feat(PoC): terrors crate usage

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -1 +1,4 @@
-target/
+target/
+scripts/__pycache__/
+.DS_Store
+.cargo/config.toml

.vscode/settings.json

@@ -1,3 +1,2 @@
 {
-    "git.enabled": false
 }

.woodpecker/server-audit.yaml

@@ -8,7 +8,7 @@ when:
       include: ['.woodpecker/server-*.yaml', 'server/**']
 
 steps:
-  - name: test
+  - name: audit
     image: jdxcode/mise:latest
     directory: server
     environment:

.woodpecker/server-lint.yaml

@@ -0,0 +1,25 @@
+when:
+  - event: pull_request
+    path:
+      include: ['.woodpecker/server-*.yaml', 'server/**']
+  - event: push
+    branch: main
+    path:
+      include: ['.woodpecker/server-*.yaml', 'server/**']
+
+steps:
+  - name: lint
+    image: jdxcode/mise:latest
+    directory: server
+    environment:
+      CARGO_TERM_COLOR: always
+      CARGO_TARGET_DIR: /usr/local/cargo/target
+      CARGO_HOME: /usr/local/cargo/registry
+    volumes:
+      - cargo-target:/usr/local/cargo/target
+      - cargo-registry:/usr/local/cargo/registry
+    commands:
+      - apt-get update && apt-get install -y pkg-config
+      - mise install rust 
+      - mise install protoc
+      - mise exec rust -- cargo clippy --all-targets --all-features -- -D warnings

.woodpecker/server-vet.yaml

@@ -8,7 +8,7 @@ when:
       include: ['.woodpecker/server-*.yaml', 'server/**']
 
 steps:
-  - name: test
+  - name: vet
     image: jdxcode/mise:latest
     directory: server
     environment:

ARCHITECTURE.md

@@ -3,7 +3,6 @@
 Arbiter is a permissioned signing service for cryptocurrency wallets. It runs as a background service on the user's machine with an optional client application for vault management.
 
 **Core principle:** The vault NEVER exposes key material. It only produces signatures when a request satisfies the configured policies.
-
 ---
 
 ## 1. Peer Types

IMPLEMENTATION.md

@@ -4,6 +4,52 @@ This document covers concrete technology choices and dependencies. For the archi
 
 ---
 
+## Client Connection Flow
+
+### New Client Approval
+
+When a client whose public key is not yet in the database connects, all connected user agents are asked to approve the connection. The first agent to respond determines the outcome; remaining requests are cancelled via a watch channel.
+
+```mermaid
+flowchart TD
+    A([Client connects]) --> B[Receive AuthChallengeRequest]
+    B --> C{pubkey in DB?}
+
+    C -- yes --> D[Read nonce\nIncrement nonce in DB]
+    D --> G
+
+    C -- no --> E[Ask all UserAgents:\nClientConnectionRequest]
+    E --> F{First response}
+    F -- denied --> Z([Reject connection])
+    F -- approved --> F2[Cancel remaining\nUserAgent requests]
+    F2 --> F3[INSERT client\nnonce = 1]
+    F3 --> G[Send AuthChallenge\nwith nonce]
+
+    G --> H[Receive AuthChallengeSolution]
+    H --> I{Signature valid?}
+    I -- no --> Z
+    I -- yes --> J([Session started])
+```
+
+### Known Issue: Concurrent Registration Race (TOCTOU)
+
+Two connections presenting the same previously-unknown public key can race through the approval flow simultaneously:
+
+1. Both check the DB → neither is registered.
+2. Both request approval from user agents → both receive approval.
+3. Both `INSERT` the client record → the second insert silently overwrites the first, resetting the nonce.
+
+This means the first connection's nonce is invalidated by the second, causing its challenge verification to fail. A fix requires either serialising new-client registration (e.g. an in-memory lock keyed on pubkey) or replacing the separate check + insert with an `INSERT OR IGNORE` / upsert guarded by a unique constraint on `public_key`.
+
+### Nonce Semantics
+
+The `program_client.nonce` column stores the **next usable nonce** — i.e. it is always one ahead of the nonce last issued in a challenge.
+
+- **New client:** inserted with `nonce = 1`; the first challenge is issued with `nonce = 0`.
+- **Existing client:** the current DB value is read and used as the challenge nonce, then immediately incremented within the same exclusive transaction, preventing replay.
+
+---
+
 ## Cryptography
 
 ### Authentication
@@ -27,6 +73,82 @@ This document covers concrete technology choices and dependencies. For the archi
 
 ---
 
+## EVM Policy Engine
+
+### Overview
+
+The EVM engine classifies incoming transactions, enforces grant constraints, and records executions. It is the sole path through which a wallet key is used for signing.
+
+The central abstraction is the `Policy` trait. Each implementation handles one semantic transaction category and owns its own database tables for grant storage and transaction logging.
+
+### Transaction Evaluation Flow
+
+`Engine::evaluate_transaction` runs the following steps in order:
+
+1. **Classify** — Each registered policy's `analyze(context)` inspects the transaction fields (`chain`, `to`, `value`, `calldata`). The first one returning `Some(meaning)` wins. If none match, the transaction is rejected as `UnsupportedTransactionType`.
+2. **Find grant** — `Policy::try_find_grant` queries for a non-revoked grant covering this wallet, client, chain, and target address.
+3. **Check shared constraints** — `check_shared_constraints` runs in the engine before any policy-specific logic. It enforces the validity window, gas fee caps, and transaction count rate limit (see below).
+4. **Evaluate** — `Policy::evaluate` checks the decoded meaning against the grant's policy-specific constraints and returns any violations.
+5. **Record** — If `RunKind::Execution` and there are no violations, the engine writes to `evm_transaction_log` and calls `Policy::record_transaction` for any policy-specific logging (e.g., token transfer volume).
+
+### Policy Trait
+
+| Method | Purpose |
+|---|---|
+| `analyze` | Pure — classifies a transaction into a typed `Meaning`, or `None` if this policy doesn't apply |
+| `evaluate` | Checks the `Meaning` against a `Grant`; returns a list of `EvalViolation`s |
+| `create_grant` | Inserts policy-specific rows; returns the specific grant ID |
+| `try_find_grant` | Finds a matching non-revoked grant for the given `EvalContext` |
+| `find_all_grants` | Returns all non-revoked grants (used for listing) |
+| `record_transaction` | Persists policy-specific data after execution |
+
+`analyze` and `evaluate` are intentionally separate: classification is pure and cheap, while evaluation may involve DB queries (e.g., fetching past transfer volume).
+
+### Registered Policies
+
+**EtherTransfer** — plain ETH transfers (empty calldata)
+
+- Grant requires: allowlist of recipient addresses + one volumetric rate limit (max ETH over a time window)
+- Violations: recipient not in allowlist, cumulative ETH volume exceeded
+
+**TokenTransfer** — ERC-20 `transfer(address,uint256)` calls
+
+- Recognised by ABI-decoding the `transfer(address,uint256)` selector against a static registry of known token contracts (`arbiter_tokens_registry`)
+- Grant requires: token contract address, optional recipient restriction, zero or more volumetric rate limits
+- Violations: recipient mismatch, any volumetric limit exceeded
+
+### Grant Model
+
+Every grant has two layers:
+
+- **Shared (`evm_basic_grant`)** — wallet, chain, validity period, gas fee caps, transaction count rate limit. One row per grant regardless of type.
+- **Specific** — policy-owned tables (`evm_ether_transfer_grant`, `evm_token_transfer_grant`, etc.) holding type-specific configuration.
+
+`find_all_grants` uses a `#[diesel::auto_type]` base join between the specific and shared tables, then batch-loads related rows (targets, volume limits) in two additional queries to avoid N+1.
+
+The engine exposes `list_all_grants` which collects across all policy types into `Vec<Grant<SpecificGrant>>` via a blanket `From<Grant<S>> for Grant<SpecificGrant>` conversion.
+
+### Shared Constraints (enforced by the engine)
+
+These are checked centrally in `check_shared_constraints` before policy evaluation:
+
+| Constraint | Fields | Behaviour |
+|---|---|---|
+| Validity window | `valid_from`, `valid_until` | Emits `InvalidTime` if current time is outside the range |
+| Gas fee cap | `max_gas_fee_per_gas`, `max_priority_fee_per_gas` | Emits `GasLimitExceeded` if either cap is breached |
+| Tx count rate limit | `rate_limit` (`count` + `window`) | Counts rows in `evm_transaction_log` within the window; emits `RateLimitExceeded` if at or above the limit |
+
+---
+
+### Known Limitations
+
+- **Only EIP-1559 transactions are supported.** Legacy and EIP-2930 types are rejected outright.
+- **No opaque-calldata (unknown contract) grant type.** The architecture describes a category for unrecognised contracts, but no policy implements it yet. Any transaction that is not a plain ETH transfer or a known ERC-20 transfer is unconditionally rejected.
+- **Token registry is static.** Tokens are recognised only if they appear in the hard-coded `arbiter_tokens_registry` crate. There is no mechanism to register additional contracts at runtime.
+- **Nonce management is not implemented.** The architecture lists nonce deduplication as a core responsibility, but no nonce tracking or enforcement exists yet.
+
+---
+
 ## Memory Protection
 
 The unsealed root key must be held in a hardened memory cell resistant to dumps, page swaps, and hibernation.

LICENSE

@@ -0,0 +1,190 @@
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README.md

@@ -0,0 +1,13 @@
+# Arbiter
+> Policy-first multi-client wallet daemon, allowing permissioned transactions across blockchains
+
+## Security warning
+Arbiter can't meaningfully protect against host compromise. Potential attack flow:
+- Attacker steals TLS keys from database
+- Pretends to be server; just accepts user agent challenge solutions
+- Pretend to be in sealed state and performing DH with client
+- Steals user password and derives seal key
+
+While this attack is highly targetive, it's still possible. 
+
+> This software is experimental. Do not use with funds you cannot afford to lose.

app/.dart_tool/extension_discovery/README.md

@@ -0,0 +1,31 @@
+Extension Discovery Cache
+=========================
+
+This folder is used by `package:extension_discovery` to cache lists of
+packages that contains extensions for other packages.
+
+DO NOT USE THIS FOLDER
+----------------------
+
+ * Do not read (or rely) the contents of this folder.
+ * Do write to this folder.
+
+If you're interested in the lists of extensions stored in this folder use the
+API offered by package `extension_discovery` to get this information.
+
+If this package doesn't work for your use-case, then don't try to read the
+contents of this folder. It may change, and will not remain stable.
+
+Use package `extension_discovery`
+---------------------------------
+
+If you want to access information from this folder.
+
+Feel free to delete this folder
+-------------------------------
+
+Files in this folder act as a cache, and the cache is discarded if the files
+are older than the modification time of `.dart_tool/package_config.json`.
+
+Hence, it should never be necessary to clear this cache manually, if you find a
+need to do please file a bug.

app/.dart_tool/extension_discovery/vs_code.json

@@ -0,0 +1 @@
+{"version":2,"entries":[{"package":"app","rootUri":"../","packageUri":"lib/"}]}

app/.dart_tool/package_config.json

@@ -0,0 +1,178 @@
+{
+  "configVersion": 2,
+  "packages": [
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+      "packageUri": "lib/",
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+    },
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+    },
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+    {
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+      "name": "lints",
+      "rootUri": "file:///Users/kaska/.pub-cache/hosted/pub.dev/lints-6.1.0",
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+    {
+      "name": "term_glyph",
+      "rootUri": "file:///Users/kaska/.pub-cache/hosted/pub.dev/term_glyph-1.2.2",
+      "packageUri": "lib/",
+      "languageVersion": "3.1"
+    },
+    {
+      "name": "test_api",
+      "rootUri": "file:///Users/kaska/.pub-cache/hosted/pub.dev/test_api-0.7.7",
+      "packageUri": "lib/",
+      "languageVersion": "3.5"
+    },
+    {
+      "name": "vector_math",
+      "rootUri": "file:///Users/kaska/.pub-cache/hosted/pub.dev/vector_math-2.2.0",
+      "packageUri": "lib/",
+      "languageVersion": "3.1"
+    },
+    {
+      "name": "vm_service",
+      "rootUri": "file:///Users/kaska/.pub-cache/hosted/pub.dev/vm_service-15.0.2",
+      "packageUri": "lib/",
+      "languageVersion": "3.5"
+    },
+    {
+      "name": "app",
+      "rootUri": "../",
+      "packageUri": "lib/",
+      "languageVersion": "3.10"
+    }
+  ],
+  "generator": "pub",
+  "generatorVersion": "3.10.8",
+  "flutterRoot": "file:///Users/kaska/.local/share/mise/installs/flutter/3.38.9-stable",
+  "flutterVersion": "3.38.9",
+  "pubCache": "file:///Users/kaska/.pub-cache"
+}

app/.dart_tool/package_graph.json

@@ -0,0 +1,230 @@
+{
+  "roots": [
+    "app"
+  ],
+  "packages": [
+    {
+      "name": "app",
+      "version": "1.0.0+1",
+      "dependencies": [
+        "cupertino_icons",
+        "flutter"
+      ],
+      "devDependencies": [
+        "flutter_lints",
+        "flutter_test"
+      ]
+    },
+    {
+      "name": "flutter_lints",
+      "version": "6.0.0",
+      "dependencies": [
+        "lints"
+      ]
+    },
+    {
+      "name": "flutter_test",
+      "version": "0.0.0",
+      "dependencies": [
+        "clock",
+        "collection",
+        "fake_async",
+        "flutter",
+        "leak_tracker_flutter_testing",
+        "matcher",
+        "meta",
+        "path",
+        "stack_trace",
+        "stream_channel",
+        "test_api",
+        "vector_math"
+      ]
+    },
+    {
+      "name": "cupertino_icons",
+      "version": "1.0.8",
+      "dependencies": []
+    },
+    {
+      "name": "flutter",
+      "version": "0.0.0",
+      "dependencies": [
+        "characters",
+        "collection",
+        "material_color_utilities",
+        "meta",
+        "sky_engine",
+        "vector_math"
+      ]
+    },
+    {
+      "name": "lints",
+      "version": "6.1.0",
+      "dependencies": []
+    },
+    {
+      "name": "stream_channel",
+      "version": "2.1.4",
+      "dependencies": [
+        "async"
+      ]
+    },
+    {
+      "name": "meta",
+      "version": "1.17.0",
+      "dependencies": []
+    },
+    {
+      "name": "collection",
+      "version": "1.19.1",
+      "dependencies": []
+    },
+    {
+      "name": "leak_tracker_flutter_testing",
+      "version": "3.0.10",
+      "dependencies": [
+        "flutter",
+        "leak_tracker",
+        "leak_tracker_testing",
+        "matcher",
+        "meta"
+      ]
+    },
+    {
+      "name": "vector_math",
+      "version": "2.2.0",
+      "dependencies": []
+    },
+    {
+      "name": "stack_trace",
+      "version": "1.12.1",
+      "dependencies": [
+        "path"
+      ]
+    },
+    {
+      "name": "clock",
+      "version": "1.1.2",
+      "dependencies": []
+    },
+    {
+      "name": "fake_async",
+      "version": "1.3.3",
+      "dependencies": [
+        "clock",
+        "collection"
+      ]
+    },
+    {
+      "name": "path",
+      "version": "1.9.1",
+      "dependencies": []
+    },
+    {
+      "name": "matcher",
+      "version": "0.12.17",
+      "dependencies": [
+        "async",
+        "meta",
+        "stack_trace",
+        "term_glyph",
+        "test_api"
+      ]
+    },
+    {
+      "name": "test_api",
+      "version": "0.7.7",
+      "dependencies": [
+        "async",
+        "boolean_selector",
+        "collection",
+        "meta",
+        "source_span",
+        "stack_trace",
+        "stream_channel",
+        "string_scanner",
+        "term_glyph"
+      ]
+    },
+    {
+      "name": "sky_engine",
+      "version": "0.0.0",
+      "dependencies": []
+    },
+    {
+      "name": "material_color_utilities",
+      "version": "0.11.1",
+      "dependencies": [
+        "collection"
+      ]
+    },
+    {
+      "name": "characters",
+      "version": "1.4.0",
+      "dependencies": []
+    },
+    {
+      "name": "async",
+      "version": "2.13.0",
+      "dependencies": [
+        "collection",
+        "meta"
+      ]
+    },
+    {
+      "name": "leak_tracker_testing",
+      "version": "3.0.2",
+      "dependencies": [
+        "leak_tracker",
+        "matcher",
+        "meta"
+      ]
+    },
+    {
+      "name": "leak_tracker",
+      "version": "11.0.2",
+      "dependencies": [
+        "clock",
+        "collection",
+        "meta",
+        "path",
+        "vm_service"
+      ]
+    },
+    {
+      "name": "term_glyph",
+      "version": "1.2.2",
+      "dependencies": []
+    },
+    {
+      "name": "string_scanner",
+      "version": "1.4.1",
+      "dependencies": [
+        "source_span"
+      ]
+    },
+    {
+      "name": "source_span",
+      "version": "1.10.2",
+      "dependencies": [
+        "collection",
+        "path",
+        "term_glyph"
+      ]
+    },
+    {
+      "name": "boolean_selector",
+      "version": "2.1.2",
+      "dependencies": [
+        "source_span",
+        "string_scanner"
+      ]
+    },
+    {
+      "name": "vm_service",
+      "version": "15.0.2",
+      "dependencies": []
+    }
+  ],
+  "configVersion": 1
+}

app/.dart_tool/version

@@ -0,0 +1 @@
+3.38.9

app/macos/Flutter/ephemeral/Flutter-Generated.xcconfig

@@ -0,0 +1,11 @@
+// This is a generated file; do not edit or check into version control.
+FLUTTER_ROOT=/Users/kaska/.local/share/mise/installs/flutter/3.38.9-stable
+FLUTTER_APPLICATION_PATH=/Users/kaska/Documents/Projects/Major/arbiter/app
+COCOAPODS_PARALLEL_CODE_SIGN=true
+FLUTTER_BUILD_DIR=build
+FLUTTER_BUILD_NAME=1.0.0
+FLUTTER_BUILD_NUMBER=1
+DART_OBFUSCATION=false
+TRACK_WIDGET_CREATION=true
+TREE_SHAKE_ICONS=false
+PACKAGE_CONFIG=.dart_tool/package_config.json

app/macos/Flutter/ephemeral/flutter_export_environment.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+# This is a generated file; do not edit or check into version control.
+export "FLUTTER_ROOT=/Users/kaska/.local/share/mise/installs/flutter/3.38.9-stable"
+export "FLUTTER_APPLICATION_PATH=/Users/kaska/Documents/Projects/Major/arbiter/app"
+export "COCOAPODS_PARALLEL_CODE_SIGN=true"
+export "FLUTTER_BUILD_DIR=build"
+export "FLUTTER_BUILD_NAME=1.0.0"
+export "FLUTTER_BUILD_NUMBER=1"
+export "DART_OBFUSCATION=false"
+export "TRACK_WIDGET_CREATION=true"
+export "TREE_SHAKE_ICONS=false"
+export "PACKAGE_CONFIG=.dart_tool/package_config.json"

app/pubspec.yaml

@@ -1,89 +0,0 @@
-name: app
-description: "A new Flutter project."
-# The following line prevents the package from being accidentally published to
-# pub.dev using `flutter pub publish`. This is preferred for private packages.
-publish_to: 'none' # Remove this line if you wish to publish to pub.dev
-
-# The following defines the version and build number for your application.
-# A version number is three numbers separated by dots, like 1.2.43
-# followed by an optional build number separated by a +.
-# Both the version and the builder number may be overridden in flutter
-# build by specifying --build-name and --build-number, respectively.
-# In Android, build-name is used as versionName while build-number used as versionCode.
-# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
-# In iOS, build-name is used as CFBundleShortVersionString while build-number is used as CFBundleVersion.
-# Read more about iOS versioning at
-# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
-# In Windows, build-name is used as the major, minor, and patch parts
-# of the product and file versions while build-number is used as the build suffix.
-version: 1.0.0+1
-
-environment:
-  sdk: ^3.10.8
-
-# Dependencies specify other packages that your package needs in order to work.
-# To automatically upgrade your package dependencies to the latest versions
-# consider running `flutter pub upgrade --major-versions`. Alternatively,
-# dependencies can be manually updated by changing the version numbers below to
-# the latest version available on pub.dev. To see which dependencies have newer
-# versions available, run `flutter pub outdated`.
-dependencies:
-  flutter:
-    sdk: flutter
-
-  # The following adds the Cupertino Icons font to your application.
-  # Use with the CupertinoIcons class for iOS style icons.
-  cupertino_icons: ^1.0.8
-
-dev_dependencies:
-  flutter_test:
-    sdk: flutter
-
-  # The "flutter_lints" package below contains a set of recommended lints to
-  # encourage good coding practices. The lint set provided by the package is
-  # activated in the `analysis_options.yaml` file located at the root of your
-  # package. See that file for information about deactivating specific lint
-  # rules and activating additional ones.
-  flutter_lints: ^6.0.0
-
-# For information on the generic Dart part of this file, see the
-# following page: https://dart.dev/tools/pub/pubspec
-
-# The following section is specific to Flutter packages.
-flutter:
-
-  # The following line ensures that the Material Icons font is
-  # included with your application, so that you can use the icons in
-  # the material Icons class.
-  uses-material-design: true
-
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
-
-  # An image asset can refer to one or more resolution-specific "variants", see
-  # https://flutter.dev/to/resolution-aware-images
-
-  # For details regarding adding assets from package dependencies, see
-  # https://flutter.dev/to/asset-from-package
-
-  # To add custom fonts to your application, add a fonts section here,
-  # in this "flutter" section. Each entry in this list should have a
-  # "family" key with the font family name, and a "fonts" key with a
-  # list giving the asset and other descriptors for the font. For
-  # example:
-  # fonts:
-  #   - family: Schyler
-  #     fonts:
-  #       - asset: fonts/Schyler-Regular.ttf
-  #       - asset: fonts/Schyler-Italic.ttf
-  #         style: italic
-  #   - family: Trajan Pro
-  #     fonts:
-  #       - asset: fonts/TrajanPro.ttf
-  #       - asset: fonts/TrajanPro_Bold.ttf
-  #         weight: 700
-  #
-  # For details regarding fonts from package dependencies,
-  # see https://flutter.dev/to/font-from-package

mise.lock

@@ -10,6 +10,10 @@ backend = "cargo:cargo-features"
 version = "0.11.1"
 backend = "cargo:cargo-features-manager"
 
+[[tools."cargo:cargo-insta"]]
+version = "1.46.3"
+backend = "cargo:cargo-insta"
+
 [[tools."cargo:cargo-nextest"]]
 version = "0.9.126"
 backend = "cargo:cargo-nextest"
@@ -51,6 +55,15 @@ backend = "aqua:protocolbuffers/protobuf/protoc"
 "platforms.macos-x64" = { checksum = "sha256:312f04713946921cc0187ef34df80241ddca1bab6f564c636885fd2cc90d3f88", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-osx-x86_64.zip"}
 "platforms.windows-x64" = { checksum = "sha256:1ebd7c87baffb9f1c47169b640872bf5fb1e4408079c691af527be9561d8f6f7", url = "https://github.com/protocolbuffers/protobuf/releases/download/v29.6/protoc-29.6-win64.zip"}
 
+[[tools.python]]
+version = "3.14.3"
+backend = "core:python"
+"platforms.linux-arm64" = { checksum = "sha256:be0f4dc2932f762292b27d46ea7d3e8e66ddf3969a5eb0254a229015ed402625", url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260303/cpython-3.14.3+20260303-aarch64-unknown-linux-gnu-install_only_stripped.tar.gz"}
+"platforms.linux-x64" = { checksum = "sha256:0a73413f89efd417871876c9accaab28a9d1e3cd6358fbfff171a38ec99302f0", url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260303/cpython-3.14.3+20260303-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz"}
+"platforms.macos-arm64" = { checksum = "sha256:4703cdf18b26798fde7b49b6b66149674c25f97127be6a10dbcf29309bdcdcdb", url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260303/cpython-3.14.3+20260303-aarch64-apple-darwin-install_only_stripped.tar.gz"}
+"platforms.macos-x64" = { checksum = "sha256:76f1cc26e3d262eae8ca546a93e8bded10cf0323613f7e246fea2e10a8115eb7", url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260303/cpython-3.14.3+20260303-x86_64-apple-darwin-install_only_stripped.tar.gz"}
+"platforms.windows-x64" = { checksum = "sha256:950c5f21a015c1bdd1337f233456df2470fab71e4d794407d27a84cb8b9909a0", url = "https://github.com/astral-sh/python-build-standalone/releases/download/20260303/cpython-3.14.3+20260303-x86_64-pc-windows-msvc-install_only_stripped.tar.gz"}
+
 [[tools.rust]]
 version = "1.93.0"
 backend = "core:rust"

mise.toml

@@ -2,10 +2,11 @@
 "cargo:diesel_cli" = { version = "2.3.6", features = "sqlite,sqlite-bundled", default-features = false }
 "cargo:cargo-audit" = "0.22.1"
 "cargo:cargo-vet" = "0.10.2"
-
 flutter = "3.38.9-stable"
 protoc = "29.6"
-rust = "1.93.0"
+"rust" = {version = "1.93.0", components = "clippy"}
 "cargo:cargo-features-manager" = "0.11.1"
 "cargo:cargo-nextest" = "0.9.126"
 "cargo:cargo-shear" = "latest"
+"cargo:cargo-insta" = "1.46.3"
+python = "3.14.3"

protobufs/arbiter.proto

@@ -2,30 +2,8 @@ syntax = "proto3";
 
 package arbiter;
 
-import "auth.proto";
-
-message ClientRequest {
-  oneof payload {
-    arbiter.auth.ClientMessage auth_message = 1;
-  }
-}
-
-message ClientResponse {
-  oneof payload {
-    arbiter.auth.ServerMessage auth_message = 1;
-  }
-}
-
-message UserAgentRequest {
-  oneof payload {
-    arbiter.auth.ClientMessage auth_message = 1;
-  }
-}
-message UserAgentResponse {
-  oneof payload {
-    arbiter.auth.ServerMessage auth_message = 1;
-  }
-}
+import "client.proto";
+import "user_agent.proto";
 
 message ServerInfo {
   string version = 1;
@@ -33,6 +11,6 @@ message ServerInfo {
 }
 
 service ArbiterService {
-  rpc Client(stream ClientRequest) returns (stream ClientResponse);
-  rpc UserAgent(stream UserAgentRequest) returns (stream UserAgentResponse);
+  rpc Client(stream arbiter.client.ClientRequest) returns (stream arbiter.client.ClientResponse);
+  rpc UserAgent(stream arbiter.user_agent.UserAgentRequest) returns (stream arbiter.user_agent.UserAgentResponse);
 }

protobufs/auth.proto

@@ -1,35 +0,0 @@
-syntax = "proto3";
-
-package arbiter.auth;
-
-import "google/protobuf/timestamp.proto";
-
-message AuthChallengeRequest {
-  bytes pubkey = 1;
-  optional string bootstrap_token = 2;
-}
-
-message AuthChallenge {
-  bytes pubkey = 1;
-  int32 nonce = 2;
-}
-
-message AuthChallengeSolution {
-  bytes signature = 1;
-}
-
-message AuthOk {}
-
-message ClientMessage {
-  oneof payload {
-    AuthChallengeRequest auth_challenge_request = 1;
-    AuthChallengeSolution auth_challenge_solution = 2;
-  }
-}
-
-message ServerMessage {
-  oneof payload {
-    AuthChallenge auth_challenge = 1;
-    AuthOk auth_ok = 2;
-  }
-}

protobufs/client.proto

@@ -0,0 +1,47 @@
+syntax = "proto3";
+
+package arbiter.client;
+
+import "evm.proto";
+
+message AuthChallengeRequest {
+  bytes pubkey = 1;
+}
+
+message AuthChallenge {
+  bytes pubkey = 1;
+  int32 nonce = 2;
+}
+
+message AuthChallengeSolution {
+  bytes signature = 1;
+}
+
+message AuthOk {}
+
+message ClientRequest {
+  oneof payload {
+    AuthChallengeRequest auth_challenge_request = 1;
+    AuthChallengeSolution auth_challenge_solution = 2;
+    arbiter.evm.EvmSignTransactionRequest evm_sign_transaction = 3;
+  }
+}
+
+message ClientConnectError {
+  enum Code {
+    UNKNOWN = 0;
+    APPROVAL_DENIED = 1;
+    NO_USER_AGENTS_ONLINE = 2;
+  }
+  Code code = 1;
+}
+
+message ClientResponse {
+  oneof payload {
+    AuthChallenge auth_challenge = 1;
+    AuthOk auth_ok = 2;
+    ClientConnectError client_connect_error = 5;
+    arbiter.evm.EvmSignTransactionResponse evm_sign_transaction = 3;
+    arbiter.evm.EvmAnalyzeTransactionResponse evm_analyze_transaction = 4;
+  }
+}

protobufs/evm.proto

@@ -0,0 +1,216 @@
+syntax = "proto3";
+
+package arbiter.evm;
+
+import "google/protobuf/empty.proto";
+import "google/protobuf/timestamp.proto";
+
+enum EvmError {
+  EVM_ERROR_UNSPECIFIED = 0;
+  EVM_ERROR_VAULT_SEALED = 1;
+  EVM_ERROR_INTERNAL = 2;
+}
+
+message WalletEntry {
+  bytes address = 1; // 20-byte Ethereum address
+}
+
+message WalletList {
+  repeated WalletEntry wallets = 1;
+}
+
+message WalletCreateResponse {
+  oneof result {
+    WalletEntry wallet = 1;
+    EvmError error = 2;
+  }
+}
+
+message WalletListResponse {
+  oneof result {
+    WalletList wallets = 1;
+    EvmError error = 2;
+  }
+}
+
+// --- Grant types ---
+
+message TransactionRateLimit {
+  uint32 count = 1;
+  int64 window_secs = 2;
+}
+
+message VolumeRateLimit {
+  bytes max_volume = 1; // U256 as big-endian bytes
+  int64 window_secs = 2;
+}
+
+message SharedSettings {
+  int32 wallet_id = 1;
+  uint64 chain_id = 2;
+  optional google.protobuf.Timestamp valid_from = 3;
+  optional google.protobuf.Timestamp valid_until = 4;
+  optional bytes max_gas_fee_per_gas = 5; // U256 as big-endian bytes
+  optional bytes max_priority_fee_per_gas = 6; // U256 as big-endian bytes
+  optional TransactionRateLimit rate_limit = 7;
+}
+
+message EtherTransferSettings {
+  repeated bytes targets = 1; // list of 20-byte Ethereum addresses
+  VolumeRateLimit limit = 2;
+}
+
+message TokenTransferSettings {
+  bytes token_contract = 1; // 20-byte Ethereum address
+  optional bytes target = 2; // 20-byte Ethereum address; absent means any recipient allowed
+  repeated VolumeRateLimit volume_limits = 3;
+}
+
+message SpecificGrant {
+  oneof grant {
+    EtherTransferSettings ether_transfer = 1;
+    TokenTransferSettings token_transfer = 2;
+  }
+}
+
+message EtherTransferMeaning {
+  bytes to = 1; // 20-byte Ethereum address
+  bytes value = 2; // U256 as big-endian bytes
+}
+
+message TokenInfo {
+  string symbol = 1;
+  bytes address = 2; // 20-byte Ethereum address
+  uint64 chain_id = 3;
+}
+
+// Mirror of token_transfers::Meaning
+message TokenTransferMeaning {
+  TokenInfo token = 1;
+  bytes to = 2; // 20-byte Ethereum address
+  bytes value = 3; // U256 as big-endian bytes
+}
+
+// Mirror of policies::SpecificMeaning
+message SpecificMeaning {
+  oneof meaning {
+    EtherTransferMeaning ether_transfer = 1;
+    TokenTransferMeaning token_transfer = 2;
+  }
+}
+
+// --- Eval error types ---
+message GasLimitExceededViolation {
+  optional bytes max_gas_fee_per_gas = 1; // U256 as big-endian bytes
+  optional bytes max_priority_fee_per_gas = 2; // U256 as big-endian bytes
+}
+
+message EvalViolation {
+  oneof kind {
+    bytes invalid_target = 1; // 20-byte Ethereum address
+    GasLimitExceededViolation gas_limit_exceeded = 2;
+    google.protobuf.Empty rate_limit_exceeded = 3;
+    google.protobuf.Empty volumetric_limit_exceeded = 4;
+    google.protobuf.Empty invalid_time = 5;
+    google.protobuf.Empty invalid_transaction_type = 6;
+  }
+}
+
+// Transaction was classified but no grant covers it
+message NoMatchingGrantError {
+  SpecificMeaning meaning = 1;
+}
+
+// Transaction was classified and a grant was found, but constraints were violated
+message PolicyViolationsError {
+  SpecificMeaning meaning = 1;
+  repeated EvalViolation violations = 2;
+}
+
+// top-level error returned when transaction evaluation fails
+message TransactionEvalError {
+  oneof kind {
+    google.protobuf.Empty contract_creation_not_supported = 1;
+    google.protobuf.Empty unsupported_transaction_type = 2;
+    NoMatchingGrantError no_matching_grant = 3;
+    PolicyViolationsError policy_violations = 4;
+  }
+}
+
+// --- UserAgent grant management ---
+message EvmGrantCreateRequest {
+  int32 client_id = 1;
+  SharedSettings shared = 2;
+  SpecificGrant specific = 3;
+}
+
+message EvmGrantCreateResponse {
+  oneof result {
+    int32 grant_id = 1;
+    EvmError error = 2;
+  }
+}
+
+message EvmGrantDeleteRequest {
+  int32 grant_id = 1;
+}
+
+message EvmGrantDeleteResponse {
+  oneof result {
+    google.protobuf.Empty ok = 1;
+    EvmError error = 2;
+  }
+}
+
+// Basic grant info returned in grant listings
+message GrantEntry {
+  int32 id = 1;
+  int32 client_id = 2;
+  SharedSettings shared = 3;
+  SpecificGrant specific = 4;
+}
+
+message EvmGrantListRequest {
+  optional int32 wallet_id = 1;
+}
+
+message EvmGrantListResponse {
+  oneof result {
+    EvmGrantList grants = 1;
+    EvmError error = 2;
+  }
+}
+
+message EvmGrantList {
+  repeated GrantEntry grants = 1;
+}
+
+// --- Client transaction operations ---
+
+message EvmSignTransactionRequest {
+  bytes wallet_address = 1; // 20-byte Ethereum address
+  bytes rlp_transaction = 2; // RLP-encoded EIP-1559 transaction (unsigned)
+}
+
+// oneof because signing and evaluation happen atomically — a signing failure
+// is always either an eval error or an internal error, never a partial success
+message EvmSignTransactionResponse {
+  oneof result {
+    bytes signature = 1; // 65-byte signature: r[32] || s[32] || v[1]
+    TransactionEvalError eval_error = 2;
+    EvmError error = 3;
+  }
+}
+
+message EvmAnalyzeTransactionRequest {
+  bytes wallet_address = 1; // 20-byte Ethereum address
+  bytes rlp_transaction = 2; // RLP-encoded EIP-1559 transaction
+}
+
+message EvmAnalyzeTransactionResponse {
+  oneof result {
+    SpecificMeaning meaning = 1;
+    TransactionEvalError eval_error = 2;
+    EvmError error = 3;
+  }
+}

protobufs/unseal.proto

@@ -1,14 +0,0 @@
-syntax = "proto3";
-
-package arbiter.unseal;
-
-message UserAgentKeyRequest {}
-
-message ServerKeyResponse {
-  bytes pubkey = 1;
-}
-message UserAgentSealedKey {
-  bytes sealed_key = 1;
-  bytes pubkey = 2;
-  bytes nonce = 3;
-}

protobufs/user_agent.proto

@@ -0,0 +1,144 @@
+syntax = "proto3";
+
+package arbiter.user_agent;
+
+import "google/protobuf/empty.proto";
+import "evm.proto";
+
+enum KeyType {
+  KEY_TYPE_UNSPECIFIED = 0;
+  KEY_TYPE_ED25519 = 1;
+  KEY_TYPE_ECDSA_SECP256K1 = 2;
+  KEY_TYPE_RSA = 3;
+}
+
+// --- SDK client management ---
+
+enum SdkClientError {
+  SDK_CLIENT_ERROR_UNSPECIFIED = 0;
+  SDK_CLIENT_ERROR_ALREADY_EXISTS = 1;
+  SDK_CLIENT_ERROR_NOT_FOUND = 2;
+  SDK_CLIENT_ERROR_HAS_RELATED_DATA = 3; // hard-delete blocked by FK (client has grants or transaction logs)
+  SDK_CLIENT_ERROR_INTERNAL = 4;
+}
+
+message SdkClientApproveRequest {
+  bytes pubkey = 1; // 32-byte ed25519 public key
+}
+
+message SdkClientRevokeRequest {
+  int32 client_id = 1;
+}
+
+message SdkClientEntry {
+  int32 id = 1;
+  bytes pubkey = 2;
+  int32 created_at = 3;
+}
+
+message SdkClientList {
+  repeated SdkClientEntry clients = 1;
+}
+
+message SdkClientApproveResponse {
+  oneof result {
+    SdkClientEntry client = 1;
+    SdkClientError error = 2;
+  }
+}
+
+message SdkClientRevokeResponse {
+  oneof result {
+    google.protobuf.Empty ok = 1;
+    SdkClientError error = 2;
+  }
+}
+
+message SdkClientListResponse {
+  oneof result {
+    SdkClientList clients = 1;
+    SdkClientError error = 2;
+  }
+}
+
+message AuthChallengeRequest {
+  bytes pubkey = 1;
+  optional string bootstrap_token = 2;
+  KeyType key_type = 3;
+}
+
+message AuthChallenge {
+  bytes pubkey = 1;
+  int32 nonce = 2;
+}
+
+message AuthChallengeSolution {
+  bytes signature = 1;
+}
+
+message AuthOk {}
+
+message UnsealStart {
+  bytes client_pubkey = 1;
+}
+
+message UnsealStartResponse {
+  bytes server_pubkey = 1;
+}
+message UnsealEncryptedKey {
+  bytes nonce = 1;
+  bytes ciphertext = 2;
+  bytes associated_data = 3;
+}
+
+enum UnsealResult {
+  UNSEAL_RESULT_UNSPECIFIED = 0;
+  UNSEAL_RESULT_SUCCESS = 1;
+  UNSEAL_RESULT_INVALID_KEY = 2;
+  UNSEAL_RESULT_UNBOOTSTRAPPED = 3;
+}
+
+enum VaultState {
+  VAULT_STATE_UNSPECIFIED = 0;
+  VAULT_STATE_UNBOOTSTRAPPED = 1;
+  VAULT_STATE_SEALED = 2;
+  VAULT_STATE_UNSEALED = 3;
+  VAULT_STATE_ERROR = 4;
+}
+
+message UserAgentRequest {
+  oneof payload {
+    AuthChallengeRequest auth_challenge_request = 1;
+    AuthChallengeSolution auth_challenge_solution = 2;
+    UnsealStart unseal_start = 3;
+    UnsealEncryptedKey unseal_encrypted_key = 4;
+    google.protobuf.Empty query_vault_state = 5;
+    google.protobuf.Empty evm_wallet_create = 6;
+    google.protobuf.Empty evm_wallet_list = 7;
+    arbiter.evm.EvmGrantCreateRequest evm_grant_create = 8;
+    arbiter.evm.EvmGrantDeleteRequest evm_grant_delete = 9;
+    arbiter.evm.EvmGrantListRequest evm_grant_list = 10;
+    // field 11 reserved: was client_connection_response (online approval removed)
+    SdkClientApproveRequest sdk_client_approve = 12;
+    SdkClientRevokeRequest sdk_client_revoke = 13;
+    google.protobuf.Empty sdk_client_list = 14;
+  }
+}
+message UserAgentResponse {
+  oneof payload {
+    AuthChallenge auth_challenge = 1;
+    AuthOk auth_ok = 2;
+    UnsealStartResponse unseal_start_response = 3;
+    UnsealResult unseal_result = 4;
+    VaultState vault_state = 5;
+    arbiter.evm.WalletCreateResponse evm_wallet_create = 6;
+    arbiter.evm.WalletListResponse evm_wallet_list = 7;
+    arbiter.evm.EvmGrantCreateResponse evm_grant_create = 8;
+    arbiter.evm.EvmGrantDeleteResponse evm_grant_delete = 9;
+    arbiter.evm.EvmGrantListResponse evm_grant_list = 10;
+    // fields 11, 12 reserved: were client_connection_request, client_connection_cancel (online approval removed)
+    SdkClientApproveResponse sdk_client_approve = 13;
+    SdkClientRevokeResponse sdk_client_revoke = 14;
+    SdkClientListResponse sdk_client_list = 15;
+  }
+}

scripts/gen_erc20_registry.py

@@ -0,0 +1,150 @@
+#!/usr/bin/env python3
+"""
+Fetch the Uniswap default token list and emit Rust `TokenInfo` statics.
+
+Usage:
+    python3 gen_erc20_registry.py                       # fetch from IPFS
+    python3 gen_erc20_registry.py tokens.json           # local file
+    python3 gen_erc20_registry.py tokens.json out.rs    # custom output file
+"""
+
+import json
+import re
+import sys
+import unicodedata
+import urllib.request
+
+UNISWAP_URL = "https://ipfs.io/ipns/tokens.uniswap.org"
+
+SOLANA_CHAIN_ID = 501000101
+IDENTIFIER_RE = re.compile(r"[^A-Za-z0-9]+")
+
+
+def load_tokens(source=None):
+    if source:
+        with open(source) as f:
+            return json.load(f)
+    req = urllib.request.Request(
+        UNISWAP_URL,
+        headers={"Accept": "application/json", "User-Agent": "gen_tokens/1.0"},
+    )
+    with urllib.request.urlopen(req, timeout=60) as resp:
+        return json.loads(resp.read())
+
+
+def escape(s: str) -> str:
+    return s.replace("\\", "\\\\").replace('"', '\\"')
+
+
+def to_screaming_case(name: str) -> str:
+    normalized = unicodedata.normalize("NFKD", name or "")
+    ascii_name = normalized.encode("ascii", "ignore").decode("ascii")
+    snake = IDENTIFIER_RE.sub("_", ascii_name).strip("_").upper()
+    if not snake:
+        snake = "TOKEN"
+    if snake[0].isdigit():
+        snake = f"TOKEN_{snake}"
+    return snake
+
+
+def static_name_for_token(token: dict, used_names: set[str]) -> str:
+    base = to_screaming_case(token.get("name", ""))
+    if base not in used_names:
+        used_names.add(base)
+        return base
+
+    address = token["address"]
+    suffix = f"{token['chainId']}_{address[2:].upper()[-8:]}"
+    candidate = f"{base}_{suffix}"
+
+    i = 2
+    while candidate in used_names:
+        candidate = f"{base}_{suffix}_{i}"
+        i += 1
+
+    used_names.add(candidate)
+    return candidate
+
+
+def main():
+    source = sys.argv[1] if len(sys.argv) > 1 else None
+    output = sys.argv[2] if len(sys.argv) > 2 else "generated_tokens.rs"
+    data = load_tokens(source)
+    tokens = data["tokens"]
+
+    # Deduplicate by (chainId, address)
+    seen = set()
+    unique = []
+    for t in tokens:
+        key = (t["chainId"], t["address"].lower())
+        if key not in seen:
+            seen.add(key)
+            unique.append(t)
+
+    unique.sort(key=lambda t: (t["chainId"], t.get("symbol", "").upper()))
+    evm_tokens = [t for t in unique if t["chainId"] != SOLANA_CHAIN_ID]
+
+    ver = data["version"]
+    lines = []
+    w = lines.append
+
+    w(
+        f"// Auto-generated from Uniswap token list v{ver['major']}.{ver['minor']}.{ver['patch']}"
+    )
+    w(f"// {len(evm_tokens)} tokens")
+    w("// DO NOT EDIT - regenerate with gen_erc20_registry.py")
+    w("")
+
+    used_static_names = set()
+    token_statics = []
+    for t in evm_tokens:
+        static_name = static_name_for_token(t, used_static_names)
+        token_statics.append((static_name, t))
+
+    for static_name, t in token_statics:
+        addr = t["address"]
+        name = escape(t.get("name", ""))
+        symbol = escape(t.get("symbol", ""))
+        decimals = t.get("decimals", 18)
+        logo = t.get("logoURI")
+        chain = t["chainId"]
+
+        logo_val = f'Some("{escape(logo)}")' if logo else "None"
+
+        w(f"pub static {static_name}: TokenInfo = TokenInfo {{")
+        w(f'    name: "{name}",')
+        w(f'    symbol: "{symbol}",')
+        w(f"    decimals: {decimals},")
+        w(f'    contract: address!("{addr}"),')
+        w(f"    chain: {chain},")
+        w(f"    logo_uri: {logo_val},")
+        w("};")
+        w("")
+
+    w("pub static TOKENS: &[&TokenInfo] = &[")
+    for static_name, _ in token_statics:
+        w(f"    &{static_name},")
+    w("];")
+    w("")
+    w("pub fn get_token(")
+    w("    chain_id: alloy::primitives::ChainId,")
+    w("    address: alloy::primitives::Address,")
+    w(") -> Option<&'static TokenInfo> {")
+    w("    match (chain_id, address) {")
+    for static_name, t in token_statics:
+        w(
+            f'        ({t["chainId"]}, addr) if addr == address!("{t["address"]}") => Some(&{static_name}),'
+        )
+    w("        _ => None,")
+    w("    }")
+    w("}")
+    w("")
+
+    with open(output, "w") as f:
+        f.write("\n".join(lines))
+
+    print(f"Wrote {len(token_statics)} tokens to {output}")
+
+
+if __name__ == "__main__":
+    main()

server/.cargo/audit.toml

@@ -0,0 +1,13 @@
+[advisories]
+# RUSTSEC-2023-0071: Marvin Attack timing side-channel in rsa crate.
+# No fixed version is available upstream.
+# RSA support is required for Windows Hello / KeyCredentialManager
+# (https://learn.microsoft.com/en-us/uwp/api/windows.security.credentials.keycredentialmanager.requestcreateasync),
+# which only issues RSA-2048 keys.
+# Mitigations in place:
+#   - Signing uses BlindedSigningKey (PSS+SHA-256), which applies blinding to
+#     protect the private key from timing recovery during signing.
+#   - RSA decryption is never performed; we only verify public-key signatures.
+#   - The attack requires local, high-resolution timing access against the
+#     signing process, which is not exposed in our threat model.
+ignore = ["RUSTSEC-2023-0071"]

server/Cargo.toml

@@ -1,15 +1,20 @@
 [workspace]
 members = [
-    "crates/arbiter-client",
-    "crates/arbiter-proto",
-    "crates/arbiter-server",
-    "crates/arbiter-useragent",
+    "crates/*",
 ]
 resolver = "3"
 
+[workspace.lints.clippy]
+disallowed-methods = "deny"
+
 
 [workspace.dependencies]
-tonic = { version = "0.14.3", features = ["deflate", "gzip", "tls-connect-info", "zstd"] }
+tonic = { version = "0.14.3", features = [
+    "deflate",
+    "gzip",
+    "tls-connect-info",
+    "zstd",
+] }
 tracing = "0.1.44"
 tokio = { version = "1.49.0", features = ["full"] }
 ed25519-dalek = { version = "3.0.0-pre.6", features = ["rand_core"] }
@@ -24,3 +29,17 @@ futures = "0.3.31"
 tokio-stream = { version = "0.1.18", features = ["full"] }
 kameo = "0.19.2"
 prost-types = { version = "0.14.3", features = ["chrono"] }
+x25519-dalek = { version = "2.0.1", features = ["getrandom"] }
+rstest = "0.26.1"
+rustls-pki-types = "1.14.0"
+alloy = "1.7.3"
+rcgen = { version = "0.14.7", features = [
+    "aws_lc_rs",
+    "pem",
+    "x509-parser",
+    "zeroize",
+], default-features = false }
+k256 = { version = "0.13.4", features = ["ecdsa", "pkcs8"] }
+rsa = { version = "0.9", features = ["sha2"] }
+sha2 = "0.10"
+spki = "0.7"

server/clippy.toml

@@ -0,0 +1,9 @@
+disallowed-methods = [
+    # RSA decryption is forbidden: the rsa crate has RUSTSEC-2023-0071 (Marvin Attack).
+    # We only use RSA for Windows Hello (KeyCredentialManager) public-key verification — decryption
+    # is never required and must not be introduced.
+    { path = "rsa::RsaPrivateKey::decrypt", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). Only PSS signing/verification is permitted." },
+    { path = "rsa::RsaPrivateKey::decrypt_blinded", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). Only PSS signing/verification is permitted." },
+    { path = "rsa::traits::Decryptor::decrypt", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). This blocks decrypt() on rsa::{pkcs1v15,oaep}::DecryptingKey." },
+    { path = "rsa::traits::RandomizedDecryptor::decrypt_with_rng", reason = "RSA decryption is forbidden (RUSTSEC-2023-0071 Marvin Attack). This blocks decrypt_with_rng() on rsa::{pkcs1v15,oaep}::DecryptingKey." },
+]

server/crates/arbiter-client/Cargo.toml

@@ -3,5 +3,20 @@ name = "arbiter-client"
 version = "0.1.0"
 edition = "2024"
 repository = "https://git.markettakers.org/MarketTakers/arbiter"
+license = "Apache-2.0"
+
+[lints]
+workspace = true
 
 [dependencies]
+arbiter-proto.path = "../arbiter-proto"
+alloy.workspace = true
+tonic.workspace = true
+tonic.features = ["tls-aws-lc"]
+tokio.workspace = true
+tokio-stream.workspace = true
+ed25519-dalek.workspace = true
+thiserror.workspace = true
+http = "1.4.0"
+rustls-webpki = { version = "0.103.9", features = ["aws-lc-rs"] }
+async-trait.workspace = true

server/crates/arbiter-client/src/lib.rs

@@ -1,14 +1,272 @@
-pub fn add(left: u64, right: u64) -> u64 {
-    left + right
+use alloy::{
+    consensus::SignableTransaction,
+    network::TxSigner,
+    primitives::{Address, B256, ChainId, Signature},
+    signers::{Error, Result, Signer},
+};
+use arbiter_proto::{
+    format_challenge,
+    proto::{
+        arbiter_service_client::ArbiterServiceClient,
+        client::{
+            AuthChallengeRequest, AuthChallengeSolution, ClientRequest, ClientResponse,
+            client_connect_error, client_request::Payload as ClientRequestPayload,
+            client_response::Payload as ClientResponsePayload,
+        },
+        evm::{
+            EvmSignTransactionRequest, evm_sign_transaction_response::Result as SignResponseResult,
+        },
+    },
+    url::ArbiterUrl,
+};
+use async_trait::async_trait;
+use ed25519_dalek::Signer as _;
+use tokio::sync::{Mutex, mpsc};
+use tokio_stream::wrappers::ReceiverStream;
+use tonic::transport::ClientTlsConfig;
+
+#[derive(Debug, thiserror::Error)]
+pub enum ConnectError {
+    #[error("Could not establish connection")]
+    Connection(#[from] tonic::transport::Error),
+
+    #[error("Invalid server URI")]
+    InvalidUri(#[from] http::uri::InvalidUri),
+
+    #[error("Invalid CA certificate")]
+    InvalidCaCert(#[from] webpki::Error),
+
+    #[error("gRPC error")]
+    Grpc(#[from] tonic::Status),
+
+    #[error("Auth challenge was not returned by server")]
+    MissingAuthChallenge,
+
+    #[error("Client approval denied by User Agent")]
+    ApprovalDenied,
+
+    #[error("No User Agents online to approve client")]
+    NoUserAgentsOnline,
+
+    #[error("Unexpected auth response payload")]
+    UnexpectedAuthResponse,
 }
 
-#[cfg(test)]
-mod tests {
-    use super::*;
+#[derive(Debug, thiserror::Error)]
+enum ClientSignError {
+    #[error("Transport channel closed")]
+    ChannelClosed,
 
-    #[test]
-    fn it_works() {
-        let result = add(2, 2);
-        assert_eq!(result, 4);
+    #[error("Connection closed by server")]
+    ConnectionClosed,
+
+    #[error("Invalid response payload")]
+    InvalidResponse,
+
+    #[error("Remote signing was rejected")]
+    Rejected,
+}
+
+struct ClientTransport {
+    sender: mpsc::Sender<ClientRequest>,
+    receiver: tonic::Streaming<ClientResponse>,
+}
+
+impl ClientTransport {
+    async fn send(&mut self, request: ClientRequest) -> std::result::Result<(), ClientSignError> {
+        self.sender
+            .send(request)
+            .await
+            .map_err(|_| ClientSignError::ChannelClosed)
+    }
+
+    async fn recv(&mut self) -> std::result::Result<ClientResponse, ClientSignError> {
+        match self.receiver.message().await {
+            Ok(Some(resp)) => Ok(resp),
+            Ok(None) => Err(ClientSignError::ConnectionClosed),
+            Err(_) => Err(ClientSignError::ConnectionClosed),
+        }
+    }
+}
+
+pub struct ArbiterSigner {
+    transport: Mutex<ClientTransport>,
+    address: Address,
+    chain_id: Option<ChainId>,
+}
+
+impl ArbiterSigner {
+    pub async fn connect_grpc(
+        url: ArbiterUrl,
+        key: ed25519_dalek::SigningKey,
+        address: Address,
+    ) -> std::result::Result<Self, ConnectError> {
+        let anchor = webpki::anchor_from_trusted_cert(&url.ca_cert)?.to_owned();
+        let tls = ClientTlsConfig::new().trust_anchor(anchor);
+
+        // NOTE: We intentionally keep the same URL construction strategy as the user-agent crate
+        // to avoid behavior drift between the two clients.
+        let channel = tonic::transport::Channel::from_shared(format!("{}:{}", url.host, url.port))?
+            .tls_config(tls)?
+            .connect()
+            .await?;
+
+        let mut client = ArbiterServiceClient::new(channel);
+        let (tx, rx) = mpsc::channel(16);
+        let response_stream = client.client(ReceiverStream::new(rx)).await?.into_inner();
+
+        let mut transport = ClientTransport {
+            sender: tx,
+            receiver: response_stream,
+        };
+
+        authenticate(&mut transport, key).await?;
+
+        Ok(Self {
+            transport: Mutex::new(transport),
+            address,
+            chain_id: None,
+        })
+    }
+
+    async fn sign_transaction_via_arbiter(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        if let Some(chain_id) = self.chain_id
+            && !tx.set_chain_id_checked(chain_id)
+        {
+            return Err(Error::TransactionChainIdMismatch {
+                signer: chain_id,
+                tx: tx.chain_id().unwrap(),
+            });
+        }
+
+        let mut rlp_transaction = Vec::new();
+        tx.encode_for_signing(&mut rlp_transaction);
+
+        let request = ClientRequest {
+            payload: Some(ClientRequestPayload::EvmSignTransaction(
+                EvmSignTransactionRequest {
+                    wallet_address: self.address.as_slice().to_vec(),
+                    rlp_transaction,
+                },
+            )),
+        };
+
+        let mut transport = self.transport.lock().await;
+        transport.send(request).await.map_err(Error::other)?;
+        let response = transport.recv().await.map_err(Error::other)?;
+
+        let payload = response
+            .payload
+            .ok_or_else(|| Error::other(ClientSignError::InvalidResponse))?;
+
+        let ClientResponsePayload::EvmSignTransaction(sign_response) = payload else {
+            return Err(Error::other(ClientSignError::InvalidResponse));
+        };
+
+        let Some(result) = sign_response.result else {
+            return Err(Error::other(ClientSignError::InvalidResponse));
+        };
+
+        match result {
+            SignResponseResult::Signature(bytes) => {
+                Signature::try_from(bytes.as_slice()).map_err(Error::other)
+            }
+            SignResponseResult::EvalError(_) | SignResponseResult::Error(_) => {
+                Err(Error::other(ClientSignError::Rejected))
+            }
+        }
+    }
+}
+
+async fn authenticate(
+    transport: &mut ClientTransport,
+    key: ed25519_dalek::SigningKey,
+) -> std::result::Result<(), ConnectError> {
+    transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: key.verifying_key().to_bytes().to_vec(),
+                },
+            )),
+        })
+        .await
+        .map_err(|_| ConnectError::UnexpectedAuthResponse)?;
+
+    let response = transport
+        .recv()
+        .await
+        .map_err(|_| ConnectError::MissingAuthChallenge)?;
+
+    let payload = response.payload.ok_or(ConnectError::MissingAuthChallenge)?;
+    match payload {
+        ClientResponsePayload::AuthChallenge(challenge) => {
+            let challenge_payload = format_challenge(challenge.nonce, &challenge.pubkey);
+            let signature = key.sign(&challenge_payload).to_bytes().to_vec();
+
+            transport
+                .send(ClientRequest {
+                    payload: Some(ClientRequestPayload::AuthChallengeSolution(
+                        AuthChallengeSolution { signature },
+                    )),
+                })
+                .await
+                .map_err(|_| ConnectError::UnexpectedAuthResponse)?;
+
+            // Current server flow does not emit `AuthOk` for SDK clients, so we proceed after
+            // sending the solution. If authentication fails, the first business request will return
+            // a `ClientConnectError` or the stream will close.
+            Ok(())
+        }
+        ClientResponsePayload::ClientConnectError(err) => {
+            match client_connect_error::Code::try_from(err.code)
+                .unwrap_or(client_connect_error::Code::Unknown)
+            {
+                client_connect_error::Code::ApprovalDenied => Err(ConnectError::ApprovalDenied),
+                client_connect_error::Code::NoUserAgentsOnline => {
+                    Err(ConnectError::NoUserAgentsOnline)
+                }
+                client_connect_error::Code::Unknown => Err(ConnectError::UnexpectedAuthResponse),
+            }
+        }
+        _ => Err(ConnectError::UnexpectedAuthResponse),
+    }
+}
+
+#[async_trait]
+impl Signer for ArbiterSigner {
+    async fn sign_hash(&self, _hash: &B256) -> Result<Signature> {
+        Err(Error::other(
+            "hash-only signing is not supported for ArbiterSigner; use transaction signing",
+        ))
+    }
+
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    fn chain_id(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+
+    fn set_chain_id(&mut self, chain_id: Option<ChainId>) {
+        self.chain_id = chain_id;
+    }
+}
+
+#[async_trait]
+impl TxSigner<Signature> for ArbiterSigner {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    async fn sign_transaction(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.sign_transaction_via_arbiter(tx).await
     }
 }

server/crates/arbiter-proto/Cargo.toml

@@ -3,6 +3,7 @@ name = "arbiter-proto"
 version = "0.1.0"
 edition = "2024"
 repository = "https://git.markettakers.org/MarketTakers/arbiter"
+license = "Apache-2.0"
 
 [dependencies]
 tonic.workspace = true
@@ -12,9 +13,25 @@ hex = "0.4.3"
 tonic-prost = "0.14.3"
 prost = "0.14.3"
 kameo.workspace = true
+url = "2.5.8"
+miette.workspace = true
+thiserror.workspace = true
+rustls-pki-types.workspace = true
+base64 = "0.22.1"
 prost-types.workspace = true
+tracing.workspace = true
+async-trait.workspace = true
 
 [build-dependencies]
 tonic-prost-build = "0.14.3"
+protoc-bin-vendored = "3"
+
+[dev-dependencies]
+rstest.workspace = true
+rand.workspace = true
+rcgen.workspace = true
+
+[package.metadata.cargo-shear]
+ignored = ["tonic-prost", "prost", "kameo"]
 
 

server/crates/arbiter-proto/build.rs

@@ -3,16 +3,25 @@ use tonic_prost_build::configure;
 static PROTOBUF_DIR: &str = "../../../protobufs";
 
 fn main() -> Result<(), Box<dyn std::error::Error>> {
+    if std::env::var("PROTOC").is_err() {
+        println!("cargo:warning=PROTOC environment variable not set, using vendored protoc");
+        let protoc = protoc_bin_vendored::protoc_bin_path().unwrap();
+        unsafe { std::env::set_var("PROTOC", protoc) };
+    }
+
+    println!("cargo::rerun-if-changed={PROTOBUF_DIR}");
+
     configure()
         .message_attribute(".", "#[derive(::kameo::Reply)]")
         .compile_protos(
             &[
                 format!("{}/arbiter.proto", PROTOBUF_DIR),
-                format!("{}/auth.proto", PROTOBUF_DIR),
+                format!("{}/user_agent.proto", PROTOBUF_DIR),
+                format!("{}/client.proto", PROTOBUF_DIR),
+                format!("{}/evm.proto", PROTOBUF_DIR),
             ],
             &[PROTOBUF_DIR.to_string()],
         )
-        
         .unwrap();
     Ok(())
 }

server/crates/arbiter-proto/src/lib.rs

@@ -1,19 +1,28 @@
-use crate::proto::auth::AuthChallenge;
+pub mod transport;
+pub mod url;
+
+use base64::{Engine, prelude::BASE64_STANDARD};
 
 pub mod proto {
     tonic::include_proto!("arbiter");
 
-    pub mod auth {
-        tonic::include_proto!("arbiter.auth");
+    pub mod user_agent {
+        tonic::include_proto!("arbiter.user_agent");
+    }
+
+    pub mod client {
+        tonic::include_proto!("arbiter.client");
+    }
+
+    pub mod evm {
+        tonic::include_proto!("arbiter.evm");
     }
 }
 
-pub mod transport;
-
-pub static BOOTSTRAP_TOKEN_PATH: &'static str = "bootstrap_token";
+pub static BOOTSTRAP_PATH: &str = "bootstrap_token";
 
 pub fn home_path() -> Result<std::path::PathBuf, std::io::Error> {
-    static ARBITER_HOME: &'static str = ".arbiter";
+    static ARBITER_HOME: &str = ".arbiter";
     let home_dir = std::env::home_dir().ok_or(std::io::Error::new(
         std::io::ErrorKind::PermissionDenied,
         "can not get home directory",
@@ -25,7 +34,7 @@ pub fn home_path() -> Result<std::path::PathBuf, std::io::Error> {
     Ok(arbiter_home)
 }
 
-pub fn format_challenge(challenge: &AuthChallenge) -> Vec<u8> {
-    let concat_form = format!("{}:{}", challenge.nonce, hex::encode(&challenge.pubkey));
-    concat_form.into_bytes().to_vec()
+pub fn format_challenge(nonce: i32, pubkey: &[u8]) -> Vec<u8> {
+    let concat_form = format!("{}:{}", nonce, BASE64_STANDARD.encode(pubkey));
+    concat_form.into_bytes()
 }

server/crates/arbiter-proto/src/transport.rs

@@ -1,46 +1,309 @@
-use futures::{Stream, StreamExt};
-use tokio::sync::mpsc::{self, error::SendError};
-use tonic::{Status, Streaming};
+//! Transport-facing abstractions for protocol/session code.
+//!
+//! This module separates three concerns:
+//!
+//! - protocol/session logic wants a small duplex interface ([`Bi`])
+//! - transport adapters push concrete stream items to an underlying IO layer
+//! - transport boundaries translate between protocol-facing and transport-facing
+//!   item types via direction-specific converters
+//!
+//! [`Bi`] is intentionally minimal and transport-agnostic:
+//! - [`Bi::recv`] yields inbound protocol messages
+//! - [`Bi::send`] accepts outbound protocol/domain items
+//!
+//! # Generic Ordering Rule
+//!
+//! This module uses a single convention consistently: when a type or trait is
+//! parameterized by protocol message directions, the generic parameters are
+//! declared as `Inbound` first, then `Outbound`.
+//!
+//! For [`Bi`], that means `Bi<Inbound, Outbound>`:
+//! - `recv() -> Option<Inbound>`
+//! - `send(Outbound)`
+//!
+//! For adapter types that are parameterized by direction-specific converters,
+//! inbound-related converter parameters are declared before outbound-related
+//! converter parameters.
+//!
+//! [`RecvConverter`] and [`SendConverter`] are infallible conversion traits used
+//! by adapters to map between protocol-facing and transport-facing item types.
+//! The traits themselves are not result-aware; adapters decide how transport
+//! errors are handled before (or instead of) conversion.
+//!
+//! [`grpc::GrpcAdapter`] combines:
+//! - a tonic inbound stream
+//! - a Tokio sender for outbound transport items
+//! - a [`RecvConverter`] for the receive path
+//! - a [`SendConverter`] for the send path
+//!
+//! [`DummyTransport`] is a no-op implementation useful for tests and local actor
+//! execution where no real network stream exists.
+//!
+//! # Component Interaction
+//!
+//! ```text
+//! inbound (network -> protocol)
+//! ============================
+//!
+//! tonic::Streaming<RecvTransport>
+//!     -> grpc::GrpcAdapter::recv()
+//!          |
+//!          +--> on `Ok(item)`: RecvConverter::convert(RecvTransport) -> Inbound
+//!          +--> on `Err(status)`: log error and close stream (`None`)
+//!     -> Bi::recv()
+//!     -> protocol/session actor
+//!
+//! outbound (protocol -> network)
+//! ==============================
+//!
+//! protocol/session actor
+//!     -> Bi::send(Outbound)
+//!     -> grpc::GrpcAdapter::send()
+//!          |
+//!          +--> SendConverter::convert(Outbound) -> SendTransport
+//!     -> Tokio mpsc::Sender<SendTransport>
+//!     -> tonic response stream
+//! ```
+//!
+//! # Design Notes
+//!
+//! - `send()` returns [`Error`] only for transport delivery failures (for
+//!   example, when the outbound channel is closed).
+//! - [`grpc::GrpcAdapter`] logs tonic receive errors and treats them as stream
+//!   closure (`None`).
+//! - When protocol-facing and transport-facing types are identical, use
+//!   [`IdentityRecvConverter`] / [`IdentitySendConverter`].
 
+use std::marker::PhantomData;
 
-// Abstraction for stream for sans-io capabilities
-pub trait Bi<T, U>: Stream<Item = Result<T, Status>> + Send + Sync + 'static {
-    type Error;
-    fn send(
-        &mut self,
-        item: Result<U, Status>,
-    ) -> impl std::future::Future<Output = Result<(), Self::Error>> + Send;
+use async_trait::async_trait;
+
+/// Errors returned by transport adapters implementing [`Bi`].
+#[derive(thiserror::Error, Debug)]
+pub enum Error {
+    #[error("Transport channel is closed")]
+    ChannelClosed,
+    #[error("Unexpected message received")]
+    UnexpectedMessage,
 }
 
-// Bi-directional stream abstraction for handling gRPC streaming requests and responses
-pub struct BiStream<T, U> {
-    pub request_stream: Streaming<T>,
-    pub response_sender: mpsc::Sender<Result<U, Status>>,
-}
-
-impl<T, U> Stream for BiStream<T, U>
+/// Receives one message from `transport` and extracts a value from it using
+/// `extractor`. Returns [`Error::ChannelClosed`] if the transport closes and
+/// [`Error::UnexpectedMessage`] if `extractor` returns `None`.
+pub async fn expect_message<T, Inbound, Outbound, Target, F>(
+    transport: &mut T,
+    extractor: F,
+) -> Result<Target, Error>
 where
-    T: Send + 'static,
-    U: Send + 'static,
+    T: Bi<Inbound, Outbound> + ?Sized,
+    F: FnOnce(Inbound) -> Option<Target>,
 {
-    type Item = Result<T, Status>;
+    let msg = transport.recv().await.ok_or(Error::ChannelClosed)?;
+    extractor(msg).ok_or(Error::UnexpectedMessage)
+}
 
-    fn poll_next(
-        mut self: std::pin::Pin<&mut Self>,
-        cx: &mut std::task::Context<'_>,
-    ) -> std::task::Poll<Option<Self::Item>> {
-        self.request_stream.poll_next_unpin(cx)
+/// Minimal bidirectional transport abstraction used by protocol code.
+///
+/// `Bi<Inbound, Outbound>` models a duplex channel with:
+/// - inbound items of type `Inbound` read via [`Bi::recv`]
+/// - outbound items of type `Outbound` written via [`Bi::send`]
+#[async_trait]
+pub trait Bi<Inbound, Outbound>: Send + Sync + 'static {
+    async fn send(&mut self, item: Outbound) -> Result<(), Error>;
+
+    async fn recv(&mut self) -> Option<Inbound>;
+}
+
+/// Converts transport-facing inbound items into protocol-facing inbound items.
+pub trait RecvConverter: Send + Sync + 'static {
+    type Input;
+    type Output;
+
+    fn convert(&self, item: Self::Input) -> Self::Output;
+}
+
+/// Converts protocol/domain outbound items into transport-facing outbound items.
+pub trait SendConverter: Send + Sync + 'static {
+    type Input;
+    type Output;
+
+    fn convert(&self, item: Self::Input) -> Self::Output;
+}
+
+/// A [`RecvConverter`] that forwards values unchanged.
+pub struct IdentityRecvConverter<T> {
+    _marker: PhantomData<T>,
+}
+
+impl<T> IdentityRecvConverter<T> {
+    pub fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
     }
 }
 
-impl<T, U> Bi<T, U> for BiStream<T, U>
-where
-    T: Send + 'static,
-    U: Send + 'static,
-{
-    type Error = SendError<Result<U, Status>>;
-
-    async fn send(&mut self, item: Result<U, Status>) -> Result<(), Self::Error> {
-        self.response_sender.send(item).await
+impl<T> Default for IdentityRecvConverter<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T> RecvConverter for IdentityRecvConverter<T>
+where
+    T: Send + Sync + 'static,
+{
+    type Input = T;
+    type Output = T;
+
+    fn convert(&self, item: Self::Input) -> Self::Output {
+        item
+    }
+}
+
+/// A [`SendConverter`] that forwards values unchanged.
+pub struct IdentitySendConverter<T> {
+    _marker: PhantomData<T>,
+}
+
+impl<T> IdentitySendConverter<T> {
+    pub fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T> Default for IdentitySendConverter<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<T> SendConverter for IdentitySendConverter<T>
+where
+    T: Send + Sync + 'static,
+{
+    type Input = T;
+    type Output = T;
+
+    fn convert(&self, item: Self::Input) -> Self::Output {
+        item
+    }
+}
+
+/// gRPC-specific transport adapters and helpers.
+pub mod grpc {
+    use async_trait::async_trait;
+    use futures::StreamExt;
+    use tokio::sync::mpsc;
+    use tonic::Streaming;
+
+    use super::{Bi, Error, RecvConverter, SendConverter};
+
+    /// [`Bi`] adapter backed by a tonic gRPC bidirectional stream.
+    ///
+    /// Tonic receive errors are logged and treated as stream closure (`None`).
+    /// The receive converter is only invoked for successful inbound transport
+    /// items.
+    pub struct GrpcAdapter<InboundConverter, OutboundConverter>
+    where
+        InboundConverter: RecvConverter,
+        OutboundConverter: SendConverter,
+    {
+        sender: mpsc::Sender<OutboundConverter::Output>,
+        receiver: Streaming<InboundConverter::Input>,
+        inbound_converter: InboundConverter,
+        outbound_converter: OutboundConverter,
+    }
+
+    impl<InboundTransport, Inbound, InboundConverter, OutboundConverter>
+        GrpcAdapter<InboundConverter, OutboundConverter>
+    where
+        InboundConverter: RecvConverter<Input = InboundTransport, Output = Inbound>,
+        OutboundConverter: SendConverter,
+    {
+        pub fn new(
+            sender: mpsc::Sender<OutboundConverter::Output>,
+            receiver: Streaming<InboundTransport>,
+            inbound_converter: InboundConverter,
+            outbound_converter: OutboundConverter,
+        ) -> Self {
+            Self {
+                sender,
+                receiver,
+                inbound_converter,
+                outbound_converter,
+            }
+        }
+    }
+
+    #[async_trait]
+    impl<InboundConverter, OutboundConverter> Bi<InboundConverter::Output, OutboundConverter::Input>
+        for GrpcAdapter<InboundConverter, OutboundConverter>
+    where
+        InboundConverter: RecvConverter,
+        OutboundConverter: SendConverter,
+        OutboundConverter::Input: Send + 'static,
+        OutboundConverter::Output: Send + 'static,
+    {
+        #[tracing::instrument(level = "trace", skip(self, item))]
+        async fn send(&mut self, item: OutboundConverter::Input) -> Result<(), Error> {
+            let outbound = self.outbound_converter.convert(item);
+            self.sender
+                .send(outbound)
+                .await
+                .map_err(|_| Error::ChannelClosed)
+        }
+
+        #[tracing::instrument(level = "trace", skip(self))]
+        async fn recv(&mut self) -> Option<InboundConverter::Output> {
+            match self.receiver.next().await {
+                Some(Ok(item)) => Some(self.inbound_converter.convert(item)),
+                Some(Err(error)) => {
+                    tracing::error!(error = ?error, "grpc transport recv failed; closing stream");
+                    None
+                }
+                None => None,
+            }
+        }
+    }
+}
+
+/// No-op [`Bi`] transport for tests and manual actor usage.
+///
+/// `send` drops all items and succeeds. [`Bi::recv`] never resolves and therefore
+/// does not busy-wait or spuriously close the stream.
+pub struct DummyTransport<Inbound, Outbound> {
+    _marker: PhantomData<(Inbound, Outbound)>,
+}
+
+impl<Inbound, Outbound> DummyTransport<Inbound, Outbound> {
+    pub fn new() -> Self {
+        Self {
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<Inbound, Outbound> Default for DummyTransport<Inbound, Outbound> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[async_trait]
+impl<Inbound, Outbound> Bi<Inbound, Outbound> for DummyTransport<Inbound, Outbound>
+where
+    Inbound: Send + Sync + 'static,
+    Outbound: Send + Sync + 'static,
+{
+    async fn send(&mut self, _item: Outbound) -> Result<(), Error> {
+        Ok(())
+    }
+
+    async fn recv(&mut self) -> Option<Inbound> {
+        std::future::pending::<()>().await;
+        None
     }
 }

server/crates/arbiter-proto/src/url.rs

@@ -0,0 +1,128 @@
+use std::fmt::Display;
+
+use base64::{Engine as _, prelude::BASE64_URL_SAFE};
+use rustls_pki_types::CertificateDer;
+
+const ARBITER_URL_SCHEME: &str = "arbiter";
+const CERT_QUERY_KEY: &str = "cert";
+const BOOTSTRAP_TOKEN_QUERY_KEY: &str = "bootstrap_token";
+
+pub struct ArbiterUrl {
+    pub host: String,
+    pub port: u16,
+    pub ca_cert: CertificateDer<'static>,
+    pub bootstrap_token: Option<String>,
+}
+
+impl Display for ArbiterUrl {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut base = format!(
+            "{ARBITER_URL_SCHEME}://{}:{}?{CERT_QUERY_KEY}={}",
+            self.host,
+            self.port,
+            BASE64_URL_SAFE.encode(&self.ca_cert)
+        );
+        if let Some(token) = &self.bootstrap_token {
+            base.push_str(&format!("&{BOOTSTRAP_TOKEN_QUERY_KEY}={}", token));
+        }
+        f.write_str(&base)
+    }
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum Error {
+    #[error("Invalid URL scheme, expected '{ARBITER_URL_SCHEME}://'")]
+    #[diagnostic(
+        code(arbiter::url::invalid_scheme),
+        help("The URL must start with '{ARBITER_URL_SCHEME}://'")
+    )]
+    InvalidScheme,
+    #[error("Missing host in URL")]
+    #[diagnostic(
+        code(arbiter::url::missing_host),
+        help("The URL must include a host, e.g., '{ARBITER_URL_SCHEME}://127.0.0.1:<port>'")
+    )]
+    MissingHost,
+    #[error("Missing port in URL")]
+    #[diagnostic(
+        code(arbiter::url::missing_port),
+        help("The URL must include a port, e.g., '{ARBITER_URL_SCHEME}://127.0.0.1:1234'")
+    )]
+    MissingPort,
+    #[error("Missing 'cert' query parameter in URL")]
+    #[diagnostic(
+        code(arbiter::url::missing_cert),
+        help("The URL must include a 'cert' query parameter")
+    )]
+    MissingCert,
+    #[error("Invalid base64 in 'cert' query parameter: {0}")]
+    #[diagnostic(code(arbiter::url::invalid_cert_base64))]
+    InvalidCertBase64(#[from] base64::DecodeError),
+}
+
+impl<'a> TryFrom<&'a str> for ArbiterUrl {
+    type Error = Error;
+
+    fn try_from(value: &'a str) -> Result<Self, Self::Error> {
+        let url = url::Url::parse(value).map_err(|_| Error::InvalidScheme)?;
+
+        if url.scheme() != ARBITER_URL_SCHEME {
+            return Err(Error::InvalidScheme);
+        }
+
+        let host = url.host_str().ok_or(Error::MissingHost)?.to_string();
+        let port = url.port().ok_or(Error::MissingPort)?;
+        let cert_str = url
+            .query_pairs()
+            .find(|(k, _)| k == CERT_QUERY_KEY)
+            .ok_or(Error::MissingCert)?
+            .1;
+
+        let cert = BASE64_URL_SAFE.decode(cert_str.as_ref())?;
+        let cert = CertificateDer::from_slice(&cert).into_owned();
+
+        let bootstrap_token = url
+            .query_pairs()
+            .find(|(k, _)| k == BOOTSTRAP_TOKEN_QUERY_KEY)
+            .map(|(_, v)| v.to_string());
+
+        Ok(ArbiterUrl {
+            host,
+            port,
+            ca_cert: cert,
+            bootstrap_token,
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use rcgen::generate_simple_self_signed;
+    use rstest::rstest;
+
+    use super::*;
+
+    #[rstest]
+
+    fn test_parsing_correctness(
+        #[values("127.0.0.1", "localhost", "192.168.1.1", "some.domain.com")] host: &str,
+
+        #[values(None, Some("token123".to_string()))] bootstrap_token: Option<String>,
+    ) {
+        let cert = generate_simple_self_signed(&["Arbiter CA".into()]).unwrap();
+        let cert = cert.cert.der();
+
+        let url = ArbiterUrl {
+            host: host.to_string(),
+            port: 1234,
+            ca_cert: cert.clone().into_owned(),
+            bootstrap_token,
+        };
+        let url_str = url.to_string();
+        let parsed_url = ArbiterUrl::try_from(url_str.as_str()).unwrap();
+        assert_eq!(url.host, parsed_url.host);
+        assert_eq!(url.port, parsed_url.port);
+        assert_eq!(url.ca_cert.to_vec(), parsed_url.ca_cert.to_vec());
+        assert_eq!(url.bootstrap_token, parsed_url.bootstrap_token);
+    }
+}

server/crates/arbiter-server/Cargo.toml

@@ -3,15 +3,13 @@ name = "arbiter-server"
 version = "0.1.0"
 edition = "2024"
 repository = "https://git.markettakers.org/MarketTakers/arbiter"
+license = "Apache-2.0"
+
+[lints]
+workspace = true
 
 [dependencies]
-diesel = { version = "2.3.6", features = [
-    "sqlite",
-    "uuid",
-    "time",
-    "chrono",
-    "serde_json",
-] }
+diesel = { version = "2.3.6", features = ["chrono", "returning_clauses_for_sqlite_3_35", "serde_json", "time", "uuid"] }
 diesel-async = { version = "0.7.4", features = [
     "bb8",
     "migrations",
@@ -21,7 +19,9 @@ diesel-async = { version = "0.7.4", features = [
 ed25519-dalek.workspace = true
 arbiter-proto.path = "../arbiter-proto"
 tracing.workspace = true
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 tonic.workspace = true
+tonic.features = ["tls-aws-lc"]
 tokio.workspace = true
 rustls.workspace = true
 smlang.workspace = true
@@ -34,16 +34,24 @@ futures.workspace = true
 tokio-stream.workspace = true
 dashmap = "6.1.0"
 rand.workspace = true
-rcgen = { version = "0.14.7", features = [
-    "aws_lc_rs",
-    "pem",
-    "x509-parser",
-    "zeroize",
-], default-features = false }
+rcgen.workspace = true
 chrono.workspace = true
 memsafe = "0.4.0"
 zeroize = { version = "1.8.2", features = ["std", "simd"] }
 kameo.workspace = true
+x25519-dalek.workspace = true
+chacha20poly1305 = { version = "0.10.1", features = ["std"] }
+argon2 = { version = "0.5.3", features = ["zeroize"] }
+restructed = "0.2.2"
+strum = { version = "0.27.2", features = ["derive"] }
+pem = "3.0.6"
+k256.workspace = true
+rsa.workspace = true
+sha2.workspace = true
+spki.workspace = true
+alloy.workspace = true
+arbiter-tokens-registry.path = "../arbiter-tokens-registry"
 
 [dev-dependencies]
+insta = "1.46.3"
 test-log = { version = "0.2", default-features = false, features = ["trace"] }

server/crates/arbiter-server/migrations/2026-02-14-171124-0000_init/up.sql

@@ -1,31 +1,159 @@
-create table if not exists aead_encrypted (
+create table if not exists root_key_history (
     id INTEGER not null PRIMARY KEY,
-    current_nonce integer not null default(1), -- if re-encrypted, this should be incremented
+    -- root key stored as aead encrypted artifact, with only difference that it's decrypted by unseal key (derived from user password)
+    root_key_encryption_nonce blob not null default(1), -- if re-encrypted, this should be incremented. Used for encrypting root key
+    data_encryption_nonce blob not null default(1), -- nonce used for encrypting with key itself
     ciphertext blob not null,
     tag blob not null,
-    schema_version integer not null default(1) -- server would need to reencrypt, because this means that we have changed algorithm
+    schema_version integer not null default(1), -- server would need to reencrypt, because this means that we have changed algorithm
+    salt blob not null -- for key deriviation 
+) STRICT;
+
+create table if not exists aead_encrypted (
+    id INTEGER not null PRIMARY KEY,
+    current_nonce blob not null default(1), -- if re-encrypted, this should be incremented
+    ciphertext blob not null,
+    tag blob not null,
+    schema_version integer not null default(1), -- server would need to reencrypt, because this means that we have changed algorithm
+    associated_root_key_id integer not null references root_key_history (id) on delete RESTRICT,
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create unique index if not exists uniq_nonce_per_root_key on aead_encrypted (
+    current_nonce,
+    associated_root_key_id
+);
+
+create table if not exists tls_history (
+    id INTEGER not null PRIMARY KEY,
+    cert text not null,
+    cert_key text not null, -- PEM Encoded private key
+    ca_cert text not null, 
+    ca_key text not null, -- PEM Encoded private key
+    created_at integer not null default(unixepoch ('now'))
 ) STRICT;
 
 -- This is a singleton
 create table if not exists arbiter_settings (
     id INTEGER not null PRIMARY KEY CHECK (id = 1), -- singleton row, id must be 1
-    root_key_id integer references aead_encrypted (id) on delete RESTRICT, -- if null, means wasn't bootstrapped yet
-    cert_key blob not null,
-    cert blob not null
+    root_key_id integer references root_key_history (id) on delete RESTRICT, -- if null, means wasn't bootstrapped yet
+    tls_id integer references tls_history (id) on delete RESTRICT
 ) STRICT;
 
+insert into arbiter_settings (id) values (1) on conflict do nothing; -- ensure singleton row exists
+
 create table if not exists useragent_client (
     id integer not null primary key,
-    nonce integer not null default (1), -- used for auth challenge
+    nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
+    key_type integer not null default(1), -- 1=Ed25519, 2=ECDSA(secp256k1)
     created_at integer not null default(unixepoch ('now')),
     updated_at integer not null default(unixepoch ('now'))
 ) STRICT;
 
 create table if not exists program_client (
     id integer not null primary key,
-    nonce integer not null default (1), -- used for auth challenge
+    nonce integer not null default(1), -- used for auth challenge
     public_key blob not null,
     created_at integer not null default(unixepoch ('now')),
     updated_at integer not null default(unixepoch ('now'))
-) STRICT;
+) STRICT;
+
+create table if not exists evm_wallet (
+    id integer not null primary key,
+    address blob not null, -- 20-byte Ethereum address
+    aead_encrypted_id integer not null references aead_encrypted (id) on delete RESTRICT,
+    created_at integer not null default(unixepoch ('now'))
+) STRICT;
+
+create unique index if not exists uniq_evm_wallet_address on evm_wallet (address);
+create unique index if not exists uniq_evm_wallet_aead on evm_wallet (aead_encrypted_id);
+
+create table if not exists evm_ether_transfer_limit (
+    id integer not null primary key,
+    window_secs integer not null,           -- window duration in seconds
+    max_volume blob not null                -- big-endian 32-byte U256
+) STRICT;
+
+-- Shared grant properties: client scope, timeframe, fee caps, and rate limit
+create table if not exists evm_basic_grant (
+    id integer not null primary key,
+    wallet_id integer not null references evm_wallet(id) on delete restrict, 
+    client_id integer not null references program_client(id) on delete restrict,
+    chain_id integer not null,              -- EIP-155 chain ID
+    valid_from integer,                     -- unix timestamp (seconds), null = no lower bound
+    valid_until integer,                    -- unix timestamp (seconds), null = no upper bound
+    max_gas_fee_per_gas blob,               -- big-endian 32-byte U256, null = unlimited
+    max_priority_fee_per_gas blob,          -- big-endian 32-byte U256, null = unlimited
+    rate_limit_count integer,               -- max transactions in window, null = unlimited
+    rate_limit_window_secs integer,         -- window duration in seconds, null = unlimited
+    revoked_at integer,                     -- unix timestamp when revoked, null = still active
+    created_at integer not null default(unixepoch('now'))
+) STRICT;
+
+-- Shared transaction log for all EVM grants, used for rate limit tracking and auditing
+create table if not exists evm_transaction_log (
+    id integer not null primary key,
+    grant_id integer not null references evm_basic_grant(id) on delete restrict,
+    client_id integer not null references program_client(id) on delete restrict,
+    wallet_id integer not null references evm_wallet(id) on delete restrict,
+    chain_id integer not null,
+    eth_value blob not null,     -- always present on any EVM tx
+    signed_at integer not null default(unixepoch('now'))
+) STRICT;
+
+create index if not exists idx_evm_basic_grant_wallet_chain on evm_basic_grant(client_id, wallet_id, chain_id);
+
+-- ===============================
+-- ERC20 token transfer grant
+-- ===============================
+create table if not exists evm_token_transfer_grant (
+    id integer not null primary key,
+    basic_grant_id integer not null unique references evm_basic_grant(id) on delete cascade,
+    token_contract blob not null,            -- 20-byte ERC20 contract address
+    receiver blob                            -- 20-byte recipient address or null if every recipient allowed
+) STRICT;
+
+-- Per-window volume limits for token transfer grants
+create table if not exists evm_token_transfer_volume_limit (
+    id integer not null primary key,
+    grant_id integer not null references evm_token_transfer_grant(id) on delete cascade,
+    window_secs integer not null,           -- window duration in seconds
+    max_volume blob not null                -- big-endian 32-byte U256
+) STRICT;
+
+-- Log table for token transfer grant usage
+create table if not exists evm_token_transfer_log (
+    id integer not null primary key,
+    grant_id integer not null references evm_token_transfer_grant(id) on delete restrict,
+    log_id integer not null references evm_transaction_log(id) on delete restrict,
+    chain_id integer not null,              -- EIP-155 chain ID
+    token_contract blob not null,           -- 20-byte ERC20 contract address
+    recipient_address blob not null,        -- 20-byte recipient address
+    value blob not null,                    -- big-endian 32-byte U256
+    created_at integer not null default(unixepoch('now'))
+) STRICT;
+
+create index if not exists idx_token_transfer_log_grant on evm_token_transfer_log(grant_id);
+create index if not exists idx_token_transfer_log_log_id on evm_token_transfer_log(log_id);
+create index if not exists idx_token_transfer_log_chain on evm_token_transfer_log(chain_id);
+
+
+-- ===============================
+-- Ether transfer grant (uses base log)
+-- ===============================
+create table if not exists evm_ether_transfer_grant (
+    id integer not null primary key,
+    basic_grant_id integer not null unique references evm_basic_grant(id) on delete cascade,
+    limit_id integer not null references evm_ether_transfer_limit(id) on delete restrict
+) STRICT;
+
+-- Specific recipient addresses for an ether transfer grant
+create table if not exists evm_ether_transfer_grant_target (
+    id integer not null primary key,
+    grant_id integer not null references evm_ether_transfer_grant(id) on delete cascade,
+    address blob not null                   -- 20-byte recipient address
+) STRICT;
+
+create unique index if not exists uniq_ether_transfer_target on evm_ether_transfer_grant_target(grant_id, address);
+

server/crates/arbiter-server/migrations/2026-03-15-103112-0000_add_program_client_pubkey_unique/down.sql

@@ -0,0 +1 @@
+DROP INDEX IF EXISTS program_client_public_key_unique;

server/crates/arbiter-server/migrations/2026-03-15-103112-0000_add_program_client_pubkey_unique/up.sql

@@ -0,0 +1,2 @@
+CREATE UNIQUE INDEX program_client_public_key_unique
+    ON program_client (public_key);

server/crates/arbiter-server/src/actors.rs

@@ -1,2 +0,0 @@
-pub mod user_agent;
-pub mod client;

server/crates/arbiter-server/src/actors/bootstrap.rs

@@ -1,40 +1,37 @@
-use arbiter_proto::{BOOTSTRAP_TOKEN_PATH, home_path};
-use diesel::{ExpressionMethods, QueryDsl};
+use arbiter_proto::{BOOTSTRAP_PATH, home_path};
+use diesel::QueryDsl;
 use diesel_async::RunQueryDsl;
 use kameo::{Actor, messages};
-use memsafe::MemSafe;
 use miette::Diagnostic;
-use rand::{RngExt, distr::StandardUniform, make_rng, rngs::StdRng};
-use secrecy::SecretString;
-use thiserror::Error;
-use tracing::info;
-use zeroize::{Zeroize, Zeroizing};
-
-use crate::{
-    context::{self, ServerContext},
-    db::{self, DatabasePool, schema},
+use rand::{
+    RngExt,
+    distr::{Alphanumeric},
+    make_rng,
+    rngs::StdRng,
 };
+use thiserror::Error;
 
+use crate::db::{self, DatabasePool, schema};
 const TOKEN_LENGTH: usize = 64;
 
 pub async fn generate_token() -> Result<String, std::io::Error> {
     let rng: StdRng = make_rng();
 
-    let token: String = rng
-        .sample_iter::<char, _>(StandardUniform)
-        .take(TOKEN_LENGTH)
-        .fold(Default::default(), |mut accum, char| {
+    let token: String = rng.sample_iter(Alphanumeric).take(TOKEN_LENGTH).fold(
+        Default::default(),
+        |mut accum, char| {
             accum += char.to_string().as_str();
             accum
-        });
+        },
+    );
 
-    tokio::fs::write(home_path()?.join(BOOTSTRAP_TOKEN_PATH), token.as_str()).await?;
+    tokio::fs::write(home_path()?.join(BOOTSTRAP_PATH), token.as_str()).await?;
 
     Ok(token)
 }
 
 #[derive(Error, Debug, Diagnostic)]
-pub enum BootstrapError {
+pub enum Error {
     #[error("Database error: {0}")]
     #[diagnostic(code(arbiter_server::bootstrap::database))]
     Database(#[from] db::PoolError),
@@ -49,12 +46,12 @@ pub enum BootstrapError {
 }
 
 #[derive(Actor)]
-pub struct BootstrapActor {
+pub struct Bootstrapper {
     token: Option<String>,
 }
 
-impl BootstrapActor {
-    pub async fn new(db: &DatabasePool) -> Result<Self, BootstrapError> {
+impl Bootstrapper {
+    pub async fn new(db: &DatabasePool) -> Result<Self, Error> {
         let mut conn = db.get().await?;
 
         let row_count: i64 = schema::useragent_client::table
@@ -64,10 +61,9 @@ impl BootstrapActor {
 
         drop(conn);
 
+
         let token = if row_count == 0 {
             let token = generate_token().await?;
-            info!(%token, "Generated bootstrap token");
-            tokio::fs::write(home_path()?.join(BOOTSTRAP_TOKEN_PATH), token.as_str()).await?;
             Some(token)
         } else {
             None
@@ -75,15 +71,10 @@ impl BootstrapActor {
 
         Ok(Self { token })
     }
-
-    #[cfg(test)]
-    pub fn get_token(&self) -> Option<String> {
-        self.token.clone()
-    }
 }
 
 #[messages]
-impl BootstrapActor {
+impl Bootstrapper {
     #[message]
     pub fn is_correct_token(&self, token: String) -> bool {
         match &self.token {
@@ -102,3 +93,11 @@ impl BootstrapActor {
         }
     }
 }
+
+#[messages]
+impl Bootstrapper {
+    #[message]
+    pub fn get_token(&self) -> Option<String> {
+        self.token.clone()
+    }
+}

server/crates/arbiter-server/src/actors/client.rs

@@ -1,12 +0,0 @@
-use arbiter_proto::{
-    proto::{ClientRequest, ClientResponse},
-    transport::Bi,
-};
-
-use crate::ServerContext;
-
-pub(crate) async fn handle_client(
-    _context: ServerContext,
-    _bistream: impl Bi<ClientRequest, ClientResponse>,
-) {
-}

server/crates/arbiter-server/src/actors/client/auth.rs

@@ -0,0 +1,183 @@
+use arbiter_proto::{
+    format_challenge,
+    proto::client::{
+        AuthChallenge, AuthChallengeSolution, ClientConnectError, ClientRequest, ClientResponse,
+        client_connect_error::Code as ConnectErrorCode,
+        client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+    },
+    transport::expect_message,
+};
+use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl as _, update};
+use diesel_async::RunQueryDsl as _;
+use ed25519_dalek::VerifyingKey;
+use tracing::error;
+
+use crate::{
+    actors::client::ClientConnection,
+    db::{self, schema::program_client},
+};
+
+use super::session::ClientSession;
+
+#[derive(thiserror::Error, Debug, Clone, PartialEq, Eq)]
+pub enum Error {
+    #[error("Unexpected message payload")]
+    UnexpectedMessagePayload,
+    #[error("Invalid client public key length")]
+    InvalidClientPubkeyLength,
+    #[error("Invalid client public key encoding")]
+    InvalidAuthPubkeyEncoding,
+    #[error("Database pool unavailable")]
+    DatabasePoolUnavailable,
+    #[error("Database operation failed")]
+    DatabaseOperationFailed,
+    #[error("Invalid challenge solution")]
+    InvalidChallengeSolution,
+    #[error("Client not registered")]
+    NotRegistered,
+    #[error("Internal error")]
+    InternalError,
+    #[error("Transport error")]
+    Transport,
+}
+
+/// Atomically reads and increments the nonce for a known client.
+/// Returns `None` if the pubkey is not registered.
+async fn get_nonce(
+    db: &db::DatabasePool,
+    pubkey: &VerifyingKey,
+) -> Result<Option<(i32, i32)>, Error> {
+    let pubkey_bytes = pubkey.as_bytes().to_vec();
+
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+
+    conn.exclusive_transaction(|conn| {
+        let pubkey_bytes = pubkey_bytes.clone();
+        Box::pin(async move {
+            let Some((client_id, current_nonce)) = program_client::table
+                .filter(program_client::public_key.eq(&pubkey_bytes))
+                .select((program_client::id, program_client::nonce))
+                .first::<(i32, i32)>(conn)
+                .await
+                .optional()?
+            else {
+                return Result::<_, diesel::result::Error>::Ok(None);
+            };
+
+            update(program_client::table)
+                .filter(program_client::public_key.eq(&pubkey_bytes))
+                .set(program_client::nonce.eq(current_nonce + 1))
+                .execute(conn)
+                .await?;
+
+            Ok(Some((client_id, current_nonce)))
+        })
+    })
+    .await
+    .map_err(|e| {
+        error!(error = ?e, "Database error");
+        Error::DatabaseOperationFailed
+    })
+}
+
+async fn challenge_client(
+    props: &mut ClientConnection,
+    pubkey: VerifyingKey,
+    nonce: i32,
+) -> Result<(), Error> {
+    let challenge = AuthChallenge {
+        pubkey: pubkey.as_bytes().to_vec(),
+        nonce,
+    };
+
+    props
+        .transport
+        .send(Ok(ClientResponse {
+            payload: Some(ClientResponsePayload::AuthChallenge(challenge.clone())),
+        }))
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to send auth challenge");
+            Error::Transport
+        })?;
+
+    let AuthChallengeSolution { signature } =
+        expect_message(&mut *props.transport, |req: ClientRequest| {
+            match req.payload? {
+                ClientRequestPayload::AuthChallengeSolution(s) => Some(s),
+                _ => None,
+            }
+        })
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Failed to receive challenge solution");
+            Error::Transport
+        })?;
+
+    let formatted = format_challenge(nonce, &challenge.pubkey);
+    let sig = signature.as_slice().try_into().map_err(|_| {
+        error!("Invalid signature length");
+        Error::InvalidChallengeSolution
+    })?;
+
+    pubkey.verify_strict(&formatted, &sig).map_err(|_| {
+        error!("Challenge solution verification failed");
+        Error::InvalidChallengeSolution
+    })?;
+
+    Ok(())
+}
+
+fn connect_error_code(err: &Error) -> ConnectErrorCode {
+    match err {
+        Error::NotRegistered => ConnectErrorCode::ApprovalDenied,
+        _ => ConnectErrorCode::Unknown,
+    }
+}
+
+async fn authenticate(props: &mut ClientConnection) -> Result<(VerifyingKey, i32), Error> {
+    let Some(ClientRequest {
+        payload: Some(ClientRequestPayload::AuthChallengeRequest(challenge)),
+    }) = props.transport.recv().await
+    else {
+        return Err(Error::Transport);
+    };
+
+    let pubkey_bytes = challenge
+        .pubkey
+        .as_array()
+        .ok_or(Error::InvalidClientPubkeyLength)?;
+    let pubkey =
+        VerifyingKey::from_bytes(pubkey_bytes).map_err(|_| Error::InvalidAuthPubkeyEncoding)?;
+
+    let (client_id, nonce) = match get_nonce(&props.db, &pubkey).await? {
+        Some((client_id, nonce)) => (client_id, nonce),
+        None => return Err(Error::NotRegistered),
+    };
+
+    challenge_client(props, pubkey, nonce).await?;
+
+    Ok((pubkey, client_id))
+}
+
+pub async fn authenticate_and_create(mut props: ClientConnection) -> Result<ClientSession, Error> {
+    match authenticate(&mut props).await {
+        Ok((_pubkey, client_id)) => Ok(ClientSession::new(props, client_id)),
+        Err(err) => {
+            let code = connect_error_code(&err);
+            let _ = props
+                .transport
+                .send(Ok(ClientResponse {
+                    payload: Some(ClientResponsePayload::ClientConnectError(
+                        ClientConnectError { code: code.into() },
+                    )),
+                }))
+                .await;
+            Err(err)
+        }
+    }
+}

server/crates/arbiter-server/src/actors/client/mod.rs

@@ -0,0 +1,58 @@
+use arbiter_proto::{
+    proto::client::{ClientRequest, ClientResponse},
+    transport::Bi,
+};
+use kameo::actor::Spawn;
+use tracing::{error, info};
+
+use crate::{
+    actors::{GlobalActors, client::session::ClientSession},
+    db,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
+pub enum ClientError {
+    #[error("Expected message with payload")]
+    MissingRequestPayload,
+    #[error("Unexpected request payload")]
+    UnexpectedRequestPayload,
+    #[error("State machine error")]
+    StateTransitionFailed,
+    #[error("Connection registration failed")]
+    ConnectionRegistrationFailed,
+    #[error(transparent)]
+    Auth(#[from] auth::Error),
+}
+
+pub type Transport = Box<dyn Bi<ClientRequest, Result<ClientResponse, ClientError>> + Send>;
+
+pub struct ClientConnection {
+    pub(crate) db: db::DatabasePool,
+    pub(crate) transport: Transport,
+    pub(crate) actors: GlobalActors,
+}
+
+impl ClientConnection {
+    pub fn new(db: db::DatabasePool, transport: Transport, actors: GlobalActors) -> Self {
+        Self {
+            db,
+            transport,
+            actors,
+        }
+    }
+}
+
+pub mod auth;
+pub mod session;
+
+pub async fn connect_client(props: ClientConnection) {
+    match auth::authenticate_and_create(props).await {
+        Ok(session) => {
+            ClientSession::spawn(session);
+            info!("Client authenticated, session started");
+        }
+        Err(err) => {
+            error!(?err, "Authentication failed, closing connection");
+        }
+    }
+}

server/crates/arbiter-server/src/actors/client/session.rs

@@ -0,0 +1,151 @@
+use alloy::{consensus::TxEip1559, primitives::Address, rlp::Decodable};
+use arbiter_proto::proto::{
+    client::{
+        ClientRequest, ClientResponse, client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+    },
+    evm::{
+        EvmError, EvmSignTransactionResponse, evm_sign_transaction_response::Result as SignResult,
+    },
+};
+use kameo::Actor;
+use tokio::select;
+use tracing::{error, info};
+
+use crate::{
+    actors::{
+        GlobalActors,
+        client::{ClientConnection, ClientError},
+        evm::ClientSignTransaction,
+        router::RegisterClient,
+    },
+    db,
+};
+
+pub struct ClientSession {
+    props: ClientConnection,
+    client_id: i32,
+}
+
+impl ClientSession {
+    pub(crate) fn new(props: ClientConnection, client_id: i32) -> Self {
+        Self { props, client_id }
+    }
+
+    pub async fn process_transport_inbound(&mut self, req: ClientRequest) -> Output {
+        let msg = req.payload.ok_or_else(|| {
+            error!(actor = "client", "Received message with no payload");
+            ClientError::MissingRequestPayload
+        })?;
+
+        match msg {
+            ClientRequestPayload::EvmSignTransaction(sign_req) => {
+                let wallet_address: [u8; 20] = sign_req
+                    .wallet_address
+                    .try_into()
+                    .map_err(|_| ClientError::UnexpectedRequestPayload)?;
+
+                let mut rlp_bytes: &[u8] = &sign_req.rlp_transaction;
+                let tx = TxEip1559::decode(&mut rlp_bytes)
+                    .map_err(|_| ClientError::UnexpectedRequestPayload)?;
+
+                let result = self
+                    .props
+                    .actors
+                    .evm
+                    .ask(ClientSignTransaction {
+                        client_id: self.client_id,
+                        wallet_address: Address::from_slice(&wallet_address),
+                        transaction: tx,
+                    })
+                    .await;
+
+                let response_result = match result {
+                    Ok(signature) => SignResult::Signature(signature.as_bytes().to_vec()),
+                    Err(err) => {
+                        error!(?err, "client sign transaction failed");
+                        SignResult::Error(EvmError::Internal.into())
+                    }
+                };
+
+                Ok(ClientResponse {
+                    payload: Some(ClientResponsePayload::EvmSignTransaction(
+                        EvmSignTransactionResponse {
+                            result: Some(response_result),
+                        },
+                    )),
+                })
+            }
+            _ => Err(ClientError::UnexpectedRequestPayload),
+        }
+    }
+}
+
+type Output = Result<ClientResponse, ClientError>;
+
+impl Actor for ClientSession {
+    type Args = Self;
+
+    type Error = ClientError;
+
+    async fn on_start(
+        args: Self::Args,
+        this: kameo::prelude::ActorRef<Self>,
+    ) -> Result<Self, Self::Error> {
+        args.props
+            .actors
+            .router
+            .ask(RegisterClient { actor: this })
+            .await
+            .map_err(|_| ClientError::ConnectionRegistrationFailed)?;
+        Ok(args)
+    }
+
+    async fn next(
+        &mut self,
+        _actor_ref: kameo::prelude::WeakActorRef<Self>,
+        mailbox_rx: &mut kameo::prelude::MailboxReceiver<Self>,
+    ) -> Option<kameo::mailbox::Signal<Self>> {
+        loop {
+            select! {
+                signal = mailbox_rx.recv() => {
+                    return signal;
+                }
+                msg = self.props.transport.recv() => {
+                    match msg {
+                        Some(request) => {
+                            match self.process_transport_inbound(request).await {
+                                Ok(resp) => {
+                                    if self.props.transport.send(Ok(resp)).await.is_err() {
+                                        error!(actor = "client", reason = "channel closed", "send.failed");
+                                        return Some(kameo::mailbox::Signal::Stop);
+                                    }
+                                }
+                                Err(err) => {
+                                    let _ = self.props.transport.send(Err(err)).await;
+                                    return Some(kameo::mailbox::Signal::Stop);
+                                }
+                            }
+                        }
+                        None => {
+                            info!(actor = "client", "transport.closed");
+                            return Some(kameo::mailbox::Signal::Stop);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl ClientSession {
+    pub fn new_test(db: db::DatabasePool, actors: GlobalActors) -> Self {
+        use arbiter_proto::transport::DummyTransport;
+        let transport: super::Transport = Box::new(DummyTransport::new());
+        let props = ClientConnection::new(db, transport, actors);
+        Self {
+            props,
+            client_id: 0,
+        }
+    }
+}

server/crates/arbiter-server/src/actors/evm/mod.rs

@@ -0,0 +1,246 @@
+use alloy::{consensus::TxEip1559, primitives::Address, signers::Signature};
+use diesel::{ExpressionMethods, OptionalExtension as _, QueryDsl, SelectableHelper as _, dsl::insert_into};
+use diesel_async::RunQueryDsl;
+use kameo::{Actor, actor::ActorRef, messages};
+use memsafe::MemSafe;
+use rand::{SeedableRng, rng, rngs::StdRng};
+
+use crate::{
+    actors::keyholder::{CreateNew, Decrypt, KeyHolder},
+    db::{self, DatabasePool, models::{self, EvmBasicGrant, SqliteTimestamp}, schema},
+    evm::{
+        self, RunKind,
+        policies::{
+            FullGrant, SharedGrantSettings, SpecificGrant, SpecificMeaning,
+            ether_transfer::EtherTransfer,
+            token_transfers::TokenTransfer,
+        },
+    },
+};
+
+pub use crate::evm::safe_signer;
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum SignTransactionError {
+    #[error("Wallet not found")]
+    #[diagnostic(code(arbiter::evm::sign::wallet_not_found))]
+    WalletNotFound,
+
+    #[error("Database error: {0}")]
+    #[diagnostic(code(arbiter::evm::sign::database))]
+    Database(#[from] diesel::result::Error),
+
+    #[error("Database pool error: {0}")]
+    #[diagnostic(code(arbiter::evm::sign::pool))]
+    Pool(#[from] db::PoolError),
+
+    #[error("Keyholder error: {0}")]
+    #[diagnostic(code(arbiter::evm::sign::keyholder))]
+    Keyholder(#[from] crate::actors::keyholder::Error),
+
+    #[error("Keyholder mailbox error")]
+    #[diagnostic(code(arbiter::evm::sign::keyholder_send))]
+    KeyholderSend,
+
+    #[error("Signing error: {0}")]
+    #[diagnostic(code(arbiter::evm::sign::signing))]
+    Signing(#[from] alloy::signers::Error),
+
+    #[error("Policy error: {0}")]
+    #[diagnostic(code(arbiter::evm::sign::vet))]
+    Vet(#[from] evm::VetError),
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum Error {
+    #[error("Keyholder error: {0}")]
+    #[diagnostic(code(arbiter::evm::keyholder))]
+    Keyholder(#[from] crate::actors::keyholder::Error),
+
+    #[error("Keyholder mailbox error")]
+    #[diagnostic(code(arbiter::evm::keyholder_send))]
+    KeyholderSend,
+
+    #[error("Database error: {0}")]
+    #[diagnostic(code(arbiter::evm::database))]
+    Database(#[from] diesel::result::Error),
+
+    #[error("Database pool error: {0}")]
+    #[diagnostic(code(arbiter::evm::database_pool))]
+    DatabasePool(#[from] db::PoolError),
+
+    #[error("Grant creation error: {0}")]
+    #[diagnostic(code(arbiter::evm::creation))]
+    Creation(#[from] evm::CreationError),
+}
+
+#[derive(Actor)]
+pub struct EvmActor {
+    pub keyholder: ActorRef<KeyHolder>,
+    pub db: DatabasePool,
+    pub rng: StdRng,
+    pub engine: evm::Engine,
+}
+
+impl EvmActor {
+    pub fn new(keyholder: ActorRef<KeyHolder>, db: DatabasePool) -> Self {
+        // is it safe to seed rng from system once?
+        // todo: audit
+        let rng = StdRng::from_rng(&mut rng());
+        let engine = evm::Engine::new(db.clone());
+        Self { keyholder, db, rng, engine }
+    }
+}
+
+#[messages]
+impl EvmActor {
+    #[message]
+    pub async fn generate(&mut self) -> Result<Address, Error> {
+        let (mut key_cell, address) = safe_signer::generate(&mut self.rng);
+
+        // Move raw key bytes into a Vec<u8> MemSafe for KeyHolder
+        let plaintext = {
+            let reader = key_cell.read().expect("MemSafe read");
+            MemSafe::new(reader.to_vec()).expect("MemSafe allocation")
+        };
+
+        let aead_id: i32 = self
+            .keyholder
+            .ask(CreateNew { plaintext })
+            .await
+            .map_err(|_| Error::KeyholderSend)?;
+
+        let mut conn = self.db.get().await?;
+        insert_into(schema::evm_wallet::table)
+            .values(&models::NewEvmWallet {
+                address: address.as_slice().to_vec(),
+                aead_encrypted_id: aead_id,
+            })
+            .execute(&mut conn)
+            .await?;
+
+        Ok(address)
+    }
+
+    #[message]
+    pub async fn list_wallets(&self) -> Result<Vec<Address>, Error> {
+        let mut conn = self.db.get().await?;
+        let rows: Vec<models::EvmWallet> = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .load(&mut conn)
+            .await?;
+
+        Ok(rows
+            .into_iter()
+            .map(|w| Address::from_slice(&w.address))
+            .collect())
+    }
+}
+
+#[messages]
+impl EvmActor {
+    #[message]
+    pub async fn useragent_create_grant(
+        &mut self,
+        client_id: i32,
+        basic: SharedGrantSettings,
+        grant: SpecificGrant,
+    ) -> Result<i32, evm::CreationError> {
+        match grant {
+            SpecificGrant::EtherTransfer(settings) => {
+                self.engine
+                    .create_grant::<EtherTransfer>(client_id, FullGrant { basic, specific: settings })
+                    .await
+            }
+            SpecificGrant::TokenTransfer(settings) => {
+                self.engine
+                    .create_grant::<TokenTransfer>(client_id, FullGrant { basic, specific: settings })
+                    .await
+            }
+        }
+    }
+
+    #[message]
+    pub async fn useragent_delete_grant(&mut self, grant_id: i32) -> Result<(), Error> {
+        let mut conn = self.db.get().await?;
+        diesel::update(schema::evm_basic_grant::table)
+            .filter(schema::evm_basic_grant::id.eq(grant_id))
+            .set(schema::evm_basic_grant::revoked_at.eq(SqliteTimestamp::now()))
+            .execute(&mut conn)
+            .await?;
+        Ok(())
+    }
+
+    #[message]
+    pub async fn useragent_list_grants(
+        &mut self,
+        wallet_id: Option<i32>,
+    ) -> Result<Vec<EvmBasicGrant>, Error> {
+        let mut conn = self.db.get().await?;
+        let mut query = schema::evm_basic_grant::table
+            .select(EvmBasicGrant::as_select())
+            .filter(schema::evm_basic_grant::revoked_at.is_null())
+            .into_boxed();
+        if let Some(wid) = wallet_id {
+            query = query.filter(schema::evm_basic_grant::wallet_id.eq(wid));
+        }
+        Ok(query.load(&mut conn).await?)
+    }
+
+    #[message]
+    pub async fn shared_analyze_transaction(
+        &mut self,
+        client_id: i32,
+        wallet_address: Address,
+        transaction: TxEip1559,
+    ) -> Result<SpecificMeaning, SignTransactionError> {
+        let mut conn = self.db.get().await?;
+        let wallet = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .filter(schema::evm_wallet::address.eq(wallet_address.as_slice()))
+            .first(&mut conn)
+            .await
+            .optional()?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        drop(conn);
+
+        let meaning = self.engine
+            .evaluate_transaction(wallet.id, client_id, transaction.clone(), RunKind::Execution)
+            .await?;
+
+        Ok(meaning)
+    }
+
+    #[message]
+    pub async fn client_sign_transaction(
+        &mut self,
+        client_id: i32,
+        wallet_address: Address,
+        mut transaction: TxEip1559,
+    ) -> Result<Signature, SignTransactionError> {
+        let mut conn = self.db.get().await?;
+        let wallet = schema::evm_wallet::table
+            .select(models::EvmWallet::as_select())
+            .filter(schema::evm_wallet::address.eq(wallet_address.as_slice()))
+            .first(&mut conn)
+            .await
+            .optional()?
+            .ok_or(SignTransactionError::WalletNotFound)?;
+        drop(conn);
+
+        let raw_key: MemSafe<Vec<u8>> = self
+            .keyholder
+            .ask(Decrypt { aead_id: wallet.aead_encrypted_id })
+            .await
+            .map_err(|_| SignTransactionError::KeyholderSend)?;
+
+        let signer = safe_signer::SafeSigner::from_memsafe(raw_key)?;
+
+        self.engine
+            .evaluate_transaction(wallet.id, client_id, transaction.clone(), RunKind::Execution)
+            .await?;
+
+        use alloy::network::TxSignerSync as _;
+        Ok(signer.sign_transaction_sync(&mut transaction)?)
+    }
+}

server/crates/arbiter-server/src/actors/keyholder/encryption.rs

@@ -0,0 +1 @@
+pub mod v1;

server/crates/arbiter-server/src/actors/keyholder/encryption/v1.rs

@@ -0,0 +1,237 @@
+use std::ops::Deref as _;
+
+use argon2::{Algorithm, Argon2, password_hash::Salt as ArgonSalt};
+use chacha20poly1305::{
+    AeadInPlace, Key, KeyInit as _, XChaCha20Poly1305, XNonce,
+    aead::{AeadMut, Error, Payload},
+};
+use memsafe::MemSafe;
+use rand::{
+    Rng as _, SeedableRng,
+    rngs::{StdRng, SysRng},
+};
+
+pub const ROOT_KEY_TAG: &[u8] = "arbiter/seal/v1".as_bytes();
+pub const TAG: &[u8] = "arbiter/private-key/v1".as_bytes();
+
+pub const NONCE_LENGTH: usize = 24;
+
+#[derive(Default)]
+pub struct Nonce([u8; NONCE_LENGTH]);
+impl Nonce {
+    pub fn increment(&mut self) {
+        for i in (0..self.0.len()).rev() {
+            if self.0[i] == 0xFF {
+                self.0[i] = 0;
+            } else {
+                self.0[i] += 1;
+                break;
+            }
+        }
+    }
+
+    pub fn to_vec(&self) -> Vec<u8> {
+        self.0.to_vec()
+    }
+}
+impl<'a> TryFrom<&'a [u8]> for Nonce {
+    type Error = ();
+
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.len() != NONCE_LENGTH {
+            return Err(());
+        }
+        let mut nonce = [0u8; NONCE_LENGTH];
+        nonce.copy_from_slice(value);
+        Ok(Self(nonce))
+    }
+}
+
+pub struct KeyCell(pub MemSafe<Key>);
+impl From<MemSafe<Key>> for KeyCell {
+    fn from(value: MemSafe<Key>) -> Self {
+        Self(value)
+    }
+}
+impl TryFrom<MemSafe<Vec<u8>>> for KeyCell {
+    type Error = ();
+
+    fn try_from(mut value: MemSafe<Vec<u8>>) -> Result<Self, Self::Error> {
+        let value = value.read().unwrap();
+        if value.len() != size_of::<Key>() {
+            return Err(());
+        }
+        let mut cell = MemSafe::new(Key::default()).unwrap();
+        {
+            let mut cell_write = cell.write().unwrap();
+            let cell_slice: &mut [u8] = cell_write.as_mut();
+            cell_slice.copy_from_slice(&value);
+        }
+        Ok(Self(cell))
+    }
+}
+
+impl KeyCell {
+    pub fn new_secure_random() -> Self {
+        let mut key = MemSafe::new(Key::default()).unwrap();
+        {
+            let mut key_buffer = key.write().unwrap();
+            let key_buffer: &mut [u8] = key_buffer.as_mut();
+
+            let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
+            rng.fill_bytes(key_buffer);
+        }
+
+        key.into()
+    }
+
+    pub fn encrypt_in_place(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        mut buffer: impl AsMut<Vec<u8>>,
+    ) -> Result<(), Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+        let buffer = buffer.as_mut();
+        cipher.encrypt_in_place(nonce, associated_data, buffer)
+    }
+    pub fn decrypt_in_place(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        buffer: &mut MemSafe<Vec<u8>>,
+    ) -> Result<(), Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+        let mut buffer = buffer.write().unwrap();
+        let buffer: &mut Vec<u8> = buffer.as_mut();
+        cipher.decrypt_in_place(nonce, associated_data, buffer)
+    }
+
+    pub fn encrypt(
+        &mut self,
+        nonce: &Nonce,
+        associated_data: &[u8],
+        plaintext: impl AsRef<[u8]>,
+    ) -> Result<Vec<u8>, Error> {
+        let key_reader = self.0.read().unwrap();
+        let key_ref = key_reader.deref();
+        let mut cipher = XChaCha20Poly1305::new(key_ref);
+        let nonce = XNonce::from_slice(nonce.0.as_ref());
+
+        let ciphertext = cipher.encrypt(
+            nonce,
+            Payload {
+                msg: plaintext.as_ref(),
+                aad: associated_data,
+            },
+        )?;
+        Ok(ciphertext)
+    }
+}
+
+pub type Salt = [u8; ArgonSalt::RECOMMENDED_LENGTH];
+
+pub fn generate_salt() -> Salt {
+    let mut salt = Salt::default();
+    let mut rng = StdRng::try_from_rng(&mut SysRng).unwrap();
+    rng.fill_bytes(&mut salt);
+    salt
+}
+
+/// User password might be of different length, have not enough entropy, etc...
+/// Derive a fixed-length key from the password using Argon2id, which is designed for password hashing and key derivation.
+pub fn derive_seal_key(mut password: MemSafe<Vec<u8>>, salt: &Salt) -> KeyCell {
+    let params = argon2::Params::new(262_144, 3, 4, None).unwrap();
+    let hasher = Argon2::new(Algorithm::Argon2id, argon2::Version::V0x13, params);
+    let mut key = MemSafe::new(Key::default()).unwrap();
+    {
+        let password_source = password.read().unwrap();
+        let mut key_buffer = key.write().unwrap();
+        let key_buffer: &mut [u8] = key_buffer.as_mut();
+
+        hasher
+            .hash_password_into(password_source.deref(), salt, key_buffer)
+            .unwrap();
+    }
+
+    key.into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use memsafe::MemSafe;
+
+    #[test]
+    pub fn derive_seal_key_deterministic() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let password2 = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key1 = derive_seal_key(password, &salt);
+        let mut key2 = derive_seal_key(password2, &salt);
+
+        let key1_reader = key1.0.read().unwrap();
+        let key2_reader = key2.0.read().unwrap();
+
+        assert_eq!(key1_reader.deref(), key2_reader.deref());
+    }
+
+    #[test]
+    pub fn successful_derive() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key = derive_seal_key(password, &salt);
+        let key_reader = key.0.read().unwrap();
+        let key_ref = key_reader.deref();
+
+        assert_ne!(key_ref.as_slice(), &[0u8; 32][..]);
+    }
+
+    #[test]
+    pub fn encrypt_decrypt() {
+        static PASSWORD: &[u8] = b"password";
+        let password = MemSafe::new(PASSWORD.to_vec()).unwrap();
+        let salt = generate_salt();
+
+        let mut key = derive_seal_key(password, &salt);
+        let nonce = Nonce(*b"unique nonce 123 1231233"); // 24 bytes for XChaCha20Poly1305
+        let associated_data = b"associated data";
+        let mut buffer = b"secret data".to_vec();
+
+        key.encrypt_in_place(&nonce, associated_data, &mut buffer)
+            .unwrap();
+        assert_ne!(buffer, b"secret data");
+
+        let mut buffer = MemSafe::new(buffer).unwrap();
+
+        key.decrypt_in_place(&nonce, associated_data, &mut buffer)
+            .unwrap();
+
+        let buffer = buffer.read().unwrap();
+        assert_eq!(*buffer, b"secret data");
+    }
+
+    #[test]
+    // We should fuzz this
+    pub fn test_nonce_increment() {
+        let mut nonce = Nonce([0u8; NONCE_LENGTH]);
+        nonce.increment();
+
+        assert_eq!(
+            nonce.0,
+            [
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1
+            ]
+        );
+    }
+}

server/crates/arbiter-server/src/actors/keyholder/mod.rs

@@ -0,0 +1,408 @@
+use chrono::Utc;
+use diesel::{
+    ExpressionMethods as _, OptionalExtension, QueryDsl, SelectableHelper,
+    dsl::{insert_into, update},
+};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+use kameo::{Actor, Reply, messages};
+use memsafe::MemSafe;
+use strum::{EnumDiscriminants, IntoDiscriminant};
+use tracing::{error, info};
+
+use crate::db::{
+    self,
+    models::{self, RootKeyHistory},
+    schema::{self},
+};
+use encryption::v1::{self, KeyCell, Nonce};
+
+pub mod encryption;
+
+#[derive(Default, EnumDiscriminants)]
+#[strum_discriminants(derive(Reply), vis(pub))]
+enum State {
+    #[default]
+    Unbootstrapped,
+    Sealed {
+        root_key_history_id: i32,
+    },
+    Unsealed {
+        root_key_history_id: i32,
+        root_key: KeyCell,
+    },
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum Error {
+    #[error("Keyholder is already bootstrapped")]
+    #[diagnostic(code(arbiter::keyholder::already_bootstrapped))]
+    AlreadyBootstrapped,
+    #[error("Keyholder is not bootstrapped")]
+    #[diagnostic(code(arbiter::keyholder::not_bootstrapped))]
+    NotBootstrapped,
+    #[error("Invalid key provided")]
+    #[diagnostic(code(arbiter::keyholder::invalid_key))]
+    InvalidKey,
+
+    #[error("Requested aead entry not found")]
+    #[diagnostic(code(arbiter::keyholder::aead_not_found))]
+    NotFound,
+
+    #[error("Encryption error: {0}")]
+    #[diagnostic(code(arbiter::keyholder::encryption_error))]
+    Encryption(#[from] chacha20poly1305::aead::Error),
+
+    #[error("Database error: {0}")]
+    #[diagnostic(code(arbiter::keyholder::database_error))]
+    DatabaseConnection(#[from] db::PoolError),
+
+    #[error("Database transaction error: {0}")]
+    #[diagnostic(code(arbiter::keyholder::database_transaction_error))]
+    DatabaseTransaction(#[from] diesel::result::Error),
+
+    #[error("Broken database")]
+    #[diagnostic(code(arbiter::keyholder::broken_database))]
+    BrokenDatabase,
+}
+
+/// Manages vault root key and tracks current state of the vault (bootstrapped/unbootstrapped, sealed/unsealed).
+/// Provides API for encrypting and decrypting data using the vault root key.
+/// Abstraction over database to make sure nonces are never reused and encryption keys are never exposed in plaintext outside of this actor.
+#[derive(Actor)]
+pub struct KeyHolder {
+    db: db::DatabasePool,
+    state: State,
+}
+
+#[messages]
+impl KeyHolder {
+    pub async fn new(db: db::DatabasePool) -> Result<Self, Error> {
+        let state = {
+            let mut conn = db.get().await?;
+
+            let (root_key_history,) = schema::arbiter_settings::table
+                .left_join(schema::root_key_history::table)
+                .select((Option::<RootKeyHistory>::as_select(),))
+                .get_result::<(Option<RootKeyHistory>,)>(&mut conn)
+                .await?;
+
+            match root_key_history {
+                Some(root_key_history) => State::Sealed {
+                    root_key_history_id: root_key_history.id,
+                },
+                None => State::Unbootstrapped,
+            }
+        };
+
+        Ok(Self { db, state })
+    }
+
+    // Exclusive transaction to avoid race condtions if multiple keyholders write
+    // additional layer of protection against nonce-reuse
+    async fn get_new_nonce(pool: &db::DatabasePool, root_key_id: i32) -> Result<Nonce, Error> {
+        let mut conn = pool.get().await?;
+
+        let nonce = conn
+            .exclusive_transaction(|conn| {
+                Box::pin(async move {
+                    let current_nonce: Vec<u8> = schema::root_key_history::table
+                        .filter(schema::root_key_history::id.eq(root_key_id))
+                        .select(schema::root_key_history::data_encryption_nonce)
+                        .first(conn)
+                        .await?;
+
+                    let mut nonce =
+                        v1::Nonce::try_from(current_nonce.as_slice()).map_err(|_| {
+                            error!(
+                                "Broken database: invalid nonce for root key history id={}",
+                                root_key_id
+                            );
+                            Error::BrokenDatabase
+                        })?;
+                    nonce.increment();
+
+                    update(schema::root_key_history::table)
+                        .filter(schema::root_key_history::id.eq(root_key_id))
+                        .set(schema::root_key_history::data_encryption_nonce.eq(nonce.to_vec()))
+                        .execute(conn)
+                        .await?;
+
+                    Result::<_, Error>::Ok(nonce)
+                })
+            })
+            .await?;
+
+        Ok(nonce)
+    }
+
+    #[message]
+    pub async fn bootstrap(&mut self, seal_key_raw: MemSafe<Vec<u8>>) -> Result<(), Error> {
+        if !matches!(self.state, State::Unbootstrapped) {
+            return Err(Error::AlreadyBootstrapped);
+        }
+        let salt = v1::generate_salt();
+        let mut seal_key = v1::derive_seal_key(seal_key_raw, &salt);
+        let mut root_key = KeyCell::new_secure_random();
+
+        // Zero nonces are fine because they are one-time
+        let root_key_nonce = v1::Nonce::default();
+        let data_encryption_nonce = v1::Nonce::default();
+
+        let root_key_ciphertext: Vec<u8> = {
+            let root_key_reader = root_key.0.read().unwrap();
+            let root_key_reader = root_key_reader.as_slice();
+            seal_key
+                .encrypt(&root_key_nonce, v1::ROOT_KEY_TAG, root_key_reader)
+                .map_err(|err| {
+                    error!(?err, "Fatal bootstrap error");
+                    Error::Encryption(err)
+                })?
+        };
+
+        let mut conn = self.db.get().await?;
+
+        let data_encryption_nonce_bytes = data_encryption_nonce.to_vec();
+        let root_key_history_id = conn
+            .transaction(|conn| {
+                Box::pin(async move {
+                    let root_key_history_id: i32 = insert_into(schema::root_key_history::table)
+                        .values(&models::NewRootKeyHistory {
+                            ciphertext: root_key_ciphertext,
+                            tag: v1::ROOT_KEY_TAG.to_vec(),
+                            root_key_encryption_nonce: root_key_nonce.to_vec(),
+                            data_encryption_nonce: data_encryption_nonce_bytes,
+                            schema_version: 1,
+                            salt: salt.to_vec(),
+                        })
+                        .returning(schema::root_key_history::id)
+                        .get_result(conn)
+                        .await?;
+
+                    update(schema::arbiter_settings::table)
+                        .set(schema::arbiter_settings::root_key_id.eq(root_key_history_id))
+                        .execute(conn)
+                        .await?;
+
+                    Result::<_, diesel::result::Error>::Ok(root_key_history_id)
+                })
+            })
+            .await?;
+
+        self.state = State::Unsealed {
+            root_key,
+            root_key_history_id,
+        };
+
+        info!("Keyholder bootstrapped successfully");
+
+        Ok(())
+    }
+
+    #[message]
+    pub async fn try_unseal(&mut self, seal_key_raw: MemSafe<Vec<u8>>) -> Result<(), Error> {
+        let State::Sealed {
+            root_key_history_id,
+        } = &self.state
+        else {
+            return Err(Error::NotBootstrapped);
+        };
+
+        // We don't want to hold connection while doing expensive KDF work
+        let current_key = {
+            let mut conn = self.db.get().await?;
+            schema::root_key_history::table
+                .filter(schema::root_key_history::id.eq(*root_key_history_id))
+                .select(schema::root_key_history::data_encryption_nonce)
+                .select(RootKeyHistory::as_select())
+                .first(&mut conn)
+                .await?
+        };
+
+        let salt = &current_key.salt;
+        let salt = v1::Salt::try_from(salt.as_slice()).map_err(|_| {
+            error!("Broken database: invalid salt for root key");
+            Error::BrokenDatabase
+        })?;
+        let mut seal_key = v1::derive_seal_key(seal_key_raw, &salt);
+
+        let mut root_key = MemSafe::new(current_key.ciphertext.clone()).unwrap();
+
+        let nonce = v1::Nonce::try_from(current_key.root_key_encryption_nonce.as_slice()).map_err(
+            |_| {
+                error!("Broken database: invalid nonce for root key");
+                Error::BrokenDatabase
+            },
+        )?;
+
+        seal_key
+            .decrypt_in_place(&nonce, v1::ROOT_KEY_TAG, &mut root_key)
+            .map_err(|err| {
+                error!(?err, "Failed to unseal root key: invalid seal key");
+                Error::InvalidKey
+            })?;
+
+        self.state = State::Unsealed {
+            root_key_history_id: current_key.id,
+            root_key: v1::KeyCell::try_from(root_key).map_err(|err| {
+                error!(?err, "Broken database: invalid encryption key size");
+                Error::BrokenDatabase
+            })?,
+        };
+
+        info!("Keyholder unsealed successfully");
+
+        Ok(())
+    }
+
+    // Decrypts the `aead_encrypted` entry with the given ID and returns the plaintext
+    #[message]
+    pub async fn decrypt(&mut self, aead_id: i32) -> Result<MemSafe<Vec<u8>>, Error> {
+        let State::Unsealed { root_key, .. } = &mut self.state else {
+            return Err(Error::NotBootstrapped);
+        };
+
+        let row: models::AeadEncrypted = {
+            let mut conn = self.db.get().await?;
+            schema::aead_encrypted::table
+                .select(models::AeadEncrypted::as_select())
+                .filter(schema::aead_encrypted::id.eq(aead_id))
+                .first(&mut conn)
+                .await
+                .optional()?
+                .ok_or(Error::NotFound)?
+        };
+
+        let nonce = v1::Nonce::try_from(row.current_nonce.as_slice()).map_err(|_| {
+            error!(
+                "Broken database: invalid nonce for aead_encrypted id={}",
+                aead_id
+            );
+            Error::BrokenDatabase
+        })?;
+        let mut output = MemSafe::new(row.ciphertext).unwrap();
+        root_key.decrypt_in_place(&nonce, v1::TAG, &mut output)?;
+        Ok(output)
+    }
+
+    // Creates new `aead_encrypted` entry in the database and returns it's ID
+    #[message]
+    pub async fn create_new(&mut self, mut plaintext: MemSafe<Vec<u8>>) -> Result<i32, Error> {
+        let State::Unsealed {
+            root_key,
+            root_key_history_id,
+        } = &mut self.state
+        else {
+            return Err(Error::NotBootstrapped);
+        };
+
+        // Order matters here - `get_new_nonce` acquires connection, so we need to call it before next acquire
+        // Borrow checker note: &mut borrow a few lines above is disjoint from this field
+        let nonce = Self::get_new_nonce(&self.db, *root_key_history_id).await?;
+
+        let mut ciphertext_buffer = plaintext.write().unwrap();
+        let ciphertext_buffer: &mut Vec<u8> = ciphertext_buffer.as_mut();
+        root_key.encrypt_in_place(&nonce, v1::TAG, &mut *ciphertext_buffer)?;
+
+        let ciphertext = std::mem::take(ciphertext_buffer);
+
+        let mut conn = self.db.get().await?;
+        let aead_id: i32 = insert_into(schema::aead_encrypted::table)
+            .values(&models::NewAeadEncrypted {
+                ciphertext,
+                tag: v1::TAG.to_vec(),
+                current_nonce: nonce.to_vec(),
+                schema_version: 1,
+                associated_root_key_id: *root_key_history_id,
+                created_at: Utc::now().into()
+            })
+            .returning(schema::aead_encrypted::id)
+            .get_result(&mut conn)
+            .await?;
+
+        Ok(aead_id)
+    }
+
+    #[message]
+    pub fn get_state(&self) -> StateDiscriminants {
+        self.state.discriminant()
+    }
+
+    #[message]
+    pub fn seal(&mut self) -> Result<(), Error> {
+        let State::Unsealed {
+            root_key_history_id,
+            ..
+        } = &self.state
+        else {
+            return Err(Error::NotBootstrapped);
+        };
+        self.state = State::Sealed {
+            root_key_history_id: *root_key_history_id,
+        };
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use diesel::SelectableHelper;
+    
+    use diesel_async::RunQueryDsl;
+    use memsafe::MemSafe;
+
+    use crate::db::{self};
+
+    use super::*;
+
+    async fn bootstrapped_actor(db: &db::DatabasePool) -> KeyHolder {
+        let mut actor = KeyHolder::new(db.clone()).await.unwrap();
+        let seal_key = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+        actor.bootstrap(seal_key).await.unwrap();
+        actor
+    }
+
+    #[tokio::test]
+    #[test_log::test]
+    async fn nonce_monotonic_even_when_nonce_allocation_interleaves() {
+        let db = db::create_test_pool().await;
+        let mut actor = bootstrapped_actor(&db).await;
+        let root_key_history_id = match actor.state {
+            State::Unsealed {
+                root_key_history_id,
+                ..
+            } => root_key_history_id,
+            _ => panic!("expected unsealed state"),
+        };
+
+        let n1 = KeyHolder::get_new_nonce(&db, root_key_history_id)
+            .await
+            .unwrap();
+        let n2 = KeyHolder::get_new_nonce(&db, root_key_history_id)
+            .await
+            .unwrap();
+        assert!(n2.to_vec() > n1.to_vec(), "nonce must increase");
+
+        let mut conn = db.get().await.unwrap();
+        let root_row: models::RootKeyHistory = schema::root_key_history::table
+            .select(models::RootKeyHistory::as_select())
+            .first(&mut conn)
+            .await
+            .unwrap();
+        assert_eq!(root_row.data_encryption_nonce, n2.to_vec());
+
+        let id = actor
+            .create_new(MemSafe::new(b"post-interleave".to_vec()).unwrap())
+            .await
+            .unwrap();
+        let row: models::AeadEncrypted = schema::aead_encrypted::table
+            .filter(schema::aead_encrypted::id.eq(id))
+            .select(models::AeadEncrypted::as_select())
+            .first(&mut conn)
+            .await
+            .unwrap();
+        assert!(
+            row.current_nonce > n2.to_vec(),
+            "next write must advance nonce"
+        );
+    }
+}

server/crates/arbiter-server/src/actors/mod.rs

@@ -0,0 +1,47 @@
+use kameo::actor::{ActorRef, Spawn};
+use miette::Diagnostic;
+use thiserror::Error;
+
+use crate::{
+    actors::{bootstrap::Bootstrapper, evm::EvmActor, keyholder::KeyHolder, router::MessageRouter},
+    db,
+};
+
+pub mod bootstrap;
+pub mod client;
+mod evm;
+pub mod keyholder;
+pub mod router;
+pub mod user_agent;
+
+#[derive(Error, Debug, Diagnostic)]
+pub enum SpawnError {
+    #[error("Failed to spawn Bootstrapper actor")]
+    #[diagnostic(code(SpawnError::Bootstrapper))]
+    Bootstrapper(#[from] bootstrap::Error),
+
+    #[error("Failed to spawn KeyHolder actor")]
+    #[diagnostic(code(SpawnError::KeyHolder))]
+    KeyHolder(#[from] keyholder::Error),
+}
+
+/// Long-lived actors that are shared across all connections and handle global state and operations
+#[derive(Clone)]
+pub struct GlobalActors {
+    pub key_holder: ActorRef<KeyHolder>,
+    pub bootstrapper: ActorRef<Bootstrapper>,
+    pub router: ActorRef<MessageRouter>,
+    pub evm: ActorRef<EvmActor>,
+}
+
+impl GlobalActors {
+    pub async fn spawn(db: db::DatabasePool) -> Result<Self, SpawnError> {
+        let key_holder = KeyHolder::spawn(KeyHolder::new(db.clone()).await?);
+        Ok(Self {
+            bootstrapper: Bootstrapper::spawn(Bootstrapper::new(&db).await?),
+            evm: EvmActor::spawn(EvmActor::new(key_holder.clone(), db)),
+            key_holder,
+            router: MessageRouter::spawn(MessageRouter::default()),
+        })
+    }
+}

server/crates/arbiter-server/src/actors/router/mod.rs

@@ -0,0 +1,76 @@
+use std::{collections::HashMap, ops::ControlFlow};
+
+use kameo::{
+    Actor,
+    actor::{ActorId, ActorRef},
+    messages,
+    prelude::{ActorStopReason, Context, WeakActorRef},
+};
+use tracing::info;
+
+use crate::actors::{client::session::ClientSession, user_agent::session::UserAgentSession};
+
+#[derive(Default)]
+pub struct MessageRouter {
+    pub user_agents: HashMap<ActorId, ActorRef<UserAgentSession>>,
+    pub clients: HashMap<ActorId, ActorRef<ClientSession>>,
+}
+
+impl Actor for MessageRouter {
+    type Args = Self;
+
+    type Error = ();
+
+    async fn on_start(args: Self::Args, _: ActorRef<Self>) -> Result<Self, Self::Error> {
+        Ok(args)
+    }
+
+    async fn on_link_died(
+        &mut self,
+        _: WeakActorRef<Self>,
+        id: ActorId,
+        _: ActorStopReason,
+    ) -> Result<ControlFlow<ActorStopReason>, Self::Error> {
+        if self.user_agents.remove(&id).is_some() {
+            info!(
+                ?id,
+                actor = "MessageRouter",
+                event = "useragent.disconnected"
+            );
+        } else if self.clients.remove(&id).is_some() {
+            info!(?id, actor = "MessageRouter", event = "client.disconnected");
+        } else {
+            info!(
+                ?id,
+                actor = "MessageRouter",
+                event = "unknown.actor.disconnected"
+            );
+        }
+        Ok(ControlFlow::Continue(()))
+    }
+}
+
+#[messages]
+impl MessageRouter {
+    #[message(ctx)]
+    pub async fn register_user_agent(
+        &mut self,
+        actor: ActorRef<UserAgentSession>,
+        ctx: &mut Context<Self, ()>,
+    ) {
+        info!(id = %actor.id(), actor = "MessageRouter", event = "useragent.connected");
+        ctx.actor_ref().link(&actor).await;
+        self.user_agents.insert(actor.id(), actor);
+    }
+
+    #[message(ctx)]
+    pub async fn register_client(
+        &mut self,
+        actor: ActorRef<ClientSession>,
+        ctx: &mut Context<Self, ()>,
+    ) {
+        info!(id = %actor.id(), actor = "MessageRouter", event = "client.connected");
+        ctx.actor_ref().link(&actor).await;
+        self.clients.insert(actor.id(), actor);
+    }
+}

server/crates/arbiter-server/src/actors/user_agent.rs

@@ -1,369 +0,0 @@
-use arbiter_proto::proto::{
-    UserAgentRequest, UserAgentResponse,
-    auth::{
-        self, AuthChallenge, AuthChallengeRequest, AuthOk, ClientMessage,
-        ServerMessage as AuthServerMessage, client_message::Payload as ClientAuthPayload,
-        server_message::Payload as ServerAuthPayload,
-    },
-    user_agent_request::Payload as UserAgentRequestPayload,
-    user_agent_response::Payload as UserAgentResponsePayload,
-};
-use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl, dsl::update};
-use diesel_async::{AsyncConnection, RunQueryDsl};
-use ed25519_dalek::VerifyingKey;
-use futures::StreamExt;
-use kameo::{
-    Actor,
-    actor::{ActorRef, Spawn},
-    error::SendError,
-    messages,
-    prelude::Context,
-};
-use tokio::sync::mpsc;
-use tokio::sync::mpsc::Sender;
-use tonic::Status;
-use tracing::{error, info};
-
-use crate::{
-    ServerContext,
-    context::bootstrap::{BootstrapActor, ConsumeToken},
-    db::{self, schema},
-    errors::GrpcStatusExt,
-};
-
-/// Context for state machine with validated key and sent challenge
-/// Challenge is then transformed to bytes using shared function and verified
-#[derive(Clone, Debug)]
-pub struct ChallengeContext {
-    challenge: AuthChallenge,
-    key: VerifyingKey,
-}
-
-// Request context with deserialized public key for state machine.
-// This intermediate struct is needed because the state machine branches depending on presence of bootstrap token,
-// but we want to have the deserialized key in both branches.
-#[derive(Clone, Debug)]
-pub struct AuthRequestContext {
-    pubkey: VerifyingKey,
-    bootstrap_token: Option<String>,
-}
-
-smlang::statemachine!(
-    name: UserAgent,
-    derive_states: [Debug],
-    custom_error: false,
-    transitions: {
-        *Init + AuthRequest(AuthRequestContext) / auth_request_context =  ReceivedAuthRequest(AuthRequestContext),
-        ReceivedAuthRequest(AuthRequestContext) + ReceivedBootstrapToken = Authenticated,
-
-        ReceivedAuthRequest(AuthRequestContext) + SentChallenge(ChallengeContext) / move_challenge = WaitingForChallengeSolution(ChallengeContext),
-
-        WaitingForChallengeSolution(ChallengeContext) + ReceivedGoodSolution = Authenticated,
-        WaitingForChallengeSolution(ChallengeContext) + ReceivedBadSolution = AuthError, // block further transitions, but connection should close anyway
-    }
-);
-
-pub struct DummyContext;
-impl UserAgentStateMachineContext for DummyContext {
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    fn move_challenge(
-        &mut self,
-        state_data: &AuthRequestContext,
-        event_data: ChallengeContext,
-    ) -> Result<ChallengeContext, ()> {
-        Ok(event_data)
-    }
-
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    fn auth_request_context(
-        &mut self,
-        event_data: AuthRequestContext,
-    ) -> Result<AuthRequestContext, ()> {
-        Ok(event_data)
-    }
-}
-
-#[derive(Actor)]
-pub struct UserAgentActor {
-    db: db::DatabasePool,
-    bootstapper: ActorRef<BootstrapActor>,
-    state: UserAgentStateMachine<DummyContext>,
-    tx: Sender<Result<UserAgentResponse, Status>>,
-}
-
-impl UserAgentActor {
-    pub(crate) fn new(
-        context: ServerContext,
-        tx: Sender<Result<UserAgentResponse, Status>>,
-    ) -> Self {
-        Self {
-            db: context.db.clone(),
-            bootstapper: context.bootstrapper.clone(),
-            state: UserAgentStateMachine::new(DummyContext),
-            tx,
-        }
-    }
-
-    pub(crate) fn new_manual(
-        db: db::DatabasePool,
-        bootstapper: ActorRef<BootstrapActor>,
-        tx: Sender<Result<UserAgentResponse, Status>>,
-    ) -> Self {
-        Self {
-            db,
-            bootstapper,
-            state: UserAgentStateMachine::new(DummyContext),
-            tx,
-        }
-    }
-
-    fn transition(&mut self, event: UserAgentEvents) -> Result<(), Status> {
-        self.state.process_event(event).map_err(|e| {
-            error!(?e, "State transition failed");
-            Status::internal("State machine error")
-        })?;
-        Ok(())
-    }
-
-    async fn auth_with_bootstrap_token(
-        &mut self,
-        pubkey: ed25519_dalek::VerifyingKey,
-        token: String,
-    ) -> Result<UserAgentResponse, Status> {
-        let token_ok: bool = self
-            .bootstapper
-            .ask(ConsumeToken { token })
-            .await
-            .map_err(|e| {
-                error!(?pubkey, "Failed to consume bootstrap token: {e}");
-                Status::internal("Bootstrap token consumption failed")
-            })?;
-
-        if !token_ok {
-            error!(?pubkey, "Invalid bootstrap token provided");
-            return Err(Status::invalid_argument("Invalid bootstrap token"));
-        }
-
-        {
-            let mut conn = self.db.get().await.to_status()?;
-
-            diesel::insert_into(schema::useragent_client::table)
-                .values((
-                    schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                    schema::useragent_client::nonce.eq(1),
-                ))
-                .execute(&mut conn)
-                .await
-                .to_status()?;
-        }
-
-        self.transition(UserAgentEvents::ReceivedBootstrapToken)?;
-
-        Ok(auth_response(ServerAuthPayload::AuthOk(AuthOk {})))
-    }
-
-    async fn auth_with_challenge(&mut self, pubkey: VerifyingKey, pubkey_bytes: Vec<u8>) -> Output {
-        let nonce: Option<i32> = {
-            let mut db_conn = self.db.get().await.to_status()?;
-            db_conn
-                .transaction(|conn| {
-                    Box::pin(async move {
-                        let current_nonce = schema::useragent_client::table
-                            .filter(
-                                schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                            )
-                            .select(schema::useragent_client::nonce)
-                            .first::<i32>(conn)
-                            .await?;
-
-                        update(schema::useragent_client::table)
-                            .filter(
-                                schema::useragent_client::public_key.eq(pubkey.as_bytes().to_vec()),
-                            )
-                            .set(schema::useragent_client::nonce.eq(current_nonce + 1))
-                            .execute(conn)
-                            .await?;
-
-                        Result::<_, diesel::result::Error>::Ok(current_nonce)
-                    })
-                })
-                .await
-                .optional()
-                .to_status()?
-        };
-
-        let Some(nonce) = nonce else {
-            error!(?pubkey, "Public key not found in database");
-            return Err(Status::unauthenticated("Public key not registered"));
-        };
-
-        let challenge = auth::AuthChallenge {
-            pubkey: pubkey_bytes,
-            nonce: nonce,
-        };
-
-        self.transition(UserAgentEvents::SentChallenge(ChallengeContext {
-            challenge: challenge.clone(),
-            key: pubkey,
-        }))?;
-
-        info!(
-            ?pubkey,
-            ?challenge,
-            "Sent authentication challenge to client"
-        );
-
-        Ok(auth_response(ServerAuthPayload::AuthChallenge(challenge)))
-    }
-
-    fn verify_challenge_solution(
-        &self,
-        solution: &auth::AuthChallengeSolution,
-    ) -> Result<(bool, &ChallengeContext), Status> {
-        let UserAgentStates::WaitingForChallengeSolution(challenge_context) = self.state.state()
-        else {
-            error!("Received challenge solution in invalid state");
-            return Err(Status::invalid_argument(
-                "Invalid state for challenge solution",
-            ));
-        };
-        let formatted_challenge = arbiter_proto::format_challenge(&challenge_context.challenge);
-
-        let signature = solution.signature.as_slice().try_into().map_err(|_| {
-            error!(?solution, "Invalid signature length");
-            Status::invalid_argument("Invalid signature length")
-        })?;
-
-        let valid = challenge_context
-            .key
-            .verify_strict(&formatted_challenge, &signature)
-            .is_ok();
-
-        Ok((valid, challenge_context))
-    }
-}
-
-type Output = Result<UserAgentResponse, Status>;
-
-fn auth_response(payload: ServerAuthPayload) -> UserAgentResponse {
-    UserAgentResponse {
-        payload: Some(UserAgentResponsePayload::AuthMessage(AuthServerMessage {
-            payload: Some(payload),
-        })),
-    }
-}
-
-#[messages]
-impl UserAgentActor {
-    #[message(ctx)]
-    pub async fn handle_auth_challenge_request(
-        &mut self,
-        req: AuthChallengeRequest,
-        ctx: &mut Context<Self, Output>,
-    ) -> Output {
-        let pubkey = req.pubkey.as_array().ok_or(Status::invalid_argument(
-            "Expected pubkey to have specific length",
-        ))?;
-        let pubkey = VerifyingKey::from_bytes(pubkey).map_err(|err| {
-            error!(?pubkey, "Failed to convert to VerifyingKey");
-            Status::invalid_argument("Failed to convert pubkey to VerifyingKey")
-        })?;
-
-        self.transition(UserAgentEvents::AuthRequest(AuthRequestContext {
-            pubkey,
-            bootstrap_token: req.bootstrap_token.clone(),
-        }))?;
-
-        match req.bootstrap_token {
-            Some(token) => self.auth_with_bootstrap_token(pubkey, token).await,
-            None => self.auth_with_challenge(pubkey, req.pubkey).await,
-        }
-    }
-
-    #[message(ctx)]
-    pub async fn handle_auth_challenge_solution(
-        &mut self,
-        solution: auth::AuthChallengeSolution,
-        ctx: &mut Context<Self, Output>,
-    ) -> Output {
-        let (valid, challenge_context) = self.verify_challenge_solution(&solution)?;
-
-        if valid {
-            info!(
-                ?challenge_context,
-                "Client provided valid solution to authentication challenge"
-            );
-            self.transition(UserAgentEvents::ReceivedGoodSolution)?;
-            Ok(auth_response(ServerAuthPayload::AuthOk(AuthOk {})))
-        } else {
-            error!("Client provided invalid solution to authentication challenge");
-            self.transition(UserAgentEvents::ReceivedBadSolution)?;
-            Err(Status::unauthenticated("Invalid challenge solution"))
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use arbiter_proto::proto::{
-        UserAgentResponse, auth::{AuthChallengeRequest, AuthOk},
-        user_agent_response::Payload as UserAgentResponsePayload,
-    };
-    use kameo::actor::Spawn;
-
-    use crate::{
-        actors::user_agent::HandleAuthChallengeRequest, context::bootstrap::BootstrapActor, db,
-    };
-
-    use super::UserAgentActor;
-
-    #[tokio::test]
-    #[test_log::test]
-    pub async fn test_bootstrap_token_auth() {
-        let db = db::create_test_pool().await;
-        // explicitly not installing any user_agent pubkeys
-        let bootstrapper = BootstrapActor::new(&db).await.unwrap(); // this will create bootstrap token
-        let token = bootstrapper.get_token().unwrap();
-
-        let bootstrapper_ref = BootstrapActor::spawn(bootstrapper);
-        let user_agent = UserAgentActor::new_manual(
-            db.clone(),
-            bootstrapper_ref,
-            tokio::sync::mpsc::channel(1).0, // dummy channel, we won't actually send responses in this test
-        );
-        let user_agent_ref = UserAgentActor::spawn(user_agent);
-
-        // simulate client sending auth request with bootstrap token
-        let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
-        let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
-
-        let result = user_agent_ref
-            .ask(HandleAuthChallengeRequest {
-                req: AuthChallengeRequest {
-                    pubkey: pubkey_bytes,
-                    bootstrap_token: Some(token),
-                },
-            })
-            .await
-            .expect("Shouldn't fail to send message");
-        
-        // auth succeeded
-        assert_eq!(
-            result,
-            UserAgentResponse {
-                payload: Some(UserAgentResponsePayload::AuthMessage(
-                    arbiter_proto::proto::auth::ServerMessage {
-                        payload: Some(arbiter_proto::proto::auth::server_message::Payload::AuthOk(
-                            AuthOk {},
-                        )),
-                    },
-                )),
-            }
-        );
-    }
-}
-
-mod transport;
-pub(crate) use transport::handle_user_agent;

server/crates/arbiter-server/src/actors/user_agent/auth.rs

@@ -0,0 +1,141 @@
+use arbiter_proto::proto::user_agent::{
+    AuthChallengeRequest, AuthChallengeSolution, KeyType as ProtoKeyType, UserAgentRequest,
+    user_agent_request::Payload as UserAgentRequestPayload,
+};
+use tracing::error;
+
+use crate::actors::user_agent::{
+    UserAgentConnection,
+    auth::state::{AuthContext, AuthPublicKey, AuthStateMachine},
+    session::UserAgentSession,
+};
+
+#[derive(thiserror::Error, Debug, PartialEq)]
+pub enum Error {
+    #[error("Unexpected message payload")]
+    UnexpectedMessagePayload,
+    #[error("Invalid client public key length")]
+    InvalidClientPubkeyLength,
+    #[error("Invalid client public key encoding")]
+    InvalidAuthPubkeyEncoding,
+    #[error("Database pool unavailable")]
+    DatabasePoolUnavailable,
+    #[error("Database operation failed")]
+    DatabaseOperationFailed,
+    #[error("Public key not registered")]
+    PublicKeyNotRegistered,
+    #[error("Transport error")]
+    Transport,
+    #[error("Invalid bootstrap token")]
+    InvalidBootstrapToken,
+    #[error("Bootstrapper actor unreachable")]
+    BootstrapperActorUnreachable,
+    #[error("Invalid challenge solution")]
+    InvalidChallengeSolution,
+}
+
+mod state;
+use state::*;
+
+fn parse_pubkey(key_type: ProtoKeyType, pubkey: Vec<u8>) -> Result<AuthPublicKey, Error> {
+    match key_type {
+        // UNSPECIFIED treated as Ed25519 for backward compatibility
+        ProtoKeyType::Unspecified | ProtoKeyType::Ed25519 => {
+            let pubkey_bytes = pubkey.as_array().ok_or(Error::InvalidClientPubkeyLength)?;
+            let key = ed25519_dalek::VerifyingKey::from_bytes(pubkey_bytes)
+                .map_err(|_| Error::InvalidAuthPubkeyEncoding)?;
+            Ok(AuthPublicKey::Ed25519(key))
+        }
+        ProtoKeyType::EcdsaSecp256k1 => {
+            // Public key is sent as 33-byte SEC1 compressed point
+            let key = k256::ecdsa::VerifyingKey::from_sec1_bytes(&pubkey)
+                .map_err(|_| Error::InvalidAuthPubkeyEncoding)?;
+            Ok(AuthPublicKey::EcdsaSecp256k1(key))
+        }
+        ProtoKeyType::Rsa => {
+            use rsa::pkcs8::DecodePublicKey as _;
+            let key = rsa::RsaPublicKey::from_public_key_der(&pubkey)
+                .map_err(|_| Error::InvalidAuthPubkeyEncoding)?;
+            Ok(AuthPublicKey::Rsa(key))
+        }
+    }
+}
+
+fn parse_auth_event(payload: UserAgentRequestPayload) -> Result<AuthEvents, Error> {
+    match payload {
+        UserAgentRequestPayload::AuthChallengeRequest(AuthChallengeRequest {
+            pubkey,
+            bootstrap_token: None,
+            key_type,
+        }) => {
+            let kt = ProtoKeyType::try_from(key_type).unwrap_or(ProtoKeyType::Unspecified);
+            Ok(AuthEvents::AuthRequest(ChallengeRequest {
+                pubkey: parse_pubkey(kt, pubkey)?,
+            }))
+        }
+        UserAgentRequestPayload::AuthChallengeRequest(AuthChallengeRequest {
+            pubkey,
+            bootstrap_token: Some(token),
+            key_type,
+        }) => {
+            let kt = ProtoKeyType::try_from(key_type).unwrap_or(ProtoKeyType::Unspecified);
+            Ok(AuthEvents::BootstrapAuthRequest(BootstrapAuthRequest {
+                pubkey: parse_pubkey(kt, pubkey)?,
+                token,
+            }))
+        }
+        UserAgentRequestPayload::AuthChallengeSolution(AuthChallengeSolution { signature }) => {
+            Ok(AuthEvents::ReceivedSolution(ChallengeSolution {
+                solution: signature,
+            }))
+        }
+        _ => Err(Error::UnexpectedMessagePayload),
+    }
+}
+
+pub async fn authenticate(props: &mut UserAgentConnection) -> Result<AuthPublicKey, Error> {
+    let mut state = AuthStateMachine::new(AuthContext::new(props));
+
+    loop {
+        // `state` holds a mutable reference to `props` so we can't access it directly here
+        let transport = state.context_mut().conn.transport.as_mut();
+        let Some(UserAgentRequest {
+            payload: Some(payload),
+        }) = transport.recv().await
+        else {
+            return Err(Error::Transport);
+        };
+
+        let event = parse_auth_event(payload)?;
+
+        match state.process_event(event).await {
+            Ok(AuthStates::AuthOk(key)) => return Ok(key.clone()),
+            Err(AuthError::ActionFailed(err)) => {
+                error!(?err, "State machine action failed");
+                return Err(err);
+            }
+            Err(AuthError::GuardFailed(err)) => {
+                error!(?err, "State machine guard failed");
+                return Err(err);
+            }
+            Err(AuthError::InvalidEvent) => {
+                error!("Invalid event for current state");
+                return Err(Error::InvalidChallengeSolution);
+            }
+            Err(AuthError::TransitionsFailed) => {
+                error!("Invalid state transition");
+                return Err(Error::InvalidChallengeSolution);
+            }
+
+            _ => (),
+        }
+    }
+}
+
+pub async fn authenticate_and_create(
+    mut props: UserAgentConnection,
+) -> Result<UserAgentSession, Error> {
+    let _key = authenticate(&mut props).await?;
+    let session = UserAgentSession::new(props);
+    Ok(session)
+}

server/crates/arbiter-server/src/actors/user_agent/auth/state.rs

@@ -0,0 +1,297 @@
+use arbiter_proto::proto::user_agent::{
+    AuthChallenge, UserAgentResponse, user_agent_response::Payload as UserAgentResponsePayload,
+};
+use diesel::{ExpressionMethods as _, OptionalExtension as _, QueryDsl, update};
+use diesel_async::RunQueryDsl;
+use tracing::error;
+
+use super::Error;
+use crate::{
+    actors::{bootstrap::ConsumeToken, user_agent::UserAgentConnection},
+    db::{models::KeyType, schema},
+};
+
+/// Abstraction over Ed25519 / ECDSA-secp256k1 / RSA public keys used during the auth handshake.
+#[derive(Clone)]
+pub enum AuthPublicKey {
+    Ed25519(ed25519_dalek::VerifyingKey),
+    /// Compressed SEC1 public key; signature bytes are raw 64-byte (r||s).
+    EcdsaSecp256k1(k256::ecdsa::VerifyingKey),
+    /// RSA-2048+ public key (Windows Hello / KeyCredentialManager); signature bytes are PSS+SHA-256.
+    Rsa(rsa::RsaPublicKey),
+}
+
+impl AuthPublicKey {
+    /// Canonical bytes stored in DB and echoed back in the challenge.
+    /// Ed25519: raw 32 bytes. ECDSA: SEC1 compressed 33 bytes. RSA: DER-encoded SPKI.
+    pub fn to_stored_bytes(&self) -> Vec<u8> {
+        match self {
+            AuthPublicKey::Ed25519(k) => k.to_bytes().to_vec(),
+            // SEC1 compressed (33 bytes) is the natural compact format for secp256k1
+            AuthPublicKey::EcdsaSecp256k1(k) => k.to_encoded_point(true).as_bytes().to_vec(),
+            AuthPublicKey::Rsa(k) => {
+                use rsa::pkcs8::EncodePublicKey as _;
+                k.to_public_key_der()
+                    .expect("rsa SPKI encoding is infallible")
+                    .to_vec()
+            }
+        }
+    }
+
+    pub fn key_type(&self) -> KeyType {
+        match self {
+            AuthPublicKey::Ed25519(_) => KeyType::Ed25519,
+            AuthPublicKey::EcdsaSecp256k1(_) => KeyType::EcdsaSecp256k1,
+            AuthPublicKey::Rsa(_) => KeyType::Rsa,
+        }
+    }
+}
+
+pub struct ChallengeRequest {
+    pub pubkey: AuthPublicKey,
+}
+
+pub struct BootstrapAuthRequest {
+    pub pubkey: AuthPublicKey,
+    pub token: String,
+}
+
+pub struct ChallengeContext {
+    pub challenge: AuthChallenge,
+    pub key: AuthPublicKey,
+}
+
+pub struct ChallengeSolution {
+    pub solution: Vec<u8>,
+}
+
+smlang::statemachine!(
+    name: Auth,
+    custom_error: true,
+    transitions: {
+        *Init + AuthRequest(ChallengeRequest) / async prepare_challenge = SentChallenge(ChallengeContext),
+        Init + BootstrapAuthRequest(BootstrapAuthRequest) [async verify_bootstrap_token] / provide_key_bootstrap = AuthOk(AuthPublicKey),
+        SentChallenge(ChallengeContext) + ReceivedSolution(ChallengeSolution) [async verify_solution] / provide_key = AuthOk(AuthPublicKey),
+    }
+);
+
+async fn create_nonce(db: &crate::db::DatabasePool, pubkey_bytes: &[u8]) -> Result<i32, Error> {
+    let mut db_conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+    db_conn
+        .exclusive_transaction(|conn| {
+            Box::pin(async move {
+                let current_nonce = schema::useragent_client::table
+                    .filter(schema::useragent_client::public_key.eq(pubkey_bytes.to_vec()))
+                    .select(schema::useragent_client::nonce)
+                    .first::<i32>(conn)
+                    .await?;
+
+                update(schema::useragent_client::table)
+                    .filter(schema::useragent_client::public_key.eq(pubkey_bytes.to_vec()))
+                    .set(schema::useragent_client::nonce.eq(current_nonce + 1))
+                    .execute(conn)
+                    .await?;
+
+                Result::<_, diesel::result::Error>::Ok(current_nonce)
+            })
+        })
+        .await
+        .optional()
+        .map_err(|e| {
+            error!(error = ?e, "Database error");
+            Error::DatabaseOperationFailed
+        })?
+        .ok_or_else(|| {
+            error!(?pubkey_bytes, "Public key not found in database");
+            Error::PublicKeyNotRegistered
+        })
+}
+
+async fn register_key(db: &crate::db::DatabasePool, pubkey: &AuthPublicKey) -> Result<(), Error> {
+    let pubkey_bytes = pubkey.to_stored_bytes();
+    let key_type = pubkey.key_type();
+    let mut conn = db.get().await.map_err(|e| {
+        error!(error = ?e, "Database pool error");
+        Error::DatabasePoolUnavailable
+    })?;
+
+    diesel::insert_into(schema::useragent_client::table)
+        .values((
+            schema::useragent_client::public_key.eq(pubkey_bytes),
+            schema::useragent_client::nonce.eq(1),
+            schema::useragent_client::key_type.eq(key_type),
+        ))
+        .execute(&mut conn)
+        .await
+        .map_err(|e| {
+            error!(error = ?e, "Database error");
+            Error::DatabaseOperationFailed
+        })?;
+
+    Ok(())
+}
+
+pub struct AuthContext<'a> {
+    pub(super) conn: &'a mut UserAgentConnection,
+}
+
+impl<'a> AuthContext<'a> {
+    pub fn new(conn: &'a mut UserAgentConnection) -> Self {
+        Self { conn }
+    }
+}
+
+impl AuthStateMachineContext for AuthContext<'_> {
+    type Error = Error;
+
+    async fn verify_solution(
+        &self,
+        ChallengeContext { challenge, key }: &ChallengeContext,
+        ChallengeSolution { solution }: &ChallengeSolution,
+    ) -> Result<bool, Self::Error> {
+        let formatted = arbiter_proto::format_challenge(challenge.nonce, &challenge.pubkey);
+
+        let valid = match key {
+            AuthPublicKey::Ed25519(vk) => {
+                let sig = solution.as_slice().try_into().map_err(|_| {
+                    error!(?solution, "Invalid Ed25519 signature length");
+                    Error::InvalidChallengeSolution
+                })?;
+                vk.verify_strict(&formatted, &sig).is_ok()
+            }
+            AuthPublicKey::EcdsaSecp256k1(vk) => {
+                use k256::ecdsa::signature::Verifier as _;
+                let sig = k256::ecdsa::Signature::try_from(solution.as_slice()).map_err(|_| {
+                    error!(?solution, "Invalid ECDSA signature bytes");
+                    Error::InvalidChallengeSolution
+                })?;
+                vk.verify(&formatted, &sig).is_ok()
+            }
+            AuthPublicKey::Rsa(pk) => {
+                use rsa::signature::Verifier as _;
+                let verifying_key = rsa::pss::VerifyingKey::<sha2::Sha256>::new(pk.clone());
+                let sig = rsa::pss::Signature::try_from(solution.as_slice()).map_err(|_| {
+                    error!(?solution, "Invalid RSA signature bytes");
+                    Error::InvalidChallengeSolution
+                })?;
+                verifying_key.verify(&formatted, &sig).is_ok()
+            }
+        };
+
+        Ok(valid)
+    }
+
+    async fn prepare_challenge(
+        &mut self,
+        ChallengeRequest { pubkey }: ChallengeRequest,
+    ) -> Result<ChallengeContext, Self::Error> {
+        let stored_bytes = pubkey.to_stored_bytes();
+        let nonce = create_nonce(&self.conn.db, &stored_bytes).await?;
+
+        let challenge = AuthChallenge {
+            pubkey: stored_bytes,
+            nonce,
+        };
+
+        self.conn
+            .transport
+            .send(Ok(UserAgentResponse {
+                payload: Some(UserAgentResponsePayload::AuthChallenge(challenge.clone())),
+            }))
+            .await
+            .map_err(|e| {
+                error!(?e, "Failed to send auth challenge");
+                Error::Transport
+            })?;
+
+        Ok(ChallengeContext {
+            challenge,
+            key: pubkey,
+        })
+    }
+
+    #[allow(missing_docs)]
+    #[allow(clippy::result_unit_err)]
+    async fn verify_bootstrap_token(
+        &self,
+        BootstrapAuthRequest { pubkey, token }: &BootstrapAuthRequest,
+    ) -> Result<bool, Self::Error> {
+        let token_ok: bool = self
+            .conn
+            .actors
+            .bootstrapper
+            .ask(ConsumeToken {
+                token: token.clone(),
+            })
+            .await
+            .map_err(|e| {
+                error!(?e, "Failed to consume bootstrap token");
+                Error::BootstrapperActorUnreachable
+            })?;
+
+        if !token_ok {
+            error!("Invalid bootstrap token provided");
+            return Err(Error::InvalidBootstrapToken);
+        }
+
+        register_key(&self.conn.db, pubkey).await?;
+
+        Ok(true)
+    }
+
+    fn provide_key_bootstrap(
+        &mut self,
+        event_data: BootstrapAuthRequest,
+    ) -> Result<AuthPublicKey, Self::Error> {
+        Ok(event_data.pubkey)
+    }
+
+    fn provide_key(
+        &mut self,
+        state_data: &ChallengeContext,
+        _: ChallengeSolution,
+    ) -> Result<AuthPublicKey, Self::Error> {
+        // ChallengeContext.key cannot be taken by value because smlang passes it by ref;
+        // we reconstruct stored bytes and return them wrapped in Ed25519 placeholder.
+        // Session uses only the raw bytes, so we carry them via a Vec<u8>.
+        // IMPORTANT: do NOT simplify this by storing the key type separately — the
+        // `AuthPublicKey` enum IS the source of truth for key bytes and type.
+        //
+        // smlang state-machine trait requires returning an owned value from `provide_key`,
+        // but `state_data` is only available by shared reference here.  We extract the
+        // stored bytes and re-wrap as the correct variant so the caller can call
+        // `to_stored_bytes()` / `key_type()` without losing information.
+        let bytes = state_data.challenge.pubkey.clone();
+        let key_type = state_data.key.key_type();
+        let rebuilt = match key_type {
+            crate::db::models::KeyType::Ed25519 => {
+                let arr: &[u8; 32] = bytes
+                    .as_slice()
+                    .try_into()
+                    .expect("ed25519 pubkey must be 32 bytes in challenge");
+                AuthPublicKey::Ed25519(
+                    ed25519_dalek::VerifyingKey::from_bytes(arr)
+                        .expect("key was already validated in parse_auth_event"),
+                )
+            }
+            crate::db::models::KeyType::EcdsaSecp256k1 => {
+                // bytes are SEC1 compressed (33 bytes produced by to_encoded_point(true))
+                AuthPublicKey::EcdsaSecp256k1(
+                    k256::ecdsa::VerifyingKey::from_sec1_bytes(&bytes)
+                        .expect("ecdsa key was already validated in parse_auth_event"),
+                )
+            }
+            crate::db::models::KeyType::Rsa => {
+                use rsa::pkcs8::DecodePublicKey as _;
+                AuthPublicKey::Rsa(
+                    rsa::RsaPublicKey::from_public_key_der(&bytes)
+                        .expect("rsa key was already validated in parse_auth_event"),
+                )
+            }
+        };
+        Ok(rebuilt)
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/mod.rs

@@ -0,0 +1,65 @@
+use arbiter_proto::{
+    proto::user_agent::{UserAgentRequest, UserAgentResponse},
+    transport::Bi,
+};
+use kameo::actor::Spawn as _;
+use tracing::{error, info};
+
+use crate::{
+    actors::{GlobalActors, user_agent::session::UserAgentSession},
+    db::{self},
+};
+
+#[derive(Debug, thiserror::Error, PartialEq)]
+pub enum TransportResponseError {
+    #[error("Expected message with payload")]
+    MissingRequestPayload,
+    #[error("Unexpected request payload")]
+    UnexpectedRequestPayload,
+    #[error("Invalid state for unseal encrypted key")]
+    InvalidStateForUnsealEncryptedKey,
+    #[error("client_pubkey must be 32 bytes")]
+    InvalidClientPubkeyLength,
+    #[error("State machine error")]
+    StateTransitionFailed,
+    #[error("Vault is not available")]
+    KeyHolderActorUnreachable,
+    #[error(transparent)]
+    Auth(#[from] auth::Error),
+    #[error("Failed registering connection")]
+    ConnectionRegistrationFailed,
+}
+
+pub type Transport =
+    Box<dyn Bi<UserAgentRequest, Result<UserAgentResponse, TransportResponseError>> + Send>;
+
+pub struct UserAgentConnection {
+    db: db::DatabasePool,
+    actors: GlobalActors,
+    transport: Transport,
+}
+
+impl UserAgentConnection {
+    pub fn new(db: db::DatabasePool, actors: GlobalActors, transport: Transport) -> Self {
+        Self {
+            db,
+            actors,
+            transport,
+        }
+    }
+}
+
+pub mod auth;
+pub mod session;
+
+pub async fn connect_user_agent(props: UserAgentConnection) {
+    match auth::authenticate_and_create(props).await {
+        Ok(session) => {
+            UserAgentSession::spawn(session);
+            info!("User authenticated, session started");
+        }
+        Err(err) => {
+            error!(?err, "Authentication failed, closing connection");
+        }
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/session.rs

@@ -0,0 +1,587 @@
+use std::{ops::DerefMut, sync::Mutex};
+
+use arbiter_proto::proto::{
+    evm as evm_proto,
+    user_agent::{
+        SdkClientApproveRequest, SdkClientApproveResponse, SdkClientEntry,
+        SdkClientError as ProtoSdkClientError, SdkClientList, SdkClientListResponse,
+        SdkClientRevokeRequest, SdkClientRevokeResponse, UnsealEncryptedKey, UnsealResult,
+        UnsealStart, UnsealStartResponse, UserAgentRequest, UserAgentResponse,
+        sdk_client_approve_response, sdk_client_list_response, sdk_client_revoke_response,
+        user_agent_request::Payload as UserAgentRequestPayload,
+        user_agent_response::Payload as UserAgentResponsePayload,
+    },
+};
+use chacha20poly1305::{AeadInPlace, XChaCha20Poly1305, XNonce, aead::KeyInit};
+use diesel::{ExpressionMethods as _, QueryDsl as _, dsl::insert_into};
+use diesel_async::RunQueryDsl as _;
+use kameo::{Actor, error::SendError, prelude::Context};
+use memsafe::MemSafe;
+use tokio::select;
+use tracing::{error, info};
+use x25519_dalek::{EphemeralSecret, PublicKey};
+
+use crate::{
+    actors::{
+        evm::{Generate, ListWallets},
+        keyholder::{self, TryUnseal},
+        router::RegisterUserAgent,
+        user_agent::{TransportResponseError, UserAgentConnection},
+    },
+    db::schema::program_client,
+};
+
+mod state;
+use state::{DummyContext, UnsealContext, UserAgentEvents, UserAgentStateMachine, UserAgentStates};
+
+// Error for consumption by other actors
+#[derive(Debug, thiserror::Error, PartialEq)]
+pub enum Error {
+    #[error("User agent session ended due to connection loss")]
+    ConnectionLost,
+
+    #[error("User agent session ended due to unexpected message")]
+    UnexpectedMessage,
+}
+
+pub struct UserAgentSession {
+    props: UserAgentConnection,
+    state: UserAgentStateMachine<DummyContext>,
+}
+
+impl UserAgentSession {
+    pub(crate) fn new(props: UserAgentConnection) -> Self {
+        Self {
+            props,
+            state: UserAgentStateMachine::new(DummyContext),
+        }
+    }
+
+    fn transition(&mut self, event: UserAgentEvents) -> Result<(), TransportResponseError> {
+        self.state.process_event(event).map_err(|e| {
+            error!(?e, "State transition failed");
+            TransportResponseError::StateTransitionFailed
+        })?;
+        Ok(())
+    }
+
+    async fn send_msg<Reply: kameo::Reply>(
+        &mut self,
+        msg: UserAgentResponsePayload,
+        _ctx: &mut Context<Self, Reply>,
+    ) -> Result<(), Error> {
+        self.props
+            .transport
+            .send(Ok(response(msg)))
+            .await
+            .map_err(|_| {
+                error!(
+                    actor = "useragent",
+                    reason = "channel closed",
+                    "send.failed"
+                );
+                Error::ConnectionLost
+            })
+    }
+
+    async fn expect_msg<Extractor, Msg, Reply>(
+        &mut self,
+        extractor: Extractor,
+        ctx: &mut Context<Self, Reply>,
+    ) -> Result<Msg, Error>
+    where
+        Extractor: FnOnce(UserAgentRequestPayload) -> Option<Msg>,
+        Reply: kameo::Reply,
+    {
+        let msg = self.props.transport.recv().await.ok_or_else(|| {
+            error!(
+                actor = "useragent",
+                reason = "channel closed",
+                "recv.failed"
+            );
+            ctx.stop();
+            Error::ConnectionLost
+        })?;
+
+        msg.payload.and_then(extractor).ok_or_else(|| {
+            error!(
+                actor = "useragent",
+                reason = "unexpected message",
+                "recv.failed"
+            );
+            ctx.stop();
+            Error::UnexpectedMessage
+        })
+    }
+}
+
+impl UserAgentSession {
+    pub async fn process_transport_inbound(&mut self, req: UserAgentRequest) -> Output {
+        let msg = req.payload.ok_or_else(|| {
+            error!(actor = "useragent", "Received message with no payload");
+            TransportResponseError::MissingRequestPayload
+        })?;
+
+        match msg {
+            UserAgentRequestPayload::UnsealStart(unseal_start) => {
+                self.handle_unseal_request(unseal_start).await
+            }
+            UserAgentRequestPayload::UnsealEncryptedKey(unseal_encrypted_key) => {
+                self.handle_unseal_encrypted_key(unseal_encrypted_key).await
+            }
+            UserAgentRequestPayload::EvmWalletCreate(_) => self.handle_evm_wallet_create().await,
+            UserAgentRequestPayload::EvmWalletList(_) => self.handle_evm_wallet_list().await,
+            UserAgentRequestPayload::SdkClientApprove(req) => {
+                self.handle_sdk_client_approve(req).await
+            }
+            UserAgentRequestPayload::SdkClientRevoke(req) => {
+                self.handle_sdk_client_revoke(req).await
+            }
+            UserAgentRequestPayload::SdkClientList(_) => self.handle_sdk_client_list().await,
+            _ => Err(TransportResponseError::UnexpectedRequestPayload),
+        }
+    }
+}
+
+type Output = Result<UserAgentResponse, TransportResponseError>;
+
+fn response(payload: UserAgentResponsePayload) -> UserAgentResponse {
+    UserAgentResponse {
+        payload: Some(payload),
+    }
+}
+
+impl UserAgentSession {
+    async fn handle_unseal_request(&mut self, req: UnsealStart) -> Output {
+        let secret = EphemeralSecret::random();
+        let public_key = PublicKey::from(&secret);
+
+        let client_pubkey_bytes: [u8; 32] = req
+            .client_pubkey
+            .try_into()
+            .map_err(|_| TransportResponseError::InvalidClientPubkeyLength)?;
+
+        let client_public_key = PublicKey::from(client_pubkey_bytes);
+
+        self.transition(UserAgentEvents::UnsealRequest(UnsealContext {
+            secret: Mutex::new(Some(secret)),
+            client_public_key,
+        }))?;
+
+        Ok(response(UserAgentResponsePayload::UnsealStartResponse(
+            UnsealStartResponse {
+                server_pubkey: public_key.as_bytes().to_vec(),
+            },
+        )))
+    }
+
+    async fn handle_unseal_encrypted_key(&mut self, req: UnsealEncryptedKey) -> Output {
+        let UserAgentStates::WaitingForUnsealKey(unseal_context) = self.state.state() else {
+            error!("Received unseal encrypted key in invalid state");
+            return Err(TransportResponseError::InvalidStateForUnsealEncryptedKey);
+        };
+        let ephemeral_secret = {
+            let mut secret_lock = unseal_context.secret.lock().unwrap();
+            let secret = secret_lock.take();
+            match secret {
+                Some(secret) => secret,
+                None => {
+                    drop(secret_lock);
+                    error!("Ephemeral secret already taken");
+                    self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                    return Ok(response(UserAgentResponsePayload::UnsealResult(
+                        UnsealResult::InvalidKey.into(),
+                    )));
+                }
+            }
+        };
+
+        let nonce = XNonce::from_slice(&req.nonce);
+
+        let shared_secret = ephemeral_secret.diffie_hellman(&unseal_context.client_public_key);
+        let cipher = XChaCha20Poly1305::new(shared_secret.as_bytes().into());
+
+        let mut seal_key_buffer = MemSafe::new(req.ciphertext.clone()).unwrap();
+
+        let decryption_result = {
+            let mut write_handle = seal_key_buffer.write().unwrap();
+            let write_handle = write_handle.deref_mut();
+            cipher.decrypt_in_place(nonce, &req.associated_data, write_handle)
+        };
+
+        match decryption_result {
+            Ok(_) => {
+                match self
+                    .props
+                    .actors
+                    .key_holder
+                    .ask(TryUnseal {
+                        seal_key_raw: seal_key_buffer,
+                    })
+                    .await
+                {
+                    Ok(_) => {
+                        info!("Successfully unsealed key with client-provided key");
+                        self.transition(UserAgentEvents::ReceivedValidKey)?;
+                        Ok(response(UserAgentResponsePayload::UnsealResult(
+                            UnsealResult::Success.into(),
+                        )))
+                    }
+                    Err(SendError::HandlerError(keyholder::Error::InvalidKey)) => {
+                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                        Ok(response(UserAgentResponsePayload::UnsealResult(
+                            UnsealResult::InvalidKey.into(),
+                        )))
+                    }
+                    Err(SendError::HandlerError(err)) => {
+                        error!(?err, "Keyholder failed to unseal key");
+                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                        Ok(response(UserAgentResponsePayload::UnsealResult(
+                            UnsealResult::InvalidKey.into(),
+                        )))
+                    }
+                    Err(err) => {
+                        error!(?err, "Failed to send unseal request to keyholder");
+                        self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                        Err(TransportResponseError::KeyHolderActorUnreachable)
+                    }
+                }
+            }
+            Err(err) => {
+                error!(?err, "Failed to decrypt unseal key");
+                self.transition(UserAgentEvents::ReceivedInvalidKey)?;
+                Ok(response(UserAgentResponsePayload::UnsealResult(
+                    UnsealResult::InvalidKey.into(),
+                )))
+            }
+        }
+    }
+}
+
+impl UserAgentSession {
+    async fn handle_evm_wallet_create(&mut self) -> Output {
+        use evm_proto::wallet_create_response::Result as CreateResult;
+
+        let result = match self.props.actors.evm.ask(Generate {}).await {
+            Ok(address) => CreateResult::Wallet(evm_proto::WalletEntry {
+                address: address.as_slice().to_vec(),
+            }),
+            Err(err) => CreateResult::Error(map_evm_error("wallet create", err).into()),
+        };
+
+        Ok(response(UserAgentResponsePayload::EvmWalletCreate(
+            evm_proto::WalletCreateResponse {
+                result: Some(result),
+            },
+        )))
+    }
+
+    async fn handle_evm_wallet_list(&mut self) -> Output {
+        use evm_proto::wallet_list_response::Result as ListResult;
+
+        let result = match self.props.actors.evm.ask(ListWallets {}).await {
+            Ok(wallets) => ListResult::Wallets(evm_proto::WalletList {
+                wallets: wallets
+                    .into_iter()
+                    .map(|addr| evm_proto::WalletEntry {
+                        address: addr.as_slice().to_vec(),
+                    })
+                    .collect(),
+            }),
+            Err(err) => ListResult::Error(map_evm_error("wallet list", err).into()),
+        };
+
+        Ok(response(UserAgentResponsePayload::EvmWalletList(
+            evm_proto::WalletListResponse {
+                result: Some(result),
+            },
+        )))
+    }
+}
+
+impl UserAgentSession {
+    async fn handle_sdk_client_approve(&mut self, req: SdkClientApproveRequest) -> Output {
+        use sdk_client_approve_response::Result as ApproveResult;
+
+        if req.pubkey.len() != 32 {
+            return Ok(response(UserAgentResponsePayload::SdkClientApprove(
+                SdkClientApproveResponse {
+                    result: Some(ApproveResult::Error(ProtoSdkClientError::Internal.into())),
+                },
+            )));
+        }
+
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as i32;
+
+        let mut conn = match self.props.db.get().await {
+            Ok(c) => c,
+            Err(e) => {
+                error!(?e, "Failed to get DB connection for sdk_client_approve");
+                return Ok(response(UserAgentResponsePayload::SdkClientApprove(
+                    SdkClientApproveResponse {
+                        result: Some(ApproveResult::Error(ProtoSdkClientError::Internal.into())),
+                    },
+                )));
+            }
+        };
+
+        let pubkey_bytes = req.pubkey.clone();
+        let insert_result = insert_into(program_client::table)
+            .values((
+                program_client::public_key.eq(&pubkey_bytes),
+                program_client::nonce.eq(1), // pre-incremented; challenge will use nonce=0
+                program_client::created_at.eq(now),
+                program_client::updated_at.eq(now),
+            ))
+            .execute(&mut conn)
+            .await;
+
+        match insert_result {
+            Ok(_) => {
+                match program_client::table
+                    .filter(program_client::public_key.eq(&pubkey_bytes))
+                    .order(program_client::id.desc())
+                    .select((
+                        program_client::id,
+                        program_client::public_key,
+                        program_client::created_at,
+                    ))
+                    .first::<(i32, Vec<u8>, i32)>(&mut conn)
+                    .await
+                {
+                    Ok((id, pubkey, created_at)) => Ok(response(
+                        UserAgentResponsePayload::SdkClientApprove(SdkClientApproveResponse {
+                            result: Some(ApproveResult::Client(SdkClientEntry {
+                                id,
+                                pubkey,
+                                created_at,
+                            })),
+                        }),
+                    )),
+                    Err(e) => {
+                        error!(?e, "Failed to fetch inserted SDK client");
+                        Ok(response(UserAgentResponsePayload::SdkClientApprove(
+                            SdkClientApproveResponse {
+                                result: Some(ApproveResult::Error(
+                                    ProtoSdkClientError::Internal.into(),
+                                )),
+                            },
+                        )))
+                    }
+                }
+            }
+            Err(diesel::result::Error::DatabaseError(
+                diesel::result::DatabaseErrorKind::UniqueViolation,
+                _,
+            )) => Ok(response(UserAgentResponsePayload::SdkClientApprove(
+                SdkClientApproveResponse {
+                    result: Some(ApproveResult::Error(
+                        ProtoSdkClientError::AlreadyExists.into(),
+                    )),
+                },
+            ))),
+            Err(e) => {
+                error!(?e, "Failed to insert SDK client");
+                Ok(response(UserAgentResponsePayload::SdkClientApprove(
+                    SdkClientApproveResponse {
+                        result: Some(ApproveResult::Error(ProtoSdkClientError::Internal.into())),
+                    },
+                )))
+            }
+        }
+    }
+
+    async fn handle_sdk_client_list(&mut self) -> Output {
+        let mut conn = match self.props.db.get().await {
+            Ok(c) => c,
+            Err(e) => {
+                error!(?e, "Failed to get DB connection for sdk_client_list");
+                return Ok(response(UserAgentResponsePayload::SdkClientList(
+                    SdkClientListResponse {
+                        result: Some(sdk_client_list_response::Result::Error(
+                            ProtoSdkClientError::Internal.into(),
+                        )),
+                    },
+                )));
+            }
+        };
+
+        match program_client::table
+            .select((
+                program_client::id,
+                program_client::public_key,
+                program_client::created_at,
+            ))
+            .load::<(i32, Vec<u8>, i32)>(&mut conn)
+            .await
+        {
+            Ok(rows) => Ok(response(UserAgentResponsePayload::SdkClientList(
+                SdkClientListResponse {
+                    result: Some(sdk_client_list_response::Result::Clients(SdkClientList {
+                        clients: rows
+                            .into_iter()
+                            .map(|(id, pubkey, created_at)| SdkClientEntry {
+                                id,
+                                pubkey,
+                                created_at,
+                            })
+                            .collect(),
+                    })),
+                },
+            ))),
+            Err(e) => {
+                error!(?e, "Failed to list SDK clients");
+                Ok(response(UserAgentResponsePayload::SdkClientList(
+                    SdkClientListResponse {
+                        result: Some(sdk_client_list_response::Result::Error(
+                            ProtoSdkClientError::Internal.into(),
+                        )),
+                    },
+                )))
+            }
+        }
+    }
+
+    async fn handle_sdk_client_revoke(&mut self, req: SdkClientRevokeRequest) -> Output {
+        use sdk_client_revoke_response::Result as RevokeResult;
+
+        let mut conn = match self.props.db.get().await {
+            Ok(c) => c,
+            Err(e) => {
+                error!(?e, "Failed to get DB connection for sdk_client_revoke");
+                return Ok(response(UserAgentResponsePayload::SdkClientRevoke(
+                    SdkClientRevokeResponse {
+                        result: Some(RevokeResult::Error(ProtoSdkClientError::Internal.into())),
+                    },
+                )));
+            }
+        };
+
+        match diesel::delete(program_client::table)
+            .filter(program_client::id.eq(req.client_id))
+            .execute(&mut conn)
+            .await
+        {
+            Ok(0) => Ok(response(UserAgentResponsePayload::SdkClientRevoke(
+                SdkClientRevokeResponse {
+                    result: Some(RevokeResult::Error(ProtoSdkClientError::NotFound.into())),
+                },
+            ))),
+            Ok(_) => Ok(response(UserAgentResponsePayload::SdkClientRevoke(
+                SdkClientRevokeResponse {
+                    result: Some(RevokeResult::Ok(())),
+                },
+            ))),
+            Err(diesel::result::Error::DatabaseError(
+                diesel::result::DatabaseErrorKind::ForeignKeyViolation,
+                _,
+            )) => Ok(response(UserAgentResponsePayload::SdkClientRevoke(
+                SdkClientRevokeResponse {
+                    result: Some(RevokeResult::Error(
+                        ProtoSdkClientError::HasRelatedData.into(),
+                    )),
+                },
+            ))),
+            Err(e) => {
+                error!(?e, "Failed to delete SDK client");
+                Ok(response(UserAgentResponsePayload::SdkClientRevoke(
+                    SdkClientRevokeResponse {
+                        result: Some(RevokeResult::Error(ProtoSdkClientError::Internal.into())),
+                    },
+                )))
+            }
+        }
+    }
+}
+
+fn map_evm_error<M>(op: &str, err: SendError<M, crate::actors::evm::Error>) -> evm_proto::EvmError {
+    use crate::actors::{evm::Error as EvmError, keyholder::Error as KhError};
+    match err {
+        SendError::HandlerError(EvmError::Keyholder(KhError::NotBootstrapped)) => {
+            evm_proto::EvmError::VaultSealed
+        }
+        SendError::HandlerError(err) => {
+            error!(?err, "EVM {op} failed");
+            evm_proto::EvmError::Internal
+        }
+        _ => {
+            error!("EVM actor unreachable during {op}");
+            evm_proto::EvmError::Internal
+        }
+    }
+}
+
+impl Actor for UserAgentSession {
+    type Args = Self;
+
+    type Error = TransportResponseError;
+
+    async fn on_start(
+        args: Self::Args,
+        this: kameo::prelude::ActorRef<Self>,
+    ) -> Result<Self, Self::Error> {
+        args.props
+            .actors
+            .router
+            .ask(RegisterUserAgent {
+                actor: this.clone(),
+            })
+            .await
+            .map_err(|err| {
+                error!(?err, "Failed to register user agent connection with router");
+                TransportResponseError::ConnectionRegistrationFailed
+            })?;
+        Ok(args)
+    }
+
+    async fn next(
+        &mut self,
+        _actor_ref: kameo::prelude::WeakActorRef<Self>,
+        mailbox_rx: &mut kameo::prelude::MailboxReceiver<Self>,
+    ) -> Option<kameo::mailbox::Signal<Self>> {
+        loop {
+            select! {
+                signal = mailbox_rx.recv() => {
+                    return signal;
+                }
+                msg = self.props.transport.recv() => {
+                    match msg {
+                        Some(request) => {
+                            match self.process_transport_inbound(request).await {
+                                Ok(response) => {
+                                    if self.props.transport.send(Ok(response)).await.is_err() {
+                                        error!(actor = "useragent", reason = "channel closed", "send.failed");
+                                        return Some(kameo::mailbox::Signal::Stop);
+                                    }
+                                }
+                                Err(err) => {
+                                    let _ = self.props.transport.send(Err(err)).await;
+                                    return Some(kameo::mailbox::Signal::Stop);
+                                }
+                            }
+                        }
+                        None => {
+                            info!(actor = "useragent", "transport.closed");
+                            return Some(kameo::mailbox::Signal::Stop);
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+impl UserAgentSession {
+    pub fn new_test(db: crate::db::DatabasePool, actors: crate::actors::GlobalActors) -> Self {
+        use arbiter_proto::transport::DummyTransport;
+        let transport: super::Transport = Box::new(DummyTransport::new());
+        let props = UserAgentConnection::new(db, actors, transport);
+        Self {
+            props,
+            state: UserAgentStateMachine::new(DummyContext),
+        }
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/session/state.rs

@@ -0,0 +1,27 @@
+use std::sync::Mutex;
+
+use x25519_dalek::{EphemeralSecret, PublicKey};
+
+pub struct UnsealContext {
+    pub client_public_key: PublicKey,
+    pub secret: Mutex<Option<EphemeralSecret>>,
+}
+
+smlang::statemachine!(
+    name: UserAgent,
+    custom_error: false,
+    transitions: {
+        *Idle + UnsealRequest(UnsealContext) / generate_temp_keypair = WaitingForUnsealKey(UnsealContext),
+        WaitingForUnsealKey(UnsealContext) + ReceivedValidKey = Unsealed,
+        WaitingForUnsealKey(UnsealContext) + ReceivedInvalidKey = Idle,
+    }
+);
+
+pub struct DummyContext;
+impl UserAgentStateMachineContext for DummyContext {
+    #[allow(missing_docs)]
+    #[allow(clippy::unused_unit)]
+    fn generate_temp_keypair(&mut self, event_data: UnsealContext) -> Result<UnsealContext, ()> {
+        Ok(event_data)
+    }
+}

server/crates/arbiter-server/src/actors/user_agent/transport.rs

@@ -1,95 +0,0 @@
-use super::UserAgentActor;
-use arbiter_proto::proto::{
-    UserAgentRequest, UserAgentResponse,
-    auth::{
-        self, AuthChallenge, AuthChallengeRequest, AuthOk, ClientMessage,
-        ServerMessage as AuthServerMessage, client_message::Payload as ClientAuthPayload,
-        server_message::Payload as ServerAuthPayload,
-    },
-    user_agent_request::Payload as UserAgentRequestPayload,
-    user_agent_response::Payload as UserAgentResponsePayload,
-};
-use futures::StreamExt;
-use kameo::{
-    actor::{ActorRef, Spawn as _},
-    error::SendError,
-};
-use tokio::sync::mpsc;
-use tonic::Status;
-use tracing::error;
-
-use crate::{
-    actors::user_agent::{HandleAuthChallengeRequest, HandleAuthChallengeSolution},
-    context::ServerContext,
-};
-
-pub(crate) async fn handle_user_agent(
-    context: ServerContext,
-    mut req_stream: tonic::Streaming<UserAgentRequest>,
-    tx: mpsc::Sender<Result<UserAgentResponse, Status>>,
-) {
-    let actor = UserAgentActor::spawn(UserAgentActor::new(context, tx.clone()));
-
-    while let Some(Ok(req)) = req_stream.next().await
-        && actor.is_alive()
-    {
-        match process_message(&actor, req).await {
-            Ok(resp) => {
-                if tx.send(Ok(resp)).await.is_err() {
-                    error!(actor = "useragent", "Failed to send response to client");
-                    break;
-                }
-            }
-            Err(status) => {
-                let _ = tx.send(Err(status)).await;
-                break;
-            }
-        }
-    }
-
-    actor.kill();
-}
-
-async fn process_message(
-    actor: &ActorRef<UserAgentActor>,
-    req: UserAgentRequest,
-) -> Result<UserAgentResponse, Status> {
-    let msg = req.payload.ok_or_else(|| {
-        error!(actor = "useragent", "Received message with no payload");
-        Status::invalid_argument("Expected message with payload")
-    })?;
-
-    let UserAgentRequestPayload::AuthMessage(ClientMessage {
-        payload: Some(client_message),
-    }) = msg
-    else {
-        error!(
-            actor = "useragent",
-            "Received unexpected message type during authentication"
-        );
-        return Err(Status::invalid_argument(
-            "Expected AuthMessage with ClientMessage payload",
-        ));
-    };
-
-    match client_message {
-        ClientAuthPayload::AuthChallengeRequest(req) => actor
-            .ask(HandleAuthChallengeRequest { req })
-            .await
-            .map_err(into_status),
-        ClientAuthPayload::AuthChallengeSolution(solution) => actor
-            .ask(HandleAuthChallengeSolution { solution })
-            .await
-            .map_err(into_status),
-    }
-}
-
-fn into_status<M>(e: SendError<M, Status>) -> Status {
-    match e {
-        SendError::HandlerError(status) => status,
-        _ => {
-            error!(actor = "useragent", "Failed to send message to actor");
-            Status::internal("session failure")
-        }
-    }
-}

server/crates/arbiter-server/src/context.rs

@@ -1,162 +0,0 @@
-use std::sync::Arc;
-
-use diesel::OptionalExtension as _;
-use diesel_async::RunQueryDsl as _;
-use ed25519_dalek::VerifyingKey;
-use kameo::actor::{ActorRef, Spawn};
-use miette::Diagnostic;
-use rand::rngs::StdRng;
-use smlang::statemachine;
-use thiserror::Error;
-use tokio::sync::RwLock;
-
-use crate::{
-    context::{
-        bootstrap::{BootstrapActor, generate_token},
-        lease::LeaseHandler,
-        tls::{TlsDataRaw, TlsManager},
-    },
-    db::{
-        self,
-        models::ArbiterSetting,
-        schema::{self, arbiter_settings},
-    },
-};
-
-pub(crate) mod bootstrap;
-pub(crate) mod lease;
-pub(crate) mod tls;
-
-#[derive(Error, Debug, Diagnostic)]
-pub enum InitError {
-    #[error("Database setup failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_setup))]
-    DatabaseSetup(#[from] db::DatabaseSetupError),
-
-    #[error("Connection acquire failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_pool))]
-    DatabasePool(#[from] db::PoolError),
-
-    #[error("Database query error: {0}")]
-    #[diagnostic(code(arbiter_server::init::database_query))]
-    DatabaseQuery(#[from] diesel::result::Error),
-
-    #[error("TLS initialization failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::tls_init))]
-    Tls(#[from] tls::TlsInitError),
-
-    #[error("Bootstrap token generation failed: {0}")]
-    #[diagnostic(code(arbiter_server::init::bootstrap_token))]
-    BootstrapToken(#[from] bootstrap::BootstrapError),
-
-    #[error("I/O Error: {0}")]
-    #[diagnostic(code(arbiter_server::init::io))]
-    Io(#[from] std::io::Error),
-}
-
-// TODO: Placeholder for secure root key cell implementation
-pub struct KeyStorage;
-
-statemachine! {
-    name: Server,
-    transitions: {
-        *NotBootstrapped + Bootstrapped = Sealed,
-        Sealed + Unsealed(KeyStorage) / move_key = Ready(KeyStorage),
-        Ready(KeyStorage) + Sealed / dispose_key = Sealed,
-    }
-}
-pub struct _Context;
-impl ServerStateMachineContext for _Context {
-    fn move_key(&mut self, _event_data: KeyStorage) -> Result<KeyStorage, ()> {
-        todo!()
-    }
-
-    #[allow(missing_docs)]
-    #[allow(clippy::unused_unit)]
-    fn dispose_key(&mut self, _state_data: &KeyStorage) -> Result<(), ()> {
-        todo!()
-    }
-}
-
-pub(crate) struct _ServerContextInner {
-    pub db: db::DatabasePool,
-    pub state: RwLock<ServerStateMachine<_Context>>,
-    pub rng: StdRng,
-    pub tls: TlsManager,
-    pub bootstrapper: ActorRef<BootstrapActor>,
-}
-#[derive(Clone)]
-pub(crate) struct ServerContext(Arc<_ServerContextInner>);
-
-impl std::ops::Deref for ServerContext {
-    type Target = _ServerContextInner;
-
-    fn deref(&self) -> &Self::Target {
-        &self.0
-    }
-}
-
-impl ServerContext {
-    async fn load_tls(
-        db: &mut db::DatabaseConnection,
-        settings: Option<&ArbiterSetting>,
-    ) -> Result<TlsManager, InitError> {
-        match &settings {
-            Some(settings) => {
-                let tls_data_raw = TlsDataRaw {
-                    cert: settings.cert.clone(),
-                    key: settings.cert_key.clone(),
-                };
-
-                Ok(TlsManager::new(Some(tls_data_raw)).await?)
-            }
-            None => {
-                let tls = TlsManager::new(None).await?;
-                let tls_data_raw = tls.bytes();
-
-                diesel::insert_into(arbiter_settings::table)
-                    .values(&ArbiterSetting {
-                        id: 1,
-                        root_key_id: None,
-                        cert_key: tls_data_raw.key,
-                        cert: tls_data_raw.cert,
-                    })
-                    .execute(db)
-                    .await?;
-
-                Ok(tls)
-            }
-        }
-    }
-
-    pub async fn new(db: db::DatabasePool) -> Result<Self, InitError> {
-        let mut conn = db.get().await?;
-        let rng = rand::make_rng();
-
-        let settings = arbiter_settings::table
-            .first::<ArbiterSetting>(&mut conn)
-            .await
-            .optional()?;
-
-        let tls = Self::load_tls(&mut conn, settings.as_ref()).await?;
-
-        drop(conn);
-
-        let mut state = ServerStateMachine::new(_Context);
-
-        if let Some(settings) = &settings
-            && settings.root_key_id.is_some()
-        {
-            // TODO: pass the encrypted root key to the state machine and let it handle decryption and transition to Sealed
-            let _ = state.process_event(ServerEvents::Bootstrapped);
-        }
-
-        Ok(Self(Arc::new(_ServerContextInner {
-            bootstrapper: BootstrapActor::spawn(BootstrapActor::new(&db).await?),
-            db,
-            rng,
-            tls,
-            state: RwLock::new(state),
-        })))
-    }
-}

server/crates/arbiter-server/src/context/lease.rs

@@ -1,41 +0,0 @@
-use std::sync::Arc;
-
-use dashmap::DashSet;
-
-#[derive(Clone, Default)]
-struct LeaseStorage<T: Eq + std::hash::Hash>(Arc<DashSet<T>>);
-
-// A lease that automatically releases the item when dropped
-pub struct Lease<T: Clone + std::hash::Hash + Eq> {
-    item: T,
-    storage: LeaseStorage<T>,
-}
-impl<T: Clone + std::hash::Hash + Eq> Drop for Lease<T> {
-    fn drop(&mut self) {
-        self.storage.0.remove(&self.item);
-    }
-}
-
-#[derive(Clone, Default)]
-pub struct LeaseHandler<T: Clone + std::hash::Hash + Eq> {
-    storage: LeaseStorage<T>,
-}
-
-impl<T: Clone + std::hash::Hash + Eq> LeaseHandler<T> {
-    pub fn new() -> Self {
-        Self {
-            storage: LeaseStorage(Arc::new(DashSet::new())),
-        }
-    }
-
-    pub fn acquire(&self, item: T) -> Result<Lease<T>, ()> {
-        if self.storage.0.insert(item.clone()) {
-            Ok(Lease {
-                item,
-                storage: self.storage.clone(),
-            })
-        } else {
-            Err(())
-        }
-    }
-}

server/crates/arbiter-server/src/context/mod.rs

@@ -0,0 +1,65 @@
+use std::sync::Arc;
+
+use miette::Diagnostic;
+use thiserror::Error;
+
+use crate::{
+    actors::GlobalActors,
+    context::tls::TlsManager,
+    db::{self},
+};
+
+pub mod tls;
+
+#[derive(Error, Debug, Diagnostic)]
+pub enum InitError {
+    #[error("Database setup failed: {0}")]
+    #[diagnostic(code(arbiter_server::init::database_setup))]
+    DatabaseSetup(#[from] db::DatabaseSetupError),
+
+    #[error("Connection acquire failed: {0}")]
+    #[diagnostic(code(arbiter_server::init::database_pool))]
+    DatabasePool(#[from] db::PoolError),
+
+    #[error("Database query error: {0}")]
+    #[diagnostic(code(arbiter_server::init::database_query))]
+    DatabaseQuery(#[from] diesel::result::Error),
+
+    #[error("TLS initialization failed: {0}")]
+    #[diagnostic(code(arbiter_server::init::tls_init))]
+    Tls(#[from] tls::InitError),
+
+    #[error("Actor spawn failed: {0}")]
+    #[diagnostic(code(arbiter_server::init::actor_spawn))]
+    ActorSpawn(#[from] crate::actors::SpawnError),
+
+    #[error("I/O Error: {0}")]
+    #[diagnostic(code(arbiter_server::init::io))]
+    Io(#[from] std::io::Error),
+}
+
+pub struct _ServerContextInner {
+    pub db: db::DatabasePool,
+    pub tls: TlsManager,
+    pub actors: GlobalActors,
+}
+#[derive(Clone)]
+pub struct ServerContext(Arc<_ServerContextInner>);
+
+impl std::ops::Deref for ServerContext {
+    type Target = _ServerContextInner;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl ServerContext {
+    pub async fn new(db: db::DatabasePool) -> Result<Self, InitError> {
+        Ok(Self(Arc::new(_ServerContextInner {
+            actors: GlobalActors::spawn(db.clone()).await?,
+            tls: TlsManager::new(db.clone()).await?,
+            db,
+        })))
+    }
+}

server/crates/arbiter-server/src/context/tls.rs

@@ -1,13 +1,36 @@
 use std::string::FromUtf8Error;
 
+use diesel::{ExpressionMethods as _, QueryDsl, SelectableHelper as _};
+use diesel_async::{AsyncConnection, RunQueryDsl};
 use miette::Diagnostic;
-use rcgen::{Certificate, KeyPair};
-use rustls::pki_types::CertificateDer;
+use pem::Pem;
+use rcgen::{
+    BasicConstraints, Certificate, CertificateParams, CertifiedIssuer, DistinguishedName, DnType,
+    IsCa, Issuer, KeyPair, KeyUsagePurpose,
+};
+use rustls::pki_types::{pem::PemObject};
 use thiserror::Error;
+use tonic::transport::CertificateDer;
 
+use crate::db::{
+    self,
+    models::{NewTlsHistory, TlsHistory},
+    schema::{
+        arbiter_settings,
+        tls_history::{self},
+    },
+};
+
+const ENCODE_CONFIG: pem::EncodeConfig = {
+    let line_ending = match cfg!(target_family = "windows") {
+        true => pem::LineEnding::CRLF,
+        false => pem::LineEnding::LF,
+    };
+    pem::EncodeConfig::new().set_line_ending(line_ending)
+};
 
 #[derive(Error, Debug, Diagnostic)]
-pub enum TlsInitError {
+pub enum InitError {
     #[error("Key generation error during TLS initialization: {0}")]
     #[diagnostic(code(arbiter_server::tls_init::key_generation))]
     KeyGeneration(#[from] rcgen::Error),
@@ -19,71 +42,211 @@ pub enum TlsInitError {
     #[error("Key deserialization error: {0}")]
     #[diagnostic(code(arbiter_server::tls_init::key_deserialization))]
     KeyDeserializationError(rcgen::Error),
+
+    #[error("Database error during TLS initialization: {0}")]
+    #[diagnostic(code(arbiter_server::tls_init::database_error))]
+    DatabaseError(#[from] diesel::result::Error),
+
+    #[error("Pem deserialization error during TLS initialization: {0}")]
+    #[diagnostic(code(arbiter_server::tls_init::pem_deserialization))]
+    PemDeserializationError(#[from] rustls::pki_types::pem::Error),
+
+    #[error("Database pool acquire error during TLS initialization: {0}")]
+    #[diagnostic(code(arbiter_server::tls_init::database_pool_acquire))]
+    DatabasePoolAcquire(#[from] db::PoolError),
 }
 
-pub struct TlsData {
-    pub cert: CertificateDer<'static>,
-    pub keypair: KeyPair,
+pub type PemCert = String;
+
+pub fn encode_cert_to_pem(cert: &CertificateDer) -> PemCert {
+    pem::encode_config(
+        &Pem::new("CERTIFICATE", cert.to_vec()),
+        ENCODE_CONFIG,
+    )
 }
 
-pub struct TlsDataRaw {
-    pub cert: Vec<u8>,
-    pub key: Vec<u8>,
+#[allow(unused)]
+struct SerializedTls {
+    cert_pem: PemCert,
+    cert_key_pem: String,
 }
-impl TlsDataRaw {
-    pub fn serialize(cert: &TlsData) -> Self {
-        Self {
-            cert: cert.cert.as_ref().to_vec(),
-            key: cert.keypair.serialize_pem().as_bytes().to_vec(),
-        }
+
+struct TlsCa {
+    issuer: Issuer<'static, KeyPair>,
+    cert: CertificateDer<'static>,
+}
+
+impl TlsCa {
+    fn generate() -> Result<Self, InitError> {
+        let keypair = KeyPair::generate()?;
+        let mut params = CertificateParams::new(["Arbiter Instance CA".into()])?;
+        params.is_ca = IsCa::Ca(BasicConstraints::Unconstrained);
+        params.key_usages = vec![
+            KeyUsagePurpose::KeyCertSign,
+            KeyUsagePurpose::CrlSign,
+            KeyUsagePurpose::DigitalSignature,
+        ];
+
+        let mut dn = DistinguishedName::new();
+        dn.push(DnType::CommonName, "Arbiter Instance CA");
+        params.distinguished_name = dn;
+        let certified_issuer = CertifiedIssuer::self_signed(params, keypair)?;
+
+        let cert_key_pem = certified_issuer.key().serialize_pem();
+
+        let issuer = Issuer::from_ca_cert_pem(
+            &certified_issuer.pem(),
+            KeyPair::from_pem(cert_key_pem.as_ref()).unwrap(),
+        )
+        .unwrap();
+
+        Ok(Self {
+            issuer,
+            cert: certified_issuer.der().clone(),
+        })
+    }
+    fn generate_leaf(&self) -> Result<TlsCert, InitError> {
+        let cert_key = KeyPair::generate()?;
+        let mut params = CertificateParams::new(["Arbiter Instance Leaf".into()])?;
+        params.is_ca = IsCa::NoCa;
+        params.key_usages = vec![
+            KeyUsagePurpose::DigitalSignature,
+            KeyUsagePurpose::KeyEncipherment,
+        ];
+
+        let mut dn = DistinguishedName::new();
+        dn.push(DnType::CommonName, "Arbiter Instance Leaf");
+        params.distinguished_name = dn;
+
+        let new_cert = params.signed_by(&cert_key, &self.issuer)?;
+
+        Ok(TlsCert {
+            cert: new_cert,
+            cert_key,
+        })
     }
 
-    pub fn deserialize(&self) -> Result<TlsData, TlsInitError> {
-        let cert = CertificateDer::from_slice(&self.cert).into_owned();
+    #[allow(unused)]
+    fn serialize(&self) -> Result<SerializedTls, InitError> {
+        let cert_key_pem = self.issuer.key().serialize_pem();
+        Ok(SerializedTls {
+            cert_pem: encode_cert_to_pem(&self.cert),
+            cert_key_pem,
+        })
+    }
 
-        let key =
-            String::from_utf8(self.key.clone()).map_err(TlsInitError::KeyInvalidFormat)?;
-
-        let keypair = KeyPair::from_pem(&key).map_err(TlsInitError::KeyDeserializationError)?;
-
-        Ok(TlsData { cert, keypair })
+    #[allow(unused)]
+    fn try_deserialize(cert_pem: &str, cert_key_pem: &str) -> Result<Self, InitError> {
+        let keypair =
+            KeyPair::from_pem(cert_key_pem).map_err(InitError::KeyDeserializationError)?;
+        let issuer = Issuer::from_ca_cert_pem(cert_pem, keypair)?;
+        Ok(Self {
+            issuer,
+            cert: CertificateDer::from_pem_slice(cert_pem.as_bytes())?,
+        })
     }
 }
 
-fn generate_cert(key: &KeyPair) -> Result<Certificate, rcgen::Error> {
-    let params = rcgen::CertificateParams::new(vec![
-        "arbiter.local".to_string(),
-        "localhost".to_string(),
-    ])?;
-
-    params.self_signed(key)
+struct TlsCert {
+    cert: Certificate,
+    cert_key: KeyPair,
 }
 
 // TODO: Implement cert rotation
-pub(crate) struct TlsManager {
-    data: TlsData,
+pub struct TlsManager {
+    cert: CertificateDer<'static>,
+    keypair: KeyPair,
+    ca_cert: CertificateDer<'static>,
+    _db: db::DatabasePool,
 }
 
 impl TlsManager {
-    pub async fn new(data: Option<TlsDataRaw>) -> Result<Self, TlsInitError> {
-        match data {
-            Some(raw) => {
-                let tls_data = raw.deserialize()?;
-                Ok(Self { data: tls_data })
-            }
-            None => {
-                let keypair = KeyPair::generate()?;
-                let cert = generate_cert(&keypair)?;
-                let tls_data = TlsData {
-                    cert: cert.der().clone(),
-                    keypair,
+    pub async fn generate_new(db: &db::DatabasePool) -> Result<Self, InitError> {
+        let ca = TlsCa::generate()?;
+        let new_cert = ca.generate_leaf()?;
+
+        {
+            let mut conn = db.get().await?;
+            conn.transaction(|conn| {
+                Box::pin(async {
+                    let new_tls_history = NewTlsHistory {
+                        cert: new_cert.cert.pem(),
+                        cert_key: new_cert.cert_key.serialize_pem(),
+                        ca_cert: encode_cert_to_pem(&ca.cert),
+                        ca_key: ca.issuer.key().serialize_pem(),
+                    };
+
+                    let inserted_tls_history: i32 = diesel::insert_into(tls_history::table)
+                        .values(&new_tls_history)
+                        .returning(tls_history::id)
+                        .get_result(conn)
+                        .await?;
+
+                    diesel::update(arbiter_settings::table)
+                        .set(arbiter_settings::tls_id.eq(inserted_tls_history))
+                        .execute(conn)
+                        .await?;
+
+                    Result::<_, diesel::result::Error>::Ok(())
+                })
+            })
+            .await?;
+        }
+
+        Ok(Self {
+            cert: new_cert.cert.der().clone(),
+            keypair: new_cert.cert_key,
+            ca_cert: ca.cert,
+            _db: db.clone(),
+        })
+    }
+
+    pub async fn new(db: db::DatabasePool) -> Result<Self, InitError> {
+        let cert_data: Option<TlsHistory> = {
+            let mut conn = db.get().await?;
+            arbiter_settings::table
+                .left_join(tls_history::table)
+                .select(Option::<TlsHistory>::as_select())
+                .first(&mut conn)
+                .await?
+        };
+
+        match cert_data {
+            Some(data) => {
+                let try_load = || -> Result<_, Box<dyn std::error::Error>> {
+                    let keypair = KeyPair::from_pem(&data.cert_key)?;
+                    let cert = CertificateDer::from_pem_slice(data.cert.as_bytes())?;
+                    let ca_cert = CertificateDer::from_pem_slice(data.ca_cert.as_bytes())?;
+                    Ok(Self {
+                        cert,
+                        keypair,
+                        ca_cert,
+                        _db: db.clone(),
+                    })
                 };
-                Ok(Self { data: tls_data })
+                match try_load() {
+                    Ok(manager) => Ok(manager),
+                    Err(e) => {
+                        eprintln!("Failed to load existing TLS certs: {e}. Generating new ones.");
+                        Self::generate_new(&db).await
+                    }
+                }
             }
+            None => Self::generate_new(&db).await,
         }
     }
 
-    pub fn bytes(&self) -> TlsDataRaw {
-        TlsDataRaw::serialize(&self.data)
+    pub fn cert(&self) -> &CertificateDer<'static> {
+        &self.cert
+    }
+    pub fn ca_cert(&self) -> &CertificateDer<'static> {
+        &self.ca_cert
+    }
+
+    pub fn cert_pem(&self) -> PemCert {
+        encode_cert_to_pem(&self.cert)
+    }
+    pub fn key_pem(&self) -> String {
+        self.keypair.serialize_pem()
     }
 }

server/crates/arbiter-server/src/db/mod.rs

@@ -1,12 +1,7 @@
-use std::sync::Arc;
-
-use diesel::{
-    Connection as _, SqliteConnection,
-    connection::{SimpleConnection as _, TransactionManager},
-};
+use diesel::{Connection as _, SqliteConnection, connection::SimpleConnection as _};
 use diesel_async::{
     AsyncConnection, SimpleAsyncConnection,
-    pooled_connection::{AsyncDieselConnectionManager, ManagerConfig, RecyclingMethod},
+    pooled_connection::{AsyncDieselConnectionManager, ManagerConfig},
     sync_connection_wrapper::SyncConnectionWrapper,
 };
 use diesel_migrations::{EmbeddedMigrations, MigrationHarness, embed_migrations};
@@ -22,30 +17,30 @@ pub type DatabasePool = diesel_async::pooled_connection::bb8::Pool<DatabaseConne
 pub type PoolInitError = diesel_async::pooled_connection::PoolError;
 pub type PoolError = diesel_async::pooled_connection::bb8::RunError;
 
-static DB_FILE: &'static str = "arbiter.sqlite";
+static DB_FILE: &str = "arbiter.sqlite";
 
 const MIGRATIONS: EmbeddedMigrations = embed_migrations!("migrations");
 
 #[derive(Error, Diagnostic, Debug)]
 pub enum DatabaseSetupError {
     #[error("Failed to determine home directory")]
-    #[diagnostic(code(arbiter::db::home_dir_error))]
+    #[diagnostic(code(arbiter::db::home_dir))]
     HomeDir(std::io::Error),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::connection_error))]
+    #[diagnostic(code(arbiter::db::connection))]
     Connection(diesel::ConnectionError),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::concurrency_error))]
+    #[diagnostic(code(arbiter::db::concurrency))]
     ConcurrencySetup(diesel::result::Error),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::migration_error))]
+    #[diagnostic(code(arbiter::db::migration))]
     Migration(Box<dyn std::error::Error + Send + Sync>),
 
     #[error(transparent)]
-    #[diagnostic(code(arbiter::db::pool_error))]
+    #[diagnostic(code(arbiter::db::pool))]
     Pool(#[from] PoolInitError),
 }
 
@@ -96,12 +91,12 @@ fn initialize_database(url: &str) -> Result<(), DatabaseSetupError> {
 
 #[tracing::instrument(level = "info")]
 pub async fn create_pool(url: Option<&str>) -> Result<DatabasePool, DatabaseSetupError> {
-    let database_url = url.map(String::from).unwrap_or(format!(
-        "{}?mode=rwc",
-        (database_path()?
+    let database_url = url.map(String::from).unwrap_or(
+        database_path()?
             .to_str()
-            .expect("database path is not valid UTF-8"))
-    ));
+            .expect("database path is not valid UTF-8")
+            .to_string(),
+    );
 
     initialize_database(&database_url)?;
 
@@ -134,17 +129,16 @@ pub async fn create_pool(url: Option<&str>) -> Result<DatabasePool, DatabaseSetu
     Ok(pool)
 }
 
-#[cfg(test)]
 pub async fn create_test_pool() -> DatabasePool {
     use rand::distr::{Alphanumeric, SampleString as _};
 
     let tempfile_name = Alphanumeric.sample_string(&mut rand::rng(), 16);
 
     let file = std::env::temp_dir().join(tempfile_name);
-    let url = format!(
-        "{}?mode=rwc",
-        file.to_str().expect("temp file path is not valid UTF-8")
-    );
+    let url = file
+        .to_str()
+        .expect("temp file path is not valid UTF-8")
+        .to_string();
 
     create_pool(Some(&url))
         .await

server/crates/arbiter-server/src/db/models.rs

@@ -1,49 +1,339 @@
 #![allow(unused)]
 #![allow(clippy::all)]
 
-use crate::db::schema::{self, aead_encrypted, arbiter_settings};
+use crate::db::schema::{
+    self, aead_encrypted, arbiter_settings, evm_basic_grant, evm_ether_transfer_grant,
+    evm_ether_transfer_grant_target, evm_ether_transfer_limit, evm_token_transfer_grant,
+    evm_token_transfer_log, evm_token_transfer_volume_limit, evm_transaction_log, evm_wallet,
+    root_key_history, tls_history,
+};
+use chrono::{DateTime, Utc};
 use diesel::{prelude::*, sqlite::Sqlite};
+use restructed::Models;
 
 pub mod types {
     use chrono::{DateTime, Utc};
-    pub struct SqliteTimestamp(DateTime<Utc>);
-}
+    use diesel::{
+        deserialize::{FromSql, FromSqlRow},
+        expression::AsExpression,
+        serialize::{IsNull, ToSql},
+        sql_types::Integer,
+        sqlite::{Sqlite, SqliteType},
+    };
 
-#[derive(Queryable, Debug, Insertable)]
+    #[derive(Debug, FromSqlRow, AsExpression)]
+    #[diesel(sql_type = Integer)]
+    #[repr(transparent)] // hint compiler to optimize the wrapper struct away
+    pub struct SqliteTimestamp(pub DateTime<Utc>);
+    impl SqliteTimestamp {
+        pub fn now() -> Self {
+            SqliteTimestamp(Utc::now())
+        }
+    }
+
+    impl From<chrono::DateTime<Utc>> for SqliteTimestamp {
+        fn from(dt: chrono::DateTime<Utc>) -> Self {
+            SqliteTimestamp(dt)
+        }
+    }
+    impl From<SqliteTimestamp> for chrono::DateTime<Utc> {
+        fn from(ts: SqliteTimestamp) -> Self {
+            ts.0
+        }
+    }
+
+    impl ToSql<Integer, Sqlite> for SqliteTimestamp {
+        fn to_sql<'b>(
+            &'b self,
+            out: &mut diesel::serialize::Output<'b, '_, Sqlite>,
+        ) -> diesel::serialize::Result {
+            let unix_timestamp = self.0.timestamp() as i32;
+            out.set_value(unix_timestamp);
+            Ok(IsNull::No)
+        }
+    }
+
+    impl FromSql<Integer, Sqlite> for SqliteTimestamp {
+        fn from_sql(
+            mut bytes: <Sqlite as diesel::backend::Backend>::RawValue<'_>,
+        ) -> diesel::deserialize::Result<Self> {
+            let Some(SqliteType::Long) = bytes.value_type() else {
+                return Err(format!(
+                    "Expected Integer type for SqliteTimestamp, got {:?}",
+                    bytes.value_type()
+                )
+                .into());
+            };
+
+            let unix_timestamp = bytes.read_long();
+            let datetime =
+                DateTime::from_timestamp(unix_timestamp, 0).ok_or("Timestamp is out of bounds")?;
+
+            Ok(SqliteTimestamp(datetime))
+        }
+    }
+
+    /// Key algorithm stored in the `useragent_client.key_type` column.
+    /// Values must stay stable — they are persisted in the database.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq, FromSqlRow, AsExpression, strum::FromRepr)]
+    #[diesel(sql_type = Integer)]
+    #[repr(i32)]
+    pub enum KeyType {
+        Ed25519 = 1,
+        EcdsaSecp256k1 = 2,
+        Rsa = 3,
+    }
+
+    impl ToSql<Integer, Sqlite> for KeyType {
+        fn to_sql<'b>(
+            &'b self,
+            out: &mut diesel::serialize::Output<'b, '_, Sqlite>,
+        ) -> diesel::serialize::Result {
+            out.set_value(*self as i32);
+            Ok(IsNull::No)
+        }
+    }
+
+    impl FromSql<Integer, Sqlite> for KeyType {
+        fn from_sql(
+            mut bytes: <Sqlite as diesel::backend::Backend>::RawValue<'_>,
+        ) -> diesel::deserialize::Result<Self> {
+            let Some(SqliteType::Long) = bytes.value_type() else {
+                return Err("Expected Integer for KeyType".into());
+            };
+            let discriminant = bytes.read_long();
+            KeyType::from_repr(discriminant as i32)
+                .ok_or_else(|| format!("Unknown KeyType discriminant: {discriminant}").into())
+        }
+    }
+}
+pub use types::*;
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[view(
+    NewAeadEncrypted,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
 #[diesel(table_name = aead_encrypted, check_for_backend(Sqlite))]
 pub struct AeadEncrypted {
     pub id: i32,
     pub ciphertext: Vec<u8>,
     pub tag: Vec<u8>,
-    pub current_nonce: i32,
+    pub current_nonce: Vec<u8>,
     pub schema_version: i32,
+    pub associated_root_key_id: i32, // references root_key_history.id
+    pub created_at: SqliteTimestamp,
 }
 
-#[derive(Queryable, Debug, Insertable)]
-#[diesel(table_name = arbiter_settings, check_for_backend(Sqlite))]
-pub struct ArbiterSetting {
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = root_key_history, check_for_backend(Sqlite))]
+#[view(
+    NewRootKeyHistory,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct RootKeyHistory {
     pub id: i32,
-    pub root_key_id: Option<i32>, // references aead_encrypted.id
-    pub cert_key: Vec<u8>,
-    pub cert: Vec<u8>,
+    pub ciphertext: Vec<u8>,
+    pub tag: Vec<u8>,
+    pub root_key_encryption_nonce: Vec<u8>,
+    pub data_encryption_nonce: Vec<u8>,
+    pub schema_version: i32,
+    pub salt: Vec<u8>,
 }
 
-#[derive(Queryable, Debug)]
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = tls_history, check_for_backend(Sqlite))]
+#[view(
+    NewTlsHistory,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct TlsHistory {
+    pub id: i32,
+    pub cert: String,
+    pub cert_key: String, // PEM Encoded private key
+    pub ca_cert: String,  // PEM Encoded certificate for cert signing
+    pub ca_key: String,   // PEM Encoded public key for cert signing
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = arbiter_settings, check_for_backend(Sqlite))]
+pub struct ArbiterSettings {
+    pub id: i32,
+    pub root_key_id: Option<i32>, // references root_key_history.id
+    pub tls_id: Option<i32>,      // references tls_history.id
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_wallet, check_for_backend(Sqlite))]
+#[view(
+    NewEvmWallet,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmWallet {
+    pub id: i32,
+    pub address: Vec<u8>,
+    pub aead_encrypted_id: i32,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Queryable, Debug, Insertable, Selectable)]
 #[diesel(table_name = schema::program_client, check_for_backend(Sqlite))]
 pub struct ProgramClient {
     pub id: i32,
-    pub public_key: Vec<u8>,
     pub nonce: i32,
-    pub created_at: i32,
-    pub updated_at: i32,
+    pub public_key: Vec<u8>,
+    pub created_at: SqliteTimestamp,
+    pub updated_at: SqliteTimestamp,
 }
 
 #[derive(Queryable, Debug)]
 #[diesel(table_name = schema::useragent_client, check_for_backend(Sqlite))]
 pub struct UseragentClient {
     pub id: i32,
-    pub public_key: Vec<u8>,
     pub nonce: i32,
-    pub created_at: i32,
-    pub updated_at: i32,
+    pub public_key: Vec<u8>,
+    pub created_at: SqliteTimestamp,
+    pub updated_at: SqliteTimestamp,
+    pub key_type: KeyType,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_limit, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferLimit,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferLimit {
+    pub id: i32,
+    pub window_secs: i32,
+    pub max_volume: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_basic_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmBasicGrant,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmBasicGrant {
+    pub id: i32,
+    pub wallet_id: i32, // references evm_wallet.id
+    pub client_id: i32, // references program_client.id
+    pub chain_id: i32,
+    pub valid_from: Option<SqliteTimestamp>,
+    pub valid_until: Option<SqliteTimestamp>,
+    pub max_gas_fee_per_gas: Option<Vec<u8>>,
+    pub max_priority_fee_per_gas: Option<Vec<u8>>,
+    pub rate_limit_count: Option<i32>,
+    pub rate_limit_window_secs: Option<i32>,
+    pub revoked_at: Option<SqliteTimestamp>,
+    pub created_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_transaction_log, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTransactionLog,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTransactionLog {
+    pub id: i32,
+    pub grant_id: i32,
+    pub client_id: i32,
+    pub wallet_id: i32,
+    pub chain_id: i32,
+    pub eth_value: Vec<u8>,
+    pub signed_at: SqliteTimestamp,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferGrant,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferGrant {
+    pub id: i32,
+    pub basic_grant_id: i32,
+    pub limit_id: i32, // references evm_ether_transfer_limit.id
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_ether_transfer_grant_target, check_for_backend(Sqlite))]
+#[view(
+    NewEvmEtherTransferGrantTarget,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmEtherTransferGrantTarget {
+    pub id: i32,
+    pub grant_id: i32,
+    pub address: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_grant, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferGrant,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferGrant {
+    pub id: i32,
+    pub basic_grant_id: i32,
+    pub token_contract: Vec<u8>,
+    pub receiver: Option<Vec<u8>>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_volume_limit, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferVolumeLimit,
+    derive(Insertable),
+    omit(id),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferVolumeLimit {
+    pub id: i32,
+    pub grant_id: i32,
+    pub window_secs: i32,
+    pub max_volume: Vec<u8>,
+}
+
+#[derive(Models, Queryable, Debug, Insertable, Selectable)]
+#[diesel(table_name = evm_token_transfer_log, check_for_backend(Sqlite))]
+#[view(
+    NewEvmTokenTransferLog,
+    derive(Insertable),
+    omit(id, created_at),
+    attributes_with = "deriveless"
+)]
+pub struct EvmTokenTransferLog {
+    pub id: i32,
+    pub grant_id: i32,
+    pub log_id: i32,
+    pub chain_id: i32,
+    pub token_contract: Vec<u8>,
+    pub recipient_address: Vec<u8>,
+    pub value: Vec<u8>,
+    pub created_at: SqliteTimestamp,
 }

server/crates/arbiter-server/src/db/schema.rs

@@ -3,10 +3,12 @@
 diesel::table! {
     aead_encrypted (id) {
         id -> Integer,
-        current_nonce -> Integer,
+        current_nonce -> Binary,
         ciphertext -> Binary,
         tag -> Binary,
         schema_version -> Integer,
+        associated_root_key_id -> Integer,
+        created_at -> Integer,
     }
 }
 
@@ -14,8 +16,100 @@ diesel::table! {
     arbiter_settings (id) {
         id -> Integer,
         root_key_id -> Nullable<Integer>,
-        cert_key -> Binary,
-        cert -> Binary,
+        tls_id -> Nullable<Integer>,
+    }
+}
+
+diesel::table! {
+    evm_basic_grant (id) {
+        id -> Integer,
+        wallet_id -> Integer,
+        client_id -> Integer,
+        chain_id -> Integer,
+        valid_from -> Nullable<Integer>,
+        valid_until -> Nullable<Integer>,
+        max_gas_fee_per_gas -> Nullable<Binary>,
+        max_priority_fee_per_gas -> Nullable<Binary>,
+        rate_limit_count -> Nullable<Integer>,
+        rate_limit_window_secs -> Nullable<Integer>,
+        revoked_at -> Nullable<Integer>,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_grant (id) {
+        id -> Integer,
+        basic_grant_id -> Integer,
+        limit_id -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_grant_target (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        address -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_ether_transfer_limit (id) {
+        id -> Integer,
+        window_secs -> Integer,
+        max_volume -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_grant (id) {
+        id -> Integer,
+        basic_grant_id -> Integer,
+        token_contract -> Binary,
+        receiver -> Nullable<Binary>,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_log (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        log_id -> Integer,
+        chain_id -> Integer,
+        token_contract -> Binary,
+        recipient_address -> Binary,
+        value -> Binary,
+        created_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_token_transfer_volume_limit (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        window_secs -> Integer,
+        max_volume -> Binary,
+    }
+}
+
+diesel::table! {
+    evm_transaction_log (id) {
+        id -> Integer,
+        grant_id -> Integer,
+        client_id -> Integer,
+        wallet_id -> Integer,
+        chain_id -> Integer,
+        eth_value -> Binary,
+        signed_at -> Integer,
+    }
+}
+
+diesel::table! {
+    evm_wallet (id) {
+        id -> Integer,
+        address -> Binary,
+        aead_encrypted_id -> Integer,
+        created_at -> Integer,
     }
 }
 
@@ -29,6 +123,29 @@ diesel::table! {
     }
 }
 
+diesel::table! {
+    root_key_history (id) {
+        id -> Integer,
+        root_key_encryption_nonce -> Binary,
+        data_encryption_nonce -> Binary,
+        ciphertext -> Binary,
+        tag -> Binary,
+        schema_version -> Integer,
+        salt -> Binary,
+    }
+}
+
+diesel::table! {
+    tls_history (id) {
+        id -> Integer,
+        cert -> Text,
+        cert_key -> Text,
+        ca_cert -> Text,
+        ca_key -> Text,
+        created_at -> Integer,
+    }
+}
+
 diesel::table! {
     useragent_client (id) {
         id -> Integer,
@@ -36,14 +153,38 @@ diesel::table! {
         public_key -> Binary,
         created_at -> Integer,
         updated_at -> Integer,
+        key_type -> Integer,
     }
 }
 
-diesel::joinable!(arbiter_settings -> aead_encrypted (root_key_id));
+diesel::joinable!(aead_encrypted -> root_key_history (associated_root_key_id));
+diesel::joinable!(arbiter_settings -> root_key_history (root_key_id));
+diesel::joinable!(arbiter_settings -> tls_history (tls_id));
+diesel::joinable!(evm_basic_grant -> evm_wallet (wallet_id));
+diesel::joinable!(evm_basic_grant -> program_client (client_id));
+diesel::joinable!(evm_ether_transfer_grant -> evm_basic_grant (basic_grant_id));
+diesel::joinable!(evm_ether_transfer_grant -> evm_ether_transfer_limit (limit_id));
+diesel::joinable!(evm_ether_transfer_grant_target -> evm_ether_transfer_grant (grant_id));
+diesel::joinable!(evm_token_transfer_grant -> evm_basic_grant (basic_grant_id));
+diesel::joinable!(evm_token_transfer_log -> evm_token_transfer_grant (grant_id));
+diesel::joinable!(evm_token_transfer_log -> evm_transaction_log (log_id));
+diesel::joinable!(evm_token_transfer_volume_limit -> evm_token_transfer_grant (grant_id));
+diesel::joinable!(evm_wallet -> aead_encrypted (aead_encrypted_id));
 
 diesel::allow_tables_to_appear_in_same_query!(
     aead_encrypted,
     arbiter_settings,
+    evm_basic_grant,
+    evm_ether_transfer_grant,
+    evm_ether_transfer_grant_target,
+    evm_ether_transfer_limit,
+    evm_token_transfer_grant,
+    evm_token_transfer_log,
+    evm_token_transfer_volume_limit,
+    evm_transaction_log,
+    evm_wallet,
     program_client,
+    root_key_history,
+    tls_history,
     useragent_client,
 );

server/crates/arbiter-server/src/errors.rs

@@ -1,24 +0,0 @@
-use tonic::Status;
-use tracing::error;
-
-pub trait GrpcStatusExt<T> {
-    fn to_status(self) -> Result<T, Status>;
-}
-
-impl<T> GrpcStatusExt<T> for Result<T, diesel::result::Error> {
-    fn to_status(self) -> Result<T, Status> {
-         self.map_err(|e| {
-            error!(error = ?e, "Database error");
-            Status::internal("Database error")
-        })
-    }
-}
-
-impl<T> GrpcStatusExt<T> for Result<T, crate::db::PoolError> {
-    fn to_status(self) -> Result<T, Status> {
-        self.map_err(|e| {
-            error!(error = ?e, "Database pool error");
-            Status::internal("Database pool error")
-        })
-    }
-}

server/crates/arbiter-server/src/evm/abi.rs

@@ -0,0 +1,84 @@
+use alloy::sol;
+
+sol! {
+    interface IERC20 {
+        event Transfer(address indexed from, address indexed to, uint256 value);
+        event Approval(address indexed owner, address indexed spender, uint256 value);
+
+        function totalSupply() external view returns (uint256);
+        function balanceOf(address account) external view returns (uint256);
+        function transfer(address to, uint256 value) external returns (bool);
+        function allowance(address owner, address spender) external view returns (uint256);
+        function approve(address spender, uint256 value) external returns (bool);
+        function transferFrom(address from, address to, uint256 value) external returns (bool);
+    }
+}
+
+sol! {
+    /// ERC-721: Non-Fungible Token Standard.
+    #[derive(Debug)]
+    interface IERC721 {
+        event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
+        event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
+        event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
+
+        function balanceOf(address owner) external view returns (uint256 balance);
+        function ownerOf(uint256 tokenId) external view returns (address owner);
+        function safeTransferFrom(address from, address to, uint256 tokenId) external;
+        function safeTransferFrom(address from, address to, uint256 tokenId, bytes calldata data) external;
+        function transferFrom(address from, address to, uint256 tokenId) external;
+        function approve(address to, uint256 tokenId) external;
+        function setApprovalForAll(address operator, bool approved) external;
+        function getApproved(uint256 tokenId) external view returns (address operator);
+        function isApprovedForAll(address owner, address operator) external view returns (bool);
+    }
+}
+
+sol! {
+    /// Wrapped Ether — the only functions beyond ERC-20 that matter.
+    #[derive(Debug)]
+    interface IWETH {
+        function deposit() external payable;
+        function withdraw(uint256 wad) external;
+    }
+}
+
+sol! {
+    /// Permit2 — Uniswap's canonical token approval manager.
+    /// Replaces per-contract ERC-20 approve() with a single approval hub.
+    #[derive(Debug)]
+    interface IPermit2 {
+        struct TokenPermissions {
+            address token;
+            uint256 amount;
+        }
+
+        struct PermitSingle {
+            TokenPermissions details;
+            address spender;
+            uint256 sigDeadline;
+        }
+
+        struct PermitBatch {
+            TokenPermissions[] details;
+            address spender;
+            uint256 sigDeadline;
+        }
+
+        struct AllowanceTransferDetails {
+            address from;
+            address to;
+            uint160 amount;
+            address token;
+        }
+
+        function approve(address token, address spender, uint160 amount, uint48 expiration) external;
+        function permit(address owner, PermitSingle calldata permitSingle, bytes calldata signature) external;
+        function permit(address owner, PermitBatch calldata permitBatch, bytes calldata signature) external;
+        function transferFrom(address from, address to, uint160 amount, address token) external;
+        function transferFrom(AllowanceTransferDetails[] calldata transferDetails) external;
+
+        function allowance(address user, address token, address spender)
+            external view returns (uint160 amount, uint48 expiration, uint48 nonce);
+    }
+}

server/crates/arbiter-server/src/evm/mod.rs

@@ -0,0 +1,340 @@
+pub mod abi;
+pub mod safe_signer;
+
+use alloy::{
+    consensus::TxEip1559,
+    primitives::{TxKind, U256},
+};
+use chrono::Utc;
+use diesel::{ExpressionMethods as _, QueryDsl, QueryResult, insert_into, sqlite::Sqlite};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::{
+    db::{
+        self,
+        models::{EvmBasicGrant, NewEvmBasicGrant, NewEvmTransactionLog, SqliteTimestamp},
+        schema::{self, evm_transaction_log},
+    },
+    evm::policies::{
+        DatabaseID, EvalContext, EvalViolation, FullGrant, Grant, Policy, SharedGrantSettings,
+        SpecificGrant, SpecificMeaning, ether_transfer::EtherTransfer,
+        token_transfers::TokenTransfer,
+    },
+};
+
+pub mod policies;
+mod utils;
+
+/// Errors that can only occur once the transaction meaning is known (during policy evaluation)
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum PolicyError {
+    #[error("Database connection pool error")]
+    #[diagnostic(code(arbiter_server::evm::policy_error::pool))]
+    Pool(#[from] db::PoolError),
+    #[error("Database returned error")]
+    #[diagnostic(code(arbiter_server::evm::policy_error::database))]
+    Database(#[from] diesel::result::Error),
+    #[error("Transaction violates policy: {0:?}")]
+    #[diagnostic(code(arbiter_server::evm::policy_error::violation))]
+    Violations(Vec<EvalViolation>),
+    #[error("No matching grant found")]
+    #[diagnostic(code(arbiter_server::evm::policy_error::no_matching_grant))]
+    NoMatchingGrant,
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum VetError {
+    #[error("Contract creation transactions are not supported")]
+    #[diagnostic(code(arbiter_server::evm::vet_error::contract_creation_unsupported))]
+    ContractCreationNotSupported,
+    #[error("Engine can't classify this transaction")]
+    #[diagnostic(code(arbiter_server::evm::vet_error::unsupported))]
+    UnsupportedTransactionType,
+    #[error("Policy evaluation failed: {1}")]
+    #[diagnostic(code(arbiter_server::evm::vet_error::evaluated))]
+    Evaluated(SpecificMeaning, #[source] PolicyError),
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum SignError {
+    #[error("Database connection pool error")]
+    #[diagnostic(code(arbiter_server::evm::database_error))]
+    Pool(#[from] db::PoolError),
+    #[error("Database returned error")]
+    #[diagnostic(code(arbiter_server::evm::database_error))]
+    Database(#[from] diesel::result::Error),
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum AnalyzeError {
+    #[error("Engine doesn't support granting permissions for contract creation")]
+    #[diagnostic(code(arbiter_server::evm::analyze_error::contract_creation_not_supported))]
+    ContractCreationNotSupported,
+
+    #[error("Unsupported transaction type")]
+    #[diagnostic(code(arbiter_server::evm::analyze_error::unsupported_transaction_type))]
+    UnsupportedTransactionType,
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum CreationError {
+    #[error("Database connection pool error")]
+    #[diagnostic(code(arbiter_server::evm::creation_error::database_error))]
+    Pool(#[from] db::PoolError),
+
+    #[error("Database returned error")]
+    #[diagnostic(code(arbiter_server::evm::creation_error::database_error))]
+    Database(#[from] diesel::result::Error),
+}
+
+#[derive(Debug, thiserror::Error, miette::Diagnostic)]
+pub enum ListGrantsError {
+    #[error("Database connection pool error")]
+    #[diagnostic(code(arbiter_server::evm::list_grants_error::pool))]
+    Pool(#[from] db::PoolError),
+
+    #[error("Database returned error")]
+    #[diagnostic(code(arbiter_server::evm::list_grants_error::database))]
+    Database(#[from] diesel::result::Error),
+}
+
+/// Controls whether a transaction should be executed or only validated
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RunKind {
+    /// Validate and record the transaction
+    Execution,
+    /// Validate only, do not record
+    CheckOnly,
+}
+
+async fn check_shared_constraints(
+    context: &EvalContext,
+    shared: &SharedGrantSettings,
+    shared_grant_id: DatabaseID,
+    conn: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+    let now = Utc::now();
+
+    // Validity window
+    if shared.valid_from.is_some_and(|t| now < t)
+        || shared.valid_until.is_some_and(|t| now > t)
+    {
+        violations.push(EvalViolation::InvalidTime);
+    }
+
+    // Gas fee caps
+    let fee_exceeded = shared
+        .max_gas_fee_per_gas
+        .is_some_and(|cap| U256::from(context.max_fee_per_gas) > cap);
+    let priority_exceeded = shared.max_priority_fee_per_gas.is_some_and(|cap| {
+        U256::from(context.max_priority_fee_per_gas) > cap
+    });
+    if fee_exceeded || priority_exceeded {
+        violations.push(EvalViolation::GasLimitExceeded {
+            max_gas_fee_per_gas: shared.max_gas_fee_per_gas,
+            max_priority_fee_per_gas: shared.max_priority_fee_per_gas,
+        });
+    }
+
+    // Transaction count rate limit
+    if let Some(rate_limit) = &shared.rate_limit {
+        let window_start = SqliteTimestamp(now - rate_limit.window);
+        let count: i64 = evm_transaction_log::table
+            .filter(evm_transaction_log::grant_id.eq(shared_grant_id))
+            .filter(evm_transaction_log::signed_at.ge(window_start))
+            .count()
+            .get_result(conn)
+            .await?;
+
+        if count >= rate_limit.count as i64 {
+            violations.push(EvalViolation::RateLimitExceeded);
+        }
+    }
+
+    Ok(violations)
+}
+
+// Supporting only EIP-1559 transactions for now, but we can easily extend this to support legacy transactions if needed
+pub struct Engine {
+    db: db::DatabasePool,
+}
+
+impl Engine {
+    async fn vet_transaction<P: Policy>(
+        &self,
+        context: EvalContext,
+        meaning: &P::Meaning,
+        run_kind: RunKind,
+    ) -> Result<(), PolicyError> {
+        let mut conn = self.db.get().await?;
+
+        let grant = P::try_find_grant(&context, &mut conn)
+            .await?
+            .ok_or(PolicyError::NoMatchingGrant)?;
+
+        let mut violations =
+            check_shared_constraints(&context, &grant.shared, grant.shared_grant_id, &mut conn)
+                .await?;
+        violations.extend(P::evaluate(&context, meaning, &grant, &mut conn).await?);
+
+        if !violations.is_empty() {
+            return Err(PolicyError::Violations(violations));
+        } else if run_kind == RunKind::Execution {
+            conn.transaction(|conn| {
+                Box::pin(async move {
+                    let log_id: i32 = insert_into(evm_transaction_log::table)
+                        .values(&NewEvmTransactionLog {
+                            grant_id: grant.shared_grant_id,
+                            client_id: context.client_id,
+                            wallet_id: context.wallet_id,
+                            chain_id: context.chain as i32,
+                            eth_value: utils::u256_to_bytes(context.value).to_vec(),
+                            signed_at: Utc::now().into(),
+                        })
+                        .returning(evm_transaction_log::id)
+                        .get_result(conn)
+                        .await?;
+
+                    P::record_transaction(&context, meaning, log_id, &grant, conn).await?;
+
+                    QueryResult::Ok(())
+                })
+            })
+            .await?;
+        }
+
+        Ok(())
+    }
+}
+
+impl Engine {
+    pub fn new(db: db::DatabasePool) -> Self {
+        Self { db }
+    }
+
+    pub async fn create_grant<P: Policy>(
+        &self,
+        client_id: i32,
+        full_grant: FullGrant<P::Settings>,
+    ) -> Result<i32, CreationError> {
+        let mut conn = self.db.get().await?;
+
+        let id = conn
+            .transaction(|conn| {
+                Box::pin(async move {
+                    use schema::evm_basic_grant;
+
+                    let basic_grant: EvmBasicGrant = insert_into(evm_basic_grant::table)
+                        .values(&NewEvmBasicGrant {
+                            wallet_id: full_grant.basic.wallet_id,
+                            chain_id: full_grant.basic.chain as i32,
+                            client_id,
+                            valid_from: full_grant.basic.valid_from.map(SqliteTimestamp),
+                            valid_until: full_grant.basic.valid_until.map(SqliteTimestamp),
+                            max_gas_fee_per_gas: full_grant
+                                .basic
+                                .max_gas_fee_per_gas
+                                .map(|fee| utils::u256_to_bytes(fee).to_vec()),
+                            max_priority_fee_per_gas: full_grant
+                                .basic
+                                .max_priority_fee_per_gas
+                                .map(|fee| utils::u256_to_bytes(fee).to_vec()),
+                            rate_limit_count: full_grant
+                                .basic
+                                .rate_limit
+                                .as_ref()
+                                .map(|rl| rl.count as i32),
+                            rate_limit_window_secs: full_grant
+                                .basic
+                                .rate_limit
+                                .as_ref()
+                                .map(|rl| rl.window.num_seconds() as i32),
+                            revoked_at: None,
+                        })
+                        .returning(evm_basic_grant::all_columns)
+                        .get_result(conn)
+                        .await?;
+
+                    P::create_grant(&basic_grant, &full_grant.specific, conn).await
+                })
+            })
+            .await?;
+
+        Ok(id)
+    }
+
+    pub async fn list_all_grants(&self) -> Result<Vec<Grant<SpecificGrant>>, ListGrantsError> {
+        let mut conn = self.db.get().await?;
+
+        let mut grants: Vec<Grant<SpecificGrant>> = Vec::new();
+
+        grants.extend(
+            EtherTransfer::find_all_grants(&mut conn)
+                .await?
+                .into_iter()
+                .map(|g| Grant {
+                    id: g.id,
+                    shared_grant_id: g.shared_grant_id,
+                    shared: g.shared,
+                    settings: SpecificGrant::EtherTransfer(g.settings),
+                }),
+        );
+        grants.extend(
+            TokenTransfer::find_all_grants(&mut conn)
+                .await?
+                .into_iter()
+                .map(|g| Grant {
+                    id: g.id,
+                    shared_grant_id: g.shared_grant_id,
+                    shared: g.shared,
+                    settings: SpecificGrant::TokenTransfer(g.settings),
+                }),
+        );
+
+        Ok(grants)
+    }
+
+    pub async fn evaluate_transaction(
+        &self,
+        wallet_id: i32,
+        client_id: i32,
+        transaction: TxEip1559,
+        run_kind: RunKind,
+    ) -> Result<SpecificMeaning, VetError> {
+        let TxKind::Call(to) = transaction.to else {
+            return Err(VetError::ContractCreationNotSupported);
+        };
+        let context = policies::EvalContext {
+            wallet_id,
+            client_id,
+            chain: transaction.chain_id,
+            to,
+            value: transaction.value,
+            calldata: transaction.input.clone(),
+            max_fee_per_gas: transaction.max_fee_per_gas,
+            max_priority_fee_per_gas: transaction.max_priority_fee_per_gas,
+        };
+
+        if let Some(meaning) = EtherTransfer::analyze(&context) {
+            return match self
+                .vet_transaction::<EtherTransfer>(context, &meaning, run_kind)
+                .await
+            {
+                Ok(()) => Ok(meaning.into()),
+                Err(e) => Err(VetError::Evaluated(meaning.into(), e)),
+            };
+        }
+        if let Some(meaning) = TokenTransfer::analyze(&context) {
+            return match self
+                .vet_transaction::<TokenTransfer>(context, &meaning, run_kind)
+                .await
+            {
+                Ok(()) => Ok(meaning.into()),
+                Err(e) => Err(VetError::Evaluated(meaning.into(), e)),
+            };
+        }
+
+        Err(VetError::UnsupportedTransactionType)
+    }
+}

server/crates/arbiter-server/src/evm/policies.rs

@@ -0,0 +1,209 @@
+use std::fmt::Display;
+
+use alloy::primitives::{Address, Bytes, ChainId, U256};
+use chrono::{DateTime, Duration, Utc};
+use diesel::{
+    ExpressionMethods as _, QueryDsl, SelectableHelper, result::QueryResult, sqlite::Sqlite,
+};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+use miette::Diagnostic;
+use thiserror::Error;
+
+use crate::{
+    db::models::{self, EvmBasicGrant},
+    evm::utils,
+};
+
+pub mod ether_transfer;
+pub mod token_transfers;
+
+#[derive(Debug, Clone)]
+pub struct EvalContext {
+    // Which wallet is this transaction for
+    pub client_id: i32,
+    pub wallet_id: i32,
+
+    // The transaction data
+    pub chain: ChainId,
+    pub to: Address,
+    pub value: U256,
+    pub calldata: Bytes,
+
+    // Gas pricing (EIP-1559)
+    pub max_fee_per_gas: u128,
+    pub max_priority_fee_per_gas: u128,
+}
+
+#[derive(Debug, Error, Diagnostic)]
+pub enum EvalViolation {
+    #[error("This grant doesn't allow transactions to the target address {target}")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::invalid_target))]
+    InvalidTarget { target: Address },
+
+    #[error("Gas limit exceeded for this grant")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::gas_limit_exceeded))]
+    GasLimitExceeded {
+        max_gas_fee_per_gas: Option<U256>,
+        max_priority_fee_per_gas: Option<U256>,
+    },
+
+    #[error("Rate limit exceeded for this grant")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::rate_limit_exceeded))]
+    RateLimitExceeded,
+
+    #[error("Transaction exceeds volumetric limits of the grant")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::volumetric_limit_exceeded))]
+    VolumetricLimitExceeded,
+
+    #[error("Transaction is outside of the grant's validity period")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::invalid_time))]
+    InvalidTime,
+
+    #[error("Transaction type is not allowed by this grant")]
+    #[diagnostic(code(arbiter_server::evm::eval_violation::invalid_transaction_type))]
+    InvalidTransactionType,
+}
+
+pub type DatabaseID = i32;
+
+pub struct Grant<PolicySettings> {
+    pub id: DatabaseID,
+    pub shared_grant_id: DatabaseID, // ID of the basic grant for shared-logic checks like rate limits and validity periods
+    pub shared: SharedGrantSettings,
+    pub settings: PolicySettings,
+}
+
+
+pub trait Policy: Sized {
+    type Settings: Send + Sync + 'static + Into<SpecificGrant>;
+    type Meaning: Display + std::fmt::Debug + Send + Sync + 'static + Into<SpecificMeaning>;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning>;
+
+    // Evaluate whether a transaction with the given meaning complies with the provided grant, and return any violations if not
+    // Empty vector means transaction is compliant with the grant
+    fn evaluate(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Vec<EvalViolation>>> + Send;
+
+    // Create a new grant in the database based on the provided grant details, and return its ID
+    fn create_grant(
+        basic: &models::EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl std::future::Future<Output = QueryResult<DatabaseID>> + Send;
+
+    // Try to find an existing grant that matches the transaction context, and return its details if found
+    // Additionally, return ID of basic grant for shared-logic checks like rate limits and validity periods
+    fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Option<Grant<Self::Settings>>>> + Send;
+
+    // Return all non-revoked grants, eagerly loading policy-specific settings
+    fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<Vec<Grant<Self::Settings>>>> + Send;
+
+    // Records, updates or deletes rate limits
+    // In other words, records grant-specific things after transaction is executed
+    fn record_transaction(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        log_id: i32,
+        grant: &Grant<Self::Settings>,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<()>> + Send;
+}
+
+pub enum ReceiverTarget {
+    Specific(Vec<Address>), // only allow transfers to these addresses
+    Any,                    // allow transfers to any address
+}
+
+// Classification of what transaction does
+#[derive(Debug)]
+pub enum SpecificMeaning {
+    EtherTransfer(ether_transfer::Meaning),
+    TokenTransfer(token_transfers::Meaning),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TransactionRateLimit {
+    pub count: u32,
+    pub window: Duration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct VolumeRateLimit {
+    pub max_volume: U256,
+    pub window: Duration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct SharedGrantSettings {
+    pub wallet_id: i32,
+    pub chain: ChainId,
+
+    pub valid_from: Option<DateTime<Utc>>,
+    pub valid_until: Option<DateTime<Utc>>,
+
+    pub max_gas_fee_per_gas: Option<U256>,
+    pub max_priority_fee_per_gas: Option<U256>,
+
+    pub rate_limit: Option<TransactionRateLimit>,
+}
+
+impl SharedGrantSettings {
+    fn try_from_model(model: EvmBasicGrant) -> QueryResult<Self> {
+        Ok(Self {
+            wallet_id: model.wallet_id,
+            chain: model.chain_id as u64, // safe because chain_id is stored as i32 but is guaranteed to be a valid ChainId by the API when creating grants
+            valid_from: model.valid_from.map(Into::into),
+            valid_until: model.valid_until.map(Into::into),
+            max_gas_fee_per_gas: model
+                .max_gas_fee_per_gas
+                .map(|b| utils::try_bytes_to_u256(&b))
+                .transpose()?,
+            max_priority_fee_per_gas: model
+                .max_priority_fee_per_gas
+                .map(|b| utils::try_bytes_to_u256(&b))
+                .transpose()?,
+            rate_limit: match (model.rate_limit_count, model.rate_limit_window_secs) {
+                (Some(count), Some(window_secs)) => Some(TransactionRateLimit {
+                    count: count as u32,
+                    window: Duration::seconds(window_secs as i64),
+                }),
+                _ => None,
+            },
+        })
+    }
+
+    pub async fn query_by_id(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+        id: i32,
+    ) -> diesel::result::QueryResult<Self> {
+        use crate::db::schema::evm_basic_grant;
+
+        let basic_grant: EvmBasicGrant = evm_basic_grant::table
+            .select(EvmBasicGrant::as_select())
+            .filter(evm_basic_grant::id.eq(id))
+            .first::<EvmBasicGrant>(conn)
+            .await?;
+
+        Self::try_from_model(basic_grant)
+    }
+}
+
+pub enum SpecificGrant {
+    EtherTransfer(ether_transfer::Settings),
+    TokenTransfer(token_transfers::Settings),
+}
+
+pub struct FullGrant<PolicyGrant> {
+    pub basic: SharedGrantSettings,
+    pub specific: PolicyGrant,
+}

server/crates/arbiter-server/src/evm/policies/ether_transfer/mod.rs

@@ -0,0 +1,347 @@
+use std::collections::HashMap;
+use std::fmt::Display;
+
+use alloy::primitives::{Address, U256};
+use chrono::{DateTime, Duration, Utc};
+use diesel::dsl::{auto_type, insert_into};
+use diesel::sqlite::Sqlite;
+use diesel::{ExpressionMethods, JoinOnDsl, prelude::*};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::db::models::{
+    EvmBasicGrant, EvmEtherTransferGrant, EvmEtherTransferGrantTarget, EvmEtherTransferLimit,
+    NewEvmEtherTransferLimit, SqliteTimestamp,
+};
+use crate::db::schema::{evm_basic_grant, evm_ether_transfer_limit, evm_transaction_log};
+use crate::evm::policies::{
+    Grant, SharedGrantSettings, SpecificGrant, SpecificMeaning, VolumeRateLimit,
+};
+use crate::{
+    db::{
+        models::{self, NewEvmEtherTransferGrant, NewEvmEtherTransferGrantTarget},
+        schema::{evm_ether_transfer_grant, evm_ether_transfer_grant_target},
+    },
+    evm::{policies::Policy, utils},
+};
+
+#[auto_type]
+fn grant_join() -> _ {
+    evm_ether_transfer_grant::table.inner_join(
+        evm_basic_grant::table.on(evm_ether_transfer_grant::basic_grant_id.eq(evm_basic_grant::id)),
+    )
+}
+
+use super::{DatabaseID, EvalContext, EvalViolation};
+
+// Plain ether transfer
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Meaning {
+    to: Address,
+    value: U256,
+}
+impl Display for Meaning {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Ether transfer of {} to {}", self.value, self.to)
+    }
+}
+impl From<Meaning> for SpecificMeaning {
+    fn from(val: Meaning) -> SpecificMeaning {
+        SpecificMeaning::EtherTransfer(val)
+    }
+}
+
+// A grant for ether transfers, which can be scoped to specific target addresses and volume limits
+pub struct Settings {
+    target: Vec<Address>,
+    limit: VolumeRateLimit,
+}
+
+impl From<Settings> for SpecificGrant {
+    fn from(val: Settings) -> SpecificGrant {
+        SpecificGrant::EtherTransfer(val)
+    }
+}
+
+async fn query_relevant_past_transaction(
+    grant_id: i32,
+    longest_window: Duration,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<(U256, DateTime<Utc>)>> {
+    let past_transactions: Vec<(Vec<u8>, SqliteTimestamp)> = evm_transaction_log::table
+        .filter(evm_transaction_log::grant_id.eq(grant_id))
+        .filter(
+            evm_transaction_log::signed_at.ge(SqliteTimestamp(chrono::Utc::now() - longest_window)),
+        )
+        .select((
+            evm_transaction_log::eth_value,
+            evm_transaction_log::signed_at,
+        ))
+        .load(db)
+        .await?;
+    let past_transaction: Vec<(U256, DateTime<Utc>)> = past_transactions
+        .into_iter()
+        .filter_map(|(value_bytes, timestamp)| {
+            let value = utils::bytes_to_u256(&value_bytes)?;
+            Some((value, timestamp.0))
+        })
+        .collect();
+    Ok(past_transaction)
+}
+
+async fn check_rate_limits(
+    grant: &Grant<Settings>,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+    let window = grant.settings.limit.window;
+
+    let past_transaction = query_relevant_past_transaction(grant.id, window, db).await?;
+
+    let window_start = chrono::Utc::now() - grant.settings.limit.window;
+    let cumulative_volume: U256 = past_transaction
+        .iter()
+        .filter(|(_, timestamp)| timestamp >= &window_start)
+        .fold(U256::default(), |acc, (value, _)| acc + *value);
+
+    if cumulative_volume > grant.settings.limit.max_volume {
+        violations.push(EvalViolation::VolumetricLimitExceeded);
+    }
+
+    Ok(violations)
+}
+
+pub struct EtherTransfer;
+impl Policy for EtherTransfer {
+    type Settings = Settings;
+
+    type Meaning = Meaning;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning> {
+        if !context.calldata.is_empty() {
+            return None;
+        }
+
+        Some(Meaning {
+            to: context.to,
+            value: context.value,
+        })
+    }
+
+    async fn evaluate(
+        _: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<EvalViolation>> {
+        let mut violations = Vec::new();
+
+        // Check if the target address is within the grant's allowed targets
+        if !grant.settings.target.contains(&meaning.to) {
+            violations.push(EvalViolation::InvalidTarget { target: meaning.to });
+        }
+
+        let rate_violations = check_rate_limits(grant, db).await?;
+        violations.extend(rate_violations);
+
+        Ok(violations)
+    }
+
+    async fn create_grant(
+        basic: &models::EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<DatabaseID> {
+        let limit_id: i32 = insert_into(evm_ether_transfer_limit::table)
+            .values(NewEvmEtherTransferLimit {
+                window_secs: grant.limit.window.num_seconds() as i32,
+                max_volume: utils::u256_to_bytes(grant.limit.max_volume).to_vec(),
+            })
+            .returning(evm_ether_transfer_limit::id)
+            .get_result(conn)
+            .await?;
+
+        let grant_id: i32 = insert_into(evm_ether_transfer_grant::table)
+            .values(&NewEvmEtherTransferGrant {
+                basic_grant_id: basic.id,
+                limit_id,
+            })
+            .returning(evm_ether_transfer_grant::id)
+            .get_result(conn)
+            .await?;
+
+        for target in &grant.target {
+            insert_into(evm_ether_transfer_grant_target::table)
+                .values(NewEvmEtherTransferGrantTarget {
+                    grant_id,
+                    address: target.to_vec(),
+                })
+                .execute(conn)
+                .await?;
+        }
+
+        Ok(grant_id)
+    }
+
+    async fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<Option<Grant<Self::Settings>>> {
+        let target_bytes = context.to.to_vec();
+
+        // Find a grant where:
+        // 1. The basic grant's wallet_id and client_id match the context
+        // 2. Any of the grant's targets match the context's `to` address
+        let grant: Option<(EvmBasicGrant, EvmEtherTransferGrant)> = evm_ether_transfer_grant::table
+            .inner_join(evm_basic_grant::table)
+            .inner_join(evm_ether_transfer_grant_target::table)
+            .filter(
+                evm_basic_grant::wallet_id
+                    .eq(context.wallet_id)
+                    .and(evm_basic_grant::client_id.eq(context.client_id))
+                    .and(evm_basic_grant::revoked_at.is_null())
+                    .and(evm_ether_transfer_grant_target::address.eq(&target_bytes)),
+            )
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmEtherTransferGrant::as_select(),
+            ))
+            .first(conn)
+            .await
+            .optional()?;
+
+        let Some((basic_grant, grant)) = grant else {
+            return Ok(None);
+        };
+
+        let target_bytes: Vec<EvmEtherTransferGrantTarget> = evm_ether_transfer_grant_target::table
+            .select(EvmEtherTransferGrantTarget::as_select())
+            .filter(evm_ether_transfer_grant_target::grant_id.eq(grant.id))
+            .load(conn)
+            .await?;
+
+        let limit: EvmEtherTransferLimit = evm_ether_transfer_limit::table
+            .filter(evm_ether_transfer_limit::id.eq(grant.limit_id))
+            .select(EvmEtherTransferLimit::as_select())
+            .first::<EvmEtherTransferLimit>(conn)
+            .await?;
+
+        // Convert bytes back to Address
+        let targets: Vec<Address> = target_bytes
+            .into_iter()
+            .filter_map(|target| {
+                // TODO: Handle invalid addresses more gracefully
+                let arr: [u8; 20] = target.address.try_into().ok()?;
+                Some(Address::from(arr))
+            })
+            .collect();
+
+        let settings = Settings {
+            target: targets,
+            limit: VolumeRateLimit {
+                max_volume: utils::try_bytes_to_u256(&limit.max_volume)
+                    .map_err(|err| diesel::result::Error::DeserializationError(Box::new(err)))?,
+                window: chrono::Duration::seconds(limit.window_secs as i64),
+            },
+        };
+
+        Ok(Some(Grant {
+            id: grant.id,
+            shared_grant_id: grant.basic_grant_id,
+            shared: SharedGrantSettings::try_from_model(basic_grant)?,
+            settings,
+        }))
+    }
+
+    async fn record_transaction(
+        _context: &EvalContext,
+        _: &Self::Meaning,
+        _log_id: i32,
+        _grant: &Grant<Self::Settings>,
+        _conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> diesel::result::QueryResult<()> {
+        // Basic log is sufficient
+
+        Ok(())
+    }
+
+    async fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<Grant<Self::Settings>>> {
+        let grants: Vec<(EvmBasicGrant, EvmEtherTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmEtherTransferGrant::as_select(),
+            ))
+            .load(conn)
+            .await?;
+
+        if grants.is_empty() {
+            return Ok(Vec::new());
+        }
+
+        let grant_ids: Vec<i32> = grants.iter().map(|(_, g)| g.id).collect();
+        let limit_ids: Vec<i32> = grants.iter().map(|(_, g)| g.limit_id).collect();
+
+        let all_targets: Vec<EvmEtherTransferGrantTarget> = evm_ether_transfer_grant_target::table
+            .filter(evm_ether_transfer_grant_target::grant_id.eq_any(&grant_ids))
+            .select(EvmEtherTransferGrantTarget::as_select())
+            .load(conn)
+            .await?;
+
+        let all_limits: Vec<EvmEtherTransferLimit> = evm_ether_transfer_limit::table
+            .filter(evm_ether_transfer_limit::id.eq_any(&limit_ids))
+            .select(EvmEtherTransferLimit::as_select())
+            .load(conn)
+            .await?;
+
+        let mut targets_by_grant: HashMap<i32, Vec<EvmEtherTransferGrantTarget>> = HashMap::new();
+        for target in all_targets {
+            targets_by_grant
+                .entry(target.grant_id)
+                .or_default()
+                .push(target);
+        }
+
+        let limits_by_id: HashMap<i32, EvmEtherTransferLimit> =
+            all_limits.into_iter().map(|l| (l.id, l)).collect();
+
+        grants
+            .into_iter()
+            .map(|(basic, specific)| {
+                let targets: Vec<Address> = targets_by_grant
+                    .get(&specific.id)
+                    .map(|v| v.as_slice())
+                    .unwrap_or_default()
+                    .iter()
+                    .filter_map(|t| {
+                        let arr: [u8; 20] = t.address.clone().try_into().ok()?;
+                        Some(Address::from(arr))
+                    })
+                    .collect();
+
+                let limit = limits_by_id
+                    .get(&specific.limit_id)
+                    .ok_or(diesel::result::Error::NotFound)?;
+
+                Ok(Grant {
+                    id: specific.id,
+                    shared_grant_id: specific.basic_grant_id,
+                    shared: SharedGrantSettings::try_from_model(basic)?,
+                    settings: Settings {
+                        target: targets,
+                        limit: VolumeRateLimit {
+                            max_volume: utils::try_bytes_to_u256(&limit.max_volume).map_err(
+                                |e| diesel::result::Error::DeserializationError(Box::new(e)),
+                            )?,
+                            window: Duration::seconds(limit.window_secs as i64),
+                        },
+                    },
+                })
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests;

server/crates/arbiter-server/src/evm/policies/ether_transfer/tests.rs

@@ -0,0 +1,387 @@
+use alloy::primitives::{Address, Bytes, U256, address};
+use chrono::{Duration, Utc};
+use diesel::{SelectableHelper, insert_into};
+use diesel_async::RunQueryDsl;
+
+use crate::db::{
+    self, DatabaseConnection,
+    models::{EvmBasicGrant, NewEvmBasicGrant, NewEvmTransactionLog, SqliteTimestamp},
+    schema::{evm_basic_grant, evm_transaction_log},
+};
+use crate::evm::{
+    policies::{
+        EvalContext, EvalViolation, Grant, Policy, SharedGrantSettings, VolumeRateLimit,
+    },
+    utils,
+};
+
+use super::{EtherTransfer, Settings};
+
+const WALLET_ID: i32 = 1;
+const CLIENT_ID: i32 = 2;
+const CHAIN_ID: u64 = 1;
+
+const ALLOWED: Address = address!("1111111111111111111111111111111111111111");
+const OTHER: Address = address!("2222222222222222222222222222222222222222");
+
+fn ctx(to: Address, value: U256) -> EvalContext {
+    EvalContext {
+        wallet_id: WALLET_ID,
+        client_id: CLIENT_ID,
+        chain: CHAIN_ID,
+        to,
+        value,
+        calldata: Bytes::new(),
+        max_fee_per_gas: 0,
+        max_priority_fee_per_gas: 0,
+    }
+}
+
+async fn insert_basic(conn: &mut DatabaseConnection, revoked: bool) -> EvmBasicGrant {
+    insert_into(evm_basic_grant::table)
+        .values(NewEvmBasicGrant {
+            wallet_id: WALLET_ID,
+            client_id: CLIENT_ID,
+            chain_id: CHAIN_ID as i32,
+            valid_from: None,
+            valid_until: None,
+            max_gas_fee_per_gas: None,
+            max_priority_fee_per_gas: None,
+            rate_limit_count: None,
+            rate_limit_window_secs: None,
+            revoked_at: revoked.then(|| SqliteTimestamp(Utc::now())),
+        })
+        .returning(EvmBasicGrant::as_select())
+        .get_result(conn)
+        .await
+        .unwrap()
+}
+
+fn make_settings(targets: Vec<Address>, max_volume: u64) -> Settings {
+    Settings {
+        target: targets,
+        limit: VolumeRateLimit {
+            max_volume: U256::from(max_volume),
+            window: Duration::hours(1),
+        },
+    }
+}
+
+fn shared() -> SharedGrantSettings {
+    SharedGrantSettings {
+        wallet_id: WALLET_ID,
+        chain: CHAIN_ID,
+        valid_from: None,
+        valid_until: None,
+        max_gas_fee_per_gas: None,
+        max_priority_fee_per_gas: None,
+        rate_limit: None,
+    }
+}
+
+// ── analyze ─────────────────────────────────────────────────────────────
+
+#[test]
+fn analyze_matches_empty_calldata() {
+    let m = EtherTransfer::analyze(&ctx(ALLOWED, U256::from(1_000u64))).unwrap();
+    assert_eq!(m.to, ALLOWED);
+    assert_eq!(m.value, U256::from(1_000u64));
+}
+
+#[test]
+fn analyze_rejects_nonempty_calldata() {
+    let context = EvalContext {
+        calldata: Bytes::from(vec![0xde, 0xad, 0xbe, 0xef]),
+        ..ctx(ALLOWED, U256::from(1u64))
+    };
+    assert!(EtherTransfer::analyze(&context).is_none());
+}
+
+// ── evaluate ────────────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn evaluate_passes_for_allowed_target() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(vec![ALLOWED], 1_000_000),
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_rejects_disallowed_target() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(vec![ALLOWED], 1_000_000),
+    };
+    let context = ctx(OTHER, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::InvalidTarget { .. }))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_when_volume_within_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            client_id: CLIENT_ID,
+            wallet_id: WALLET_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(500u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_rejects_volume_over_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            client_id: CLIENT_ID,
+            wallet_id: WALLET_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(1_001u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+#[tokio::test]
+async fn evaluate_passes_at_exactly_volume_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000);
+    let grant_id = EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    // Exactly at the limit — the check is `>`, so this should not violate
+    insert_into(evm_transaction_log::table)
+        .values(NewEvmTransactionLog {
+            grant_id,
+            client_id: CLIENT_ID,
+            wallet_id: WALLET_ID,
+            chain_id: CHAIN_ID as i32,
+            eth_value: utils::u256_to_bytes(U256::from(1_000u64)).to_vec(),
+            signed_at: SqliteTimestamp(Utc::now()),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant {
+        id: grant_id,
+        shared_grant_id: basic.id,
+        shared: shared(),
+        settings,
+    };
+    let context = ctx(ALLOWED, U256::from(100u64));
+    let m = EtherTransfer::analyze(&context).unwrap();
+    let v = EtherTransfer::evaluate(&context, &m, &grant, &mut *conn)
+        .await
+        .unwrap();
+    assert!(
+        !v.iter()
+            .any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded))
+    );
+}
+
+// ── try_find_grant ───────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn try_find_grant_roundtrip() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(ALLOWED, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+
+    assert!(found.is_some());
+    let g = found.unwrap();
+    assert_eq!(g.settings.target, vec![ALLOWED]);
+    assert_eq!(g.settings.limit.max_volume, U256::from(1_000_000u64));
+}
+
+#[tokio::test]
+async fn try_find_grant_revoked_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, true).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(ALLOWED, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+#[tokio::test]
+async fn try_find_grant_wrong_target_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let found = EtherTransfer::try_find_grant(&ctx(OTHER, U256::from(1u64)), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+// ── find_all_grants ──────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn find_all_grants_empty_db() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert!(all.is_empty());
+}
+
+#[tokio::test]
+async fn find_all_grants_excludes_revoked() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let settings = make_settings(vec![ALLOWED], 1_000_000);
+    let active = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&active, &settings, &mut *conn)
+        .await
+        .unwrap();
+    let revoked = insert_basic(&mut conn, true).await;
+    EtherTransfer::create_grant(&revoked, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.target, vec![ALLOWED]);
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_targets() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(vec![ALLOWED, OTHER], 1_000_000);
+    EtherTransfer::create_grant(&basic, &settings, &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.target.len(), 2);
+    assert_eq!(all[0].settings.limit.max_volume, U256::from(1_000_000u64));
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_grants() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic1 = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&basic1, &make_settings(vec![ALLOWED], 500), &mut *conn)
+        .await
+        .unwrap();
+    let basic2 = insert_basic(&mut conn, false).await;
+    EtherTransfer::create_grant(&basic2, &make_settings(vec![OTHER], 1_000), &mut *conn)
+        .await
+        .unwrap();
+
+    let all = EtherTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 2);
+}

server/crates/arbiter-server/src/evm/policies/token_transfers/mod.rs

@@ -0,0 +1,385 @@
+use std::collections::HashMap;
+
+use alloy::{
+    primitives::{Address, U256},
+    sol_types::SolCall,
+};
+use arbiter_tokens_registry::evm::nonfungible::{self, TokenInfo};
+use chrono::{DateTime, Duration, Utc};
+use diesel::dsl::{auto_type, insert_into};
+use diesel::sqlite::Sqlite;
+use diesel::{ExpressionMethods, prelude::*};
+use diesel_async::{AsyncConnection, RunQueryDsl};
+
+use crate::db::models::{
+    EvmBasicGrant, EvmTokenTransferGrant, EvmTokenTransferVolumeLimit, NewEvmTokenTransferGrant,
+    NewEvmTokenTransferLog, NewEvmTokenTransferVolumeLimit, SqliteTimestamp,
+};
+use crate::db::schema::{
+    evm_basic_grant, evm_token_transfer_grant, evm_token_transfer_log,
+    evm_token_transfer_volume_limit,
+};
+use crate::evm::{
+    abi::IERC20::transferCall,
+    policies::{
+        Grant, Policy, SharedGrantSettings, SpecificGrant, SpecificMeaning, VolumeRateLimit,
+    },
+    utils,
+};
+
+use super::{DatabaseID, EvalContext, EvalViolation};
+
+#[auto_type]
+fn grant_join() -> _ {
+    evm_token_transfer_grant::table.inner_join(
+        evm_basic_grant::table.on(evm_token_transfer_grant::basic_grant_id.eq(evm_basic_grant::id)),
+    )
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Meaning {
+    token: &'static TokenInfo,
+    to: Address,
+    value: U256,
+}
+impl std::fmt::Display for Meaning {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "Transfer of {} {} to {}",
+            self.value, self.token.symbol, self.to
+        )
+    }
+}
+impl From<Meaning> for SpecificMeaning {
+    fn from(val: Meaning) -> SpecificMeaning {
+        SpecificMeaning::TokenTransfer(val)
+    }
+}
+
+// A grant for token transfers, which can be scoped to specific target addresses and volume limits
+pub struct Settings {
+    token_contract: Address,
+    target: Option<Address>,
+    volume_limits: Vec<VolumeRateLimit>,
+}
+impl From<Settings> for SpecificGrant {
+    fn from(val: Settings) -> SpecificGrant {
+        SpecificGrant::TokenTransfer(val)
+    }
+}
+
+async fn query_relevant_past_transfers(
+    grant_id: i32,
+    longest_window: Duration,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<(U256, DateTime<Utc>)>> {
+    let past_logs: Vec<(Vec<u8>, SqliteTimestamp)> = evm_token_transfer_log::table
+        .filter(evm_token_transfer_log::grant_id.eq(grant_id))
+        .filter(
+            evm_token_transfer_log::created_at
+                .ge(SqliteTimestamp(chrono::Utc::now() - longest_window)),
+        )
+        .select((
+            evm_token_transfer_log::value,
+            evm_token_transfer_log::created_at,
+        ))
+        .load(db)
+        .await?;
+
+    let past_transfers: Vec<(U256, DateTime<Utc>)> = past_logs
+        .into_iter()
+        .filter_map(|(value_bytes, timestamp)| {
+            let value = utils::bytes_to_u256(&value_bytes)?;
+            Some((value, timestamp.0))
+        })
+        .collect();
+
+    Ok(past_transfers)
+}
+
+async fn check_volume_rate_limits(
+    grant: &Grant<Settings>,
+    db: &mut impl AsyncConnection<Backend = Sqlite>,
+) -> QueryResult<Vec<EvalViolation>> {
+    let mut violations = Vec::new();
+
+    let Some(longest_window) = grant.settings.volume_limits.iter().map(|l| l.window).max() else {
+        return Ok(violations);
+    };
+
+    let past_transfers = query_relevant_past_transfers(grant.id, longest_window, db).await?;
+
+    for limit in &grant.settings.volume_limits {
+        let window_start = chrono::Utc::now() - limit.window;
+        let cumulative_volume: U256 = past_transfers
+            .iter()
+            .filter(|(_, timestamp)| timestamp >= &window_start)
+            .fold(U256::default(), |acc, (value, _)| acc + *value);
+
+        if cumulative_volume > limit.max_volume {
+            violations.push(EvalViolation::VolumetricLimitExceeded);
+            break;
+        }
+    }
+
+    Ok(violations)
+}
+
+pub struct TokenTransfer;
+impl Policy for TokenTransfer {
+    type Settings = Settings;
+    type Meaning = Meaning;
+
+    fn analyze(context: &EvalContext) -> Option<Self::Meaning> {
+        let token = nonfungible::get_token(context.chain, context.to)?;
+        let decoded = transferCall::abi_decode_raw_validate(&context.calldata).ok()?;
+
+        Some(Meaning {
+            token,
+            to: decoded.to,
+            value: decoded.value,
+        })
+    }
+
+    async fn evaluate(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        grant: &Grant<Self::Settings>,
+        db: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<EvalViolation>> {
+        let mut violations = Vec::new();
+
+        // erc20 transfer shouldn't carry eth value
+        if !context.value.is_zero() {
+            violations.push(EvalViolation::InvalidTransactionType);
+            return Ok(violations);
+        }
+
+        if let Some(allowed) = grant.settings.target
+            && allowed != meaning.to
+        {
+            violations.push(EvalViolation::InvalidTarget { target: meaning.to });
+        }
+
+        let rate_violations = check_volume_rate_limits(grant, db).await?;
+        violations.extend(rate_violations);
+
+        Ok(violations)
+    }
+
+    async fn create_grant(
+        basic: &EvmBasicGrant,
+        grant: &Self::Settings,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<DatabaseID> {
+        // Store the specific receiver as bytes (None means any receiver is allowed)
+        let receiver: Option<Vec<u8>> = grant.target.map(|addr| addr.to_vec());
+
+        let grant_id: i32 = insert_into(evm_token_transfer_grant::table)
+            .values(NewEvmTokenTransferGrant {
+                basic_grant_id: basic.id,
+                token_contract: grant.token_contract.to_vec(),
+                receiver,
+            })
+            .returning(evm_token_transfer_grant::id)
+            .get_result(conn)
+            .await?;
+
+        for limit in &grant.volume_limits {
+            insert_into(evm_token_transfer_volume_limit::table)
+                .values(NewEvmTokenTransferVolumeLimit {
+                    grant_id,
+                    window_secs: limit.window.num_seconds() as i32,
+                    max_volume: utils::u256_to_bytes(limit.max_volume).to_vec(),
+                })
+                .execute(conn)
+                .await?;
+        }
+
+        Ok(grant_id)
+    }
+
+    async fn try_find_grant(
+        context: &EvalContext,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Option<Grant<Self::Settings>>> {
+        let token_contract_bytes = context.to.to_vec();
+
+        let grant: Option<(EvmBasicGrant, EvmTokenTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .filter(evm_basic_grant::wallet_id.eq(context.wallet_id))
+            .filter(evm_basic_grant::client_id.eq(context.client_id))
+            .filter(evm_token_transfer_grant::token_contract.eq(&token_contract_bytes))
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmTokenTransferGrant::as_select(),
+            ))
+            .first(conn)
+            .await
+            .optional()?;
+
+        let Some((basic_grant, token_grant)) = grant else {
+            return Ok(None);
+        };
+
+        let volume_limits_db: Vec<EvmTokenTransferVolumeLimit> =
+            evm_token_transfer_volume_limit::table
+                .filter(evm_token_transfer_volume_limit::grant_id.eq(token_grant.id))
+                .select(EvmTokenTransferVolumeLimit::as_select())
+                .load(conn)
+                .await?;
+
+        let volume_limits: Vec<VolumeRateLimit> = volume_limits_db
+            .into_iter()
+            .map(|row| {
+                Ok(VolumeRateLimit {
+                    max_volume: utils::try_bytes_to_u256(&row.max_volume).map_err(|err| {
+                        diesel::result::Error::DeserializationError(Box::new(err))
+                    })?,
+                    window: Duration::seconds(row.window_secs as i64),
+                })
+            })
+            .collect::<QueryResult<Vec<_>>>()?;
+
+        let token_contract: [u8; 20] = token_grant.token_contract.try_into().map_err(|_| {
+            diesel::result::Error::DeserializationError(
+                "Invalid token contract address length".into(),
+            )
+        })?;
+
+        let target: Option<Address> = match token_grant.receiver {
+            None => None,
+            Some(bytes) => {
+                let arr: [u8; 20] = bytes.try_into().map_err(|_| {
+                    diesel::result::Error::DeserializationError(
+                        "Invalid receiver address length".into(),
+                    )
+                })?;
+                Some(Address::from(arr))
+            }
+        };
+
+        let settings = Settings {
+            token_contract: Address::from(token_contract),
+            target,
+            volume_limits,
+        };
+
+        Ok(Some(Grant {
+            id: token_grant.id,
+            shared_grant_id: token_grant.basic_grant_id,
+            shared: SharedGrantSettings::try_from_model(basic_grant)?,
+            settings,
+        }))
+    }
+
+    async fn record_transaction(
+        context: &EvalContext,
+        meaning: &Self::Meaning,
+        log_id: i32,
+        grant: &Grant<Self::Settings>,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<()> {
+        insert_into(evm_token_transfer_log::table)
+            .values(NewEvmTokenTransferLog {
+                grant_id: grant.id,
+                log_id,
+                chain_id: context.chain as i32,
+                token_contract: context.to.to_vec(),
+                recipient_address: meaning.to.to_vec(),
+                value: utils::u256_to_bytes(meaning.value).to_vec(),
+            })
+            .execute(conn)
+            .await?;
+
+        Ok(())
+    }
+
+    async fn find_all_grants(
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> QueryResult<Vec<Grant<Self::Settings>>> {
+        let grants: Vec<(EvmBasicGrant, EvmTokenTransferGrant)> = grant_join()
+            .filter(evm_basic_grant::revoked_at.is_null())
+            .select((
+                EvmBasicGrant::as_select(),
+                EvmTokenTransferGrant::as_select(),
+            ))
+            .load(conn)
+            .await?;
+
+        if grants.is_empty() {
+            return Ok(Vec::new());
+        }
+
+        let grant_ids: Vec<i32> = grants.iter().map(|(_, g)| g.id).collect();
+
+        let all_volume_limits: Vec<EvmTokenTransferVolumeLimit> =
+            evm_token_transfer_volume_limit::table
+                .filter(evm_token_transfer_volume_limit::grant_id.eq_any(&grant_ids))
+                .select(EvmTokenTransferVolumeLimit::as_select())
+                .load(conn)
+                .await?;
+
+        let mut limits_by_grant: HashMap<i32, Vec<EvmTokenTransferVolumeLimit>> = HashMap::new();
+        for limit in all_volume_limits {
+            limits_by_grant
+                .entry(limit.grant_id)
+                .or_default()
+                .push(limit);
+        }
+
+        grants
+            .into_iter()
+            .map(|(basic, specific)| {
+                let volume_limits: Vec<VolumeRateLimit> = limits_by_grant
+                    .get(&specific.id)
+                    .map(|v| v.as_slice())
+                    .unwrap_or_default()
+                    .iter()
+                    .map(|row| {
+                        Ok(VolumeRateLimit {
+                            max_volume: utils::try_bytes_to_u256(&row.max_volume).map_err(|e| {
+                                diesel::result::Error::DeserializationError(Box::new(e))
+                            })?,
+                            window: Duration::seconds(row.window_secs as i64),
+                        })
+                    })
+                    .collect::<QueryResult<Vec<_>>>()?;
+
+                let token_contract: [u8; 20] =
+                    specific.token_contract.clone().try_into().map_err(|_| {
+                        diesel::result::Error::DeserializationError(
+                            "Invalid token contract address length".into(),
+                        )
+                    })?;
+
+                let target: Option<Address> = match &specific.receiver {
+                    None => None,
+                    Some(bytes) => {
+                        let arr: [u8; 20] = bytes.clone().try_into().map_err(|_| {
+                            diesel::result::Error::DeserializationError(
+                                "Invalid receiver address length".into(),
+                            )
+                        })?;
+                        Some(Address::from(arr))
+                    }
+                };
+
+                Ok(Grant {
+                    id: specific.id,
+                    shared_grant_id: specific.basic_grant_id,
+                    shared: SharedGrantSettings::try_from_model(basic)?,
+                    settings: Settings {
+                        token_contract: Address::from(token_contract),
+                        target,
+                        volume_limits,
+                    },
+                })
+            })
+            .collect()
+    }
+}
+
+#[cfg(test)]
+mod tests;

server/crates/arbiter-server/src/evm/policies/token_transfers/tests.rs

@@ -0,0 +1,397 @@
+use alloy::primitives::{Address, Bytes, U256, address};
+use alloy::sol_types::SolCall;
+use chrono::{Duration, Utc};
+use diesel::{SelectableHelper, insert_into};
+use diesel_async::RunQueryDsl;
+
+use crate::db::{
+    self, DatabaseConnection,
+    models::{EvmBasicGrant, NewEvmBasicGrant, SqliteTimestamp},
+    schema::evm_basic_grant,
+};
+use crate::evm::{
+    abi::IERC20::transferCall,
+    policies::{EvalContext, EvalViolation, Grant, Policy, SharedGrantSettings, VolumeRateLimit},
+    utils,
+};
+
+use super::{Settings, TokenTransfer};
+
+// DAI on Ethereum mainnet — present in the static token registry
+const CHAIN_ID: u64 = 1;
+const DAI: Address = address!("6B175474E89094C44Da98b954EedeAC495271d0F");
+
+const WALLET_ID: i32 = 1;
+const CLIENT_ID: i32 = 2;
+
+const RECIPIENT: Address = address!("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
+const OTHER: Address = address!("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");
+const UNKNOWN_TOKEN: Address = address!("cccccccccccccccccccccccccccccccccccccccc");
+
+/// Encode `transfer(to, value)` raw params (no 4-byte selector).
+/// `abi_decode_raw_validate` expects exactly this format.
+fn transfer_calldata(to: Address, value: U256) -> Bytes {
+    let mut raw = Vec::new();
+    transferCall { to, value }.abi_encode_raw(&mut raw);
+    Bytes::from(raw)
+}
+
+fn ctx(to: Address, calldata: Bytes) -> EvalContext {
+    EvalContext {
+        wallet_id: WALLET_ID,
+        client_id: CLIENT_ID,
+        chain: CHAIN_ID,
+        to,
+        value: U256::ZERO,
+        calldata,
+        max_fee_per_gas: 0,
+        max_priority_fee_per_gas: 0,
+    }
+}
+
+async fn insert_basic(conn: &mut DatabaseConnection, revoked: bool) -> EvmBasicGrant {
+    insert_into(evm_basic_grant::table)
+        .values(NewEvmBasicGrant {
+            wallet_id: WALLET_ID,
+            client_id: CLIENT_ID,
+            chain_id: CHAIN_ID as i32,
+            valid_from: None,
+            valid_until: None,
+            max_gas_fee_per_gas: None,
+            max_priority_fee_per_gas: None,
+            rate_limit_count: None,
+            rate_limit_window_secs: None,
+            revoked_at: revoked.then(|| SqliteTimestamp(Utc::now())),
+        })
+        .returning(EvmBasicGrant::as_select())
+        .get_result(conn)
+        .await
+        .unwrap()
+}
+
+fn make_settings(target: Option<Address>, max_volume: Option<u64>) -> Settings {
+    Settings {
+        token_contract: DAI,
+        target,
+        volume_limits: max_volume
+            .map(|v| {
+                vec![VolumeRateLimit {
+                    max_volume: U256::from(v),
+                    window: Duration::hours(1),
+                }]
+            })
+            .unwrap_or_default(),
+    }
+}
+
+fn shared() -> SharedGrantSettings {
+    SharedGrantSettings {
+        wallet_id: WALLET_ID,
+        chain: CHAIN_ID,
+        valid_from: None,
+        valid_until: None,
+        max_gas_fee_per_gas: None,
+        max_priority_fee_per_gas: None,
+        rate_limit: None,
+    }
+}
+
+// ── analyze ─────────────────────────────────────────────────────────────
+
+#[test]
+fn analyze_known_token_valid_calldata() {
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let m = TokenTransfer::analyze(&ctx(DAI, calldata)).unwrap();
+    assert_eq!(m.to, RECIPIENT);
+    assert_eq!(m.value, U256::from(100u64));
+}
+
+#[test]
+fn analyze_unknown_token_returns_none() {
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    assert!(TokenTransfer::analyze(&ctx(UNKNOWN_TOKEN, calldata)).is_none());
+}
+
+#[test]
+fn analyze_invalid_calldata_returns_none() {
+    let calldata = Bytes::from(vec![0xde, 0xad, 0xbe, 0xef]);
+    assert!(TokenTransfer::analyze(&ctx(DAI, calldata)).is_none());
+}
+
+#[test]
+fn analyze_empty_calldata_returns_none() {
+    assert!(TokenTransfer::analyze(&ctx(DAI, Bytes::new())).is_none());
+}
+
+// ── evaluate ────────────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn evaluate_rejects_nonzero_eth_value() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let mut context = ctx(DAI, calldata);
+    context.value = U256::from(1u64); // ETH attached to an ERC-20 call
+
+    let m = TokenTransfer::analyze(&EvalContext { value: U256::ZERO, ..context.clone() })
+        .unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(v.iter().any(|e| matches!(e, EvalViolation::InvalidTransactionType)));
+}
+
+#[tokio::test]
+async fn evaluate_passes_any_recipient_when_no_restriction() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_passes_matching_restricted_recipient() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(Some(RECIPIENT), None),
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(v.is_empty());
+}
+
+#[tokio::test]
+async fn evaluate_rejects_wrong_restricted_recipient() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(Some(RECIPIENT), None),
+    };
+    let calldata = transfer_calldata(OTHER, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(v.iter().any(|e| matches!(e, EvalViolation::InvalidTarget { .. })));
+}
+
+#[tokio::test]
+async fn evaluate_passes_volume_within_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(1_000));
+    let grant_id = TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    // Record a past transfer of 500 (within 1000 limit)
+    use crate::db::{models::NewEvmTokenTransferLog, schema::evm_token_transfer_log};
+    insert_into(evm_token_transfer_log::table)
+        .values(NewEvmTokenTransferLog {
+            grant_id,
+            log_id: 0,
+            chain_id: CHAIN_ID as i32,
+            token_contract: DAI.to_vec(),
+            recipient_address: RECIPIENT.to_vec(),
+            value: utils::u256_to_bytes(U256::from(500u64)).to_vec(),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant { id: grant_id, shared_grant_id: basic.id, shared: shared(), settings };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(!v.iter().any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded)));
+}
+
+#[tokio::test]
+async fn evaluate_rejects_volume_over_limit() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(1_000));
+    let grant_id = TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    use crate::db::{models::NewEvmTokenTransferLog, schema::evm_token_transfer_log};
+    insert_into(evm_token_transfer_log::table)
+        .values(NewEvmTokenTransferLog {
+            grant_id,
+            log_id: 0,
+            chain_id: CHAIN_ID as i32,
+            token_contract: DAI.to_vec(),
+            recipient_address: RECIPIENT.to_vec(),
+            value: utils::u256_to_bytes(U256::from(1_001u64)).to_vec(),
+        })
+        .execute(&mut *conn)
+        .await
+        .unwrap();
+
+    let grant = Grant { id: grant_id, shared_grant_id: basic.id, shared: shared(), settings };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(v.iter().any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded)));
+}
+
+#[tokio::test]
+async fn evaluate_no_volume_limits_always_passes() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let grant = Grant {
+        id: 999,
+        shared_grant_id: 999,
+        shared: shared(),
+        settings: make_settings(None, None), // no volume limits
+    };
+    let calldata = transfer_calldata(RECIPIENT, U256::from(u64::MAX));
+    let context = ctx(DAI, calldata);
+    let m = TokenTransfer::analyze(&context).unwrap();
+    let v = TokenTransfer::evaluate(&context, &m, &grant, &mut *conn).await.unwrap();
+    assert!(!v.iter().any(|e| matches!(e, EvalViolation::VolumetricLimitExceeded)));
+}
+
+// ── try_find_grant ───────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn try_find_grant_roundtrip() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(Some(RECIPIENT), Some(5_000));
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    let calldata = transfer_calldata(RECIPIENT, U256::from(100u64));
+    let found = TokenTransfer::try_find_grant(&ctx(DAI, calldata), &mut *conn)
+        .await
+        .unwrap();
+
+    assert!(found.is_some());
+    let g = found.unwrap();
+    assert_eq!(g.settings.token_contract, DAI);
+    assert_eq!(g.settings.target, Some(RECIPIENT));
+    assert_eq!(g.settings.volume_limits.len(), 1);
+    assert_eq!(g.settings.volume_limits[0].max_volume, U256::from(5_000u64));
+}
+
+#[tokio::test]
+async fn try_find_grant_revoked_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, true).await;
+    let settings = make_settings(None, None);
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    let calldata = transfer_calldata(RECIPIENT, U256::from(1u64));
+    let found = TokenTransfer::try_find_grant(&ctx(DAI, calldata), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+#[tokio::test]
+async fn try_find_grant_unknown_token_returns_none() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, None);
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    // Query with a different token contract
+    let calldata = transfer_calldata(RECIPIENT, U256::from(1u64));
+    let found = TokenTransfer::try_find_grant(&ctx(UNKNOWN_TOKEN, calldata), &mut *conn)
+        .await
+        .unwrap();
+    assert!(found.is_none());
+}
+
+// ── find_all_grants ──────────────────────────────────────────────────────
+
+#[tokio::test]
+async fn find_all_grants_empty_db() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert!(all.is_empty());
+}
+
+#[tokio::test]
+async fn find_all_grants_excludes_revoked() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let settings = make_settings(None, Some(1_000));
+    let active = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(&active, &settings, &mut *conn).await.unwrap();
+    let revoked = insert_basic(&mut conn, true).await;
+    TokenTransfer::create_grant(&revoked, &settings, &mut *conn).await.unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+}
+
+#[tokio::test]
+async fn find_all_grants_loads_volume_limits() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let basic = insert_basic(&mut conn, false).await;
+    let settings = make_settings(None, Some(9_999));
+    TokenTransfer::create_grant(&basic, &settings, &mut *conn).await.unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 1);
+    assert_eq!(all[0].settings.volume_limits.len(), 1);
+    assert_eq!(all[0].settings.volume_limits[0].max_volume, U256::from(9_999u64));
+}
+
+#[tokio::test]
+async fn find_all_grants_multiple_grants_batch_loaded() {
+    let db = db::create_test_pool().await;
+    let mut conn = db.get().await.unwrap();
+
+    let b1 = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(&b1, &make_settings(None, Some(1_000)), &mut *conn)
+        .await
+        .unwrap();
+    let b2 = insert_basic(&mut conn, false).await;
+    TokenTransfer::create_grant(&b2, &make_settings(Some(RECIPIENT), Some(2_000)), &mut *conn)
+        .await
+        .unwrap();
+
+    let all = TokenTransfer::find_all_grants(&mut *conn).await.unwrap();
+    assert_eq!(all.len(), 2);
+}

server/crates/arbiter-server/src/evm/safe_signer.rs

@@ -0,0 +1,196 @@
+use std::sync::Mutex;
+
+use alloy::{
+    consensus::SignableTransaction,
+    network::{TxSigner, TxSignerSync},
+    primitives::{Address, ChainId, Signature, B256},
+    signers::{Error, Result, Signer, SignerSync, utils::secret_key_to_address},
+};
+use async_trait::async_trait;
+use k256::ecdsa::{self, signature::hazmat::PrehashSigner, RecoveryId, SigningKey};
+use memsafe::MemSafe;
+
+/// An Ethereum signer that stores its secp256k1 secret key inside a
+/// hardware-protected [`MemSafe`] cell.
+///
+/// The underlying memory page is kept non-readable/non-writable at rest.
+/// Access is temporarily elevated only for the duration of each signing
+/// operation, then immediately revoked.
+///
+/// Because [`MemSafe::read`] requires `&mut self` while the [`Signer`] trait
+/// requires `&self`, the cell is wrapped in a [`Mutex`].
+pub struct SafeSigner {
+    key: Mutex<MemSafe<SigningKey>>,
+    address: Address,
+    chain_id: Option<ChainId>,
+}
+
+impl std::fmt::Debug for SafeSigner {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("SafeSigner")
+            .field("address", &self.address)
+            .field("chain_id", &self.chain_id)
+            .finish()
+    }
+}
+
+/// Generates a secp256k1 secret key directly inside a [`MemSafe`] cell.
+///
+/// Random bytes are written in-place into protected memory, then validated
+/// as a legal scalar on the secp256k1 curve (the scalar must be in
+/// `[1, n)` where `n` is the curve order — roughly 1-in-2^128 chance of
+/// rejection, but we retry to be correct).
+///
+/// Returns the protected key bytes and the derived Ethereum address.
+pub fn generate(rng: &mut impl rand::Rng) -> (MemSafe<[u8; 32]>, Address) {
+    loop {
+        let mut cell = MemSafe::new([0u8; 32]).expect("MemSafe allocation");
+        {
+            let mut w = cell.write().expect("MemSafe write");
+            rng.fill_bytes(w.as_mut());
+        }
+        let reader = cell.read().expect("MemSafe read");
+        if let Ok(sk) = SigningKey::from_slice(reader.as_ref()) {
+            let address = secret_key_to_address(&sk);
+            drop(reader);
+            return (cell, address);
+        }
+    }
+}
+
+impl SafeSigner {
+    /// Reconstructs a `SafeSigner` from key material held in a [`MemSafe`] buffer.
+    ///
+    /// The key bytes are read from protected memory, parsed as a secp256k1
+    /// scalar, and immediately moved into a new [`MemSafe`] cell. The raw
+    /// bytes are never exposed outside this function.
+    pub fn from_memsafe(mut cell: MemSafe<Vec<u8>>) -> Result<Self> {
+        let reader = cell.read().map_err(Error::other)?;
+        let sk = SigningKey::from_slice(reader.as_slice()).map_err(Error::other)?;
+        drop(reader);
+        Self::new(sk)
+    }
+
+    /// Creates a new `SafeSigner` by moving the signing key into a protected
+    /// memory region.
+    pub fn new(key: SigningKey) -> Result<Self> {
+        let address = secret_key_to_address(&key);
+        let cell = MemSafe::new(key).map_err(Error::other)?;
+        Ok(Self {
+            key: Mutex::new(cell),
+            address,
+            chain_id: None,
+        })
+    }
+
+    fn sign_hash_inner(&self, hash: &B256) -> Result<Signature> {
+        let mut cell = self.key.lock().expect("SafeSigner mutex poisoned");
+        let reader = cell.read().map_err(Error::other)?;
+        let sig: (ecdsa::Signature, RecoveryId) = reader.sign_prehash(hash.as_ref())?;
+        Ok(sig.into())
+    }
+
+    fn sign_tx_inner(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        if let Some(chain_id) = self.chain_id
+            && !tx.set_chain_id_checked(chain_id)
+        {
+            return Err(Error::TransactionChainIdMismatch {
+                signer: chain_id,
+                tx: tx.chain_id().unwrap(),
+            });
+        }
+        self.sign_hash_inner(&tx.signature_hash()).map_err(Error::other)
+    }
+}
+
+#[async_trait]
+impl Signer for SafeSigner {
+    #[inline]
+    async fn sign_hash(&self, hash: &B256) -> Result<Signature> {
+        self.sign_hash_inner(hash)
+    }
+
+    #[inline]
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    #[inline]
+    fn chain_id(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+
+    #[inline]
+    fn set_chain_id(&mut self, chain_id: Option<ChainId>) {
+        self.chain_id = chain_id;
+    }
+}
+
+impl SignerSync for SafeSigner {
+    #[inline]
+    fn sign_hash_sync(&self, hash: &B256) -> Result<Signature> {
+        self.sign_hash_inner(hash)
+    }
+
+    #[inline]
+    fn chain_id_sync(&self) -> Option<ChainId> {
+        self.chain_id
+    }
+}
+
+#[async_trait]
+impl TxSigner<Signature> for SafeSigner {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    async fn sign_transaction(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.sign_tx_inner(tx)
+    }
+}
+
+impl TxSignerSync<Signature> for SafeSigner {
+    fn address(&self) -> Address {
+        self.address
+    }
+
+    fn sign_transaction_sync(
+        &self,
+        tx: &mut dyn SignableTransaction<Signature>,
+    ) -> Result<Signature> {
+        self.sign_tx_inner(tx)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use alloy::signers::local::PrivateKeySigner;
+
+    #[test]
+    fn sign_and_recover() {
+        let pk = PrivateKeySigner::random();
+        let key = pk.into_credential();
+        let signer = SafeSigner::new(key).unwrap();
+        let message = b"hello arbiter";
+        let sig = signer.sign_message_sync(message).unwrap();
+        let recovered = sig.recover_address_from_msg(message).unwrap();
+        assert_eq!(recovered, Signer::address(&signer));
+    }
+
+    #[test]
+    fn chain_id_roundtrip() {
+        let pk = PrivateKeySigner::random();
+        let key = pk.into_credential();
+        let mut signer = SafeSigner::new(key).unwrap();
+        assert_eq!(Signer::chain_id(&signer), None);
+        signer.set_chain_id(Some(1337));
+        assert_eq!(Signer::chain_id(&signer), Some(1337));
+    }
+}

server/crates/arbiter-server/src/evm/utils.rs

@@ -0,0 +1,26 @@
+use alloy::primitives::U256;
+
+#[derive(thiserror::Error, Debug)]
+#[error("Expected {expected} bytes but got {actual} bytes")]
+pub struct LengthError {
+    pub expected: usize,
+    pub actual: usize,
+}
+
+pub fn u256_to_bytes(value: U256) -> [u8; 32] {
+    value.to_le_bytes()
+}
+pub fn bytes_to_u256(bytes: &[u8]) -> Option<U256> {
+    let bytes: [u8; 32] = bytes.try_into().ok()?;
+    Some(U256::from_le_bytes(bytes))
+}
+
+pub fn try_bytes_to_u256(bytes: &[u8]) -> diesel::result::QueryResult<U256> {
+    let bytes: [u8; 32] = bytes.try_into().map_err(|_| {
+        diesel::result::Error::DeserializationError(Box::new(LengthError {
+            expected: 32,
+            actual: bytes.len(),
+        }))
+    })?;
+    Ok(U256::from_le_bytes(bytes))
+}

server/crates/arbiter-server/src/lib.rs

@@ -1,62 +1,201 @@
-#![allow(unused)]
-
-use std::sync::Arc;
-
+#![forbid(unsafe_code)]
 use arbiter_proto::{
-    proto::{ClientRequest, ClientResponse, UserAgentRequest, UserAgentResponse},
-    transport::BiStream,
+    proto::{
+        client::{ClientRequest, ClientResponse},
+        user_agent::{UserAgentRequest, UserAgentResponse},
+    },
+    transport::{IdentityRecvConverter, SendConverter, grpc},
 };
 use async_trait::async_trait;
 use tokio_stream::wrappers::ReceiverStream;
 
 use tokio::sync::mpsc;
 use tonic::{Request, Response, Status};
+use tracing::info;
 
 use crate::{
-    actors::{client::handle_client, user_agent::handle_user_agent},
+    actors::{
+        client::{self, ClientConnection as ClientConnectionProps, ClientError, connect_client},
+        user_agent::{self, TransportResponseError, UserAgentConnection, connect_user_agent},
+    },
     context::ServerContext,
 };
 
 pub mod actors;
-mod context;
-mod db;
-mod errors;
+pub mod context;
+pub mod db;
+pub mod evm;
 
 const DEFAULT_CHANNEL_SIZE: usize = 1000;
 
+struct UserAgentGrpcSender;
+
+impl SendConverter for UserAgentGrpcSender {
+    type Input = Result<UserAgentResponse, TransportResponseError>;
+    type Output = Result<UserAgentResponse, Status>;
+
+    fn convert(&self, item: Self::Input) -> Self::Output {
+        match item {
+            Ok(message) => Ok(message),
+            Err(err) => Err(user_agent_error_status(err)),
+        }
+    }
+}
+
+struct ClientGrpcSender;
+
+impl SendConverter for ClientGrpcSender {
+    type Input = Result<ClientResponse, ClientError>;
+    type Output = Result<ClientResponse, Status>;
+
+    fn convert(&self, item: Self::Input) -> Self::Output {
+        match item {
+            Ok(message) => Ok(message),
+            Err(err) => Err(client_error_status(err)),
+        }
+    }
+}
+
+fn client_error_status(value: ClientError) -> Status {
+    match value {
+        ClientError::MissingRequestPayload | ClientError::UnexpectedRequestPayload => {
+            Status::invalid_argument("Expected message with payload")
+        }
+        ClientError::StateTransitionFailed => Status::internal("State machine error"),
+        ClientError::Auth(ref err) => client_auth_error_status(err),
+        ClientError::ConnectionRegistrationFailed => {
+            Status::internal("Connection registration failed")
+        }
+    }
+}
+
+fn client_auth_error_status(value: &client::auth::Error) -> Status {
+    use client::auth::Error;
+    match value {
+        Error::UnexpectedMessagePayload | Error::InvalidClientPubkeyLength => {
+            Status::invalid_argument(value.to_string())
+        }
+        Error::InvalidAuthPubkeyEncoding => {
+            Status::invalid_argument("Failed to convert pubkey to VerifyingKey")
+        }
+        Error::InvalidChallengeSolution => Status::unauthenticated(value.to_string()),
+        Error::NotRegistered => Status::permission_denied(value.to_string()),
+        Error::Transport => Status::internal("Transport error"),
+        Error::DatabasePoolUnavailable => Status::internal("Database pool error"),
+        Error::DatabaseOperationFailed => Status::internal("Database error"),
+        Error::InternalError => Status::internal("Internal error"),
+    }
+}
+
+fn user_agent_error_status(value: TransportResponseError) -> Status {
+    match value {
+        TransportResponseError::MissingRequestPayload
+        | TransportResponseError::UnexpectedRequestPayload => {
+            Status::invalid_argument("Expected message with payload")
+        }
+        TransportResponseError::InvalidStateForUnsealEncryptedKey => {
+            Status::failed_precondition("Invalid state for unseal encrypted key")
+        }
+        TransportResponseError::InvalidClientPubkeyLength => {
+            Status::invalid_argument("client_pubkey must be 32 bytes")
+        }
+        TransportResponseError::StateTransitionFailed => Status::internal("State machine error"),
+        TransportResponseError::KeyHolderActorUnreachable => {
+            Status::internal("Vault is not available")
+        }
+        TransportResponseError::Auth(ref err) => auth_error_status(err),
+        TransportResponseError::ConnectionRegistrationFailed => {
+            Status::internal("Failed registering connection")
+        }
+    }
+}
+
+fn auth_error_status(value: &user_agent::auth::Error) -> Status {
+    use user_agent::auth::Error;
+    match value {
+        Error::UnexpectedMessagePayload | Error::InvalidClientPubkeyLength => {
+            Status::invalid_argument(value.to_string())
+        }
+        Error::InvalidAuthPubkeyEncoding => {
+            Status::invalid_argument("Failed to convert pubkey to VerifyingKey")
+        }
+        Error::PublicKeyNotRegistered | Error::InvalidChallengeSolution => {
+            Status::unauthenticated(value.to_string())
+        }
+        Error::InvalidBootstrapToken => Status::invalid_argument("Invalid bootstrap token"),
+        Error::Transport => Status::internal("Transport error"),
+        Error::BootstrapperActorUnreachable => {
+            Status::internal("Bootstrap token consumption failed")
+        }
+        Error::DatabasePoolUnavailable => Status::internal("Database pool error"),
+        Error::DatabaseOperationFailed => Status::internal("Database error"),
+    }
+}
+
 pub struct Server {
     context: ServerContext,
 }
 
+impl Server {
+    pub fn new(context: ServerContext) -> Self {
+        Self { context }
+    }
+}
+
 #[async_trait]
 impl arbiter_proto::proto::arbiter_service_server::ArbiterService for Server {
     type UserAgentStream = ReceiverStream<Result<UserAgentResponse, Status>>;
     type ClientStream = ReceiverStream<Result<ClientResponse, Status>>;
 
+    #[tracing::instrument(level = "debug", skip(self))]
     async fn client(
         &self,
         request: Request<tonic::Streaming<ClientRequest>>,
     ) -> Result<Response<Self::ClientStream>, Status> {
         let req_stream = request.into_inner();
         let (tx, rx) = mpsc::channel(DEFAULT_CHANNEL_SIZE);
-        tokio::spawn(handle_client(
-            self.context.clone(),
-            BiStream {
-                request_stream: req_stream,
-                response_sender: tx,
-            },
-        ));
+
+        let transport = grpc::GrpcAdapter::new(
+            tx,
+            req_stream,
+            IdentityRecvConverter::<ClientRequest>::new(),
+            ClientGrpcSender,
+        );
+        let props = ClientConnectionProps::new(
+            self.context.db.clone(),
+            Box::new(transport),
+            self.context.actors.clone(),
+        );
+        tokio::spawn(connect_client(props));
+
+        info!(event = "connection established", "grpc.client");
 
         Ok(Response::new(ReceiverStream::new(rx)))
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     async fn user_agent(
         &self,
         request: Request<tonic::Streaming<UserAgentRequest>>,
     ) -> Result<Response<Self::UserAgentStream>, Status> {
         let req_stream = request.into_inner();
         let (tx, rx) = mpsc::channel(DEFAULT_CHANNEL_SIZE);
-        tokio::spawn(handle_user_agent(self.context.clone(), req_stream, tx));
+
+        let transport = grpc::GrpcAdapter::new(
+            tx,
+            req_stream,
+            IdentityRecvConverter::<UserAgentRequest>::new(),
+            UserAgentGrpcSender,
+        );
+        let props = UserAgentConnection::new(
+            self.context.db.clone(),
+            self.context.actors.clone(),
+            Box::new(transport),
+        );
+        tokio::spawn(connect_user_agent(props));
+
+        info!(event = "connection established", "grpc.user_agent");
+
         Ok(Response::new(ReceiverStream::new(rx)))
     }
 }

server/crates/arbiter-server/src/main.rs

@@ -0,0 +1,53 @@
+use std::net::SocketAddr;
+
+use arbiter_proto::{proto::arbiter_service_server::ArbiterServiceServer, url::ArbiterUrl};
+use arbiter_server::{Server, actors::bootstrap::GetToken, context::ServerContext, db};
+use miette::miette;
+use tonic::transport::{Identity, ServerTlsConfig};
+use tracing::info;
+
+const PORT: u16 = 50051;
+
+#[tokio::main]
+async fn main() -> miette::Result<()> {
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("info")),
+        )
+        .init();
+
+    info!("Starting arbiter server");
+
+    let db = db::create_pool(None).await?;
+    info!("Database ready");
+
+    let context = ServerContext::new(db).await?;
+
+    let addr: SocketAddr = format!("127.0.0.1:{PORT}").parse().expect("valid address");
+    info!(%addr, "Starting gRPC server");
+
+    let url = ArbiterUrl {
+        host: addr.ip().to_string(),
+        port: addr.port(),
+        ca_cert: context.tls.ca_cert().clone().into_owned(),
+        bootstrap_token: context.actors.bootstrapper.ask(GetToken).await.unwrap(),
+    };
+
+    info!(%url, "Server URL");
+
+    let tls = ServerTlsConfig::new().identity(Identity::from_pem(
+        context.tls.cert_pem(),
+        context.tls.key_pem(),
+    ));
+
+    tonic::transport::Server::builder()
+        .tls_config(tls)
+        .map_err(|err| miette!("Faild to setup TLS: {err}"))?
+        .add_service(ArbiterServiceServer::new(Server::new(context)))
+        .serve(addr)
+        .await
+        .map_err(|e| miette::miette!("gRPC server error: {e}"))?;
+
+    unreachable!("gRPC server should run indefinitely");
+}

server/crates/arbiter-server/tests/client.rs

@@ -0,0 +1,4 @@
+mod common;
+
+#[path = "client/auth.rs"]
+mod auth;

server/crates/arbiter-server/tests/client/auth.rs

@@ -0,0 +1,222 @@
+use alloy::{
+    consensus::TxEip1559,
+    primitives::{Address, Bytes, TxKind, U256},
+    rlp::Encodable,
+};
+use arbiter_proto::proto::{
+    client::{
+        AuthChallengeRequest, AuthChallengeSolution, ClientRequest,
+        client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+    },
+    evm::EvmSignTransactionRequest,
+};
+use arbiter_proto::transport::Bi;
+use arbiter_server::actors::GlobalActors;
+use arbiter_server::{
+    actors::client::{ClientConnection, connect_client},
+    db::{self, schema},
+};
+use diesel::{ExpressionMethods as _, insert_into};
+use diesel_async::RunQueryDsl;
+use ed25519_dalek::Signer as _;
+
+use super::common::ChannelTransport;
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_unregistered_pubkey_rejected() {
+    let db = db::create_test_pool().await;
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+    let props = ClientConnection::new(db.clone(), Box::new(server_transport), actors);
+    let task = tokio::spawn(connect_client(props));
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Auth fails, connect_client returns, transport drops
+    task.await.unwrap();
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_challenge_auth() {
+    let db = db::create_test_pool().await;
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    {
+        let mut conn = db.get().await.unwrap();
+        insert_into(schema::program_client::table)
+            .values(schema::program_client::public_key.eq(pubkey_bytes.clone()))
+            .execute(&mut conn)
+            .await
+            .unwrap();
+    }
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    let props = ClientConnection::new(db.clone(), Box::new(server_transport), actors);
+    let task = tokio::spawn(connect_client(props));
+
+    // Send challenge request
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Read the challenge response
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(resp) => match resp.payload {
+            Some(ClientResponsePayload::AuthChallenge(c)) => c,
+            other => panic!("Expected AuthChallenge, got {other:?}"),
+        },
+        Err(err) => panic!("Expected Ok response, got Err({err:?})"),
+    };
+
+    // Sign the challenge and send solution
+    let formatted_challenge = arbiter_proto::format_challenge(challenge.nonce, &challenge.pubkey);
+    let signature = new_key.sign(&formatted_challenge);
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeSolution(
+                AuthChallengeSolution {
+                    signature: signature.to_bytes().to_vec(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Auth completes, session spawned
+    task.await.unwrap();
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_evm_sign_request_payload_is_handled() {
+    let db = db::create_test_pool().await;
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    {
+        let mut conn = db.get().await.unwrap();
+        insert_into(schema::program_client::table)
+            .values(schema::program_client::public_key.eq(pubkey_bytes.clone()))
+            .execute(&mut conn)
+            .await
+            .unwrap();
+    }
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    let props = ClientConnection::new(db.clone(), Box::new(server_transport), actors);
+    let task = tokio::spawn(connect_client(props));
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(resp) => match resp.payload {
+            Some(ClientResponsePayload::AuthChallenge(c)) => c,
+            other => panic!("Expected AuthChallenge, got {other:?}"),
+        },
+        Err(err) => panic!("Expected Ok response, got Err({err:?})"),
+    };
+
+    let formatted_challenge = arbiter_proto::format_challenge(challenge.nonce, &challenge.pubkey);
+    let signature = new_key.sign(&formatted_challenge);
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeSolution(
+                AuthChallengeSolution {
+                    signature: signature.to_bytes().to_vec(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    task.await.unwrap();
+
+    let tx = TxEip1559 {
+        chain_id: 1,
+        nonce: 0,
+        gas_limit: 21_000,
+        max_fee_per_gas: 1,
+        max_priority_fee_per_gas: 1,
+        to: TxKind::Call(Address::from_slice(&[0x11; 20])),
+        value: U256::ZERO,
+        input: Bytes::new(),
+        access_list: Default::default(),
+    };
+
+    let mut rlp_transaction = Vec::new();
+    tx.encode(&mut rlp_transaction);
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::EvmSignTransaction(
+                EvmSignTransactionRequest {
+                    wallet_address: [0x22; 20].to_vec(),
+                    rlp_transaction,
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive sign response");
+
+    match response {
+        Ok(resp) => match resp.payload {
+            Some(ClientResponsePayload::EvmSignTransaction(_)) => {}
+            other => panic!("Expected EvmSignTransaction response, got {other:?}"),
+        },
+        Err(err) => panic!("Expected Ok response, got Err({err:?})"),
+    }
+}

server/crates/arbiter-server/tests/common/mod.rs

@@ -0,0 +1,73 @@
+use arbiter_proto::transport::{Bi, Error};
+use arbiter_server::{
+    actors::keyholder::KeyHolder,
+    db::{self, schema},
+};
+use async_trait::async_trait;
+use diesel::QueryDsl;
+use diesel_async::RunQueryDsl;
+use memsafe::MemSafe;
+use tokio::sync::mpsc;
+
+#[allow(dead_code)]
+pub async fn bootstrapped_keyholder(db: &db::DatabasePool) -> KeyHolder {
+    let mut actor = KeyHolder::new(db.clone()).await.unwrap();
+    actor
+        .bootstrap(MemSafe::new(b"test-seal-key".to_vec()).unwrap())
+        .await
+        .unwrap();
+    actor
+}
+
+#[allow(dead_code)]
+pub async fn root_key_history_id(db: &db::DatabasePool) -> i32 {
+    let mut conn = db.get().await.unwrap();
+    let id = schema::arbiter_settings::table
+        .select(schema::arbiter_settings::root_key_id)
+        .first::<Option<i32>>(&mut conn)
+        .await
+        .unwrap();
+    id.expect("root_key_id should be set after bootstrap")
+}
+
+#[allow(dead_code)]
+pub struct ChannelTransport<T, Y> {
+    receiver: mpsc::Receiver<T>,
+    sender: mpsc::Sender<Y>,
+}
+
+impl<T, Y> ChannelTransport<T, Y> {
+    #[allow(dead_code)]
+    pub fn new() -> (Self, ChannelTransport<Y, T>) {
+        let (tx1, rx1) = mpsc::channel(10);
+        let (tx2, rx2) = mpsc::channel(10);
+        (
+            Self {
+                receiver: rx1,
+                sender: tx2,
+            },
+            ChannelTransport {
+                receiver: rx2,
+                sender: tx1,
+            },
+        )
+    }
+}
+
+#[async_trait]
+impl<T, Y> Bi<T, Y> for ChannelTransport<T, Y>
+where
+    T: Send + 'static,
+    Y: Send + 'static,
+{
+    async fn send(&mut self, item: Y) -> Result<(), Error> {
+        self.sender
+            .send(item)
+            .await
+            .map_err(|_| Error::ChannelClosed)
+    }
+
+    async fn recv(&mut self) -> Option<T> {
+        self.receiver.recv().await
+    }
+}

server/crates/arbiter-server/tests/keyholder.rs

@@ -0,0 +1,8 @@
+mod common;
+
+#[path = "keyholder/concurrency.rs"]
+mod concurrency;
+#[path = "keyholder/lifecycle.rs"]
+mod lifecycle;
+#[path = "keyholder/storage.rs"]
+mod storage;

server/crates/arbiter-server/tests/keyholder/concurrency.rs

@@ -0,0 +1,173 @@
+use std::collections::{HashMap, HashSet};
+
+use arbiter_server::{
+    actors::keyholder::{CreateNew, Error, KeyHolder},
+    db::{self, models, schema},
+};
+use diesel::{ExpressionMethods as _, QueryDsl, SelectableHelper, dsl::sql_query};
+use diesel_async::RunQueryDsl;
+use kameo::actor::{ActorRef, Spawn as _};
+use memsafe::MemSafe;
+use tokio::task::JoinSet;
+
+use crate::common;
+
+async fn write_concurrently(
+    actor: ActorRef<KeyHolder>,
+    prefix: &'static str,
+    count: usize,
+) -> Vec<(i32, Vec<u8>)> {
+    let mut set = JoinSet::new();
+    for i in 0..count {
+        let actor = actor.clone();
+        set.spawn(async move {
+            let plaintext = format!("{prefix}-{i}").into_bytes();
+            let id = actor
+                .ask(CreateNew {
+                    plaintext: MemSafe::new(plaintext.clone()).unwrap(),
+                })
+                .await
+                .unwrap();
+            (id, plaintext)
+        });
+    }
+
+    let mut out = Vec::with_capacity(count);
+    while let Some(res) = set.join_next().await {
+        out.push(res.unwrap());
+    }
+    out
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn concurrent_create_new_no_duplicate_nonces_() {
+    let db = db::create_test_pool().await;
+    let actor = KeyHolder::spawn(common::bootstrapped_keyholder(&db).await);
+
+    let writes = write_concurrently(actor, "nonce-unique", 32).await;
+    assert_eq!(writes.len(), 32);
+
+    let mut conn = db.get().await.unwrap();
+    let rows: Vec<models::AeadEncrypted> = schema::aead_encrypted::table
+        .select(models::AeadEncrypted::as_select())
+        .load(&mut conn)
+        .await
+        .unwrap();
+    assert_eq!(rows.len(), 32);
+
+    let nonces: Vec<&Vec<u8>> = rows.iter().map(|r| &r.current_nonce).collect();
+    let unique: HashSet<&Vec<u8>> = nonces.iter().copied().collect();
+    assert_eq!(nonces.len(), unique.len(), "all nonces must be unique");
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn concurrent_create_new_root_nonce_never_moves_backward() {
+    let db = db::create_test_pool().await;
+    let actor = KeyHolder::spawn(common::bootstrapped_keyholder(&db).await);
+
+    write_concurrently(actor, "root-max", 24).await;
+
+    let mut conn = db.get().await.unwrap();
+    let rows: Vec<models::AeadEncrypted> = schema::aead_encrypted::table
+        .select(models::AeadEncrypted::as_select())
+        .load(&mut conn)
+        .await
+        .unwrap();
+    let max_nonce = rows
+        .iter()
+        .map(|r| r.current_nonce.clone())
+        .max()
+        .expect("at least one row");
+
+    let root_row: models::RootKeyHistory = schema::root_key_history::table
+        .select(models::RootKeyHistory::as_select())
+        .first(&mut conn)
+        .await
+        .unwrap();
+    assert_eq!(root_row.data_encryption_nonce, max_nonce);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn insert_failure_does_not_create_partial_row() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+    let root_key_history_id = common::root_key_history_id(&db).await;
+
+    let mut conn = db.get().await.unwrap();
+    let before_count: i64 = schema::aead_encrypted::table
+        .count()
+        .get_result(&mut conn)
+        .await
+        .unwrap();
+    let before_root_nonce: Vec<u8> = schema::root_key_history::table
+        .filter(schema::root_key_history::id.eq(root_key_history_id))
+        .select(schema::root_key_history::data_encryption_nonce)
+        .first(&mut conn)
+        .await
+        .unwrap();
+
+    sql_query(
+        "CREATE TRIGGER fail_aead_insert BEFORE INSERT ON aead_encrypted BEGIN SELECT RAISE(ABORT, 'forced test failure'); END;",
+    )
+    .execute(&mut conn)
+    .await
+    .unwrap();
+    drop(conn);
+
+    let err = actor
+        .create_new(MemSafe::new(b"should fail".to_vec()).unwrap())
+        .await
+        .unwrap_err();
+    assert!(matches!(err, Error::DatabaseTransaction(_)));
+
+    let mut conn = db.get().await.unwrap();
+    sql_query("DROP TRIGGER fail_aead_insert;")
+        .execute(&mut conn)
+        .await
+        .unwrap();
+
+    let after_count: i64 = schema::aead_encrypted::table
+        .count()
+        .get_result(&mut conn)
+        .await
+        .unwrap();
+    assert_eq!(
+        before_count, after_count,
+        "failed insert must not create row"
+    );
+
+    let after_root_nonce: Vec<u8> = schema::root_key_history::table
+        .filter(schema::root_key_history::id.eq(root_key_history_id))
+        .select(schema::root_key_history::data_encryption_nonce)
+        .first(&mut conn)
+        .await
+        .unwrap();
+    assert!(
+        after_root_nonce > before_root_nonce,
+        "current behavior allows nonce gap on failed insert"
+    );
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn decrypt_roundtrip_after_high_concurrency() {
+    let db = db::create_test_pool().await;
+    let actor = KeyHolder::spawn(common::bootstrapped_keyholder(&db).await);
+
+    let writes = write_concurrently(actor, "roundtrip", 40).await;
+    let expected: HashMap<i32, Vec<u8>> = writes.into_iter().collect();
+
+    let mut decryptor = KeyHolder::new(db.clone()).await.unwrap();
+    decryptor
+        .try_unseal(MemSafe::new(b"test-seal-key".to_vec()).unwrap())
+        .await
+        .unwrap();
+
+    for (id, plaintext) in expected {
+        let mut decrypted = decryptor.decrypt(id).await.unwrap();
+        assert_eq!(*decrypted.read().unwrap(), plaintext);
+    }
+}

server/crates/arbiter-server/tests/keyholder/lifecycle.rs

@@ -0,0 +1,131 @@
+use arbiter_server::{
+    actors::keyholder::{Error, KeyHolder},
+    db::{self, models, schema},
+};
+use diesel::{QueryDsl, SelectableHelper};
+use diesel_async::RunQueryDsl;
+use memsafe::MemSafe;
+
+use crate::common;
+
+#[tokio::test]
+#[test_log::test]
+async fn test_bootstrap() {
+    let db = db::create_test_pool().await;
+    let mut actor = KeyHolder::new(db.clone()).await.unwrap();
+
+    let seal_key = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+    actor.bootstrap(seal_key).await.unwrap();
+
+    let mut conn = db.get().await.unwrap();
+    let row: models::RootKeyHistory = schema::root_key_history::table
+        .select(models::RootKeyHistory::as_select())
+        .first(&mut conn)
+        .await
+        .unwrap();
+
+    assert_eq!(row.schema_version, 1);
+    assert_eq!(
+        row.tag,
+        arbiter_server::actors::keyholder::encryption::v1::ROOT_KEY_TAG
+    );
+    assert!(!row.ciphertext.is_empty());
+    assert!(!row.salt.is_empty());
+    assert_eq!(
+        row.data_encryption_nonce,
+        arbiter_server::actors::keyholder::encryption::v1::Nonce::default().to_vec()
+    );
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_bootstrap_rejects_double() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let seal_key2 = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+    let err = actor.bootstrap(seal_key2).await.unwrap_err();
+    assert!(matches!(err, Error::AlreadyBootstrapped));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_create_new_before_bootstrap_fails() {
+    let db = db::create_test_pool().await;
+    let mut actor = KeyHolder::new(db).await.unwrap();
+
+    let err = actor
+        .create_new(MemSafe::new(b"data".to_vec()).unwrap())
+        .await
+        .unwrap_err();
+    assert!(matches!(err, Error::NotBootstrapped));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_decrypt_before_bootstrap_fails() {
+    let db = db::create_test_pool().await;
+    let mut actor = KeyHolder::new(db).await.unwrap();
+
+    let err = actor.decrypt(1).await.unwrap_err();
+    assert!(matches!(err, Error::NotBootstrapped));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_new_restores_sealed_state() {
+    let db = db::create_test_pool().await;
+    let actor = common::bootstrapped_keyholder(&db).await;
+    drop(actor);
+
+    let mut actor2 = KeyHolder::new(db).await.unwrap();
+    let err = actor2.decrypt(1).await.unwrap_err();
+    assert!(matches!(err, Error::NotBootstrapped));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_unseal_correct_password() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let plaintext = b"survive a restart";
+    let aead_id = actor
+        .create_new(MemSafe::new(plaintext.to_vec()).unwrap())
+        .await
+        .unwrap();
+    drop(actor);
+
+    let mut actor = KeyHolder::new(db.clone()).await.unwrap();
+    let seal_key = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+    actor.try_unseal(seal_key).await.unwrap();
+
+    let mut decrypted = actor.decrypt(aead_id).await.unwrap();
+    assert_eq!(*decrypted.read().unwrap(), plaintext);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_unseal_wrong_then_correct_password() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let plaintext = b"important data";
+    let aead_id = actor
+        .create_new(MemSafe::new(plaintext.to_vec()).unwrap())
+        .await
+        .unwrap();
+    drop(actor);
+
+    let mut actor = KeyHolder::new(db.clone()).await.unwrap();
+
+    let bad_key = MemSafe::new(b"wrong-password".to_vec()).unwrap();
+    let err = actor.try_unseal(bad_key).await.unwrap_err();
+    assert!(matches!(err, Error::InvalidKey));
+
+    let good_key = MemSafe::new(b"test-seal-key".to_vec()).unwrap();
+    actor.try_unseal(good_key).await.unwrap();
+
+    let mut decrypted = actor.decrypt(aead_id).await.unwrap();
+    assert_eq!(*decrypted.read().unwrap(), plaintext);
+}

server/crates/arbiter-server/tests/keyholder/storage.rs

@@ -0,0 +1,161 @@
+use std::collections::HashSet;
+
+use arbiter_server::{
+    actors::keyholder::{Error, encryption::v1},
+    db::{self, models, schema},
+};
+use diesel::{ExpressionMethods as _, QueryDsl, SelectableHelper, dsl::update};
+use diesel_async::RunQueryDsl;
+use memsafe::MemSafe;
+
+use crate::common;
+
+#[tokio::test]
+#[test_log::test]
+async fn test_create_decrypt_roundtrip() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let plaintext = b"hello arbiter";
+    let aead_id = actor
+        .create_new(MemSafe::new(plaintext.to_vec()).unwrap())
+        .await
+        .unwrap();
+
+    let mut decrypted = actor.decrypt(aead_id).await.unwrap();
+    assert_eq!(*decrypted.read().unwrap(), plaintext);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_decrypt_nonexistent_returns_not_found() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let err = actor.decrypt(9999).await.unwrap_err();
+    assert!(matches!(err, Error::NotFound));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_ciphertext_differs_across_entries() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let plaintext = b"same content";
+    let id1 = actor
+        .create_new(MemSafe::new(plaintext.to_vec()).unwrap())
+        .await
+        .unwrap();
+    let id2 = actor
+        .create_new(MemSafe::new(plaintext.to_vec()).unwrap())
+        .await
+        .unwrap();
+
+    let mut conn = db.get().await.unwrap();
+    let row1: models::AeadEncrypted = schema::aead_encrypted::table
+        .filter(schema::aead_encrypted::id.eq(id1))
+        .select(models::AeadEncrypted::as_select())
+        .first(&mut conn)
+        .await
+        .unwrap();
+    let row2: models::AeadEncrypted = schema::aead_encrypted::table
+        .filter(schema::aead_encrypted::id.eq(id2))
+        .select(models::AeadEncrypted::as_select())
+        .first(&mut conn)
+        .await
+        .unwrap();
+
+    assert_ne!(row1.ciphertext, row2.ciphertext);
+
+    let mut d1 = actor.decrypt(id1).await.unwrap();
+    let mut d2 = actor.decrypt(id2).await.unwrap();
+    assert_eq!(*d1.read().unwrap(), plaintext);
+    assert_eq!(*d2.read().unwrap(), plaintext);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_nonce_never_reused() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+
+    let n = 5;
+    for i in 0..n {
+        actor
+            .create_new(MemSafe::new(format!("secret {i}").into_bytes()).unwrap())
+            .await
+            .unwrap();
+    }
+
+    let mut conn = db.get().await.unwrap();
+    let rows: Vec<models::AeadEncrypted> = schema::aead_encrypted::table
+        .select(models::AeadEncrypted::as_select())
+        .load(&mut conn)
+        .await
+        .unwrap();
+
+    assert_eq!(rows.len(), n);
+
+    let nonces: Vec<&Vec<u8>> = rows.iter().map(|r| &r.current_nonce).collect();
+    let unique: HashSet<&Vec<u8>> = nonces.iter().copied().collect();
+    assert_eq!(nonces.len(), unique.len(), "all nonces must be unique");
+
+    for (i, row) in rows.iter().enumerate() {
+        let mut expected = v1::Nonce::default();
+        for _ in 0..=i {
+            expected.increment();
+        }
+        assert_eq!(row.current_nonce, expected.to_vec(), "nonce {i} mismatch");
+    }
+
+    let root_row: models::RootKeyHistory = schema::root_key_history::table
+        .select(models::RootKeyHistory::as_select())
+        .first(&mut conn)
+        .await
+        .unwrap();
+    let last_nonce = &rows.last().unwrap().current_nonce;
+    assert_eq!(&root_row.data_encryption_nonce, last_nonce);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn broken_db_nonce_format_fails_closed() {
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+    let root_key_history_id = common::root_key_history_id(&db).await;
+
+    let mut conn = db.get().await.unwrap();
+    update(
+        schema::root_key_history::table
+            .filter(schema::root_key_history::id.eq(root_key_history_id)),
+    )
+    .set(schema::root_key_history::data_encryption_nonce.eq(vec![1, 2, 3]))
+    .execute(&mut conn)
+    .await
+    .unwrap();
+    drop(conn);
+
+    let err = actor
+        .create_new(MemSafe::new(b"must fail".to_vec()).unwrap())
+        .await
+        .unwrap_err();
+    assert!(matches!(err, Error::BrokenDatabase));
+
+    let db = db::create_test_pool().await;
+    let mut actor = common::bootstrapped_keyholder(&db).await;
+    let id = actor
+        .create_new(MemSafe::new(b"decrypt target".to_vec()).unwrap())
+        .await
+        .unwrap();
+    let mut conn = db.get().await.unwrap();
+    update(schema::aead_encrypted::table.filter(schema::aead_encrypted::id.eq(id)))
+        .set(schema::aead_encrypted::current_nonce.eq(vec![7, 8]))
+        .execute(&mut conn)
+        .await
+        .unwrap();
+    drop(conn);
+
+    let err = actor.decrypt(id).await.unwrap_err();
+    assert!(matches!(err, Error::BrokenDatabase));
+}

server/crates/arbiter-server/tests/user_agent.rs

@@ -0,0 +1,8 @@
+mod common;
+
+#[path = "user_agent/auth.rs"]
+mod auth;
+#[path = "user_agent/sdk_client.rs"]
+mod sdk_client;
+#[path = "user_agent/unseal.rs"]
+mod unseal;

server/crates/arbiter-server/tests/user_agent/auth.rs

@@ -0,0 +1,168 @@
+use arbiter_proto::proto::user_agent::{
+    AuthChallengeRequest, AuthChallengeSolution, KeyType as ProtoKeyType, UserAgentRequest,
+    user_agent_request::Payload as UserAgentRequestPayload,
+    user_agent_response::Payload as UserAgentResponsePayload,
+};
+use arbiter_proto::transport::Bi;
+use arbiter_server::{
+    actors::{
+        GlobalActors,
+        bootstrap::GetToken,
+        user_agent::{UserAgentConnection, connect_user_agent},
+    },
+    db::{self, schema},
+};
+use diesel::{ExpressionMethods as _, QueryDsl, insert_into};
+use diesel_async::RunQueryDsl;
+use ed25519_dalek::Signer as _;
+
+use super::common::ChannelTransport;
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_bootstrap_token_auth() {
+    let db = db::create_test_pool().await;
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+    let token = actors.bootstrapper.ask(GetToken).await.unwrap().unwrap();
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let props = UserAgentConnection::new(db.clone(), actors, Box::new(server_transport));
+    let task = tokio::spawn(connect_user_agent(props));
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    test_transport
+        .send(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                    bootstrap_token: Some(token),
+                    key_type: ProtoKeyType::Ed25519.into(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    task.await.unwrap();
+
+    let mut conn = db.get().await.unwrap();
+    let stored_pubkey: Vec<u8> = schema::useragent_client::table
+        .select(schema::useragent_client::public_key)
+        .first::<Vec<u8>>(&mut conn)
+        .await
+        .unwrap();
+    assert_eq!(stored_pubkey, new_key.verifying_key().to_bytes().to_vec());
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_bootstrap_invalid_token_auth() {
+    let db = db::create_test_pool().await;
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let props = UserAgentConnection::new(db.clone(), actors, Box::new(server_transport));
+    let task = tokio::spawn(connect_user_agent(props));
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    test_transport
+        .send(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                    bootstrap_token: Some("invalid_token".to_string()),
+                    key_type: ProtoKeyType::Ed25519.into(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Auth fails, connect_user_agent returns, transport drops
+    task.await.unwrap();
+
+    // Verify no key was registered
+    let mut conn = db.get().await.unwrap();
+    let count: i64 = schema::useragent_client::table
+        .count()
+        .get_result::<i64>(&mut conn)
+        .await
+        .unwrap();
+    assert_eq!(count, 0);
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_challenge_auth() {
+    let db = db::create_test_pool().await;
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    // Pre-register key with key_type
+    {
+        let mut conn = db.get().await.unwrap();
+        insert_into(schema::useragent_client::table)
+            .values((
+                schema::useragent_client::public_key.eq(pubkey_bytes.clone()),
+                schema::useragent_client::key_type.eq(1i32),
+            ))
+            .execute(&mut conn)
+            .await
+            .unwrap();
+    }
+
+    let (server_transport, mut test_transport) = ChannelTransport::new();
+    let props = UserAgentConnection::new(db.clone(), actors, Box::new(server_transport));
+    let task = tokio::spawn(connect_user_agent(props));
+
+    // Send challenge request
+    test_transport
+        .send(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes,
+                    bootstrap_token: None,
+                    key_type: ProtoKeyType::Ed25519.into(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Read the challenge response
+    let response = test_transport
+        .recv()
+        .await
+        .expect("should receive challenge");
+    let challenge = match response {
+        Ok(resp) => match resp.payload {
+            Some(UserAgentResponsePayload::AuthChallenge(c)) => c,
+            other => panic!("Expected AuthChallenge, got {other:?}"),
+        },
+        Err(err) => panic!("Expected Ok response, got Err({err:?})"),
+    };
+
+    // Sign the challenge and send solution
+    let formatted_challenge = arbiter_proto::format_challenge(challenge.nonce, &challenge.pubkey);
+    let signature = new_key.sign(&formatted_challenge);
+
+    test_transport
+        .send(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::AuthChallengeSolution(
+                AuthChallengeSolution {
+                    signature: signature.to_bytes().to_vec(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    // Auth completes, session spawned
+    task.await.unwrap();
+}

server/crates/arbiter-server/tests/user_agent/sdk_client.rs

@@ -0,0 +1,270 @@
+use arbiter_proto::proto::user_agent::{
+    SdkClientApproveRequest, SdkClientError as ProtoSdkClientError, SdkClientRevokeRequest,
+    UserAgentRequest, sdk_client_approve_response, sdk_client_list_response,
+    sdk_client_revoke_response, user_agent_request::Payload as UserAgentRequestPayload,
+    user_agent_response::Payload as UserAgentResponsePayload,
+};
+use arbiter_server::{
+    actors::{GlobalActors, user_agent::session::UserAgentSession},
+    db,
+};
+
+/// Shared helper: create a session and register a client pubkey via sdk_client_approve.
+async fn make_session(db: &db::DatabasePool) -> UserAgentSession {
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+    UserAgentSession::new_test(db.clone(), actors)
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_approve_registers_client() {
+    let db = db::create_test_pool().await;
+    let mut session = make_session(&db).await;
+
+    let pubkey = [0x42u8; 32];
+
+    let response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientApprove(
+                SdkClientApproveRequest {
+                    pubkey: pubkey.to_vec(),
+                },
+            )),
+        })
+        .await
+        .expect("handler should succeed");
+
+    let entry = match response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientApprove(resp) => match resp.result.unwrap() {
+            sdk_client_approve_response::Result::Client(e) => e,
+            sdk_client_approve_response::Result::Error(e) => {
+                panic!("Expected Client, got error {:?}", e)
+            }
+        },
+        other => panic!("Expected SdkClientApprove, got {other:?}"),
+    };
+
+    assert_eq!(entry.pubkey, pubkey.to_vec());
+    assert!(entry.id > 0);
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_approve_duplicate_returns_already_exists() {
+    let db = db::create_test_pool().await;
+    let mut session = make_session(&db).await;
+
+    let pubkey = [0x11u8; 32];
+    let req = UserAgentRequest {
+        payload: Some(UserAgentRequestPayload::SdkClientApprove(
+            SdkClientApproveRequest {
+                pubkey: pubkey.to_vec(),
+            },
+        )),
+    };
+
+    session
+        .process_transport_inbound(req.clone())
+        .await
+        .unwrap();
+
+    let response = session
+        .process_transport_inbound(req)
+        .await
+        .expect("second insert should not panic");
+
+    match response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientApprove(resp) => match resp.result.unwrap() {
+            sdk_client_approve_response::Result::Error(code) => {
+                assert_eq!(code, ProtoSdkClientError::AlreadyExists as i32);
+            }
+            sdk_client_approve_response::Result::Client(_) => {
+                panic!("Expected AlreadyExists error for duplicate pubkey")
+            }
+        },
+        other => panic!("Expected SdkClientApprove, got {other:?}"),
+    }
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_list_shows_registered_clients() {
+    let db = db::create_test_pool().await;
+    let mut session = make_session(&db).await;
+
+    let pubkey_a = [0x0Au8; 32];
+    let pubkey_b = [0x0Bu8; 32];
+
+    for pubkey in [pubkey_a, pubkey_b] {
+        session
+            .process_transport_inbound(UserAgentRequest {
+                payload: Some(UserAgentRequestPayload::SdkClientApprove(
+                    SdkClientApproveRequest {
+                        pubkey: pubkey.to_vec(),
+                    },
+                )),
+            })
+            .await
+            .unwrap();
+    }
+
+    let response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientList(())),
+        })
+        .await
+        .expect("list should succeed");
+
+    let clients = match response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientList(resp) => match resp.result.unwrap() {
+            sdk_client_list_response::Result::Clients(list) => list.clients,
+            sdk_client_list_response::Result::Error(e) => {
+                panic!("Expected Clients, got error {:?}", e)
+            }
+        },
+        other => panic!("Expected SdkClientList, got {other:?}"),
+    };
+
+    assert_eq!(clients.len(), 2);
+    let pubkeys: Vec<Vec<u8>> = clients.into_iter().map(|e| e.pubkey).collect();
+    assert!(pubkeys.contains(&pubkey_a.to_vec()));
+    assert!(pubkeys.contains(&pubkey_b.to_vec()));
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_revoke_removes_client() {
+    let db = db::create_test_pool().await;
+    let mut session = make_session(&db).await;
+
+    let pubkey = [0xBBu8; 32];
+
+    // Register a client and get its id
+    let approve_response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientApprove(
+                SdkClientApproveRequest {
+                    pubkey: pubkey.to_vec(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    let client_id = match approve_response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientApprove(resp) => match resp.result.unwrap() {
+            sdk_client_approve_response::Result::Client(e) => e.id,
+            sdk_client_approve_response::Result::Error(e) => panic!("approve failed: {:?}", e),
+        },
+        other => panic!("{other:?}"),
+    };
+
+    // Revoke the client
+    let revoke_response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientRevoke(
+                SdkClientRevokeRequest { client_id },
+            )),
+        })
+        .await
+        .expect("revoke should succeed");
+
+    match revoke_response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientRevoke(resp) => match resp.result.unwrap() {
+            sdk_client_revoke_response::Result::Ok(_) => {}
+            sdk_client_revoke_response::Result::Error(e) => {
+                panic!("Expected Ok, got error {:?}", e)
+            }
+        },
+        other => panic!("Expected SdkClientRevoke, got {other:?}"),
+    }
+
+    // List should now be empty
+    let list_response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientList(())),
+        })
+        .await
+        .unwrap();
+
+    let clients = match list_response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientList(resp) => match resp.result.unwrap() {
+            sdk_client_list_response::Result::Clients(list) => list.clients,
+            sdk_client_list_response::Result::Error(e) => panic!("list error: {:?}", e),
+        },
+        other => panic!("{other:?}"),
+    };
+    assert!(clients.is_empty(), "client should be removed after revoke");
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_revoke_not_found_returns_error() {
+    let db = db::create_test_pool().await;
+    let mut session = make_session(&db).await;
+
+    let response = session
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::SdkClientRevoke(
+                SdkClientRevokeRequest { client_id: 9999 },
+            )),
+        })
+        .await
+        .unwrap();
+
+    match response.payload.unwrap() {
+        UserAgentResponsePayload::SdkClientRevoke(resp) => match resp.result.unwrap() {
+            sdk_client_revoke_response::Result::Error(code) => {
+                assert_eq!(code, ProtoSdkClientError::NotFound as i32);
+            }
+            sdk_client_revoke_response::Result::Ok(_) => {
+                panic!("Expected NotFound error for missing client_id")
+            }
+        },
+        other => panic!("Expected SdkClientRevoke, got {other:?}"),
+    }
+}
+
+#[tokio::test]
+#[test_log::test]
+async fn test_sdk_client_approve_rejected_client_cannot_auth() {
+    // Verify the core flow: only pre-approved clients can authenticate
+    use arbiter_proto::proto::client::{
+        AuthChallengeRequest, ClientRequest, client_request::Payload as ClientRequestPayload,
+        client_response::Payload as ClientResponsePayload,
+    };
+    use arbiter_proto::transport::Bi as _;
+    use arbiter_server::actors::client::{ClientConnection, connect_client};
+
+    let db = db::create_test_pool().await;
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    let new_key = ed25519_dalek::SigningKey::generate(&mut rand::rng());
+    let pubkey_bytes = new_key.verifying_key().to_bytes().to_vec();
+
+    let (server_transport, mut test_transport) = super::common::ChannelTransport::<_, _>::new();
+    let props = ClientConnection::new(db.clone(), Box::new(server_transport), actors.clone());
+    let task = tokio::spawn(connect_client(props));
+
+    test_transport
+        .send(ClientRequest {
+            payload: Some(ClientRequestPayload::AuthChallengeRequest(
+                AuthChallengeRequest {
+                    pubkey: pubkey_bytes.clone(),
+                },
+            )),
+        })
+        .await
+        .unwrap();
+
+    let response = test_transport.recv().await.unwrap().unwrap();
+    assert!(
+        matches!(
+            response.payload.unwrap(),
+            ClientResponsePayload::ClientConnectError(_)
+        ),
+        "unregistered client should be rejected"
+    );
+
+    task.await.unwrap();
+}

server/crates/arbiter-server/tests/user_agent/unseal.rs

@@ -0,0 +1,184 @@
+use arbiter_proto::proto::user_agent::{
+    UnsealEncryptedKey, UnsealResult, UnsealStart, UserAgentRequest,
+    user_agent_request::Payload as UserAgentRequestPayload,
+    user_agent_response::Payload as UserAgentResponsePayload,
+};
+use arbiter_server::{
+    actors::{
+        GlobalActors,
+        keyholder::{Bootstrap, Seal},
+        user_agent::session::UserAgentSession,
+    },
+    db,
+};
+use chacha20poly1305::{AeadInPlace, XChaCha20Poly1305, XNonce, aead::KeyInit};
+use memsafe::MemSafe;
+use x25519_dalek::{EphemeralSecret, PublicKey};
+
+async fn setup_sealed_user_agent(
+    seal_key: &[u8],
+) -> (db::DatabasePool, UserAgentSession) {
+    let db = db::create_test_pool().await;
+    let actors = GlobalActors::spawn(db.clone()).await.unwrap();
+
+    actors
+        .key_holder
+        .ask(Bootstrap {
+            seal_key_raw: MemSafe::new(seal_key.to_vec()).unwrap(),
+        })
+        .await
+        .unwrap();
+    actors.key_holder.ask(Seal).await.unwrap();
+
+    let session = UserAgentSession::new_test(db.clone(), actors);
+
+    (db, session)
+}
+
+async fn client_dh_encrypt(
+    user_agent: &mut UserAgentSession,
+    key_to_send: &[u8],
+) -> UnsealEncryptedKey {
+    let client_secret = EphemeralSecret::random();
+    let client_public = PublicKey::from(&client_secret);
+
+    let response = user_agent
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::UnsealStart(UnsealStart {
+                client_pubkey: client_public.as_bytes().to_vec(),
+            })),
+        })
+        .await
+        .unwrap();
+
+    let server_pubkey = match response.payload.unwrap() {
+        UserAgentResponsePayload::UnsealStartResponse(resp) => resp.server_pubkey,
+        other => panic!("Expected UnsealStartResponse, got {other:?}"),
+    };
+    let server_public = PublicKey::from(<[u8; 32]>::try_from(server_pubkey.as_slice()).unwrap());
+
+    let shared_secret = client_secret.diffie_hellman(&server_public);
+    let cipher = XChaCha20Poly1305::new(shared_secret.as_bytes().into());
+    let nonce = XNonce::from([0u8; 24]);
+    let associated_data = b"unseal";
+    let mut ciphertext = key_to_send.to_vec();
+    cipher
+        .encrypt_in_place(&nonce, associated_data, &mut ciphertext)
+        .unwrap();
+
+    UnsealEncryptedKey {
+        nonce: nonce.to_vec(),
+        ciphertext,
+        associated_data: associated_data.to_vec(),
+    }
+}
+
+fn unseal_key_request(req: UnsealEncryptedKey) -> UserAgentRequest {
+    UserAgentRequest {
+        payload: Some(UserAgentRequestPayload::UnsealEncryptedKey(req)),
+    }
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_unseal_success() {
+    let seal_key = b"test-seal-key";
+    let (_db, mut user_agent) = setup_sealed_user_agent(seal_key).await;
+
+    let encrypted_key = client_dh_encrypt(&mut user_agent, seal_key).await;
+
+    let response = user_agent
+        .process_transport_inbound(unseal_key_request(encrypted_key))
+        .await
+        .unwrap();
+
+    assert_eq!(
+        response.payload.unwrap(),
+        UserAgentResponsePayload::UnsealResult(UnsealResult::Success.into()),
+    );
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_unseal_wrong_seal_key() {
+    let (_db, mut user_agent) = setup_sealed_user_agent(b"correct-key").await;
+
+    let encrypted_key = client_dh_encrypt(&mut user_agent, b"wrong-key").await;
+
+    let response = user_agent
+        .process_transport_inbound(unseal_key_request(encrypted_key))
+        .await
+        .unwrap();
+
+    assert_eq!(
+        response.payload.unwrap(),
+        UserAgentResponsePayload::UnsealResult(UnsealResult::InvalidKey.into()),
+    );
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_unseal_corrupted_ciphertext() {
+    let (_db, mut user_agent) = setup_sealed_user_agent(b"test-key").await;
+
+    let client_secret = EphemeralSecret::random();
+    let client_public = PublicKey::from(&client_secret);
+
+    user_agent
+        .process_transport_inbound(UserAgentRequest {
+            payload: Some(UserAgentRequestPayload::UnsealStart(UnsealStart {
+                client_pubkey: client_public.as_bytes().to_vec(),
+            })),
+        })
+        .await
+        .unwrap();
+
+    let response = user_agent
+        .process_transport_inbound(unseal_key_request(UnsealEncryptedKey {
+            nonce: vec![0u8; 24],
+            ciphertext: vec![0u8; 32],
+            associated_data: vec![],
+        }))
+        .await
+        .unwrap();
+
+    assert_eq!(
+        response.payload.unwrap(),
+        UserAgentResponsePayload::UnsealResult(UnsealResult::InvalidKey.into()),
+    );
+}
+
+#[tokio::test]
+#[test_log::test]
+pub async fn test_unseal_retry_after_invalid_key() {
+    let seal_key = b"real-seal-key";
+    let (_db, mut user_agent) = setup_sealed_user_agent(seal_key).await;
+
+    {
+        let encrypted_key = client_dh_encrypt(&mut user_agent, b"wrong-key").await;
+
+        let response = user_agent
+            .process_transport_inbound(unseal_key_request(encrypted_key))
+            .await
+            .unwrap();
+
+        assert_eq!(
+            response.payload.unwrap(),
+            UserAgentResponsePayload::UnsealResult(UnsealResult::InvalidKey.into()),
+        );
+    }
+
+    {
+        let encrypted_key = client_dh_encrypt(&mut user_agent, seal_key).await;
+
+        let response = user_agent
+            .process_transport_inbound(unseal_key_request(encrypted_key))
+            .await
+            .unwrap();
+
+        assert_eq!(
+            response.payload.unwrap(),
+            UserAgentResponsePayload::UnsealResult(UnsealResult::Success.into()),
+        );
+    }
+}

server/crates/arbiter-terrors-poc/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "arbiter-terrors-poc"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+terrors = "0.3"

server/crates/arbiter-terrors-poc/src/auth.rs

@@ -0,0 +1,139 @@
+use crate::errors::{InternalError1, InternalError2, InvalidSignature, NotRegistered};
+use terrors::OneOf;
+
+use crate::errors::ProtoError;
+
+// Each sub-call's error type already implements DrainInto<ProtoError>, so we convert
+// directly to ProtoError without broaden — no turbofish needed anywhere.
+//
+// Call chain:
+//   load_config()  → OneOf<(InternalError2,)>          → ProtoError::from
+//   get_nonce()    → OneOf<(InternalError1, InternalError2)> → ProtoError::from
+//   verify_sig()   → OneOf<(InvalidSignature,)>         → ProtoError::from
+pub fn process_request(id: u32, sig: &str) -> Result<String, ProtoError> {
+    if id == 0 {
+        return Err(ProtoError::NotRegistered);
+    }
+
+    let config = load_config(id).map_err(ProtoError::from)?;
+    let nonce = crate::db::get_nonce(id).map_err(ProtoError::from)?;
+    verify_signature(nonce, sig).map_err(ProtoError::from)?;
+
+    Ok(format!("config={config} nonce={nonce} sig={sig}"))
+}
+
+// Simulates loading a config value.
+// id=97 triggers InternalError2 ("config read failed").
+fn load_config(id: u32) -> Result<String, OneOf<(InternalError2,)>> {
+    if id == 97 {
+        return Err(OneOf::new(InternalError2("config read failed".to_owned())));
+    }
+    Ok(format!("cfg-{id}"))
+}
+
+pub fn verify_signature(_nonce: u32, sig: &str) -> Result<(), OneOf<(InvalidSignature,)>> {
+    if sig != "ok" {
+        return Err(OneOf::new(InvalidSignature));
+    }
+    Ok(())
+}
+
+type AuthError = OneOf<(
+    NotRegistered,
+    InvalidSignature,
+    InternalError1,
+    InternalError2,
+)>;
+
+pub fn authenticate(id: u32, sig: &str) -> Result<u32, AuthError> {
+    if id == 0 {
+        return Err(OneOf::new(NotRegistered));
+    }
+
+    // Return type AuthError lets the compiler infer the broaden target.
+    let nonce = crate::db::get_nonce(id).map_err(OneOf::broaden)?;
+    verify_signature(nonce, sig).map_err(OneOf::broaden)?;
+
+    Ok(nonce)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn verify_signature_ok() {
+        assert!(verify_signature(42, "ok").is_ok());
+    }
+
+    #[test]
+    fn verify_signature_bad() {
+        let err = verify_signature(42, "bad").unwrap_err();
+        assert!(err.narrow::<crate::errors::InvalidSignature, _>().is_ok());
+    }
+
+    #[test]
+    fn authenticate_success() {
+        assert_eq!(authenticate(1, "ok").unwrap(), 42);
+    }
+
+    #[test]
+    fn authenticate_not_registered() {
+        let err = authenticate(0, "ok").unwrap_err();
+        assert!(err.narrow::<crate::errors::NotRegistered, _>().is_ok());
+    }
+
+    #[test]
+    fn authenticate_invalid_signature() {
+        let err = authenticate(1, "bad").unwrap_err();
+        assert!(err.narrow::<crate::errors::InvalidSignature, _>().is_ok());
+    }
+
+    #[test]
+    fn authenticate_internal_error1() {
+        let err = authenticate(99, "ok").unwrap_err();
+        assert!(err.narrow::<crate::errors::InternalError1, _>().is_ok());
+    }
+
+    #[test]
+    fn authenticate_internal_error2() {
+        let err = authenticate(98, "ok").unwrap_err();
+        assert!(err.narrow::<crate::errors::InternalError2, _>().is_ok());
+    }
+
+    #[test]
+    fn process_request_success() {
+        let result = process_request(1, "ok").unwrap();
+        assert!(result.contains("nonce=42"));
+    }
+
+    #[test]
+    fn process_request_not_registered() {
+        let err = process_request(0, "ok").unwrap_err();
+        assert!(matches!(err, crate::errors::ProtoError::NotRegistered));
+    }
+
+    #[test]
+    fn process_request_invalid_signature() {
+        let err = process_request(1, "bad").unwrap_err();
+        assert!(matches!(err, crate::errors::ProtoError::InvalidSignature));
+    }
+
+    #[test]
+    fn process_request_internal_from_config() {
+        // id=97 → load_config returns InternalError2
+        let err = process_request(97, "ok").unwrap_err();
+        assert!(
+            matches!(err, crate::errors::ProtoError::Internal(ref msg) if msg == "config read failed")
+        );
+    }
+
+    #[test]
+    fn process_request_internal_from_db() {
+        // id=99 → get_nonce returns InternalError1
+        let err = process_request(99, "ok").unwrap_err();
+        assert!(
+            matches!(err, crate::errors::ProtoError::Internal(ref msg) if msg == "db pool unavailable")
+        );
+    }
+}

server/crates/arbiter-terrors-poc/src/db.rs

@@ -0,0 +1,38 @@
+use crate::errors::{InternalError1, InternalError2};
+use terrors::OneOf;
+
+// Simulates fetching a nonce from a database.
+// id=99 → InternalError1 (pool unavailable)
+// id=98 → InternalError2 (query timeout)
+pub fn get_nonce(id: u32) -> Result<u32, OneOf<(InternalError1, InternalError2)>> {
+    match id {
+        99 => Err(OneOf::new(InternalError1("db pool unavailable".to_owned()))),
+        98 => Err(OneOf::new(InternalError2("query timeout".to_owned()))),
+        _ => Ok(42),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn get_nonce_returns_nonce_for_valid_id() {
+        assert_eq!(get_nonce(1).unwrap(), 42);
+    }
+
+    #[test]
+    fn get_nonce_returns_internal_error1_for_sentinel() {
+        let err = get_nonce(99).unwrap_err();
+        let internal = err.narrow::<crate::errors::InternalError1, _>().unwrap();
+        assert_eq!(internal.0, "db pool unavailable");
+    }
+
+    #[test]
+    fn get_nonce_returns_internal_error2_for_sentinel() {
+        let err = get_nonce(98).unwrap_err();
+        let e = err.narrow::<crate::errors::InternalError1, _>().unwrap_err();
+        let internal = e.take::<crate::errors::InternalError2>();
+        assert_eq!(internal.0, "query timeout");
+    }
+}

server/crates/arbiter-terrors-poc/src/errors.rs

@@ -0,0 +1,130 @@
+use terrors::OneOf;
+
+// Wire boundary type — what would go into a proto response
+#[derive(Debug)]
+pub enum ProtoError {
+    NotRegistered,
+    InvalidSignature,
+    Internal(String), // Or Box<dyn Error>, who cares?
+}
+
+// Internal terrors types
+#[derive(Debug)]
+pub struct NotRegistered;
+#[derive(Debug)]
+pub struct InvalidSignature;
+#[derive(Debug)]
+pub struct InternalError1(pub String);
+#[derive(Debug)]
+pub struct InternalError2(pub String);
+
+// Errors can be scattered across the codebase as long as they implement Into<ProtoError>
+impl From<NotRegistered> for ProtoError {
+    fn from(_: NotRegistered) -> Self {
+        ProtoError::NotRegistered
+    }
+}
+
+impl From<InvalidSignature> for ProtoError {
+    fn from(_: InvalidSignature) -> Self {
+        ProtoError::InvalidSignature
+    }
+}
+
+impl From<InternalError1> for ProtoError {
+    fn from(e: InternalError1) -> Self {
+        ProtoError::Internal(e.0)
+    }
+}
+impl From<InternalError2> for ProtoError {
+    fn from(e: InternalError2) -> Self {
+        ProtoError::Internal(e.0)
+    }
+}
+
+/// Private helper trait for converting from OneOf<T...> where each T can be converted
+/// into the target type `O` by recursively narrowing until a match is found.
+/// 
+/// IDK why this isn't already in terrors.
+trait DrainInto<O>: terrors::TypeSet + Sized {
+    fn drain(e: OneOf<Self>) -> O;
+}
+
+macro_rules! impl_drain_into {
+    ($head:ident) => {
+        impl<$head, O> DrainInto<O> for ($head,)
+        where
+            $head: Into<O> + 'static,
+        {
+            fn drain(e: OneOf<($head,)>) -> O {
+                e.take().into()
+            }
+        }
+    };
+    ($head:ident, $($tail:ident),+) => {
+        impl<$head, $($tail),+, O> DrainInto<O> for ($head, $($tail),+)
+        where
+            $head: Into<O> + 'static,
+            ($($tail,)+): DrainInto<O>,
+        {
+            fn drain(e: OneOf<($head, $($tail),+)>) -> O {
+                match e.narrow::<$head, _>() {
+                    Ok(h) => h.into(),
+                    Err(rest) => <($($tail,)+)>::drain(rest),
+                }
+            }
+        }
+        impl_drain_into!($($tail),+);
+    };
+}
+
+// Generates impls for all tuple sizes from 1 up to 7 (restricted by terrors internal impl).
+// Each invocation produces one impl then recurses on the tail.
+impl_drain_into!(A, B, C, D, E, F, G, H, I);
+
+// Blanket From impl: body delegates to the recursive drain.
+impl<E: DrainInto<ProtoError>> From<OneOf<E>> for ProtoError {
+    fn from(e: OneOf<E>) -> Self {
+        E::drain(e)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn not_registered_converts_to_proto() {
+        let e: ProtoError = NotRegistered.into();
+        assert!(matches!(e, ProtoError::NotRegistered));
+    }
+
+    #[test]
+    fn invalid_signature_converts_to_proto() {
+        let e: ProtoError = InvalidSignature.into();
+        assert!(matches!(e, ProtoError::InvalidSignature));
+    }
+
+    #[test]
+    fn internal_converts_to_proto() {
+        let e: ProtoError = InternalError1("boom".into()).into();
+        assert!(matches!(e, ProtoError::Internal(msg) if msg == "boom"));
+    }
+
+    #[test]
+    fn one_of_remainder_converts_to_proto_invalid_signature() {
+        use terrors::OneOf;
+        let e: OneOf<(InvalidSignature, InternalError1)> = OneOf::new(InvalidSignature);
+        let proto = ProtoError::from(e);
+        assert!(matches!(proto, ProtoError::InvalidSignature));
+    }
+
+    #[test]
+    fn one_of_remainder_converts_to_proto_internal() {
+        use terrors::OneOf;
+        let e: OneOf<(InvalidSignature, InternalError1)> =
+            OneOf::new(InternalError1("db fail".into()));
+        let proto = ProtoError::from(e);
+        assert!(matches!(proto, ProtoError::Internal(msg) if msg == "db fail"));
+    }
+}

server/crates/arbiter-terrors-poc/src/main.rs

@@ -0,0 +1,43 @@
+mod auth;
+mod db;
+mod errors;
+
+use errors::ProtoError;
+
+fn run(id: u32, sig: &str) {
+    print!("authenticate(id={id}, sig={sig:?}) => ");
+    match auth::authenticate(id, sig) {
+        Ok(nonce) => println!("Ok(nonce={nonce})"),
+        Err(e) => match e.narrow::<errors::NotRegistered, _>() {
+            Ok(_) => println!("Err(NotRegistered) — handled locally"),
+            Err(remaining) => {
+                let proto = ProtoError::from(remaining);
+                println!("Err(ProtoError::{proto:?}) — forwarded to wire");
+            }
+        },
+    }
+}
+
+fn run_process(id: u32, sig: &str) {
+    print!("process_request(id={id}, sig={sig:?}) => ");
+    match auth::process_request(id, sig) {
+        Ok(s) => println!("Ok({s})"),
+        Err(e) => println!("Err(ProtoError::{e:?})"),
+    }
+}
+
+fn main() {
+    println!("=== authenticate ===");
+    run(0, "ok");   // NotRegistered
+    run(1, "bad");  // InvalidSignature
+    run(99, "ok");  // InternalError1
+    run(98, "ok");  // InternalError2
+    run(1, "ok");   // success
+
+    println!("\n=== process_request (Try chain) ===");
+    run_process(0, "ok");   // NotRegistered (guard, no I/O)
+    run_process(97, "ok");  // InternalError2 from load_config
+    run_process(99, "ok");  // InternalError1 from get_nonce
+    run_process(1, "bad");  // InvalidSignature from verify_signature
+    run_process(1, "ok");   // success
+}

server/crates/arbiter-tokens-registry/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "arbiter-tokens-registry"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+alloy.workspace = true

server/crates/arbiter-tokens-registry/src/evm/mod.rs

@@ -0,0 +1 @@
+pub mod nonfungible;

server/crates/arbiter-tokens-registry/src/evm/nonfungible.rs

@@ -0,0 +1,13 @@
+use alloy::primitives::{Address, ChainId, address};
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct TokenInfo {
+    pub name: &'static str,
+    pub symbol: &'static str,
+    pub decimals: u32,
+    pub contract: Address,
+    pub chain: ChainId,
+    pub logo_uri: Option<&'static str>,
+}
+
+include!("tokens.rs");