feat(server): initial EVM functionality impl

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

@@ -0,0 +1,129 @@
+use std::fmt::Display;
+
+use alloy::primitives::{Address, Bytes, ChainId, U256};
+use chrono::{DateTime, Duration, Utc};
+use diesel::{result::QueryResult, sqlite::Sqlite};
+use diesel_async::AsyncConnection;
+use miette::Diagnostic;
+use thiserror::Error;
+
+use crate::db::models;
+
+pub mod ether_transfer;
+
+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,
+}
+
+#[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,
+}
+
+pub type DatabaseID = i32;
+
+pub struct GrantMetadata {
+    pub basic_grant_id: DatabaseID,
+    pub policy_grant_id: DatabaseID,
+}
+
+pub trait Policy: Sized {
+    type Grant: Send + 'static + Into<SpecificGrant>;
+    type Meaning: Display + Send + '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(
+        meaning: &Self::Meaning,
+        grant: &Self::Grant,
+        meta: &GrantMetadata,
+        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::Grant,
+        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<(Self::Grant, GrantMetadata)>>>;
+
+    // Records, updates or deletes rate limits
+    // In other words, records grant-specific things after transaction is executed
+    fn record_transaction(
+        context: &EvalContext,
+        grant: &GrantMetadata,
+        conn: &mut impl AsyncConnection<Backend = Sqlite>,
+    ) -> impl Future<Output = QueryResult<()>>;
+}
+
+// Classification of what transaction does
+pub enum SpecificMeaning {
+    EtherTransfer(ether_transfer::Meaning),
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct TransactionRateLimit {
+    pub count: u32,
+    pub window: Duration,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct BasicGrant {
+    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>,
+}
+
+pub enum SpecificGrant {
+    EtherTransfer(ether_transfer::Grant),
+}
+
+pub struct FullGrant<PolicyGrant> {
+    pub basic: BasicGrant,
+    pub specific: PolicyGrant,
+}