fix(useragent): unsafe, but working implementation of ml-dsa

useragent/lib/features/identity/hazmat_mldsa.dart

@@ -0,0 +1,71 @@
+import 'dart:convert';
+
+import 'package:arbiter/src/rust/api.dart';
+import 'package:cryptography/cryptography.dart';
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:arbiter/features/identity/pk_manager.dart';
+
+final storage = FlutterSecureStorage(
+  aOptions: AndroidOptions.biometric(
+    enforceBiometrics: true,
+    biometricPromptTitle: 'Authentication Required',
+  ),
+  mOptions: MacOsOptions(
+    accessibility: KeychainAccessibility.unlocked_this_device,
+    label: "Arbiter",
+    description: "Confirm your identity to access vault",
+    synchronizable: false,
+    accessControlFlags: [AccessControlFlag.userPresence],
+    usesDataProtectionKeychain: true,
+  ),
+);
+
+class HazmatMldsa extends KeyHandle {
+  final MldsaKey _key;
+
+  HazmatMldsa({required MldsaKey key}) : _key = key;
+
+  @override
+  Future<List<int>> getPublicKey() async {
+    final publicKey = await _key.getPublicKey();
+    return publicKey;
+  }
+
+  @override
+  Future<List<int>> sign(List<int> data) async {
+    final signature = await _key.sign(message: data);
+    return signature;
+  }
+}
+
+class HazmatMLDSAManager extends KeyManager {
+  static const _storageKey = "ed25519_identity";
+
+  @override
+  Future<KeyHandle> create() async {
+    final storedKey = await get();
+    if (storedKey != null) {
+      return storedKey;
+    }
+
+    final newKeypair = await MldsaKey.generate();
+    final keyBytes = await newKeypair.toBytes();
+
+    await storage.write(key: _storageKey, value: base64Encode(keyBytes));
+
+    return HazmatMldsa(key: newKeypair);
+  }
+
+  @override
+  Future<KeyHandle?> get() async {
+    final storedKeyPair = await storage.read(key: _storageKey);
+    if (storedKeyPair == null) {
+      return null;
+    }
+
+    final keyBytes = base64Decode(storedKeyPair);
+    final key = await MldsaKey.fromBytes(bytes: keyBytes);
+
+    return HazmatMldsa(key: key);
+  }
+}