feat(server): auth comptes utilisateurs et tokens API (ticket #48)

Ajoute la couche application (ports, use cases), les entités du
domaine, l'endpoint api/auth_api.dart (register/login/logout) et son
câblage dans le router, le hashing de mot de passe et le service de
token (infrastructure/security), et l'adapter Postgres des repositories
d'auth s'appuyant sur la table users du ticket #49. dart pub get OK,
dart analyze clean, dart test 10/10 vert (test PostgreSQL réel skip
faute de Docker disponible dans ce sandbox). Logique d'auth et
middleware testés via repositories fake en mémoire ; les endpoints
HTTP register/login/logout n'ont pas pu être exercés de bout en bout
faute d'accès à un vrai PostgreSQL local.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/lib/api/auth_api.dart

@@ -0,0 +1,161 @@
+import 'dart:convert';
+
+import 'package:shelf/shelf.dart';
+
+import '../application/application.dart';
+import '../domain/domain.dart';
+
+const authenticatedRequestContextKey = 'gametime.authenticatedRequest';
+const bearerTokenContextKey = 'gametime.bearerToken';
+
+typedef AuthenticateToken =
+    Future<AuthenticatedRequest> Function({required String token});
+
+final class AuthApi {
+  const AuthApi({
+    required this.registerUser,
+    required this.login,
+    required this.logout,
+    required this.authenticateRequest,
+  });
+
+  final RegisterUserUseCase registerUser;
+  final LoginUseCase login;
+  final LogoutUseCase logout;
+  final AuthenticateRequestUseCase authenticateRequest;
+
+  Future<Response> register(Request request) async {
+    try {
+      final body = await _readJsonObject(request);
+      final user = await registerUser.execute(
+        email: _requiredString(body, 'email'),
+        password: _requiredString(body, 'password'),
+        displayName: _optionalString(body, 'displayName'),
+      );
+      return _jsonResponse(201, {'userId': user.id, 'email': user.email});
+    } on EmailAlreadyTakenException catch (error) {
+      return _errorResponse(409, error.message);
+    } on ValidationException catch (error) {
+      return _errorResponse(400, error.message);
+    } on FormatException catch (error) {
+      return _errorResponse(400, error.message);
+    }
+  }
+
+  Future<Response> loginUser(Request request) async {
+    try {
+      final body = await _readJsonObject(request);
+      final result = await login.execute(
+        email: _requiredString(body, 'email'),
+        password: _requiredString(body, 'password'),
+        userAgent: request.headers['user-agent'],
+        deviceLabel: _optionalString(body, 'deviceLabel'),
+      );
+      return _jsonResponse(200, {
+        'token': result.token,
+        'expiresAt': result.expiresAt.toIso8601String(),
+      });
+    } on InvalidCredentialsException catch (error) {
+      return _errorResponse(401, error.message);
+    } on ValidationException catch (error) {
+      return _errorResponse(400, error.message);
+    } on FormatException catch (error) {
+      return _errorResponse(400, error.message);
+    }
+  }
+
+  Future<Response> logoutUser(Request request) async {
+    final token = request.context[bearerTokenContextKey] as String?;
+    if (token == null) {
+      return _errorResponse(401, 'Unauthorized.');
+    }
+    try {
+      await logout.execute(token: token);
+      return Response(204);
+    } on UnauthorizedException catch (error) {
+      return _errorResponse(401, error.message);
+    }
+  }
+}
+
+Middleware authenticationMiddleware(AuthenticateToken authenticate) {
+  return (innerHandler) {
+    return (request) async {
+      final token = _bearerToken(request.headers['authorization']);
+      if (token == null) {
+        return _errorResponse(401, 'Missing bearer token.');
+      }
+
+      try {
+        final authenticated = await authenticate(token: token);
+        return innerHandler(
+          request.change(
+            context: {
+              authenticatedRequestContextKey: authenticated,
+              bearerTokenContextKey: token,
+            },
+          ),
+        );
+      } on UnauthorizedException catch (error) {
+        return _errorResponse(401, error.message);
+      }
+    };
+  };
+}
+
+AuthenticatedRequest? authenticatedRequestFrom(Request request) {
+  return request.context[authenticatedRequestContextKey]
+      as AuthenticatedRequest?;
+}
+
+String? _bearerToken(String? authorization) {
+  if (authorization == null) {
+    return null;
+  }
+  final parts = authorization.trim().split(RegExp(r'\s+'));
+  if (parts.length != 2 || parts.first.toLowerCase() != 'bearer') {
+    return null;
+  }
+  return parts[1].isEmpty ? null : parts[1];
+}
+
+Future<Map<String, Object?>> _readJsonObject(Request request) async {
+  final raw = await request.readAsString();
+  final decoded = jsonDecode(raw);
+  if (decoded is! Map<String, Object?>) {
+    throw const FormatException('Request body must be a JSON object.');
+  }
+  return decoded;
+}
+
+String _requiredString(Map<String, Object?> body, String key) {
+  final value = body[key];
+  if (value is! String || value.trim().isEmpty) {
+    throw FormatException('$key must be a non-empty string.');
+  }
+  return value;
+}
+
+String? _optionalString(Map<String, Object?> body, String key) {
+  final value = body[key];
+  if (value == null) {
+    return null;
+  }
+  if (value is! String) {
+    throw FormatException('$key must be a string.');
+  }
+  final trimmed = value.trim();
+  return trimmed.isEmpty ? null : trimmed;
+}
+
+Response _jsonResponse(int statusCode, Map<String, Object?> body) {
+  return Response(
+    statusCode,
+    body: jsonEncode(body),
+    headers: {'content-type': 'application/json'},
+  );
+}
+
+Response _errorResponse(int statusCode, String message) {
+  return _jsonResponse(statusCode, {'error': message});
+}

server/lib/api/router.dart

@@ -3,7 +3,9 @@ import 'dart:convert';
 import 'package:shelf/shelf.dart';
 import 'package:shelf_router/shelf_router.dart';
 
-Handler buildApiHandler() {
+import 'auth_api.dart';
+
+Handler buildApiHandler({AuthApi? authApi}) {
   final router = Router()
     ..get('/health', (Request request) {
       return Response.ok(
@@ -12,5 +14,17 @@ Handler buildApiHandler() {
       );
     });
 
+  if (authApi != null) {
+    router
+      ..post('/auth/register', authApi.register)
+      ..post('/auth/login', authApi.loginUser)
+      ..post(
+        '/auth/logout',
+        authenticationMiddleware(authApi.authenticateRequest.execute)(
+          authApi.logoutUser,
+        ),
+      );
+  }
+
   return const Pipeline().addMiddleware(logRequests()).addHandler(router.call);
 }

server/lib/application/README.md

@@ -2,4 +2,5 @@
 
 Server use cases, ports and API DTOs independent from Shelf and PostgreSQL.
 
-Concrete adapters are wired from `bin/server.dart`.
+Authentication use cases live here and depend only on repository/security
+ports. Concrete adapters are wired from `bin/server.dart`.

server/lib/application/application.dart

@@ -0,0 +1,2 @@
+export 'ports.dart';
+export 'use_cases.dart';

server/lib/application/ports.dart

@@ -0,0 +1,43 @@
+import '../domain/domain.dart';
+
+abstract interface class UserRepository {
+  Future<UserAccount?> findByEmail(String email);
+
+  Future<UserAccount?> findById(String id);
+
+  Future<void> insert(UserAccount user);
+
+  Future<void> updatePasswordHash({
+    required String userId,
+    required String passwordHash,
+    required DateTime updatedAt,
+  });
+}
+
+abstract interface class AuthSessionRepository {
+  Future<void> insert(AuthSession session);
+
+  Future<AuthSession?> findByTokenHash(String tokenHash);
+
+  Future<void> revoke({required String sessionId, required DateTime revokedAt});
+}
+
+abstract interface class PasswordHasher {
+  Future<String> hash(String password);
+
+  Future<bool> verify({required String password, required String passwordHash});
+}
+
+abstract interface class OpaqueTokenService {
+  String generateToken();
+
+  String hashToken(String token);
+}
+
+abstract interface class Clock {
+  DateTime now();
+}
+
+abstract interface class IdGenerator {
+  String newId();
+}

server/lib/application/use_cases.dart

@@ -0,0 +1,190 @@
+import '../domain/domain.dart';
+import 'ports.dart';
+
+const _minimumPasswordLength = 8;
+final _emailPattern = RegExp(r'^[^@\s]+@[^@\s]+\.[^@\s]+$');
+
+final class RegisterUserUseCase {
+  const RegisterUserUseCase({
+    required this.users,
+    required this.passwordHasher,
+    required this.clock,
+    required this.ids,
+  });
+
+  final UserRepository users;
+  final PasswordHasher passwordHasher;
+  final Clock clock;
+  final IdGenerator ids;
+
+  Future<UserAccount> execute({
+    required String email,
+    required String password,
+    String? displayName,
+  }) async {
+    final normalizedEmail = _validateEmail(email);
+    _validatePassword(password);
+
+    final existing = await users.findByEmail(normalizedEmail);
+    if (existing != null) {
+      throw const EmailAlreadyTakenException();
+    }
+
+    final now = clock.now().toUtc();
+    final user = UserAccount(
+      id: ids.newId(),
+      email: normalizedEmail,
+      passwordHash: await passwordHasher.hash(password),
+      displayName: _blankToNull(displayName),
+      createdAt: now,
+      updatedAt: now,
+    );
+    await users.insert(user);
+    return user;
+  }
+}
+
+final class LoginResult {
+  const LoginResult({
+    required this.user,
+    required this.session,
+    required this.token,
+  });
+
+  final UserAccount user;
+  final AuthSession session;
+  final String token;
+
+  DateTime get expiresAt => session.expiresAt;
+}
+
+final class LoginUseCase {
+  const LoginUseCase({
+    required this.users,
+    required this.sessions,
+    required this.passwordHasher,
+    required this.tokens,
+    required this.clock,
+    required this.ids,
+    this.sessionDuration = const Duration(days: 30),
+  });
+
+  final UserRepository users;
+  final AuthSessionRepository sessions;
+  final PasswordHasher passwordHasher;
+  final OpaqueTokenService tokens;
+  final Clock clock;
+  final IdGenerator ids;
+  final Duration sessionDuration;
+
+  Future<LoginResult> execute({
+    required String email,
+    required String password,
+    String? userAgent,
+    String? deviceLabel,
+  }) async {
+    final normalizedEmail = _validateEmail(email);
+    final user = await users.findByEmail(normalizedEmail);
+    if (user == null || user.isDisabled) {
+      throw const InvalidCredentialsException();
+    }
+    final verified = await passwordHasher.verify(
+      password: password,
+      passwordHash: user.passwordHash,
+    );
+    if (!verified) {
+      throw const InvalidCredentialsException();
+    }
+
+    final now = clock.now().toUtc();
+    final token = tokens.generateToken();
+    final session = AuthSession(
+      id: ids.newId(),
+      userId: user.id,
+      tokenHash: tokens.hashToken(token),
+      issuedAt: now,
+      expiresAt: now.add(sessionDuration),
+      userAgent: _blankToNull(userAgent),
+      deviceLabel: _blankToNull(deviceLabel),
+    );
+    await sessions.insert(session);
+    return LoginResult(user: user, session: session, token: token);
+  }
+}
+
+final class LogoutUseCase {
+  const LogoutUseCase({
+    required this.sessions,
+    required this.tokens,
+    required this.clock,
+  });
+
+  final AuthSessionRepository sessions;
+  final OpaqueTokenService tokens;
+  final Clock clock;
+
+  Future<void> execute({required String token}) async {
+    final session = await sessions.findByTokenHash(tokens.hashToken(token));
+    if (session == null || !session.isActiveAt(clock.now())) {
+      throw const UnauthorizedException();
+    }
+    await sessions.revoke(
+      sessionId: session.id,
+      revokedAt: clock.now().toUtc(),
+    );
+  }
+}
+
+final class AuthenticatedRequest {
+  const AuthenticatedRequest({required this.user, required this.session});
+
+  final UserAccount user;
+  final AuthSession session;
+}
+
+final class AuthenticateRequestUseCase {
+  const AuthenticateRequestUseCase({
+    required this.users,
+    required this.sessions,
+    required this.tokens,
+    required this.clock,
+  });
+
+  final UserRepository users;
+  final AuthSessionRepository sessions;
+  final OpaqueTokenService tokens;
+  final Clock clock;
+
+  Future<AuthenticatedRequest> execute({required String token}) async {
+    final session = await sessions.findByTokenHash(tokens.hashToken(token));
+    if (session == null || !session.isActiveAt(clock.now())) {
+      throw const UnauthorizedException();
+    }
+    final user = await users.findById(session.userId);
+    if (user == null || user.isDisabled) {
+      throw const UnauthorizedException();
+    }
+    return AuthenticatedRequest(user: user, session: session);
+  }
+}
+
+String _validateEmail(String email) {
+  final normalized = email.trim().toLowerCase();
+  if (!_emailPattern.hasMatch(normalized)) {
+    throw const ValidationException('Email format is invalid.');
+  }
+  return normalized;
+}
+
+void _validatePassword(String password) {
+  if (password.length < _minimumPasswordLength) {
+    throw const ValidationException(
+      'Password must contain at least 8 characters.',
+    );
+  }
+}
+
+String? _blankToNull(String? value) {
+  final trimmed = value?.trim();
+  return trimmed == null || trimmed.isEmpty ? null : trimmed;
+}

server/lib/domain/README.md

@@ -4,3 +4,5 @@ Pure server domain entities and invariants.
 
 This layer must not import Shelf, PostgreSQL adapters, Docker configuration or
 other infrastructure concerns.
+
+Current entities: `UserAccount` and `AuthSession`.

server/lib/domain/domain.dart

@@ -0,0 +1 @@
+export 'entities.dart';

server/lib/domain/entities.dart

@@ -0,0 +1,97 @@
+final class DomainException implements Exception {
+  const DomainException(this.message);
+
+  final String message;
+
+  @override
+  String toString() => message;
+}
+
+final class ValidationException extends DomainException {
+  const ValidationException(super.message);
+}
+
+final class EmailAlreadyTakenException extends DomainException {
+  const EmailAlreadyTakenException() : super('Email already taken.');
+}
+
+final class InvalidCredentialsException extends DomainException {
+  const InvalidCredentialsException() : super('Invalid credentials.');
+}
+
+final class UnauthorizedException extends DomainException {
+  const UnauthorizedException() : super('Unauthorized.');
+}
+
+final class UserAccount {
+  UserAccount({
+    required String id,
+    required String email,
+    required String passwordHash,
+    this.displayName,
+    required DateTime createdAt,
+    required DateTime updatedAt,
+    DateTime? disabledAt,
+  }) : id = _nonBlank(id, 'User id'),
+       email = _nonBlank(email, 'Email').toLowerCase(),
+       passwordHash = _nonBlank(passwordHash, 'Password hash'),
+       createdAt = createdAt.toUtc(),
+       updatedAt = updatedAt.toUtc(),
+       disabledAt = disabledAt?.toUtc();
+
+  final String id;
+  final String email;
+  final String passwordHash;
+  final String? displayName;
+  final DateTime createdAt;
+  final DateTime updatedAt;
+  final DateTime? disabledAt;
+
+  bool get isDisabled => disabledAt != null;
+}
+
+final class AuthSession {
+  AuthSession({
+    required String id,
+    required String userId,
+    required String tokenHash,
+    required DateTime issuedAt,
+    required DateTime expiresAt,
+    DateTime? revokedAt,
+    this.userAgent,
+    this.deviceLabel,
+  }) : id = _nonBlank(id, 'Auth session id'),
+       userId = _nonBlank(userId, 'User id'),
+       tokenHash = _nonBlank(tokenHash, 'Token hash'),
+       issuedAt = issuedAt.toUtc(),
+       expiresAt = expiresAt.toUtc(),
+       revokedAt = revokedAt?.toUtc() {
+    if (!this.expiresAt.isAfter(this.issuedAt)) {
+      throw const ValidationException(
+        'Auth session expiration must be after issue time.',
+      );
+    }
+  }
+
+  final String id;
+  final String userId;
+  final String tokenHash;
+  final DateTime issuedAt;
+  final DateTime expiresAt;
+  final DateTime? revokedAt;
+  final String? userAgent;
+  final String? deviceLabel;
+
+  bool isActiveAt(DateTime now) {
+    final instant = now.toUtc();
+    return revokedAt == null && expiresAt.isAfter(instant);
+  }
+}
+
+String _nonBlank(String value, String label) {
+  final trimmed = value.trim();
+  if (trimmed.isEmpty) {
+    throw ValidationException('$label must not be blank.');
+  }
+  return trimmed;
+}

server/lib/infrastructure/postgres/auth_repositories.dart

@@ -0,0 +1,199 @@
+import 'package:postgres/postgres.dart';
+
+import '../../application/application.dart';
+import '../../domain/domain.dart';
+
+final class PostgresUserRepository implements UserRepository {
+  const PostgresUserRepository(this.connection);
+
+  final Connection connection;
+
+  @override
+  Future<UserAccount?> findByEmail(String email) async {
+    final result = await connection.execute(
+      Sql.named('''
+        SELECT id, email, password_hash, display_name, created_at, updated_at,
+               disabled_at
+        FROM users
+        WHERE email = @email
+        LIMIT 1
+      '''),
+      parameters: {'email': email.trim().toLowerCase()},
+    );
+    return result.isEmpty ? null : _userFromRow(result.single);
+  }
+
+  @override
+  Future<UserAccount?> findById(String id) async {
+    final result = await connection.execute(
+      Sql.named('''
+        SELECT id, email, password_hash, display_name, created_at, updated_at,
+               disabled_at
+        FROM users
+        WHERE id = @id
+        LIMIT 1
+      '''),
+      parameters: {'id': id},
+    );
+    return result.isEmpty ? null : _userFromRow(result.single);
+  }
+
+  @override
+  Future<void> insert(UserAccount user) async {
+    await connection.execute(
+      Sql.named('''
+        INSERT INTO users (
+          id, email, password_hash, display_name, created_at, updated_at,
+          disabled_at
+        )
+        VALUES (
+          @id, @email, @password_hash, @display_name, @created_at,
+          @updated_at, @disabled_at
+        )
+      '''),
+      parameters: {
+        'id': user.id,
+        'email': user.email,
+        'password_hash': user.passwordHash,
+        'display_name': user.displayName,
+        'created_at': user.createdAt,
+        'updated_at': user.updatedAt,
+        'disabled_at': user.disabledAt,
+      },
+    );
+  }
+
+  @override
+  Future<void> updatePasswordHash({
+    required String userId,
+    required String passwordHash,
+    required DateTime updatedAt,
+  }) async {
+    await connection.execute(
+      Sql.named('''
+        UPDATE users
+        SET password_hash = @password_hash, updated_at = @updated_at
+        WHERE id = @user_id
+      '''),
+      parameters: {
+        'user_id': userId,
+        'password_hash': passwordHash,
+        'updated_at': updatedAt.toUtc(),
+      },
+    );
+  }
+}
+
+final class PostgresAuthSessionRepository implements AuthSessionRepository {
+  const PostgresAuthSessionRepository(this.connection);
+
+  final Connection connection;
+
+  @override
+  Future<void> insert(AuthSession session) async {
+    await connection.execute(
+      Sql.named('''
+        INSERT INTO auth_sessions (
+          id, user_id, token_hash, issued_at, expires_at, revoked_at,
+          user_agent, device_label
+        )
+        VALUES (
+          @id, @user_id, @token_hash, @issued_at, @expires_at, @revoked_at,
+          @user_agent, @device_label
+        )
+      '''),
+      parameters: {
+        'id': session.id,
+        'user_id': session.userId,
+        'token_hash': session.tokenHash,
+        'issued_at': session.issuedAt,
+        'expires_at': session.expiresAt,
+        'revoked_at': session.revokedAt,
+        'user_agent': session.userAgent,
+        'device_label': session.deviceLabel,
+      },
+    );
+  }
+
+  @override
+  Future<AuthSession?> findByTokenHash(String tokenHash) async {
+    final result = await connection.execute(
+      Sql.named('''
+        SELECT id, user_id, token_hash, issued_at, expires_at, revoked_at,
+               user_agent, device_label
+        FROM auth_sessions
+        WHERE token_hash = @token_hash
+        LIMIT 1
+      '''),
+      parameters: {'token_hash': tokenHash},
+    );
+    return result.isEmpty ? null : _authSessionFromRow(result.single);
+  }
+
+  @override
+  Future<void> revoke({
+    required String sessionId,
+    required DateTime revokedAt,
+  }) async {
+    await connection.execute(
+      Sql.named('''
+        UPDATE auth_sessions
+        SET revoked_at = @revoked_at
+        WHERE id = @id AND revoked_at IS NULL
+      '''),
+      parameters: {'id': sessionId, 'revoked_at': revokedAt.toUtc()},
+    );
+  }
+}
+
+UserAccount _userFromRow(dynamic row) {
+  final values = row.toColumnMap() as Map<String, Object?>;
+  return UserAccount(
+    id: _stringValue(values['id']),
+    email: _stringValue(values['email']),
+    passwordHash: _stringValue(values['password_hash']),
+    displayName: values['display_name'] as String?,
+    createdAt: _dateTimeValue(values['created_at']),
+    updatedAt: _dateTimeValue(values['updated_at']),
+    disabledAt: _nullableDateTimeValue(values['disabled_at']),
+  );
+}
+
+AuthSession _authSessionFromRow(dynamic row) {
+  final values = row.toColumnMap() as Map<String, Object?>;
+  return AuthSession(
+    id: _stringValue(values['id']),
+    userId: _stringValue(values['user_id']),
+    tokenHash: _stringValue(values['token_hash']),
+    issuedAt: _dateTimeValue(values['issued_at']),
+    expiresAt: _dateTimeValue(values['expires_at']),
+    revokedAt: _nullableDateTimeValue(values['revoked_at']),
+    userAgent: values['user_agent'] as String?,
+    deviceLabel: values['device_label'] as String?,
+  );
+}
+
+String _stringValue(Object? value) {
+  if (value == null) {
+    throw const FormatException('Expected non-null string value.');
+  }
+  return value.toString();
+}
+
+DateTime _dateTimeValue(Object? value) {
+  final result = _nullableDateTimeValue(value);
+  if (result == null) {
+    throw const FormatException('Expected non-null DateTime value.');
+  }
+  return result;
+}
+
+DateTime? _nullableDateTimeValue(Object? value) {
+  if (value == null) {
+    return null;
+  }
+  if (value is DateTime) {
+    return value.toUtc();
+  }
+  return DateTime.parse(value.toString()).toUtc();
+}

server/lib/infrastructure/postgres/postgres.dart

@@ -0,0 +1,2 @@
+export 'auth_repositories.dart';
+export 'postgres_database.dart';

server/lib/infrastructure/security/README.md

@@ -1,5 +1,7 @@
 # Security infrastructure
 
-Placeholder for password hashing, token signing and token verification.
+Password hashing uses PBKDF2-HMAC-SHA256 via `package:cryptography`, with a
+random per-password salt and encoded parameters in the stored hash.
 
-Authentication is planned for ticket #48.
+API tokens are opaque random base64url strings generated with `Random.secure()`.
+Only the SHA-256 hash of a token is persisted.

server/lib/infrastructure/security/password_hasher.dart

@@ -0,0 +1,88 @@
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:cryptography/cryptography.dart';
+
+import '../../application/application.dart';
+import '../../domain/domain.dart';
+
+final class Pbkdf2PasswordHasher implements PasswordHasher {
+  Pbkdf2PasswordHasher({
+    this.iterations = 210000,
+    this.saltLength = 16,
+    this.bits = 256,
+    Random? random,
+  }) : _random = random ?? Random.secure();
+
+  final int iterations;
+  final int saltLength;
+  final int bits;
+  final Random _random;
+
+  @override
+  Future<String> hash(String password) async {
+    final salt = List<int>.generate(saltLength, (_) => _random.nextInt(256));
+    final hash = await _derive(password, salt, iterations, bits);
+    return [
+      'pbkdf2_sha256',
+      iterations.toString(),
+      base64UrlEncode(salt),
+      base64UrlEncode(hash),
+    ].join(r'$');
+  }
+
+  @override
+  Future<bool> verify({
+    required String password,
+    required String passwordHash,
+  }) async {
+    final parts = passwordHash.split(r'$');
+    if (parts.length != 4 || parts[0] != 'pbkdf2_sha256') {
+      throw const ValidationException('Unsupported password hash format.');
+    }
+
+    final parsedIterations = int.tryParse(parts[1]);
+    if (parsedIterations == null || parsedIterations <= 0) {
+      throw const ValidationException('Invalid password hash iterations.');
+    }
+
+    final salt = base64Url.decode(parts[2]);
+    final expectedHash = base64Url.decode(parts[3]);
+    final actualHash = await _derive(
+      password,
+      salt,
+      parsedIterations,
+      expectedHash.length * 8,
+    );
+    return _constantTimeEquals(actualHash, expectedHash);
+  }
+
+  Future<List<int>> _derive(
+    String password,
+    List<int> salt,
+    int iterations,
+    int bits,
+  ) async {
+    final algorithm = Pbkdf2(
+      macAlgorithm: Hmac.sha256(),
+      iterations: iterations,
+      bits: bits,
+    );
+    final key = await algorithm.deriveKey(
+      secretKey: SecretKey(utf8.encode(password)),
+      nonce: salt,
+    );
+    return key.extractBytes();
+  }
+}
+
+bool _constantTimeEquals(List<int> left, List<int> right) {
+  if (left.length != right.length) {
+    return false;
+  }
+  var diff = 0;
+  for (var index = 0; index < left.length; index++) {
+    diff |= left[index] ^ right[index];
+  }
+  return diff == 0;
+}

server/lib/infrastructure/security/runtime_services.dart

@@ -0,0 +1,32 @@
+import 'dart:math';
+
+import '../../application/application.dart';
+
+final class SystemClock implements Clock {
+  const SystemClock();
+
+  @override
+  DateTime now() => DateTime.now().toUtc();
+}
+
+final class UuidV4Generator implements IdGenerator {
+  UuidV4Generator({Random? random}) : _random = random ?? Random.secure();
+
+  final Random _random;
+
+  @override
+  String newId() {
+    final bytes = List<int>.generate(16, (_) => _random.nextInt(256));
+    bytes[6] = (bytes[6] & 0x0f) | 0x40;
+    bytes[8] = (bytes[8] & 0x3f) | 0x80;
+    final hex = bytes.map((byte) => byte.toRadixString(16).padLeft(2, '0'));
+    final value = hex.join();
+    return [
+      value.substring(0, 8),
+      value.substring(8, 12),
+      value.substring(12, 16),
+      value.substring(16, 20),
+      value.substring(20),
+    ].join('-');
+  }
+}

server/lib/infrastructure/security/security.dart

@@ -0,0 +1,3 @@
+export 'password_hasher.dart';
+export 'runtime_services.dart';
+export 'token_service.dart';

server/lib/infrastructure/security/token_service.dart

@@ -0,0 +1,25 @@
+import 'dart:convert';
+import 'dart:math';
+
+import 'package:crypto/crypto.dart';
+
+import '../../application/application.dart';
+
+final class SecureOpaqueTokenService implements OpaqueTokenService {
+  SecureOpaqueTokenService({this.byteLength = 32, Random? random})
+    : _random = random ?? Random.secure();
+
+  final int byteLength;
+  final Random _random;
+
+  @override
+  String generateToken() {
+    final bytes = List<int>.generate(byteLength, (_) => _random.nextInt(256));
+    return base64UrlEncode(bytes).replaceAll('=', '');
+  }
+
+  @override
+  String hashToken(String token) {
+    return sha256.convert(utf8.encode(token)).toString();
+  }
+}