feat: Add a base trust manager class

lib/omemo_dart.dart

@@ -11,4 +11,6 @@ export 'src/omemo/encrypted_key.dart';
 export 'src/omemo/encryption_result.dart';
 export 'src/omemo/fingerprint.dart';
 export 'src/omemo/sessionmanager.dart';
+export 'src/trust/base.dart';
+//export 'src/trust/btbv.dart';
 export 'src/x3dh/x3dh.dart';

lib/src/omemo/sessionmanager.dart

@@ -19,6 +19,7 @@ import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
 import 'package:omemo_dart/src/protobuf/omemo_authenticated_message.dart';
 import 'package:omemo_dart/src/protobuf/omemo_key_exchange.dart';
 import 'package:omemo_dart/src/protobuf/omemo_message.dart';
+import 'package:omemo_dart/src/trust/base.dart';
 import 'package:omemo_dart/src/x3dh/x3dh.dart';
 import 'package:synchronized/synchronized.dart';
 
@@ -27,13 +28,13 @@ const omemoPayloadInfoString = 'OMEMO Payload';
 
 class OmemoSessionManager {
 
-  OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap)
+  OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap, this._trustManager)
     : _lock = Lock(),
       _deviceLock = Lock(),
       _eventStreamController = StreamController<OmemoEvent>.broadcast();
 
   /// Deserialise the OmemoSessionManager from JSON data [data].
-  factory OmemoSessionManager.fromJson(Map<String, dynamic> data) {
+  factory OmemoSessionManager.fromJson(Map<String, dynamic> data, TrustManager trustManager) {
     final ratchetMap = <RatchetMapKey, OmemoDoubleRatchet>{};
     for (final rawRatchet in data['sessions']! as List<Map<String, dynamic>>) {
       final key = RatchetMapKey(rawRatchet['jid']! as String, rawRatchet['deviceId']! as int);
@@ -41,20 +42,20 @@ class OmemoSessionManager {
       ratchetMap[key] = ratchet;
     }
 
-    // TODO(PapaTutuWawa): Handle Trust behaviour
     return OmemoSessionManager(
       Device.fromJson(data['device']! as Map<String, dynamic>),
       data['devices']! as Map<String, List<int>>,
       ratchetMap,
+      trustManager,
     );
   }
       
   /// Generate a new cryptographic identity.
-  static Future<OmemoSessionManager> generateNewIdentity(String jid, { int opkAmount = 100 }) async {
+  static Future<OmemoSessionManager> generateNewIdentity(String jid, TrustManager trustManager, { int opkAmount = 100 }) async {
     assert(opkAmount > 0, 'opkAmount must be bigger than 0.');
     final device = await Device.generateNewDevice(jid, opkAmount: opkAmount);
 
-    return OmemoSessionManager(device, {}, {});
+    return OmemoSessionManager(device, {}, {}, trustManager);
   }
   
   /// Lock for _ratchetMap and _bundleMap
@@ -75,6 +76,9 @@ class OmemoSessionManager {
   /// and its lock
   final Lock _deviceLock;
 
+  /// The trust manager
+  final TrustManager _trustManager;
+  
   /// A stream that receives events regarding the session
   Stream<OmemoEvent> get eventStream => _eventStreamController.stream;
 
@@ -218,6 +222,9 @@ class OmemoSessionManager {
       // We assume that the user already checked if the session exists
       for (final jid in jids) {
         for (final deviceId in _deviceMap[jid]!) {
+          // Only encrypt to devices that are trusted
+          if (!(await _trustManager.isTrusted(jid, deviceId))) continue;
+
           final ratchetKey = RatchetMapKey(jid, deviceId);
           final ratchet = _ratchetMap[ratchetKey]!;
           final ciphertext = (await ratchet.ratchetEncrypt(keyPayload)).ciphertext;

lib/src/trust/always.dart

@@ -0,0 +1,11 @@
+import 'package:meta/meta.dart';
+import 'package:omemo_dart/src/trust/base.dart';
+
+/// Only use for testing!
+/// An implementation of TrustManager that always trusts every device and thus
+/// has no internal state.
+@visibleForTesting
+class AlwaysTrustingTrustManager extends TrustManager {
+  @override
+  Future<bool> isTrusted(String jid, int deviceId) async => true;
+}

lib/src/trust/base.dart

@@ -0,0 +1,7 @@
+/// The base class for managing trust in OMEMO sessions.
+// ignore: one_member_abstracts
+abstract class TrustManager {
+  /// Return true when the device with id [deviceId] of Jid [jid] is trusted, i.e. if an
+  /// encrypted message should be sent to this device. If not, return false.
+  Future<bool> isTrusted(String jid, int deviceId);
+}

test/omemo_test.dart

@@ -1,4 +1,5 @@
 import 'package:omemo_dart/omemo_dart.dart';
+import 'package:omemo_dart/src/trust/always.dart';
 import 'package:test/test.dart';
 
 void main() {
@@ -10,8 +11,16 @@ void main() {
     var deviceModified = false;
     var ratchetModified = 0;
     var deviceMapModified = 0;
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
     final bobOpks = (await bobSession.getDevice()).opks.values.toList();
     bobSession.eventStream.listen((event) {
       if (event is DeviceModifiedEvent) {
@@ -83,10 +92,22 @@ void main() {
     const bobJid = 'bob@other.server.example';
       
     // Alice and Bob generate their sessions
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
     // Bob's other device
-    final bobSession2 = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final bobSession2 = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
 
     // Alice encrypts a message for Bob
     const messagePlaintext = 'Hello Bob!';
@@ -149,9 +170,21 @@ void main() {
     const bobJid = 'bob@other.server.example';
       
     // Alice and Bob generate their sessions
-    final aliceSession1 = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final aliceSession2 = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession1 = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final aliceSession2 = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
 
     // Alice encrypts a message for Bob
     const messagePlaintext = 'Hello Bob!';
@@ -192,8 +225,16 @@ void main() {
     const bobJid = 'bob@other.server.example';
       
     // Alice and Bob generate their sessions
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
 
     // Alice encrypts a message for Bob
     final aliceMessage = await aliceSession.encryptToJid(
@@ -225,7 +266,11 @@ void main() {
   test('Test rotating the Signed Prekey', () async {
     // Generate the session
     const aliceJid = 'alice@some.server';
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
 
     // Setup an event listener
     final oldDevice = await aliceSession.getDevice();
@@ -254,8 +299,16 @@ void main() {
     const bobJid = 'bob@other.server.example';
       
     // Alice and Bob generate their sessions
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
 
     // Alice encrypts a message for Bob
     const messagePlaintext = 'Hello Bob!';

test/serialisation_test.dart

@@ -1,10 +1,15 @@
 import 'package:omemo_dart/omemo_dart.dart';
+import 'package:omemo_dart/src/trust/always.dart';
 import 'package:test/test.dart';
 
 void main() {
   test('Test serialising and deserialising the Device', () async {
     // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity('user@test.server', opkAmount: 1);
+    final oldSession = await OmemoSessionManager.generateNewIdentity(
+      'user@test.server',
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
     final oldDevice = await oldSession.getDevice();
     final serialised = await oldDevice.toJson();
 
@@ -14,7 +19,11 @@ void main() {
 
   test('Test serialising and deserialising the Device after rotating the SPK', () async {
     // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity('user@test.server', opkAmount: 1);
+    final oldSession = await OmemoSessionManager.generateNewIdentity(
+      'user@test.server',
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
     final oldDevice = await (await oldSession.getDevice()).replaceSignedPrekey();
     final serialised = await oldDevice.toJson();
 
@@ -26,8 +35,16 @@ void main() {
     // Generate a random ratchet
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
-    final aliceSession = await OmemoSessionManager.generateNewIdentity(aliceJid, opkAmount: 1);
-    final bobSession = await OmemoSessionManager.generateNewIdentity(bobJid, opkAmount: 1);
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
     final aliceMessage = await aliceSession.encryptToJid(
       bobJid,
       'Hello Bob!',
@@ -50,8 +67,16 @@ void main() {
 
   test('Test serialising and deserialising the OmemoSessionManager', () async {
     // Generate a random session
-    final oldSession = await OmemoSessionManager.generateNewIdentity('a@server', opkAmount: 4);
-    final bobSession = await OmemoSessionManager.generateNewIdentity('b@other.server', opkAmount: 4);
+    final oldSession = await OmemoSessionManager.generateNewIdentity(
+      'a@server',
+      AlwaysTrustingTrustManager(),
+      opkAmount: 4,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      'b@other.server',
+      AlwaysTrustingTrustManager(),
+      opkAmount: 4,
+    );
     await oldSession.addSessionFromBundle(
       'bob@localhost',
       (await bobSession.getDevice()).id,
@@ -60,7 +85,10 @@ void main() {
 
     // Serialise and deserialise
     final serialised = await oldSession.toJson();
-    final newSession = OmemoSessionManager.fromJson(serialised);
+    final newSession = OmemoSessionManager.fromJson(
+      serialised,
+      AlwaysTrustingTrustManager(),
+    );
 
     final oldDevice = await oldSession.getDevice();
     final newDevice = await newSession.getDevice();