use mutex over all signal operations

lib/src/services/api.service.dart

@@ -35,6 +35,7 @@ import 'package:twonly/src/services/group.services.dart';
 import 'package:twonly/src/services/notifications/fcm.notifications.dart';
 import 'package:twonly/src/services/notifications/pushkeys.notifications.dart';
 import 'package:twonly/src/services/signal/identity.signal.dart';
+import 'package:twonly/src/services/signal/protocol_state.signal.dart';
 import 'package:twonly/src/services/signal/utils.signal.dart';
 import 'package:twonly/src/services/subscription.service.dart';
 import 'package:twonly/src/services/user.service.dart';
@@ -121,6 +122,7 @@ class ApiService {
       unawaited(syncFlameCounters());
       unawaited(setupNotificationWithUsers());
       unawaited(signalHandleNewServerConnection());
+      resetResyncedUsers();
       unawaited(fetchGroupStatesForUnjoinedGroups());
       unawaited(fetchMissingGroupPublicKey());
       unawaited(checkForDeletedUsernames());

lib/src/services/api/client2client/errors.c2c.dart

@@ -26,6 +26,8 @@ Future<void> handleErrorMessage(
           requested: Value(true),
         ),
       );
+    case EncryptedContent_ErrorMessages_Type.SESSION_OUT_OF_SYNC:
+      break; // The other user initiated a new signal session, so ignore the error in this case, as the new session works...
     // ignore: no_default_cases
     default:
       break;

lib/src/services/api/server_messages.api.dart

@@ -74,7 +74,6 @@ Future<void> handleServerMessage(server.ServerToClient msg) async {
 }
 
 DateTime lastPushKeyRequest = clock.now().subtract(const Duration(hours: 1));
-bool alreadyPerformedAnResync = false;
 
 Mutex protectReceiptCheck = Mutex();
 

lib/src/services/signal/encryption.signal.dart

@@ -3,21 +3,18 @@ import 'dart:typed_data';
 import 'package:libsignal_protocol_dart/libsignal_protocol_dart.dart';
 // ignore: implementation_imports
 import 'package:libsignal_protocol_dart/src/invalid_message_exception.dart';
-import 'package:mutex/mutex.dart';
 import 'package:twonly/src/model/protobuf/client/generated/messages.pb.dart';
 import 'package:twonly/src/services/api/messages.api.dart';
+import 'package:twonly/src/services/signal/protocol_state.signal.dart';
 import 'package:twonly/src/services/signal/session.signal.dart';
 import 'package:twonly/src/services/signal/utils.signal.dart';
 import 'package:twonly/src/utils/log.dart';
 
-/// This caused some troubles, so protection the encryption...
-final lockingSignalEncryption = Mutex();
-
 Future<CiphertextMessage?> signalEncryptMessage(
   int target,
   Uint8List plaintextContent,
 ) async {
-  return lockingSignalEncryption.protect<CiphertextMessage?>(() async {
+  return lockingSignalProtocol.protect<CiphertextMessage?>(() async {
     try {
       final signalStore = (await getSignalStore())!;
       final address = getSignalAddress(target);
@@ -30,14 +27,13 @@ Future<CiphertextMessage?> signalEncryptMessage(
   });
 }
 
-bool alreadyPerformedAnResync = false;
-
 Future<(EncryptedContent?, PlaintextContent_DecryptionErrorMessage_Type?)>
 signalDecryptMessage(
   int fromUserId,
   Uint8List encryptedContentRaw,
   int type,
 ) async {
+  return lockingSignalProtocol.protect(() async {
     try {
       final session = SessionCipher.fromStore(
         (await getSignalStore())!,
@@ -65,11 +61,11 @@ signalDecryptMessage(
       Log.warn(e);
       return (null, PlaintextContent_DecryptionErrorMessage_Type.PREKEY_UNKNOWN);
     } on InvalidMessageException catch (e) {
-    if (!alreadyPerformedAnResync) {
+      if (!resyncedUsers.contains(fromUserId)) {
         if (await handleSessionResync(fromUserId)) {
           // This flag prevents from resyncing the session the client received multiple new
           // messages from the server he could not decrypt
-        alreadyPerformedAnResync = true;
+          resyncedUsers.add(fromUserId);
 
           // This message contains a new PreKeyBundle establishing a new signal session
           await sendCipherText(
@@ -88,4 +84,5 @@ signalDecryptMessage(
       Log.error(e);
       return (null, PlaintextContent_DecryptionErrorMessage_Type.UNKNOWN);
     }
+  });
 }

lib/src/services/signal/identity.signal.dart

@@ -9,6 +9,7 @@ import 'package:twonly/src/constants/secure_storage.keys.dart';
 import 'package:twonly/src/database/signal/signal_protocol_store.dart';
 import 'package:twonly/src/model/json/signal_identity.model.dart';
 import 'package:twonly/src/services/signal/consts.signal.dart';
+import 'package:twonly/src/services/signal/protocol_state.signal.dart';
 import 'package:twonly/src/services/signal/utils.signal.dart';
 import 'package:twonly/src/services/user.service.dart';
 import 'package:twonly/src/utils/log.dart';
@@ -57,6 +58,7 @@ Future<void> signalHandleNewServerConnection() async {
 }
 
 Future<List<PreKeyRecord>> signalGetPreKeys() async {
+  return lockingSignalProtocol.protect(() async {
     final user = await getUser();
     if (user == null) return [];
 
@@ -72,6 +74,7 @@ Future<List<PreKeyRecord>> signalGetPreKeys() async {
       await signalStore.preKeyStore.storePreKey(p.id, p);
     }
     return preKeys;
+  });
 }
 
 Future<SignalIdentity?> getSignalIdentity() async {
@@ -136,6 +139,7 @@ Future<void> createIfNotExistsSignalIdentity() async {
 }
 
 Future<SignedPreKeyRecord?> _getNewSignalSignedPreKey() async {
+  return lockingSignalProtocol.protect(() async {
     var identityKeyPair = await getSignalIdentityKeyPair();
     final user = await getUser();
     final signalStore = await getSignalStore();
@@ -158,4 +162,5 @@ Future<SignedPreKeyRecord?> _getNewSignalSignedPreKey() async {
     await signalStore.storeSignedPreKey(signedPreKeyId, signedPreKey);
 
     return signedPreKey;
+  });
 }

lib/src/services/signal/protocol_state.signal.dart

@@ -0,0 +1,12 @@
+import 'package:mutex/mutex.dart';
+
+/// Unified lock for all Signal protocol operations (encryption, decryption, session management).
+final lockingSignalProtocol = Mutex();
+
+/// Tracking users who have already been resynced in the current session.
+final resyncedUsers = <int>{};
+
+/// Reset the resync tracking set.
+void resetResyncedUsers() {
+  resyncedUsers.clear();
+}

lib/src/services/signal/session.signal.dart

@@ -4,10 +4,12 @@ import 'package:libsignal_protocol_dart/libsignal_protocol_dart.dart';
 import 'package:twonly/locator.dart';
 import 'package:twonly/src/model/protobuf/api/websocket/server_to_client.pb.dart';
 import 'package:twonly/src/services/signal/consts.signal.dart';
+import 'package:twonly/src/services/signal/protocol_state.signal.dart';
 import 'package:twonly/src/services/signal/utils.signal.dart';
 import 'package:twonly/src/utils/log.dart';
 
 Future<bool> processSignalUserData(Response_UserData userData) async {
+  return lockingSignalProtocol.protect(() async {
     final SignalProtocolStore? signalStore = await getSignalStore();
 
     if (signalStore == null) {
@@ -72,13 +74,7 @@ Future<bool> processSignalUserData(Response_UserData userData) async {
       Log.error('could not process pre key bundle: $e');
       return false;
     }
-}
-
-Future<void> deleteSessionWithTarget(int target) async {
-  final signalStore = await getSignalStore();
-  if (signalStore == null) return;
-  final address = SignalProtocolAddress(target.toString(), defaultDeviceId);
-  await signalStore.sessionStore.deleteSession(address);
+  });
 }
 
 Future<Uint8List?> getPublicKeyFromContact(int contactId) async {