feat: Add events for commiting the device map and ratchet

lib/src/events.dart

@@ -1,11 +1,28 @@
+import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
 import 'package:omemo_dart/src/omemo/device.dart';
 
 abstract class OmemoEvent {}
 
+/// Triggered when a ratchet has been modified
+class RatchetModifiedEvent extends OmemoEvent {
+
+  RatchetModifiedEvent(this.jid, this.deviceId, this.ratchet);
+  final String jid;
+  final int deviceId;
+  final OmemoDoubleRatchet ratchet;
+}
+
+/// Triggered when the device map has been modified
+class DeviceMapModifiedEvent extends OmemoEvent {
+
+  DeviceMapModifiedEvent(this.map);
+  final Map<String, List<int>> map;
+}
+
 /// Triggered by the OmemoSessionManager when our own device bundle was modified
 /// and thus should be republished.
-class DeviceBundleModifiedEvent extends OmemoEvent {
+class DeviceModifiedEvent extends OmemoEvent {
 
-  DeviceBundleModifiedEvent(this.device);
+  DeviceModifiedEvent(this.device);
   final Device device;
 }

lib/src/omemo/sessionmanager.dart

@@ -130,6 +130,9 @@ class OmemoSessionManager {
         _deviceMap[jid]!.add(deviceId);
       }
 
+      // Commit the device map
+      _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
+
       // Add the ratchet session
       final key = RatchetMapKey(jid, deviceId);
       if (!_ratchetMap.containsKey(key)) {
@@ -138,6 +141,9 @@ class OmemoSessionManager {
         // TODO(PapaTutuWawa): What do we do now?
         throw Exception();
       }
+
+      // Commit the ratchet
+      _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
     });
   }
 
@@ -218,6 +224,9 @@ class OmemoSessionManager {
         final ratchet = _ratchetMap[ratchetKey]!;
         final ciphertext = (await ratchet.ratchetEncrypt(concatKey)).ciphertext;
 
+        // Commit the ratchet
+        _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
+        
         if (kex.isNotEmpty && kex.containsKey(deviceId)) {
           final k = kex[deviceId]!
             ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
@@ -274,9 +283,9 @@ class OmemoSessionManager {
       // Replace the OPK
       await _deviceLock.synchronized(() async {
         device = await device.replaceOnetimePrekey(kex.pkId!);
-        _eventStreamController.add(
-          DeviceBundleModifiedEvent(device),
-        );
+
+        // Commit the device
+        _eventStreamController.add(DeviceModifiedEvent(device));
       });
     } else {
       authMessage = OmemoAuthenticatedMessage.fromBuffer(decodedRawKey);
@@ -291,17 +300,22 @@ class OmemoSessionManager {
     }
 
     final message = OmemoMessage.fromBuffer(authMessage.message!);
-
     final ratchetKey = RatchetMapKey(senderJid, senderDeviceId);
-    final ratchet = _ratchetMap[ratchetKey]!;
-    List<int> keyAndHmac;
-    if (rawKey.kex) {
-      keyAndHmac = await ratchet.ratchetDecrypt(message, authMessage.writeToBuffer());
-    } else {
-      keyAndHmac = await ratchet.ratchetDecrypt(message, decodedRawKey);
-    }
-    final key = keyAndHmac.sublist(0, 32);
-    final hmac = keyAndHmac.sublist(32, 48);
+    List<int>? keyAndHmac;
+    await _lock.synchronized(() async {
+      final ratchet = _ratchetMap[ratchetKey]!;
+      if (rawKey.kex) {
+        keyAndHmac = await ratchet.ratchetDecrypt(message, authMessage.writeToBuffer());
+      } else {
+        keyAndHmac = await ratchet.ratchetDecrypt(message, decodedRawKey);
+      }
+
+      // Commit the ratchet
+      _eventStreamController.add(RatchetModifiedEvent(senderJid, senderDeviceId, ratchet));
+    });
+
+    final key = keyAndHmac!.sublist(0, 32);
+    final hmac = keyAndHmac!.sublist(32, 48);
     final derivedKeys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
 
     final computedHmac = await truncatedHmac(ciphertext, derivedKeys.authenticationKey);

test/omemo_test.dart

@@ -8,12 +8,18 @@ void main() {
       
     // Alice and Bob generate their sessions
     var deviceModified = false;
+    var ratchetModified = 0;
+    var deviceMapModified = 0;
     final aliceSession = await OmemoSessionManager.generateNewIdentity(opkAmount: 1);
     final bobSession = await OmemoSessionManager.generateNewIdentity(opkAmount: 1);
     final bobOpks = (await bobSession.getDevice()).opks.values.toList();
     bobSession.eventStream.listen((event) {
-      if (event is DeviceBundleModifiedEvent) {
+      if (event is DeviceModifiedEvent) {
         deviceModified = true;
+      } else if (event is RatchetModifiedEvent) {
+        ratchetModified++;
+      } else if (event is DeviceMapModifiedEvent) {
+        deviceMapModified++;
       }
     });
 
@@ -39,6 +45,11 @@ void main() {
       aliceMessage.encryptedKeys,
     );
     expect(messagePlaintext, bobMessage);
+    // The ratchet should be modified two times: Once for when the ratchet is created and
+    // other time for when the message is decrypted
+    expect(ratchetModified, 2);
+    // Bob's device map should be modified once
+    expect(deviceMapModified, 1);
     // The event should be triggered
     expect(deviceModified, true);
     // Bob should have replaced his OPK