refactor: Olm Exceptions

lib/encryption/encryption.dart

@@ -155,7 +155,7 @@ class Encryption {
     var canRequestSession = false;
     try {
       if (event.content['algorithm'] != AlgorithmTypes.megolmV1AesSha2) {
-        throw (DecryptError.UNKNOWN_ALGORITHM);
+        throw DecryptException(DecryptException.unknownAlgorithm);
       }
       final String sessionId = event.content['session_id'];
       final String senderKey = event.content['sender_key'];
@@ -163,10 +163,11 @@ class Encryption {
           keyManager.getInboundGroupSession(roomId, sessionId, senderKey);
       if (inboundGroupSession == null) {
         canRequestSession = true;
-        throw (DecryptError.UNKNOWN_SESSION);
+        throw DecryptException(DecryptException.unknownSession);
       }
       // decrypt errors here may mean we have a bad session key - others might have a better one
       canRequestSession = true;
+
       final decryptResult = inboundGroupSession.inboundGroupSession
           .decrypt(event.content['ciphertext']);
       canRequestSession = false;
@@ -179,7 +180,7 @@ class Encryption {
       if (haveIndex &&
           inboundGroupSession.indexes[messageIndexKey] != messageIndexValue) {
         Logs().e('[Decrypt] Could not decrypt due to a corrupted session.');
-        throw (DecryptError.CHANNEL_CORRUPTED);
+        throw DecryptException(DecryptException.channelCorrupted);
       }
       inboundGroupSession.indexes[messageIndexKey] = messageIndexValue;
       if (!haveIndex) {
@@ -197,7 +198,7 @@ class Encryption {
     } catch (exception) {
       // alright, if this was actually by our own outbound group session, we might as well clear it
       if (client.enableE2eeRecovery &&
-          exception != DecryptError.UNKNOWN_SESSION &&
+          exception.toString() != DecryptException.unknownSession &&
           (keyManager
                       .getOutboundGroupSession(roomId)
                       ?.outboundGroupSession
@@ -383,11 +384,30 @@ class Encryption {
   }
 }
 
-abstract class DecryptError {
-  static const String NOT_ENABLED = 'Encryption is not enabled in your client.';
-  static const String UNKNOWN_ALGORITHM = 'Unknown encryption algorithm.';
-  static const String UNKNOWN_SESSION =
+class DecryptException implements Exception {
+  String cause;
+  String libolmMessage;
+  DecryptException(this.cause, [this.libolmMessage]);
+
+  @override
+  String toString() => cause;
+
+  static const String notEnabled = 'Encryption is not enabled in your client.';
+  static const String unknownAlgorithm = 'Unknown encryption algorithm.';
+  static const String unknownSession =
       'The sender has not sent us the session key.';
-  static const String CHANNEL_CORRUPTED =
+  static const String channelCorrupted =
       'The secure channel with the sender was corrupted.';
+  static const String unableToDecryptWithAnyOlmSession =
+      'Unable to decrypt with any existing OLM session';
+  static const String senderDoesntMatch =
+      "Message was decrypted but sender doesn't match";
+  static const String recipientDoesntMatch =
+      "Message was decrypted but recipient doesn't match";
+  static const String ownFingerprintDoesntMatch =
+      "Message was decrypted but own fingerprint Key doesn't match";
+  static const String isntSentForThisDevice =
+      "The message isn't sent for this device";
+  static const String unknownMessageType = 'Unknown message type';
+  static const String decryptionFailed = 'Decryption failed';
 }

lib/encryption/olm_manager.dart

@@ -248,17 +248,17 @@ class OlmManager {
       return event;
     }
     if (event.content['algorithm'] != AlgorithmTypes.olmV1Curve25519AesSha2) {
-      throw ('Unknown algorithm: ${event.content['algorithm']}');
+      throw DecryptException(DecryptException.unknownAlgorithm);
     }
     if (!event.content['ciphertext'].containsKey(identityKey)) {
-      throw ("The message isn't sent for this device");
+      throw DecryptException(DecryptException.isntSentForThisDevice);
     }
     String plaintext;
     final String senderKey = event.content['sender_key'];
     final String body = event.content['ciphertext'][identityKey]['body'];
     final int type = event.content['ciphertext'][identityKey]['type'];
     if (type != 0 && type != 1) {
-      throw ('Unknown message type');
+      throw DecryptException(DecryptException.unknownMessageType);
     }
     final device = client.userDeviceKeys[event.sender]?.deviceKeys?.values
         ?.firstWhere((d) => d.curve25519Key == senderKey, orElse: () => null);
@@ -280,7 +280,12 @@ class OlmManager {
     if (existingSessions != null) {
       for (var session in existingSessions) {
         if (type == 0 && session.session.matches_inbound(body) == true) {
+          try {
             plaintext = session.session.decrypt(type, body);
+          } catch (e) {
+            throw DecryptException(
+                DecryptException.decryptionFailed, e.toString());
+          }
           updateSessionUsage(session);
           break;
         } else if (type == 1) {
@@ -295,7 +300,7 @@ class OlmManager {
       }
     }
     if (plaintext == null && type != 0) {
-      throw ('Unable to decrypt with any existing OLM session');
+      throw DecryptException(DecryptException.unableToDecryptWithAnyOlmSession);
     }
 
     if (plaintext == null) {
@@ -313,24 +318,24 @@ class OlmManager {
               lastReceived: DateTime.now(),
             )));
         updateSessionUsage();
-      } catch (_) {
+      } catch (e) {
         newSession?.free();
-        rethrow;
+        throw DecryptException(DecryptException.decryptionFailed, e.toString());
       }
     }
     final Map<String, dynamic> plainContent = json.decode(plaintext);
     if (plainContent.containsKey('sender') &&
         plainContent['sender'] != event.sender) {
-      throw ("Message was decrypted but sender doesn't match");
+      throw DecryptException(DecryptException.senderDoesntMatch);
     }
     if (plainContent.containsKey('recipient') &&
         plainContent['recipient'] != client.userID) {
-      throw ("Message was decrypted but recipient doesn't match");
+      throw DecryptException(DecryptException.recipientDoesntMatch);
     }
     if (plainContent['recipient_keys'] is Map &&
         plainContent['recipient_keys']['ed25519'] is String &&
         plainContent['recipient_keys']['ed25519'] != fingerprintKey) {
-      throw ("Message was decrypted but own fingerprint Key doesn't match");
+      throw DecryptException(DecryptException.ownFingerprintDoesntMatch);
     }
     return ToDeviceEvent(
       content: plainContent['content'],

lib/src/utils/event_localizations.dart

@@ -43,16 +43,16 @@ abstract class EventLocalizations {
       case MessageTypes.BadEncrypted:
         String errorText;
         switch (event.body) {
-          case DecryptError.CHANNEL_CORRUPTED:
+          case DecryptException.channelCorrupted:
             errorText = i18n.channelCorruptedDecryptError + '.';
             break;
-          case DecryptError.NOT_ENABLED:
+          case DecryptException.notEnabled:
             errorText = i18n.encryptionNotEnabled + '.';
             break;
-          case DecryptError.UNKNOWN_ALGORITHM:
+          case DecryptException.unknownAlgorithm:
             errorText = i18n.unknownEncryptionAlgorithm + '.';
             break;
-          case DecryptError.UNKNOWN_SESSION:
+          case DecryptException.unknownSession:
             errorText = i18n.noPermission + '.';
             break;
           default:

test/event_test.dart

@@ -302,7 +302,7 @@ void main() {
         'status': 2,
         'content': json.encode({
           'msgtype': 'm.bad.encrypted',
-          'body': DecryptError.UNKNOWN_SESSION,
+          'body': DecryptException.unknownSession,
           'can_request_session': true,
           'algorithm': AlgorithmTypes.megolmV1AesSha2,
           'ciphertext': 'AwgAEnACgAkLmt6qF84IK++J7UDH2Za1YVchHyprqTqsg...',