release: Bump version to 0.3.2

This was mostly caused by Dart not copying values but referencing
them. AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.

We know make some assumptions about received key exchanges, so this
needs some field testing.

.gitignore

@@ -12,6 +12,3 @@ pubspec.lock
 # NixOS
 .direnv
 .envrc
-
-# Protobuf build artifacts
-lib/protobuf/*.dart

.pubignore

@@ -0,0 +1 @@
+lib/protobuf

.woodpecker.yml

@@ -0,0 +1,11 @@
+pipeline:
+  lint:
+    image: dart:2.18.1
+    commands:
+      - dart pub get
+      - dart analyze --fatal-infos --fatal-warnings
+  test:
+    image: dart:2.18.1
+    commands:
+      - dart pub get
+      - dart test

CHANGELOG.md

@@ -9,3 +9,30 @@
 
 - Fix bug with the Double Ratchet causing only the initial message to be decryptable
 - Expose `getDeviceMap` as a developer usable function
+
+## 0.2.0
+
+- Add convenience functions `getDeviceId` and `getDeviceBundle`
+- Creating a new ratchet with an id for which we already have a ratchet will now overwrite the old ratchet
+- Ratchet now carry an "acknowledged" attribute
+
+## 0.2.1
+
+- Add `isRatchetAcknowledged`
+- Ratchets that are created due to accepting a kex are now unacknowledged
+
+## 0.3.0
+
+- Implement enabling and disabling ratchets via the TrustManager interface
+- Fix deserialization of the various objects
+- Remove the BTBV TrustManager's loadState method. Just use the constructor
+- Allow removing all ratchets for a given Jid
+- If an error occurs while decrypting the message, the ratchet will now be reset to its prior state
+- Fix a bug within the Varint encoding function. This should fix some occasional UnknownSignedPrekeyExceptions
+- Remove OmemoSessionManager's toJson and fromJson. Use toJsonWithoutSessions and fromJsonWithoutSessions. Restoring sessions is not out-of-scope for that function
+
+## 0.3.1
+
+- Fix a bug that caused the device's id to change when replacing a OPK
+- Every decryption failure now causes the ratchet to be restored to a pre-decryption state
+- Add method to get the device's fingerprint

README.md

@@ -28,7 +28,7 @@ Include `omemo_dart` in your `pubspec.yaml` like this:
 dependencies:
   omemo_dart:
     hosted: https://git.polynom.me/api/packages/PapaTutuWawa/pub
-    version: ^0.1.0
+    version: ^0.3.1
   # [...]
 
 # [...]

example/omemo_dart_example.dart

@@ -65,7 +65,7 @@ void main() async {
     // a new session. Let's also assume that Bob only has one device. We may, however,
     // add more bundles to newSessions, if we know of more.
     newSessions: [
-      await (await bobSession.getDevice()).toBundle(),
+      await bobSession.getDeviceBundle(),
     ],
   );
 
@@ -119,6 +119,8 @@ void main() async {
     aliceDevice.id,
     // The deserialised keys
     keys,
+    // Since the message was not delayed, we use the current time
+    DateTime.now().millisecondsSinceEpoch,
   );
 
   // All Bob has to do now is replace the OMEMO wrapper element 

lib/protobuf/schema.pb.dart

@@ -0,0 +1,263 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+import 'dart:core' as $core;
+
+import 'package:protobuf/protobuf.dart' as $pb;
+
+class OMEMOMessage extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(const $core.bool.fromEnvironment('protobuf.omit_message_names') ? '' : 'OMEMOMessage', createEmptyInstance: create)
+    ..a<$core.int>(1, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'n', $pb.PbFieldType.QU3)
+    ..a<$core.int>(2, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'pn', $pb.PbFieldType.QU3)
+    ..a<$core.List<$core.int>>(3, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'dhPub', $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(4, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'ciphertext', $pb.PbFieldType.OY)
+  ;
+
+  OMEMOMessage._() : super();
+  factory OMEMOMessage({
+    $core.int? n,
+    $core.int? pn,
+    $core.List<$core.int>? dhPub,
+    $core.List<$core.int>? ciphertext,
+  }) {
+    final _result = create();
+    if (n != null) {
+      _result.n = n;
+    }
+    if (pn != null) {
+      _result.pn = pn;
+    }
+    if (dhPub != null) {
+      _result.dhPub = dhPub;
+    }
+    if (ciphertext != null) {
+      _result.ciphertext = ciphertext;
+    }
+    return _result;
+  }
+  factory OMEMOMessage.fromBuffer($core.List<$core.int> i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromBuffer(i, r);
+  factory OMEMOMessage.fromJson($core.String i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromJson(i, r);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+  'Will be removed in next major version')
+  OMEMOMessage clone() => OMEMOMessage()..mergeFromMessage(this);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+  'Will be removed in next major version')
+  OMEMOMessage copyWith(void Function(OMEMOMessage) updates) => super.copyWith((message) => updates(message as OMEMOMessage)) as OMEMOMessage; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOMessage create() => OMEMOMessage._();
+  OMEMOMessage createEmptyInstance() => create();
+  static $pb.PbList<OMEMOMessage> createRepeated() => $pb.PbList<OMEMOMessage>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOMessage getDefault() => _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<OMEMOMessage>(create);
+  static OMEMOMessage? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.int get n => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set n($core.int v) { $_setUnsignedInt32(0, v); }
+  @$pb.TagNumber(1)
+  $core.bool hasN() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearN() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.int get pn => $_getIZ(1);
+  @$pb.TagNumber(2)
+  set pn($core.int v) { $_setUnsignedInt32(1, v); }
+  @$pb.TagNumber(2)
+  $core.bool hasPn() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearPn() => clearField(2);
+
+  @$pb.TagNumber(3)
+  $core.List<$core.int> get dhPub => $_getN(2);
+  @$pb.TagNumber(3)
+  set dhPub($core.List<$core.int> v) { $_setBytes(2, v); }
+  @$pb.TagNumber(3)
+  $core.bool hasDhPub() => $_has(2);
+  @$pb.TagNumber(3)
+  void clearDhPub() => clearField(3);
+
+  @$pb.TagNumber(4)
+  $core.List<$core.int> get ciphertext => $_getN(3);
+  @$pb.TagNumber(4)
+  set ciphertext($core.List<$core.int> v) { $_setBytes(3, v); }
+  @$pb.TagNumber(4)
+  $core.bool hasCiphertext() => $_has(3);
+  @$pb.TagNumber(4)
+  void clearCiphertext() => clearField(4);
+}
+
+class OMEMOAuthenticatedMessage extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(const $core.bool.fromEnvironment('protobuf.omit_message_names') ? '' : 'OMEMOAuthenticatedMessage', createEmptyInstance: create)
+    ..a<$core.List<$core.int>>(1, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'mac', $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(2, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'message', $pb.PbFieldType.QY)
+  ;
+
+  OMEMOAuthenticatedMessage._() : super();
+  factory OMEMOAuthenticatedMessage({
+    $core.List<$core.int>? mac,
+    $core.List<$core.int>? message,
+  }) {
+    final _result = create();
+    if (mac != null) {
+      _result.mac = mac;
+    }
+    if (message != null) {
+      _result.message = message;
+    }
+    return _result;
+  }
+  factory OMEMOAuthenticatedMessage.fromBuffer($core.List<$core.int> i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromBuffer(i, r);
+  factory OMEMOAuthenticatedMessage.fromJson($core.String i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromJson(i, r);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+  'Will be removed in next major version')
+  OMEMOAuthenticatedMessage clone() => OMEMOAuthenticatedMessage()..mergeFromMessage(this);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+  'Will be removed in next major version')
+  OMEMOAuthenticatedMessage copyWith(void Function(OMEMOAuthenticatedMessage) updates) => super.copyWith((message) => updates(message as OMEMOAuthenticatedMessage)) as OMEMOAuthenticatedMessage; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOAuthenticatedMessage create() => OMEMOAuthenticatedMessage._();
+  OMEMOAuthenticatedMessage createEmptyInstance() => create();
+  static $pb.PbList<OMEMOAuthenticatedMessage> createRepeated() => $pb.PbList<OMEMOAuthenticatedMessage>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOAuthenticatedMessage getDefault() => _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<OMEMOAuthenticatedMessage>(create);
+  static OMEMOAuthenticatedMessage? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.List<$core.int> get mac => $_getN(0);
+  @$pb.TagNumber(1)
+  set mac($core.List<$core.int> v) { $_setBytes(0, v); }
+  @$pb.TagNumber(1)
+  $core.bool hasMac() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearMac() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.List<$core.int> get message => $_getN(1);
+  @$pb.TagNumber(2)
+  set message($core.List<$core.int> v) { $_setBytes(1, v); }
+  @$pb.TagNumber(2)
+  $core.bool hasMessage() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearMessage() => clearField(2);
+}
+
+class OMEMOKeyExchange extends $pb.GeneratedMessage {
+  static final $pb.BuilderInfo _i = $pb.BuilderInfo(const $core.bool.fromEnvironment('protobuf.omit_message_names') ? '' : 'OMEMOKeyExchange', createEmptyInstance: create)
+    ..a<$core.int>(1, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'pkId', $pb.PbFieldType.QU3)
+    ..a<$core.int>(2, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'spkId', $pb.PbFieldType.QU3)
+    ..a<$core.List<$core.int>>(3, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'ik', $pb.PbFieldType.QY)
+    ..a<$core.List<$core.int>>(4, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'ek', $pb.PbFieldType.QY)
+    ..aQM<OMEMOAuthenticatedMessage>(5, const $core.bool.fromEnvironment('protobuf.omit_field_names') ? '' : 'message', subBuilder: OMEMOAuthenticatedMessage.create)
+  ;
+
+  OMEMOKeyExchange._() : super();
+  factory OMEMOKeyExchange({
+    $core.int? pkId,
+    $core.int? spkId,
+    $core.List<$core.int>? ik,
+    $core.List<$core.int>? ek,
+    OMEMOAuthenticatedMessage? message,
+  }) {
+    final _result = create();
+    if (pkId != null) {
+      _result.pkId = pkId;
+    }
+    if (spkId != null) {
+      _result.spkId = spkId;
+    }
+    if (ik != null) {
+      _result.ik = ik;
+    }
+    if (ek != null) {
+      _result.ek = ek;
+    }
+    if (message != null) {
+      _result.message = message;
+    }
+    return _result;
+  }
+  factory OMEMOKeyExchange.fromBuffer($core.List<$core.int> i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromBuffer(i, r);
+  factory OMEMOKeyExchange.fromJson($core.String i, [$pb.ExtensionRegistry r = $pb.ExtensionRegistry.EMPTY]) => create()..mergeFromJson(i, r);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.deepCopy] instead. '
+  'Will be removed in next major version')
+  OMEMOKeyExchange clone() => OMEMOKeyExchange()..mergeFromMessage(this);
+  @$core.Deprecated(
+  'Using this can add significant overhead to your binary. '
+  'Use [GeneratedMessageGenericExtensions.rebuild] instead. '
+  'Will be removed in next major version')
+  OMEMOKeyExchange copyWith(void Function(OMEMOKeyExchange) updates) => super.copyWith((message) => updates(message as OMEMOKeyExchange)) as OMEMOKeyExchange; // ignore: deprecated_member_use
+  $pb.BuilderInfo get info_ => _i;
+  @$core.pragma('dart2js:noInline')
+  static OMEMOKeyExchange create() => OMEMOKeyExchange._();
+  OMEMOKeyExchange createEmptyInstance() => create();
+  static $pb.PbList<OMEMOKeyExchange> createRepeated() => $pb.PbList<OMEMOKeyExchange>();
+  @$core.pragma('dart2js:noInline')
+  static OMEMOKeyExchange getDefault() => _defaultInstance ??= $pb.GeneratedMessage.$_defaultFor<OMEMOKeyExchange>(create);
+  static OMEMOKeyExchange? _defaultInstance;
+
+  @$pb.TagNumber(1)
+  $core.int get pkId => $_getIZ(0);
+  @$pb.TagNumber(1)
+  set pkId($core.int v) { $_setUnsignedInt32(0, v); }
+  @$pb.TagNumber(1)
+  $core.bool hasPkId() => $_has(0);
+  @$pb.TagNumber(1)
+  void clearPkId() => clearField(1);
+
+  @$pb.TagNumber(2)
+  $core.int get spkId => $_getIZ(1);
+  @$pb.TagNumber(2)
+  set spkId($core.int v) { $_setUnsignedInt32(1, v); }
+  @$pb.TagNumber(2)
+  $core.bool hasSpkId() => $_has(1);
+  @$pb.TagNumber(2)
+  void clearSpkId() => clearField(2);
+
+  @$pb.TagNumber(3)
+  $core.List<$core.int> get ik => $_getN(2);
+  @$pb.TagNumber(3)
+  set ik($core.List<$core.int> v) { $_setBytes(2, v); }
+  @$pb.TagNumber(3)
+  $core.bool hasIk() => $_has(2);
+  @$pb.TagNumber(3)
+  void clearIk() => clearField(3);
+
+  @$pb.TagNumber(4)
+  $core.List<$core.int> get ek => $_getN(3);
+  @$pb.TagNumber(4)
+  set ek($core.List<$core.int> v) { $_setBytes(3, v); }
+  @$pb.TagNumber(4)
+  $core.bool hasEk() => $_has(3);
+  @$pb.TagNumber(4)
+  void clearEk() => clearField(4);
+
+  @$pb.TagNumber(5)
+  OMEMOAuthenticatedMessage get message => $_getN(4);
+  @$pb.TagNumber(5)
+  set message(OMEMOAuthenticatedMessage v) { setField(5, v); }
+  @$pb.TagNumber(5)
+  $core.bool hasMessage() => $_has(4);
+  @$pb.TagNumber(5)
+  void clearMessage() => clearField(5);
+  @$pb.TagNumber(5)
+  OMEMOAuthenticatedMessage ensureMessage() => $_ensure(4);
+}
+

lib/protobuf/schema.pbenum.dart

@@ -0,0 +1,7 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+

lib/protobuf/schema.pbjson.dart

@@ -0,0 +1,48 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,deprecated_member_use_from_same_package,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+import 'dart:core' as $core;
+import 'dart:convert' as $convert;
+import 'dart:typed_data' as $typed_data;
+@$core.Deprecated('Use oMEMOMessageDescriptor instead')
+const OMEMOMessage$json = const {
+  '1': 'OMEMOMessage',
+  '2': const [
+    const {'1': 'n', '3': 1, '4': 2, '5': 13, '10': 'n'},
+    const {'1': 'pn', '3': 2, '4': 2, '5': 13, '10': 'pn'},
+    const {'1': 'dh_pub', '3': 3, '4': 2, '5': 12, '10': 'dhPub'},
+    const {'1': 'ciphertext', '3': 4, '4': 1, '5': 12, '10': 'ciphertext'},
+  ],
+};
+
+/// Descriptor for `OMEMOMessage`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOMessageDescriptor = $convert.base64Decode('CgxPTUVNT01lc3NhZ2USDAoBbhgBIAIoDVIBbhIOCgJwbhgCIAIoDVICcG4SFQoGZGhfcHViGAMgAigMUgVkaFB1YhIeCgpjaXBoZXJ0ZXh0GAQgASgMUgpjaXBoZXJ0ZXh0');
+@$core.Deprecated('Use oMEMOAuthenticatedMessageDescriptor instead')
+const OMEMOAuthenticatedMessage$json = const {
+  '1': 'OMEMOAuthenticatedMessage',
+  '2': const [
+    const {'1': 'mac', '3': 1, '4': 2, '5': 12, '10': 'mac'},
+    const {'1': 'message', '3': 2, '4': 2, '5': 12, '10': 'message'},
+  ],
+};
+
+/// Descriptor for `OMEMOAuthenticatedMessage`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOAuthenticatedMessageDescriptor = $convert.base64Decode('ChlPTUVNT0F1dGhlbnRpY2F0ZWRNZXNzYWdlEhAKA21hYxgBIAIoDFIDbWFjEhgKB21lc3NhZ2UYAiACKAxSB21lc3NhZ2U=');
+@$core.Deprecated('Use oMEMOKeyExchangeDescriptor instead')
+const OMEMOKeyExchange$json = const {
+  '1': 'OMEMOKeyExchange',
+  '2': const [
+    const {'1': 'pk_id', '3': 1, '4': 2, '5': 13, '10': 'pkId'},
+    const {'1': 'spk_id', '3': 2, '4': 2, '5': 13, '10': 'spkId'},
+    const {'1': 'ik', '3': 3, '4': 2, '5': 12, '10': 'ik'},
+    const {'1': 'ek', '3': 4, '4': 2, '5': 12, '10': 'ek'},
+    const {'1': 'message', '3': 5, '4': 2, '5': 11, '6': '.OMEMOAuthenticatedMessage', '10': 'message'},
+  ],
+};
+
+/// Descriptor for `OMEMOKeyExchange`. Decode as a `google.protobuf.DescriptorProto`.
+final $typed_data.Uint8List oMEMOKeyExchangeDescriptor = $convert.base64Decode('ChBPTUVNT0tleUV4Y2hhbmdlEhMKBXBrX2lkGAEgAigNUgRwa0lkEhUKBnNwa19pZBgCIAIoDVIFc3BrSWQSDgoCaWsYAyACKAxSAmlrEg4KAmVrGAQgAigMUgJlaxI0CgdtZXNzYWdlGAUgAigLMhouT01FTU9BdXRoZW50aWNhdGVkTWVzc2FnZVIHbWVzc2FnZQ==');

lib/protobuf/schema.pbserver.dart

@@ -0,0 +1,9 @@
+///
+//  Generated code. Do not modify.
+//  source: schema.proto
+//
+// @dart = 2.12
+// ignore_for_file: annotate_overrides,camel_case_types,constant_identifier_names,deprecated_member_use_from_same_package,directives_ordering,library_prefixes,non_constant_identifier_names,prefer_final_fields,return_of_invalid_type,unnecessary_const,unnecessary_import,unnecessary_this,unused_import,unused_shown_name
+
+export 'schema.pb.dart';
+

lib/src/double_ratchet/double_ratchet.dart

@@ -68,6 +68,8 @@ class OmemoDoubleRatchet {
     this.sessionAd,
     this.mkSkipped, // MKSKIPPED
     this.acknowledged,
+    this.kexTimestamp,
+    this.kex,
   );
   
   factory OmemoDoubleRatchet.fromJson(Map<String, dynamic> data) {
@@ -82,9 +84,11 @@ class OmemoDoubleRatchet {
       'ns': 0,
       'nr': 0,
       'pn': 0,
-      'ik_pub': 'base/64/encoded',
+      'ik_pub': null | 'base/64/encoded',
       'session_ad': 'base/64/encoded',
       'acknowledged': true | false,
+      'kex_timestamp': int,
+      'kex': 'base/64/encoded',
       'mkskipped': [
         {
           'key': 'base/64/encoded',
@@ -94,11 +98,20 @@ class OmemoDoubleRatchet {
       ]
     }
     */
-    final mkSkipped = <SkippedKey, List<int>>{};
+    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    for (final entry in data['mkskipped']! as List<Map<String, dynamic>>) {
+    //       such we need to convert the items by hand.
-      final key = SkippedKey.fromJson(entry);
+    final mkSkipped = Map<SkippedKey, List<int>>.fromEntries(
-      mkSkipped[key] = base64.decode(entry['key']! as String);
+      (data['mkskipped']! as List<dynamic>).map<MapEntry<SkippedKey, List<int>>>(
-    }
+        (entry) {
+          final map = entry as Map<String, dynamic>;
+          final key = SkippedKey.fromJson(map);
+          return MapEntry(
+            key,
+            base64.decode(map['key']! as String),
+          );
+        },
+      ),
+    );
     
     return OmemoDoubleRatchet(
       OmemoKeyPair.fromBytes(
@@ -120,6 +133,8 @@ class OmemoDoubleRatchet {
       base64.decode(data['session_ad']! as String),
       mkSkipped,
       data['acknowledged']! as bool,
+      data['kex_timestamp']! as int,
+      data['kex'] as String?,
     );
   }
   
@@ -151,6 +166,13 @@ class OmemoDoubleRatchet {
 
   final Map<SkippedKey, List<int>> mkSkipped;
 
+  /// The point in time at which we performed the kex exchange to create this ratchet.
+  /// Precision is milliseconds since epoch.
+  int kexTimestamp;
+
+  /// The key exchange that was used for initiating the session.
+  final String? kex;
+  
   /// Indicates whether we received an empty OMEMO message after building a session with
   /// the device. 
   bool acknowledged;
@@ -158,7 +180,7 @@ class OmemoDoubleRatchet {
   /// Create an OMEMO session using the Signed Pre Key [spk], the shared secret [sk] that
   /// was obtained using a X3DH and the associated data [ad] that was also obtained through
   /// a X3DH. [ik] refers to Bob's (the receiver's) IK public key.
-  static Future<OmemoDoubleRatchet> initiateNewSession(OmemoPublicKey spk, OmemoPublicKey ik, List<int> sk, List<int> ad) async {
+  static Future<OmemoDoubleRatchet> initiateNewSession(OmemoPublicKey spk, OmemoPublicKey ik, List<int> sk, List<int> ad, int timestamp) async {
     final dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     final dhr = spk;
     final rk  = await kdfRk(sk, await omemoDH(dhs, dhr, 0));
@@ -177,6 +199,8 @@ class OmemoDoubleRatchet {
       ad,
       {},
       false,
+      timestamp,
+      '',
     );
   }
 
@@ -184,7 +208,7 @@ class OmemoDoubleRatchet {
   /// Pre Key keypair [spk], the shared secret [sk] that was obtained through a X3DH and
   /// the associated data [ad] that was also obtained through a X3DH. [ik] refers to
   /// Alice's (the initiator's) IK public key.
-  static Future<OmemoDoubleRatchet> acceptNewSession(OmemoKeyPair spk, OmemoPublicKey ik, List<int> sk, List<int> ad) async {
+  static Future<OmemoDoubleRatchet> acceptNewSession(OmemoKeyPair spk, OmemoPublicKey ik, List<int> sk, List<int> ad, int kexTimestamp) async {
     return OmemoDoubleRatchet(
       spk,
       null,
@@ -197,7 +221,9 @@ class OmemoDoubleRatchet {
       ik,
       ad,
       {},
-      true,
+      false,
+      kexTimestamp,
+      null,
     );
   }
 
@@ -224,6 +250,8 @@ class OmemoDoubleRatchet {
       'session_ad': base64.encode(sessionAd),
       'mkskipped': mkSkippedSerialised,
       'acknowledged': acknowledged,
+      'kex_timestamp': kexTimestamp,
+      'kex': kex,
     };
   }
   
@@ -259,18 +287,18 @@ class OmemoDoubleRatchet {
   }
 
   Future<void> _dhRatchet(OmemoMessage header) async {
-    pn = header.n!;
+    pn = ns;
     ns = 0;
     nr = 0;
     dhr = OmemoPublicKey.fromBytes(header.dhPub!, KeyPairType.x25519);
 
     final newRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newRk;
+    rk = List.from(newRk);
-    ckr = newRk;
+    ckr = List.from(newRk);
     dhs = await OmemoKeyPair.generateNewPair(KeyPairType.x25519);
     final newNewRk = await kdfRk(rk, await omemoDH(dhs, dhr!, 0));
-    rk = newNewRk;
+    rk = List.from(newNewRk);
-    cks = newNewRk;
+    cks = List.from(newNewRk);
   }
 
   /// Encrypt [plaintext] using the Double Ratchet.
@@ -304,8 +332,8 @@ class OmemoDoubleRatchet {
     }
 
     final dhPubMatches = listsEqual(
-      header.dhPub ?? <int>[],
+      header.dhPub!,
-      await dhr?.getBytes() ?? <int>[],
+      (await dhr?.getBytes()) ?? <int>[],
     );
     if (!dhPubMatches) {
       await _skipMessageKeys(header.pn!);
@@ -321,12 +349,64 @@ class OmemoDoubleRatchet {
     return decrypt(mk, ciphertext, concat([sessionAd, header.writeToBuffer()]), sessionAd);
   }
 
+  OmemoDoubleRatchet clone() {
+    return OmemoDoubleRatchet(
+      dhs,
+      dhr,
+      rk,
+      cks != null ?
+        List<int>.from(cks!) :
+        null,
+      ckr != null ?
+        List<int>.from(ckr!) :
+        null,
+      ns,
+      nr,
+      pn,
+      ik,
+      sessionAd,
+      Map<SkippedKey, List<int>>.from(mkSkipped),
+      acknowledged,
+      kexTimestamp,
+      kex,
+    );
+  }
+
+  OmemoDoubleRatchet cloneWithKex(String kex) {
+    return OmemoDoubleRatchet(
+      dhs,
+      dhr,
+      rk,
+      cks != null ?
+        List<int>.from(cks!) :
+        null,
+      ckr != null ?
+        List<int>.from(ckr!) :
+        null,
+      ns,
+      nr,
+      pn,
+      ik,
+      sessionAd,
+      Map<SkippedKey, List<int>>.from(mkSkipped),
+      acknowledged,
+      kexTimestamp,
+      kex,
+    );
+  }
+  
   @visibleForTesting
   Future<bool> equals(OmemoDoubleRatchet other) async {
-    // ignore: invalid_use_of_visible_for_testing_member
+    final dhrMatch = dhr == null ?
-    final dhrMatch = dhr == null ? other.dhr == null : await dhr!.equals(other.dhr!);
+      other.dhr == null :
-    final ckrMatch = ckr == null ? other.ckr == null : listsEqual(ckr!, other.ckr!);
+      // ignore: invalid_use_of_visible_for_testing_member
-    final cksMatch = cks == null ? other.cks == null : listsEqual(cks!, other.cks!);
+      other.dhr != null && await dhr!.equals(other.dhr!);
+    final ckrMatch = ckr == null ?
+      other.ckr == null :
+      other.ckr != null && listsEqual(ckr!, other.ckr!);
+    final cksMatch = cks == null ?
+      other.cks == null :
+      other.cks != null && listsEqual(cks!, other.cks!);
  
     // ignore: invalid_use_of_visible_for_testing_member
     final dhsMatch = await dhs.equals(other.dhs);
@@ -342,6 +422,7 @@ class OmemoDoubleRatchet {
       ns == other.ns &&
       nr == other.nr &&
       pn == other.pn &&
-      listsEqual(sessionAd, other.sessionAd);
+      listsEqual(sessionAd, other.sessionAd) &&
+      kexTimestamp == other.kexTimestamp;
   }
 }

lib/src/errors.dart

@@ -30,3 +30,16 @@ class NoDecryptionKeyException implements Exception {
 class UnknownSignedPrekeyException implements Exception {
   String errMsg() => 'Unknown Signed Prekey used.';
 }
+
+/// Triggered by the Session Manager when the received Key Exchange message does not meet
+/// the requirement that a key exchange, given that the ratchet already exists, must be
+/// sent after its creation.
+class InvalidKeyExchangeException implements Exception {
+  String errMsg() => 'The key exchange was sent before the last kex finished';
+}
+
+/// Triggered by the Session Manager when a message's sequence number is smaller than we
+/// expect it to be.
+class MessageAlreadyDecryptedException implements Exception {
+  String errMsg() => 'The message has already been decrypted';
+}

lib/src/helpers.dart

@@ -73,3 +73,7 @@ OmemoKeyPair? decodeKeyPairIfNotNull(String? pk, String? sk, KeyPairType type) {
     type,
   );
 }
+
+int getTimestamp() {
+  return DateTime.now().millisecondsSinceEpoch;
+}

lib/src/omemo/device.dart

@@ -49,14 +49,23 @@ class Device {
       ]
     }
     */
-    final opks = <int, OmemoKeyPair>{};
+    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
-    for (final opk in data['opks']! as List<Map<String, dynamic>>) {
+    //       such we need to convert the items by hand.
-      opks[opk['id']! as int] = OmemoKeyPair.fromBytes(
+    final opks = Map<int, OmemoKeyPair>.fromEntries(
-        base64.decode(opk['public']! as String),
+      (data['opks']! as List<dynamic>).map<MapEntry<int, OmemoKeyPair>>(
-        base64.decode(opk['private']! as String),
+        (opk) {
-        KeyPairType.x25519,
+          final map = opk as Map<String, dynamic>;
-      );
+          return MapEntry(
-    }
+            map['id']! as int,
+            OmemoKeyPair.fromBytes(
+              base64.decode(map['public']! as String),
+              base64.decode(map['private']! as String),
+              KeyPairType.x25519,
+            ),
+          );
+        },
+      ),
+    );
 
     return Device(
       data['jid']! as String,
@@ -131,7 +140,7 @@ class Device {
     
     return Device(
       jid,
-      id,
+      this.id,
       ik,
       spk,
       spkId,

lib/src/omemo/ratchet_map_key.dart

@@ -4,9 +4,24 @@ import 'package:meta/meta.dart';
 class RatchetMapKey {
 
   const RatchetMapKey(this.jid, this.deviceId);
+
+  factory RatchetMapKey.fromJsonKey(String key) {
+    final parts = key.split(':');
+    final deviceId = int.parse(parts.first);
+
+    return RatchetMapKey(
+      parts.sublist(1).join(':'),
+      deviceId,
+    );
+  }
+
   final String jid;
   final int deviceId;
 
+  String toJsonKey() {
+    return '$deviceId:$jid';
+  }
+  
   @override
   bool operator ==(Object other) {
     return other is RatchetMapKey && jid == other.jid && deviceId == other.deviceId;

lib/src/omemo/sessionmanager.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'package:collection/collection.dart';
 import 'package:cryptography/cryptography.dart';
 import 'package:hex/hex.dart';
+import 'package:logging/logging.dart';
 import 'package:meta/meta.dart';
 import 'package:omemo_dart/src/crypto.dart';
 import 'package:omemo_dart/src/double_ratchet/double_ratchet.dart';
@@ -31,31 +32,28 @@ class OmemoSessionManager {
   OmemoSessionManager(this._device, this._deviceMap, this._ratchetMap, this._trustManager)
     : _lock = Lock(),
       _deviceLock = Lock(),
-      _eventStreamController = StreamController<OmemoEvent>.broadcast();
+      _eventStreamController = StreamController<OmemoEvent>.broadcast(),
-
+      _log = Logger('OmemoSessionManager');
-  /// Deserialise the OmemoSessionManager from JSON data [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);
-      final ratchet = OmemoDoubleRatchet.fromJson(rawRatchet['ratchet']! as Map<String, dynamic>);
-      ratchetMap[key] = ratchet;
-    }
-
-    return OmemoSessionManager(
-      Device.fromJson(data['device']! as Map<String, dynamic>),
-      data['devices']! as Map<String, List<int>>,
-      ratchetMap,
-      trustManager,
-    );
-  }
 
   /// Deserialise the OmemoSessionManager from JSON data [data] that does not contain
   /// the ratchet sessions.
-  factory OmemoSessionManager.fromJsonWithoutSessions(Map<String, dynamic> data, Map<RatchetMapKey, OmemoDoubleRatchet> ratchetMap, TrustManager trustManager) {
+  factory OmemoSessionManager.fromJsonWithoutSessions(
+    Map<String, dynamic> data,
+    Map<RatchetMapKey, OmemoDoubleRatchet> ratchetMap,
+    TrustManager trustManager,
+  ) {
+    // NOTE: Dart has some issues with just casting a List<dynamic> to List<Map<...>>, as
+    //       such we need to convert the items by hand.
     return OmemoSessionManager(
       Device.fromJson(data['device']! as Map<String, dynamic>),
-      data['devices']! as Map<String, List<int>>,
+      (data['devices']! as Map<String, dynamic>).map<String, List<int>>(
+        (key, value) {
+          return MapEntry(
+            key,
+            (value as List<dynamic>).map<int>((i) => i as int).toList(),
+          );
+        }
+      ),
       ratchetMap,
       trustManager,
     );
@@ -69,6 +67,9 @@ class OmemoSessionManager {
     return OmemoSessionManager(device, {}, {}, trustManager);
   }
 
+  /// Logging
+  Logger _log;
+  
   /// Lock for _ratchetMap and _bundleMap
   final Lock _lock;
 
@@ -96,12 +97,19 @@ class OmemoSessionManager {
 
   /// Returns our own device.
   Future<Device> getDevice() async {
-    Device? dev;
+    return _deviceLock.synchronized(() => _device);
-    await _deviceLock.synchronized(() async {
+  }
-      dev = _device;
-    });
 
-    return dev!;
+  /// Returns the id attribute of our own device. This is just a short-hand for
+  /// ```await (session.getDevice()).id```.
+  Future<int> getDeviceId() async {
+    return _deviceLock.synchronized(() => _device.id);
+  }
+
+  /// Returns the device as an OmemoBundle. This is just a short-hand for
+  /// ```await (await session.getDevice()).toBundle()```.
+  Future<OmemoBundle> getDeviceBundle() async {
+    return _deviceLock.synchronized(() async => _device.toBundle());
   }
   
   /// Add a session [ratchet] with the [deviceId] to the internal tracking state.
@@ -110,21 +118,22 @@ class OmemoSessionManager {
       // Add the bundle Id
       if (!_deviceMap.containsKey(jid)) {
         _deviceMap[jid] = [deviceId];
-      } else {
-        _deviceMap[jid]!.add(deviceId);
-      }
 
-      // Commit the device map
+        // Commit the device map
-      _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
+        _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
+      } else {
+        // Prevent having the same device multiple times in the list
+        if (!_deviceMap[jid]!.contains(deviceId)) {
+          _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)) {
+      _ratchetMap[key] = ratchet;
-        _ratchetMap[key] = ratchet;
-      } else {
-        // TODO(PapaTutuWawa): What do we do now?
-        throw Exception();
-      }
 
       // Commit the ratchet
       _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
@@ -145,6 +154,7 @@ class OmemoSessionManager {
       bundle.ik,
       kexResult.sk,
       kexResult.ad,
+      getTimestamp(),
     );
 
     await _trustManager.onNewSession(jid, deviceId);
@@ -160,27 +170,29 @@ class OmemoSessionManager {
   /// Build a new session with the user at [jid] with the device [deviceId] using data
   /// from the key exchange [kex]. In case [kex] contains an unknown Signed Prekey
   /// identifier an UnknownSignedPrekeyException will be thrown.
-  Future<void> _addSessionFromKeyExchange(String jid, int deviceId, OmemoKeyExchange kex) async {
+  Future<OmemoDoubleRatchet> _addSessionFromKeyExchange(String jid, int deviceId, OmemoKeyExchange kex) async {
     // Pick the correct SPK
     final device = await getDevice();
-    OmemoKeyPair? spk;
+    final spk = await _lock.synchronized(() async {
-    if (kex.spkId == device.spkId) {
+      if (kex.spkId == _device.spkId) {
-      spk = device.spk;
+        return _device.spk;
-    } else if (kex.spkId == device.oldSpkId) {
+      } else if (kex.spkId == _device.oldSpkId) {
-      spk = device.oldSpk;
+        return _device.oldSpk;
-    } else {
+      }
+
+      return null;
+    });
+    if (spk == null) {
       throw UnknownSignedPrekeyException();
     }
     
-    assert(spk != null, 'The used SPK must be found');
-    
     final kexResult = await x3dhFromInitialMessage(
       X3DHMessage(
         OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
         OmemoPublicKey.fromBytes(kex.ek!, KeyPairType.x25519),
         kex.pkId!,
       ),
-      spk!,
+      spk,
       device.opks.values.elementAt(kex.pkId!),
       device.ik,
     );
@@ -189,10 +201,10 @@ class OmemoSessionManager {
       OmemoPublicKey.fromBytes(kex.ik!, KeyPairType.ed25519),
       kexResult.sk,
       kexResult.ad,
+      getTimestamp(),
     );
 
-    await _trustManager.onNewSession(jid, deviceId);
+    return ratchet;
-    await _addSession(jid, deviceId, ratchet);
   }
 
   /// Like [encryptToJids] but only for one Jid [jid].
@@ -229,7 +241,11 @@ class OmemoSessionManager {
     final kex = <int, OmemoKeyExchange>{};
     if (newSessions != null) {
       for (final newSession in newSessions) {
-        kex[newSession.id] = await addSessionFromBundle(newSession.jid, newSession.id, newSession);
+        kex[newSession.id] = await addSessionFromBundle(
+          newSession.jid,
+          newSession.id,
+          newSession,
+        );
       }
     }
     
@@ -241,27 +257,59 @@ class OmemoSessionManager {
           if (plaintext != null) {
             // Only encrypt to devices that are trusted
             if (!(await _trustManager.isTrusted(jid, deviceId))) continue;
+
+            // Onyl encrypt to devices that are enabled
+            if (!(await _trustManager.isEnabled(jid, deviceId))) continue;
           }
 
           final ratchetKey = RatchetMapKey(jid, deviceId);
-          final ratchet = _ratchetMap[ratchetKey]!;
+          var ratchet = _ratchetMap[ratchetKey]!;
           final ciphertext = (await ratchet.ratchetEncrypt(keyPayload)).ciphertext;
  
-          // Commit the ratchet
-          _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
-          
           if (kex.isNotEmpty && kex.containsKey(deviceId)) {
+            // The ratchet did not exist
             final k = kex[deviceId]!
               ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
+            final buffer = base64.encode(k.writeToBuffer());
             encryptedKeys.add(
               EncryptedKey(
                 jid,
                 deviceId,
-                base64.encode(k.writeToBuffer()),
+                buffer,
                 true,
               ),
             );
+
+            ratchet = ratchet.cloneWithKex(buffer);
+            _ratchetMap[ratchetKey] = ratchet;
+          } else if (!ratchet.acknowledged) {
+            // The ratchet exists but is not acked
+            if (ratchet.kex != null) {
+              final oldKex = OmemoKeyExchange.fromBuffer(base64.decode(ratchet.kex!))
+              ..message = OmemoAuthenticatedMessage.fromBuffer(ciphertext);
+              
+              encryptedKeys.add(
+                EncryptedKey(
+                  jid,
+                  deviceId,
+                  base64.encode(oldKex.writeToBuffer()),
+                  true,
+                ),
+              );
+            } else {
+              // The ratchet is not acked but we don't have the old key exchange
+              _log.warning('Ratchet for $jid:$deviceId is not acked but the kex attribute is null');
+              encryptedKeys.add(
+                EncryptedKey(
+                  jid,
+                  deviceId,
+                  base64.encode(ciphertext),
+                  false,
+                ),
+              );
+            }
           } else {
+            // The ratchet exists and is acked
             encryptedKeys.add(
               EncryptedKey(
                 jid,
@@ -271,6 +319,9 @@ class OmemoSessionManager {
               ),
             );
           }
+
+          // Commit the ratchet
+          _eventStreamController.add(RatchetModifiedEvent(jid, deviceId, ratchet));
         }
       }
     });
@@ -281,16 +332,57 @@ class OmemoSessionManager {
     );
   }
 
+  /// In case a decryption error occurs, the Double Ratchet spec says to just restore
+  /// the ratchet to its old state. As such, this function restores the ratchet at
+  /// [mapKey] with [oldRatchet].
+  Future<void> _restoreRatchet(RatchetMapKey mapKey, OmemoDoubleRatchet oldRatchet) async {
+    await _lock.synchronized(() {
+      _log.finest('Restoring ratchet ${mapKey.jid}:${mapKey.deviceId} to ${oldRatchet.nr}');
+      _ratchetMap[mapKey] = oldRatchet;
+
+      // Commit the ratchet
+      _eventStreamController.add(
+        RatchetModifiedEvent(
+          mapKey.jid,
+          mapKey.deviceId,
+          oldRatchet,
+        ),
+      );
+    });
+  }
+
+  Future<String?> _decryptAndVerifyHmac(List<int>? ciphertext, List<int> keyAndHmac) async {
+    // Empty OMEMO messages should just have the key decrypted and/or session set up.
+    if (ciphertext == null) {
+      return null;
+    }
+    
+    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);
+    if (!listsEqual(hmac, computedHmac)) {
+      throw InvalidMessageHMACException();
+    }
+    
+    return utf8.decode(
+      await aes256CbcDecrypt(ciphertext, derivedKeys.encryptionKey, derivedKeys.iv),
+    );
+  }
+  
   /// Attempt to decrypt [ciphertext]. [keys] refers to the <key /> elements inside the
   /// <keys /> element with a "jid" attribute matching our own. [senderJid] refers to the
   /// bare Jid of the sender. [senderDeviceId] refers to the "sid" attribute of the
   /// <encrypted /> element.
+  /// [timestamp] refers to the time the message was sent. This might be either what the
+  /// server tells you via "XEP-0203: Delayed Delivery" or the point in time at which
+  /// you received the stanza, if no Delayed Delivery element was found.
   ///
   /// If the received message is an empty OMEMO message, i.e. there is no <payload />
   /// element, then [ciphertext] must be set to null. In this case, this function
   /// will return null as there is no message to be decrypted. This, however, is used
   /// to set up sessions or advance the ratchets.
-  Future<String?> decryptMessage(List<int>? ciphertext, String senderJid, int senderDeviceId, List<EncryptedKey> keys) async {
+  Future<String?> decryptMessage(List<int>? ciphertext, String senderJid, int senderDeviceId, List<EncryptedKey> keys, int timestamp) async {
     // Try to find a session we can decrypt with.
     var device = await getDevice();
     final rawKey = keys.firstWhereOrNull((key) => key.rid == device.id);
@@ -298,20 +390,57 @@ class OmemoSessionManager {
       throw NotEncryptedForDeviceException();
     }
 
+    final ratchetKey = RatchetMapKey(senderJid, senderDeviceId);
     final decodedRawKey = base64.decode(rawKey.value);
+    List<int>? keyAndHmac;
     OmemoAuthenticatedMessage authMessage;
+    OmemoDoubleRatchet? oldRatchet;
+    OmemoMessage? message;
     if (rawKey.kex) {
-      // TODO(PapaTutuWawa): Only do this when we should
+      // If the ratchet already existed, we store it. If it didn't, oldRatchet will stay
+      // null.
+      final oldRatchet = (await _getRatchet(ratchetKey))?.clone();
       final kex = OmemoKeyExchange.fromBuffer(decodedRawKey);
-      await _addSessionFromKeyExchange(
-        senderJid,
-        senderDeviceId,
-        kex,
-      );
-
       authMessage = kex.message!;
+      message = OmemoMessage.fromBuffer(authMessage.message!);
+
+      // Guard against old key exchanges
+      if (oldRatchet != null) {
+        _log.finest('KEX for existent ratchet. ${oldRatchet.pn}');
+        if (oldRatchet.kexTimestamp > timestamp) {
+          throw InvalidKeyExchangeException();
+        }
+        
+        // Try to decrypt it
+        try {
+          final decrypted = await oldRatchet.ratchetDecrypt(message, authMessage.writeToBuffer());
+
+          // Commit the ratchet
+          _eventStreamController.add(
+            RatchetModifiedEvent(
+              senderJid,
+              senderDeviceId,
+              oldRatchet,
+            ),
+          );
+          
+          final plaintext = await _decryptAndVerifyHmac(
+            ciphertext,
+            decrypted,
+          );
+          await _addSession(senderJid, senderDeviceId, oldRatchet);
+          return plaintext;
+        } catch (_) {
+          _log.finest('Failed to use old ratchet with KEX for existing ratchet');
+        }
+      }
+
+      final r = await _addSessionFromKeyExchange(senderJid, senderDeviceId, kex);
+      await _trustManager.onNewSession(senderJid, senderDeviceId);
+      await _addSession(senderJid, senderDeviceId, r);
 
       // Replace the OPK
+      // TODO(PapaTutuWawa): Replace the OPK when we know that the KEX worked
       await _deviceLock.synchronized(() async {
         device = await device.replaceOnetimePrekey(kex.pkId!);
 
@@ -320,6 +449,7 @@ class OmemoSessionManager {
       });
     } else {
       authMessage = OmemoAuthenticatedMessage.fromBuffer(decodedRawKey);
+      message = OmemoMessage.fromBuffer(authMessage.message!);
     }
     
     final devices = _deviceMap[senderJid];
@@ -330,37 +460,30 @@ class OmemoSessionManager {
       throw NoDecryptionKeyException();
     }
 
-    final message = OmemoMessage.fromBuffer(authMessage.message!);
+    // We can guarantee that the ratchet exists at this point in time
-    final ratchetKey = RatchetMapKey(senderJid, senderDeviceId);
+    final ratchet = (await _getRatchet(ratchetKey))!;
-    List<int>? keyAndHmac;
+    oldRatchet ??= ratchet.clone();
-    await _lock.synchronized(() async {
+
-      final ratchet = _ratchetMap[ratchetKey]!;
+    try {
       if (rawKey.kex) {
         keyAndHmac = await ratchet.ratchetDecrypt(message, authMessage.writeToBuffer());
       } else {
         keyAndHmac = await ratchet.ratchetDecrypt(message, decodedRawKey);
       }
-
+    } catch (_) {
-      // Commit the ratchet
+      await _restoreRatchet(ratchetKey, oldRatchet);
-      _eventStreamController.add(RatchetModifiedEvent(senderJid, senderDeviceId, ratchet));
+      rethrow;
-    });
-
-    // Empty OMEMO messages should just have the key decrypted and/or session set up.
-    if (ciphertext == null) {
-      return null;
     }
 
-    final key = keyAndHmac!.sublist(0, 32);
+    // Commit the ratchet
-    final hmac = keyAndHmac!.sublist(32, 48);
+    _eventStreamController.add(RatchetModifiedEvent(senderJid, senderDeviceId, ratchet));
-    final derivedKeys = await deriveEncryptionKeys(key, omemoPayloadInfoString);
 
-    final computedHmac = await truncatedHmac(ciphertext, derivedKeys.authenticationKey);
+    try {
-    if (!listsEqual(hmac, computedHmac)) {
+      return _decryptAndVerifyHmac(ciphertext, keyAndHmac);
-      throw InvalidMessageHMACException();
+    } catch (_) { 
+      await _restoreRatchet(ratchetKey, oldRatchet);
+      rethrow;
     }
-    
-    final plaintext = await aes256CbcDecrypt(ciphertext, derivedKeys.encryptionKey, derivedKeys.iv);
-    return utf8.decode(plaintext);
   }
 
   /// Returns the list of hex-encoded fingerprints we have for sessions with [jid].
@@ -369,7 +492,7 @@ class OmemoSessionManager {
 
     await _lock.synchronized(() async {
       // Get devices for jid
-      final devices = _deviceMap[jid]!;
+      final devices = _deviceMap[jid] ?? [];
 
       for (final deviceId in devices) {
         final ratchet = _ratchetMap[RatchetMapKey(jid, deviceId)]!;
@@ -386,6 +509,16 @@ class OmemoSessionManager {
     return fingerprints;
   }
 
+  /// Returns the hex-encoded fingerprint of the current device.
+  Future<DeviceFingerprint> getHexFingerprintForDevice() async {
+    final device = await getDevice();
+
+    return DeviceFingerprint(
+      device.id,
+      HEX.encode(await device.ik.pk.getBytes()),
+    );
+  }
+
   /// Replaces the Signed Prekey and its signature in our own device bundle. Triggers
   /// a DeviceModifiedEvent when done.
   /// See https://xmpp.org/extensions/xep-0384.html#protocol-key_exchange under the point
@@ -402,13 +535,7 @@ class OmemoSessionManager {
   /// Returns the device map, i.e. the mapping of bare Jid to its device identifiers
   /// we have built sessions with.
   Future<Map<String, List<int>>> getDeviceMap() async {
-    Map<String, List<int>>? map;
+    return _lock.synchronized(() => _deviceMap);
-
-    await _lock.synchronized(() async {
-      map = _deviceMap;
-    });
-
-    return map!;
   }
 
   /// Removes the ratchet identified by [jid] and [deviceId] from the session manager.
@@ -431,20 +558,45 @@ class OmemoSessionManager {
     });
   }
 
+  /// Removes all ratchets for Jid [jid]. Triggers a DeviceMapModified event at the end and an
+  /// RatchetRemovedEvent for each ratchet.
+  Future<void> removeAllRatchets(String jid) async {
+    await _lock.synchronized(() async {
+      for (final deviceId in _deviceMap[jid]!) {
+        // Remove the ratchet
+        _ratchetMap.remove(RatchetMapKey(jid, deviceId));
+        // Commit it
+        _eventStreamController.add(RatchetRemovedEvent(jid, deviceId));
+      }
+
+      // Remove the device from jid
+      _deviceMap.remove(jid);
+      // Commit it
+      _eventStreamController.add(DeviceMapModifiedEvent(_deviceMap));
+    });
+  }
+  
   /// Returns the list of device identifiers belonging to [jid] that are yet unacked, i.e.
   /// we have not yet received an empty OMEMO message from.
-  Future<List<int>> getUnacknowledgedRatchets(String jid) async {
+  Future<List<int>?> getUnacknowledgedRatchets(String jid) async {
-    final ret = List<int>.empty(growable: true);
+    return _lock.synchronized(() async {
+      final ret = List<int>.empty(growable: true);
+      final devices = _deviceMap[jid];
+      if (devices == null) return null;
 
-    await _lock.synchronized(() async {
-      final devices = _deviceMap[jid]!;
       for (final device in devices) {
         final ratchet = _ratchetMap[RatchetMapKey(jid, device)]!;
         if (!ratchet.acknowledged) ret.add(device);
       }
-    });
 
-    return ret;
+      return ret;
+    });
+  }
+
+  /// Returns true if the ratchet for [jid] with device identifier [deviceId] is
+  /// acknowledged. Returns false if not.
+  Future<bool> isRatchetAcknowledged(String jid, int deviceId) async {
+    return _lock.synchronized(() => _ratchetMap[RatchetMapKey(jid, deviceId)]!.acknowledged);
   }
   
   /// Mark the ratchet for device [deviceId] from [jid] as acked.
@@ -480,48 +632,18 @@ class OmemoSessionManager {
     });
   }
 
+  Future<OmemoDoubleRatchet?> _getRatchet(RatchetMapKey key) async {
+    return _lock.synchronized(() async {
+      return _ratchetMap[key];
+    });
+  }
+  
   @visibleForTesting
   OmemoDoubleRatchet getRatchet(String jid, int deviceId) => _ratchetMap[RatchetMapKey(jid, deviceId)]!;
 
   @visibleForTesting
   Map<RatchetMapKey, OmemoDoubleRatchet> getRatchetMap() => _ratchetMap;
 
-  /// Serialise the entire session manager into a JSON object.
-  Future<Map<String, dynamic>> toJson() async {
-    /*
-    {
-      'devices': {
-        'alice@...': [1, 2, ...],
-        'bob@...': [1],
-        ...
-      },
-      'device': { ... },
-      'sessions': [
-        {
-          'jid': 'alice@...',
-          'deviceId': 1,
-          'ratchet': { ... },
-        },
-        ...
-      ],
-    }
-    */
-
-    final sessions = List<Map<String, dynamic>>.empty(growable: true);
-    for (final entry in _ratchetMap.entries) {
-      sessions.add({
-        'jid': entry.key.jid,
-        'deviceId': entry.key.deviceId,
-        'ratchet': await entry.value.toJson(),
-      });
-    }
-    return {
-      'devices': _deviceMap,
-      'device': await (await getDevice()).toJson(),
-      'sessions': sessions,
-    };
-  }
-
   /// Serialise the entire session manager into a JSON object.
   Future<Map<String, dynamic>> toJsonWithoutSessions() async {
     /*

lib/src/protobuf/protobuf.dart

@@ -46,21 +46,18 @@ List<int> encodeVarint(int i) {
   assert(i >= 0, "Two's complement is not implemented");
   final ret = List<int>.empty(growable: true);
 
-  var j = 0;
+  // Thanks to https://github.com/hathibelagal-dev/LEB128 for the trick with toRadixString!
-  while (true) {
+  final numSevenBlocks = (i.toRadixString(2).length / 7).ceil();
+  for (var j = 0; j < numSevenBlocks; j++) {
     // The 7 LSB of the byte we're creating
     final x = (i & (lsb7Mask << j * 7)) >> j * 7;
-    // The next bits
-    final next = i & (lsb7Mask << (j + 1) * 7);
 
-    if (next == 0) {
+    if (j == numSevenBlocks - 1) {
       // If we were to shift further, we only get zero, so we're at the end
       ret.add(x);
-      break;
     } else {
       // We still have at least one bit more to go, so set the MSB to 1
       ret.add(x + msb);
-      j++;
     }
   }
 

lib/src/trust/always.dart

@@ -11,4 +11,13 @@ class AlwaysTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> onNewSession(String jid, int deviceId) async {}
+
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async => true;
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

lib/src/trust/base.dart

@@ -8,4 +8,15 @@ abstract class TrustManager {
   /// Called by the OmemoSessionManager when a new session has been built. Should set
   /// a default trust state to [jid]'s device with identifier [deviceId].
   Future<void> onNewSession(String jid, int deviceId);
+
+  /// Return true if the device with id [deviceId] of Jid [jid] should be used for encryption.
+  /// If not, return false.
+  Future<bool> isEnabled(String jid, int deviceId);
+
+  /// Mark the device with id [deviceId] of Jid [jid] as enabled if [enabled] is true or as disabled
+  /// if [enabled] is false.
+  Future<void> setEnabled(String jid, int deviceId, bool enabled);
+
+  /// Serialize the trust manager to JSON.
+  Future<Map<String, dynamic>> toJson();
 }

lib/src/trust/btbv.dart

@@ -8,24 +8,52 @@ import 'package:synchronized/synchronized.dart';
 /// - blindTrust: The fingerprint is not verified using OOB means
 /// - verified: The fingerprint has been verified using OOB means
 enum BTBVTrustState {
-  notTrusted,
+  notTrusted, // = 1
-  blindTrust,
+  blindTrust, // = 2
-  verified,
+  verified,   // = 3
+}
+
+int _trustToInt(BTBVTrustState state) {
+  switch (state) {
+    case BTBVTrustState.notTrusted: return 1;
+    case BTBVTrustState.blindTrust: return 2;
+    case BTBVTrustState.verified:   return 3;
+  }
+}
+
+BTBVTrustState _trustFromInt(int i) {
+  switch (i) {
+    case 1: return BTBVTrustState.notTrusted;
+    case 2: return BTBVTrustState.blindTrust;
+    case 3: return BTBVTrustState.verified;
+    default: return BTBVTrustState.notTrusted;
+  }
 }
 
 /// A TrustManager that implements the idea of Blind Trust Before Verification.
 /// See https://gultsch.de/trust.html for more details.
 abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
-  BlindTrustBeforeVerificationTrustManager()
+  BlindTrustBeforeVerificationTrustManager({
-    : trustCache = {},
+    Map<RatchetMapKey, BTBVTrustState>? trustCache,
-      devices = {},
+    Map<RatchetMapKey, bool>? enablementCache,
-      _lock = Lock();
+    Map<String, List<int>>? devices,
+  }) : trustCache = trustCache ?? {},
+       enablementCache = enablementCache ?? {},
+       devices = devices ?? {},
+       _lock = Lock();
 
-  /// The cache for Mapping a RatchetMapKey to its trust state
+  /// The cache for mapping a RatchetMapKey to its trust state
+  @visibleForTesting
   @protected
   final Map<RatchetMapKey, BTBVTrustState> trustCache;
 
+  /// The cache for mapping a RatchetMapKey to whether it is enabled or not
+  @visibleForTesting
+  @protected
+  final Map<RatchetMapKey, bool> enablementCache;
+  
   /// Mapping of Jids to their device identifiers
+  @visibleForTesting
   @protected
   final Map<String, List<int>> devices;
 
@@ -74,10 +102,13 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
   @override
   Future<void> onNewSession(String jid, int deviceId) async {
     await _lock.synchronized(() async {
+      final key = RatchetMapKey(jid, deviceId);
       if (_hasAtLeastOneVerifiedDevice(jid)) {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.notTrusted;
+        trustCache[key] = BTBVTrustState.notTrusted;
+        enablementCache[key] = false;
       } else {
-        trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.blindTrust;
+        trustCache[key] = BTBVTrustState.blindTrust;
+        enablementCache[key] = true;
       }
 
       if (devices.containsKey(jid)) {
@@ -114,16 +145,75 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
     });
   }
 
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async {
+    return _lock.synchronized(() async {
+      final value = enablementCache[RatchetMapKey(jid, deviceId)];
+
+      if (value == null) return false;
+      return value;
+    });
+  }
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {
+    await _lock.synchronized(() async {
+      enablementCache[RatchetMapKey(jid, deviceId)] = enabled;
+    });
+
+    // Commit the state
+    await commitState();
+  }
+
+  @override
+  Future<Map<String, dynamic>> toJson() async {
+    return {
+      'devices': devices,
+      'trust': trustCache.map((key, value) => MapEntry(
+        key.toJsonKey(), _trustToInt(value),
+      ),),
+      'enable': enablementCache.map((key, value) => MapEntry(key.toJsonKey(), value)),
+    };
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the device list.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<String, List<int>> deviceListFromJson(Map<String, dynamic> json) {
+    return (json['devices']! as Map<String, dynamic>).map<String, List<int>>(
+      (key, value) => MapEntry(
+        key,
+        (value as List<dynamic>).map<int>((i) => i as int).toList(),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the trust cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, BTBVTrustState> trustCacheFromJson(Map<String, dynamic> json) {
+    return (json['trust']! as Map<String, dynamic>).map<RatchetMapKey, BTBVTrustState>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        _trustFromInt(value as int),
+      ),
+    );
+  }
+
+  /// From a serialized version of a BTBV trust manager, extract the enable cache.
+  /// NOTE: This is needed as Dart cannot just cast a List<dynamic> to List<int> and so on.
+  static Map<RatchetMapKey, bool> enableCacheFromJson(Map<String, dynamic> json) {
+    return (json['enable']! as Map<String, dynamic>).map<RatchetMapKey, bool>(
+      (key, value) => MapEntry(
+        RatchetMapKey.fromJsonKey(key),
+        value as bool,
+      ),
+    );
+  }
+  
   /// Called when the state of the trust manager has been changed. Allows the user to
   /// commit the trust state to persistent storage.
   @visibleForOverriding
   Future<void> commitState();
 
-  /// Called when the user wants to restore the state of the trust manager. The format
-  /// and actual storage mechanism is left to the user.
-  @visibleForOverriding
-  Future<void> loadState();
-  
   @visibleForTesting
   BTBVTrustState getDeviceTrust(String jid, int deviceId) => trustCache[RatchetMapKey(jid, deviceId)]!;
 }
@@ -133,7 +223,4 @@ abstract class BlindTrustBeforeVerificationTrustManager extends TrustManager {
 class MemoryBTBVTrustManager extends BlindTrustBeforeVerificationTrustManager {
   @override
   Future<void> commitState() async {}
-
-  @override
-  Future<void> loadState() async {}
 }

lib/src/trust/never.dart

@@ -11,4 +11,13 @@ class NeverTrustingTrustManager extends TrustManager {
 
   @override
   Future<void> onNewSession(String jid, int deviceId) async {}
+
+  @override
+  Future<bool> isEnabled(String jid, int deviceId) async => true;
+
+  @override
+  Future<void> setEnabled(String jid, int deviceId, bool enabled) async {}
+
+  @override
+  Future<Map<String, dynamic>> toJson() async => <String, dynamic>{};
 }

pubspec.yaml

@@ -1,6 +1,6 @@
 name: omemo_dart
 description: An XMPP library independent OMEMO library
-version: 0.1.3
+version: 0.3.2
 homepage: https://github.com/PapaTutuWawa/omemo_dart
 publish_to: https://git.polynom.me/api/packages/PapaTutuWawa/pub
 
@@ -11,7 +11,8 @@ dependencies:
   collection: ^1.16.0
   cryptography: ^2.0.5
   hex: ^0.2.0
-  meta: ^1.8.0
+  logging: ^1.0.2
+  meta: ^1.7.0
   pinenacl: ^0.5.1
   synchronized: ^3.0.0+2
 

test/double_ratchet_test.dart

@@ -84,12 +84,14 @@ void main() {
       ikBob.pk,
       resultAlice.sk,
       resultAlice.ad,
+      0,
     );
     final bobsRatchet = await OmemoDoubleRatchet.acceptNewSession(
       spkBob,
       ikAlice.pk,
       resultBob.sk,
       resultBob.ad,
+      0,
     );
 
     expect(alicesRatchet.sessionAd, bobsRatchet.sessionAd);

test/omemo_test.dart

@@ -1,9 +1,47 @@
+import 'package:logging/logging.dart';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:omemo_dart/src/trust/never.dart';
 import 'package:test/test.dart';
 
 void main() {
+  Logger.root
+    ..level = Level.ALL
+    ..onRecord.listen((record) {
+      // ignore: avoid_print
+      print('${record.level.name}: ${record.message}');
+    });
+
+  test('Test replacing a onetime prekey', () async {
+    const aliceJid = 'alice@server.example';
+    final device = await Device.generateNewDevice(aliceJid, opkAmount: 1);
+
+    final newDevice = await device.replaceOnetimePrekey(0);
+
+    expect(device.jid, newDevice.jid);
+    expect(device.id, newDevice.id);
+
+    var opksMatch = true;
+    if (newDevice.opks.length != device.opks.length) {
+      opksMatch = false;
+    } else {
+      for (final entry in device.opks.entries) {
+        final m = await newDevice.opks[entry.key]?.equals(entry.value) ?? false;
+        if (!m) opksMatch = false;
+      }
+    }
+    
+    expect(opksMatch, true);
+    expect(await device.ik.equals(newDevice.ik), true);
+    expect(await device.spk.equals(newDevice.spk), true);
+
+    final oldSpkMatch = device.oldSpk != null ?
+      await device.oldSpk!.equals(newDevice.oldSpk!) :
+      newDevice.oldSpk == null;
+    expect(oldSpkMatch, true);
+    expect(listsEqual(device.spkSignature, newDevice.spkSignature), true);
+  });
+    
   test('Test using OMEMO sessions with only one device per user', () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
@@ -38,7 +76,7 @@ void main() {
       bobJid,
       messagePlaintext,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
     expect(aliceMessage.encryptedKeys.length, 1);
@@ -50,8 +88,9 @@ void main() {
     final bobMessage = await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
     // The ratchet should be modified two times: Once for when the ratchet is created and
@@ -67,6 +106,10 @@ void main() {
       false,
     );
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(aliceJid, await aliceSession.getDeviceId());
+    
     // Bob responds to Alice
     const bobResponseText = 'Oh, hello Alice!';
     final bobResponseMessage = await bobSession.encryptToJid(
@@ -81,8 +124,9 @@ void main() {
     final aliceReceivedMessage = await aliceSession.decryptMessage(
       bobResponseMessage.ciphertext,
       bobJid,
-      (await bobSession.getDevice()).id,
+      await bobSession.getDeviceId(),
       bobResponseMessage.encryptedKeys,
+      0,
     );
     expect(bobResponseText, aliceReceivedMessage);
   });
@@ -115,8 +159,8 @@ void main() {
       bobJid,
       messagePlaintext,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
-        await (await bobSession2.getDevice()).toBundle(),
+        await bobSession2.getDeviceBundle(),
       ],
     );
     expect(aliceMessage.encryptedKeys.length, 2);
@@ -130,11 +174,16 @@ void main() {
     final bobMessage = await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(aliceJid, await aliceSession.getDeviceId());
+    
     // Bob responds to Alice
     const bobResponseText = 'Oh, hello Alice!';
     final bobResponseMessage = await bobSession.encryptToJid(
@@ -149,8 +198,9 @@ void main() {
     final aliceReceivedMessage = await aliceSession.decryptMessage(
       bobResponseMessage.ciphertext,
       bobJid,
-      (await bobSession.getDevice()).id,
+      await bobSession.getDeviceId(),
       bobResponseMessage.encryptedKeys,
+      0,
     );
     expect(bobResponseText, aliceReceivedMessage);
 
@@ -192,8 +242,8 @@ void main() {
       [bobJid, aliceJid],
       messagePlaintext,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
-        await (await aliceSession2.getDevice()).toBundle(),
+        await aliceSession2.getDeviceBundle(),
       ],
     );
     expect(aliceMessage.encryptedKeys.length, 2);
@@ -205,8 +255,9 @@ void main() {
     final bobMessage = await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession1.getDevice()).id,
+      await aliceSession1.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
 
@@ -214,13 +265,14 @@ void main() {
     final aliceMessage2 = await aliceSession2.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession1.getDevice()).id,
+      await aliceSession1.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, aliceMessage2);
   });
 
-  test('Test using sending empty OMEMO messages', () async {
+  test('Test sending empty OMEMO messages', () async {
     const aliceJid = 'alice@server.example';
     const bobJid = 'bob@other.server.example';
       
@@ -241,7 +293,7 @@ void main() {
       bobJid,
       null,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
     expect(aliceMessage.encryptedKeys.length, 1);
@@ -254,13 +306,14 @@ void main() {
     final bobMessage = await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(bobMessage, null);
 
     // This call must not cause an exception
-    bobSession.getRatchet(aliceJid, (await aliceSession.getDevice()).id);
+    bobSession.getRatchet(aliceJid, await aliceSession.getDeviceId());
   });
 
   test('Test rotating the Signed Prekey', () async {
@@ -316,7 +369,7 @@ void main() {
       bobJid,
       messagePlaintext,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
     expect(aliceMessage.encryptedKeys.length, 1);
@@ -331,8 +384,9 @@ void main() {
     final bobMessage = await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
     expect(messagePlaintext, bobMessage);
   });
@@ -358,7 +412,7 @@ void main() {
       bobJid,
       null,
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
 
@@ -387,7 +441,7 @@ void main() {
       bobJid,
       'Hello Bob!',
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
 
@@ -397,10 +451,15 @@ void main() {
     await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      0,
     );
 
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(aliceJid, await aliceSession.getDeviceId());
+    
     for (var i = 0; i < 100; i++) {
       final messageText = 'Test Message #$i';
       // Bob responds to Alice
@@ -416,8 +475,9 @@ void main() {
       final aliceReceivedMessage = await aliceSession.decryptMessage(
         bobResponseMessage.ciphertext,
         bobJid,
-        (await bobSession.getDevice()).id,
+        await bobSession.getDeviceId(),
         bobResponseMessage.encryptedKeys,
+        0,
       );
       expect(messageText, aliceReceivedMessage);
     }
@@ -448,14 +508,14 @@ void main() {
         bobJid,
         'Hallo Welt',
         newSessions: [
-          await (await bobSession1.getDevice()).toBundle(),
+          await bobSession1.getDeviceBundle(),
-          await (await bobSession2.getDevice()).toBundle(),
+          await bobSession2.getDeviceBundle(),
         ],
       );
 
       // One of those two sessions is broken, so Alice removes the session2 ratchet
-      final id1 = (await bobSession1.getDevice()).id;
+      final id1 = await bobSession1.getDeviceId();
-      final id2 = (await bobSession2.getDevice()).id;
+      final id2 = await bobSession2.getDeviceId();
       await aliceSession.removeRatchet(bobJid, id1);
 
       final map = aliceSession.getRatchetMap();
@@ -485,12 +545,12 @@ void main() {
         bobJid,
         'Hallo Welt',
         newSessions: [
-          await (await bobSession.getDevice()).toBundle(),
+          await bobSession.getDeviceBundle(),
         ],
       );
 
       // One of those two sessions is broken, so Alice removes the session2 ratchet
-      final id = (await bobSession.getDevice()).id;
+      final id = await bobSession.getDeviceId();
       await aliceSession.removeRatchet(bobJid, id);
 
       final map = aliceSession.getRatchetMap();
@@ -520,13 +580,13 @@ void main() {
       bobJid,
       'Hallo Welt',
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
     expect(
       await aliceSession.getUnacknowledgedRatchets(bobJid),
       [
-        (await bobSession.getDevice()).id,
+        await bobSession.getDeviceId(),
       ],
     );
 
@@ -537,10 +597,350 @@ void main() {
     // ...
 
     // Alice marks the ratchet as acknowledged
-    await aliceSession.ratchetAcknowledged(bobJid, (await bobSession.getDevice()).id);
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
     expect(
-      (await aliceSession.getUnacknowledgedRatchets(bobJid)).isEmpty,
+      (await aliceSession.getUnacknowledgedRatchets(bobJid))!.isEmpty,
       true,
     );
   });
+
+  test('Test overwriting sessions', () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 2,
+    );
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      0,
+    );
+    final aliceRatchet1 = aliceSession.getRatchet(
+      bobJid,
+      await bobSession.getDeviceId(),
+    );
+    final bobRatchet1 = bobSession.getRatchet(
+      aliceJid,
+      await aliceSession.getDeviceId(),
+    );
+
+    // Alice is impatient and immediately sends another message before the original one
+    // can be acknowledged by Bob
+    final msg2 = await aliceSession.encryptToJid(
+      bobJid,
+      "Why don't you answer?",
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    await bobSession.decryptMessage(
+      msg2.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+    final aliceRatchet2 = aliceSession.getRatchet(
+      bobJid,
+      await bobSession.getDeviceId(),
+    );
+    final bobRatchet2 = bobSession.getRatchet(
+      aliceJid,
+      await aliceSession.getDeviceId(),
+    );
+
+    // Both should only have one ratchet
+    expect(aliceSession.getRatchetMap().length, 1);
+    expect(bobSession.getRatchetMap().length, 1);
+    
+    // The ratchets should both be different
+    expect(await aliceRatchet1.equals(aliceRatchet2), false);
+    expect(await bobRatchet1.equals(bobRatchet2), false);
+  });
+
+  test('Test resending key exchanges', () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 2,
+    );
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    // The first message should be a kex message
+    expect(msg1.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      0,
+    );
+
+    // Alice is impatient and immediately sends another message before the original one
+    // can be acknowledged by Bob
+    final msg2 = await aliceSession.encryptToJid(
+      bobJid,
+      "Why don't you answer?",
+    );
+    expect(msg2.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg2.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+
+  });
+  
+  test('Test receiving old messages including a KEX', () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 2,
+    );
+
+    final bobsReceivedMessages = List<EncryptionResult>.empty(growable: true);
+    final bobsReceivedMessagesTimestamps = List<int>.empty(growable: true);
+    
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    bobsReceivedMessages.add(msg1);
+    final t1 = getTimestamp();
+    bobsReceivedMessagesTimestamps.add(t1);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      t1,
+    );
+
+    // Ratchets are acked
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(aliceJid, await aliceSession.getDeviceId());
+    
+    // Bob responds
+    final msg2 = await bobSession.encryptToJid(
+      aliceJid,
+      'Hello!',
+    );
+
+    await aliceSession.decryptMessage(
+      msg2.ciphertext,
+      bobJid,
+      await bobSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+    
+    // Send some messages between the two
+    for (var i = 0; i < 100; i++) {
+      final msg = await aliceSession.encryptToJid(
+        bobJid,
+        'Hello $i',
+      );
+      bobsReceivedMessages.add(msg);
+      final t = getTimestamp();
+      bobsReceivedMessagesTimestamps.add(t);
+      final result = await bobSession.decryptMessage(
+        msg.ciphertext,
+        aliceJid,
+        await aliceSession.getDeviceId(),
+        msg.encryptedKeys,
+        t,
+      );
+
+      expect(result, 'Hello $i');
+    }
+
+    // Due to some issue with the transport protocol, the messages to Bob are received
+    // again.
+    final ratchetPreError = bobSession
+      .getRatchet(aliceJid, await aliceSession.getDeviceId())
+      .clone();
+    var invalidKex = 0;
+    var errorCounter = 0;
+    for (var i = 0; i < bobsReceivedMessages.length; i++) {
+      final msg = bobsReceivedMessages[i];
+      try {
+        await bobSession.decryptMessage(
+          msg.ciphertext,
+          aliceJid,
+          await aliceSession.getDeviceId(),
+          msg.encryptedKeys,
+          bobsReceivedMessagesTimestamps[i],
+        );
+        expect(true, false);
+      } on InvalidMessageHMACException catch (_) {
+        errorCounter++;
+      } on InvalidKeyExchangeException catch (_) {
+        invalidKex++;
+      }
+    }
+    final ratchetPostError = bobSession
+      .getRatchet(aliceJid, await aliceSession.getDeviceId())
+      .clone();
+
+    // The 100 messages including the initial KEX message
+    expect(invalidKex, 1);
+    expect(errorCounter, 100);
+    expect(await ratchetPreError.equals(ratchetPostError), true);
+
+    
+    final msg3 = await aliceSession.encryptToJid(
+      bobJid,
+      'Are you okay?',
+    );
+    final result = await bobSession.decryptMessage(
+      msg3.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg3.encryptedKeys,
+      104,
+    );
+
+    expect(result, 'Are you okay?');
+  });
+
+  test("Test ignoring a new KEX when we haven't acket it yet", () async {
+    const aliceJid = 'alice@server.example';
+    const bobJid = 'bob@other.server.example';
+    // Alice and Bob generate their sessions
+    final aliceSession = await OmemoSessionManager.generateNewIdentity(
+      aliceJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+    final bobSession = await OmemoSessionManager.generateNewIdentity(
+      bobJid,
+      AlwaysTrustingTrustManager(),
+      opkAmount: 1,
+    );
+
+    // Alice sends Bob a message
+    final msg1 = await aliceSession.encryptToJid(
+      bobJid,
+      'Hallo Welt',
+      newSessions: [
+        await bobSession.getDeviceBundle(),
+      ],
+    );
+    expect(msg1.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg1.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg1.encryptedKeys,
+      getTimestamp(),
+    );
+
+    // Alice sends another message before the ack can reach us
+    final msg2 = await aliceSession.encryptToJid(
+      bobJid,
+      'ANSWER ME!',
+    );
+    expect(msg2.encryptedKeys.first.kex, true);
+
+    await bobSession.decryptMessage(
+      msg2.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg2.encryptedKeys,
+      getTimestamp(),
+    );
+
+    // Now the acks reach us
+    await aliceSession.ratchetAcknowledged(bobJid, await bobSession.getDeviceId());
+    await bobSession.ratchetAcknowledged(aliceJid, await aliceSession.getDeviceId());
+
+    // Alice sends another message
+    final msg3 = await aliceSession.encryptToJid(
+      bobJid,
+      "You read the message, didn't you?",
+    );
+    expect(msg3.encryptedKeys.first.kex, false);
+
+    await bobSession.decryptMessage(
+      msg3.ciphertext,
+      aliceJid,
+      await aliceSession.getDeviceId(),
+      msg3.encryptedKeys,
+      getTimestamp(),
+    );
+
+    for (var i = 0; i < 100; i++) {
+      final messageText = 'Test Message #$i';
+      // Bob responds to Alice
+      final bobResponseMessage = await bobSession.encryptToJid(
+        aliceJid,
+        messageText,
+      );
+
+      // Bob sends the message to Alice
+      // ...
+
+      // Alice decrypts it
+      final aliceReceivedMessage = await aliceSession.decryptMessage(
+        bobResponseMessage.ciphertext,
+        bobJid,
+        await bobSession.getDeviceId(),
+        bobResponseMessage.encryptedKeys,
+        0,
+      );
+      expect(messageText, aliceReceivedMessage);
+    }
+  });
 }

test/protobuf_test.dart

@@ -48,6 +48,10 @@ void main() {
         <int>[172, 2],
       );
     });
+
+    test('Test some special cases', () {
+      expect(decodeVarint(encodeVarint(1042464893), 0).n, 1042464893);
+    });
   });
 
   group('OMEMOMessage', () {
@@ -170,5 +174,13 @@ void main() {
       expect(decoded.message!.mac, <int>[5, 6, 8, 0]);
       expect(decoded.message!.message, <int>[4, 5, 7, 3, 2]);
     });
+    test('Test decoding an issue', () {
+      /*
+      final data = 'CAAQfRogc2GwslU219dUkrMHNM4KdZRmuFnBTae+bQaJ+55IsAMiII7aZKj2sUpb6xR/3Ari7WZUmKFV0G6czUc4NMvjKDBaKnwKEM2ZpI8X3TgcxhxwENANnlsSaAgAEAAaICy8T9WPgLb7RdYd8/4JkrLF0RahEkC3ZaEfk5jw3dsLIkBMILzLyByweLgF4lCn0oNea+kbdrFr6rY7r/7WyI8hXEQz38QpnN+jyGGwC7Ga0dq70WuyqE7VpiFArQwqZh2G';
+      final kex = OmemoKeyExchange.fromBuffer(base64Decode(data));
+
+      expect(kex.spkId!, 1042464893);
+      */
+    });
   });
 }

test/serialisation_test.dart

@@ -1,7 +1,12 @@
+import 'dart:convert';
 import 'package:omemo_dart/omemo_dart.dart';
 import 'package:omemo_dart/src/trust/always.dart';
 import 'package:test/test.dart';
 
+Map<String, dynamic> jsonify(Map<String, dynamic> map) {
+  return jsonDecode(jsonEncode(map)) as Map<String, dynamic>;
+}
+
 void main() {
   test('Test serialising and deserialising the Device', () async {
     // Generate a random session
@@ -11,7 +16,7 @@ void main() {
       opkAmount: 1,
     );
     final oldDevice = await oldSession.getDevice();
-    final serialised = await oldDevice.toJson();
+    final serialised = jsonify(await oldDevice.toJson());
 
     final newDevice = Device.fromJson(serialised);
     expect(await oldDevice.equals(newDevice), true);
@@ -25,7 +30,7 @@ void main() {
       opkAmount: 1,
     );
     final oldDevice = await (await oldSession.getDevice()).replaceSignedPrekey();
-    final serialised = await oldDevice.toJson();
+    final serialised = jsonify(await oldDevice.toJson());
 
     final newDevice = Device.fromJson(serialised);
     expect(await oldDevice.equals(newDevice), true);
@@ -49,17 +54,18 @@ void main() {
       bobJid,
       'Hello Bob!',
       newSessions: [
-        await (await bobSession.getDevice()).toBundle(),
+        await bobSession.getDeviceBundle(),
       ],
     );
     await bobSession.decryptMessage(
       aliceMessage.ciphertext,
       aliceJid,
-      (await aliceSession.getDevice()).id,
+      await aliceSession.getDeviceId(),
       aliceMessage.encryptedKeys,
+      getTimestamp(),
     );
-    final aliceOld = aliceSession.getRatchet(bobJid, (await bobSession.getDevice()).id);
+    final aliceOld = aliceSession.getRatchet(bobJid, await bobSession.getDeviceId());
-    final aliceSerialised = await aliceOld.toJson();
+    final aliceSerialised = jsonify(await aliceOld.toJson());
     final aliceNew = OmemoDoubleRatchet.fromJson(aliceSerialised);
 
     expect(await aliceOld.equals(aliceNew), true);
@@ -79,14 +85,16 @@ void main() {
     );
     await oldSession.addSessionFromBundle(
       'bob@localhost',
-      (await bobSession.getDevice()).id,
+      await bobSession.getDeviceId(),
-      await (await bobSession.getDevice()).toBundle(),
+      await bobSession.getDeviceBundle(),
     );
 
     // Serialise and deserialise
-    final serialised = await oldSession.toJson();
+    final serialised = jsonify(await oldSession.toJsonWithoutSessions());
-    final newSession = OmemoSessionManager.fromJson(
+    final newSession = OmemoSessionManager.fromJsonWithoutSessions(
       serialised,
+      // NOTE: At this point, we don't care about this attribute
+      {},
       AlwaysTrustingTrustManager(),
     );
 
@@ -94,14 +102,47 @@ void main() {
     final newDevice = await newSession.getDevice();
     expect(await oldDevice.equals(newDevice), true);
     expect(await oldSession.getDeviceMap(), await newSession.getDeviceMap());
+  });
 
-    expect(oldSession.getRatchetMap().length, newSession.getRatchetMap().length);
+  test('Test serializing and deserializing RatchetMapKey', () {
-    for (final session in oldSession.getRatchetMap().entries) {
+    const test1 = RatchetMapKey('user@example.org', 1234);
-      expect(newSession.getRatchetMap().containsKey(session.key), true);
+    final result1 = RatchetMapKey.fromJsonKey(test1.toJsonKey());
+    expect(result1.jid, test1.jid);
+    expect(result1.deviceId, test1.deviceId);
 
-      final oldRatchet = oldSession.getRatchetMap()[session.key]!;
+    const test2 = RatchetMapKey('user@example.org/hallo:welt', 3333);
-      final newRatchet = newSession.getRatchetMap()[session.key]!;
+    final result2 = RatchetMapKey.fromJsonKey(test2.toJsonKey());
-      expect(await oldRatchet.equals(newRatchet), true);
+    expect(result2.jid, test2.jid);
-    }
+    expect(result2.deviceId, test2.deviceId);
+  });
+
+  test('Test serializing and deserializing the components of the BTBV manager', () async {
+    // Caroline's BTBV manager
+    final btbv = MemoryBTBVTrustManager();
+    // Example data
+    const aliceJid = 'alice@some.server';
+    const bobJid = 'bob@other.server';
+    
+    await btbv.onNewSession(aliceJid, 1);
+    await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
+    await btbv.onNewSession(aliceJid, 2);
+    await btbv.onNewSession(bobJid, 3);
+    await btbv.onNewSession(bobJid, 4);
+
+    final serialized = jsonify(await btbv.toJson());
+    final deviceList = BlindTrustBeforeVerificationTrustManager.deviceListFromJson(
+      serialized,
+    );
+    expect(btbv.devices, deviceList);
+
+    final trustCache = BlindTrustBeforeVerificationTrustManager.trustCacheFromJson(
+      serialized,
+    );
+    expect(btbv.trustCache, trustCache);
+
+    final enableCache = BlindTrustBeforeVerificationTrustManager.enableCacheFromJson(
+      serialized,
+    );
+    expect(btbv.enablementCache, enableCache);
   });
 }

test/trust_test.dart

@@ -12,6 +12,7 @@ void main() {
     // Caroline starts a chat a device from Alice
     await btbv.onNewSession(aliceJid, 1);
     expect(await btbv.isTrusted(aliceJid, 1), true);
+    expect(await btbv.isEnabled(aliceJid, 1), true);
 
     // Caroline meets with Alice and verifies her fingerprint
     await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
@@ -21,6 +22,7 @@ void main() {
     await btbv.onNewSession(aliceJid, 2);
     expect(await btbv.isTrusted(aliceJid, 2), false);
     expect(btbv.getDeviceTrust(aliceJid, 2), BTBVTrustState.notTrusted);
+    expect(await btbv.isEnabled(aliceJid, 2), false);
 
     // Caronline starts a chat with Bob but since they live far apart, Caroline cannot
     // verify his fingerprint.
@@ -32,5 +34,7 @@ void main() {
     expect(await btbv.isTrusted(bobJid, 4), true);
     expect(btbv.getDeviceTrust(bobJid, 3), BTBVTrustState.blindTrust);
     expect(btbv.getDeviceTrust(bobJid, 4), BTBVTrustState.blindTrust);
+    expect(await btbv.isEnabled(bobJid, 3), true);
+    expect(await btbv.isEnabled(bobJid, 4), true);
   });
 }