famedlysdk/lib/encryption/key_manager.dart

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/*
* Famedly Matrix SDK
* Copyright (C) 2019, 2020 Famedly GmbH
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
import 'dart:convert';
import 'package:pedantic/pedantic.dart';
import 'package:famedlysdk/famedlysdk.dart';
import 'package:famedlysdk/matrix_api.dart';
import 'package:olm/olm.dart' as olm;
import './encryption.dart';
import './utils/session_key.dart';
import './utils/outbound_group_session.dart';
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const MEGOLM_KEY = 'm.megolm_backup.v1';
class KeyManager {
final Encryption encryption;
Client get client => encryption.client;
final outgoingShareRequests = <String, KeyManagerKeyShareRequest>{};
final incomingShareRequests = <String, KeyManagerKeyShareRequest>{};
final _inboundGroupSessions = <String, Map<String, SessionKey>>{};
final _outboundGroupSessions = <String, OutboundGroupSession>{};
final Set<String> _loadedOutboundGroupSessions = <String>{};
final Set<String> _requestedSessionIds = <String>{};
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KeyManager(this.encryption) {
encryption.ssss.setValidator(MEGOLM_KEY, (String secret) async {
final keyObj = olm.PkDecryption();
try {
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final info = await client.api.getRoomKeysBackup();
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if (info.algorithm != RoomKeysAlgorithmType.v1Curve25519AesSha2) {
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return false;
}
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if (keyObj.init_with_private_key(base64.decode(secret)) ==
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info.authData['public_key']) {
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_requestedSessionIds.clear();
return true;
}
return false;
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} catch (_) {
return false;
} finally {
keyObj.free();
}
});
}
bool get enabled => client.accountData[MEGOLM_KEY] != null;
/// clear all cached inbound group sessions. useful for testing
void clearInboundGroupSessions() {
_inboundGroupSessions.clear();
}
void setInboundGroupSession(String roomId, String sessionId, String senderKey,
Map<String, dynamic> content,
{bool forwarded = false}) {
final oldSession =
getInboundGroupSession(roomId, sessionId, senderKey, otherRooms: false);
if (content['algorithm'] != 'm.megolm.v1.aes-sha2') {
return;
}
olm.InboundGroupSession inboundGroupSession;
try {
inboundGroupSession = olm.InboundGroupSession();
if (forwarded) {
inboundGroupSession.import_session(content['session_key']);
} else {
inboundGroupSession.create(content['session_key']);
}
} catch (e) {
inboundGroupSession.free();
print(
'[LibOlm] Could not create new InboundGroupSession: ' + e.toString());
return;
}
final newSession = SessionKey(
content: content,
inboundGroupSession: inboundGroupSession,
indexes: {},
key: client.userID,
);
final oldFirstIndex =
oldSession?.inboundGroupSession?.first_known_index() ?? 0;
final newFirstIndex = newSession.inboundGroupSession.first_known_index();
if (oldSession == null ||
newFirstIndex < oldFirstIndex ||
(oldFirstIndex == newFirstIndex &&
newSession.forwardingCurve25519KeyChain.length <
oldSession.forwardingCurve25519KeyChain.length)) {
// use new session
oldSession?.dispose();
} else {
// we are gonna keep our old session
newSession.dispose();
return;
}
if (!_inboundGroupSessions.containsKey(roomId)) {
_inboundGroupSessions[roomId] = <String, SessionKey>{};
}
_inboundGroupSessions[roomId][sessionId] = newSession;
client.database?.storeInboundGroupSession(
client.id,
roomId,
sessionId,
inboundGroupSession.pickle(client.userID),
json.encode(content),
json.encode({}),
);
// TODO: somehow try to decrypt last message again
final room = client.getRoomById(roomId);
if (room != null) {
room.onSessionKeyReceived.add(sessionId);
}
}
SessionKey getInboundGroupSession(
String roomId, String sessionId, String senderKey,
{bool otherRooms = true}) {
if (_inboundGroupSessions.containsKey(roomId) &&
_inboundGroupSessions[roomId].containsKey(sessionId)) {
return _inboundGroupSessions[roomId][sessionId];
}
if (!otherRooms) {
return null;
}
// search if this session id is *somehow* found in another room
for (final val in _inboundGroupSessions.values) {
if (val.containsKey(sessionId)) {
return val[sessionId];
}
}
return null;
}
/// Loads an inbound group session
Future<SessionKey> loadInboundGroupSession(
String roomId, String sessionId, String senderKey) async {
if (roomId == null || sessionId == null || senderKey == null) {
return null;
}
if (_inboundGroupSessions.containsKey(roomId) &&
_inboundGroupSessions[roomId].containsKey(sessionId)) {
return _inboundGroupSessions[roomId][sessionId]; // nothing to do
}
final session = await client.database
?.getDbInboundGroupSession(client.id, roomId, sessionId);
if (session == null) {
final room = client.getRoomById(roomId);
final requestIdent = '$roomId|$sessionId|$senderKey';
if (client.enableE2eeRecovery &&
room != null &&
!_requestedSessionIds.contains(requestIdent)) {
// do e2ee recovery
_requestedSessionIds.add(requestIdent);
unawaited(request(room, sessionId, senderKey));
}
return null;
}
if (!_inboundGroupSessions.containsKey(roomId)) {
_inboundGroupSessions[roomId] = <String, SessionKey>{};
}
final sess = SessionKey.fromDb(session, client.userID);
if (!sess.isValid) {
return null;
}
_inboundGroupSessions[roomId][sessionId] = sess;
return sess;
}
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/// clear all cached inbound group sessions. useful for testing
void clearOutboundGroupSessions() {
_outboundGroupSessions.clear();
}
/// Clears the existing outboundGroupSession but first checks if the participating
/// devices have been changed. Returns false if the session has not been cleared because
/// it wasn't necessary.
Future<bool> clearOutboundGroupSession(String roomId,
{bool wipe = false}) async {
final room = client.getRoomById(roomId);
final sess = getOutboundGroupSession(roomId);
if (room == null || sess == null) {
return true;
}
if (!wipe) {
// first check if the devices in the room changed
final deviceKeys = await room.getUserDeviceKeys();
deviceKeys.removeWhere((k) => k.blocked);
final deviceKeyIds = deviceKeys.map((k) => k.deviceId).toList();
deviceKeyIds.sort();
if (deviceKeyIds.toString() != sess.devices.toString()) {
wipe = true;
}
// next check if it needs to be rotated
final encryptionContent = room.getState(EventTypes.Encryption)?.content;
final maxMessages = encryptionContent != null &&
encryptionContent['rotation_period_msgs'] is int
? encryptionContent['rotation_period_msgs']
: 100;
final maxAge = encryptionContent != null &&
encryptionContent['rotation_period_ms'] is int
? encryptionContent['rotation_period_ms']
: 604800000; // default of one week
if (sess.sentMessages >= maxMessages ||
sess.creationTime
.add(Duration(milliseconds: maxAge))
.isBefore(DateTime.now())) {
wipe = true;
}
if (!wipe) {
return false;
}
}
sess.dispose();
_outboundGroupSessions.remove(roomId);
await client.database?.removeOutboundGroupSession(client.id, roomId);
return true;
}
Future<void> storeOutboundGroupSession(
String roomId, OutboundGroupSession sess) async {
if (sess == null) {
return;
}
await client.database?.storeOutboundGroupSession(
client.id,
roomId,
sess.outboundGroupSession.pickle(client.userID),
json.encode(sess.devices),
sess.creationTime,
sess.sentMessages);
}
Future<OutboundGroupSession> createOutboundGroupSession(String roomId) async {
await clearOutboundGroupSession(roomId, wipe: true);
final room = client.getRoomById(roomId);
if (room == null) {
return null;
}
final deviceKeys = await room.getUserDeviceKeys();
deviceKeys.removeWhere((k) => k.blocked);
final deviceKeyIds = deviceKeys.map((k) => k.deviceId).toList();
deviceKeyIds.sort();
final outboundGroupSession = olm.OutboundGroupSession();
try {
outboundGroupSession.create();
} catch (e) {
outboundGroupSession.free();
print('[LibOlm] Unable to create new outboundGroupSession: ' +
e.toString());
return null;
}
final rawSession = <String, dynamic>{
'algorithm': 'm.megolm.v1.aes-sha2',
'room_id': room.id,
'session_id': outboundGroupSession.session_id(),
'session_key': outboundGroupSession.session_key(),
};
setInboundGroupSession(
roomId, rawSession['session_id'], encryption.identityKey, rawSession);
final sess = OutboundGroupSession(
devices: deviceKeyIds,
creationTime: DateTime.now(),
outboundGroupSession: outboundGroupSession,
sentMessages: 0,
key: client.userID,
);
try {
await client.sendToDevice(deviceKeys, 'm.room_key', rawSession);
await storeOutboundGroupSession(roomId, sess);
_outboundGroupSessions[roomId] = sess;
} catch (e, s) {
print(
'[LibOlm] Unable to send the session key to the participating devices: ' +
e.toString());
print(s);
sess.dispose();
return null;
}
return sess;
}
OutboundGroupSession getOutboundGroupSession(String roomId) {
return _outboundGroupSessions[roomId];
}
Future<void> loadOutboundGroupSession(String roomId) async {
if (_loadedOutboundGroupSessions.contains(roomId) ||
_outboundGroupSessions.containsKey(roomId) ||
client.database == null) {
return; // nothing to do
}
_loadedOutboundGroupSessions.add(roomId);
final session =
await client.database.getDbOutboundGroupSession(client.id, roomId);
if (session == null) {
return;
}
final sess = OutboundGroupSession.fromDb(session, client.userID);
if (!sess.isValid) {
return;
}
_outboundGroupSessions[roomId] = sess;
}
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Future<bool> isCached() async {
if (!enabled) {
return false;
}
return (await encryption.ssss.getCached(MEGOLM_KEY)) != null;
}
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Future<void> loadFromResponse(RoomKeys keys) async {
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if (!(await isCached())) {
return;
}
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final privateKey =
base64.decode(await encryption.ssss.getCached(MEGOLM_KEY));
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final decryption = olm.PkDecryption();
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final info = await client.api.getRoomKeysBackup();
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String backupPubKey;
try {
backupPubKey = decryption.init_with_private_key(privateKey);
if (backupPubKey == null ||
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info.algorithm != RoomKeysAlgorithmType.v1Curve25519AesSha2 ||
info.authData['public_key'] != backupPubKey) {
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return;
}
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for (final roomEntry in keys.rooms.entries) {
final roomId = roomEntry.key;
for (final sessionEntry in roomEntry.value.sessions.entries) {
final sessionId = sessionEntry.key;
final session = sessionEntry.value;
final firstMessageIndex = session.firstMessageIndex;
final forwardedCount = session.forwardedCount;
final isVerified = session.isVerified;
final sessionData = session.sessionData;
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if (firstMessageIndex == null ||
forwardedCount == null ||
isVerified == null ||
!(sessionData is Map)) {
continue;
}
Map<String, dynamic> decrypted;
try {
decrypted = json.decode(decryption.decrypt(sessionData['ephemeral'],
sessionData['mac'], sessionData['ciphertext']));
} catch (err) {
print('[LibOlm] Error decrypting room key: ' + err.toString());
}
if (decrypted != null) {
decrypted['session_id'] = sessionId;
decrypted['room_id'] = roomId;
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setInboundGroupSession(
roomId, sessionId, decrypted['sender_key'], decrypted,
forwarded: true);
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}
}
}
} finally {
decryption.free();
}
}
Future<void> loadSingleKey(String roomId, String sessionId) async {
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final info = await client.api.getRoomKeysBackup();
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final ret =
await client.api.getRoomKeysSingleKey(roomId, sessionId, info.version);
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final keys = RoomKeys.fromJson({
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'rooms': {
roomId: {
'sessions': {
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sessionId: ret.toJson(),
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},
},
},
});
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await loadFromResponse(keys);
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}
/// Request a certain key from another device
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Future<void> request(Room room, String sessionId, String senderKey,
{bool tryOnlineBackup = true}) async {
if (tryOnlineBackup) {
// let's first check our online key backup store thingy...
var hadPreviously =
getInboundGroupSession(room.id, sessionId, senderKey) != null;
try {
await loadSingleKey(room.id, sessionId);
} catch (err, stacktrace) {
print('[KeyManager] Failed to access online key backup: ' +
err.toString());
print(stacktrace);
}
if (!hadPreviously &&
getInboundGroupSession(room.id, sessionId, senderKey) != null) {
return; // we managed to load the session from online backup, no need to care about it now
}
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}
// while we just send the to-device event to '*', we still need to save the
// devices themself to know where to send the cancel to after receiving a reply
final devices = await room.getUserDeviceKeys();
final requestId = client.generateUniqueTransactionId();
final request = KeyManagerKeyShareRequest(
requestId: requestId,
devices: devices,
room: room,
sessionId: sessionId,
senderKey: senderKey,
);
await client.sendToDevice(
[],
'm.room_key_request',
{
'action': 'request',
'body': {
'algorithm': 'm.megolm.v1.aes-sha2',
'room_id': room.id,
'sender_key': senderKey,
'session_id': sessionId,
},
'request_id': requestId,
'requesting_device_id': client.deviceID,
},
encrypted: false,
toUsers: await room.requestParticipants());
outgoingShareRequests[request.requestId] = request;
}
/// Handle an incoming to_device event that is related to key sharing
Future<void> handleToDeviceEvent(ToDeviceEvent event) async {
if (event.type == 'm.room_key_request') {
if (!event.content.containsKey('request_id')) {
return; // invalid event
}
if (event.content['action'] == 'request') {
// we are *receiving* a request
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print('[KeyManager] Received key sharing request...');
if (!event.content.containsKey('body')) {
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print('[KeyManager] No body, doing nothing');
return; // no body
}
if (!client.userDeviceKeys.containsKey(event.sender) ||
!client.userDeviceKeys[event.sender].deviceKeys
.containsKey(event.content['requesting_device_id'])) {
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print('[KeyManager] Device not found, doing nothing');
return; // device not found
}
final device = client.userDeviceKeys[event.sender]
.deviceKeys[event.content['requesting_device_id']];
if (device.userId == client.userID &&
device.deviceId == client.deviceID) {
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print('[KeyManager] Request is by ourself, ignoring');
return; // ignore requests by ourself
}
final room = client.getRoomById(event.content['body']['room_id']);
if (room == null) {
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print('[KeyManager] Unknown room, ignoring');
return; // unknown room
}
final sessionId = event.content['body']['session_id'];
final senderKey = event.content['body']['sender_key'];
// okay, let's see if we have this session at all
if ((await loadInboundGroupSession(room.id, sessionId, senderKey)) ==
null) {
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print('[KeyManager] Unknown session, ignoring');
return; // we don't have this session anyways
}
final request = KeyManagerKeyShareRequest(
requestId: event.content['request_id'],
devices: [device],
room: room,
sessionId: sessionId,
senderKey: senderKey,
);
if (incomingShareRequests.containsKey(request.requestId)) {
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print('[KeyManager] Already processed this request, ignoring');
return; // we don't want to process one and the same request multiple times
}
incomingShareRequests[request.requestId] = request;
final roomKeyRequest =
RoomKeyRequest.fromToDeviceEvent(event, this, request);
if (device.userId == client.userID &&
device.verified &&
!device.blocked) {
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print('[KeyManager] All checks out, forwarding key...');
// alright, we can forward the key
await roomKeyRequest.forwardKey();
} else {
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print('[KeyManager] Asking client, if the key should be forwarded');
client.onRoomKeyRequest
.add(roomKeyRequest); // let the client handle this
}
} else if (event.content['action'] == 'request_cancellation') {
// we got told to cancel an incoming request
if (!incomingShareRequests.containsKey(event.content['request_id'])) {
return; // we don't know this request anyways
}
// alright, let's just cancel this request
final request = incomingShareRequests[event.content['request_id']];
request.canceled = true;
incomingShareRequests.remove(request.requestId);
}
} else if (event.type == 'm.forwarded_room_key') {
// we *received* an incoming key request
if (event.encryptedContent == null) {
return; // event wasn't encrypted, this is a security risk
}
final request = outgoingShareRequests.values.firstWhere(
(r) =>
r.room.id == event.content['room_id'] &&
r.sessionId == event.content['session_id'] &&
r.senderKey == event.content['sender_key'],
orElse: () => null);
if (request == null || request.canceled) {
return; // no associated request found or it got canceled
}
final device = request.devices.firstWhere(
(d) =>
d.userId == event.sender &&
d.curve25519Key == event.encryptedContent['sender_key'],
orElse: () => null);
if (device == null) {
return; // someone we didn't send our request to replied....better ignore this
}
// TODO: verify that the keys work to decrypt a message
// alright, all checks out, let's go ahead and store this session
setInboundGroupSession(
request.room.id, request.sessionId, request.senderKey, event.content,
forwarded: true);
request.devices.removeWhere(
(k) => k.userId == device.userId && k.deviceId == device.deviceId);
outgoingShareRequests.remove(request.requestId);
// send cancel to all other devices
if (request.devices.isEmpty) {
return; // no need to send any cancellation
}
await client.sendToDevice(
request.devices,
'm.room_key_request',
{
'action': 'request_cancellation',
'request_id': request.requestId,
'requesting_device_id': client.deviceID,
},
encrypted: false);
} else if (event.type == 'm.room_key') {
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if (event.encryptedContent == null) {
return; // the event wasn't encrypted, this is a security risk;
}
final String roomId = event.content['room_id'];
final String sessionId = event.content['session_id'];
if (client.userDeviceKeys.containsKey(event.sender) &&
client.userDeviceKeys[event.sender].deviceKeys
.containsKey(event.content['requesting_device_id'])) {
event.content['sender_claimed_ed25519_key'] = client
.userDeviceKeys[event.sender]
.deviceKeys[event.content['requesting_device_id']]
.ed25519Key;
}
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setInboundGroupSession(roomId, sessionId,
event.encryptedContent['sender_key'], event.content,
forwarded: false);
}
}
void dispose() {
for (final sess in _outboundGroupSessions.values) {
sess.dispose();
}
for (final entries in _inboundGroupSessions.values) {
for (final sess in entries.values) {
sess.dispose();
}
}
}
}
class KeyManagerKeyShareRequest {
final String requestId;
final List<DeviceKeys> devices;
final Room room;
final String sessionId;
final String senderKey;
bool canceled;
KeyManagerKeyShareRequest(
{this.requestId,
this.devices,
this.room,
this.sessionId,
this.senderKey,
this.canceled = false});
}
class RoomKeyRequest extends ToDeviceEvent {
KeyManager keyManager;
KeyManagerKeyShareRequest request;
RoomKeyRequest.fromToDeviceEvent(ToDeviceEvent toDeviceEvent,
KeyManager keyManager, KeyManagerKeyShareRequest request) {
this.keyManager = keyManager;
this.request = request;
sender = toDeviceEvent.sender;
content = toDeviceEvent.content;
type = toDeviceEvent.type;
}
Room get room => request.room;
DeviceKeys get requestingDevice => request.devices.first;
Future<void> forwardKey() async {
if (request.canceled) {
keyManager.incomingShareRequests.remove(request.requestId);
return; // request is canceled, don't send anything
}
var room = this.room;
final session = await keyManager.loadInboundGroupSession(
room.id, request.sessionId, request.senderKey);
var forwardedKeys = <dynamic>[keyManager.encryption.identityKey];
for (final key in session.forwardingCurve25519KeyChain) {
forwardedKeys.add(key);
}
var message = session.content;
message['forwarding_curve25519_key_chain'] = forwardedKeys;
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message['sender_key'] = request.senderKey;
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message['sender_claimed_ed25519_key'] =
forwardedKeys.isEmpty ? keyManager.encryption.fingerprintKey : null;
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if (message['sender_claimed_ed25519_key'] == null) {
for (final value in keyManager.client.userDeviceKeys.values) {
for (final key in value.deviceKeys.values) {
if (key.curve25519Key == forwardedKeys.first) {
message['sender_claimed_ed25519_key'] = key.ed25519Key;
}
}
if (message['sender_claimed_ed25519_key'] != null) {
break;
}
}
}
message['session_key'] = session.inboundGroupSession
.export_session(session.inboundGroupSession.first_known_index());
// send the actual reply of the key back to the requester
await keyManager.client.sendToDevice(
[requestingDevice],
'm.forwarded_room_key',
message,
);
keyManager.incomingShareRequests.remove(request.requestId);
}
}