famedlysdk/lib/encryption/olm_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:canonical_json/canonical_json.dart';
import 'package:famedlysdk/famedlysdk.dart';
import 'package:famedlysdk/matrix_api.dart';
import 'package:olm/olm.dart' as olm;
import './encryption.dart';
class OlmManager {
final Encryption encryption;
Client get client => encryption.client;
olm.Account _olmAccount;
/// Returns the base64 encoded keys to store them in a store.
/// This String should **never** leave the device!
String get pickledOlmAccount =>
enabled ? _olmAccount.pickle(client.userID) : null;
String get fingerprintKey =>
enabled ? json.decode(_olmAccount.identity_keys())['ed25519'] : null;
String get identityKey =>
enabled ? json.decode(_olmAccount.identity_keys())['curve25519'] : null;
bool get enabled => _olmAccount != null;
OlmManager(this.encryption);
/// A map from Curve25519 identity keys to existing olm sessions.
Map<String, List<olm.Session>> get olmSessions => _olmSessions;
final Map<String, List<olm.Session>> _olmSessions = {};
Future<void> init(String olmAccount) async {
if (olmAccount == null) {
try {
await olm.init();
_olmAccount = olm.Account();
_olmAccount.create();
if (await uploadKeys(uploadDeviceKeys: true) == false) {
throw ('Upload key failed');
}
} catch (_) {
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_olmAccount?.free();
_olmAccount = null;
}
} else {
try {
await olm.init();
_olmAccount = olm.Account();
_olmAccount.unpickle(client.userID, olmAccount);
} catch (_) {
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_olmAccount?.free();
_olmAccount = null;
}
}
}
/// Adds a signature to this json from this olm account.
Map<String, dynamic> signJson(Map<String, dynamic> payload) {
if (!enabled) throw ('Encryption is disabled');
final Map<String, dynamic> unsigned = payload['unsigned'];
final Map<String, dynamic> signatures = payload['signatures'];
payload.remove('unsigned');
payload.remove('signatures');
final canonical = canonicalJson.encode(payload);
final signature = _olmAccount.sign(String.fromCharCodes(canonical));
if (signatures != null) {
payload['signatures'] = signatures;
} else {
payload['signatures'] = <String, dynamic>{};
}
if (!payload['signatures'].containsKey(client.userID)) {
payload['signatures'][client.userID] = <String, dynamic>{};
}
payload['signatures'][client.userID]['ed25519:${client.deviceID}'] =
signature;
if (unsigned != null) {
payload['unsigned'] = unsigned;
}
return payload;
}
/// Checks the signature of a signed json object.
bool checkJsonSignature(String key, Map<String, dynamic> signedJson,
String userId, String deviceId) {
if (!enabled) throw ('Encryption is disabled');
final Map<String, dynamic> signatures = signedJson['signatures'];
if (signatures == null || !signatures.containsKey(userId)) return false;
signedJson.remove('unsigned');
signedJson.remove('signatures');
if (!signatures[userId].containsKey('ed25519:$deviceId')) return false;
final String signature = signatures[userId]['ed25519:$deviceId'];
final canonical = canonicalJson.encode(signedJson);
final message = String.fromCharCodes(canonical);
var isValid = false;
final olmutil = olm.Utility();
try {
olmutil.ed25519_verify(key, message, signature);
isValid = true;
} catch (e) {
isValid = false;
print('[LibOlm] Signature check failed: ' + e.toString());
} finally {
olmutil.free();
}
return isValid;
}
/// Generates new one time keys, signs everything and upload it to the server.
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Future<bool> uploadKeys(
{bool uploadDeviceKeys = false, int oldKeyCount = 0}) async {
if (!enabled) {
return true;
}
// generate one-time keys
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// we generate 2/3rds of max, so that other keys people may still have can
// still be used
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final oneTimeKeysCount =
(_olmAccount.max_number_of_one_time_keys() * 2 / 3).floor() -
oldKeyCount;
_olmAccount.generate_one_time_keys(oneTimeKeysCount);
final Map<String, dynamic> oneTimeKeys =
json.decode(_olmAccount.one_time_keys());
// now sign all the one-time keys
final signedOneTimeKeys = <String, dynamic>{};
for (final entry in oneTimeKeys['curve25519'].entries) {
final key = entry.key;
final value = entry.value;
signedOneTimeKeys['signed_curve25519:$key'] = <String, dynamic>{};
signedOneTimeKeys['signed_curve25519:$key'] = signJson({
'key': value,
});
}
// and now generate the payload to upload
final keysContent = <String, dynamic>{
if (uploadDeviceKeys)
'device_keys': {
'user_id': client.userID,
'device_id': client.deviceID,
'algorithms': [
'm.olm.v1.curve25519-aes-sha2',
'm.megolm.v1.aes-sha2'
],
'keys': <String, dynamic>{},
},
};
if (uploadDeviceKeys) {
final Map<String, dynamic> keys =
json.decode(_olmAccount.identity_keys());
for (final entry in keys.entries) {
final algorithm = entry.key;
final value = entry.value;
keysContent['device_keys']['keys']['$algorithm:${client.deviceID}'] =
value;
}
keysContent['device_keys'] =
signJson(keysContent['device_keys'] as Map<String, dynamic>);
}
final response = await client.api.uploadDeviceKeys(
deviceKeys: uploadDeviceKeys
? MatrixDeviceKeys.fromJson(keysContent['device_keys'])
: null,
oneTimeKeys: signedOneTimeKeys,
);
_olmAccount.mark_keys_as_published();
await client.database?.updateClientKeys(pickledOlmAccount, client.id);
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return response['signed_curve25519'] == oneTimeKeysCount;
}
void handleDeviceOneTimeKeysCount(Map<String, int> countJson) {
if (!enabled) {
return;
}
// Check if there are at least half of max_number_of_one_time_keys left on the server
// and generate and upload more if not.
if (countJson.containsKey('signed_curve25519') &&
countJson['signed_curve25519'] <
(_olmAccount.max_number_of_one_time_keys() / 2)) {
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uploadKeys(oldKeyCount: countJson['signed_curve25519']);
}
}
void storeOlmSession(String curve25519IdentityKey, olm.Session session) {
if (client.database == null) {
return;
}
if (!_olmSessions.containsKey(curve25519IdentityKey)) {
_olmSessions[curve25519IdentityKey] = [];
}
final ix = _olmSessions[curve25519IdentityKey]
.indexWhere((s) => s.session_id() == session.session_id());
if (ix == -1) {
// add a new session
_olmSessions[curve25519IdentityKey].add(session);
} else {
// update an existing session
_olmSessions[curve25519IdentityKey][ix] = session;
}
final pickle = session.pickle(client.userID);
client.database.storeOlmSession(
client.id, curve25519IdentityKey, session.session_id(), pickle);
}
ToDeviceEvent _decryptToDeviceEvent(ToDeviceEvent event) {
if (event.type != EventTypes.Encrypted) {
return event;
}
if (event.content['algorithm'] != 'm.olm.v1.curve25519-aes-sha2') {
throw ('Unknown algorithm: ${event.content}');
}
if (!event.content['ciphertext'].containsKey(identityKey)) {
throw ("The message isn't sent for this device");
}
String plaintext;
final String senderKey = event.content['sender_key'];
final String body = event.content['ciphertext'][identityKey]['body'];
final int type = event.content['ciphertext'][identityKey]['type'];
if (type != 0 && type != 1) {
throw ('Unknown message type');
}
var existingSessions = olmSessions[senderKey];
if (existingSessions != null) {
for (var session in existingSessions) {
if (type == 0 && session.matches_inbound(body) == true) {
plaintext = session.decrypt(type, body);
storeOlmSession(senderKey, session);
break;
} else if (type == 1) {
try {
plaintext = session.decrypt(type, body);
storeOlmSession(senderKey, session);
break;
} catch (_) {
plaintext = null;
}
}
}
}
if (plaintext == null && type != 0) {
return event;
}
if (plaintext == null) {
var newSession = olm.Session();
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try {
newSession.create_inbound_from(_olmAccount, senderKey, body);
_olmAccount.remove_one_time_keys(newSession);
client.database?.updateClientKeys(pickledOlmAccount, client.id);
plaintext = newSession.decrypt(type, body);
storeOlmSession(senderKey, newSession);
} catch (_) {
newSession?.free();
rethrow;
}
}
final Map<String, dynamic> plainContent = json.decode(plaintext);
if (plainContent.containsKey('sender') &&
plainContent['sender'] != event.sender) {
throw ("Message was decrypted but sender doesn't match");
}
if (plainContent.containsKey('recipient') &&
plainContent['recipient'] != client.userID) {
throw ("Message was decrypted but recipient doesn't match");
}
if (plainContent['recipient_keys'] is Map &&
plainContent['recipient_keys']['ed25519'] is String &&
plainContent['recipient_keys']['ed25519'] != fingerprintKey) {
throw ("Message was decrypted but own fingerprint Key doesn't match");
}
return ToDeviceEvent(
content: plainContent['content'],
encryptedContent: event.content,
type: plainContent['type'],
sender: event.sender,
);
}
Future<ToDeviceEvent> decryptToDeviceEvent(ToDeviceEvent event) async {
if (event.type != EventTypes.Encrypted) {
return event;
}
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final senderKey = event.content['sender_key'];
final loadFromDb = () async {
if (client.database == null) {
return false;
}
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final sessions = await client.database
.getSingleOlmSessions(client.id, senderKey, client.userID);
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if (sessions.isEmpty) {
return false; // okay, can't do anything
}
_olmSessions[senderKey] = sessions;
return true;
};
if (!_olmSessions.containsKey(senderKey)) {
await loadFromDb();
}
event = _decryptToDeviceEvent(event);
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if (event.type != EventTypes.Encrypted || !(await loadFromDb())) {
return event;
}
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// retry to decrypt!
return _decryptToDeviceEvent(event);
}
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Future<void> startOutgoingOlmSessions(List<DeviceKeys> deviceKeys) async {
var requestingKeysFrom = <String, Map<String, String>>{};
for (var device in deviceKeys) {
if (requestingKeysFrom[device.userId] == null) {
requestingKeysFrom[device.userId] = {};
}
requestingKeysFrom[device.userId][device.deviceId] = 'signed_curve25519';
}
final response =
await client.api.requestOneTimeKeys(requestingKeysFrom, timeout: 10000);
for (var userKeysEntry in response.oneTimeKeys.entries) {
final userId = userKeysEntry.key;
for (var deviceKeysEntry in userKeysEntry.value.entries) {
final deviceId = deviceKeysEntry.key;
final fingerprintKey =
client.userDeviceKeys[userId].deviceKeys[deviceId].ed25519Key;
final identityKey =
client.userDeviceKeys[userId].deviceKeys[deviceId].curve25519Key;
for (Map<String, dynamic> deviceKey in deviceKeysEntry.value.values) {
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if (!checkJsonSignature(
fingerprintKey, deviceKey, userId, deviceId)) {
continue;
}
try {
var session = olm.Session();
session.create_outbound(_olmAccount, identityKey, deviceKey['key']);
await storeOlmSession(identityKey, session);
} catch (e) {
print('[LibOlm] Could not create new outbound olm session: ' +
e.toString());
}
}
}
}
}
Future<Map<String, dynamic>> encryptToDeviceMessagePayload(
DeviceKeys device, String type, Map<String, dynamic> payload) async {
var sess = olmSessions[device.curve25519Key];
if (sess == null || sess.isEmpty) {
final sessions = await client.database
.getSingleOlmSessions(client.id, device.curve25519Key, client.userID);
if (sessions.isEmpty) {
throw ('No olm session found');
}
sess = _olmSessions[device.curve25519Key] = sessions;
}
sess.sort((a, b) => a.session_id().compareTo(b.session_id()));
final fullPayload = {
'type': type,
'content': payload,
'sender': client.userID,
'keys': {'ed25519': fingerprintKey},
'recipient': device.userId,
'recipient_keys': {'ed25519': device.ed25519Key},
};
final encryptResult = sess.first.encrypt(json.encode(fullPayload));
storeOlmSession(device.curve25519Key, sess.first);
final encryptedBody = <String, dynamic>{
'algorithm': 'm.olm.v1.curve25519-aes-sha2',
'sender_key': identityKey,
'ciphertext': <String, dynamic>{},
};
encryptedBody['ciphertext'][device.curve25519Key] = {
'type': encryptResult.type,
'body': encryptResult.body,
};
return encryptedBody;
}
Future<Map<String, dynamic>> encryptToDeviceMessage(
List<DeviceKeys> deviceKeys,
String type,
Map<String, dynamic> payload) async {
var data = <String, Map<String, Map<String, dynamic>>>{};
final deviceKeysWithoutSession = List<DeviceKeys>.from(deviceKeys);
deviceKeysWithoutSession.removeWhere((DeviceKeys deviceKeys) =>
olmSessions.containsKey(deviceKeys.curve25519Key));
if (deviceKeysWithoutSession.isNotEmpty) {
await startOutgoingOlmSessions(deviceKeysWithoutSession);
}
for (final device in deviceKeys) {
if (!data.containsKey(device.userId)) {
data[device.userId] = {};
}
try {
data[device.userId][device.deviceId] =
await encryptToDeviceMessagePayload(device, type, payload);
} catch (e) {
print('[LibOlm] Error encrypting to-device event: ' + e.toString());
continue;
}
}
return data;
}
void dispose() {
for (final sessions in olmSessions.values) {
for (final sess in sessions) {
sess.free();
}
}
_olmAccount?.free();
_olmAccount = null;
}
}