feat: Implement a BTBV TrustManager

This commit is contained in:
PapaTutuWawa 2022-08-08 18:47:43 +02:00
parent dafd0af1e5
commit c1fb79a20f
6 changed files with 155 additions and 1 deletions

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@ -12,5 +12,5 @@ export 'src/omemo/encryption_result.dart';
export 'src/omemo/fingerprint.dart'; export 'src/omemo/fingerprint.dart';
export 'src/omemo/sessionmanager.dart'; export 'src/omemo/sessionmanager.dart';
export 'src/trust/base.dart'; export 'src/trust/base.dart';
//export 'src/trust/btbv.dart'; export 'src/trust/btbv.dart';
export 'src/x3dh/x3dh.dart'; export 'src/x3dh/x3dh.dart';

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@ -134,6 +134,7 @@ class OmemoSessionManager {
kexResult.ad, kexResult.ad,
); );
await _trustManager.onNewSession(jid, deviceId);
await _addSession(jid, deviceId, ratchet); await _addSession(jid, deviceId, ratchet);
return OmemoKeyExchange() return OmemoKeyExchange()
@ -177,6 +178,7 @@ class OmemoSessionManager {
kexResult.ad, kexResult.ad,
); );
await _trustManager.onNewSession(jid, deviceId);
await _addSession(jid, deviceId, ratchet); await _addSession(jid, deviceId, ratchet);
} }

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@ -8,4 +8,7 @@ import 'package:omemo_dart/src/trust/base.dart';
class AlwaysTrustingTrustManager extends TrustManager { class AlwaysTrustingTrustManager extends TrustManager {
@override @override
Future<bool> isTrusted(String jid, int deviceId) async => true; Future<bool> isTrusted(String jid, int deviceId) async => true;
@override
Future<void> onNewSession(String jid, int deviceId) async {}
} }

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@ -4,4 +4,8 @@ abstract class TrustManager {
/// Return true when the device with id [deviceId] of Jid [jid] is trusted, i.e. if an /// Return true when the device with id [deviceId] of Jid [jid] is trusted, i.e. if an
/// encrypted message should be sent to this device. If not, return false. /// encrypted message should be sent to this device. If not, return false.
Future<bool> isTrusted(String jid, int deviceId); Future<bool> isTrusted(String jid, int deviceId);
/// 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);
} }

109
lib/src/trust/btbv.dart Normal file
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@ -0,0 +1,109 @@
import 'package:meta/meta.dart';
import 'package:omemo_dart/src/omemo/ratchet_map_key.dart';
import 'package:omemo_dart/src/trust/base.dart';
import 'package:synchronized/synchronized.dart';
/// Every device is in either of those two trust states:
/// - notTrusted: The device is absolutely not trusted
/// - blindTrust: The fingerprint is not verified using OOB means
/// - verified: The fingerprint has been verified using OOB means
enum BTBVTrustState {
notTrusted,
blindTrust,
verified,
}
class BlindTrustBeforeVerificationTrustManager extends TrustManager {
BlindTrustBeforeVerificationTrustManager()
: _trustCache = {},
_devices = {},
_lock = Lock();
/// The cache for Mapping a RatchetMapKey to its trust state
final Map<RatchetMapKey, BTBVTrustState> _trustCache;
/// Mapping of Jids to their device identifiers
final Map<String, List<int>> _devices;
/// The lock for _devices and _trustCache
final Lock _lock;
/// Returns true if [jid] has at least one device that is verified. If not, returns false.
/// Note that this function accesses _devices and _trustCache, which requires that the
/// lock for those two maps (_lock) has been aquired before calling.
bool _hasAtLeastOneVerifiedDevice(String jid) {
if (!_devices.containsKey(jid)) return false;
return _devices[jid]!.any((id) {
return _trustCache[RatchetMapKey(jid, id)]! == BTBVTrustState.verified;
});
}
@override
Future<bool> isTrusted(String jid, int deviceId) async {
var returnValue = false;
await _lock.synchronized(() async {
final trustCacheValue = _trustCache[RatchetMapKey(jid, deviceId)];
if (trustCacheValue == BTBVTrustState.notTrusted) {
returnValue = false;
return;
} else if (trustCacheValue == BTBVTrustState.verified) {
// The key is verified, so it's safe.
returnValue = true;
return;
} else {
if (_hasAtLeastOneVerifiedDevice(jid)) {
// Do not trust if there is at least one device with full trust
returnValue = false;
return;
} else {
// We have not verified a key from [jid], so it is blind trust all the way.
returnValue = true;
return;
}
}
});
return returnValue;
}
@override
Future<void> onNewSession(String jid, int deviceId) async {
await _lock.synchronized(() async {
if (_hasAtLeastOneVerifiedDevice(jid)) {
_trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.notTrusted;
} else {
_trustCache[RatchetMapKey(jid, deviceId)] = BTBVTrustState.blindTrust;
}
if (_devices.containsKey(jid)) {
_devices[jid]!.add(deviceId);
} else {
_devices[jid] = List<int>.from([deviceId]);
}
});
}
/// Returns a mapping from the device identifiers of [jid] to their trust state.
Future<Map<int, BTBVTrustState>> getDevicesTrust(String jid) async {
final map = <int, BTBVTrustState>{};
await _lock.synchronized(() async {
for (final deviceId in _devices[jid]!) {
map[deviceId] = _trustCache[RatchetMapKey(jid, deviceId)]!;
}
});
return map;
}
/// Sets the trust of [jid]'s device with identifier [deviceId] to [state].
Future<void> setDeviceTrust(String jid, int deviceId, BTBVTrustState state) async {
await _lock.synchronized(() async {
_trustCache[RatchetMapKey(jid, deviceId)] = state;
});
}
@visibleForTesting
BTBVTrustState getDeviceTrust(String jid, int deviceId) => _trustCache[RatchetMapKey(jid, deviceId)]!;
}

36
test/trust_test.dart Normal file
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@ -0,0 +1,36 @@
import 'package:omemo_dart/omemo_dart.dart';
import 'package:test/test.dart';
void main() {
test('Test the Blind Trust Before Verification TrustManager', () async {
// Caroline's BTBV manager
final btbv = BlindTrustBeforeVerificationTrustManager();
// Example data
const aliceJid = 'alice@some.server';
const bobJid = 'bob@other.server';
// Caroline starts a chat a device from Alice
await btbv.onNewSession(aliceJid, 1);
expect(await btbv.isTrusted(aliceJid, 1), true);
// Caroline meets with Alice and verifies her fingerprint
await btbv.setDeviceTrust(aliceJid, 1, BTBVTrustState.verified);
expect(await btbv.isTrusted(aliceJid, 1), true);
// Alice adds a new device
await btbv.onNewSession(aliceJid, 2);
expect(await btbv.isTrusted(aliceJid, 2), false);
expect(btbv.getDeviceTrust(aliceJid, 2), BTBVTrustState.notTrusted);
// Caronline starts a chat with Bob but since they live far apart, Caroline cannot
// verify his fingerprint.
await btbv.onNewSession(bobJid, 3);
// Bob adds a new device
await btbv.onNewSession(bobJid, 4);
expect(await btbv.isTrusted(bobJid, 3), true);
expect(await btbv.isTrusted(bobJid, 4), true);
expect(btbv.getDeviceTrust(bobJid, 3), BTBVTrustState.blindTrust);
expect(btbv.getDeviceTrust(bobJid, 4), BTBVTrustState.blindTrust);
});
}