diff options
| -rw-r--r-- | changelog.d/6850.misc | 1 | ||||
| -rw-r--r-- | synapse/handlers/device.py | 8 | ||||
| -rw-r--r-- | synapse/handlers/federation.py | 72 |
3 files changed, 67 insertions, 14 deletions
diff --git a/changelog.d/6850.misc b/changelog.d/6850.misc new file mode 100644 index 0000000000..418569113f --- /dev/null +++ b/changelog.d/6850.misc @@ -0,0 +1 @@ +Detect unexpected sender keys on inbound encrypted events and resync device lists. diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py index 26ef5e150c..a9bd431486 100644 --- a/synapse/handlers/device.py +++ b/synapse/handlers/device.py @@ -598,7 +598,13 @@ class DeviceListUpdater(object): # happens if we've missed updates. resync = yield self._need_to_do_resync(user_id, pending_updates) - logger.debug("Need to re-sync devices for %r? %r", user_id, resync) + if logger.isEnabledFor(logging.INFO): + logger.info( + "Received device list update for %s, requiring resync: %s. Devices: %s", + user_id, + resync, + ", ".join(u[0] for u in pending_updates), + ) if resync: yield self.user_device_resync(user_id) diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 488200a2d1..e9441bbeff 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -754,27 +754,73 @@ class FederationHandler(BaseHandler): # if we don't then we mark the device cache for that user as stale. if event.type == EventTypes.Encrypted: device_id = event.content.get("device_id") + sender_key = event.content.get("sender_key") + + cached_devices = await self.store.get_cached_devices_for_user(event.sender) + + resync = False # Whether we should resync device lists. + + device = None if device_id is not None: - cached_devices = await self.store.get_cached_devices_for_user( - event.sender - ) - if device_id not in cached_devices: + device = cached_devices.get(device_id) + if device is None: logger.info( "Received event from remote device not in our cache: %s %s", event.sender, device_id, ) - await self.store.mark_remote_user_device_cache_as_stale( - event.sender + resync = True + + # We also check if the `sender_key` matches what we expect. + if sender_key is not None: + # Figure out what sender key we're expecting. If we know the + # device and recognize the algorithm then we can work out the + # exact key to expect. Otherwise check it matches any key we + # have for that device. + if device: + keys = device.get("keys", {}).get("keys", {}) + + if event.content.get("algorithm") == "m.megolm.v1.aes-sha2": + # For this algorithm we expect a curve25519 key. + key_name = "curve25519:%s" % (device_id,) + current_keys = [keys.get(key_name)] + else: + # We don't know understand the algorithm, so we just + # check it matches a key for the device. + current_keys = keys.values() + elif device_id: + # We don't have any keys for the device ID. + current_keys = [] + else: + # The event didn't include a device ID, so we just look for + # keys across all devices. + current_keys = ( + key + for device in cached_devices + for key in device.get("keys", {}).get("keys", {}).values() ) - # Immediately attempt a resync in the background - if self.config.worker_app: - return run_in_background(self._user_device_resync, event.sender) - else: - return run_in_background( - self._device_list_updater.user_device_resync, event.sender - ) + # We now check that the sender key matches (one of) the expected + # keys. + if sender_key not in current_keys: + logger.info( + "Received event from remote device with unexpected sender key: %s %s: %s", + event.sender, + device_id or "<no device_id>", + sender_key, + ) + resync = True + + if resync: + await self.store.mark_remote_user_device_cache_as_stale(event.sender) + + # Immediately attempt a resync in the background + if self.config.worker_app: + return run_in_background(self._user_device_resync, event.sender) + else: + return run_in_background( + self._device_list_updater.user_device_resync, event.sender + ) @log_function async def backfill(self, dest, room_id, limit, extremities): |