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):
|
