Fix DoS when there is a cycle in redaction events

Make sure that synapse doesn't explode when a redaction redacts itself, or there is a larger cycle.
matrix-org · Jul 26, 2019 · 0f2ecb9 · 0f2ecb9
1 parent 70e18ce
commit 0f2ecb9
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
@@ -637,6 +637,10 @@ def _maybe_redact_event_row(self, original_ev, redactions):
             # we choose to ignore redactions of m.room.create events.
             return None
 
+        if original_ev.type == "m.room.redaction":
+            # ... and redaction events
+            return None
+
         redaction_map = yield self._get_events_from_cache_or_db(redactions)
 
         for redaction_id in redactions: