Improve event validation (#16908)

As the title states.

1 files changed, 11 insertions, 1 deletions

diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 0aedb37f16..3aa2e2b7ba 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -41,6 +41,7 @@ from synapse.api.constants import (
     AccountDataTypes,
     EventContentFields,
     EventTypes,
+    JoinRules,
     Membership,
 )
 from synapse.api.filtering import FilterCollection
@@ -675,13 +676,22 @@ class SyncHandler:
                         )
                     )
 
-                loaded_recents = await filter_events_for_client(
+                filtered_recents = await filter_events_for_client(
                     self._storage_controllers,
                     sync_config.user.to_string(),
                     loaded_recents,
                     always_include_ids=current_state_ids,
                 )
 
+                loaded_recents = []
+                for event in filtered_recents:
+                    if event.type == EventTypes.CallInvite:
+                        room_info = await self.store.get_room_with_stats(event.room_id)
+                        assert room_info is not None
+                        if room_info.join_rules == JoinRules.PUBLIC:
+                            continue
+                    loaded_recents.append(event)
+
                 log_kv({"loaded_recents_after_client_filtering": len(loaded_recents)})
 
                 loaded_recents.extend(recents)