Move some event auth checks out to a different method (#13065)

* Add auth events to events used in tests

* Move some event auth checks out to a different method

Some of the event auth checks apply to an event's auth_events, rather than the
state at the event - which means they can play no part in state
resolution. Move them out to a separate method.

* Rename check_auth_rules_for_event

Now it only checks the state-dependent auth rules, it needs a better name.

2 files changed, 23 insertions, 12 deletions

diff --git a/synapse/handlers/event_auth.py b/synapse/handlers/event_auth.py

index ed4149bd58..a2dd9c7efa 100644
--- a/synapse/handlers/event_auth.py
+++ b/synapse/handlers/event_auth.py
@@ -23,7 +23,10 @@ from synapse.api.constants import (
 )
 from synapse.api.errors import AuthError, Codes, SynapseError
 from synapse.api.room_versions import RoomVersion
-from synapse.event_auth import check_auth_rules_for_event
+from synapse.event_auth import (
+    check_state_dependent_auth_rules,
+    check_state_independent_auth_rules,
+)
 from synapse.events import EventBase
 from synapse.events.builder import EventBuilder
 from synapse.events.snapshot import EventContext
@@ -52,9 +55,10 @@ class EventAuthHandler:
         context: EventContext,
     ) -> None:
         """Check an event passes the auth rules at its own auth events"""
+        await check_state_independent_auth_rules(self._store, event)
         auth_event_ids = event.auth_event_ids()
         auth_events_by_id = await self._store.get_events(auth_event_ids)
-        check_auth_rules_for_event(event, auth_events_by_id.values())
+        check_state_dependent_auth_rules(event, auth_events_by_id.values())
 
     def compute_auth_events(
         self,
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py

index 6c9e6a00b5..565ffd7cfd 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -50,7 +50,8 @@ from synapse.api.errors import (
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion, RoomVersions
 from synapse.event_auth import (
     auth_types_for_event,
-    check_auth_rules_for_event,
+    check_state_dependent_auth_rules,
+    check_state_independent_auth_rules,
     validate_event_for_room_version,
 )
 from synapse.events import EventBase
@@ -1430,7 +1431,9 @@ class FederationEventHandler:
             allow_rejected=True,
         )
 
-        def prep(event: EventBase) -> Optional[Tuple[EventBase, EventContext]]:
+        events_and_contexts_to_persist: List[Tuple[EventBase, EventContext]] = []
+
+        async def prep(event: EventBase) -> None:
             with nested_logging_context(suffix=event.event_id):
                 auth = []
                 for auth_event_id in event.auth_event_ids():
@@ -1444,7 +1447,7 @@ class FederationEventHandler:
                             event,
                             auth_event_id,
                         )
-                        return None
+                        return
                     auth.append(ae)
 
                 # we're not bothering about room state, so flag the event as an outlier.
@@ -1453,17 +1456,20 @@ class FederationEventHandler:
                 context = EventContext.for_outlier(self._storage_controllers)
                 try:
                     validate_event_for_room_version(event)
-                    check_auth_rules_for_event(event, auth)
+                    await check_state_independent_auth_rules(self._store, event)
+                    check_state_dependent_auth_rules(event, auth)
                 except AuthError as e:
                     logger.warning("Rejecting %r because %s", event, e)
                     context.rejected = RejectedReason.AUTH_ERROR
 
-            return event, context
+            events_and_contexts_to_persist.append((event, context))
+
+        for event in fetched_events:
+            await prep(event)
 
-        events_to_persist = (x for x in (prep(event) for event in fetched_events) if x)
         await self.persist_events_and_notify(
             room_id,
-            tuple(events_to_persist),
+            events_and_contexts_to_persist,
             # Mark these events backfilled as they're historic events that will
             # eventually be backfilled. For example, missing events we fetch
             # during backfill should be marked as backfilled as well.
@@ -1515,7 +1521,8 @@ class FederationEventHandler:
 
         # ... and check that the event passes auth at those auth events.
         try:
-            check_auth_rules_for_event(event, claimed_auth_events)
+            await check_state_independent_auth_rules(self._store, event)
+            check_state_dependent_auth_rules(event, claimed_auth_events)
         except AuthError as e:
             logger.warning(
                 "While checking auth of %r against auth_events: %s", event, e
@@ -1563,7 +1570,7 @@ class FederationEventHandler:
             auth_events_for_auth = calculated_auth_event_map
 
         try:
-            check_auth_rules_for_event(event, auth_events_for_auth.values())
+            check_state_dependent_auth_rules(event, auth_events_for_auth.values())
         except AuthError as e:
             logger.warning("Failed auth resolution for %r because %s", event, e)
             context.rejected = RejectedReason.AUTH_ERROR
@@ -1663,7 +1670,7 @@ class FederationEventHandler:
         )
 
         try:
-            check_auth_rules_for_event(event, current_auth_events)
+            check_state_dependent_auth_rules(event, current_auth_events)
         except AuthError as e:
             logger.warning(
                 "Soft-failing %r (from %s) because %s",