Merge pull request #3641 from matrix-org/rav/room_id_check

Validation for events/rooms in fed requests

changelog.d/3641.bugfix

@@ -0,0 +1 @@
+Fix a potential event disclosure issue

synapse/federation/federation_server.py

@@ -425,6 +425,7 @@ class FederationServer(FederationBase):
             ret = yield self.handler.on_query_auth(
                 origin,
                 event_id,
+                room_id,
                 signed_auth,
                 content.get("rejects", []),
                 content.get("missing", []),

synapse/handlers/federation.py

@@ -1349,6 +1349,11 @@ class FederationHandler(BaseHandler):
     def get_state_for_pdu(self, room_id, event_id):
         """Returns the state at the event. i.e. not including said event.
         """
+
+        event = yield self.store.get_event(
+            event_id, allow_none=False, check_room_id=room_id,
+        )
+
         state_groups = yield self.store.get_state_groups(
             room_id, [event_id]
         )
@@ -1359,8 +1364,7 @@ class FederationHandler(BaseHandler):
                 (e.type, e.state_key): e for e in state
             }
 
-            event = yield self.store.get_event(event_id)
-            if event and event.is_state():
+            if event.is_state():
                 # Get previous state
                 if "replaces_state" in event.unsigned:
                     prev_id = event.unsigned["replaces_state"]
@@ -1391,6 +1395,10 @@ class FederationHandler(BaseHandler):
     def get_state_ids_for_pdu(self, room_id, event_id):
         """Returns the state at the event. i.e. not including said event.
         """
+        event = yield self.store.get_event(
+            event_id, allow_none=False, check_room_id=room_id,
+        )
+
         state_groups = yield self.store.get_state_groups_ids(
             room_id, [event_id]
         )
@@ -1399,8 +1407,7 @@ class FederationHandler(BaseHandler):
             _, state = state_groups.items().pop()
             results = state
 
-            event = yield self.store.get_event(event_id)
-            if event and event.is_state():
+            if event.is_state():
                 # Get previous state
                 if "replaces_state" in event.unsigned:
                     prev_id = event.unsigned["replaces_state"]
@@ -1706,8 +1713,19 @@ class FederationHandler(BaseHandler):
         defer.returnValue(context)
 
     @defer.inlineCallbacks
-    def on_query_auth(self, origin, event_id, remote_auth_chain, rejects,
+    def on_query_auth(self, origin, event_id, room_id, remote_auth_chain, rejects,
                       missing):
+        in_room = yield self.auth.check_host_in_room(
+            room_id,
+            origin
+        )
+        if not in_room:
+            raise AuthError(403, "Host not in room.")
+
+        event = yield self.store.get_event(
+            event_id, allow_none=False, check_room_id=room_id
+        )
+
         # Just go through and process each event in `remote_auth_chain`. We
         # don't want to fall into the trap of `missing` being wrong.
         for e in remote_auth_chain:
@@ -1717,7 +1735,6 @@ class FederationHandler(BaseHandler):
                 pass
 
         # Now get the current auth_chain for the event.
-        event = yield self.store.get_event(event_id)
         local_auth_chain = yield self.store.get_auth_chain(
             [auth_id for auth_id, _ in event.auth_events],
             include_given=True

synapse/storage/event_federation.py

@@ -343,6 +343,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore,
                 table="events",
                 keyvalues={
                     "event_id": event_id,
+                    "room_id": room_id,
                 },
                 retcol="depth",
                 allow_none=True,

synapse/storage/events_worker.py

@@ -19,7 +19,7 @@ from canonicaljson import json
 
 from twisted.internet import defer
 
-from synapse.api.errors import SynapseError
+from synapse.api.errors import NotFoundError
 # these are only included to make the type annotations work
 from synapse.events import EventBase  # noqa: F401
 from synapse.events import FrozenEvent
@@ -76,7 +76,7 @@ class EventsWorkerStore(SQLBaseStore):
     @defer.inlineCallbacks
     def get_event(self, event_id, check_redacted=True,
                   get_prev_content=False, allow_rejected=False,
-                  allow_none=False):
+                  allow_none=False, check_room_id=None):
         """Get an event from the database by event_id.
 
         Args:
@@ -87,7 +87,9 @@ class EventsWorkerStore(SQLBaseStore):
                 include the previous states content in the unsigned field.
             allow_rejected (bool): If True return rejected events.
             allow_none (bool): If True, return None if no event found, if
-                False throw an exception.
+                False throw a NotFoundError
+            check_room_id (str|None): if not None, check the room of the found event.
+                If there is a mismatch, behave as per allow_none.
 
         Returns:
             Deferred : A FrozenEvent.
@@ -99,10 +101,16 @@ class EventsWorkerStore(SQLBaseStore):
             allow_rejected=allow_rejected,
         )
 
-        if not events and not allow_none:
-            raise SynapseError(404, "Could not find event %s" % (event_id,))
+        event = events[0] if events else None
 
-        defer.returnValue(events[0] if events else None)
+        if event is not None and check_room_id is not None:
+            if event.room_id != check_room_id:
+                event = None
+
+        if event is None and not allow_none:
+            raise NotFoundError("Could not find event %s" % (event_id,))
+
+        defer.returnValue(event)
 
     @defer.inlineCallbacks
     def get_events(self, event_ids, check_redacted=True,