diff options
| -rw-r--r-- | synapse/events/__init__.py | 6 | ||||
| -rw-r--r-- | synapse/events/third_party_rules.py | 7 | ||||
| -rw-r--r-- | tests/rest/client/test_third_party_rules.py | 20 |
3 files changed, 30 insertions, 3 deletions
diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py index 7a51d0a22f..65df62107f 100644 --- a/synapse/events/__init__.py +++ b/synapse/events/__init__.py @@ -312,6 +312,12 @@ class EventBase(metaclass=abc.ABCMeta): """ return [e for e, _ in self.auth_events] + def freeze(self): + """'Freeze' the event dict, so it cannot be modified by accident""" + + # this will be a no-op if the event dict is already frozen. + self._dict = freeze(self._dict) + class FrozenEvent(EventBase): format_version = EventFormatVersions.V1 # All events of this type are V1 diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py index a9aabe00df..77fbd3f68a 100644 --- a/synapse/events/third_party_rules.py +++ b/synapse/events/third_party_rules.py @@ -69,9 +69,10 @@ class ThirdPartyEventRules: events = await self.store.get_events(prev_state_ids.values()) state_events = {(ev.type, ev.state_key): ev for ev in events.values()} - # The module can modify the event slightly if it wants, but caution should be - # exercised, and it's likely to go very wrong if applied to events received over - # federation. + # Ensure that the event is frozen, to make sure that the module is not tempted + # to try to modify it. Any attempt to modify it at this point will invalidate + # the hashes and signatures. + event.freeze() return await self.third_party_rules.check_event_allowed(event, state_events) diff --git a/tests/rest/client/test_third_party_rules.py b/tests/rest/client/test_third_party_rules.py index d404550800..0048bea54a 100644 --- a/tests/rest/client/test_third_party_rules.py +++ b/tests/rest/client/test_third_party_rules.py @@ -114,6 +114,26 @@ class ThirdPartyRulesTestCase(unittest.HomeserverTestCase): self.render(request) self.assertEquals(channel.result["code"], b"403", channel.result) + def test_cannot_modify_event(self): + """cannot accidentally modify an event before it is persisted""" + + # first patch the event checker so that it will try to modify the event + async def check(ev: EventBase, state): + ev.content = {"x": "y"} + return True + + current_rules_module().check_event_allowed = check + + # now send the event + request, channel = self.make_request( + "PUT", + "/_matrix/client/r0/rooms/%s/send/modifyme/1" % self.room_id, + {"x": "x"}, + access_token=self.tok, + ) + self.render(request) + self.assertEqual(channel.result["code"], b"500", channel.result) + def test_modify_event(self): """The module can return a modified version of the event""" # first patch the event checker so that it will modify the event |