diff options
| -rw-r--r-- | synapse/events/third_party_rules.py | 12 | ||||
| -rw-r--r-- | synapse/handlers/message.py | 64 | ||||
| -rw-r--r-- | tests/rest/client/test_third_party_rules.py | 8 |
3 files changed, 75 insertions, 9 deletions
diff --git a/synapse/events/third_party_rules.py b/synapse/events/third_party_rules.py index 1535cc5339..a9aabe00df 100644 --- a/synapse/events/third_party_rules.py +++ b/synapse/events/third_party_rules.py @@ -12,7 +12,8 @@ # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. -from typing import Callable + +from typing import Callable, Union from synapse.events import EventBase from synapse.events.snapshot import EventContext @@ -44,15 +45,20 @@ class ThirdPartyEventRules: async def check_event_allowed( self, event: EventBase, context: EventContext - ) -> bool: + ) -> Union[bool, dict]: """Check if a provided event should be allowed in the given context. + The module can return: + * True: the event is allowed. + * False: the event is not allowed, and should be rejected with M_FORBIDDEN. + * a dict: replacement event data. + Args: event: The event to be checked. context: The context of the event. Returns: - True if the event should be allowed, False if not. + The result from the ThirdPartyRules module, as above """ if self.third_party_rules is None: return True diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py index 987c759791..0c6aec347e 100644 --- a/synapse/handlers/message.py +++ b/synapse/handlers/message.py @@ -795,16 +795,22 @@ class EventCreationHandler: if requester: context.app_service = requester.app_service - event_allowed = await self.third_party_event_rules.check_event_allowed( + third_party_result = await self.third_party_event_rules.check_event_allowed( event, context ) - if not event_allowed: + if not third_party_result: logger.info( "Event %s forbidden by third-party rules", event, ) raise SynapseError( 403, "This event is not allowed in this context", Codes.FORBIDDEN ) + elif isinstance(third_party_result, dict): + # the third-party rules want to replace the event. We'll need to build a new + # event. + event, context = await self._rebuild_event_after_third_party_rules( + third_party_result, event + ) self.validator.validate_new(event, self.config) @@ -1294,3 +1300,57 @@ class EventCreationHandler: room_id, ) del self._rooms_to_exclude_from_dummy_event_insertion[room_id] + + async def _rebuild_event_after_third_party_rules( + self, third_party_result: dict, original_event: EventBase + ) -> Tuple[EventBase, EventContext]: + # the third_party_event_rules want to replace the event. + # we do some basic checks, and then return the replacement event and context. + + # Construct a new EventBuilder and validate it, which helps with the + # rest of these checks. + try: + builder = self.event_builder_factory.for_room_version( + original_event.room_version, third_party_result + ) + self.validator.validate_builder(builder) + except SynapseError as e: + raise Exception( + "Third party rules module created an invalid event: " + e.msg, + ) + + immutable_fields = [ + # changing the room is going to break things: we've already checked that the + # room exists, and are holding a concurrency limiter token for that room. + # Also, we might need to use a different room version. + "room_id", + # changing the type or state key might work, but we'd need to check that the + # calling functions aren't making assumptions about them. + "type", + "state_key", + ] + + for k in immutable_fields: + if getattr(builder, k, None) != original_event.get(k): + raise Exception( + "Third party rules module created an invalid event: " + "cannot change field " + k + ) + + # check that the new sender belongs to this HS + if not self.hs.is_mine_id(builder.sender): + raise Exception( + "Third party rules module created an invalid event: " + "invalid sender " + builder.sender + ) + + # copy over the original internal metadata + for k, v in original_event.internal_metadata.get_dict().items(): + setattr(builder.internal_metadata, k, v) + + event = await builder.build(prev_event_ids=original_event.prev_event_ids()) + + # we rebuild the event context, to be on the safe side. If nothing else, + # delta_ids might need an update. + context = await self.state.compute_event_context(event) + return event, context diff --git a/tests/rest/client/test_third_party_rules.py b/tests/rest/client/test_third_party_rules.py index b737625e33..d404550800 100644 --- a/tests/rest/client/test_third_party_rules.py +++ b/tests/rest/client/test_third_party_rules.py @@ -115,12 +115,12 @@ class ThirdPartyRulesTestCase(unittest.HomeserverTestCase): self.assertEquals(channel.result["code"], b"403", channel.result) def test_modify_event(self): - """Tests that the module can successfully tweak an event before it is persisted. - """ + """The module can return a modified version of the event""" # first patch the event checker so that it will modify the event async def check(ev: EventBase, state): - ev.content = {"x": "y"} - return True + d = ev.get_dict() + d["content"] = {"x": "y"} + return d current_rules_module().check_event_allowed = check |