From 1473058b5eb14b5128c0b6ee6e88e89602ad96c5 Mon Sep 17 00:00:00 2001 From: Brendan Abolivier Date: Wed, 8 May 2019 17:01:30 +0100 Subject: Do checks on aliases for incoming m.room.aliases events (#5128) Follow-up to #5124 Also added a bunch of checks to make sure everything (both the stuff added on #5124 and this PR) works as intended. --- synapse/handlers/message.py | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) (limited to 'synapse/handlers/message.py') diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py index 224d34ef3a..e5afeadf68 100644 --- a/synapse/handlers/message.py +++ b/synapse/handlers/message.py @@ -228,6 +228,7 @@ class EventCreationHandler(object): self.ratelimiter = hs.get_ratelimiter() self.notifier = hs.get_notifier() self.config = hs.config + self.require_membership_for_aliases = hs.config.require_membership_for_aliases self.send_event_to_master = ReplicationSendEventRestServlet.make_client(hs) @@ -336,6 +337,35 @@ class EventCreationHandler(object): prev_events_and_hashes=prev_events_and_hashes, ) + # In an ideal world we wouldn't need the second part of this condition. However, + # this behaviour isn't spec'd yet, meaning we should be able to deactivate this + # behaviour. Another reason is that this code is also evaluated each time a new + # m.room.aliases event is created, which includes hitting a /directory route. + # Therefore not including this condition here would render the similar one in + # synapse.handlers.directory pointless. + if builder.type == EventTypes.Aliases and self.require_membership_for_aliases: + # Ideally we'd do the membership check in event_auth.check(), which + # describes a spec'd algorithm for authenticating events received over + # federation as well as those created locally. As of room v3, aliases events + # can be created by users that are not in the room, therefore we have to + # tolerate them in event_auth.check(). + prev_state_ids = yield context.get_prev_state_ids(self.store) + prev_event_id = prev_state_ids.get((EventTypes.Member, event.sender)) + prev_event = yield self.store.get_event(prev_event_id, allow_none=True) + if not prev_event or prev_event.membership != Membership.JOIN: + logger.warning( + ("Attempt to send `m.room.aliases` in room %s by user %s but" + " membership is %s"), + event.room_id, + event.sender, + prev_event.membership if prev_event else None, + ) + + raise AuthError( + 403, + "You must be in the room to create an alias for it", + ) + self.validator.validate_new(event) defer.returnValue((event, context)) -- cgit 1.4.1