From 1168cbd54db059cefdf968077f6b14163de6c04c Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Thu, 22 Sep 2016 10:56:53 +0100 Subject: [PATCH] Allow invites via 3pid to bypass sender sig check When a server sends a third party invite another server may be the one that the inviting user registers with. In this case it is that remote server that will issue an actual invitation, and wants to do it "in the name of" the original invitee. However, the new proper invite will not be signed by the original server, and thus other servers would reject the invite if it was seen as coming from the original user. To fix this, a special case has been added to the auth rules whereby another server can send an invite "in the name of" another server's user, so long as that user had previously issued a third party invite that is now being accepted. --- synapse/api/auth.py | 17 ++++++++++++++++- synapse/handlers/federation.py | 12 ++++++------ 2 files changed, 22 insertions(+), 7 deletions(-) diff --git a/synapse/api/auth.py b/synapse/api/auth.py index 98a50f0948..d60c1b15ae 100644 --- a/synapse/api/auth.py +++ b/synapse/api/auth.py @@ -72,7 +72,7 @@ class Auth(object): auth_events = { (e.type, e.state_key): e for e in auth_events.values() } - self.check(event, auth_events=auth_events, do_sig_check=False) + self.check(event, auth_events=auth_events, do_sig_check=do_sig_check) def check(self, event, auth_events, do_sig_check=True): """ Checks if this event is correctly authed. @@ -92,9 +92,21 @@ class Auth(object): raise AuthError(500, "Event has no room_id: %s" % event) sender_domain = get_domain_from_id(event.sender) + event_id_domain = get_domain_from_id(event.event_id) + + is_invite_via_3pid = ( + event.type == EventTypes.Member + and event.membership == Membership.INVITE + and "third_party_invite" in event.content + ) # Check the sender's domain has signed the event if do_sig_check and not event.signatures.get(sender_domain): + if not is_invite_via_3pid: + raise AuthError(403, "Event not signed by sender's server") + + # Check the event_id's domain has signed the event + if do_sig_check and not event.signatures.get(event_id_domain): raise AuthError(403, "Event not signed by sending server") if auth_events is None: @@ -491,6 +503,9 @@ class Auth(object): if not invite_event: return False + if invite_event.sender != event.sender: + return False + if event.user_id != invite_event.user_id: return False diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index f7cb3c1bb2..a393263e1e 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -1922,15 +1922,15 @@ class FederationHandler(BaseHandler): original_invite = yield self.store.get_event( original_invite_id, allow_none=True ) - if not original_invite: + if original_invite: + display_name = original_invite.content["display_name"] + event_dict["content"]["third_party_invite"]["display_name"] = display_name + else: logger.info( - "Could not find invite event for third_party_invite - " - "discarding: %s" % (event_dict,) + "Could not find invite event for third_party_invite: %r", + event_dict ) - return - display_name = original_invite.content["display_name"] - event_dict["content"]["third_party_invite"]["display_name"] = display_name builder = self.event_builder_factory.new(event_dict) EventValidator().validate_new(builder) message_handler = self.hs.get_handlers().message_handler