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Allow invites via 3pid to bypass sender sig check

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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.
This commit is contained in:
Erik Johnston 2016-09-22 10:56:53 +01:00
parent bbc0d9617f
commit 1168cbd54d
2 changed files with 22 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

17
synapse/api/auth.py
View file

@ -72,7 +72,7 @@ class Auth(object):
auth_events = { auth_events = {
(e.type, e.state_key): e for e in auth_events.values() (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): def check(self, event, auth_events, do_sig_check=True):
""" Checks if this event is correctly authed. """ Checks if this event is correctly authed.
@ -92,9 +92,21 @@ class Auth(object):
raise AuthError(500, "Event has no room_id: %s" % event) raise AuthError(500, "Event has no room_id: %s" % event)
sender_domain = get_domain_from_id(event.sender) 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 # Check the sender's domain has signed the event
if do_sig_check and not event.signatures.get(sender_domain): 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") raise AuthError(403, "Event not signed by sending server")
if auth_events is None: if auth_events is None:
@ -491,6 +503,9 @@ class Auth(object):
if not invite_event: if not invite_event:
return False return False
if invite_event.sender != event.sender:
return False
if event.user_id != invite_event.user_id: if event.user_id != invite_event.user_id:
return False return False

14
synapse/handlers/federation.py
View file

@ -1922,15 +1922,15 @@ class FederationHandler(BaseHandler):
original_invite = yield self.store.get_event( original_invite = yield self.store.get_event(
original_invite_id, allow_none=True original_invite_id, allow_none=True
) )
if not original_invite: if original_invite:
logger.info(
"Could not find invite event for third_party_invite - "
"discarding: %s" % (event_dict,)
)
return
display_name = original_invite.content["display_name"] display_name = original_invite.content["display_name"]
event_dict["content"]["third_party_invite"]["display_name"] = display_name event_dict["content"]["third_party_invite"]["display_name"] = display_name
else:
logger.info(
"Could not find invite event for third_party_invite: %r",
event_dict
)
builder = self.event_builder_factory.new(event_dict) builder = self.event_builder_factory.new(event_dict)
EventValidator().validate_new(builder) EventValidator().validate_new(builder)
message_handler = self.hs.get_handlers().message_handler message_handler = self.hs.get_handlers().message_handler