Check on room creation if the user is allowed to publish the room to the room directory. (#7260)

changelog.d/7260.bugfix

@@ -0,0 +1 @@
+Fix room publish permissions not being checked on room creation.

synapse/handlers/room.py

@@ -645,6 +645,13 @@ class RoomCreationHandler(BaseHandler):
                 check_membership=False,
             )
 
+        if is_public:
+            if not self.config.is_publishing_room_allowed(user_id, room_id, room_alias):
+                # Lets just return a generic message, as there may be all sorts of
+                # reasons why we said no. TODO: Allow configurable error messages
+                # per alias creation rule?
+                raise SynapseError(403, "Not allowed to publish room")
+
         preset_config = config.get(
             "preset",
             RoomCreationPreset.PRIVATE_CHAT