Add user_may_join_room spam check

synapse/events/spamcheck.py

@@ -122,3 +122,21 @@ class SpamChecker(object):
             return True
 
         return self.spam_checker.user_may_publish_room(userid, room_id)
+
+    def user_may_join_room(self, userid, room_id, is_invited):
+        """Checks if a given users is allowed to join a room.
+
+        Is not called when the user creates a room.
+
+        Args:
+            userid (str)
+            room_id (str)
+            is_invited (bool): Whether the user is invited into the room
+
+        Returns:
+            bool: Whether the user may join the room
+        """
+        if self.spam_checker is None:
+            return True
+
+        return self.spam_checker.user_may_join_room(userid, room_id, is_invited)

synapse/handlers/room_member.py

@@ -487,8 +487,19 @@ class RoomMemberHandler(object):
                     # so don't really fit into the general auth process.
                     raise AuthError(403, "Guest access not allowed")
 
+            inviter = yield self._get_inviter(target.to_string(), room_id)
+            # We assume that if the spam checker allowed the user to create
+            # a room then they're allowed to join it.
+            if not new_room and not self.spam_checker.user_may_join_room(
+                target.to_string(), room_id,
+                is_invited=inviter is not None,
+                new_room=new_room,
+            ):
+                raise SynapseError(
+                    403, "Not allowed to join this room",
+                )
+
             if not is_host_in_room:
-                inviter = yield self._get_inviter(target.to_string(), room_id)
                 if inviter and not self.hs.is_mine(inviter):
                     remote_room_hosts.append(inviter.domain)
 

synapse/rulecheck/domain_rule_checker.py

@@ -75,6 +75,11 @@ class DomainRuleChecker(object):
         """
         return True
 
+    def user_may_join_room(self, userid, room_id, is_invited, new_room):
+        """Implements synapse.events.SpamChecker.user_may_join_room
+        """
+        return True
+
     @staticmethod
     def parse_config(config):
         """Implements synapse.events.SpamChecker.parse_config