Don't set new room alias before potential 403 (#10930)

Fixes: #10929 

Signed-off-by: Andrew Ferrazzutti <fair@miscworks.net>

1 files changed, 9 insertions, 9 deletions

diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py

index 6f39e9446f..cf01d58ea1 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -773,6 +773,15 @@ class RoomCreationHandler:
         if not allowed_by_third_party_rules:
             raise SynapseError(403, "Room visibility value not allowed.")
 
+        if is_public:
+            if not self.config.roomdirectory.is_publishing_room_allowed(
+                user_id, room_id, room_alias
+            ):
+                # Let's 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")
+
         directory_handler = self.hs.get_directory_handler()
         if room_alias:
             await directory_handler.create_association(
@@ -783,15 +792,6 @@ class RoomCreationHandler:
                 check_membership=False,
             )
 
-        if is_public:
-            if not self.config.roomdirectory.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