Fix errors when updating the user directory with invalid data (#8223)

changelog.d/8223.bugfix

@@ -0,0 +1 @@
+Fixes a longstanding bug where user directory updates could break when unexpected profile data was included in events.

synapse/handlers/profile.py

@@ -161,6 +161,9 @@ async def set_displayname(
                     Codes.FORBIDDEN,
                 )
 
+        if not isinstance(new_displayname, str):
+            raise SynapseError(400, "Invalid displayname")
+
         if len(new_displayname) > MAX_DISPLAYNAME_LEN:
             raise SynapseError(
                 400, "Displayname is too long (max %i)" % (MAX_DISPLAYNAME_LEN,)
@@ -235,6 +238,9 @@ async def set_avatar_url(
                     400, "Changing avatar is disabled on this server", Codes.FORBIDDEN
                 )
 
+        if not isinstance(new_avatar_url, str):
+            raise SynapseError(400, "Invalid displayname")
+
         if len(new_avatar_url) > MAX_AVATAR_URL_LEN:
             raise SynapseError(
                 400, "Avatar URL is too long (max %i)" % (MAX_AVATAR_URL_LEN,)

synapse/handlers/user_directory.py

@@ -234,7 +234,7 @@ async def _handle_deltas(self, deltas):
     async def _handle_room_publicity_change(
         self, room_id, prev_event_id, event_id, typ
     ):
-        """Handle a room having potentially changed from/to world_readable/publically
+        """Handle a room having potentially changed from/to world_readable/publicly
         joinable.
 
         Args:
@@ -388,9 +388,15 @@ async def _handle_profile_change(self, user_id, room_id, prev_event_id, event_id
 
         prev_name = prev_event.content.get("displayname")
         new_name = event.content.get("displayname")
+        # If the new name is an unexpected form, do not update the directory.
+        if not isinstance(new_name, str):
+            new_name = prev_name
 
         prev_avatar = prev_event.content.get("avatar_url")
         new_avatar = event.content.get("avatar_url")
+        # If the new avatar is an unexpected form, do not update the directory.
+        if not isinstance(new_avatar, str):
+            new_avatar = prev_avatar
 
         if prev_name != new_name or prev_avatar != new_avatar:
             await self.store.update_profile_in_user_dir(user_id, new_name, new_avatar)

synapse/storage/databases/main/user_directory.py

@@ -371,6 +371,11 @@ async def update_profile_in_user_dir(
         """
         Update or add a user's profile in the user directory.
         """
+        # If the display name or avatar URL are unexpected types, overwrite them.
+        if not isinstance(display_name, str):
+            display_name = None
+        if not isinstance(avatar_url, str):
+            avatar_url = None
 
         def _update_profile_in_user_dir_txn(txn):
             new_entry = self.db_pool.simple_upsert_txn(