1 files changed, 7 insertions, 2 deletions
diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index efc926d094..c3c776a9f9 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -271,6 +271,7 @@ class Auth:
         app_service = self.store.get_app_service_by_token(
             self.get_access_token_from_request(request)
         )
+
         if app_service is None:
             return None, None
 
@@ -291,8 +292,12 @@ class Auth:
 
         if not app_service.is_interested_in_user(user_id):
             raise AuthError(403, "Application service cannot masquerade as this user.")
-        if not (await self.store.get_user_by_id(user_id)):
-            raise AuthError(403, "Application service has not registered this user")
+        # Let ASes manipulate nonexistent users (e.g. to shadow-register them)
+        # if not (yield self.store.get_user_by_id(user_id)):
+        #     raise AuthError(
+        #         403,
+        #         "Application service has not registered this user"
+        #     )
         return user_id, app_service
 
     async def get_user_by_access_token(