Do not assume that account data is of the correct form. (#8454)

This fixes a bug where `m.ignored_user_list` was assumed to be a dict,
leading to odd behavior for users who set it to something else.

1 files changed, 7 insertions, 2 deletions

diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
index ef81d73573..49ee23470d 100644
--- a/synapse/storage/databases/main/account_data.py
+++ b/synapse/storage/databases/main/account_data.py
@@ -18,6 +18,7 @@ import abc
 import logging
 from typing import Dict, List, Optional, Tuple
 
+from synapse.api.constants import AccountDataTypes
 from synapse.storage._base import SQLBaseStore, db_to_json
 from synapse.storage.database import DatabasePool
 from synapse.storage.util.id_generators import StreamIdGenerator
@@ -291,14 +292,18 @@ class AccountDataWorkerStore(SQLBaseStore, metaclass=abc.ABCMeta):
         self, ignored_user_id: str, ignorer_user_id: str, cache_context: _CacheContext
     ) -> bool:
         ignored_account_data = await self.get_global_account_data_by_type_for_user(
-            "m.ignored_user_list",
+            AccountDataTypes.IGNORED_USER_LIST,
             ignorer_user_id,
             on_invalidate=cache_context.invalidate,
         )
         if not ignored_account_data:
             return False
 
-        return ignored_user_id in ignored_account_data.get("ignored_users", {})
+        try:
+            return ignored_user_id in ignored_account_data.get("ignored_users", {})
+        except TypeError:
+            # The type of the ignored_users field is invalid.
+            return False
 
 
 class AccountDataStore(AccountDataWorkerStore):