Do not assume that the contents dictionary includes history_visibility. (#8945)

2 files changed, 10 insertions, 2 deletions

diff --git a/synapse/api/auth.py b/synapse/api/auth.py

index 1951f6e178..48c4d7b0be 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -23,7 +23,7 @@ from twisted.web.server import Request
 import synapse.types
 from synapse import event_auth
 from synapse.api.auth_blocking import AuthBlocking
-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import EventTypes, HistoryVisibility, Membership
 from synapse.api.errors import (
     AuthError,
     Codes,
@@ -648,7 +648,8 @@ class Auth:
             )
             if (
                 visibility
-                and visibility.content["history_visibility"] == "world_readable"
+                and visibility.content.get("history_visibility")
+                == HistoryVisibility.WORLD_READABLE
             ):
                 return Membership.JOIN, None
             raise AuthError(
diff --git a/synapse/api/constants.py b/synapse/api/constants.py

index 592abd844b..1932df83b4 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -160,3 +160,10 @@ class RoomEncryptionAlgorithms:
 class AccountDataTypes:
     DIRECT = "m.direct"
     IGNORED_USER_LIST = "m.ignored_user_list"
+
+
+class HistoryVisibility:
+    INVITED = "invited"
+    JOINED = "joined"
+    SHARED = "shared"
+    WORLD_READABLE = "world_readable"