From db265f064272205d1e473ee35632e3ff3846dae5 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Date: Thu, 4 Apr 2019 13:05:51 +0100
Subject: [PATCH] Prevent kicking users who aren't in the room (#4999)
Prevent kick events from succeeding if the user is not currently in the room.
---
changelog.d/4999.bugfix | 1 +
synapse/handlers/room_member.py | 9 +++++++++
2 files changed, 10 insertions(+)
create mode 100644 changelog.d/4999.bugfix
diff --git a/changelog.d/4999.bugfix b/changelog.d/4999.bugfix
new file mode 100644
index 0000000000..acbc191960
--- /dev/null
+++ b/changelog.d/4999.bugfix
@@ -0,0 +1 @@
+Prevent the ability to kick users from a room they aren't in.
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 71ce5b54e5..e432740832 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -421,6 +421,9 @@ class RoomMemberHandler(object):
room_id, latest_event_ids=latest_event_ids,
)
+ # TODO: Refactor into dictionary of explicitly allowed transitions
+ # between old and new state, with specific error messages for some
+ # transitions and generic otherwise
old_state_id = current_state_ids.get((EventTypes.Member, target.to_string()))
if old_state_id:
old_state = yield self.store.get_event(old_state_id, allow_none=True)
@@ -446,6 +449,9 @@ class RoomMemberHandler(object):
if same_sender and same_membership and same_content:
defer.returnValue(old_state)
+ if old_membership in ["ban", "leave"] and action == "kick":
+ raise AuthError(403, "The target user is not in the room")
+
# we don't allow people to reject invites to the server notice
# room, but they can leave it once they are joined.
if (
@@ -459,6 +465,9 @@ class RoomMemberHandler(object):
"You cannot reject this invite",
errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
)
+ else:
+ if action == "kick":
+ raise AuthError(403, "The target user is not in the room")
is_host_in_room = yield self._is_host_in_room(current_state_ids)
--
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