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Fix joining rooms you have been unbanned from
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Since forever synapse did not allow you to join a room after you have
been unbanned from it over federation. This was not actually because of
the unban event not federating. Synapse simply used outdated state to
validate the join transition. This skips the validation if we are not in
the room and for that reason won't have the current room state.

Fixes matrix-org#1563

Signed-off-by: Nicolas Werner <nicolas.werner@hotmail.de>
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@deepbluev7
deepbluev7 committed Mar 25, 2023
1 parent ce00e57 commit 7bf026c
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Showing 2 changed files with 58 additions and 53 deletions.
2 changes: 1 addition & 1 deletion synapse/handlers/federation_event.py
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Original file line number Diff line number Diff line change
Expand Up @@ -583,7 +583,7 @@ async def process_remote_join(

await self._check_event_auth(origin, event, context)
if context.rejected:
raise SynapseError(400, "Join event was rejected")
raise SynapseError(403, "Join event was rejected")

# the remote server is responsible for sending our join event to the rest
# of the federation. Indeed, attempting to do so will result in problems
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109 changes: 57 additions & 52 deletions synapse/handlers/room_member.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -850,63 +850,68 @@ async def update_membership_locked(
# `is_partial_state_room` also indicates whether `partial_state_before_join` is
# partial.

# 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 = partial_state_before_join.get(
(EventTypes.Member, target.to_string())
)
if old_state_id:
old_state = await self.store.get_event(old_state_id, allow_none=True)
old_membership = old_state.content.get("membership") if old_state else None
if action == "unban" and old_membership != "ban":
raise SynapseError(
403,
"Cannot unban user who was not banned"
" (membership=%s)" % old_membership,
errcode=Codes.BAD_STATE,
)
if old_membership == "ban" and action not in ["ban", "unban", "leave"]:
raise SynapseError(
403,
"Cannot %s user who was banned" % (action,),
errcode=Codes.BAD_STATE,
)

if old_state:
same_content = content == old_state.content
same_membership = old_membership == effective_membership_state
same_sender = requester.user.to_string() == old_state.sender
if same_sender and same_membership and same_content:
# duplicate event.
# we know it was persisted, so must have a stream ordering.
assert old_state.internal_metadata.stream_ordering
return (
old_state.event_id,
old_state.internal_metadata.stream_ordering,
)
is_host_in_room = await self._is_host_in_room(partial_state_before_join)

if old_membership in ["ban", "leave"] and action == "kick":
raise AuthError(403, "The target user is not in the room")
# if we are not in the room, we won't have the current state
if is_host_in_room:
# 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 = partial_state_before_join.get(
(EventTypes.Member, target.to_string())
)

# we don't allow people to reject invites to the server notice
# room, but they can leave it once they are joined.
if (
old_membership == Membership.INVITE
and effective_membership_state == Membership.LEAVE
):
is_blocked = await self.store.is_server_notice_room(room_id)
if is_blocked:
if old_state_id:
old_state = await self.store.get_event(old_state_id, allow_none=True)
old_membership = (
old_state.content.get("membership") if old_state else None
)
if action == "unban" and old_membership != "ban":
raise SynapseError(
HTTPStatus.FORBIDDEN,
"You cannot reject this invite",
errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
403,
"Cannot unban user who was not banned"
" (membership=%s)" % old_membership,
errcode=Codes.BAD_STATE,
)
if old_membership == "ban" and action not in ["ban", "unban", "leave"]:
raise SynapseError(
403,
"Cannot %s user who was banned" % (action,),
errcode=Codes.BAD_STATE,
)
else:
if action == "kick":
raise AuthError(403, "The target user is not in the room")

is_host_in_room = await self._is_host_in_room(partial_state_before_join)
if old_state:
same_content = content == old_state.content
same_membership = old_membership == effective_membership_state
same_sender = requester.user.to_string() == old_state.sender
if same_sender and same_membership and same_content:
# duplicate event.
# we know it was persisted, so must have a stream ordering.
assert old_state.internal_metadata.stream_ordering
return (
old_state.event_id,
old_state.internal_metadata.stream_ordering,
)

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 (
old_membership == Membership.INVITE
and effective_membership_state == Membership.LEAVE
):
is_blocked = await self.store.is_server_notice_room(room_id)
if is_blocked:
raise SynapseError(
HTTPStatus.FORBIDDEN,
"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")

if effective_membership_state == Membership.JOIN:
if requester.is_guest:
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