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# Copyright 2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from typing import TYPE_CHECKING, Optional
from synapse.api.constants import EventTypes, JoinRules, Membership
from synapse.api.errors import AuthError
from synapse.api.room_versions import RoomVersion
from synapse.events import EventBase
from synapse.types import StateMap
if TYPE_CHECKING:
from synapse.server import HomeServer
class EventAuthHandler:
"""
This class contains methods for authenticating events added to room graphs.
"""
def __init__(self, hs: "HomeServer"):
self._store = hs.get_datastore()
async def check_restricted_join_rules(
self,
state_ids: StateMap[str],
room_version: RoomVersion,
user_id: str,
prev_member_event: Optional[EventBase],
) -> None:
"""
Check whether a user can join a room without an invite due to restricted join rules.
When joining a room with restricted joined rules (as defined in MSC3083),
the membership of spaces must be checked during a room join.
Args:
state_ids: The state of the room as it currently is.
room_version: The room version of the room being joined.
user_id: The user joining the room.
prev_member_event: The current membership event for this user.
Raises:
AuthError if the user cannot join the room.
"""
# If the member is invited or currently joined, then nothing to do.
if prev_member_event and (
prev_member_event.membership in (Membership.JOIN, Membership.INVITE)
):
return
# This only applies to room versions which support the new join rule.
if not room_version.msc3083_join_rules:
return
# If there's no join rule, then it defaults to invite (so this doesn't apply).
join_rules_event_id = state_ids.get((EventTypes.JoinRules, ""), None)
if not join_rules_event_id:
return
# If the join rule is not restricted, this doesn't apply.
join_rules_event = await self._store.get_event(join_rules_event_id)
if join_rules_event.content.get("join_rule") != JoinRules.MSC3083_RESTRICTED:
return
# If allowed is of the wrong form, then only allow invited users.
allowed_spaces = join_rules_event.content.get("allow", [])
if not isinstance(allowed_spaces, list):
allowed_spaces = ()
# Get the list of joined rooms and see if there's an overlap.
if allowed_spaces:
joined_rooms = await self._store.get_rooms_for_user(user_id)
else:
joined_rooms = ()
# Pull out the other room IDs, invalid data gets filtered.
for space in allowed_spaces:
if not isinstance(space, dict):
continue
space_id = space.get("space")
if not isinstance(space_id, str):
continue
# The user was joined to one of the spaces specified, they can join
# this room!
if space_id in joined_rooms:
return
# The user was not in any of the required spaces.
raise AuthError(
403,
"You do not belong to any of the required spaces to join this room.",
)
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