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Check for space membership during a remote join of a restricted room (#9814) 

When receiving a /send_join request for a room with join rules set to 'restricted',
check if the user is a member of the spaces defined in the 'allow' key of the join rules.

This only applies to an experimental room version, as defined in MSC3083.
This commit is contained in:
Patrick Cloke 2021-04-23 07:05:51 -04:00 committed by GitHub
parent 3853a7edfc
commit d924827da1
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6 changed files with 131 additions and 68 deletions
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1
changelog.d/9814.feature Normal file
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@ -0,0 +1 @@
Update experimental support for [MSC3083](https://github.com/matrix-org/matrix-doc/pull/3083): restricting room access via group membership.

1
synapse/api/auth.py
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@ -65,6 +65,7 @@ class Auth:
"""
FIXME: This class contains a mix of functions for authenticating users
of our client-server API and authenticating events added to room graphs.
The latter should be moved to synapse.handlers.event_auth.EventAuthHandler.
"""
def __init__(self, hs):

86
synapse/handlers/event_auth.py Normal file
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@ -0,0 +1,86 @@
# 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
from synapse.api.constants import EventTypes, JoinRules
from synapse.api.room_versions import RoomVersion
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 can_join_without_invite(
self, state_ids: StateMap[str], room_version: RoomVersion, user_id: str
) -> bool:
"""
Check whether a user can join a room without an invite.
When joining a room with restricted joined rules (as defined in MSC3083),
the membership of spaces must be checked during 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.
Returns:
True if the user can join the room, false otherwise.
"""
# This only applies to room versions which support the new join rule.
if not room_version.msc3083_join_rules:
return True
# 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 True
# 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 True
# 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):
return False
# Get the list of joined rooms and see if there's an overlap.
joined_rooms = await self._store.get_rooms_for_user(user_id)
# 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 True
# The user was not in any of the required spaces.
return False

44
synapse/handlers/federation.py
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@ -146,6 +146,7 @@ class FederationHandler(BaseHandler):
self.is_mine_id = hs.is_mine_id
self.spam_checker = hs.get_spam_checker()
self.event_creation_handler = hs.get_event_creation_handler()
self._event_auth_handler = hs.get_event_auth_handler()
self._message_handler = hs.get_message_handler()
self._server_notices_mxid = hs.config.server_notices_mxid
self.config = hs.config
@ -1673,8 +1674,40 @@ class FederationHandler(BaseHandler):
# would introduce the danger of backwards-compatibility problems.
event.internal_metadata.send_on_behalf_of = origin
# Calculate the event context.
context = await self.state_handler.compute_event_context(event)
context = await self._auth_and_persist_event(origin, event, context)
# Get the state before the new event.
prev_state_ids = await context.get_prev_state_ids()
# Check if the user is already in the room or invited to the room.
user_id = event.state_key
prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)
newly_joined = True
user_is_invited = False
if prev_member_event_id:
prev_member_event = await self.store.get_event(prev_member_event_id)
newly_joined = prev_member_event.membership != Membership.JOIN
user_is_invited = prev_member_event.membership == Membership.INVITE
# If the member is not already in the room, and not invited, check if
# they should be allowed access via membership in a space.
if (
newly_joined
and not user_is_invited
and not await self._event_auth_handler.can_join_without_invite(
prev_state_ids,
event.room_version,
user_id,
)
):
raise AuthError(
403,
"You do not belong to any of the required spaces to join this room.",
)
# Persist the event.
await self._auth_and_persist_event(origin, event, context)
logger.debug(
"on_send_join_request: After _auth_and_persist_event: %s, sigs: %s",
@ -1682,8 +1715,6 @@ class FederationHandler(BaseHandler):
event.signatures,
)
prev_state_ids = await context.get_prev_state_ids()
state_ids = list(prev_state_ids.values())
auth_chain = await self.store.get_auth_chain(event.room_id, state_ids)
@ -2006,7 +2037,7 @@ class FederationHandler(BaseHandler):
state: Optional[Iterable[EventBase]] = None,
auth_events: Optional[MutableStateMap[EventBase]] = None,
backfilled: bool = False,
) -> EventContext:
) -> None:
"""
Process an event by performing auth checks and then persisting to the database.
@ -2028,9 +2059,6 @@ class FederationHandler(BaseHandler):
event is an outlier), may be the auth events claimed by the remote
server.
backfilled: True if the event was backfilled.
Returns:
The event context.
"""
context = await self._check_event_auth(
origin,
@ -2060,8 +2088,6 @@ class FederationHandler(BaseHandler):
)
raise
return context
async def _auth_and_persist_events(
self,
origin: str,

62
synapse/handlers/room_member.py
View File

@ -19,7 +19,7 @@ from http import HTTPStatus
from typing import TYPE_CHECKING, Iterable, List, Optional, Tuple
from synapse import types
from synapse.api.constants import AccountDataTypes, EventTypes, JoinRules, Membership
from synapse.api.constants import AccountDataTypes, EventTypes, Membership
from synapse.api.errors import (
AuthError,
Codes,
@ -28,7 +28,6 @@ from synapse.api.errors import (
SynapseError,
)
from synapse.api.ratelimiting import Ratelimiter
from synapse.api.room_versions import RoomVersion
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.types import JsonDict, Requester, RoomAlias, RoomID, StateMap, UserID
@ -64,6 +63,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
self.profile_handler = hs.get_profile_handler()
self.event_creation_handler = hs.get_event_creation_handler()
self.account_data_handler = hs.get_account_data_handler()
self.event_auth_handler = hs.get_event_auth_handler()
self.member_linearizer = Linearizer(name="member")
@ -178,62 +178,6 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
await self._invites_per_user_limiter.ratelimit(requester, invitee_user_id)
async def _can_join_without_invite(
self, state_ids: StateMap[str], room_version: RoomVersion, user_id: str
) -> bool:
"""
Check whether a user can join a room without an invite.
When joining a room with restricted joined rules (as defined in MSC3083),
the membership of spaces must be checked during 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.
Returns:
True if the user can join the room, false otherwise.
"""
# This only applies to room versions which support the new join rule.
if not room_version.msc3083_join_rules:
return True
# If there's no join rule, then it defaults to public (so this doesn't apply).
join_rules_event_id = state_ids.get((EventTypes.JoinRules, ""), None)
if not join_rules_event_id:
return True
# 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 True
# 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):
return False
# Get the list of joined rooms and see if there's an overlap.
joined_rooms = await self.store.get_rooms_for_user(user_id)
# 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 True
# The user was not in any of the required spaces.
return False
async def _local_membership_update(
self,
requester: Requester,
@ -302,7 +246,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
if (
newly_joined
and not user_is_invited
and not await self._can_join_without_invite(
and not await self.event_auth_handler.can_join_without_invite(
prev_state_ids, event.room_version, user_id
)
):

5
synapse/server.py
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@ -77,6 +77,7 @@ from synapse.handlers.devicemessage import DeviceMessageHandler
from synapse.handlers.directory import DirectoryHandler
from synapse.handlers.e2e_keys import E2eKeysHandler
from synapse.handlers.e2e_room_keys import E2eRoomKeysHandler
from synapse.handlers.event_auth import EventAuthHandler
from synapse.handlers.events import EventHandler, EventStreamHandler
from synapse.handlers.federation import FederationHandler
from synapse.handlers.groups_local import GroupsLocalHandler, GroupsLocalWorkerHandler
@ -746,6 +747,10 @@ class HomeServer(metaclass=abc.ABCMeta):
def get_space_summary_handler(self) -> SpaceSummaryHandler:
return SpaceSummaryHandler(self)
@cache_in_self
def get_event_auth_handler(self) -> EventAuthHandler:
return EventAuthHandler(self)
@cache_in_self
def get_external_cache(self) -> ExternalCache:
return ExternalCache(self)