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# -*- coding: utf-8 -*-
# Copyright 2019 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 Callable, Union
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.types import Requester, StateMap
class ThirdPartyEventRules:
"""Allows server admins to provide a Python module implementing an extra
set of rules to apply when processing events.
This is designed to help admins of closed federations with enforcing custom
behaviours.
"""
def __init__(self, hs):
self.third_party_rules = None
self.store = hs.get_datastore()
module = None
config = None
if hs.config.third_party_event_rules:
module, config = hs.config.third_party_event_rules
if module is not None:
self.third_party_rules = module(
config=config,
module_api=hs.get_module_api(),
)
async def check_event_allowed(
self, event: EventBase, context: EventContext
) -> Union[bool, dict]:
"""Check if a provided event should be allowed in the given context.
The module can return:
* True: the event is allowed.
* False: the event is not allowed, and should be rejected with M_FORBIDDEN.
* a dict: replacement event data.
Args:
event: The event to be checked.
context: The context of the event.
Returns:
The result from the ThirdPartyRules module, as above
"""
if self.third_party_rules is None:
return True
prev_state_ids = await context.get_prev_state_ids()
# Retrieve the state events from the database.
events = await self.store.get_events(prev_state_ids.values())
state_events = {(ev.type, ev.state_key): ev for ev in events.values()}
# Ensure that the event is frozen, to make sure that the module is not tempted
# to try to modify it. Any attempt to modify it at this point will invalidate
# the hashes and signatures.
event.freeze()
return await self.third_party_rules.check_event_allowed(event, state_events)
async def on_create_room(
self, requester: Requester, config: dict, is_requester_admin: bool
) -> bool:
"""Intercept requests to create room to allow, deny or update the
request config.
Args:
requester
config: The creation config from the client.
is_requester_admin: If the requester is an admin
Returns:
Whether room creation is allowed or denied.
"""
if self.third_party_rules is None:
return True
ret = await self.third_party_rules.on_create_room(
requester, config, is_requester_admin
)
return ret
async def check_threepid_can_be_invited(
self, medium: str, address: str, room_id: str
) -> bool:
"""Check if a provided 3PID can be invited in the given room.
Args:
medium: The 3PID's medium.
address: The 3PID's address.
room_id: The room we want to invite the threepid to.
Returns:
True if the 3PID can be invited, False if not.
"""
if self.third_party_rules is None:
return True
state_events = await self._get_state_map_for_room(room_id)
ret = await self.third_party_rules.check_threepid_can_be_invited(
medium, address, state_events
)
return ret
async def check_visibility_can_be_modified(
self, room_id: str, new_visibility: str
) -> bool:
"""Check if a room is allowed to be published to, or removed from, the public room
list.
Args:
room_id: The ID of the room.
new_visibility: The new visibility state. Either "public" or "private".
Returns:
True if the room's visibility can be modified, False if not.
"""
if self.third_party_rules is None:
return True
check_func = getattr(
self.third_party_rules, "check_visibility_can_be_modified", None
)
if not check_func or not isinstance(check_func, Callable):
return True
state_events = await self._get_state_map_for_room(room_id)
return await check_func(room_id, state_events, new_visibility)
async def _get_state_map_for_room(self, room_id: str) -> StateMap[EventBase]:
"""Given a room ID, return the state events of that room.
Args:
room_id: The ID of the room.
Returns:
A dict mapping (event type, state key) to state event.
"""
state_ids = await self.store.get_filtered_current_state_ids(room_id)
room_state_events = await self.store.get_events(state_ids.values())
state_events = {}
for key, event_id in state_ids.items():
state_events[key] = room_state_events[event_id]
return state_events
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