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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 twisted.internet import defer
class ThirdPartyEventRules(object):
"""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)
@defer.inlineCallbacks
def check_event_allowed(self, event, context):
"""Check if a provided event should be allowed in the given context.
Args:
event (synapse.events.EventBase): The event to be checked.
context (synapse.events.snapshot.EventContext): The context of the event.
Returns:
defer.Deferred(bool), True if the event should be allowed, False if not.
"""
if self.third_party_rules is None:
defer.returnValue(True)
prev_state_ids = yield context.get_prev_state_ids(self.store)
# Retrieve the state events from the database.
state_events = {}
for key, event_id in prev_state_ids.items():
state_events[key] = yield self.store.get_event(event_id, allow_none=True)
ret = yield self.third_party_rules.check_event_allowed(event, state_events)
defer.returnValue(ret)
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