mirror of
https://mau.dev/maunium/synapse.git
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bc80b3f454
* Add helpers for getting prev and auth events This is in preparation for allowing the event format to change between room versions.
549 lines
17 KiB
Python
549 lines
17 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import heapq
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import itertools
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import logging
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from six import iteritems, itervalues
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from twisted.internet import defer
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from synapse import event_auth
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from synapse.api.constants import EventTypes
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from synapse.api.errors import AuthError
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logger = logging.getLogger(__name__)
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@defer.inlineCallbacks
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def resolve_events_with_store(state_sets, event_map, state_res_store):
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"""Resolves the state using the v2 state resolution algorithm
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Args:
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state_sets(list): List of dicts of (type, state_key) -> event_id,
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which are the different state groups to resolve.
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event_map(dict[str,FrozenEvent]|None):
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a dict from event_id to event, for any events that we happen to
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have in flight (eg, those currently being persisted). This will be
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used as a starting point fof finding the state we need; any missing
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events will be requested via state_res_store.
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If None, all events will be fetched via state_res_store.
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state_res_store (StateResolutionStore)
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Returns
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Deferred[dict[(str, str), str]]:
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a map from (type, state_key) to event_id.
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"""
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logger.debug("Computing conflicted state")
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# We use event_map as a cache, so if its None we need to initialize it
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if event_map is None:
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event_map = {}
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# First split up the un/conflicted state
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unconflicted_state, conflicted_state = _seperate(state_sets)
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if not conflicted_state:
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defer.returnValue(unconflicted_state)
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logger.debug("%d conflicted state entries", len(conflicted_state))
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logger.debug("Calculating auth chain difference")
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# Also fetch all auth events that appear in only some of the state sets'
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# auth chains.
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auth_diff = yield _get_auth_chain_difference(
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state_sets, event_map, state_res_store,
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)
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full_conflicted_set = set(itertools.chain(
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itertools.chain.from_iterable(itervalues(conflicted_state)),
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auth_diff,
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))
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events = yield state_res_store.get_events([
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eid for eid in full_conflicted_set
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if eid not in event_map
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], allow_rejected=True)
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event_map.update(events)
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full_conflicted_set = set(eid for eid in full_conflicted_set if eid in event_map)
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logger.debug("%d full_conflicted_set entries", len(full_conflicted_set))
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# Get and sort all the power events (kicks/bans/etc)
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power_events = (
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eid for eid in full_conflicted_set
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if _is_power_event(event_map[eid])
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)
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sorted_power_events = yield _reverse_topological_power_sort(
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power_events,
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event_map,
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state_res_store,
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full_conflicted_set,
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)
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logger.debug("sorted %d power events", len(sorted_power_events))
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# Now sequentially auth each one
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resolved_state = yield _iterative_auth_checks(
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sorted_power_events, unconflicted_state, event_map,
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state_res_store,
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)
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logger.debug("resolved power events")
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# OK, so we've now resolved the power events. Now sort the remaining
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# events using the mainline of the resolved power level.
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leftover_events = [
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ev_id
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for ev_id in full_conflicted_set
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if ev_id not in sorted_power_events
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]
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logger.debug("sorting %d remaining events", len(leftover_events))
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pl = resolved_state.get((EventTypes.PowerLevels, ""), None)
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leftover_events = yield _mainline_sort(
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leftover_events, pl, event_map, state_res_store,
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)
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logger.debug("resolving remaining events")
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resolved_state = yield _iterative_auth_checks(
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leftover_events, resolved_state, event_map,
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state_res_store,
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)
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logger.debug("resolved")
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# We make sure that unconflicted state always still applies.
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resolved_state.update(unconflicted_state)
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logger.debug("done")
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defer.returnValue(resolved_state)
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@defer.inlineCallbacks
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def _get_power_level_for_sender(event_id, event_map, state_res_store):
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"""Return the power level of the sender of the given event according to
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their auth events.
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Args:
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event_id (str)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[int]
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"""
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event = yield _get_event(event_id, event_map, state_res_store)
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pl = None
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for aid in event.auth_event_ids():
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""):
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pl = aev
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break
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if pl is None:
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# Couldn't find power level. Check if they're the creator of the room
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for aid in event.auth_event_ids():
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.Create, ""):
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if aev.content.get("creator") == event.sender:
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defer.returnValue(100)
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break
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defer.returnValue(0)
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level = pl.content.get("users", {}).get(event.sender)
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if level is None:
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level = pl.content.get("users_default", 0)
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if level is None:
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defer.returnValue(0)
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else:
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defer.returnValue(int(level))
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@defer.inlineCallbacks
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def _get_auth_chain_difference(state_sets, event_map, state_res_store):
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"""Compare the auth chains of each state set and return the set of events
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that only appear in some but not all of the auth chains.
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Args:
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state_sets (list)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[set[str]]: Set of event IDs
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"""
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common = set(itervalues(state_sets[0])).intersection(
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*(itervalues(s) for s in state_sets[1:])
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)
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auth_sets = []
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for state_set in state_sets:
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auth_ids = set(
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eid
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for key, eid in iteritems(state_set)
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if (key[0] in (
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EventTypes.Member,
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EventTypes.ThirdPartyInvite,
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) or key in (
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(EventTypes.PowerLevels, ''),
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(EventTypes.Create, ''),
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(EventTypes.JoinRules, ''),
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)) and eid not in common
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)
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auth_chain = yield state_res_store.get_auth_chain(auth_ids)
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auth_ids.update(auth_chain)
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auth_sets.append(auth_ids)
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intersection = set(auth_sets[0]).intersection(*auth_sets[1:])
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union = set().union(*auth_sets)
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defer.returnValue(union - intersection)
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def _seperate(state_sets):
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"""Return the unconflicted and conflicted state. This is different than in
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the original algorithm, as this defines a key to be conflicted if one of
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the state sets doesn't have that key.
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Args:
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state_sets (list)
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Returns:
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tuple[dict, dict]: A tuple of unconflicted and conflicted state. The
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conflicted state dict is a map from type/state_key to set of event IDs
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"""
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unconflicted_state = {}
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conflicted_state = {}
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for key in set(itertools.chain.from_iterable(state_sets)):
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event_ids = set(state_set.get(key) for state_set in state_sets)
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if len(event_ids) == 1:
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unconflicted_state[key] = event_ids.pop()
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else:
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event_ids.discard(None)
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conflicted_state[key] = event_ids
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return unconflicted_state, conflicted_state
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def _is_power_event(event):
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"""Return whether or not the event is a "power event", as defined by the
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v2 state resolution algorithm
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Args:
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event (FrozenEvent)
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Returns:
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boolean
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"""
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if (event.type, event.state_key) in (
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(EventTypes.PowerLevels, ""),
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(EventTypes.JoinRules, ""),
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(EventTypes.Create, ""),
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):
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return True
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if event.type == EventTypes.Member:
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if event.membership in ('leave', 'ban'):
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return event.sender != event.state_key
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return False
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@defer.inlineCallbacks
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def _add_event_and_auth_chain_to_graph(graph, event_id, event_map,
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state_res_store, auth_diff):
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"""Helper function for _reverse_topological_power_sort that add the event
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and its auth chain (that is in the auth diff) to the graph
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Args:
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graph (dict[str, set[str]]): A map from event ID to the events auth
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event IDs
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event_id (str): Event to add to the graph
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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auth_diff (set[str]): Set of event IDs that are in the auth difference.
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"""
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state = [event_id]
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while state:
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eid = state.pop()
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graph.setdefault(eid, set())
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event = yield _get_event(eid, event_map, state_res_store)
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for aid in event.auth_event_ids():
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if aid in auth_diff:
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if aid not in graph:
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state.append(aid)
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graph.setdefault(eid, set()).add(aid)
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@defer.inlineCallbacks
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def _reverse_topological_power_sort(event_ids, event_map, state_res_store, auth_diff):
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"""Returns a list of the event_ids sorted by reverse topological ordering,
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and then by power level and origin_server_ts
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Args:
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event_ids (list[str]): The events to sort
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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auth_diff (set[str]): Set of event IDs that are in the auth difference.
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Returns:
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Deferred[list[str]]: The sorted list
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"""
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graph = {}
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for event_id in event_ids:
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yield _add_event_and_auth_chain_to_graph(
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graph, event_id, event_map, state_res_store, auth_diff,
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)
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event_to_pl = {}
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for event_id in graph:
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pl = yield _get_power_level_for_sender(event_id, event_map, state_res_store)
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event_to_pl[event_id] = pl
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def _get_power_order(event_id):
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ev = event_map[event_id]
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pl = event_to_pl[event_id]
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return -pl, ev.origin_server_ts, event_id
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# Note: graph is modified during the sort
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it = lexicographical_topological_sort(
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graph,
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key=_get_power_order,
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)
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sorted_events = list(it)
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defer.returnValue(sorted_events)
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@defer.inlineCallbacks
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def _iterative_auth_checks(event_ids, base_state, event_map, state_res_store):
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"""Sequentially apply auth checks to each event in given list, updating the
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state as it goes along.
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Args:
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event_ids (list[str]): Ordered list of events to apply auth checks to
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base_state (dict[tuple[str, str], str]): The set of state to start with
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[dict[tuple[str, str], str]]: Returns the final updated state
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"""
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resolved_state = base_state.copy()
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for event_id in event_ids:
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event = event_map[event_id]
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auth_events = {}
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for aid in event.auth_event_ids():
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ev = yield _get_event(aid, event_map, state_res_store)
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if ev.rejected_reason is None:
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auth_events[(ev.type, ev.state_key)] = ev
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for key in event_auth.auth_types_for_event(event):
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if key in resolved_state:
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ev_id = resolved_state[key]
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ev = yield _get_event(ev_id, event_map, state_res_store)
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if ev.rejected_reason is None:
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auth_events[key] = event_map[ev_id]
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try:
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event_auth.check(
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event, auth_events,
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do_sig_check=False,
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do_size_check=False
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)
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resolved_state[(event.type, event.state_key)] = event_id
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except AuthError:
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pass
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defer.returnValue(resolved_state)
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@defer.inlineCallbacks
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def _mainline_sort(event_ids, resolved_power_event_id, event_map,
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state_res_store):
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"""Returns a sorted list of event_ids sorted by mainline ordering based on
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the given event resolved_power_event_id
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Args:
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event_ids (list[str]): Events to sort
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resolved_power_event_id (str): The final resolved power level event ID
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[list[str]]: The sorted list
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"""
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mainline = []
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pl = resolved_power_event_id
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while pl:
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mainline.append(pl)
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pl_ev = yield _get_event(pl, event_map, state_res_store)
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auth_events = pl_ev.auth_event_ids()
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pl = None
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for aid in auth_events:
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ev = yield _get_event(aid, event_map, state_res_store)
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if (ev.type, ev.state_key) == (EventTypes.PowerLevels, ""):
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pl = aid
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break
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mainline_map = {ev_id: i + 1 for i, ev_id in enumerate(reversed(mainline))}
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event_ids = list(event_ids)
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order_map = {}
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for ev_id in event_ids:
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depth = yield _get_mainline_depth_for_event(
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event_map[ev_id], mainline_map,
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event_map, state_res_store,
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)
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order_map[ev_id] = (depth, event_map[ev_id].origin_server_ts, ev_id)
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event_ids.sort(key=lambda ev_id: order_map[ev_id])
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defer.returnValue(event_ids)
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@defer.inlineCallbacks
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def _get_mainline_depth_for_event(event, mainline_map, event_map, state_res_store):
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"""Get the mainline depths for the given event based on the mainline map
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Args:
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event (FrozenEvent)
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mainline_map (dict[str, int]): Map from event_id to mainline depth for
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events in the mainline.
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[int]
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"""
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# We do an iterative search, replacing `event with the power level in its
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# auth events (if any)
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while event:
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depth = mainline_map.get(event.event_id)
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if depth is not None:
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defer.returnValue(depth)
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auth_events = event.auth_event_ids()
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event = None
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for aid in auth_events:
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aev = yield _get_event(aid, event_map, state_res_store)
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if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""):
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event = aev
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break
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# Didn't find a power level auth event, so we just return 0
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defer.returnValue(0)
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@defer.inlineCallbacks
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def _get_event(event_id, event_map, state_res_store):
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"""Helper function to look up event in event_map, falling back to looking
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it up in the store
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Args:
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event_id (str)
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event_map (dict[str,FrozenEvent])
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state_res_store (StateResolutionStore)
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Returns:
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Deferred[FrozenEvent]
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"""
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if event_id not in event_map:
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events = yield state_res_store.get_events([event_id], allow_rejected=True)
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event_map.update(events)
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defer.returnValue(event_map[event_id])
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def lexicographical_topological_sort(graph, key):
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"""Performs a lexicographic reverse topological sort on the graph.
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This returns a reverse topological sort (i.e. if node A references B then B
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appears before A in the sort), with ties broken lexicographically based on
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return value of the `key` function.
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NOTE: `graph` is modified during the sort.
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Args:
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graph (dict[str, set[str]]): A representation of the graph where each
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node is a key in the dict and its value are the nodes edges.
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key (func): A function that takes a node and returns a value that is
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comparable and used to order nodes
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Yields:
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str: The next node in the topological sort
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"""
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# Note, this is basically Kahn's algorithm except we look at nodes with no
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# outgoing edges, c.f.
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# https://en.wikipedia.org/wiki/Topological_sorting#Kahn's_algorithm
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outdegree_map = graph
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reverse_graph = {}
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# Lists of nodes with zero out degree. Is actually a tuple of
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# `(key(node), node)` so that sorting does the right thing
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zero_outdegree = []
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for node, edges in iteritems(graph):
|
|
if len(edges) == 0:
|
|
zero_outdegree.append((key(node), node))
|
|
|
|
reverse_graph.setdefault(node, set())
|
|
for edge in edges:
|
|
reverse_graph.setdefault(edge, set()).add(node)
|
|
|
|
# heapq is a built in implementation of a sorted queue.
|
|
heapq.heapify(zero_outdegree)
|
|
|
|
while zero_outdegree:
|
|
_, node = heapq.heappop(zero_outdegree)
|
|
|
|
for parent in reverse_graph[node]:
|
|
out = outdegree_map[parent]
|
|
out.discard(node)
|
|
if len(out) == 0:
|
|
heapq.heappush(zero_outdegree, (key(parent), parent))
|
|
|
|
yield node
|