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Diffstat (limited to 'synapse/state/v2.py')
| -rw-r--r-- | synapse/state/v2.py | 544 |
1 files changed, 544 insertions, 0 deletions
diff --git a/synapse/state/v2.py b/synapse/state/v2.py new file mode 100644 index 0000000000..5d06f7e928 --- /dev/null +++ b/synapse/state/v2.py @@ -0,0 +1,544 @@ +# -*- coding: utf-8 -*- +# Copyright 2018 New Vector Ltd +# +# 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. + +import heapq +import itertools +import logging + +from six import iteritems, itervalues + +from twisted.internet import defer + +from synapse import event_auth +from synapse.api.constants import EventTypes +from synapse.api.errors import AuthError + +logger = logging.getLogger(__name__) + + +@defer.inlineCallbacks +def resolve_events_with_store(state_sets, event_map, state_res_store): + """Resolves the state using the v2 state resolution algorithm + + Args: + state_sets(list): List of dicts of (type, state_key) -> event_id, + which are the different state groups to resolve. + + event_map(dict[str,FrozenEvent]|None): + a dict from event_id to event, for any events that we happen to + have in flight (eg, those currently being persisted). This will be + used as a starting point fof finding the state we need; any missing + events will be requested via state_res_store. + + If None, all events will be fetched via state_res_store. + + state_res_store (StateResolutionStore) + + Returns + Deferred[dict[(str, str), str]]: + a map from (type, state_key) to event_id. + """ + + logger.debug("Computing conflicted state") + + # First split up the un/conflicted state + unconflicted_state, conflicted_state = _seperate(state_sets) + + if not conflicted_state: + defer.returnValue(unconflicted_state) + + logger.debug("%d conflicted state entries", len(conflicted_state)) + logger.debug("Calculating auth chain difference") + + # Also fetch all auth events that appear in only some of the state sets' + # auth chains. + auth_diff = yield _get_auth_chain_difference( + state_sets, event_map, state_res_store, + ) + + full_conflicted_set = set(itertools.chain( + itertools.chain.from_iterable(itervalues(conflicted_state)), + auth_diff, + )) + + events = yield state_res_store.get_events([ + eid for eid in full_conflicted_set + if eid not in event_map + ], allow_rejected=True) + event_map.update(events) + + full_conflicted_set = set(eid for eid in full_conflicted_set if eid in event_map) + + logger.debug("%d full_conflicted_set entries", len(full_conflicted_set)) + + # Get and sort all the power events (kicks/bans/etc) + power_events = ( + eid for eid in full_conflicted_set + if _is_power_event(event_map[eid]) + ) + + sorted_power_events = yield _reverse_topological_power_sort( + power_events, + event_map, + state_res_store, + full_conflicted_set, + ) + + logger.debug("sorted %d power events", len(sorted_power_events)) + + # Now sequentially auth each one + resolved_state = yield _iterative_auth_checks( + sorted_power_events, unconflicted_state, event_map, + state_res_store, + ) + + logger.debug("resolved power events") + + # OK, so we've now resolved the power events. Now sort the remaining + # events using the mainline of the resolved power level. + + leftover_events = [ + ev_id + for ev_id in full_conflicted_set + if ev_id not in sorted_power_events + ] + + logger.debug("sorting %d remaining events", len(leftover_events)) + + pl = resolved_state.get((EventTypes.PowerLevels, ""), None) + leftover_events = yield _mainline_sort( + leftover_events, pl, event_map, state_res_store, + ) + + logger.debug("resolving remaining events") + + resolved_state = yield _iterative_auth_checks( + leftover_events, resolved_state, event_map, + state_res_store, + ) + + logger.debug("resolved") + + # We make sure that unconflicted state always still applies. + resolved_state.update(unconflicted_state) + + logger.debug("done") + + defer.returnValue(resolved_state) + + +@defer.inlineCallbacks +def _get_power_level_for_sender(event_id, event_map, state_res_store): + """Return the power level of the sender of the given event according to + their auth events. + + Args: + event_id (str) + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[int] + """ + event = yield _get_event(event_id, event_map, state_res_store) + + pl = None + for aid, _ in event.auth_events: + aev = yield _get_event(aid, event_map, state_res_store) + if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""): + pl = aev + break + + if pl is None: + # Couldn't find power level. Check if they're the creator of the room + for aid, _ in event.auth_events: + aev = yield _get_event(aid, event_map, state_res_store) + if (aev.type, aev.state_key) == (EventTypes.Create, ""): + if aev.content.get("creator") == event.sender: + defer.returnValue(100) + break + defer.returnValue(0) + + level = pl.content.get("users", {}).get(event.sender) + if level is None: + level = pl.content.get("users_default", 0) + + if level is None: + defer.returnValue(0) + else: + defer.returnValue(int(level)) + + +@defer.inlineCallbacks +def _get_auth_chain_difference(state_sets, event_map, state_res_store): + """Compare the auth chains of each state set and return the set of events + that only appear in some but not all of the auth chains. + + Args: + state_sets (list) + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[set[str]]: Set of event IDs + """ + common = set(itervalues(state_sets[0])).intersection( + *(itervalues(s) for s in state_sets[1:]) + ) + + auth_sets = [] + for state_set in state_sets: + auth_ids = set( + eid + for key, eid in iteritems(state_set) + if (key[0] in ( + EventTypes.Member, + EventTypes.ThirdPartyInvite, + ) or key in ( + (EventTypes.PowerLevels, ''), + (EventTypes.Create, ''), + (EventTypes.JoinRules, ''), + )) and eid not in common + ) + + auth_chain = yield state_res_store.get_auth_chain(auth_ids) + auth_ids.update(auth_chain) + + auth_sets.append(auth_ids) + + intersection = set(auth_sets[0]).intersection(*auth_sets[1:]) + union = set().union(*auth_sets) + + defer.returnValue(union - intersection) + + +def _seperate(state_sets): + """Return the unconflicted and conflicted state. This is different than in + the original algorithm, as this defines a key to be conflicted if one of + the state sets doesn't have that key. + + Args: + state_sets (list) + + Returns: + tuple[dict, dict]: A tuple of unconflicted and conflicted state. The + conflicted state dict is a map from type/state_key to set of event IDs + """ + unconflicted_state = {} + conflicted_state = {} + + for key in set(itertools.chain.from_iterable(state_sets)): + event_ids = set(state_set.get(key) for state_set in state_sets) + if len(event_ids) == 1: + unconflicted_state[key] = event_ids.pop() + else: + event_ids.discard(None) + conflicted_state[key] = event_ids + + return unconflicted_state, conflicted_state + + +def _is_power_event(event): + """Return whether or not the event is a "power event", as defined by the + v2 state resolution algorithm + + Args: + event (FrozenEvent) + + Returns: + boolean + """ + if (event.type, event.state_key) in ( + (EventTypes.PowerLevels, ""), + (EventTypes.JoinRules, ""), + (EventTypes.Create, ""), + ): + return True + + if event.type == EventTypes.Member: + if event.membership in ('leave', 'ban'): + return event.sender != event.state_key + + return False + + +@defer.inlineCallbacks +def _add_event_and_auth_chain_to_graph(graph, event_id, event_map, + state_res_store, auth_diff): + """Helper function for _reverse_topological_power_sort that add the event + and its auth chain (that is in the auth diff) to the graph + + Args: + graph (dict[str, set[str]]): A map from event ID to the events auth + event IDs + event_id (str): Event to add to the graph + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + auth_diff (set[str]): Set of event IDs that are in the auth difference. + """ + + state = [event_id] + while state: + eid = state.pop() + graph.setdefault(eid, set()) + + event = yield _get_event(eid, event_map, state_res_store) + for aid, _ in event.auth_events: + if aid in auth_diff: + if aid not in graph: + state.append(aid) + + graph.setdefault(eid, set()).add(aid) + + +@defer.inlineCallbacks +def _reverse_topological_power_sort(event_ids, event_map, state_res_store, auth_diff): + """Returns a list of the event_ids sorted by reverse topological ordering, + and then by power level and origin_server_ts + + Args: + event_ids (list[str]): The events to sort + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + auth_diff (set[str]): Set of event IDs that are in the auth difference. + + Returns: + Deferred[list[str]]: The sorted list + """ + + graph = {} + for event_id in event_ids: + yield _add_event_and_auth_chain_to_graph( + graph, event_id, event_map, state_res_store, auth_diff, + ) + + event_to_pl = {} + for event_id in graph: + pl = yield _get_power_level_for_sender(event_id, event_map, state_res_store) + event_to_pl[event_id] = pl + + def _get_power_order(event_id): + ev = event_map[event_id] + pl = event_to_pl[event_id] + + return -pl, ev.origin_server_ts, event_id + + # Note: graph is modified during the sort + it = lexicographical_topological_sort( + graph, + key=_get_power_order, + ) + sorted_events = list(it) + + defer.returnValue(sorted_events) + + +@defer.inlineCallbacks +def _iterative_auth_checks(event_ids, base_state, event_map, state_res_store): + """Sequentially apply auth checks to each event in given list, updating the + state as it goes along. + + Args: + event_ids (list[str]): Ordered list of events to apply auth checks to + base_state (dict[tuple[str, str], str]): The set of state to start with + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[dict[tuple[str, str], str]]: Returns the final updated state + """ + resolved_state = base_state.copy() + + for event_id in event_ids: + event = event_map[event_id] + + auth_events = {} + for aid, _ in event.auth_events: + ev = yield _get_event(aid, event_map, state_res_store) + + if ev.rejected_reason is None: + auth_events[(ev.type, ev.state_key)] = ev + + for key in event_auth.auth_types_for_event(event): + if key in resolved_state: + ev_id = resolved_state[key] + ev = yield _get_event(ev_id, event_map, state_res_store) + + if ev.rejected_reason is None: + auth_events[key] = event_map[ev_id] + + try: + event_auth.check( + event, auth_events, + do_sig_check=False, + do_size_check=False + ) + + resolved_state[(event.type, event.state_key)] = event_id + except AuthError: + pass + + defer.returnValue(resolved_state) + + +@defer.inlineCallbacks +def _mainline_sort(event_ids, resolved_power_event_id, event_map, + state_res_store): + """Returns a sorted list of event_ids sorted by mainline ordering based on + the given event resolved_power_event_id + + Args: + event_ids (list[str]): Events to sort + resolved_power_event_id (str): The final resolved power level event ID + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[list[str]]: The sorted list + """ + mainline = [] + pl = resolved_power_event_id + while pl: + mainline.append(pl) + pl_ev = yield _get_event(pl, event_map, state_res_store) + auth_events = pl_ev.auth_events + pl = None + for aid, _ in auth_events: + ev = yield _get_event(aid, event_map, state_res_store) + if (ev.type, ev.state_key) == (EventTypes.PowerLevels, ""): + pl = aid + break + + mainline_map = {ev_id: i + 1 for i, ev_id in enumerate(reversed(mainline))} + + event_ids = list(event_ids) + + order_map = {} + for ev_id in event_ids: + depth = yield _get_mainline_depth_for_event( + event_map[ev_id], mainline_map, + event_map, state_res_store, + ) + order_map[ev_id] = (depth, event_map[ev_id].origin_server_ts, ev_id) + + event_ids.sort(key=lambda ev_id: order_map[ev_id]) + + defer.returnValue(event_ids) + + +@defer.inlineCallbacks +def _get_mainline_depth_for_event(event, mainline_map, event_map, state_res_store): + """Get the mainline depths for the given event based on the mainline map + + Args: + event (FrozenEvent) + mainline_map (dict[str, int]): Map from event_id to mainline depth for + events in the mainline. + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[int] + """ + + # We do an iterative search, replacing `event with the power level in its + # auth events (if any) + while event: + depth = mainline_map.get(event.event_id) + if depth is not None: + defer.returnValue(depth) + + auth_events = event.auth_events + event = None + + for aid, _ in auth_events: + aev = yield _get_event(aid, event_map, state_res_store) + if (aev.type, aev.state_key) == (EventTypes.PowerLevels, ""): + event = aev + break + + # Didn't find a power level auth event, so we just return 0 + defer.returnValue(0) + + +@defer.inlineCallbacks +def _get_event(event_id, event_map, state_res_store): + """Helper function to look up event in event_map, falling back to looking + it up in the store + + Args: + event_id (str) + event_map (dict[str,FrozenEvent]) + state_res_store (StateResolutionStore) + + Returns: + Deferred[FrozenEvent] + """ + if event_id not in event_map: + events = yield state_res_store.get_events([event_id], allow_rejected=True) + event_map.update(events) + defer.returnValue(event_map[event_id]) + + +def lexicographical_topological_sort(graph, key): + """Performs a lexicographic reverse topological sort on the graph. + + This returns a reverse topological sort (i.e. if node A references B then B + appears before A in the sort), with ties broken lexicographically based on + return value of the `key` function. + + NOTE: `graph` is modified during the sort. + + Args: + graph (dict[str, set[str]]): A representation of the graph where each + node is a key in the dict and its value are the nodes edges. + key (func): A function that takes a node and returns a value that is + comparable and used to order nodes + + Yields: + str: The next node in the topological sort + """ + + # Note, this is basically Kahn's algorithm except we look at nodes with no + # outgoing edges, c.f. + # https://en.wikipedia.org/wiki/Topological_sorting#Kahn's_algorithm + outdegree_map = graph + reverse_graph = {} + + # Lists of nodes with zero out degree. Is actually a tuple of + # `(key(node), node)` so that sorting does the right thing + zero_outdegree = [] + + 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 |