# -*- 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(room_version, state_sets, event_map, state_res_store):
"""Resolves the state using the v2 state resolution algorithm
Args:
room_version (str): The room version
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")
# We use event_map as a cache, so if its None we need to initialize it
if event_map is None:
event_map = {}
# First split up the un/conflicted state
unconflicted_state, conflicted_state = _seperate(state_sets)
if not conflicted_state:
return 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(
room_version,
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(
room_version, 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")
return 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_event_ids():
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_event_ids():
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:
return 100
break
return 0
level = pl.content.get("users", {}).get(event.sender)
if level is None:
level = pl.content.get("users_default", 0)
if level is None:
return 0
else:
return 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)
return 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_event_ids():
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)
return sorted_events
@defer.inlineCallbacks
def _iterative_auth_checks(
room_version, 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:
room_version (str)
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_event_ids():
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(
room_version,
event,
auth_events,
do_sig_check=False,
do_size_check=False,
)
resolved_state[(event.type, event.state_key)] = event_id
except AuthError:
pass
return 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_event_ids()
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])
return 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:
return depth
auth_events = event.auth_event_ids()
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
return 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)
return 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