From 1473058b5eb14b5128c0b6ee6e88e89602ad96c5 Mon Sep 17 00:00:00 2001 From: Brendan Abolivier Date: Wed, 8 May 2019 17:01:30 +0100 Subject: Do checks on aliases for incoming m.room.aliases events (#5128) Follow-up to #5124 Also added a bunch of checks to make sure everything (both the stuff added on #5124 and this PR) works as intended. --- synapse/api/constants.py | 3 +++ synapse/events/snapshot.py | 8 ++++++-- synapse/events/validator.py | 15 +++++++++++++-- synapse/handlers/directory.py | 7 +++---- synapse/handlers/message.py | 30 ++++++++++++++++++++++++++++++ 5 files changed, 55 insertions(+), 8 deletions(-) (limited to 'synapse') diff --git a/synapse/api/constants.py b/synapse/api/constants.py index 0860b75905..8547a63535 100644 --- a/synapse/api/constants.py +++ b/synapse/api/constants.py @@ -20,6 +20,9 @@ # the "depth" field on events is limited to 2**63 - 1 MAX_DEPTH = 2**63 - 1 +# the maximum length for a room alias is 255 characters +MAX_ALIAS_LENGTH = 255 + class Membership(object): diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py index 368b5f6ae4..fa09c132a0 100644 --- a/synapse/events/snapshot.py +++ b/synapse/events/snapshot.py @@ -187,7 +187,9 @@ class EventContext(object): Returns: Deferred[dict[(str, str), str]|None]: Returns None if state_group - is None, which happens when the associated event is an outlier. + is None, which happens when the associated event is an outlier. + Maps a (type, state_key) to the event ID of the state event matching + this tuple. """ if not self._fetching_state_deferred: @@ -205,7 +207,9 @@ class EventContext(object): Returns: Deferred[dict[(str, str), str]|None]: Returns None if state_group - is None, which happens when the associated event is an outlier. + is None, which happens when the associated event is an outlier. + Maps a (type, state_key) to the event ID of the state event matching + this tuple. """ if not self._fetching_state_deferred: diff --git a/synapse/events/validator.py b/synapse/events/validator.py index 514273c792..711af512b2 100644 --- a/synapse/events/validator.py +++ b/synapse/events/validator.py @@ -15,8 +15,8 @@ from six import string_types -from synapse.api.constants import EventTypes, Membership -from synapse.api.errors import SynapseError +from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes, Membership +from synapse.api.errors import Codes, SynapseError from synapse.api.room_versions import EventFormatVersions from synapse.types import EventID, RoomID, UserID @@ -56,6 +56,17 @@ class EventValidator(object): if not isinstance(getattr(event, s), string_types): raise SynapseError(400, "'%s' not a string type" % (s,)) + if event.type == EventTypes.Aliases: + if "aliases" in event.content: + for alias in event.content["aliases"]: + if len(alias) > MAX_ALIAS_LENGTH: + raise SynapseError( + 400, + ("Can't create aliases longer than" + " %d characters" % (MAX_ALIAS_LENGTH,)), + Codes.INVALID_PARAM, + ) + def validate_builder(self, event): """Validates that the builder/event has roughly the right format. Only checks values that we expect a proto event to have, rather than all the diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py index 50c587aa61..a12f9508d8 100644 --- a/synapse/handlers/directory.py +++ b/synapse/handlers/directory.py @@ -19,7 +19,7 @@ import string from twisted.internet import defer -from synapse.api.constants import EventTypes +from synapse.api.constants import MAX_ALIAS_LENGTH, EventTypes from synapse.api.errors import ( AuthError, CodeMessageException, @@ -36,7 +36,6 @@ logger = logging.getLogger(__name__) class DirectoryHandler(BaseHandler): - MAX_ALIAS_LENGTH = 255 def __init__(self, hs): super(DirectoryHandler, self).__init__(hs) @@ -105,10 +104,10 @@ class DirectoryHandler(BaseHandler): user_id = requester.user.to_string() - if len(room_alias.to_string()) > self.MAX_ALIAS_LENGTH: + if len(room_alias.to_string()) > MAX_ALIAS_LENGTH: raise SynapseError( 400, - "Can't create aliases longer than %s characters" % self.MAX_ALIAS_LENGTH, + "Can't create aliases longer than %s characters" % MAX_ALIAS_LENGTH, Codes.INVALID_PARAM, ) diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py index 224d34ef3a..e5afeadf68 100644 --- a/synapse/handlers/message.py +++ b/synapse/handlers/message.py @@ -228,6 +228,7 @@ class EventCreationHandler(object): self.ratelimiter = hs.get_ratelimiter() self.notifier = hs.get_notifier() self.config = hs.config + self.require_membership_for_aliases = hs.config.require_membership_for_aliases self.send_event_to_master = ReplicationSendEventRestServlet.make_client(hs) @@ -336,6 +337,35 @@ class EventCreationHandler(object): prev_events_and_hashes=prev_events_and_hashes, ) + # In an ideal world we wouldn't need the second part of this condition. However, + # this behaviour isn't spec'd yet, meaning we should be able to deactivate this + # behaviour. Another reason is that this code is also evaluated each time a new + # m.room.aliases event is created, which includes hitting a /directory route. + # Therefore not including this condition here would render the similar one in + # synapse.handlers.directory pointless. + if builder.type == EventTypes.Aliases and self.require_membership_for_aliases: + # Ideally we'd do the membership check in event_auth.check(), which + # describes a spec'd algorithm for authenticating events received over + # federation as well as those created locally. As of room v3, aliases events + # can be created by users that are not in the room, therefore we have to + # tolerate them in event_auth.check(). + prev_state_ids = yield context.get_prev_state_ids(self.store) + prev_event_id = prev_state_ids.get((EventTypes.Member, event.sender)) + prev_event = yield self.store.get_event(prev_event_id, allow_none=True) + if not prev_event or prev_event.membership != Membership.JOIN: + logger.warning( + ("Attempt to send `m.room.aliases` in room %s by user %s but" + " membership is %s"), + event.room_id, + event.sender, + prev_event.membership if prev_event else None, + ) + + raise AuthError( + 403, + "You must be in the room to create an alias for it", + ) + self.validator.validate_new(event) defer.returnValue((event, context)) -- cgit 1.4.1