Ejemplo n.º 1
0
class EventCreationHandler(object):
    def __init__(self, hs):
        self.hs = hs
        self.auth = hs.get_auth()
        self.store = hs.get_datastore()
        self.state = hs.get_state_handler()
        self.clock = hs.get_clock()
        self.validator = EventValidator()
        self.profile_handler = hs.get_profile_handler()
        self.event_builder_factory = hs.get_event_builder_factory()
        self.server_name = hs.hostname
        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)

        # This is only used to get at ratelimit function, and maybe_kick_guest_users
        self.base_handler = BaseHandler(hs)

        self.pusher_pool = hs.get_pusherpool()

        # We arbitrarily limit concurrent event creation for a room to 5.
        # This is to stop us from diverging history *too* much.
        self.limiter = Linearizer(max_count=5, name="room_event_creation_limit")

        self.action_generator = hs.get_action_generator()

        self.spam_checker = hs.get_spam_checker()

        self._block_events_without_consent_error = (
            self.config.block_events_without_consent_error
        )

        # we need to construct a ConsentURIBuilder here, as it checks that the necessary
        # config options, but *only* if we have a configuration for which we are
        # going to need it.
        if self._block_events_without_consent_error:
            self._consent_uri_builder = ConsentURIBuilder(self.config)

    @defer.inlineCallbacks
    def create_event(self, requester, event_dict, token_id=None, txn_id=None,
                     prev_events_and_hashes=None, require_consent=True):
        """
        Given a dict from a client, create a new event.

        Creates an FrozenEvent object, filling out auth_events, prev_events,
        etc.

        Adds display names to Join membership events.

        Args:
            requester
            event_dict (dict): An entire event
            token_id (str)
            txn_id (str)

            prev_events_and_hashes (list[(str, dict[str, str], int)]|None):
                the forward extremities to use as the prev_events for the
                new event. For each event, a tuple of (event_id, hashes, depth)
                where *hashes* is a map from algorithm to hash.

                If None, they will be requested from the database.

            require_consent (bool): Whether to check if the requester has
                consented to privacy policy.
        Raises:
            ResourceLimitError if server is blocked to some resource being
            exceeded
        Returns:
            Tuple of created event (FrozenEvent), Context
        """
        yield self.auth.check_auth_blocking(requester.user.to_string())

        if event_dict["type"] == EventTypes.Create and event_dict["state_key"] == "":
            room_version = event_dict["content"]["room_version"]
        else:
            try:
                room_version = yield self.store.get_room_version(event_dict["room_id"])
            except NotFoundError:
                raise AuthError(403, "Unknown room")

        builder = self.event_builder_factory.new(room_version, event_dict)

        self.validator.validate_builder(builder)

        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            target = UserID.from_string(builder.state_key)

            if membership in {Membership.JOIN, Membership.INVITE}:
                # If event doesn't include a display name, add one.
                profile = self.profile_handler
                content = builder.content

                try:
                    if "displayname" not in content:
                        content["displayname"] = yield profile.get_displayname(target)
                    if "avatar_url" not in content:
                        content["avatar_url"] = yield profile.get_avatar_url(target)
                except Exception as e:
                    logger.info(
                        "Failed to get profile information for %r: %s",
                        target, e
                    )

        is_exempt = yield self._is_exempt_from_privacy_policy(builder, requester)
        if require_consent and not is_exempt:
            yield self.assert_accepted_privacy_policy(requester)

        if token_id is not None:
            builder.internal_metadata.token_id = token_id

        if txn_id is not None:
            builder.internal_metadata.txn_id = txn_id

        event, context = yield self.create_new_client_event(
            builder=builder,
            requester=requester,
            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))

    def _is_exempt_from_privacy_policy(self, builder, requester):
        """"Determine if an event to be sent is exempt from having to consent
        to the privacy policy

        Args:
            builder (synapse.events.builder.EventBuilder): event being created
            requester (Requster): user requesting this event

        Returns:
            Deferred[bool]: true if the event can be sent without the user
                consenting
        """
        # the only thing the user can do is join the server notices room.
        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            if membership == Membership.JOIN:
                return self._is_server_notices_room(builder.room_id)
            elif membership == Membership.LEAVE:
                # the user is always allowed to leave (but not kick people)
                return builder.state_key == requester.user.to_string()
        return succeed(False)

    @defer.inlineCallbacks
    def _is_server_notices_room(self, room_id):
        if self.config.server_notices_mxid is None:
            defer.returnValue(False)
        user_ids = yield self.store.get_users_in_room(room_id)
        defer.returnValue(self.config.server_notices_mxid in user_ids)

    @defer.inlineCallbacks
    def assert_accepted_privacy_policy(self, requester):
        """Check if a user has accepted the privacy policy

        Called when the given user is about to do something that requires
        privacy consent. We see if the user is exempt and otherwise check that
        they have given consent. If they have not, a ConsentNotGiven error is
        raised.

        Args:
            requester (synapse.types.Requester):
                The user making the request

        Returns:
            Deferred[None]: returns normally if the user has consented or is
                exempt

        Raises:
            ConsentNotGivenError: if the user has not given consent yet
        """
        if self._block_events_without_consent_error is None:
            return

        # exempt AS users from needing consent
        if requester.app_service is not None:
            return

        user_id = requester.user.to_string()

        # exempt the system notices user
        if (
            self.config.server_notices_mxid is not None and
            user_id == self.config.server_notices_mxid
        ):
            return

        u = yield self.store.get_user_by_id(user_id)
        assert u is not None
        if u["appservice_id"] is not None:
            # users registered by an appservice are exempt
            return
        if u["consent_version"] == self.config.user_consent_version:
            return

        consent_uri = self._consent_uri_builder.build_user_consent_uri(
            requester.user.localpart,
        )
        msg = self._block_events_without_consent_error % {
            'consent_uri': consent_uri,
        }
        raise ConsentNotGivenError(
            msg=msg,
            consent_uri=consent_uri,
        )

    @defer.inlineCallbacks
    def send_nonmember_event(self, requester, event, context, ratelimit=True):
        """
        Persists and notifies local clients and federation of an event.

        Args:
            event (FrozenEvent) the event to send.
            context (Context) the context of the event.
            ratelimit (bool): Whether to rate limit this send.
            is_guest (bool): Whether the sender is a guest.
        """
        if event.type == EventTypes.Member:
            raise SynapseError(
                500,
                "Tried to send member event through non-member codepath"
            )

        user = UserID.from_string(event.sender)

        assert self.hs.is_mine(user), "User must be our own: %s" % (user,)

        if event.is_state():
            prev_state = yield self.deduplicate_state_event(event, context)
            if prev_state is not None:
                logger.info(
                    "Not bothering to persist state event %s duplicated by %s",
                    event.event_id, prev_state.event_id,
                )
                defer.returnValue(prev_state)

        yield self.handle_new_client_event(
            requester=requester,
            event=event,
            context=context,
            ratelimit=ratelimit,
        )

    @defer.inlineCallbacks
    def deduplicate_state_event(self, event, context):
        """
        Checks whether event is in the latest resolved state in context.

        If so, returns the version of the event in context.
        Otherwise, returns None.
        """
        prev_state_ids = yield context.get_prev_state_ids(self.store)
        prev_event_id = prev_state_ids.get((event.type, event.state_key))
        prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
        if not prev_event:
            return

        if prev_event and event.user_id == prev_event.user_id:
            prev_content = encode_canonical_json(prev_event.content)
            next_content = encode_canonical_json(event.content)
            if prev_content == next_content:
                defer.returnValue(prev_event)
        return

    @defer.inlineCallbacks
    def create_and_send_nonmember_event(
        self,
        requester,
        event_dict,
        ratelimit=True,
        txn_id=None
    ):
        """
        Creates an event, then sends it.

        See self.create_event and self.send_nonmember_event.
        """

        # We limit the number of concurrent event sends in a room so that we
        # don't fork the DAG too much. If we don't limit then we can end up in
        # a situation where event persistence can't keep up, causing
        # extremities to pile up, which in turn leads to state resolution
        # taking longer.
        with (yield self.limiter.queue(event_dict["room_id"])):
            event, context = yield self.create_event(
                requester,
                event_dict,
                token_id=requester.access_token_id,
                txn_id=txn_id
            )

            spam_error = self.spam_checker.check_event_for_spam(event)
            if spam_error:
                if not isinstance(spam_error, string_types):
                    spam_error = "Spam is not permitted here"
                raise SynapseError(
                    403, spam_error, Codes.FORBIDDEN
                )

            yield self.send_nonmember_event(
                requester,
                event,
                context,
                ratelimit=ratelimit,
            )
        defer.returnValue(event)

    @measure_func("create_new_client_event")
    @defer.inlineCallbacks
    def create_new_client_event(self, builder, requester=None,
                                prev_events_and_hashes=None):
        """Create a new event for a local client

        Args:
            builder (EventBuilder):

            requester (synapse.types.Requester|None):

            prev_events_and_hashes (list[(str, dict[str, str], int)]|None):
                the forward extremities to use as the prev_events for the
                new event. For each event, a tuple of (event_id, hashes, depth)
                where *hashes* is a map from algorithm to hash.

                If None, they will be requested from the database.

        Returns:
            Deferred[(synapse.events.EventBase, synapse.events.snapshot.EventContext)]
        """

        if prev_events_and_hashes is not None:
            assert len(prev_events_and_hashes) <= 10, \
                "Attempting to create an event with %i prev_events" % (
                    len(prev_events_and_hashes),
            )
        else:
            prev_events_and_hashes = \
                yield self.store.get_prev_events_for_room(builder.room_id)

        prev_events = [
            (event_id, prev_hashes)
            for event_id, prev_hashes, _ in prev_events_and_hashes
        ]

        event = yield builder.build(
            prev_event_ids=[p for p, _ in prev_events],
        )
        context = yield self.state.compute_event_context(event)
        if requester:
            context.app_service = requester.app_service

        self.validator.validate_new(event)

        # If this event is an annotation then we check that that the sender
        # can't annotate the same way twice (e.g. stops users from liking an
        # event multiple times).
        relation = event.content.get("m.relates_to", {})
        if relation.get("rel_type") == RelationTypes.ANNOTATION:
            relates_to = relation["event_id"]
            aggregation_key = relation["key"]

            already_exists = yield self.store.has_user_annotated_event(
                relates_to, event.type, aggregation_key, event.sender,
            )
            if already_exists:
                raise SynapseError(400, "Can't send same reaction twice")

        logger.debug(
            "Created event %s",
            event.event_id,
        )

        defer.returnValue(
            (event, context,)
        )

    @measure_func("handle_new_client_event")
    @defer.inlineCallbacks
    def handle_new_client_event(
        self,
        requester,
        event,
        context,
        ratelimit=True,
        extra_users=[],
    ):
        """Processes a new event. This includes checking auth, persisting it,
        notifying users, sending to remote servers, etc.

        If called from a worker will hit out to the master process for final
        processing.

        Args:
            requester (Requester)
            event (FrozenEvent)
            context (EventContext)
            ratelimit (bool)
            extra_users (list(UserID)): Any extra users to notify about event
        """

        if event.is_state() and (event.type, event.state_key) == (EventTypes.Create, ""):
            room_version = event.content.get(
                "room_version", RoomVersions.V1.identifier
            )
        else:
            room_version = yield self.store.get_room_version(event.room_id)

        try:
            yield self.auth.check_from_context(room_version, event, context)
        except AuthError as err:
            logger.warn("Denying new event %r because %s", event, err)
            raise err

        # Ensure that we can round trip before trying to persist in db
        try:
            dump = frozendict_json_encoder.encode(event.content)
            json.loads(dump)
        except Exception:
            logger.exception("Failed to encode content: %r", event.content)
            raise

        yield self.action_generator.handle_push_actions_for_event(
            event, context
        )

        # reraise does not allow inlineCallbacks to preserve the stacktrace, so we
        # hack around with a try/finally instead.
        success = False
        try:
            # If we're a worker we need to hit out to the master.
            if self.config.worker_app:
                yield self.send_event_to_master(
                    event_id=event.event_id,
                    store=self.store,
                    requester=requester,
                    event=event,
                    context=context,
                    ratelimit=ratelimit,
                    extra_users=extra_users,
                )
                success = True
                return

            yield self.persist_and_notify_client_event(
                requester,
                event,
                context,
                ratelimit=ratelimit,
                extra_users=extra_users,
            )

            success = True
        finally:
            if not success:
                # Ensure that we actually remove the entries in the push actions
                # staging area, if we calculated them.
                run_in_background(
                    self.store.remove_push_actions_from_staging,
                    event.event_id,
                )

    @defer.inlineCallbacks
    def persist_and_notify_client_event(
        self,
        requester,
        event,
        context,
        ratelimit=True,
        extra_users=[],
    ):
        """Called when we have fully built the event, have already
        calculated the push actions for the event, and checked auth.

        This should only be run on master.
        """
        assert not self.config.worker_app

        if ratelimit:
            yield self.base_handler.ratelimit(requester)

        yield self.base_handler.maybe_kick_guest_users(event, context)

        if event.type == EventTypes.CanonicalAlias:
            # Check the alias is acually valid (at this time at least)
            room_alias_str = event.content.get("alias", None)
            if room_alias_str:
                room_alias = RoomAlias.from_string(room_alias_str)
                directory_handler = self.hs.get_handlers().directory_handler
                mapping = yield directory_handler.get_association(room_alias)

                if mapping["room_id"] != event.room_id:
                    raise SynapseError(
                        400,
                        "Room alias %s does not point to the room" % (
                            room_alias_str,
                        )
                    )

        federation_handler = self.hs.get_handlers().federation_handler

        if event.type == EventTypes.Member:
            if event.content["membership"] == Membership.INVITE:
                def is_inviter_member_event(e):
                    return (
                        e.type == EventTypes.Member and
                        e.sender == event.sender
                    )

                current_state_ids = yield context.get_current_state_ids(self.store)

                state_to_include_ids = [
                    e_id
                    for k, e_id in iteritems(current_state_ids)
                    if k[0] in self.hs.config.room_invite_state_types
                    or k == (EventTypes.Member, event.sender)
                ]

                state_to_include = yield self.store.get_events(state_to_include_ids)

                event.unsigned["invite_room_state"] = [
                    {
                        "type": e.type,
                        "state_key": e.state_key,
                        "content": e.content,
                        "sender": e.sender,
                    }
                    for e in itervalues(state_to_include)
                ]

                invitee = UserID.from_string(event.state_key)
                if not self.hs.is_mine(invitee):
                    # TODO: Can we add signature from remote server in a nicer
                    # way? If we have been invited by a remote server, we need
                    # to get them to sign the event.

                    returned_invite = yield federation_handler.send_invite(
                        invitee.domain,
                        event,
                    )

                    event.unsigned.pop("room_state", None)

                    # TODO: Make sure the signatures actually are correct.
                    event.signatures.update(
                        returned_invite.signatures
                    )

        if event.type == EventTypes.Redaction:
            prev_state_ids = yield context.get_prev_state_ids(self.store)
            auth_events_ids = yield self.auth.compute_auth_events(
                event, prev_state_ids, for_verification=True,
            )
            auth_events = yield self.store.get_events(auth_events_ids)
            auth_events = {
                (e.type, e.state_key): e for e in auth_events.values()
            }
            room_version = yield self.store.get_room_version(event.room_id)
            if self.auth.check_redaction(room_version, event, auth_events=auth_events):
                original_event = yield self.store.get_event(
                    event.redacts,
                    check_redacted=False,
                    get_prev_content=False,
                    allow_rejected=False,
                    allow_none=False
                )
                if event.user_id != original_event.user_id:
                    raise AuthError(
                        403,
                        "You don't have permission to redact events"
                    )

                # We've already checked.
                event.internal_metadata.recheck_redaction = False

        if event.type == EventTypes.Create:
            prev_state_ids = yield context.get_prev_state_ids(self.store)
            if prev_state_ids:
                raise AuthError(
                    403,
                    "Changing the room create event is forbidden",
                )

        (event_stream_id, max_stream_id) = yield self.store.persist_event(
            event, context=context
        )

        yield self.pusher_pool.on_new_notifications(
            event_stream_id, max_stream_id,
        )

        def _notify():
            try:
                self.notifier.on_new_room_event(
                    event, event_stream_id, max_stream_id,
                    extra_users=extra_users
                )
            except Exception:
                logger.exception("Error notifying about new room event")

        run_in_background(_notify)

        if event.type == EventTypes.Message:
            # We don't want to block sending messages on any presence code. This
            # matters as sometimes presence code can take a while.
            run_in_background(self._bump_active_time, requester.user)

    @defer.inlineCallbacks
    def _bump_active_time(self, user):
        try:
            presence = self.hs.get_presence_handler()
            yield presence.bump_presence_active_time(user)
        except Exception:
            logger.exception("Error bumping presence active time")
Ejemplo n.º 2
0
class EventCreationHandler(object):
    def __init__(self, hs: "HomeServer"):
        self.hs = hs
        self.auth = hs.get_auth()
        self.store = hs.get_datastore()
        self.storage = hs.get_storage()
        self.state = hs.get_state_handler()
        self.clock = hs.get_clock()
        self.validator = EventValidator()
        self.profile_handler = hs.get_profile_handler()
        self.event_builder_factory = hs.get_event_builder_factory()
        self.server_name = hs.hostname
        self.notifier = hs.get_notifier()
        self.config = hs.config
        self.require_membership_for_aliases = hs.config.require_membership_for_aliases
        self._is_event_writer = (
            self.config.worker.writers.events == hs.get_instance_name())

        self.room_invite_state_types = self.hs.config.room_invite_state_types

        self.send_event = ReplicationSendEventRestServlet.make_client(hs)

        # This is only used to get at ratelimit function, and maybe_kick_guest_users
        self.base_handler = BaseHandler(hs)

        self.pusher_pool = hs.get_pusherpool()

        # We arbitrarily limit concurrent event creation for a room to 5.
        # This is to stop us from diverging history *too* much.
        self.limiter = Linearizer(max_count=5,
                                  name="room_event_creation_limit")

        self.action_generator = hs.get_action_generator()

        self.spam_checker = hs.get_spam_checker()
        self.third_party_event_rules = hs.get_third_party_event_rules()

        self._block_events_without_consent_error = (
            self.config.block_events_without_consent_error)

        # Rooms which should be excluded from dummy insertion. (For instance,
        # those without local users who can send events into the room).
        #
        # map from room id to time-of-last-attempt.
        #
        self._rooms_to_exclude_from_dummy_event_insertion = {
        }  # type: dict[str, int]

        # we need to construct a ConsentURIBuilder here, as it checks that the necessary
        # config options, but *only* if we have a configuration for which we are
        # going to need it.
        if self._block_events_without_consent_error:
            self._consent_uri_builder = ConsentURIBuilder(self.config)

        if (not self.config.worker_app
                and self.config.cleanup_extremities_with_dummy_events):
            self.clock.looping_call(
                lambda: run_as_background_process(
                    "send_dummy_events_to_fill_extremities",
                    self._send_dummy_events_to_fill_extremities,
                ),
                5 * 60 * 1000,
            )

        self._message_handler = hs.get_message_handler()

        self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages

        self._dummy_events_threshold = hs.config.dummy_events_threshold

    @defer.inlineCallbacks
    def create_event(
        self,
        requester,
        event_dict,
        token_id=None,
        txn_id=None,
        prev_event_ids: Optional[Collection[str]] = None,
        require_consent=True,
    ):
        """
        Given a dict from a client, create a new event.

        Creates an FrozenEvent object, filling out auth_events, prev_events,
        etc.

        Adds display names to Join membership events.

        Args:
            requester
            event_dict (dict): An entire event
            token_id (str)
            txn_id (str)

            prev_event_ids:
                the forward extremities to use as the prev_events for the
                new event.

                If None, they will be requested from the database.

            require_consent (bool): Whether to check if the requester has
                consented to privacy policy.
        Raises:
            ResourceLimitError if server is blocked to some resource being
            exceeded
        Returns:
            Tuple of created event (FrozenEvent), Context
        """
        yield self.auth.check_auth_blocking(requester.user.to_string())

        if event_dict["type"] == EventTypes.Create and event_dict[
                "state_key"] == "":
            room_version = event_dict["content"]["room_version"]
        else:
            try:
                room_version = yield self.store.get_room_version_id(
                    event_dict["room_id"])
            except NotFoundError:
                raise AuthError(403, "Unknown room")

        builder = self.event_builder_factory.new(room_version, event_dict)

        self.validator.validate_builder(builder)

        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            target = UserID.from_string(builder.state_key)

            if membership in {Membership.JOIN, Membership.INVITE}:
                # If event doesn't include a display name, add one.
                profile = self.profile_handler
                content = builder.content

                try:
                    if "displayname" not in content:
                        displayname = yield profile.get_displayname(target)
                        if displayname is not None:
                            content["displayname"] = displayname
                    if "avatar_url" not in content:
                        avatar_url = yield profile.get_avatar_url(target)
                        if avatar_url is not None:
                            content["avatar_url"] = avatar_url
                except Exception as e:
                    logger.info("Failed to get profile information for %r: %s",
                                target, e)

        is_exempt = yield self._is_exempt_from_privacy_policy(
            builder, requester)
        if require_consent and not is_exempt:
            yield self.assert_accepted_privacy_policy(requester)

        if token_id is not None:
            builder.internal_metadata.token_id = token_id

        if txn_id is not None:
            builder.internal_metadata.txn_id = txn_id

        event, context = yield self.create_new_client_event(
            builder=builder,
            requester=requester,
            prev_event_ids=prev_event_ids,
        )

        # 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()
            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 prev_event_id else None)
            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, self.config)

        return (event, context)

    def _is_exempt_from_privacy_policy(self, builder, requester):
        """"Determine if an event to be sent is exempt from having to consent
        to the privacy policy

        Args:
            builder (synapse.events.builder.EventBuilder): event being created
            requester (Requster): user requesting this event

        Returns:
            Deferred[bool]: true if the event can be sent without the user
                consenting
        """
        # the only thing the user can do is join the server notices room.
        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            if membership == Membership.JOIN:
                return self._is_server_notices_room(builder.room_id)
            elif membership == Membership.LEAVE:
                # the user is always allowed to leave (but not kick people)
                return builder.state_key == requester.user.to_string()
        return succeed(False)

    @defer.inlineCallbacks
    def _is_server_notices_room(self, room_id):
        if self.config.server_notices_mxid is None:
            return False
        user_ids = yield self.store.get_users_in_room(room_id)
        return self.config.server_notices_mxid in user_ids

    @defer.inlineCallbacks
    def assert_accepted_privacy_policy(self, requester):
        """Check if a user has accepted the privacy policy

        Called when the given user is about to do something that requires
        privacy consent. We see if the user is exempt and otherwise check that
        they have given consent. If they have not, a ConsentNotGiven error is
        raised.

        Args:
            requester (synapse.types.Requester):
                The user making the request

        Returns:
            Deferred[None]: returns normally if the user has consented or is
                exempt

        Raises:
            ConsentNotGivenError: if the user has not given consent yet
        """
        if self._block_events_without_consent_error is None:
            return

        # exempt AS users from needing consent
        if requester.app_service is not None:
            return

        user_id = requester.user.to_string()

        # exempt the system notices user
        if (self.config.server_notices_mxid is not None
                and user_id == self.config.server_notices_mxid):
            return

        u = yield self.store.get_user_by_id(user_id)
        assert u is not None
        if u["user_type"] in (UserTypes.SUPPORT, UserTypes.BOT):
            # support and bot users are not required to consent
            return
        if u["appservice_id"] is not None:
            # users registered by an appservice are exempt
            return
        if u["consent_version"] == self.config.user_consent_version:
            return

        consent_uri = self._consent_uri_builder.build_user_consent_uri(
            requester.user.localpart)
        msg = self._block_events_without_consent_error % {
            "consent_uri": consent_uri
        }
        raise ConsentNotGivenError(msg=msg, consent_uri=consent_uri)

    async def send_nonmember_event(self,
                                   requester,
                                   event,
                                   context,
                                   ratelimit=True) -> int:
        """
        Persists and notifies local clients and federation of an event.

        Args:
            event (FrozenEvent) the event to send.
            context (Context) the context of the event.
            ratelimit (bool): Whether to rate limit this send.
            is_guest (bool): Whether the sender is a guest.

        Return:
            The stream_id of the persisted event.
        """
        if event.type == EventTypes.Member:
            raise SynapseError(
                500, "Tried to send member event through non-member codepath")

        user = UserID.from_string(event.sender)

        assert self.hs.is_mine(user), "User must be our own: %s" % (user, )

        if event.is_state():
            prev_state = await self.deduplicate_state_event(event, context)
            if prev_state is not None:
                logger.info(
                    "Not bothering to persist state event %s duplicated by %s",
                    event.event_id,
                    prev_state.event_id,
                )
                return prev_state

        return await self.handle_new_client_event(requester=requester,
                                                  event=event,
                                                  context=context,
                                                  ratelimit=ratelimit)

    @defer.inlineCallbacks
    def deduplicate_state_event(self, event, context):
        """
        Checks whether event is in the latest resolved state in context.

        If so, returns the version of the event in context.
        Otherwise, returns None.
        """
        prev_state_ids = yield context.get_prev_state_ids()
        prev_event_id = prev_state_ids.get((event.type, event.state_key))
        if not prev_event_id:
            return
        prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
        if not prev_event:
            return

        if prev_event and event.user_id == prev_event.user_id:
            prev_content = encode_canonical_json(prev_event.content)
            next_content = encode_canonical_json(event.content)
            if prev_content == next_content:
                return prev_event
        return

    async def create_and_send_nonmember_event(self,
                                              requester,
                                              event_dict,
                                              ratelimit=True,
                                              txn_id=None
                                              ) -> Tuple[EventBase, int]:
        """
        Creates an event, then sends it.

        See self.create_event and self.send_nonmember_event.
        """

        # We limit the number of concurrent event sends in a room so that we
        # don't fork the DAG too much. If we don't limit then we can end up in
        # a situation where event persistence can't keep up, causing
        # extremities to pile up, which in turn leads to state resolution
        # taking longer.
        with (await self.limiter.queue(event_dict["room_id"])):
            event, context = await self.create_event(
                requester,
                event_dict,
                token_id=requester.access_token_id,
                txn_id=txn_id)

            spam_error = self.spam_checker.check_event_for_spam(event)
            if spam_error:
                if not isinstance(spam_error, str):
                    spam_error = "Spam is not permitted here"
                raise SynapseError(403, spam_error, Codes.FORBIDDEN)

            stream_id = await self.send_nonmember_event(requester,
                                                        event,
                                                        context,
                                                        ratelimit=ratelimit)
        return event, stream_id

    @measure_func("create_new_client_event")
    @defer.inlineCallbacks
    def create_new_client_event(
            self,
            builder,
            requester=None,
            prev_event_ids: Optional[Collection[str]] = None):
        """Create a new event for a local client

        Args:
            builder (EventBuilder):

            requester (synapse.types.Requester|None):

            prev_event_ids:
                the forward extremities to use as the prev_events for the
                new event.

                If None, they will be requested from the database.

        Returns:
            Deferred[(synapse.events.EventBase, synapse.events.snapshot.EventContext)]
        """

        if prev_event_ids is not None:
            assert len(prev_event_ids) <= 10, (
                "Attempting to create an event with %i prev_events" %
                (len(prev_event_ids), ))
        else:
            prev_event_ids = yield self.store.get_prev_events_for_room(
                builder.room_id)

        event = yield builder.build(prev_event_ids=prev_event_ids)
        context = yield self.state.compute_event_context(event)
        if requester:
            context.app_service = requester.app_service

        self.validator.validate_new(event, self.config)

        # If this event is an annotation then we check that that the sender
        # can't annotate the same way twice (e.g. stops users from liking an
        # event multiple times).
        relation = event.content.get("m.relates_to", {})
        if relation.get("rel_type") == RelationTypes.ANNOTATION:
            relates_to = relation["event_id"]
            aggregation_key = relation["key"]

            already_exists = yield self.store.has_user_annotated_event(
                relates_to, event.type, aggregation_key, event.sender)
            if already_exists:
                raise SynapseError(400, "Can't send same reaction twice")

        logger.debug("Created event %s", event.event_id)

        return (event, context)

    @measure_func("handle_new_client_event")
    async def handle_new_client_event(self,
                                      requester,
                                      event,
                                      context,
                                      ratelimit=True,
                                      extra_users=[]) -> int:
        """Processes a new event. This includes checking auth, persisting it,
        notifying users, sending to remote servers, etc.

        If called from a worker will hit out to the master process for final
        processing.

        Args:
            requester (Requester)
            event (FrozenEvent)
            context (EventContext)
            ratelimit (bool)
            extra_users (list(UserID)): Any extra users to notify about event

        Return:
            The stream_id of the persisted event.
        """

        if event.is_state() and (event.type, event.state_key) == (
                EventTypes.Create,
                "",
        ):
            room_version = event.content.get("room_version",
                                             RoomVersions.V1.identifier)
        else:
            room_version = await self.store.get_room_version_id(event.room_id)

        event_allowed = await self.third_party_event_rules.check_event_allowed(
            event, context)
        if not event_allowed:
            raise SynapseError(403,
                               "This event is not allowed in this context",
                               Codes.FORBIDDEN)

        if event.internal_metadata.is_out_of_band_membership():
            # the only sort of out-of-band-membership events we expect to see here
            # are invite rejections we have generated ourselves.
            assert event.type == EventTypes.Member
            assert event.content["membership"] == Membership.LEAVE
        else:
            try:
                await self.auth.check_from_context(room_version, event,
                                                   context)
            except AuthError as err:
                logger.warning("Denying new event %r because %s", event, err)
                raise err

        # Ensure that we can round trip before trying to persist in db
        try:
            dump = frozendict_json_encoder.encode(event.content)
            json.loads(dump)
        except Exception:
            logger.exception("Failed to encode content: %r", event.content)
            raise

        await self.action_generator.handle_push_actions_for_event(
            event, context)

        # reraise does not allow inlineCallbacks to preserve the stacktrace, so we
        # hack around with a try/finally instead.
        success = False
        try:
            # If we're a worker we need to hit out to the master.
            if not self._is_event_writer:
                result = await self.send_event(
                    instance_name=self.config.worker.writers.events,
                    event_id=event.event_id,
                    store=self.store,
                    requester=requester,
                    event=event,
                    context=context,
                    ratelimit=ratelimit,
                    extra_users=extra_users,
                )
                stream_id = result["stream_id"]
                event.internal_metadata.stream_ordering = stream_id
                success = True
                return stream_id

            stream_id = await self.persist_and_notify_client_event(
                requester,
                event,
                context,
                ratelimit=ratelimit,
                extra_users=extra_users)

            success = True
            return stream_id
        finally:
            if not success:
                # Ensure that we actually remove the entries in the push actions
                # staging area, if we calculated them.
                run_in_background(self.store.remove_push_actions_from_staging,
                                  event.event_id)

    @defer.inlineCallbacks
    def _validate_canonical_alias(self, directory_handler, room_alias_str,
                                  expected_room_id):
        """
        Ensure that the given room alias points to the expected room ID.

        Args:
            directory_handler: The directory handler object.
            room_alias_str: The room alias to check.
            expected_room_id: The room ID that the alias should point to.
        """
        room_alias = RoomAlias.from_string(room_alias_str)
        try:
            mapping = yield defer.ensureDeferred(
                directory_handler.get_association(room_alias))
        except SynapseError as e:
            # Turn M_NOT_FOUND errors into M_BAD_ALIAS errors.
            if e.errcode == Codes.NOT_FOUND:
                raise SynapseError(
                    400,
                    "Room alias %s does not point to the room" %
                    (room_alias_str, ),
                    Codes.BAD_ALIAS,
                )
            raise

        if mapping["room_id"] != expected_room_id:
            raise SynapseError(
                400,
                "Room alias %s does not point to the room" %
                (room_alias_str, ),
                Codes.BAD_ALIAS,
            )

    async def persist_and_notify_client_event(self,
                                              requester,
                                              event,
                                              context,
                                              ratelimit=True,
                                              extra_users=[]) -> int:
        """Called when we have fully built the event, have already
        calculated the push actions for the event, and checked auth.

        This should only be run on the instance in charge of persisting events.
        """
        assert self._is_event_writer

        if ratelimit:
            # We check if this is a room admin redacting an event so that we
            # can apply different ratelimiting. We do this by simply checking
            # it's not a self-redaction (to avoid having to look up whether the
            # user is actually admin or not).
            is_admin_redaction = False
            if event.type == EventTypes.Redaction:
                original_event = await self.store.get_event(
                    event.redacts,
                    redact_behaviour=EventRedactBehaviour.AS_IS,
                    get_prev_content=False,
                    allow_rejected=False,
                    allow_none=True,
                )

                is_admin_redaction = (original_event and
                                      event.sender != original_event.sender)

            await self.base_handler.ratelimit(
                requester, is_admin_redaction=is_admin_redaction)

        await self.base_handler.maybe_kick_guest_users(event, context)

        if event.type == EventTypes.CanonicalAlias:
            # Validate a newly added alias or newly added alt_aliases.

            original_alias = None
            original_alt_aliases = set()

            original_event_id = event.unsigned.get("replaces_state")
            if original_event_id:
                original_event = await self.store.get_event(original_event_id)

                if original_event:
                    original_alias = original_event.content.get("alias", None)
                    original_alt_aliases = original_event.content.get(
                        "alt_aliases", [])

            # Check the alias is currently valid (if it has changed).
            room_alias_str = event.content.get("alias", None)
            directory_handler = self.hs.get_handlers().directory_handler
            if room_alias_str and room_alias_str != original_alias:
                await self._validate_canonical_alias(directory_handler,
                                                     room_alias_str,
                                                     event.room_id)

            # Check that alt_aliases is the proper form.
            alt_aliases = event.content.get("alt_aliases", [])
            if not isinstance(alt_aliases, (list, tuple)):
                raise SynapseError(400,
                                   "The alt_aliases property must be a list.",
                                   Codes.INVALID_PARAM)

            # If the old version of alt_aliases is of an unknown form,
            # completely replace it.
            if not isinstance(original_alt_aliases, (list, tuple)):
                original_alt_aliases = []

            # Check that each alias is currently valid.
            new_alt_aliases = set(alt_aliases) - set(original_alt_aliases)
            if new_alt_aliases:
                for alias_str in new_alt_aliases:
                    await self._validate_canonical_alias(
                        directory_handler, alias_str, event.room_id)

        federation_handler = self.hs.get_handlers().federation_handler

        if event.type == EventTypes.Member:
            if event.content["membership"] == Membership.INVITE:

                def is_inviter_member_event(e):
                    return e.type == EventTypes.Member and e.sender == event.sender

                current_state_ids = await context.get_current_state_ids()

                state_to_include_ids = [
                    e_id for k, e_id in current_state_ids.items()
                    if k[0] in self.room_invite_state_types or k == (
                        EventTypes.Member, event.sender)
                ]

                state_to_include = await self.store.get_events(
                    state_to_include_ids)

                event.unsigned["invite_room_state"] = [{
                    "type": e.type,
                    "state_key": e.state_key,
                    "content": e.content,
                    "sender": e.sender,
                } for e in state_to_include.values()]

                invitee = UserID.from_string(event.state_key)
                if not self.hs.is_mine(invitee):
                    # TODO: Can we add signature from remote server in a nicer
                    # way? If we have been invited by a remote server, we need
                    # to get them to sign the event.

                    returned_invite = await federation_handler.send_invite(
                        invitee.domain, event)
                    event.unsigned.pop("room_state", None)

                    # TODO: Make sure the signatures actually are correct.
                    event.signatures.update(returned_invite.signatures)

        if event.type == EventTypes.Redaction:
            original_event = await self.store.get_event(
                event.redacts,
                redact_behaviour=EventRedactBehaviour.AS_IS,
                get_prev_content=False,
                allow_rejected=False,
                allow_none=True,
            )

            # we can make some additional checks now if we have the original event.
            if original_event:
                if original_event.type == EventTypes.Create:
                    raise AuthError(
                        403, "Redacting create events is not permitted")

                if original_event.room_id != event.room_id:
                    raise SynapseError(
                        400, "Cannot redact event from a different room")

            prev_state_ids = await context.get_prev_state_ids()
            auth_events_ids = await self.auth.compute_auth_events(
                event, prev_state_ids, for_verification=True)
            auth_events = await self.store.get_events(auth_events_ids)
            auth_events = {(e.type, e.state_key): e
                           for e in auth_events.values()}

            room_version = await self.store.get_room_version_id(event.room_id)
            room_version_obj = KNOWN_ROOM_VERSIONS[room_version]

            if event_auth.check_redaction(room_version_obj,
                                          event,
                                          auth_events=auth_events):
                # this user doesn't have 'redact' rights, so we need to do some more
                # checks on the original event. Let's start by checking the original
                # event exists.
                if not original_event:
                    raise NotFoundError("Could not find event %s" %
                                        (event.redacts, ))

                if event.user_id != original_event.user_id:
                    raise AuthError(
                        403, "You don't have permission to redact events")

                # all the checks are done.
                event.internal_metadata.recheck_redaction = False

        if event.type == EventTypes.Create:
            prev_state_ids = await context.get_prev_state_ids()
            if prev_state_ids:
                raise AuthError(403,
                                "Changing the room create event is forbidden")

        event_stream_id, max_stream_id = await self.storage.persistence.persist_event(
            event, context=context)

        if self._ephemeral_events_enabled:
            # If there's an expiry timestamp on the event, schedule its expiry.
            self._message_handler.maybe_schedule_expiry(event)

        await self.pusher_pool.on_new_notifications(event_stream_id,
                                                    max_stream_id)

        def _notify():
            try:
                self.notifier.on_new_room_event(event,
                                                event_stream_id,
                                                max_stream_id,
                                                extra_users=extra_users)
            except Exception:
                logger.exception("Error notifying about new room event")

        run_in_background(_notify)

        if event.type == EventTypes.Message:
            # We don't want to block sending messages on any presence code. This
            # matters as sometimes presence code can take a while.
            run_in_background(self._bump_active_time, requester.user)

        return event_stream_id

    async def _bump_active_time(self, user):
        try:
            presence = self.hs.get_presence_handler()
            await presence.bump_presence_active_time(user)
        except Exception:
            logger.exception("Error bumping presence active time")

    async def _send_dummy_events_to_fill_extremities(self):
        """Background task to send dummy events into rooms that have a large
        number of extremities
        """
        self._expire_rooms_to_exclude_from_dummy_event_insertion()
        room_ids = await self.store.get_rooms_with_many_extremities(
            min_count=self._dummy_events_threshold,
            limit=5,
            room_id_filter=self._rooms_to_exclude_from_dummy_event_insertion.
            keys(),
        )

        for room_id in room_ids:
            # For each room we need to find a joined member we can use to send
            # the dummy event with.

            latest_event_ids = await self.store.get_prev_events_for_room(
                room_id)

            members = await self.state.get_current_users_in_room(
                room_id, latest_event_ids=latest_event_ids)
            dummy_event_sent = False
            for user_id in members:
                if not self.hs.is_mine_id(user_id):
                    continue
                requester = create_requester(user_id)
                try:
                    event, context = await self.create_event(
                        requester,
                        {
                            "type": "org.matrix.dummy_event",
                            "content": {},
                            "room_id": room_id,
                            "sender": user_id,
                        },
                        prev_event_ids=latest_event_ids,
                    )

                    event.internal_metadata.proactively_send = False

                    await self.send_nonmember_event(requester,
                                                    event,
                                                    context,
                                                    ratelimit=False)
                    dummy_event_sent = True
                    break
                except ConsentNotGivenError:
                    logger.info(
                        "Failed to send dummy event into room %s for user %s due to "
                        "lack of consent. Will try another user" %
                        (room_id, user_id))
                except AuthError:
                    logger.info(
                        "Failed to send dummy event into room %s for user %s due to "
                        "lack of power. Will try another user" %
                        (room_id, user_id))

            if not dummy_event_sent:
                # Did not find a valid user in the room, so remove from future attempts
                # Exclusion is time limited, so the room will be rechecked in the future
                # dependent on _DUMMY_EVENT_ROOM_EXCLUSION_EXPIRY
                logger.info(
                    "Failed to send dummy event into room %s. Will exclude it from "
                    "future attempts until cache expires" % (room_id, ))
                now = self.clock.time_msec()
                self._rooms_to_exclude_from_dummy_event_insertion[
                    room_id] = now

    def _expire_rooms_to_exclude_from_dummy_event_insertion(self):
        expire_before = self.clock.time_msec(
        ) - _DUMMY_EVENT_ROOM_EXCLUSION_EXPIRY
        to_expire = set()
        for room_id, time in self._rooms_to_exclude_from_dummy_event_insertion.items(
        ):
            if time < expire_before:
                to_expire.add(room_id)
        for room_id in to_expire:
            logger.debug(
                "Expiring room id %s from dummy event insertion exclusion cache",
                room_id,
            )
            del self._rooms_to_exclude_from_dummy_event_insertion[room_id]
Ejemplo n.º 3
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class EventCreationHandler(object):
    def __init__(self, hs):
        self.hs = hs
        self.auth = hs.get_auth()
        self.store = hs.get_datastore()
        self.state = hs.get_state_handler()
        self.clock = hs.get_clock()
        self.validator = EventValidator()
        self.profile_handler = hs.get_profile_handler()
        self.event_builder_factory = hs.get_event_builder_factory()
        self.server_name = hs.hostname
        self.ratelimiter = hs.get_ratelimiter()
        self.notifier = hs.get_notifier()
        self.config = hs.config

        self.send_event_to_master = ReplicationSendEventRestServlet.make_client(
            hs)

        # This is only used to get at ratelimit function, and maybe_kick_guest_users
        self.base_handler = BaseHandler(hs)

        self.pusher_pool = hs.get_pusherpool()

        # We arbitrarily limit concurrent event creation for a room to 5.
        # This is to stop us from diverging history *too* much.
        self.limiter = Linearizer(max_count=5,
                                  name="room_event_creation_limit")

        self.action_generator = hs.get_action_generator()

        self.spam_checker = hs.get_spam_checker()

        if self.config.block_events_without_consent_error is not None:
            self._consent_uri_builder = ConsentURIBuilder(self.config)

    @defer.inlineCallbacks
    def create_event(self,
                     requester,
                     event_dict,
                     token_id=None,
                     txn_id=None,
                     prev_events_and_hashes=None):
        """
        Given a dict from a client, create a new event.

        Creates an FrozenEvent object, filling out auth_events, prev_events,
        etc.

        Adds display names to Join membership events.

        Args:
            requester
            event_dict (dict): An entire event
            token_id (str)
            txn_id (str)

            prev_events_and_hashes (list[(str, dict[str, str], int)]|None):
                the forward extremities to use as the prev_events for the
                new event. For each event, a tuple of (event_id, hashes, depth)
                where *hashes* is a map from algorithm to hash.

                If None, they will be requested from the database.
        Raises:
            ResourceLimitError if server is blocked to some resource being
            exceeded
        Returns:
            Tuple of created event (FrozenEvent), Context
        """
        yield self.auth.check_auth_blocking(requester.user.to_string())

        if event_dict["type"] == EventTypes.Create and event_dict[
                "state_key"] == "":
            room_version = event_dict["content"]["room_version"]
        else:
            try:
                room_version = yield self.store.get_room_version(
                    event_dict["room_id"])
            except NotFoundError:
                raise AuthError(403, "Unknown room")

        builder = self.event_builder_factory.new(room_version, event_dict)

        self.validator.validate_builder(builder)

        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            target = UserID.from_string(builder.state_key)

            if membership in {Membership.JOIN, Membership.INVITE}:
                # If event doesn't include a display name, add one.
                profile = self.profile_handler
                content = builder.content

                try:
                    if "displayname" not in content:
                        content["displayname"] = yield profile.get_displayname(
                            target)
                    if "avatar_url" not in content:
                        content["avatar_url"] = yield profile.get_avatar_url(
                            target)
                except Exception as e:
                    logger.info("Failed to get profile information for %r: %s",
                                target, e)

        is_exempt = yield self._is_exempt_from_privacy_policy(
            builder, requester)
        if not is_exempt:
            yield self.assert_accepted_privacy_policy(requester)

        if token_id is not None:
            builder.internal_metadata.token_id = token_id

        if txn_id is not None:
            builder.internal_metadata.txn_id = txn_id

        event, context = yield self.create_new_client_event(
            builder=builder,
            requester=requester,
            prev_events_and_hashes=prev_events_and_hashes,
        )

        self.validator.validate_new(event)

        defer.returnValue((event, context))

    def _is_exempt_from_privacy_policy(self, builder, requester):
        """"Determine if an event to be sent is exempt from having to consent
        to the privacy policy

        Args:
            builder (synapse.events.builder.EventBuilder): event being created
            requester (Requster): user requesting this event

        Returns:
            Deferred[bool]: true if the event can be sent without the user
                consenting
        """
        # the only thing the user can do is join the server notices room.
        if builder.type == EventTypes.Member:
            membership = builder.content.get("membership", None)
            if membership == Membership.JOIN:
                return self._is_server_notices_room(builder.room_id)
            elif membership == Membership.LEAVE:
                # the user is always allowed to leave (but not kick people)
                return builder.state_key == requester.user.to_string()
        return succeed(False)

    @defer.inlineCallbacks
    def _is_server_notices_room(self, room_id):
        if self.config.server_notices_mxid is None:
            defer.returnValue(False)
        user_ids = yield self.store.get_users_in_room(room_id)
        defer.returnValue(self.config.server_notices_mxid in user_ids)

    @defer.inlineCallbacks
    def assert_accepted_privacy_policy(self, requester):
        """Check if a user has accepted the privacy policy

        Called when the given user is about to do something that requires
        privacy consent. We see if the user is exempt and otherwise check that
        they have given consent. If they have not, a ConsentNotGiven error is
        raised.

        Args:
            requester (synapse.types.Requester):
                The user making the request

        Returns:
            Deferred[None]: returns normally if the user has consented or is
                exempt

        Raises:
            ConsentNotGivenError: if the user has not given consent yet
        """
        if self.config.block_events_without_consent_error is None:
            return

        # exempt AS users from needing consent
        if requester.app_service is not None:
            return

        user_id = requester.user.to_string()

        # exempt the system notices user
        if (self.config.server_notices_mxid is not None
                and user_id == self.config.server_notices_mxid):
            return

        u = yield self.store.get_user_by_id(user_id)
        assert u is not None
        if u["appservice_id"] is not None:
            # users registered by an appservice are exempt
            return
        if u["consent_version"] == self.config.user_consent_version:
            return

        consent_uri = self._consent_uri_builder.build_user_consent_uri(
            requester.user.localpart, )
        msg = self.config.block_events_without_consent_error % {
            'consent_uri': consent_uri,
        }
        raise ConsentNotGivenError(
            msg=msg,
            consent_uri=consent_uri,
        )

    @defer.inlineCallbacks
    def send_nonmember_event(self, requester, event, context, ratelimit=True):
        """
        Persists and notifies local clients and federation of an event.

        Args:
            event (FrozenEvent) the event to send.
            context (Context) the context of the event.
            ratelimit (bool): Whether to rate limit this send.
            is_guest (bool): Whether the sender is a guest.
        """
        if event.type == EventTypes.Member:
            raise SynapseError(
                500, "Tried to send member event through non-member codepath")

        user = UserID.from_string(event.sender)

        assert self.hs.is_mine(user), "User must be our own: %s" % (user, )

        if event.is_state():
            prev_state = yield self.deduplicate_state_event(event, context)
            logger.info(
                "Not bothering to persist duplicate state event %s",
                event.event_id,
            )
            if prev_state is not None:
                defer.returnValue(prev_state)

        yield self.handle_new_client_event(
            requester=requester,
            event=event,
            context=context,
            ratelimit=ratelimit,
        )

    @defer.inlineCallbacks
    def deduplicate_state_event(self, event, context):
        """
        Checks whether event is in the latest resolved state in context.

        If so, returns the version of the event in context.
        Otherwise, returns None.
        """
        prev_state_ids = yield context.get_prev_state_ids(self.store)
        prev_event_id = prev_state_ids.get((event.type, event.state_key))
        prev_event = yield self.store.get_event(prev_event_id, allow_none=True)
        if not prev_event:
            return

        if prev_event and event.user_id == prev_event.user_id:
            prev_content = encode_canonical_json(prev_event.content)
            next_content = encode_canonical_json(event.content)
            if prev_content == next_content:
                defer.returnValue(prev_event)
        return

    @defer.inlineCallbacks
    def create_and_send_nonmember_event(self,
                                        requester,
                                        event_dict,
                                        ratelimit=True,
                                        txn_id=None):
        """
        Creates an event, then sends it.

        See self.create_event and self.send_nonmember_event.
        """

        # We limit the number of concurrent event sends in a room so that we
        # don't fork the DAG too much. If we don't limit then we can end up in
        # a situation where event persistence can't keep up, causing
        # extremities to pile up, which in turn leads to state resolution
        # taking longer.
        with (yield self.limiter.queue(event_dict["room_id"])):
            event, context = yield self.create_event(
                requester,
                event_dict,
                token_id=requester.access_token_id,
                txn_id=txn_id)

            spam_error = self.spam_checker.check_event_for_spam(event)
            if spam_error:
                if not isinstance(spam_error, string_types):
                    spam_error = "Spam is not permitted here"
                raise SynapseError(403, spam_error, Codes.FORBIDDEN)

            yield self.send_nonmember_event(
                requester,
                event,
                context,
                ratelimit=ratelimit,
            )
        defer.returnValue(event)

    @measure_func("create_new_client_event")
    @defer.inlineCallbacks
    def create_new_client_event(self,
                                builder,
                                requester=None,
                                prev_events_and_hashes=None):
        """Create a new event for a local client

        Args:
            builder (EventBuilder):

            requester (synapse.types.Requester|None):

            prev_events_and_hashes (list[(str, dict[str, str], int)]|None):
                the forward extremities to use as the prev_events for the
                new event. For each event, a tuple of (event_id, hashes, depth)
                where *hashes* is a map from algorithm to hash.

                If None, they will be requested from the database.

        Returns:
            Deferred[(synapse.events.EventBase, synapse.events.snapshot.EventContext)]
        """

        if prev_events_and_hashes is not None:
            assert len(prev_events_and_hashes) <= 10, \
                "Attempting to create an event with %i prev_events" % (
                    len(prev_events_and_hashes),
            )
        else:
            prev_events_and_hashes = \
                yield self.store.get_prev_events_for_room(builder.room_id)

        prev_events = [(event_id, prev_hashes)
                       for event_id, prev_hashes, _ in prev_events_and_hashes]

        event = yield builder.build(prev_event_ids=[p
                                                    for p, _ in prev_events], )
        context = yield self.state.compute_event_context(event)
        if requester:
            context.app_service = requester.app_service

        self.validator.validate_new(event)

        logger.debug(
            "Created event %s",
            event.event_id,
        )

        defer.returnValue((
            event,
            context,
        ))

    @measure_func("handle_new_client_event")
    @defer.inlineCallbacks
    def handle_new_client_event(
        self,
        requester,
        event,
        context,
        ratelimit=True,
        extra_users=[],
    ):
        """Processes a new event. This includes checking auth, persisting it,
        notifying users, sending to remote servers, etc.

        If called from a worker will hit out to the master process for final
        processing.

        Args:
            requester (Requester)
            event (FrozenEvent)
            context (EventContext)
            ratelimit (bool)
            extra_users (list(UserID)): Any extra users to notify about event
        """

        if event.is_state() and (event.type,
                                 event.state_key) == (EventTypes.Create, ""):
            room_version = event.content.get("room_version", RoomVersions.V1)
        else:
            room_version = yield self.store.get_room_version(event.room_id)

        try:
            yield self.auth.check_from_context(room_version, event, context)
        except AuthError as err:
            logger.warn("Denying new event %r because %s", event, err)
            raise err

        # Ensure that we can round trip before trying to persist in db
        try:
            dump = frozendict_json_encoder.encode(event.content)
            json.loads(dump)
        except Exception:
            logger.exception("Failed to encode content: %r", event.content)
            raise

        yield self.action_generator.handle_push_actions_for_event(
            event, context)

        # reraise does not allow inlineCallbacks to preserve the stacktrace, so we
        # hack around with a try/finally instead.
        success = False
        try:
            # If we're a worker we need to hit out to the master.
            if self.config.worker_app:
                yield self.send_event_to_master(
                    event_id=event.event_id,
                    store=self.store,
                    requester=requester,
                    event=event,
                    context=context,
                    ratelimit=ratelimit,
                    extra_users=extra_users,
                )
                success = True
                return

            yield self.persist_and_notify_client_event(
                requester,
                event,
                context,
                ratelimit=ratelimit,
                extra_users=extra_users,
            )

            success = True
        finally:
            if not success:
                # Ensure that we actually remove the entries in the push actions
                # staging area, if we calculated them.
                run_in_background(
                    self.store.remove_push_actions_from_staging,
                    event.event_id,
                )

    @defer.inlineCallbacks
    def persist_and_notify_client_event(
        self,
        requester,
        event,
        context,
        ratelimit=True,
        extra_users=[],
    ):
        """Called when we have fully built the event, have already
        calculated the push actions for the event, and checked auth.

        This should only be run on master.
        """
        assert not self.config.worker_app

        if ratelimit:
            yield self.base_handler.ratelimit(requester)

        yield self.base_handler.maybe_kick_guest_users(event, context)

        if event.type == EventTypes.CanonicalAlias:
            # Check the alias is acually valid (at this time at least)
            room_alias_str = event.content.get("alias", None)
            if room_alias_str:
                room_alias = RoomAlias.from_string(room_alias_str)
                directory_handler = self.hs.get_handlers().directory_handler
                mapping = yield directory_handler.get_association(room_alias)

                if mapping["room_id"] != event.room_id:
                    raise SynapseError(
                        400, "Room alias %s does not point to the room" %
                        (room_alias_str, ))

        federation_handler = self.hs.get_handlers().federation_handler

        if event.type == EventTypes.Member:
            if event.content["membership"] == Membership.INVITE:

                def is_inviter_member_event(e):
                    return (e.type == EventTypes.Member
                            and e.sender == event.sender)

                current_state_ids = yield context.get_current_state_ids(
                    self.store)

                state_to_include_ids = [
                    e_id for k, e_id in iteritems(current_state_ids)
                    if k[0] in self.hs.config.room_invite_state_types or k == (
                        EventTypes.Member, event.sender)
                ]

                state_to_include = yield self.store.get_events(
                    state_to_include_ids)

                event.unsigned["invite_room_state"] = [{
                    "type": e.type,
                    "state_key": e.state_key,
                    "content": e.content,
                    "sender": e.sender,
                } for e in itervalues(state_to_include)]

                invitee = UserID.from_string(event.state_key)
                if not self.hs.is_mine(invitee):
                    # TODO: Can we add signature from remote server in a nicer
                    # way? If we have been invited by a remote server, we need
                    # to get them to sign the event.

                    returned_invite = yield federation_handler.send_invite(
                        invitee.domain,
                        event,
                    )

                    event.unsigned.pop("room_state", None)

                    # TODO: Make sure the signatures actually are correct.
                    event.signatures.update(returned_invite.signatures)

        if event.type == EventTypes.Redaction:
            prev_state_ids = yield context.get_prev_state_ids(self.store)
            auth_events_ids = yield self.auth.compute_auth_events(
                event,
                prev_state_ids,
                for_verification=True,
            )
            auth_events = yield self.store.get_events(auth_events_ids)
            auth_events = {(e.type, e.state_key): e
                           for e in auth_events.values()}
            room_version = yield self.store.get_room_version(event.room_id)
            if self.auth.check_redaction(room_version,
                                         event,
                                         auth_events=auth_events):
                original_event = yield self.store.get_event(
                    event.redacts,
                    check_redacted=False,
                    get_prev_content=False,
                    allow_rejected=False,
                    allow_none=False)
                if event.user_id != original_event.user_id:
                    raise AuthError(
                        403, "You don't have permission to redact events")

                # We've already checked.
                event.internal_metadata.recheck_redaction = False

        if event.type == EventTypes.Create:
            prev_state_ids = yield context.get_prev_state_ids(self.store)
            if prev_state_ids:
                raise AuthError(
                    403,
                    "Changing the room create event is forbidden",
                )

        (event_stream_id,
         max_stream_id) = yield self.store.persist_event(event,
                                                         context=context)

        yield self.pusher_pool.on_new_notifications(
            event_stream_id,
            max_stream_id,
        )

        def _notify():
            try:
                self.notifier.on_new_room_event(event,
                                                event_stream_id,
                                                max_stream_id,
                                                extra_users=extra_users)
            except Exception:
                logger.exception("Error notifying about new room event")

        run_in_background(_notify)

        if event.type == EventTypes.Message:
            # We don't want to block sending messages on any presence code. This
            # matters as sometimes presence code can take a while.
            run_in_background(self._bump_active_time, requester.user)

    @defer.inlineCallbacks
    def _bump_active_time(self, user):
        try:
            presence = self.hs.get_presence_handler()
            yield presence.bump_presence_active_time(user)
        except Exception:
            logger.exception("Error bumping presence active time")