path: root/synapse/handlers/_base.py

# -*- coding: utf-8 -*-
# Copyright 2014 - 2016 OpenMarket 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.

from twisted.internet import defer

from synapse.api.errors import LimitExceededError
from synapse.api.constants import Membership, EventTypes
from synapse.types import UserID, Requester

from synapse.util.logcontext import preserve_fn

import logging


logger = logging.getLogger(__name__)


VISIBILITY_PRIORITY = (
    "world_readable",
    "shared",
    "invited",
    "joined",
)


MEMBERSHIP_PRIORITY = (
    Membership.JOIN,
    Membership.INVITE,
    Membership.KNOCK,
    Membership.LEAVE,
    Membership.BAN,
)


class BaseHandler(object):
    """
    Common base class for the event handlers.

    Attributes:
        store (synapse.storage.events.StateStore):
        state_handler (synapse.state.StateHandler):
    """

    def __init__(self, hs):
        self.store = hs.get_datastore()
        self.auth = hs.get_auth()
        self.notifier = hs.get_notifier()
        self.state_handler = hs.get_state_handler()
        self.distributor = hs.get_distributor()
        self.ratelimiter = hs.get_ratelimiter()
        self.clock = hs.get_clock()
        self.hs = hs

        self.server_name = hs.hostname

        self.event_builder_factory = hs.get_event_builder_factory()

    @defer.inlineCallbacks
    def filter_events_for_clients(self, user_tuples, events, event_id_to_state):
        """ Returns dict of user_id -> list of events that user is allowed to
        see.

        Args:
            user_tuples (str, bool): (user id, is_peeking) for each user to be
                checked. is_peeking should be true if:
                * the user is not currently a member of the room, and:
                * the user has not been a member of the room since the
                given events
            events ([synapse.events.EventBase]): list of events to filter
        """
        forgotten = yield defer.gatherResults([
            preserve_fn(self.store.who_forgot_in_room)(
                room_id,
            )
            for room_id in frozenset(e.room_id for e in events)
        ], consumeErrors=True)

        # Set of membership event_ids that have been forgotten
        event_id_forgotten = frozenset(
            row["event_id"] for rows in forgotten for row in rows
        )

        ignore_dict_content = yield self.store.get_global_account_data_by_type_for_users(
            "m.ignored_user_list", user_ids=[user_id for user_id, _ in user_tuples]
        )

        # FIXME: This will explode if people upload something incorrect.
        ignore_dict = {
            user_id: frozenset(
                content.get("ignored_users", {}).keys() if content else []
            )
            for user_id, content in ignore_dict_content.items()
        }

        def allowed(event, user_id, is_peeking, ignore_list):
            """
            Args:
                event (synapse.events.EventBase): event to check
                user_id (str)
                is_peeking (bool)
                ignore_list (list): list of users to ignore
            """
            if not event.is_state() and event.sender in ignore_list:
                return False

            state = event_id_to_state[event.event_id]

            # get the room_visibility at the time of the event.
            visibility_event = state.get((EventTypes.RoomHistoryVisibility, ""), None)
            if visibility_event:
                visibility = visibility_event.content.get("history_visibility", "shared")
            else:
                visibility = "shared"

            if visibility not in VISIBILITY_PRIORITY:
                visibility = "shared"

            # if it was world_readable, it's easy: everyone can read it
            if visibility == "world_readable":
                return True

            # Always allow history visibility events on boundaries. This is done
            # by setting the effective visibility to the least restrictive
            # of the old vs new.
            if event.type == EventTypes.RoomHistoryVisibility:
                prev_content = event.unsigned.get("prev_content", {})
                prev_visibility = prev_content.get("history_visibility", None)

                if prev_visibility not in VISIBILITY_PRIORITY:
                    prev_visibility = "shared"

                new_priority = VISIBILITY_PRIORITY.index(visibility)
                old_priority = VISIBILITY_PRIORITY.index(prev_visibility)
                if old_priority < new_priority:
                    visibility = prev_visibility

            # likewise, if the event is the user's own membership event, use
            # the 'most joined' membership
            membership = None
            if event.type == EventTypes.Member and event.state_key == user_id:
                membership = event.content.get("membership", None)
                if membership not in MEMBERSHIP_PRIORITY:
                    membership = "leave"

                prev_content = event.unsigned.get("prev_content", {})
                prev_membership = prev_content.get("membership", None)
                if prev_membership not in MEMBERSHIP_PRIORITY:
                    prev_membership = "leave"

                new_priority = MEMBERSHIP_PRIORITY.index(membership)
                old_priority = MEMBERSHIP_PRIORITY.index(prev_membership)
                if old_priority < new_priority:
                    membership = prev_membership

            # otherwise, get the user's membership at the time of the event.
            if membership is None:
                membership_event = state.get((EventTypes.Member, user_id), None)
                if membership_event:
                    if membership_event.event_id not in event_id_forgotten:
                        membership = membership_event.membership

            # if the user was a member of the room at the time of the event,
            # they can see it.
            if membership == Membership.JOIN:
                return True

            if visibility == "joined":
                # we weren't a member at the time of the event, so we can't
                # see this event.
                return False

            elif visibility == "invited":
                # user can also see the event if they were *invited* at the time
                # of the event.
                return membership == Membership.INVITE

            else:
                # visibility is shared: user can also see the event if they have
                # become a member since the event
                #
                # XXX: if the user has subsequently joined and then left again,
                # ideally we would share history up to the point they left. But
                # we don't know when they left.
                return not is_peeking

        defer.returnValue({
            user_id: [
                event
                for event in events
                if allowed(event, user_id, is_peeking, ignore_dict.get(user_id, []))
            ]
            for user_id, is_peeking in user_tuples
        })

    @defer.inlineCallbacks
    def filter_events_for_client(self, user_id, events, is_peeking=False):
        """
        Check which events a user is allowed to see

        Args:
            user_id(str): user id to be checked
            events([synapse.events.EventBase]): list of events to be checked
            is_peeking(bool): should be True if:
              * the user is not currently a member of the room, and:
              * the user has not been a member of the room since the given
                events

        Returns:
            [synapse.events.EventBase]
        """
        types = (
            (EventTypes.RoomHistoryVisibility, ""),
            (EventTypes.Member, user_id),
        )
        event_id_to_state = yield self.store.get_state_for_events(
            frozenset(e.event_id for e in events),
            types=types
        )
        res = yield self.filter_events_for_clients(
            [(user_id, is_peeking)], events, event_id_to_state
        )
        defer.returnValue(res.get(user_id, []))

    def ratelimit(self, requester):
        time_now = self.clock.time()
        allowed, time_allowed = self.ratelimiter.send_message(
            requester.user.to_string(), time_now,
            msg_rate_hz=self.hs.config.rc_messages_per_second,
            burst_count=self.hs.config.rc_message_burst_count,
        )
        if not allowed:
            raise LimitExceededError(
                retry_after_ms=int(1000 * (time_allowed - time_now)),
            )

    def is_host_in_room(self, current_state):
        room_members = [
            (state_key, event.membership)
            for ((event_type, state_key), event) in current_state.items()
            if event_type == EventTypes.Member
        ]
        if len(room_members) == 0:
            # Have we just created the room, and is this about to be the very
            # first member event?
            create_event = current_state.get(("m.room.create", ""))
            if create_event:
                return True
        for (state_key, membership) in room_members:
            if (
                self.hs.is_mine_id(state_key)
                and membership == Membership.JOIN
            ):
                return True
        return False

    @defer.inlineCallbacks
    def maybe_kick_guest_users(self, event, current_state):
        # Technically this function invalidates current_state by changing it.
        # Hopefully this isn't that important to the caller.
        if event.type == EventTypes.GuestAccess:
            guest_access = event.content.get("guest_access", "forbidden")
            if guest_access != "can_join":
                yield self.kick_guest_users(current_state)

    @defer.inlineCallbacks
    def kick_guest_users(self, current_state):
        for member_event in current_state:
            try:
                if member_event.type != EventTypes.Member:
                    continue

                target_user = UserID.from_string(member_event.state_key)
                if not self.hs.is_mine(target_user):
                    continue

                if member_event.content["membership"] not in {
                    Membership.JOIN,
                    Membership.INVITE
                }:
                    continue

                if (
                    "kind" not in member_event.content
                    or member_event.content["kind"] != "guest"
                ):
                    continue

                # We make the user choose to leave, rather than have the
                # event-sender kick them. This is partially because we don't
                # need to worry about power levels, and partially because guest
                # users are a concept which doesn't hugely work over federation,
                # and having homeservers have their own users leave keeps more
                # of that decision-making and control local to the guest-having
                # homeserver.
                requester = Requester(target_user, "", True)
                handler = self.hs.get_handlers().room_member_handler
                yield handler.update_membership(
                    requester,
                    target_user,
                    member_event.room_id,
                    "leave",
                    ratelimit=False,
                )
            except Exception as e:
                logger.warn("Error kicking guest user: %s" % (e,))