summary refs log tree commit diff
path: root/synapse/handlers/room_member.py
blob: 0080eeaf8dbf3578383de761719789fa5c1b1fb3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
# -*- coding: utf-8 -*-
# Copyright 2016-2020 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import abc
import logging
import random
from http import HTTPStatus
from typing import TYPE_CHECKING, Iterable, List, Optional, Tuple, Union

from unpaddedbase64 import encode_base64

from synapse import types
from synapse.api.constants import MAX_DEPTH, AccountDataTypes, EventTypes, Membership
from synapse.api.errors import (
    AuthError,
    Codes,
    LimitExceededError,
    ShadowBanError,
    SynapseError,
)
from synapse.api.ratelimiting import Ratelimiter
from synapse.api.room_versions import EventFormatVersions
from synapse.crypto.event_signing import compute_event_reference_hash
from synapse.events import EventBase
from synapse.events.builder import create_local_event_from_event_dict
from synapse.events.snapshot import EventContext
from synapse.events.validator import EventValidator
from synapse.storage.roommember import RoomsForUser
from synapse.types import JsonDict, Requester, RoomAlias, RoomID, StateMap, UserID
from synapse.util.async_helpers import Linearizer
from synapse.util.distributor import user_left_room

from ._base import BaseHandler

if TYPE_CHECKING:
    from synapse.server import HomeServer


logger = logging.getLogger(__name__)


class RoomMemberHandler(metaclass=abc.ABCMeta):
    # TODO(paul): This handler currently contains a messy conflation of
    #   low-level API that works on UserID objects and so on, and REST-level
    #   API that takes ID strings and returns pagination chunks. These concerns
    #   ought to be separated out a lot better.

    def __init__(self, hs: "HomeServer"):
        self.hs = hs
        self.store = hs.get_datastore()
        self.auth = hs.get_auth()
        self.state_handler = hs.get_state_handler()
        self.config = hs.config

        self.federation_handler = hs.get_federation_handler()
        self.directory_handler = hs.get_directory_handler()
        self.identity_handler = hs.get_identity_handler()
        self.registration_handler = hs.get_registration_handler()
        self.profile_handler = hs.get_profile_handler()
        self.event_creation_handler = hs.get_event_creation_handler()

        self.member_linearizer = Linearizer(name="member")

        self.clock = hs.get_clock()
        self.spam_checker = hs.get_spam_checker()
        self.third_party_event_rules = hs.get_third_party_event_rules()
        self._server_notices_mxid = self.config.server_notices_mxid
        self._enable_lookup = hs.config.enable_3pid_lookup
        self.allow_per_room_profiles = self.config.allow_per_room_profiles

        self._join_rate_limiter_local = Ratelimiter(
            clock=self.clock,
            rate_hz=hs.config.ratelimiting.rc_joins_local.per_second,
            burst_count=hs.config.ratelimiting.rc_joins_local.burst_count,
        )
        self._join_rate_limiter_remote = Ratelimiter(
            clock=self.clock,
            rate_hz=hs.config.ratelimiting.rc_joins_remote.per_second,
            burst_count=hs.config.ratelimiting.rc_joins_remote.burst_count,
        )

        # This is only used to get at ratelimit function, and
        # maybe_kick_guest_users. It's fine there are multiple of these as
        # it doesn't store state.
        self.base_handler = BaseHandler(hs)

    @abc.abstractmethod
    async def _remote_join(
        self,
        requester: Requester,
        remote_room_hosts: List[str],
        room_id: str,
        user: UserID,
        content: dict,
    ) -> Tuple[str, int]:
        """Try and join a room that this server is not in

        Args:
            requester
            remote_room_hosts: List of servers that can be used to join via.
            room_id: Room that we are trying to join
            user: User who is trying to join
            content: A dict that should be used as the content of the join event.
        """
        raise NotImplementedError()

    @abc.abstractmethod
    async def remote_reject_invite(
        self,
        invite_event_id: str,
        txn_id: Optional[str],
        requester: Requester,
        content: JsonDict,
    ) -> Tuple[str, int]:
        """
        Rejects an out-of-band invite we have received from a remote server

        Args:
            invite_event_id: ID of the invite to be rejected
            txn_id: optional transaction ID supplied by the client
            requester: user making the rejection request, according to the access token
            content: additional content to include in the rejection event.
               Normally an empty dict.

        Returns:
            event id, stream_id of the leave event
        """
        raise NotImplementedError()

    @abc.abstractmethod
    async def _user_left_room(self, target: UserID, room_id: str) -> None:
        """Notifies distributor on master process that the user has left the
        room.

        Args:
            target
            room_id
        """
        raise NotImplementedError()

    async def _local_membership_update(
        self,
        requester: Requester,
        target: UserID,
        room_id: str,
        membership: str,
        prev_event_ids: List[str],
        txn_id: Optional[str] = None,
        ratelimit: bool = True,
        content: Optional[dict] = None,
        require_consent: bool = True,
    ) -> Tuple[str, int]:
        user_id = target.to_string()

        if content is None:
            content = {}

        content["membership"] = membership
        if requester.is_guest:
            content["kind"] = "guest"

        # Check if we already have an event with a matching transaction ID. (We
        # do this check just before we persist an event as well, but may as well
        # do it up front for efficiency.)
        if txn_id and requester.access_token_id:
            existing_event_id = await self.store.get_event_id_from_transaction_id(
                room_id, requester.user.to_string(), requester.access_token_id, txn_id,
            )
            if existing_event_id:
                event_pos = await self.store.get_position_for_event(existing_event_id)
                return existing_event_id, event_pos.stream

        event, context = await self.event_creation_handler.create_event(
            requester,
            {
                "type": EventTypes.Member,
                "content": content,
                "room_id": room_id,
                "sender": requester.user.to_string(),
                "state_key": user_id,
                # For backwards compatibility:
                "membership": membership,
            },
            token_id=requester.access_token_id,
            txn_id=txn_id,
            prev_event_ids=prev_event_ids,
            require_consent=require_consent,
        )

        prev_state_ids = await context.get_prev_state_ids()

        prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)

        if event.membership == Membership.JOIN:
            newly_joined = True
            if prev_member_event_id:
                prev_member_event = await self.store.get_event(prev_member_event_id)
                newly_joined = prev_member_event.membership != Membership.JOIN

            # Only rate-limit if the user actually joined the room, otherwise we'll end
            # up blocking profile updates.
            if newly_joined:
                time_now_s = self.clock.time()
                (
                    allowed,
                    time_allowed,
                ) = self._join_rate_limiter_local.can_requester_do_action(requester)

                if not allowed:
                    raise LimitExceededError(
                        retry_after_ms=int(1000 * (time_allowed - time_now_s))
                    )

        result_event = await self.event_creation_handler.handle_new_client_event(
            requester, event, context, extra_users=[target], ratelimit=ratelimit,
        )

        if event.membership == Membership.LEAVE:
            if prev_member_event_id:
                prev_member_event = await self.store.get_event(prev_member_event_id)
                if prev_member_event.membership == Membership.JOIN:
                    await self._user_left_room(target, room_id)

        # we know it was persisted, so should have a stream ordering
        assert result_event.internal_metadata.stream_ordering
        return result_event.event_id, result_event.internal_metadata.stream_ordering

    async def copy_room_tags_and_direct_to_room(
        self, old_room_id, new_room_id, user_id
    ) -> None:
        """Copies the tags and direct room state from one room to another.

        Args:
            old_room_id: The room ID of the old room.
            new_room_id: The room ID of the new room.
            user_id: The user's ID.
        """
        # Retrieve user account data for predecessor room
        user_account_data, _ = await self.store.get_account_data_for_user(user_id)

        # Copy direct message state if applicable
        direct_rooms = user_account_data.get(AccountDataTypes.DIRECT, {})

        # Check which key this room is under
        if isinstance(direct_rooms, dict):
            for key, room_id_list in direct_rooms.items():
                if old_room_id in room_id_list and new_room_id not in room_id_list:
                    # Add new room_id to this key
                    direct_rooms[key].append(new_room_id)

                    # Save back to user's m.direct account data
                    await self.store.add_account_data_for_user(
                        user_id, AccountDataTypes.DIRECT, direct_rooms
                    )
                    break

        # Copy room tags if applicable
        room_tags = await self.store.get_tags_for_room(user_id, old_room_id)

        # Copy each room tag to the new room
        for tag, tag_content in room_tags.items():
            await self.store.add_tag_to_room(user_id, new_room_id, tag, tag_content)

    async def update_membership(
        self,
        requester: Requester,
        target: UserID,
        room_id: str,
        action: str,
        txn_id: Optional[str] = None,
        remote_room_hosts: Optional[List[str]] = None,
        third_party_signed: Optional[dict] = None,
        ratelimit: bool = True,
        content: Optional[dict] = None,
        require_consent: bool = True,
    ) -> Tuple[str, int]:
        """Update a user's membership in a room.

        Params:
            requester: The user who is performing the update.
            target: The user whose membership is being updated.
            room_id: The room ID whose membership is being updated.
            action: The membership change, see synapse.api.constants.Membership.
            txn_id: The transaction ID, if given.
            remote_room_hosts: Remote servers to send the update to.
            third_party_signed: Information from a 3PID invite.
            ratelimit: Whether to rate limit the request.
            content: The content of the created event.
            require_consent: Whether consent is required.

        Returns:
            A tuple of the new event ID and stream ID.

        Raises:
            ShadowBanError if a shadow-banned requester attempts to send an invite.
        """
        if action == Membership.INVITE and requester.shadow_banned:
            # We randomly sleep a bit just to annoy the requester.
            await self.clock.sleep(random.randint(1, 10))
            raise ShadowBanError()

        key = (room_id,)

        with (await self.member_linearizer.queue(key)):
            result = await self._update_membership(
                requester,
                target,
                room_id,
                action,
                txn_id=txn_id,
                remote_room_hosts=remote_room_hosts,
                third_party_signed=third_party_signed,
                ratelimit=ratelimit,
                content=content,
                require_consent=require_consent,
            )

        return result

    async def _update_membership(
        self,
        requester: Requester,
        target: UserID,
        room_id: str,
        action: str,
        txn_id: Optional[str] = None,
        remote_room_hosts: Optional[List[str]] = None,
        third_party_signed: Optional[dict] = None,
        ratelimit: bool = True,
        content: Optional[dict] = None,
        require_consent: bool = True,
    ) -> Tuple[str, int]:
        content_specified = bool(content)
        if content is None:
            content = {}
        else:
            # We do a copy here as we potentially change some keys
            # later on.
            content = dict(content)

        if not self.allow_per_room_profiles or requester.shadow_banned:
            # Strip profile data, knowing that new profile data will be added to the
            # event's content in event_creation_handler.create_event() using the target's
            # global profile.
            content.pop("displayname", None)
            content.pop("avatar_url", None)

        effective_membership_state = action
        if action in ["kick", "unban"]:
            effective_membership_state = "leave"

        # if this is a join with a 3pid signature, we may need to turn a 3pid
        # invite into a normal invite before we can handle the join.
        if third_party_signed is not None:
            await self.federation_handler.exchange_third_party_invite(
                third_party_signed["sender"],
                target.to_string(),
                room_id,
                third_party_signed,
            )

        if not remote_room_hosts:
            remote_room_hosts = []

        if effective_membership_state not in ("leave", "ban"):
            is_blocked = await self.store.is_room_blocked(room_id)
            if is_blocked:
                raise SynapseError(403, "This room has been blocked on this server")

        if effective_membership_state == Membership.INVITE:
            # block any attempts to invite the server notices mxid
            if target.to_string() == self._server_notices_mxid:
                raise SynapseError(HTTPStatus.FORBIDDEN, "Cannot invite this user")

            block_invite = False

            if (
                self._server_notices_mxid is not None
                and requester.user.to_string() == self._server_notices_mxid
            ):
                # allow the server notices mxid to send invites
                is_requester_admin = True

            else:
                is_requester_admin = await self.auth.is_server_admin(requester.user)

            if not is_requester_admin:
                if self.config.block_non_admin_invites:
                    logger.info(
                        "Blocking invite: user is not admin and non-admin "
                        "invites disabled"
                    )
                    block_invite = True

                if not self.spam_checker.user_may_invite(
                    requester.user.to_string(), target.to_string(), room_id
                ):
                    logger.info("Blocking invite due to spam checker")
                    block_invite = True

            if block_invite:
                raise SynapseError(403, "Invites have been disabled on this server")

        latest_event_ids = await self.store.get_prev_events_for_room(room_id)

        current_state_ids = await self.state_handler.get_current_state_ids(
            room_id, latest_event_ids=latest_event_ids
        )

        # TODO: Refactor into dictionary of explicitly allowed transitions
        # between old and new state, with specific error messages for some
        # transitions and generic otherwise
        old_state_id = current_state_ids.get((EventTypes.Member, target.to_string()))
        if old_state_id:
            old_state = await self.store.get_event(old_state_id, allow_none=True)
            old_membership = old_state.content.get("membership") if old_state else None
            if action == "unban" and old_membership != "ban":
                raise SynapseError(
                    403,
                    "Cannot unban user who was not banned"
                    " (membership=%s)" % old_membership,
                    errcode=Codes.BAD_STATE,
                )
            if old_membership == "ban" and action != "unban":
                raise SynapseError(
                    403,
                    "Cannot %s user who was banned" % (action,),
                    errcode=Codes.BAD_STATE,
                )

            if old_state:
                same_content = content == old_state.content
                same_membership = old_membership == effective_membership_state
                same_sender = requester.user.to_string() == old_state.sender
                if same_sender and same_membership and same_content:
                    # duplicate event.
                    # we know it was persisted, so must have a stream ordering.
                    assert old_state.internal_metadata.stream_ordering
                    return (
                        old_state.event_id,
                        old_state.internal_metadata.stream_ordering,
                    )

            if old_membership in ["ban", "leave"] and action == "kick":
                raise AuthError(403, "The target user is not in the room")

            # we don't allow people to reject invites to the server notice
            # room, but they can leave it once they are joined.
            if (
                old_membership == Membership.INVITE
                and effective_membership_state == Membership.LEAVE
            ):
                is_blocked = await self._is_server_notice_room(room_id)
                if is_blocked:
                    raise SynapseError(
                        HTTPStatus.FORBIDDEN,
                        "You cannot reject this invite",
                        errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
                    )
        else:
            if action == "kick":
                raise AuthError(403, "The target user is not in the room")

        is_host_in_room = await self._is_host_in_room(current_state_ids)

        if effective_membership_state == Membership.JOIN:
            if requester.is_guest:
                guest_can_join = await self._can_guest_join(current_state_ids)
                if not guest_can_join:
                    # This should be an auth check, but guests are a local concept,
                    # so don't really fit into the general auth process.
                    raise AuthError(403, "Guest access not allowed")

            if not is_host_in_room:
                time_now_s = self.clock.time()
                (
                    allowed,
                    time_allowed,
                ) = self._join_rate_limiter_remote.can_requester_do_action(requester,)

                if not allowed:
                    raise LimitExceededError(
                        retry_after_ms=int(1000 * (time_allowed - time_now_s))
                    )

                inviter = await self._get_inviter(target.to_string(), room_id)
                if inviter and not self.hs.is_mine(inviter):
                    remote_room_hosts.append(inviter.domain)

                content["membership"] = Membership.JOIN

                profile = self.profile_handler
                if not content_specified:
                    content["displayname"] = await profile.get_displayname(target)
                    content["avatar_url"] = await profile.get_avatar_url(target)

                if requester.is_guest:
                    content["kind"] = "guest"

                remote_join_response = await self._remote_join(
                    requester, remote_room_hosts, room_id, target, content
                )

                return remote_join_response

        elif effective_membership_state == Membership.LEAVE:
            if not is_host_in_room:
                # perhaps we've been invited
                invite = await self.store.get_invite_for_local_user_in_room(
                    user_id=target.to_string(), room_id=room_id
                )  # type: Optional[RoomsForUser]
                if not invite:
                    logger.info(
                        "%s sent a leave request to %s, but that is not an active room "
                        "on this server, and there is no pending invite",
                        target,
                        room_id,
                    )

                    raise SynapseError(404, "Not a known room")

                logger.info(
                    "%s rejects invite to %s from %s", target, room_id, invite.sender
                )

                if not self.hs.is_mine_id(invite.sender):
                    # send the rejection to the inviter's HS (with fallback to
                    # local event)
                    return await self.remote_reject_invite(
                        invite.event_id, txn_id, requester, content,
                    )

                # the inviter was on our server, but has now left. Carry on
                # with the normal rejection codepath, which will also send the
                # rejection out to any other servers we believe are still in the room.

                # thanks to overzealous cleaning up of event_forward_extremities in
                # `delete_old_current_state_events`, it's possible to end up with no
                # forward extremities here. If that happens, let's just hang the
                # rejection off the invite event.
                #
                # see: https://github.com/matrix-org/synapse/issues/7139
                if len(latest_event_ids) == 0:
                    latest_event_ids = [invite.event_id]

        return await self._local_membership_update(
            requester=requester,
            target=target,
            room_id=room_id,
            membership=effective_membership_state,
            txn_id=txn_id,
            ratelimit=ratelimit,
            prev_event_ids=latest_event_ids,
            content=content,
            require_consent=require_consent,
        )

    async def transfer_room_state_on_room_upgrade(
        self, old_room_id: str, room_id: str
    ) -> None:
        """Upon our server becoming aware of an upgraded room, either by upgrading a room
        ourselves or joining one, we can transfer over information from the previous room.

        Copies user state (tags/push rules) for every local user that was in the old room, as
        well as migrating the room directory state.

        Args:
            old_room_id: The ID of the old room
            room_id: The ID of the new room
        """
        logger.info("Transferring room state from %s to %s", old_room_id, room_id)

        # Find all local users that were in the old room and copy over each user's state
        users = await self.store.get_users_in_room(old_room_id)
        await self.copy_user_state_on_room_upgrade(old_room_id, room_id, users)

        # Add new room to the room directory if the old room was there
        # Remove old room from the room directory
        old_room = await self.store.get_room(old_room_id)
        if old_room and old_room["is_public"]:
            await self.store.set_room_is_public(old_room_id, False)
            await self.store.set_room_is_public(room_id, True)

        # Transfer alias mappings in the room directory
        await self.store.update_aliases_for_room(old_room_id, room_id)

        # Check if any groups we own contain the predecessor room
        local_group_ids = await self.store.get_local_groups_for_room(old_room_id)
        for group_id in local_group_ids:
            # Add new the new room to those groups
            await self.store.add_room_to_group(group_id, room_id, old_room["is_public"])

            # Remove the old room from those groups
            await self.store.remove_room_from_group(group_id, old_room_id)

    async def copy_user_state_on_room_upgrade(
        self, old_room_id: str, new_room_id: str, user_ids: Iterable[str]
    ) -> None:
        """Copy user-specific information when they join a new room when that new room is the
        result of a room upgrade

        Args:
            old_room_id: The ID of upgraded room
            new_room_id: The ID of the new room
            user_ids: User IDs to copy state for
        """

        logger.debug(
            "Copying over room tags and push rules from %s to %s for users %s",
            old_room_id,
            new_room_id,
            user_ids,
        )

        for user_id in user_ids:
            try:
                # It is an upgraded room. Copy over old tags
                await self.copy_room_tags_and_direct_to_room(
                    old_room_id, new_room_id, user_id
                )
                # Copy over push rules
                await self.store.copy_push_rules_from_room_to_room_for_user(
                    old_room_id, new_room_id, user_id
                )
            except Exception:
                logger.exception(
                    "Error copying tags and/or push rules from rooms %s to %s for user %s. "
                    "Skipping...",
                    old_room_id,
                    new_room_id,
                    user_id,
                )
                continue

    async def send_membership_event(
        self,
        requester: Optional[Requester],
        event: EventBase,
        context: EventContext,
        ratelimit: bool = True,
    ):
        """
        Change the membership status of a user in a room.

        Args:
            requester: The local user who requested the membership
                event. If None, certain checks, like whether this homeserver can
                act as the sender, will be skipped.
            event: The membership event.
            context: The context of the event.
            ratelimit: Whether to rate limit this request.
        Raises:
            SynapseError if there was a problem changing the membership.
        """
        target_user = UserID.from_string(event.state_key)
        room_id = event.room_id

        if requester is not None:
            sender = UserID.from_string(event.sender)
            assert (
                sender == requester.user
            ), "Sender (%s) must be same as requester (%s)" % (sender, requester.user)
            assert self.hs.is_mine(sender), "Sender must be our own: %s" % (sender,)
        else:
            requester = types.create_requester(target_user)

        prev_state_ids = await context.get_prev_state_ids()
        if event.membership == Membership.JOIN:
            if requester.is_guest:
                guest_can_join = await self._can_guest_join(prev_state_ids)
                if not guest_can_join:
                    # This should be an auth check, but guests are a local concept,
                    # so don't really fit into the general auth process.
                    raise AuthError(403, "Guest access not allowed")

        if event.membership not in (Membership.LEAVE, Membership.BAN):
            is_blocked = await self.store.is_room_blocked(room_id)
            if is_blocked:
                raise SynapseError(403, "This room has been blocked on this server")

        event = await self.event_creation_handler.handle_new_client_event(
            requester, event, context, extra_users=[target_user], ratelimit=ratelimit
        )

        prev_member_event_id = prev_state_ids.get(
            (EventTypes.Member, event.state_key), None
        )

        if event.membership == Membership.LEAVE:
            if prev_member_event_id:
                prev_member_event = await self.store.get_event(prev_member_event_id)
                if prev_member_event.membership == Membership.JOIN:
                    await self._user_left_room(target_user, room_id)

    async def _can_guest_join(self, current_state_ids: StateMap[str]) -> bool:
        """
        Returns whether a guest can join a room based on its current state.
        """
        guest_access_id = current_state_ids.get((EventTypes.GuestAccess, ""), None)
        if not guest_access_id:
            return False

        guest_access = await self.store.get_event(guest_access_id)

        return bool(
            guest_access
            and guest_access.content
            and "guest_access" in guest_access.content
            and guest_access.content["guest_access"] == "can_join"
        )

    async def lookup_room_alias(
        self, room_alias: RoomAlias
    ) -> Tuple[RoomID, List[str]]:
        """
        Get the room ID associated with a room alias.

        Args:
            room_alias: The alias to look up.
        Returns:
            A tuple of:
                The room ID as a RoomID object.
                Hosts likely to be participating in the room ([str]).
        Raises:
            SynapseError if room alias could not be found.
        """
        directory_handler = self.directory_handler
        mapping = await directory_handler.get_association(room_alias)

        if not mapping:
            raise SynapseError(404, "No such room alias")

        room_id = mapping["room_id"]
        servers = mapping["servers"]

        # put the server which owns the alias at the front of the server list.
        if room_alias.domain in servers:
            servers.remove(room_alias.domain)
        servers.insert(0, room_alias.domain)

        return RoomID.from_string(room_id), servers

    async def _get_inviter(self, user_id: str, room_id: str) -> Optional[UserID]:
        invite = await self.store.get_invite_for_local_user_in_room(
            user_id=user_id, room_id=room_id
        )
        if invite:
            return UserID.from_string(invite.sender)
        return None

    async def do_3pid_invite(
        self,
        room_id: str,
        inviter: UserID,
        medium: str,
        address: str,
        id_server: str,
        requester: Requester,
        txn_id: Optional[str],
        id_access_token: Optional[str] = None,
    ) -> int:
        """Invite a 3PID to a room.

        Args:
            room_id: The room to invite the 3PID to.
            inviter: The user sending the invite.
            medium: The 3PID's medium.
            address: The 3PID's address.
            id_server: The identity server to use.
            requester: The user making the request.
            txn_id: The transaction ID this is part of, or None if this is not
                part of a transaction.
            id_access_token: The optional identity server access token.

        Returns:
             The new stream ID.

        Raises:
            ShadowBanError if the requester has been shadow-banned.
        """
        if self.config.block_non_admin_invites:
            is_requester_admin = await self.auth.is_server_admin(requester.user)
            if not is_requester_admin:
                raise SynapseError(
                    403, "Invites have been disabled on this server", Codes.FORBIDDEN
                )

        if requester.shadow_banned:
            # We randomly sleep a bit just to annoy the requester.
            await self.clock.sleep(random.randint(1, 10))
            raise ShadowBanError()

        # We need to rate limit *before* we send out any 3PID invites, so we
        # can't just rely on the standard ratelimiting of events.
        await self.base_handler.ratelimit(requester)

        can_invite = await self.third_party_event_rules.check_threepid_can_be_invited(
            medium, address, room_id
        )
        if not can_invite:
            raise SynapseError(
                403,
                "This third-party identifier can not be invited in this room",
                Codes.FORBIDDEN,
            )

        if not self._enable_lookup:
            raise SynapseError(
                403, "Looking up third-party identifiers is denied from this server"
            )

        invitee = await self.identity_handler.lookup_3pid(
            id_server, medium, address, id_access_token
        )

        if invitee:
            # Note that update_membership with an action of "invite" can raise
            # a ShadowBanError, but this was done above already.
            _, stream_id = await self.update_membership(
                requester, UserID.from_string(invitee), room_id, "invite", txn_id=txn_id
            )
        else:
            stream_id = await self._make_and_store_3pid_invite(
                requester,
                id_server,
                medium,
                address,
                room_id,
                inviter,
                txn_id=txn_id,
                id_access_token=id_access_token,
            )

        return stream_id

    async def _make_and_store_3pid_invite(
        self,
        requester: Requester,
        id_server: str,
        medium: str,
        address: str,
        room_id: str,
        user: UserID,
        txn_id: Optional[str],
        id_access_token: Optional[str] = None,
    ) -> int:
        room_state = await self.state_handler.get_current_state(room_id)

        inviter_display_name = ""
        inviter_avatar_url = ""
        member_event = room_state.get((EventTypes.Member, user.to_string()))
        if member_event:
            inviter_display_name = member_event.content.get("displayname", "")
            inviter_avatar_url = member_event.content.get("avatar_url", "")

        # if user has no display name, default to their MXID
        if not inviter_display_name:
            inviter_display_name = user.to_string()

        canonical_room_alias = ""
        canonical_alias_event = room_state.get((EventTypes.CanonicalAlias, ""))
        if canonical_alias_event:
            canonical_room_alias = canonical_alias_event.content.get("alias", "")

        room_name = ""
        room_name_event = room_state.get((EventTypes.Name, ""))
        if room_name_event:
            room_name = room_name_event.content.get("name", "")

        room_join_rules = ""
        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
        if join_rules_event:
            room_join_rules = join_rules_event.content.get("join_rule", "")

        room_avatar_url = ""
        room_avatar_event = room_state.get((EventTypes.RoomAvatar, ""))
        if room_avatar_event:
            room_avatar_url = room_avatar_event.content.get("url", "")

        (
            token,
            public_keys,
            fallback_public_key,
            display_name,
        ) = await self.identity_handler.ask_id_server_for_third_party_invite(
            requester=requester,
            id_server=id_server,
            medium=medium,
            address=address,
            room_id=room_id,
            inviter_user_id=user.to_string(),
            room_alias=canonical_room_alias,
            room_avatar_url=room_avatar_url,
            room_join_rules=room_join_rules,
            room_name=room_name,
            inviter_display_name=inviter_display_name,
            inviter_avatar_url=inviter_avatar_url,
            id_access_token=id_access_token,
        )

        (
            event,
            stream_id,
        ) = await self.event_creation_handler.create_and_send_nonmember_event(
            requester,
            {
                "type": EventTypes.ThirdPartyInvite,
                "content": {
                    "display_name": display_name,
                    "public_keys": public_keys,
                    # For backwards compatibility:
                    "key_validity_url": fallback_public_key["key_validity_url"],
                    "public_key": fallback_public_key["public_key"],
                },
                "room_id": room_id,
                "sender": user.to_string(),
                "state_key": token,
            },
            ratelimit=False,
            txn_id=txn_id,
        )
        return stream_id

    async def _is_host_in_room(self, current_state_ids: StateMap[str]) -> bool:
        # Have we just created the room, and is this about to be the very
        # first member event?
        create_event_id = current_state_ids.get(("m.room.create", ""))
        if len(current_state_ids) == 1 and create_event_id:
            # We can only get here if we're in the process of creating the room
            return True

        for etype, state_key in current_state_ids:
            if etype != EventTypes.Member or not self.hs.is_mine_id(state_key):
                continue

            event_id = current_state_ids[(etype, state_key)]
            event = await self.store.get_event(event_id, allow_none=True)
            if not event:
                continue

            if event.membership == Membership.JOIN:
                return True

        return False

    async def _is_server_notice_room(self, room_id: str) -> bool:
        if self._server_notices_mxid is None:
            return False
        user_ids = await self.store.get_users_in_room(room_id)
        return self._server_notices_mxid in user_ids


class RoomMemberMasterHandler(RoomMemberHandler):
    def __init__(self, hs):
        super().__init__(hs)

        self.distributor = hs.get_distributor()
        self.distributor.declare("user_left_room")

    async def _is_remote_room_too_complex(
        self, room_id: str, remote_room_hosts: List[str]
    ) -> Optional[bool]:
        """
        Check if complexity of a remote room is too great.

        Args:
            room_id
            remote_room_hosts

        Returns: bool of whether the complexity is too great, or None
            if unable to be fetched
        """
        max_complexity = self.hs.config.limit_remote_rooms.complexity
        complexity = await self.federation_handler.get_room_complexity(
            remote_room_hosts, room_id
        )

        if complexity:
            return complexity["v1"] > max_complexity
        return None

    async def _is_local_room_too_complex(self, room_id: str) -> bool:
        """
        Check if the complexity of a local room is too great.

        Args:
            room_id: The room ID to check for complexity.
        """
        max_complexity = self.hs.config.limit_remote_rooms.complexity
        complexity = await self.store.get_room_complexity(room_id)

        return complexity["v1"] > max_complexity

    async def _remote_join(
        self,
        requester: Requester,
        remote_room_hosts: List[str],
        room_id: str,
        user: UserID,
        content: dict,
    ) -> Tuple[str, int]:
        """Implements RoomMemberHandler._remote_join
        """
        # filter ourselves out of remote_room_hosts: do_invite_join ignores it
        # and if it is the only entry we'd like to return a 404 rather than a
        # 500.
        remote_room_hosts = [
            host for host in remote_room_hosts if host != self.hs.hostname
        ]

        if len(remote_room_hosts) == 0:
            raise SynapseError(404, "No known servers")

        check_complexity = self.hs.config.limit_remote_rooms.enabled
        if check_complexity and self.hs.config.limit_remote_rooms.admins_can_join:
            check_complexity = not await self.auth.is_server_admin(user)

        if check_complexity:
            # Fetch the room complexity
            too_complex = await self._is_remote_room_too_complex(
                room_id, remote_room_hosts
            )
            if too_complex is True:
                raise SynapseError(
                    code=400,
                    msg=self.hs.config.limit_remote_rooms.complexity_error,
                    errcode=Codes.RESOURCE_LIMIT_EXCEEDED,
                )

        # We don't do an auth check if we are doing an invite
        # join dance for now, since we're kinda implicitly checking
        # that we are allowed to join when we decide whether or not we
        # need to do the invite/join dance.
        event_id, stream_id = await self.federation_handler.do_invite_join(
            remote_room_hosts, room_id, user.to_string(), content
        )

        # Check the room we just joined wasn't too large, if we didn't fetch the
        # complexity of it before.
        if check_complexity:
            if too_complex is False:
                # We checked, and we're under the limit.
                return event_id, stream_id

            # Check again, but with the local state events
            too_complex = await self._is_local_room_too_complex(room_id)

            if too_complex is False:
                # We're under the limit.
                return event_id, stream_id

            # The room is too large. Leave.
            requester = types.create_requester(user, None, False, False, None)
            await self.update_membership(
                requester=requester, target=user, room_id=room_id, action="leave"
            )
            raise SynapseError(
                code=400,
                msg=self.hs.config.limit_remote_rooms.complexity_error,
                errcode=Codes.RESOURCE_LIMIT_EXCEEDED,
            )

        return event_id, stream_id

    async def remote_reject_invite(
        self,
        invite_event_id: str,
        txn_id: Optional[str],
        requester: Requester,
        content: JsonDict,
    ) -> Tuple[str, int]:
        """
        Rejects an out-of-band invite received from a remote user

        Implements RoomMemberHandler.remote_reject_invite
        """
        invite_event = await self.store.get_event(invite_event_id)
        room_id = invite_event.room_id
        target_user = invite_event.state_key

        # first of all, try doing a rejection via the inviting server
        fed_handler = self.federation_handler
        try:
            inviter_id = UserID.from_string(invite_event.sender)
            event, stream_id = await fed_handler.do_remotely_reject_invite(
                [inviter_id.domain], room_id, target_user, content=content
            )
            return event.event_id, stream_id
        except Exception as e:
            # if we were unable to reject the invite, we will generate our own
            # leave event.
            #
            # The 'except' clause is very broad, but we need to
            # capture everything from DNS failures upwards
            #
            logger.warning("Failed to reject invite: %s", e)

            return await self._locally_reject_invite(
                invite_event, txn_id, requester, content
            )

    async def _locally_reject_invite(
        self,
        invite_event: EventBase,
        txn_id: Optional[str],
        requester: Requester,
        content: JsonDict,
    ) -> Tuple[str, int]:
        """Generate a local invite rejection

        This is called after we fail to reject an invite via a remote server. It
        generates an out-of-band membership event locally.

        Args:
            invite_event: the invite to be rejected
            txn_id: optional transaction ID supplied by the client
            requester:  user making the rejection request, according to the access token
            content: additional content to include in the rejection event.
               Normally an empty dict.
        """

        room_id = invite_event.room_id
        target_user = invite_event.state_key
        room_version = await self.store.get_room_version(room_id)

        content["membership"] = Membership.LEAVE

        # the auth events for the new event are the same as that of the invite, plus
        # the invite itself.
        #
        # the prev_events are just the invite.
        invite_hash = invite_event.event_id  # type: Union[str, Tuple]
        if room_version.event_format == EventFormatVersions.V1:
            alg, h = compute_event_reference_hash(invite_event)
            invite_hash = (invite_event.event_id, {alg: encode_base64(h)})

        auth_events = tuple(invite_event.auth_events) + (invite_hash,)
        prev_events = (invite_hash,)

        # we cap depth of generated events, to ensure that they are not
        # rejected by other servers (and so that they can be persisted in
        # the db)
        depth = min(invite_event.depth + 1, MAX_DEPTH)

        event_dict = {
            "depth": depth,
            "auth_events": auth_events,
            "prev_events": prev_events,
            "type": EventTypes.Member,
            "room_id": room_id,
            "sender": target_user,
            "content": content,
            "state_key": target_user,
        }

        event = create_local_event_from_event_dict(
            clock=self.clock,
            hostname=self.hs.hostname,
            signing_key=self.hs.signing_key,
            room_version=room_version,
            event_dict=event_dict,
        )
        event.internal_metadata.outlier = True
        event.internal_metadata.out_of_band_membership = True
        if txn_id is not None:
            event.internal_metadata.txn_id = txn_id
        if requester.access_token_id is not None:
            event.internal_metadata.token_id = requester.access_token_id

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

        context = await self.state_handler.compute_event_context(event)
        context.app_service = requester.app_service
        result_event = await self.event_creation_handler.handle_new_client_event(
            requester, event, context, extra_users=[UserID.from_string(target_user)],
        )
        # we know it was persisted, so must have a stream ordering
        assert result_event.internal_metadata.stream_ordering

        return result_event.event_id, result_event.internal_metadata.stream_ordering

    async def _user_left_room(self, target: UserID, room_id: str) -> None:
        """Implements RoomMemberHandler._user_left_room
        """
        user_left_room(self.distributor, target, room_id)

    async def forget(self, user: UserID, room_id: str) -> None:
        user_id = user.to_string()

        member = await self.state_handler.get_current_state(
            room_id=room_id, event_type=EventTypes.Member, state_key=user_id
        )
        membership = member.membership if member else None

        if membership is not None and membership not in [
            Membership.LEAVE,
            Membership.BAN,
        ]:
            raise SynapseError(400, "User %s in room %s" % (user_id, room_id))

        if membership:
            await self.store.forget(user_id, room_id)