summary refs log tree commit diff
path: root/synapse/crypto/keyring.py
blob: 80f27f8c53b9c9b830b787414ac41928e61db363 (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
# -*- 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 synapse.crypto.keyclient import fetch_server_key
from synapse.api.errors import SynapseError, Codes
from synapse.util.retryutils import get_retry_limiter
from synapse.util import unwrapFirstError
from synapse.util.async import ObservableDeferred
from synapse.util.logcontext import (
    preserve_context_over_deferred, preserve_context_over_fn, PreserveLoggingContext,
    preserve_fn
)
from synapse.util.metrics import Measure

from twisted.internet import defer

from signedjson.sign import (
    verify_signed_json, signature_ids, sign_json, encode_canonical_json
)
from signedjson.key import (
    is_signing_algorithm_supported, decode_verify_key_bytes
)
from unpaddedbase64 import decode_base64, encode_base64

from OpenSSL import crypto

from collections import namedtuple
import urllib
import hashlib
import logging


logger = logging.getLogger(__name__)


VerifyKeyRequest = namedtuple("VerifyRequest", (
    "server_name", "key_ids", "json_object", "deferred"
))
"""
A request for a verify key to verify a JSON object.

Attributes:
    server_name(str): The name of the server to verify against.
    key_ids(set(str)): The set of key_ids to that could be used to verify the
        JSON object
    json_object(dict): The JSON object to verify.
    deferred(twisted.internet.defer.Deferred):
        A deferred (server_name, key_id, verify_key) tuple that resolves when
        a verify key has been fetched
"""


class KeyLookupError(ValueError):
    pass


class Keyring(object):
    def __init__(self, hs):
        self.store = hs.get_datastore()
        self.clock = hs.get_clock()
        self.client = hs.get_http_client()
        self.config = hs.get_config()
        self.perspective_servers = self.config.perspectives
        self.hs = hs

        self.key_downloads = {}

    def verify_json_for_server(self, server_name, json_object):
        return self.verify_json_objects_for_server(
            [(server_name, json_object)]
        )[0]

    def verify_json_objects_for_server(self, server_and_json):
        """Bulk verfies signatures of json objects, bulk fetching keys as
        necessary.

        Args:
            server_and_json (list): List of pairs of (server_name, json_object)

        Returns:
            list of deferreds indicating success or failure to verify each
            json object's signature for the given server_name.
        """
        verify_requests = []

        for server_name, json_object in server_and_json:

            key_ids = signature_ids(json_object, server_name)
            if not key_ids:
                logger.warn("Request from %s: no supported signature keys",
                            server_name)
                deferred = defer.fail(SynapseError(
                    400,
                    "Not signed with a supported algorithm",
                    Codes.UNAUTHORIZED,
                ))
            else:
                deferred = defer.Deferred()

            logger.debug("Verifying for %s with key_ids %s",
                         server_name, key_ids)

            verify_request = VerifyKeyRequest(
                server_name, key_ids, json_object, deferred
            )

            verify_requests.append(verify_request)

        @defer.inlineCallbacks
        def handle_key_deferred(verify_request):
            server_name = verify_request.server_name
            try:
                _, key_id, verify_key = yield verify_request.deferred
            except IOError as e:
                logger.warn(
                    "Got IOError when downloading keys for %s: %s %s",
                    server_name, type(e).__name__, str(e.message),
                )
                raise SynapseError(
                    502,
                    "Error downloading keys for %s" % (server_name,),
                    Codes.UNAUTHORIZED,
                )
            except Exception as e:
                logger.exception(
                    "Got Exception when downloading keys for %s: %s %s",
                    server_name, type(e).__name__, str(e.message),
                )
                raise SynapseError(
                    401,
                    "No key for %s with id %s" % (server_name, key_ids),
                    Codes.UNAUTHORIZED,
                )

            json_object = verify_request.json_object

            logger.debug("Got key %s %s:%s for server %s, verifying" % (
                key_id, verify_key.alg, verify_key.version, server_name,
            ))
            try:
                verify_signed_json(json_object, server_name, verify_key)
            except:
                raise SynapseError(
                    401,
                    "Invalid signature for server %s with key %s:%s" % (
                        server_name, verify_key.alg, verify_key.version
                    ),
                    Codes.UNAUTHORIZED,
                )

        server_to_deferred = {
            server_name: defer.Deferred()
            for server_name, _ in server_and_json
        }

        with PreserveLoggingContext():

            # We want to wait for any previous lookups to complete before
            # proceeding.
            wait_on_deferred = self.wait_for_previous_lookups(
                [server_name for server_name, _ in server_and_json],
                server_to_deferred,
            )

            # Actually start fetching keys.
            wait_on_deferred.addBoth(
                lambda _: self.get_server_verify_keys(verify_requests)
            )

            # When we've finished fetching all the keys for a given server_name,
            # resolve the deferred passed to `wait_for_previous_lookups` so that
            # any lookups waiting will proceed.
            server_to_request_ids = {}

            def remove_deferreds(res, server_name, verify_request):
                request_id = id(verify_request)
                server_to_request_ids[server_name].discard(request_id)
                if not server_to_request_ids[server_name]:
                    d = server_to_deferred.pop(server_name, None)
                    if d:
                        d.callback(None)
                return res

            for verify_request in verify_requests:
                server_name = verify_request.server_name
                request_id = id(verify_request)
                server_to_request_ids.setdefault(server_name, set()).add(request_id)
                deferred.addBoth(remove_deferreds, server_name, verify_request)

        # Pass those keys to handle_key_deferred so that the json object
        # signatures can be verified
        return [
            preserve_context_over_fn(handle_key_deferred, verify_request)
            for verify_request in verify_requests
        ]

    @defer.inlineCallbacks
    def wait_for_previous_lookups(self, server_names, server_to_deferred):
        """Waits for any previous key lookups for the given servers to finish.

        Args:
            server_names (list): list of server_names we want to lookup
            server_to_deferred (dict): server_name to deferred which gets
                resolved once we've finished looking up keys for that server
        """
        while True:
            wait_on = [
                self.key_downloads[server_name]
                for server_name in server_names
                if server_name in self.key_downloads
            ]
            if wait_on:
                with PreserveLoggingContext():
                    yield defer.DeferredList(wait_on)
            else:
                break

        for server_name, deferred in server_to_deferred.items():
            d = ObservableDeferred(preserve_context_over_deferred(deferred))
            self.key_downloads[server_name] = d

            def rm(r, server_name):
                self.key_downloads.pop(server_name, None)
                return r

            d.addBoth(rm, server_name)

    def get_server_verify_keys(self, verify_requests):
        """Takes a dict of KeyGroups and tries to find at least one key for
        each group.
        """

        # These are functions that produce keys given a list of key ids
        key_fetch_fns = (
            self.get_keys_from_store,  # First try the local store
            self.get_keys_from_perspectives,  # Then try via perspectives
            self.get_keys_from_server,  # Then try directly
        )

        @defer.inlineCallbacks
        def do_iterations():
            with Measure(self.clock, "get_server_verify_keys"):
                merged_results = {}

                missing_keys = {}
                for verify_request in verify_requests:
                    missing_keys.setdefault(verify_request.server_name, set()).update(
                        verify_request.key_ids
                    )

                for fn in key_fetch_fns:
                    results = yield fn(missing_keys.items())
                    merged_results.update(results)

                    # We now need to figure out which verify requests we have keys
                    # for and which we don't
                    missing_keys = {}
                    requests_missing_keys = []
                    for verify_request in verify_requests:
                        server_name = verify_request.server_name
                        result_keys = merged_results[server_name]

                        if verify_request.deferred.called:
                            # We've already called this deferred, which probably
                            # means that we've already found a key for it.
                            continue

                        for key_id in verify_request.key_ids:
                            if key_id in result_keys:
                                with PreserveLoggingContext():
                                    verify_request.deferred.callback((
                                        server_name,
                                        key_id,
                                        result_keys[key_id],
                                    ))
                                break
                        else:
                            # The else block is only reached if the loop above
                            # doesn't break.
                            missing_keys.setdefault(server_name, set()).update(
                                verify_request.key_ids
                            )
                            requests_missing_keys.append(verify_request)

                    if not missing_keys:
                        break

                for verify_request in requests_missing_keys.values():
                    verify_request.deferred.errback(SynapseError(
                        401,
                        "No key for %s with id %s" % (
                            verify_request.server_name, verify_request.key_ids,
                        ),
                        Codes.UNAUTHORIZED,
                    ))

        def on_err(err):
            for verify_request in verify_requests:
                if not verify_request.deferred.called:
                    verify_request.deferred.errback(err)

        do_iterations().addErrback(on_err)

    @defer.inlineCallbacks
    def get_keys_from_store(self, server_name_and_key_ids):
        res = yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(self.store.get_server_verify_keys)(
                    server_name, key_ids
                ).addCallback(lambda ks, server: (server, ks), server_name)
                for server_name, key_ids in server_name_and_key_ids
            ],
            consumeErrors=True,
        )).addErrback(unwrapFirstError)

        defer.returnValue(dict(res))

    @defer.inlineCallbacks
    def get_keys_from_perspectives(self, server_name_and_key_ids):
        @defer.inlineCallbacks
        def get_key(perspective_name, perspective_keys):
            try:
                result = yield self.get_server_verify_key_v2_indirect(
                    server_name_and_key_ids, perspective_name, perspective_keys
                )
                defer.returnValue(result)
            except Exception as e:
                logger.exception(
                    "Unable to get key from %r: %s %s",
                    perspective_name,
                    type(e).__name__, str(e.message),
                )
                defer.returnValue({})

        results = yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(get_key)(p_name, p_keys)
                for p_name, p_keys in self.perspective_servers.items()
            ],
            consumeErrors=True,
        )).addErrback(unwrapFirstError)

        union_of_keys = {}
        for result in results:
            for server_name, keys in result.items():
                union_of_keys.setdefault(server_name, {}).update(keys)

        defer.returnValue(union_of_keys)

    @defer.inlineCallbacks
    def get_keys_from_server(self, server_name_and_key_ids):
        @defer.inlineCallbacks
        def get_key(server_name, key_ids):
            limiter = yield get_retry_limiter(
                server_name,
                self.clock,
                self.store,
            )
            with limiter:
                keys = None
                try:
                    keys = yield self.get_server_verify_key_v2_direct(
                        server_name, key_ids
                    )
                except Exception as e:
                    logger.info(
                        "Unable to get key %r for %r directly: %s %s",
                        key_ids, server_name,
                        type(e).__name__, str(e.message),
                    )

                if not keys:
                    keys = yield self.get_server_verify_key_v1_direct(
                        server_name, key_ids
                    )

                    keys = {server_name: keys}

            defer.returnValue(keys)

        results = yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(get_key)(server_name, key_ids)
                for server_name, key_ids in server_name_and_key_ids
            ],
            consumeErrors=True,
        )).addErrback(unwrapFirstError)

        merged = {}
        for result in results:
            merged.update(result)

        defer.returnValue({
            server_name: keys
            for server_name, keys in merged.items()
            if keys
        })

    @defer.inlineCallbacks
    def get_server_verify_key_v2_indirect(self, server_names_and_key_ids,
                                          perspective_name,
                                          perspective_keys):
        # TODO(mark): Set the minimum_valid_until_ts to that needed by
        # the events being validated or the current time if validating
        # an incoming request.
        query_response = yield self.client.post_json(
            destination=perspective_name,
            path=b"/_matrix/key/v2/query",
            data={
                u"server_keys": {
                    server_name: {
                        key_id: {
                            u"minimum_valid_until_ts": 0
                        } for key_id in key_ids
                    }
                    for server_name, key_ids in server_names_and_key_ids
                }
            },
            long_retries=True,
        )

        keys = {}

        responses = query_response["server_keys"]

        for response in responses:
            if (u"signatures" not in response
                    or perspective_name not in response[u"signatures"]):
                raise KeyLookupError(
                    "Key response not signed by perspective server"
                    " %r" % (perspective_name,)
                )

            verified = False
            for key_id in response[u"signatures"][perspective_name]:
                if key_id in perspective_keys:
                    verify_signed_json(
                        response,
                        perspective_name,
                        perspective_keys[key_id]
                    )
                    verified = True

            if not verified:
                logging.info(
                    "Response from perspective server %r not signed with a"
                    " known key, signed with: %r, known keys: %r",
                    perspective_name,
                    list(response[u"signatures"][perspective_name]),
                    list(perspective_keys)
                )
                raise KeyLookupError(
                    "Response not signed with a known key for perspective"
                    " server %r" % (perspective_name,)
                )

            processed_response = yield self.process_v2_response(
                perspective_name, response, only_from_server=False
            )

            for server_name, response_keys in processed_response.items():
                keys.setdefault(server_name, {}).update(response_keys)

        yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(self.store_keys)(
                    server_name=server_name,
                    from_server=perspective_name,
                    verify_keys=response_keys,
                )
                for server_name, response_keys in keys.items()
            ],
            consumeErrors=True
        )).addErrback(unwrapFirstError)

        defer.returnValue(keys)

    @defer.inlineCallbacks
    def get_server_verify_key_v2_direct(self, server_name, key_ids):
        keys = {}

        for requested_key_id in key_ids:
            if requested_key_id in keys:
                continue

            (response, tls_certificate) = yield fetch_server_key(
                server_name, self.hs.tls_server_context_factory,
                path=(b"/_matrix/key/v2/server/%s" % (
                    urllib.quote(requested_key_id),
                )).encode("ascii"),
            )

            if (u"signatures" not in response
                    or server_name not in response[u"signatures"]):
                raise KeyLookupError("Key response not signed by remote server")

            if "tls_fingerprints" not in response:
                raise KeyLookupError("Key response missing TLS fingerprints")

            certificate_bytes = crypto.dump_certificate(
                crypto.FILETYPE_ASN1, tls_certificate
            )
            sha256_fingerprint = hashlib.sha256(certificate_bytes).digest()
            sha256_fingerprint_b64 = encode_base64(sha256_fingerprint)

            response_sha256_fingerprints = set()
            for fingerprint in response[u"tls_fingerprints"]:
                if u"sha256" in fingerprint:
                    response_sha256_fingerprints.add(fingerprint[u"sha256"])

            if sha256_fingerprint_b64 not in response_sha256_fingerprints:
                raise KeyLookupError("TLS certificate not allowed by fingerprints")

            response_keys = yield self.process_v2_response(
                from_server=server_name,
                requested_ids=[requested_key_id],
                response_json=response,
            )

            keys.update(response_keys)

        yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(self.store_keys)(
                    server_name=key_server_name,
                    from_server=server_name,
                    verify_keys=verify_keys,
                )
                for key_server_name, verify_keys in keys.items()
            ],
            consumeErrors=True
        )).addErrback(unwrapFirstError)

        defer.returnValue(keys)

    @defer.inlineCallbacks
    def process_v2_response(self, from_server, response_json,
                            requested_ids=[], only_from_server=True):
        time_now_ms = self.clock.time_msec()
        response_keys = {}
        verify_keys = {}
        for key_id, key_data in response_json["verify_keys"].items():
            if is_signing_algorithm_supported(key_id):
                key_base64 = key_data["key"]
                key_bytes = decode_base64(key_base64)
                verify_key = decode_verify_key_bytes(key_id, key_bytes)
                verify_key.time_added = time_now_ms
                verify_keys[key_id] = verify_key

        old_verify_keys = {}
        for key_id, key_data in response_json["old_verify_keys"].items():
            if is_signing_algorithm_supported(key_id):
                key_base64 = key_data["key"]
                key_bytes = decode_base64(key_base64)
                verify_key = decode_verify_key_bytes(key_id, key_bytes)
                verify_key.expired = key_data["expired_ts"]
                verify_key.time_added = time_now_ms
                old_verify_keys[key_id] = verify_key

        results = {}
        server_name = response_json["server_name"]
        if only_from_server:
            if server_name != from_server:
                raise KeyLookupError(
                    "Expected a response for server %r not %r" % (
                        from_server, server_name
                    )
                )
        for key_id in response_json["signatures"].get(server_name, {}):
            if key_id not in response_json["verify_keys"]:
                raise KeyLookupError(
                    "Key response must include verification keys for all"
                    " signatures"
                )
            if key_id in verify_keys:
                verify_signed_json(
                    response_json,
                    server_name,
                    verify_keys[key_id]
                )

        signed_key_json = sign_json(
            response_json,
            self.config.server_name,
            self.config.signing_key[0],
        )

        signed_key_json_bytes = encode_canonical_json(signed_key_json)
        ts_valid_until_ms = signed_key_json[u"valid_until_ts"]

        updated_key_ids = set(requested_ids)
        updated_key_ids.update(verify_keys)
        updated_key_ids.update(old_verify_keys)

        response_keys.update(verify_keys)
        response_keys.update(old_verify_keys)

        yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(self.store.store_server_keys_json)(
                    server_name=server_name,
                    key_id=key_id,
                    from_server=server_name,
                    ts_now_ms=time_now_ms,
                    ts_expires_ms=ts_valid_until_ms,
                    key_json_bytes=signed_key_json_bytes,
                )
                for key_id in updated_key_ids
            ],
            consumeErrors=True,
        )).addErrback(unwrapFirstError)

        results[server_name] = response_keys

        defer.returnValue(results)

    @defer.inlineCallbacks
    def get_server_verify_key_v1_direct(self, server_name, key_ids):
        """Finds a verification key for the server with one of the key ids.
        Args:
            server_name (str): The name of the server to fetch a key for.
            keys_ids (list of str): The key_ids to check for.
        """

        # Try to fetch the key from the remote server.

        (response, tls_certificate) = yield fetch_server_key(
            server_name, self.hs.tls_server_context_factory
        )

        # Check the response.

        x509_certificate_bytes = crypto.dump_certificate(
            crypto.FILETYPE_ASN1, tls_certificate
        )

        if ("signatures" not in response
                or server_name not in response["signatures"]):
            raise KeyLookupError("Key response not signed by remote server")

        if "tls_certificate" not in response:
            raise KeyLookupError("Key response missing TLS certificate")

        tls_certificate_b64 = response["tls_certificate"]

        if encode_base64(x509_certificate_bytes) != tls_certificate_b64:
            raise KeyLookupError("TLS certificate doesn't match")

        # Cache the result in the datastore.

        time_now_ms = self.clock.time_msec()

        verify_keys = {}
        for key_id, key_base64 in response["verify_keys"].items():
            if is_signing_algorithm_supported(key_id):
                key_bytes = decode_base64(key_base64)
                verify_key = decode_verify_key_bytes(key_id, key_bytes)
                verify_key.time_added = time_now_ms
                verify_keys[key_id] = verify_key

        for key_id in response["signatures"][server_name]:
            if key_id not in response["verify_keys"]:
                raise KeyLookupError(
                    "Key response must include verification keys for all"
                    " signatures"
                )
            if key_id in verify_keys:
                verify_signed_json(
                    response,
                    server_name,
                    verify_keys[key_id]
                )

        yield self.store.store_server_certificate(
            server_name,
            server_name,
            time_now_ms,
            tls_certificate,
        )

        yield self.store_keys(
            server_name=server_name,
            from_server=server_name,
            verify_keys=verify_keys,
        )

        defer.returnValue(verify_keys)

    @defer.inlineCallbacks
    def store_keys(self, server_name, from_server, verify_keys):
        """Store a collection of verify keys for a given server
        Args:
            server_name(str): The name of the server the keys are for.
            from_server(str): The server the keys were downloaded from.
            verify_keys(dict): A mapping of key_id to VerifyKey.
        Returns:
            A deferred that completes when the keys are stored.
        """
        # TODO(markjh): Store whether the keys have expired.
        yield preserve_context_over_deferred(defer.gatherResults(
            [
                preserve_fn(self.store.store_server_verify_key)(
                    server_name, server_name, key.time_added, key
                )
                for key_id, key in verify_keys.items()
            ],
            consumeErrors=True,
        )).addErrback(unwrapFirstError)