summary refs log tree commit diff
path: root/synapse/http/federation/matrix_federation_agent.py
blob: 3a0525e3659468266fed253ab74d7b0182d94703 (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
# -*- coding: utf-8 -*-
# Copyright 2019 New Vector 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.
import json
import logging
import random
import time

import attr
from netaddr import IPAddress
from zope.interface import implementer

from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.internet.interfaces import IStreamClientEndpoint
from twisted.web.client import URI, Agent, HTTPConnectionPool, RedirectAgent, readBody
from twisted.web.http import stringToDatetime
from twisted.web.http_headers import Headers
from twisted.web.iweb import IAgent

from synapse.http.federation.srv_resolver import SrvResolver, pick_server_from_list
from synapse.util.caches.ttlcache import TTLCache
from synapse.util.logcontext import make_deferred_yieldable

# period to cache .well-known results for by default
WELL_KNOWN_DEFAULT_CACHE_PERIOD = 24 * 3600

# jitter to add to the .well-known default cache ttl
WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER = 10 * 60

# period to cache failure to fetch .well-known for
WELL_KNOWN_INVALID_CACHE_PERIOD = 1 * 3600

# cap for .well-known cache period
WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600


logger = logging.getLogger(__name__)
well_known_cache = TTLCache('well-known')


@implementer(IAgent)
class MatrixFederationAgent(object):
    """An Agent-like thing which provides a `request` method which will look up a matrix
    server and send an HTTP request to it.

    Doesn't implement any retries. (Those are done in MatrixFederationHttpClient.)

    Args:
        reactor (IReactor): twisted reactor to use for underlying requests

        tls_client_options_factory (ClientTLSOptionsFactory|None):
            factory to use for fetching client tls options, or none to disable TLS.

        _well_known_tls_policy (IPolicyForHTTPS|None):
            TLS policy to use for fetching .well-known files. None to use a default
            (browser-like) implementation.

        srv_resolver (SrvResolver|None):
            SRVResolver impl to use for looking up SRV records. None to use a default
            implementation.
    """

    def __init__(
        self, reactor, tls_client_options_factory,
        _well_known_tls_policy=None,
        _srv_resolver=None,
        _well_known_cache=well_known_cache,
    ):
        self._reactor = reactor
        self._tls_client_options_factory = tls_client_options_factory
        if _srv_resolver is None:
            _srv_resolver = SrvResolver()
        self._srv_resolver = _srv_resolver

        self._pool = HTTPConnectionPool(reactor)
        self._pool.retryAutomatically = False
        self._pool.maxPersistentPerHost = 5
        self._pool.cachedConnectionTimeout = 2 * 60

        agent_args = {}
        if _well_known_tls_policy is not None:
            # the param is called 'contextFactory', but actually passing a
            # contextfactory is deprecated, and it expects an IPolicyForHTTPS.
            agent_args['contextFactory'] = _well_known_tls_policy
        _well_known_agent = RedirectAgent(
            Agent(self._reactor, pool=self._pool, **agent_args),
        )
        self._well_known_agent = _well_known_agent

        self._well_known_cache = _well_known_cache

    @defer.inlineCallbacks
    def request(self, method, uri, headers=None, bodyProducer=None):
        """
        Args:
            method (bytes): HTTP method: GET/POST/etc

            uri (bytes): Absolute URI to be retrieved

            headers (twisted.web.http_headers.Headers|None):
                HTTP headers to send with the request, or None to
                send no extra headers.

            bodyProducer (twisted.web.iweb.IBodyProducer|None):
                An object which can generate bytes to make up the
                body of this request (for example, the properly encoded contents of
                a file for a file upload).  Or None if the request is to have
                no body.

        Returns:
            Deferred[twisted.web.iweb.IResponse]:
                fires when the header of the response has been received (regardless of the
                response status code). Fails if there is any problem which prevents that
                response from being received (including problems that prevent the request
                from being sent).
        """
        parsed_uri = URI.fromBytes(uri, defaultPort=-1)
        res = yield self._route_matrix_uri(parsed_uri)

        # set up the TLS connection params
        #
        # XXX disabling TLS is really only supported here for the benefit of the
        # unit tests. We should make the UTs cope with TLS rather than having to make
        # the code support the unit tests.
        if self._tls_client_options_factory is None:
            tls_options = None
        else:
            tls_options = self._tls_client_options_factory.get_options(
                res.tls_server_name.decode("ascii")
            )

        # make sure that the Host header is set correctly
        if headers is None:
            headers = Headers()
        else:
            headers = headers.copy()

        if not headers.hasHeader(b'host'):
            headers.addRawHeader(b'host', res.host_header)

        class EndpointFactory(object):
            @staticmethod
            def endpointForURI(_uri):
                ep = LoggingHostnameEndpoint(
                    self._reactor, res.target_host, res.target_port,
                )
                if tls_options is not None:
                    ep = wrapClientTLS(tls_options, ep)
                return ep

        agent = Agent.usingEndpointFactory(self._reactor, EndpointFactory(), self._pool)
        res = yield make_deferred_yieldable(
            agent.request(method, uri, headers, bodyProducer)
        )
        defer.returnValue(res)

    @defer.inlineCallbacks
    def _route_matrix_uri(self, parsed_uri, lookup_well_known=True):
        """Helper for `request`: determine the routing for a Matrix URI

        Args:
            parsed_uri (twisted.web.client.URI): uri to route. Note that it should be
                parsed with URI.fromBytes(uri, defaultPort=-1) to set the `port` to -1
                if there is no explicit port given.

            lookup_well_known (bool): True if we should look up the .well-known file if
                there is no SRV record.

        Returns:
            Deferred[_RoutingResult]
        """
        # check for an IP literal
        try:
            ip_address = IPAddress(parsed_uri.host.decode("ascii"))
        except Exception:
            # not an IP address
            ip_address = None

        if ip_address:
            port = parsed_uri.port
            if port == -1:
                port = 8448
            defer.returnValue(_RoutingResult(
                host_header=parsed_uri.netloc,
                tls_server_name=parsed_uri.host,
                target_host=parsed_uri.host,
                target_port=port,
            ))

        if parsed_uri.port != -1:
            # there is an explicit port
            defer.returnValue(_RoutingResult(
                host_header=parsed_uri.netloc,
                tls_server_name=parsed_uri.host,
                target_host=parsed_uri.host,
                target_port=parsed_uri.port,
            ))

        if lookup_well_known:
            # try a .well-known lookup
            well_known_server = yield self._get_well_known(parsed_uri.host)

            if well_known_server:
                # if we found a .well-known, start again, but don't do another
                # .well-known lookup.

                # parse the server name in the .well-known response into host/port.
                # (This code is lifted from twisted.web.client.URI.fromBytes).
                if b':' in well_known_server:
                    well_known_host, well_known_port = well_known_server.rsplit(b':', 1)
                    try:
                        well_known_port = int(well_known_port)
                    except ValueError:
                        # the part after the colon could not be parsed as an int
                        # - we assume it is an IPv6 literal with no port (the closing
                        # ']' stops it being parsed as an int)
                        well_known_host, well_known_port = well_known_server, -1
                else:
                    well_known_host, well_known_port = well_known_server, -1

                new_uri = URI(
                    scheme=parsed_uri.scheme,
                    netloc=well_known_server,
                    host=well_known_host,
                    port=well_known_port,
                    path=parsed_uri.path,
                    params=parsed_uri.params,
                    query=parsed_uri.query,
                    fragment=parsed_uri.fragment,
                )

                res = yield self._route_matrix_uri(new_uri, lookup_well_known=False)
                defer.returnValue(res)

        # try a SRV lookup
        service_name = b"_matrix._tcp.%s" % (parsed_uri.host,)
        server_list = yield self._srv_resolver.resolve_service(service_name)

        if not server_list:
            target_host = parsed_uri.host
            port = 8448
            logger.debug(
                "No SRV record for %s, using %s:%i",
                parsed_uri.host.decode("ascii"), target_host.decode("ascii"), port,
            )
        else:
            target_host, port = pick_server_from_list(server_list)
            logger.debug(
                "Picked %s:%i from SRV records for %s",
                target_host.decode("ascii"), port, parsed_uri.host.decode("ascii"),
            )

        defer.returnValue(_RoutingResult(
            host_header=parsed_uri.netloc,
            tls_server_name=parsed_uri.host,
            target_host=target_host,
            target_port=port,
        ))

    @defer.inlineCallbacks
    def _get_well_known(self, server_name):
        """Attempt to fetch and parse a .well-known file for the given server

        Args:
            server_name (bytes): name of the server, from the requested url

        Returns:
            Deferred[bytes|None]: either the new server name, from the .well-known, or
                None if there was no .well-known file.
        """
        try:
            cached = self._well_known_cache[server_name]
            defer.returnValue(cached)
        except KeyError:
            pass

        # TODO: should we linearise so that we don't end up doing two .well-known requests
        # for the same server in parallel?

        uri = b"https://%s/.well-known/matrix/server" % (server_name, )
        uri_str = uri.decode("ascii")
        logger.info("Fetching %s", uri_str)
        try:
            response = yield make_deferred_yieldable(
                self._well_known_agent.request(b"GET", uri),
            )
            body = yield make_deferred_yieldable(readBody(response))
            if response.code != 200:
                raise Exception("Non-200 response %s" % (response.code, ))
        except Exception as e:
            logger.info("Error fetching %s: %s", uri_str, e)

            # add some randomness to the TTL to avoid a stampeding herd every hour
            # after startup
            cache_period = WELL_KNOWN_INVALID_CACHE_PERIOD
            cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)

            self._well_known_cache.set(server_name, None, cache_period)
            defer.returnValue(None)

        try:
            parsed_body = json.loads(body.decode('utf-8'))
            logger.info("Response from .well-known: %s", parsed_body)
            if not isinstance(parsed_body, dict):
                raise Exception("not a dict")
            if "m.server" not in parsed_body:
                raise Exception("Missing key 'm.server'")
        except Exception as e:
            raise Exception("invalid .well-known response from %s: %s" % (uri_str, e,))

        result = parsed_body["m.server"].encode("ascii")

        cache_period = _cache_period_from_headers(
            response.headers,
            time_now=self._reactor.seconds,
        )
        if cache_period is None:
            cache_period = WELL_KNOWN_DEFAULT_CACHE_PERIOD
            # add some randomness to the TTL to avoid a stampeding herd every 24 hours
            # after startup
            cache_period += random.uniform(0, WELL_KNOWN_DEFAULT_CACHE_PERIOD_JITTER)
        else:
            cache_period = min(cache_period, WELL_KNOWN_MAX_CACHE_PERIOD)

        if cache_period > 0:
            self._well_known_cache.set(server_name, result, cache_period)

        defer.returnValue(result)


@implementer(IStreamClientEndpoint)
class LoggingHostnameEndpoint(object):
    """A wrapper for HostnameEndpint which logs when it connects"""
    def __init__(self, reactor, host, port, *args, **kwargs):
        self.host = host
        self.port = port
        self.ep = HostnameEndpoint(reactor, host, port, *args, **kwargs)

    def connect(self, protocol_factory):
        logger.info("Connecting to %s:%i", self.host, self.port)
        return self.ep.connect(protocol_factory)


def _cache_period_from_headers(headers, time_now=time.time):
    cache_controls = _parse_cache_control(headers)

    if b'no-store' in cache_controls:
        return 0

    if b'max-age' in cache_controls:
        try:
            max_age = int(cache_controls[b'max-age'])
            return max_age
        except ValueError:
            pass

    expires = headers.getRawHeaders(b'expires')
    if expires is not None:
        try:
            expires_date = stringToDatetime(expires[-1])
            return expires_date - time_now()
        except ValueError:
            # RFC7234 says 'A cache recipient MUST interpret invalid date formats,
            # especially the value "0", as representing a time in the past (i.e.,
            # "already expired").
            return 0

    return None


def _parse_cache_control(headers):
    cache_controls = {}
    for hdr in headers.getRawHeaders(b'cache-control', []):
        for directive in hdr.split(b','):
            splits = [x.strip() for x in directive.split(b'=', 1)]
            k = splits[0].lower()
            v = splits[1] if len(splits) > 1 else None
            cache_controls[k] = v
    return cache_controls


@attr.s
class _RoutingResult(object):
    """The result returned by `_route_matrix_uri`.

    Contains the parameters needed to direct a federation connection to a particular
    server.

    Where a SRV record points to several servers, this object contains a single server
    chosen from the list.
    """

    host_header = attr.ib()
    """
    The value we should assign to the Host header (host:port from the matrix
    URI, or .well-known).

    :type: bytes
    """

    tls_server_name = attr.ib()
    """
    The server name we should set in the SNI (typically host, without port, from the
    matrix URI or .well-known)

    :type: bytes
    """

    target_host = attr.ib()
    """
    The hostname (or IP literal) we should route the TCP connection to (the target of the
    SRV record, or the hostname from the URL/.well-known)

    :type: bytes
    """

    target_port = attr.ib()
    """
    The port we should route the TCP connection to (the target of the SRV record, or
    the port from the URL/.well-known, or 8448)

    :type: int
    """