# -*- 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.web.client import URI, Agent, HTTPConnectionPool, 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 = 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): logger.info( "Connecting to %s:%i", res.target_host.decode("ascii"), res.target_port, ) ep = HostnameEndpoint(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, )) # 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 and 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) 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) 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 """