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![Tim Leung](/assets/img/avatar_default.png)
A reactor was being passed instead of a whitelist for the BlacklistingAgentWrapper used by the WellyKnownResolver. This coulld cause exceptions when attempting to connect to IP addresses that are blacklisted, but in reality this did not have any observable affect since this code is not used for IP literals.
352 lines
12 KiB
Python
352 lines
12 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2019 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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import urllib.parse
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from typing import List, Optional
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from netaddr import AddrFormatError, IPAddress, IPSet
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from zope.interface import implementer
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from twisted.internet import defer
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from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
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from twisted.internet.interfaces import (
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IProtocolFactory,
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IReactorCore,
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IStreamClientEndpoint,
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)
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from twisted.web.client import URI, Agent, HTTPConnectionPool
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from twisted.web.http_headers import Headers
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from twisted.web.iweb import IAgent, IAgentEndpointFactory, IBodyProducer
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from synapse.crypto.context_factory import FederationPolicyForHTTPS
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from synapse.http.client import BlacklistingAgentWrapper
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from synapse.http.federation.srv_resolver import Server, SrvResolver
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from synapse.http.federation.well_known_resolver import WellKnownResolver
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from synapse.logging.context import make_deferred_yieldable, run_in_background
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from synapse.util import Clock
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logger = logging.getLogger(__name__)
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@implementer(IAgent)
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class MatrixFederationAgent:
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"""An Agent-like thing which provides a `request` method which correctly
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handles resolving matrix server names when using matrix://. Handles standard
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https URIs as normal.
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Doesn't implement any retries. (Those are done in MatrixFederationHttpClient.)
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Args:
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reactor: twisted reactor to use for underlying requests
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tls_client_options_factory:
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factory to use for fetching client tls options, or none to disable TLS.
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user_agent:
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The user agent header to use for federation requests.
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_srv_resolver:
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SrvResolver implementation to use for looking up SRV records. None
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to use a default implementation.
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_well_known_resolver:
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WellKnownResolver to use to perform well-known lookups. None to use a
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default implementation.
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"""
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def __init__(
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self,
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reactor: IReactorCore,
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tls_client_options_factory: Optional[FederationPolicyForHTTPS],
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user_agent: bytes,
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ip_blacklist: IPSet,
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_srv_resolver: Optional[SrvResolver] = None,
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_well_known_resolver: Optional[WellKnownResolver] = None,
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):
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self._reactor = reactor
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self._clock = Clock(reactor)
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self._pool = HTTPConnectionPool(reactor)
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self._pool.retryAutomatically = False
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self._pool.maxPersistentPerHost = 5
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self._pool.cachedConnectionTimeout = 2 * 60
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self._agent = Agent.usingEndpointFactory(
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self._reactor,
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MatrixHostnameEndpointFactory(
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reactor, tls_client_options_factory, _srv_resolver
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),
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pool=self._pool,
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)
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self.user_agent = user_agent
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if _well_known_resolver is None:
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# Note that the name resolver has already been wrapped in a
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# IPBlacklistingResolver by MatrixFederationHttpClient.
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_well_known_resolver = WellKnownResolver(
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self._reactor,
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agent=BlacklistingAgentWrapper(
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Agent(
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self._reactor,
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pool=self._pool,
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contextFactory=tls_client_options_factory,
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),
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ip_blacklist=ip_blacklist,
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),
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user_agent=self.user_agent,
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)
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self._well_known_resolver = _well_known_resolver
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@defer.inlineCallbacks
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def request(
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self,
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method: bytes,
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uri: bytes,
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headers: Optional[Headers] = None,
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bodyProducer: Optional[IBodyProducer] = None,
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) -> defer.Deferred:
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"""
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Args:
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method: HTTP method: GET/POST/etc
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uri: Absolute URI to be retrieved
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headers:
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HTTP headers to send with the request, or None to send no extra headers.
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bodyProducer:
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An object which can generate bytes to make up the
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body of this request (for example, the properly encoded contents of
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a file for a file upload). Or None if the request is to have
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no body.
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Returns:
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Deferred[twisted.web.iweb.IResponse]:
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fires when the header of the response has been received (regardless of the
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response status code). Fails if there is any problem which prevents that
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response from being received (including problems that prevent the request
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from being sent).
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"""
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# We use urlparse as that will set `port` to None if there is no
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# explicit port.
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parsed_uri = urllib.parse.urlparse(uri)
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# There must be a valid hostname.
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assert parsed_uri.hostname
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# If this is a matrix:// URI check if the server has delegated matrix
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# traffic using well-known delegation.
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#
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# We have to do this here and not in the endpoint as we need to rewrite
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# the host header with the delegated server name.
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delegated_server = None
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if (
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parsed_uri.scheme == b"matrix"
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and not _is_ip_literal(parsed_uri.hostname)
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and not parsed_uri.port
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):
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well_known_result = yield defer.ensureDeferred(
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self._well_known_resolver.get_well_known(parsed_uri.hostname)
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)
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delegated_server = well_known_result.delegated_server
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if delegated_server:
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# Ok, the server has delegated matrix traffic to somewhere else, so
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# lets rewrite the URL to replace the server with the delegated
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# server name.
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uri = urllib.parse.urlunparse(
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(
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parsed_uri.scheme,
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delegated_server,
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parsed_uri.path,
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parsed_uri.params,
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parsed_uri.query,
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parsed_uri.fragment,
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)
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)
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parsed_uri = urllib.parse.urlparse(uri)
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# We need to make sure the host header is set to the netloc of the
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# server and that a user-agent is provided.
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if headers is None:
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headers = Headers()
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else:
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headers = headers.copy()
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if not headers.hasHeader(b"host"):
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headers.addRawHeader(b"host", parsed_uri.netloc)
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if not headers.hasHeader(b"user-agent"):
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headers.addRawHeader(b"user-agent", self.user_agent)
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res = yield make_deferred_yieldable(
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self._agent.request(method, uri, headers, bodyProducer)
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)
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return res
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@implementer(IAgentEndpointFactory)
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class MatrixHostnameEndpointFactory:
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"""Factory for MatrixHostnameEndpoint for parsing to an Agent.
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"""
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def __init__(
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self,
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reactor: IReactorCore,
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tls_client_options_factory: Optional[FederationPolicyForHTTPS],
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srv_resolver: Optional[SrvResolver],
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):
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self._reactor = reactor
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self._tls_client_options_factory = tls_client_options_factory
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if srv_resolver is None:
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srv_resolver = SrvResolver()
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self._srv_resolver = srv_resolver
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def endpointForURI(self, parsed_uri):
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return MatrixHostnameEndpoint(
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self._reactor,
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self._tls_client_options_factory,
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self._srv_resolver,
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parsed_uri,
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)
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@implementer(IStreamClientEndpoint)
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class MatrixHostnameEndpoint:
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"""An endpoint that resolves matrix:// URLs using Matrix server name
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resolution (i.e. via SRV). Does not check for well-known delegation.
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Args:
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reactor: twisted reactor to use for underlying requests
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tls_client_options_factory:
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factory to use for fetching client tls options, or none to disable TLS.
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srv_resolver: The SRV resolver to use
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parsed_uri: The parsed URI that we're wanting to connect to.
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"""
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def __init__(
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self,
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reactor: IReactorCore,
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tls_client_options_factory: Optional[FederationPolicyForHTTPS],
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srv_resolver: SrvResolver,
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parsed_uri: URI,
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):
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self._reactor = reactor
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self._parsed_uri = parsed_uri
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# set up the TLS connection params
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#
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# XXX disabling TLS is really only supported here for the benefit of the
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# unit tests. We should make the UTs cope with TLS rather than having to make
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# the code support the unit tests.
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if tls_client_options_factory is None:
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self._tls_options = None
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else:
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self._tls_options = tls_client_options_factory.get_options(
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self._parsed_uri.host
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)
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self._srv_resolver = srv_resolver
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def connect(self, protocol_factory: IProtocolFactory) -> defer.Deferred:
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"""Implements IStreamClientEndpoint interface
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"""
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return run_in_background(self._do_connect, protocol_factory)
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async def _do_connect(self, protocol_factory: IProtocolFactory) -> None:
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first_exception = None
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server_list = await self._resolve_server()
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for server in server_list:
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host = server.host
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port = server.port
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try:
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logger.debug("Connecting to %s:%i", host.decode("ascii"), port)
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endpoint = HostnameEndpoint(self._reactor, host, port)
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if self._tls_options:
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endpoint = wrapClientTLS(self._tls_options, endpoint)
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result = await make_deferred_yieldable(
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endpoint.connect(protocol_factory)
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)
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return result
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except Exception as e:
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logger.info(
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"Failed to connect to %s:%i: %s", host.decode("ascii"), port, e
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)
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if not first_exception:
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first_exception = e
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# We return the first failure because that's probably the most interesting.
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if first_exception:
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raise first_exception
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# This shouldn't happen as we should always have at least one host/port
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# to try and if that doesn't work then we'll have an exception.
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raise Exception("Failed to resolve server %r" % (self._parsed_uri.netloc,))
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async def _resolve_server(self) -> List[Server]:
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"""Resolves the server name to a list of hosts and ports to attempt to
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connect to.
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"""
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if self._parsed_uri.scheme != b"matrix":
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return [Server(host=self._parsed_uri.host, port=self._parsed_uri.port)]
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# Note: We don't do well-known lookup as that needs to have happened
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# before now, due to needing to rewrite the Host header of the HTTP
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# request.
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# We reparse the URI so that defaultPort is -1 rather than 80
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parsed_uri = urllib.parse.urlparse(self._parsed_uri.toBytes())
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host = parsed_uri.hostname
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port = parsed_uri.port
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# If there is an explicit port or the host is an IP address we bypass
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# SRV lookups and just use the given host/port.
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if port or _is_ip_literal(host):
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return [Server(host, port or 8448)]
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server_list = await self._srv_resolver.resolve_service(b"_matrix._tcp." + host)
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if server_list:
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return server_list
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# No SRV records, so we fallback to host and 8448
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return [Server(host, 8448)]
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def _is_ip_literal(host: bytes) -> bool:
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"""Test if the given host name is either an IPv4 or IPv6 literal.
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Args:
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host: The host name to check
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Returns:
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True if the hostname is an IP address literal.
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"""
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host_str = host.decode("ascii")
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try:
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IPAddress(host_str)
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return True
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except AddrFormatError:
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return False
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