313 lines
11 KiB
Python
313 lines
11 KiB
Python
# Copyright 2019 The Matrix.org Foundation C.I.C.
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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 base64
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import logging
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import re
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from typing import Optional, Tuple
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from urllib.request import getproxies_environment, proxy_bypass_environment
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import attr
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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.python.failure import Failure
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from twisted.web.client import URI, BrowserLikePolicyForHTTPS, _AgentBase
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from twisted.web.error import SchemeNotSupported
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from twisted.web.http_headers import Headers
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from twisted.web.iweb import IAgent, IPolicyForHTTPS
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from synapse.http.connectproxyclient import HTTPConnectProxyEndpoint
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logger = logging.getLogger(__name__)
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_VALID_URI = re.compile(br"\A[\x21-\x7e]+\Z")
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@attr.s
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class ProxyCredentials:
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username_password = attr.ib(type=bytes)
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def as_proxy_authorization_value(self) -> bytes:
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"""
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Return the value for a Proxy-Authorization header (i.e. 'Basic abdef==').
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Returns:
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A transformation of the authentication string the encoded value for
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a Proxy-Authorization header.
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"""
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# Encode as base64 and prepend the authorization type
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return b"Basic " + base64.encodebytes(self.username_password)
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@implementer(IAgent)
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class ProxyAgent(_AgentBase):
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"""An Agent implementation which will use an HTTP proxy if one was requested
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Args:
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reactor: twisted reactor to place outgoing
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connections.
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proxy_reactor: twisted reactor to use for connections to the proxy server
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reactor might have some blacklisting applied (i.e. for DNS queries),
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but we need unblocked access to the proxy.
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contextFactory (IPolicyForHTTPS): A factory for TLS contexts, to control the
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verification parameters of OpenSSL. The default is to use a
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`BrowserLikePolicyForHTTPS`, so unless you have special
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requirements you can leave this as-is.
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connectTimeout (Optional[float]): The amount of time that this Agent will wait
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for the peer to accept a connection, in seconds. If 'None',
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HostnameEndpoint's default (30s) will be used.
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This is used for connections to both proxies and destination servers.
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bindAddress (bytes): The local address for client sockets to bind to.
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pool (HTTPConnectionPool|None): connection pool to be used. If None, a
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non-persistent pool instance will be created.
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use_proxy (bool): Whether proxy settings should be discovered and used
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from conventional environment variables.
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"""
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def __init__(
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self,
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reactor,
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proxy_reactor=None,
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contextFactory: Optional[IPolicyForHTTPS] = None,
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connectTimeout=None,
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bindAddress=None,
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pool=None,
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use_proxy=False,
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):
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contextFactory = contextFactory or BrowserLikePolicyForHTTPS()
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_AgentBase.__init__(self, reactor, pool)
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if proxy_reactor is None:
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self.proxy_reactor = reactor
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else:
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self.proxy_reactor = proxy_reactor
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self._endpoint_kwargs = {}
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if connectTimeout is not None:
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self._endpoint_kwargs["timeout"] = connectTimeout
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if bindAddress is not None:
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self._endpoint_kwargs["bindAddress"] = bindAddress
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http_proxy = None
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https_proxy = None
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no_proxy = None
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if use_proxy:
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proxies = getproxies_environment()
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http_proxy = proxies["http"].encode() if "http" in proxies else None
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https_proxy = proxies["https"].encode() if "https" in proxies else None
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no_proxy = proxies["no"] if "no" in proxies else None
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# Parse credentials from https proxy connection string if present
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self.https_proxy_creds, https_proxy = parse_username_password(https_proxy)
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self.http_proxy_endpoint = _http_proxy_endpoint(
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http_proxy, self.proxy_reactor, **self._endpoint_kwargs
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)
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self.https_proxy_endpoint = _http_proxy_endpoint(
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https_proxy, self.proxy_reactor, **self._endpoint_kwargs
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)
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self.no_proxy = no_proxy
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self._policy_for_https = contextFactory
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self._reactor = reactor
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def request(self, method, uri, headers=None, bodyProducer=None):
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"""
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Issue a request to the server indicated by the given uri.
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Supports `http` and `https` schemes.
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An existing connection from the connection pool may be used or a new one may be
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created.
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See also: twisted.web.iweb.IAgent.request
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Args:
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method (bytes): The request method to use, such as `GET`, `POST`, etc
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uri (bytes): The location of the resource to request.
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headers (Headers|None): Extra headers to send with the request
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bodyProducer (IBodyProducer|None): An object which can generate bytes to
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make up the body of this request (for example, the properly encoded
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contents of a file for a file upload). Or, None if the request is to
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have no body.
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Returns:
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Deferred[IResponse]: completes when the header of the response has
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been received (regardless of the response status code).
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Can fail with:
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SchemeNotSupported: if the uri is not http or https
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twisted.internet.error.TimeoutError if the server we are connecting
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to (proxy or destination) does not accept a connection before
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connectTimeout.
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... other things too.
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"""
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uri = uri.strip()
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if not _VALID_URI.match(uri):
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raise ValueError("Invalid URI {!r}".format(uri))
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parsed_uri = URI.fromBytes(uri)
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pool_key = (parsed_uri.scheme, parsed_uri.host, parsed_uri.port)
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request_path = parsed_uri.originForm
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should_skip_proxy = False
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if self.no_proxy is not None:
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should_skip_proxy = proxy_bypass_environment(
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parsed_uri.host.decode(),
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proxies={"no": self.no_proxy},
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)
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if (
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parsed_uri.scheme == b"http"
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and self.http_proxy_endpoint
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and not should_skip_proxy
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):
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# Cache *all* connections under the same key, since we are only
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# connecting to a single destination, the proxy:
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pool_key = ("http-proxy", self.http_proxy_endpoint)
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endpoint = self.http_proxy_endpoint
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request_path = uri
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elif (
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parsed_uri.scheme == b"https"
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and self.https_proxy_endpoint
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and not should_skip_proxy
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):
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connect_headers = Headers()
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# Determine whether we need to set Proxy-Authorization headers
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if self.https_proxy_creds:
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# Set a Proxy-Authorization header
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connect_headers.addRawHeader(
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b"Proxy-Authorization",
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self.https_proxy_creds.as_proxy_authorization_value(),
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)
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endpoint = HTTPConnectProxyEndpoint(
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self.proxy_reactor,
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self.https_proxy_endpoint,
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parsed_uri.host,
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parsed_uri.port,
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headers=connect_headers,
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)
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else:
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# not using a proxy
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endpoint = HostnameEndpoint(
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self._reactor, parsed_uri.host, parsed_uri.port, **self._endpoint_kwargs
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)
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logger.debug("Requesting %s via %s", uri, endpoint)
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if parsed_uri.scheme == b"https":
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tls_connection_creator = self._policy_for_https.creatorForNetloc(
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parsed_uri.host, parsed_uri.port
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)
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endpoint = wrapClientTLS(tls_connection_creator, endpoint)
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elif parsed_uri.scheme == b"http":
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pass
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else:
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return defer.fail(
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Failure(
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SchemeNotSupported("Unsupported scheme: %r" % (parsed_uri.scheme,))
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)
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)
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return self._requestWithEndpoint(
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pool_key, endpoint, method, parsed_uri, headers, bodyProducer, request_path
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)
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def _http_proxy_endpoint(proxy: Optional[bytes], reactor, **kwargs):
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"""Parses an http proxy setting and returns an endpoint for the proxy
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Args:
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proxy: the proxy setting in the form: [<username>:<password>@]<host>[:<port>]
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Note that compared to other apps, this function currently lacks support
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for specifying a protocol schema (i.e. protocol://...).
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reactor: reactor to be used to connect to the proxy
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kwargs: other args to be passed to HostnameEndpoint
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Returns:
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interfaces.IStreamClientEndpoint|None: endpoint to use to connect to the proxy,
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or None
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"""
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if proxy is None:
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return None
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# Parse the connection string
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host, port = parse_host_port(proxy, default_port=1080)
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return HostnameEndpoint(reactor, host, port, **kwargs)
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def parse_username_password(proxy: bytes) -> Tuple[Optional[ProxyCredentials], bytes]:
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"""
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Parses the username and password from a proxy declaration e.g
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username:password@hostname:port.
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Args:
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proxy: The proxy connection string.
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Returns
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An instance of ProxyCredentials and the proxy connection string with any credentials
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stripped, i.e u:p@host:port -> host:port. If no credentials were found, the
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ProxyCredentials instance is replaced with None.
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"""
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if proxy and b"@" in proxy:
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# We use rsplit here as the password could contain an @ character
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credentials, proxy_without_credentials = proxy.rsplit(b"@", 1)
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return ProxyCredentials(credentials), proxy_without_credentials
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return None, proxy
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def parse_host_port(hostport: bytes, default_port: int = None) -> Tuple[bytes, int]:
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"""
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Parse the hostname and port from a proxy connection byte string.
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Args:
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hostport: The proxy connection string. Must be in the form 'host[:port]'.
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default_port: The default port to return if one is not found in `hostport`.
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Returns:
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A tuple containing the hostname and port. Uses `default_port` if one was not found.
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"""
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if b":" in hostport:
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host, port = hostport.rsplit(b":", 1)
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try:
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port = int(port)
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return host, port
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except ValueError:
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# the thing after the : wasn't a valid port; presumably this is an
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# IPv6 address.
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pass
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return hostport, default_port
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