# Copyright 2019 The Matrix.org Foundation C.I.C.
#
# 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 logging
import re
from typing import Any, Dict, Optional, Tuple
from urllib.parse import urlparse
from urllib.request import ( # type: ignore[attr-defined]
getproxies_environment,
proxy_bypass_environment,
)
from zope.interface import implementer
from twisted.internet import defer
from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
from twisted.internet.interfaces import IReactorCore, IStreamClientEndpoint
from twisted.python.failure import Failure
from twisted.web.client import (
URI,
BrowserLikePolicyForHTTPS,
HTTPConnectionPool,
_AgentBase,
)
from twisted.web.error import SchemeNotSupported
from twisted.web.http_headers import Headers
from twisted.web.iweb import IAgent, IBodyProducer, IPolicyForHTTPS
from synapse.http.connectproxyclient import HTTPConnectProxyEndpoint, ProxyCredentials
from synapse.types import ISynapseReactor
logger = logging.getLogger(__name__)
_VALID_URI = re.compile(br"\A[\x21-\x7e]+\Z")
@implementer(IAgent)
class ProxyAgent(_AgentBase):
"""An Agent implementation which will use an HTTP proxy if one was requested
Args:
reactor: twisted reactor to place outgoing
connections.
proxy_reactor: twisted reactor to use for connections to the proxy server
reactor might have some blacklisting applied (i.e. for DNS queries),
but we need unblocked access to the proxy.
contextFactory: A factory for TLS contexts, to control the
verification parameters of OpenSSL. The default is to use a
`BrowserLikePolicyForHTTPS`, so unless you have special
requirements you can leave this as-is.
connectTimeout: The amount of time that this Agent will wait
for the peer to accept a connection, in seconds. If 'None',
HostnameEndpoint's default (30s) will be used.
This is used for connections to both proxies and destination servers.
bindAddress: The local address for client sockets to bind to.
pool: connection pool to be used. If None, a
non-persistent pool instance will be created.
use_proxy: Whether proxy settings should be discovered and used
from conventional environment variables.
Raises:
ValueError if use_proxy is set and the environment variables
contain an invalid proxy specification.
RuntimeError if no tls_options_factory is given for a https connection
"""
def __init__(
self,
reactor: IReactorCore,
proxy_reactor: Optional[ISynapseReactor] = None,
contextFactory: Optional[IPolicyForHTTPS] = None,
connectTimeout: Optional[float] = None,
bindAddress: Optional[bytes] = None,
pool: Optional[HTTPConnectionPool] = None,
use_proxy: bool = False,
):
contextFactory = contextFactory or BrowserLikePolicyForHTTPS()
_AgentBase.__init__(self, reactor, pool)
if proxy_reactor is None:
self.proxy_reactor = reactor
else:
self.proxy_reactor = proxy_reactor
self._endpoint_kwargs: Dict[str, Any] = {}
if connectTimeout is not None:
self._endpoint_kwargs["timeout"] = connectTimeout
if bindAddress is not None:
self._endpoint_kwargs["bindAddress"] = bindAddress
http_proxy = None
https_proxy = None
no_proxy = None
if use_proxy:
proxies = getproxies_environment()
http_proxy = proxies["http"].encode() if "http" in proxies else None
https_proxy = proxies["https"].encode() if "https" in proxies else None
no_proxy = proxies["no"] if "no" in proxies else None
self.http_proxy_endpoint, self.http_proxy_creds = http_proxy_endpoint(
http_proxy, self.proxy_reactor, contextFactory, **self._endpoint_kwargs
)
self.https_proxy_endpoint, self.https_proxy_creds = http_proxy_endpoint(
https_proxy, self.proxy_reactor, contextFactory, **self._endpoint_kwargs
)
self.no_proxy = no_proxy
self._policy_for_https = contextFactory
self._reactor = reactor
def request(
self,
method: bytes,
uri: bytes,
headers: Optional[Headers] = None,
bodyProducer: Optional[IBodyProducer] = None,
) -> defer.Deferred:
"""
Issue a request to the server indicated by the given uri.
Supports `http` and `https` schemes.
An existing connection from the connection pool may be used or a new one may be
created.
See also: twisted.web.iweb.IAgent.request
Args:
method: The request method to use, such as `GET`, `POST`, etc
uri: The location of the resource to request.
headers: Extra headers to send with the request
bodyProducer: 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[IResponse]: completes when the header of the response has
been received (regardless of the response status code).
Can fail with:
SchemeNotSupported: if the uri is not http or https
twisted.internet.error.TimeoutError if the server we are connecting
to (proxy or destination) does not accept a connection before
connectTimeout.
... other things too.
"""
uri = uri.strip()
if not _VALID_URI.match(uri):
raise ValueError(f"Invalid URI {uri!r}")
parsed_uri = URI.fromBytes(uri)
pool_key = f"{parsed_uri.scheme!r}{parsed_uri.host!r}{parsed_uri.port}"
request_path = parsed_uri.originForm
should_skip_proxy = False
if self.no_proxy is not None:
should_skip_proxy = proxy_bypass_environment(
parsed_uri.host.decode(),
proxies={"no": self.no_proxy},
)
if (
parsed_uri.scheme == b"http"
and self.http_proxy_endpoint
and not should_skip_proxy
):
# Determine whether we need to set Proxy-Authorization headers
if self.http_proxy_creds:
# Set a Proxy-Authorization header
if headers is None:
headers = Headers()
headers.addRawHeader(
b"Proxy-Authorization",
self.http_proxy_creds.as_proxy_authorization_value(),
)
# Cache *all* connections under the same key, since we are only
# connecting to a single destination, the proxy:
pool_key = "http-proxy"
endpoint = self.http_proxy_endpoint
request_path = uri
elif (
parsed_uri.scheme == b"https"
and self.https_proxy_endpoint
and not should_skip_proxy
):
endpoint = HTTPConnectProxyEndpoint(
self.proxy_reactor,
self.https_proxy_endpoint,
parsed_uri.host,
parsed_uri.port,
self.https_proxy_creds,
)
else:
# not using a proxy
endpoint = HostnameEndpoint(
self._reactor, parsed_uri.host, parsed_uri.port, **self._endpoint_kwargs
)
logger.debug("Requesting %s via %s", uri, endpoint)
if parsed_uri.scheme == b"https":
tls_connection_creator = self._policy_for_https.creatorForNetloc(
parsed_uri.host, parsed_uri.port
)
endpoint = wrapClientTLS(tls_connection_creator, endpoint)
elif parsed_uri.scheme == b"http":
pass
else:
return defer.fail(
Failure(
SchemeNotSupported("Unsupported scheme: %r" % (parsed_uri.scheme,))
)
)
return self._requestWithEndpoint(
pool_key, endpoint, method, parsed_uri, headers, bodyProducer, request_path
)
def http_proxy_endpoint(
proxy: Optional[bytes],
reactor: IReactorCore,
tls_options_factory: Optional[IPolicyForHTTPS],
**kwargs,
) -> Tuple[Optional[IStreamClientEndpoint], Optional[ProxyCredentials]]:
"""Parses an http proxy setting and returns an endpoint for the proxy
Args:
proxy: the proxy setting in the form: [scheme://][<username>:<password>@]<host>[:<port>]
This currently supports http:// and https:// proxies.
A hostname without scheme is assumed to be http.
reactor: reactor to be used to connect to the proxy
tls_options_factory: the TLS options to use when connecting through a https proxy
kwargs: other args to be passed to HostnameEndpoint
Returns:
a tuple of
endpoint to use to connect to the proxy, or None
ProxyCredentials or if no credentials were found, or None
Raise:
ValueError if proxy has no hostname or unsupported scheme.
RuntimeError if no tls_options_factory is given for a https connection
"""
if proxy is None:
return None, None
# Note: urlsplit/urlparse cannot be used here as that does not work (for Python
# 3.9+) on scheme-less proxies, e.g. host:port.
scheme, host, port, credentials = parse_proxy(proxy)
proxy_endpoint = HostnameEndpoint(reactor, host, port, **kwargs)
if scheme == b"https":
if tls_options_factory:
tls_options = tls_options_factory.creatorForNetloc(host, port)
proxy_endpoint = wrapClientTLS(tls_options, proxy_endpoint)
else:
raise RuntimeError(
f"No TLS options for a https connection via proxy {proxy!s}"
)
return proxy_endpoint, credentials
def parse_proxy(
proxy: bytes, default_scheme: bytes = b"http", default_port: int = 1080
) -> Tuple[bytes, bytes, int, Optional[ProxyCredentials]]:
"""
Parse a proxy connection string.
Given a HTTP proxy URL, breaks it down into components and checks that it
has a hostname (otherwise it is not useful to us when trying to find a
proxy) and asserts that the URL has a scheme we support.
Args:
proxy: The proxy connection string. Must be in the form '[scheme://][<username>:<password>@]host[:port]'.
default_scheme: The default scheme to return if one is not found in `proxy`. Defaults to http
default_port: The default port to return if one is not found in `proxy`. Defaults to 1080
Returns:
A tuple containing the scheme, hostname, port and ProxyCredentials.
If no credentials were found, the ProxyCredentials instance is replaced with None.
Raise:
ValueError if proxy has no hostname or unsupported scheme.
"""
# First check if we have a scheme present
# Note: urlsplit/urlparse cannot be used (for Python # 3.9+) on scheme-less proxies, e.g. host:port.
if b"://" not in proxy:
proxy = b"".join([default_scheme, b"://", proxy])
url = urlparse(proxy)
if not url.hostname:
raise ValueError("Proxy URL did not contain a hostname! Please specify one.")
if url.scheme not in (b"http", b"https"):
raise ValueError(
f"Unknown proxy scheme {url.scheme!s}; only 'http' and 'https' is supported."
)
credentials = None
if url.username and url.password:
credentials = ProxyCredentials(b"".join([url.username, b":", url.password]))
return url.scheme, url.hostname, url.port or default_port, credentials