Title: urrlib2 opener for SSL proxy (CONNECT method)
Submitter: Alessandro Budai (other recipes)
Last Updated: 2005/11/16
Version no: 1.1
Category: Network

Description:

This small module builds an urllib2 opener that can be used to make a connection through a proxy using the http CONNECT method (that can be used to proxy SSLconnections).
The current urrlib2 seems to not support this method.

Source: Text Source

# urllib2 opener to connection through a proxy using the CONNECT method, (useful for SSL)
# tested with python 2.4

import urllib2
import urllib
import httplib
import socket


class ProxyHTTPConnection(httplib.HTTPConnection):

    _ports = {'http' : 80, 'https' : 443}


    def request(self, method, url, body=None, headers={}):
        #request is called before connect, so can interpret url and get
        #real host/port to be used to make CONNECT request to proxy
        proto, rest = urllib.splittype(url)
        if proto is None:
            raise ValueError, "unknown URL type: %s" % url
        #get host
        host, rest = urllib.splithost(rest)
        #try to get port
        host, port = urllib.splitport(host)
        #if port is not defined try to get from proto
        if port is None:
            try:
                port = self._ports[proto]
            except KeyError:
                raise ValueError, "unknown protocol for: %s" % url
        self._real_host = host
        self._real_port = port
        httplib.HTTPConnection.request(self, method, url, body, headers)
        

    def connect(self):
        httplib.HTTPConnection.connect(self)
        #send proxy CONNECT request
        self.send("CONNECT %s:%d HTTP/1.0\r\n\r\n" % (self._real_host, self._real_port))
        #expect a HTTP/1.0 200 Connection established
        response = self.response_class(self.sock, strict=self.strict, method=self._method)
        (version, code, message) = response._read_status()
        #probably here we can handle auth requests...
        if code != 200:
            #proxy returned and error, abort connection, and raise exception
            self.close()
            raise socket.error, "Proxy connection failed: %d %s" % (code, message.strip())
        #eat up header block from proxy....
        while True:
            #should not use directly fp probablu
            line = response.fp.readline()
            if line == '\r\n': break


class ProxyHTTPSConnection(ProxyHTTPConnection):
    
    default_port = 443

    def __init__(self, host, port = None, key_file = None, cert_file = None, strict = None):
        ProxyHTTPConnection.__init__(self, host, port)
        self.key_file = key_file
        self.cert_file = cert_file
    
    def connect(self):
        ProxyHTTPConnection.connect(self)
        #make the sock ssl-aware
        ssl = socket.ssl(self.sock, self.key_file, self.cert_file)
        self.sock = httplib.FakeSocket(self.sock, ssl)
        
                                       
class ConnectHTTPHandler(urllib2.HTTPHandler):

    def do_open(self, http_class, req):
        return urllib2.HTTPHandler.do_open(self, ProxyHTTPConnection, req)


class ConnectHTTPSHandler(urllib2.HTTPSHandler):

    def do_open(self, http_class, req):
        return urllib2.HTTPSHandler.do_open(self, ProxyHTTPSConnection, req)


if __name__ == '__main__':
    
    import sys
    
    opener = urllib2.build_opener(ConnectHTTPHandler, ConnectHTTPSHandler)
    urllib2.install_opener(opener)
    req = urllib2.Request(url='https://192.168.1.1')
    req.set_proxy('192.168.1.254:3128', 'https')
    f = urllib2.urlopen(req)
    print f.read()

Discussion:

This module provides an openers that can be used with urrlib2 to make a connection through a proxy that supports the CONNECT method.
The ProxyHTTPConnection class takes care of connecting to the proxy, sending the CONNECT string and interpreting results. In case of success (http code 200 reply) we are connected to remote host and everything can go as usual.
When connecting to an SSL enabled host ProxyHTTPSConnection, after a successfull connect, makes the socket ssl-aware.
Currently no authentication scheme is supported, but can be easily added (maybe even resorting to urrlib2 support).