Python Cookbook 2Nd Edition Jun 1002005 [Electronic resources]

David Ascher, Alex Martelli, Anna Ravenscroft

نسخه متنی -صفحه : 394/ 287

Recipe 14.8. Authenticating with a Proxy for HTTPS Navigation

Credit: John Nielsen

Problem

You need to use httplib for HTTPS navigation through a proxy that requires basic authentication, but httplib out of the box supports HTTPS only through proxies that do not require authentication.

Solution

Unfortunately, it takes a wafer-thin amount of trickery to achieve this recipe's task. Here is a script that is just tricky enough:

import httplib, base64, socket
# parameters for the script
user = 'proxy_login'; passwd = 'proxy_pass'
host = 'login.yahoo.com'; port = 443
phost = 'proxy_host'; pport = 80
# setup basic authentication
user_pass = base64.encodestring(user+':'+passwd)
proxy_authorization = 'Proxy-authorization: Basic '+user_pass+'\r\n'
proxy_connect = 'CONNECT %s:%s HTTP/1.0\r\n' % (host, port)
user_agent = 'User-Agent: python\r\n'
proxy_pieces = proxy_connect+proxy_authorization+user_agent+'\r\n'
# connect to the proxy
proxy_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
proxy_socket.connect((phost, pport))
proxy_socket.sendall(proxy_pieces+'\r\n')
response = proxy_socket.recv(8192)
status = response.split( )[1]
if status!='200':
raise IOError, 'Connecting to proxy: status=%s' % status
# trivial setup for SSL socket
ssl = socket.ssl(proxy_socket, None, None)
sock = httplib.FakeSocket(proxy_socket, ssl)
# initialize httplib and replace
 the connection's socket with the SSL one
h = httplib.HTTPConnection('localhost')
h.sock = sock
# and finally, use the now-HTTPS httplib connection as you wish
h.request('GET', '/')
r = h.getresponse( )
print r.read( )

Discussion

HTTPS is essentially HTTP spoken on top of an SSL connection rather than a plain socket. So, this recipe connects to the proxy with basic authentication at the very lowest level of Python socket programming, wraps an SSL socket around the proxy connection thus secured, and finally plays a little trick under httplib's nose to use that laboriously constructed SSL socket in place of the plain socket in an HTTPConnection instance. From that point onwards, you can use the normal httplib approach as you wish.