Use TLS SNI extension with pyOpenSSL

Use TLS SNI extension in the client, if pyOpenSSL is available.

This fixes resource fetches to https servers that require the
extension. These are typically cdn servers.

Example of such server, without SNI:

$ openssl s_client -connect cdn3.vox-cdn.com:443
CONNECTED(00000003)
140434795792032:error:14077410:SSL routines:SSL23_GET_SERVER_HELLO:sslv3 alert handshake failure:s23_clnt.c:732:
...

With SNI:

$ openssl s_client -connect cdn3.vox-cdn.com:443 -servername cdn3.vox-cdn.com
 CONNECTED(00000003)
depth=3 C = US, O = "The Go Daddy Group, Inc.", OU = Go Daddy Class 2
 Certification Authority
....

Author: kkinnunen

Diff for: httpclient.py

@@ -174,15 +174,50 @@ class DetailedHTTPConnection(httplib.HTTPConnection):
   """Preserve details relevant to replaying connections."""
   response_class = DetailedHTTPResponse
 
-
 class DetailedHTTPSResponse(DetailedHTTPResponse):
   """Preserve details relevant to replaying SSL responses."""
   pass
 
+try:
+  from OpenSSL import SSL
+  import OpenSSL.version
+  from socket import _fileobject
+  if OpenSSL.version <= (0, 12):
+    raise ImportError("Need pyOpenSSL > 0.12 for client usage")
+
+  SSLConnection = SSL.Connection
 
-class DetailedHTTPSConnection(httplib.HTTPSConnection):
-  """Preserve details relevant to replaying SSL connections."""
-  response_class = DetailedHTTPSResponse
+  class FOSSLConnection(SSLConnection):
+    """A connection object that can be accessed as a file object.
+    Needed so that httplib can use SSL.Connection.
+    """
+    def makefile(self, mode, bufsize=-1):
+      return _fileobject(self, mode, bufsize)
+
+  class DetailedHTTPSConnection(DetailedHTTPConnection):
+    """Preserve details relevant to replaying SSL connections.
+    A pyOpenSSL implementation of DetailedHTTPConnection. This
+    supports TLS SNI extension, which is needed for some content
+    distribution networks."""
+    response_class = DetailedHTTPSResponse
+    default_port = httplib.HTTPS_PORT
+    def __init__(self, host, port):
+      DetailedHTTPConnection.__init__(self, host, port)
+      self.context = SSL.Context(SSL.SSLv23_METHOD)
+
+    def connect(self):
+      DetailedHTTPConnection.connect(self)
+      self.sock = FOSSLConnection(self.context, self.sock)
+      self.sock.set_connect_state()
+      self.sock.set_tlsext_host_name(self._host_name)
+      self.sock.do_handshake()
+
+except ImportError, e:
+  class DetailedHTTPSConnection(httplib.HTTPSConnection):
+    """Preserve details relevant to replaying SSL connections."""
+    response_class = DetailedHTTPSResponse
+    def set_host_name(self, dummy):
+      pass
 
 
 class RealHttpFetch(object):
@@ -292,6 +327,7 @@ def _get_connection(self, request_host, request_port, is_ssl):
 
     if is_ssl:
       connection = DetailedHTTPSConnection(connection_ip, connection_port)
+      connection.set_host_name(connection_host)
       if system_proxy:
         connection.set_tunnel(self, request_host, request_port)
     else: