Add support for TLS SNI in httpdownloader

[Cas]

Sites that use cloudflare require TLSv1.2 and use SNI.

From forum: ​http://forum.deluge-torrent.org/viewtopic.php?f=7&p=218087#p218087

[DEBUG   ] 11:54:50 addtorrentdialog:715 Download failed: [Failure instance: Traceback: <class 'OpenSSL.SSL.Error'>: [('SSL routines', 'SSL23_GET_SERVER_HELLO', 'tlsv1 alert internal error')]
twisted/internet/selectreactor.py:149:_doReadOrWrite
twisted/internet/tcp.py:209:doRead
twisted/internet/tcp.py:215:_dataReceived
twisted/protocols/tls.py:415:dataReceived
--- <exception caught here> ---
twisted/protocols/tls.py:554:_write
OpenSSL/SSL.py:1271:send
OpenSSL/SSL.py:1187:_raise_ssl_error
OpenSSL/_util.py:48:exception_from_error_queue
]

As this is now supported in Twisted >= 14 we can add support.

To verify if this is the issue a simply test without the server name:

openssl s_client -connect www.seo.com:443
> ...
> 139785801238176:error:14077438:SSL routines:SSL23_GET_SERVER_HELLO:tlsv1 alert internal error:s23_clnt.c:770:
> ...

By adding the server name in the request it will now pass:

openssl s_client -connect www.seo.com:443 -servername seo.com

[Cas]

For reference here is the current working code:

deluge/httpdownloader.py

@@ -211 +211 @@
     factory = HTTPDownloader(url, filename, callback, headers, force_filename, allow_compression)
     if scheme == "https":
         from twisted.internet import ssl
-        reactor.connectSSL(host, port, factory, ssl.ClientContextFactory())
+        from twisted.internet._sslverify import ClientTLSOptions
+
+        class TLSSNIContextFactory(ssl.ClientContextFactory):
+            def getContext(self, hostname=None, port=None):
+                ctx = ssl.ClientContextFactory.getContext(self)
+                ClientTLSOptions(host, ctx)
+                return ctx
+
+        reactor.connectSSL(host, port, factory, TLSSNIContextFactory())
     else:
         reactor.connectTCP(host, port, factory)
 

[Cas]

Fixed 1.3-stable: [697c22a46cfc]