Does M2Crypto have client-side Server Name Indication (SNI) support?

Question

I have a python SSL client written using M2Crypto to which I'd like to add SNI support.

Looks like with OpenSSL one would use ```SSL_set_tlsext_host_name(ssl, servername)''' but I don't see that function exposed in the M2Crypto API.

Am I just missing it or is there some other way to do this?

Answer 1

I looked at the latest code in the M2Crypto SVN repository, and there is no support (yet) fro SNI. I needed SNI too so in the true open source spirit I wrote a patch for it :-)

The patch to add it is actually very simple:

Index: SWIG/_ssl.i
===================================================================
--- SWIG/_ssl.i (revision 739)
+++ SWIG/_ssl.i (working copy)
@@ -14,6 +14,7 @@
 #include <openssl/bio.h>
 #include <openssl/dh.h>
 #include <openssl/ssl.h>
+#include <openssl/tls1.h>
 #include <openssl/x509.h>
 %}

@@ -375,6 +376,10 @@
     return SSL_get_mode(ssl);
 }

+long ssl_set_tlsext_host_name(SSL *ssl, const char *name) {
+    return SSL_set_tlsext_host_name(ssl, name);
+}
+
 void ssl_set_client_CA_list_from_file(SSL *ssl, const char *ca_file) {
     SSL_set_client_CA_list(ssl, SSL_load_client_CA_file(ca_file));
 }
Index: M2Crypto/SSL/Connection.py
===================================================================
--- M2Crypto/SSL/Connection.py  (revision 739)
+++ M2Crypto/SSL/Connection.py  (working copy)
@@ -359,3 +359,7 @@

     def set_post_connection_check_callback(self, postConnectionCheck):
         self.postConnectionCheck = postConnectionCheck
+
+    def set_tlsext_host_name(self, name):
+        "Set the requested hostname for the SNI (Server Name Indication) extension"
+        m2.ssl_set_tlsext_host_name(self.ssl, name)

This has of course also been submitted to the M2Crypto bug/enhancement tracker.