net: disable SSLv3 fallback.

net/socket/ssl_client_socket_nss.cc

Index: net/socket/ssl_client_socket_nss.cc
diff --git a/net/socket/ssl_client_socket_nss.cc b/net/socket/ssl_client_socket_nss.cc
index c5869fc3503a5ddfa53abb1b9ba0aecbabbfb442..826c94b03a777b30c844214534b449aa203a3cb7 100644
--- a/net/socket/ssl_client_socket_nss.cc
+++ b/net/socket/ssl_client_socket_nss.cc
@@ -3314,6 +3314,11 @@ int SSLClientSocketNSS::DoHandshakeComplete(int result) {
   EnterFunction(result);
 
   if (result == OK) {
+    if (ssl_config_.version_fallback &&
+        ssl_config_.version_max < ssl_config_.version_fallback_min) {
+      return ERR_SSL_FALLBACK_BEYOND_MINIMUM_VERSION;

[davidben, 2014/10/07 22:06:30]

I believe we're fine, but I want to point this out:

Is this going to avoid caching the session? Otherwise NSS is going to clamp
client_version to the session's version when it tries to resume. There's an
SSL_CacheSession call that doesn't get made until later, but probably worth
checking experimentally.

Or better yet: a unit test.

[agl, 2014/10/07 23:59:54]

A very good point, thanks! Please see added unit test.

+    }
+
     // SSL handshake is completed. Let's verify the certificate.
     GotoState(STATE_VERIFY_CERT);
     // Done!