Hi,
I would like to ask if anyone here has actually been able to trim the EC Supported Groups in the Client Hello with a TLS-ECDHE cipher using the APIs described in the OpenSSL v1.0.2 manpage for SSL_CTX_set1_curves()
My shared objects are built using OpenSSL v1.0.2t with FIPS Object Module v2.0.5 . The TLS handshake pcap has always shown myCipher ("ECDHE-RSA-AES128-GCM-SHA256") in the Client Hello correctly, accompanied with 13 curves in the Supported Group Extension. However, enhancing SSL_CTX myCtx to restrict the curves to just 3 (P-521:P384:P256) still show the same 13 curves as in the pcap. The man page doesn't suggest nor do i see any reason why FIPS should prevent this from working.
//existing working code
if((myCtx = SSL_CTX_new(SSL_METHOD *)TLSv1_2_method()) == NULL)
return;
if((SSL_CTX_set_cipher_list(myCtx, myCipher) != 1))
return;
//enhancement, not working
if(SSL_CTX_set1_curves(myCtx, "P-521:P-384:P-256", 3)) != 1))
return;
The API returns 0 (suggesting no error), but pcap shows no change, i.e. still shows the std. 13 curves.
Trying a code snippet involving SSL_CONF_cmd(myConfCtx, "-named-curve", "P-256") suggested in this link , available prior to SSL_CTX_set1_curves() introduction in v1.0.2, didn’t help either.
Thank you for any guidance you can provide.
Rohit
