On Mon, Apr 15, 2019 at 5:45 PM Jeremy Harris <[email protected]> wrote: > > On 15/04/2019 07:33, Nikos Mavrogiannopoulos wrote: > > On Sun, Apr 14, 2019 at 9:19 PM Jeremy Harris <[email protected]> wrote: > >> > >> On 14/04/2019 15:09, Nikos Mavrogiannopoulos wrote: > >>> On Sat, Apr 13, 2019 at 8:20 PM Jeremy Harris <[email protected]> wrote: > >>>> GnuTLS 3.6.7 > >>>> > >>>> On resuming a TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256 session > >>>> I'm getting a reported ciphersuite TLS1.3:NULL:256 > >>>> > >>>> The "NULL" derives from gnutls_cipher_suite_get_name() and > >>>> the difference from the original is that the kx has changed > >>>> from 12 (GNUTLS_KX_ECDHE_RSA) to 14 (GNUTLS_KX_ECDHE_PSK). > >>>> > >>>> > >>>> Should I be using gnutls_kx_get_name() (&c for cipher and mac) > >>>> separately, rather than gnutls_cipher_suite_get_name() ? > >>> > >>> There are no key exchange methods under TLS1.3, or they are kind of > >>> implied, that's why you see null there. I'd recommend to use > >>> gnutls_session_get_desc() which gives a description applicable for > >>> gnutls but uniform across versions. > >> > >> Using that, the original connection gets > >> (TLS1.3)-(ECDHE-SECP256R1)-(RSA-PSS-RSAE-SHA256)-(AES-256-GCM) > >> and the resumed session gets > >> (TLS1.3)-(ECDHE-PSK-SECP256R1)-(AES-256-GCM) > >> > >> Assuming the ECDHE is "implied by the TLS1.3" and the PSK part > >> is saying the key was shared by the initial connection... > >> what has happened to the cipher? > > > > The cipher is in both cases AES-256-GCM. What has changed is the key > > exchange and authentication method. > > Ah. So what is the distinction between the elements > (ECDHE-SECP256R1) and (RSA-PSS-RSAE-SHA256) ?
The first is key exchange, the latter is the authentication method (of the key exchange), i.e., the algorithm used to sign it. > Also, where did the MAC information go? Is it still valid and required > to use gnutls_mac_get_name(gnutls_mac_get()) ? The algorithms are now AEAD, and the MAC is part of the cipher (in this case GCM). What gnutls_mac_get() will return is AEAD. Most of these questions should be answered by this post: https://nikmav.blogspot.com/2018/05/gnutls-and-tls-13.html regards, Nikos _______________________________________________ Gnutls-help mailing list [email protected] http://lists.gnupg.org/mailman/listinfo/gnutls-help
