[gnutls-help] Is AES GCM only in TLS1.2 ?

[Daniel Kahn Gillmor]

On Wed 2015-05-27 16:35:52 -0400, jonetsu wrote:

> The output of the cipher listing, in FIPS mode, filtered for TLS1.2, gives:
>
> % gnutls-cli -l --priority NORMAL | grep 1.2
>
>  TLS_ECDHE_ECDSA_AES_128_GCM_SHA256
>  TLS_ECDHE_ECDSA_AES_256_GCM_SHA384
>  TLS_ECDHE_ECDSA_CAMELLIA_128_GCM_SHA256
>  TLS_ECDHE_ECDSA_CAMELLIA_256_GCM_SHA384
>  [...]

It appears you've trimmed the right-hand side of this transcript, where
TLS1.2 actually appears.

> Only GCM variation of AES.  Why is GCM the only available AES variation in TLS1.2 ?

I think you're misunderstanding the output of gnutls-cli -l, which looks
like this:

TLS_ECDHE_ECDSA_AES_128_GCM_SHA256                	0xc0, 0x2b	TLS1.2

I think this line says that the TLS_ECDHE_ECDSA_AES_128_GCM_SHA256
ciphersuite is only available for TLS 1.2 and higher (because that is
when it when it was introduced).

You'll note that no ciphersuites are listed with a "TLS1.1" label,
despite the fact that GnuTLS will connect to a peer that only handles
TLS 1.1.

Similarly, there are ciphersuites marked with SSL3.0, despite the fact
that GnuTLS does not support SSLv3 any longer (SSLv3 is old and
known-broken[0]).  These ciphersuites are listed that way because that's
the protocol version in which they were introduced.

hth,

    --dkg

[0] https://tools.ietf.org/html/draft-ietf-tls-sslv3-diediedie-03
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