[gnutls-devel] gnutls_certificate_verify_peers* question

[Jaak Ristioja]

On 19.02.2013 14:05, Nikos Mavrogiannopoulos wrote:
> On Tue, Feb 19, 2013 at 10:10 AM, Jaak Ristioja <jaak.ristioja at cyber.ee> wrote:
>> Hello!
>> If I use the gnutls_certificate_verify_peers2() or
>> gnutls_certificate_verify_peers3() functions in the callback set using
>> gnutls_certificate_set_verify_function(), do those functions also verify
>> that the peer has the private key corresponding to the public key in the
>> certificate, or is it done elsewhere outside of the callback?
> 
> Hello,
>  For simplicity I'll focus on the signing ciphersuites. In that case,
> during the handshake you receive a message from the peer that contains
> handshake parameters (it is the random nonces and DH params in server
> side) that are signed. This message is verified in gnutls_handshake()
> directly (i.e. you have no say on that). If that succeeds the callback
> takes control and verifies whether the parameters (i.e. the
> certificate) used in the previous signature verification are
> acceptable.

Do I understand it correctly, that once the callback (set using
gnutls_certificate_set_verify_function) is called during handshake, it
has already been verified that the peer holds the private key for the
public key in the certificate the peer provides?

Thanks,
Jaak