Client certificate authentication

Robert Ionescu hightronicdesign at
Mon Mar 15 23:05:35 UTC 2021

Hmm ok I get it.
So, to be able to get the fingerprint for the used certificates during a
TLS handshake is possible by using the SSL_set_verify callbacks in the
application or is the mentioned postfix useful for this purpose?
Robert Ionescu

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On Mon, Mar 15, 2021 at 12:46 PM Viktor Dukhovni <openssl-users at>

> On Mon, Mar 15, 2021 at 12:23:54PM +0100, Robert Ionescu wrote:
> > I already found the callbacks for the verification process and I am
> > still trying to figure it out if it is possible to change them in a
> > way that they will print some certificate information to determine
> > which certificate was used?
> What do you mean "change them"?  These are callbacks, you register the
> callback function in the application, and then do whatever you want in
> that function, including print certificate information, if that's your
> goal.  There's nothing to "change".
> The verification Postfix uses for optional certificate verification
> verbosity is at:
> --
>     Viktor.
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