get_preauth_time
krb5_error_code (*get_preauth_time)(krb5_context context,
get_preauth_time,
retval = cb->get_preauth_time(context, rock, FALSE, &ts.patimestamp,
ret = cb->get_preauth_time(context, rock, TRUE, &pa_enc.patimestamp,
retval = cb->get_preauth_time(context, rock, TRUE, &ctsec, &cusec);