sshpkt_get_bignum2
if ((r = sshpkt_get_bignum2(ssh, &p)) != 0 ||
(r = sshpkt_get_bignum2(ssh, &g)) != 0 ||
if ((r = sshpkt_get_bignum2(ssh, &dh_server_pub)) != 0 ||
if ((r = sshpkt_get_bignum2(ssh, &dh_client_pub)) != 0 ||
int sshpkt_get_bignum2(struct ssh *ssh, BIGNUM **valp);