SSL_get_peer_signature_type_nid
else if (SSL_get_peer_signature_type_nid(s, &nid))
int SSL_get_peer_signature_type_nid(const SSL *s, int *pnid);
SSL_get_peer_signature_type_nid(client.ssl, &ret->server_sign_type);
SSL_get_peer_signature_type_nid(server.ssl, &ret->client_sign_type);