X509_get0_signature
X509_get0_signature(&signature, NULL, x);
X509_get0_signature(&sig, &sig_alg, x);
void X509_get0_signature(const ASN1_BIT_STRING **psig,
X509_get0_signature(NULL, &alg, eecert);
X509_get0_signature(&sig, &alg, x509);