openssl 验证证书是否是某个CA证书签发

int VerifyCertByIssuer(X509 *cert, X509 *issuer)
{
int res = 0;
EVP_PKEY *pubkey = 0;
if (X509_check_issued(issuer, cert) != X509_V_OK)
{
goto end;
}
pubkey = X509_get_pubkey(issuer);
if (!X509_verify(cert, pubkey))
{
goto end;
}
res = 1;
end:
if (pubkey)
{
EVP_PKEY_free(pubkey);
}
return res;
}