OpenSSL::X509::CRL#signature_algorithm

static VALUE
ossl_x509crl_get_signature_algorithm(VALUE self)
{
    X509_CRL *crl;
    const X509_ALGOR *alg;
    BIO *out;

    GetX509CRL(self, crl);
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eX509CRLError, NULL);
    }
    X509_CRL_get0_signature(crl, NULL, &alg);
    if (!i2a_ASN1_OBJECT(out, alg->algorithm)) {
        BIO_free(out);
        ossl_raise(eX509CRLError, NULL);
    }

    return ossl_membio2str(out);
}