OpenSSL::X509::Request#signature_algorithm

static VALUE
ossl_x509req_get_signature_algorithm(VALUE self)
{
    X509_REQ *req;
    const X509_ALGOR *alg;
    BIO *out;

    GetX509Req(self, req);

    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eX509ReqError, NULL);
    }
    X509_REQ_get0_signature(req, NULL, &alg);
    if (!i2a_ASN1_OBJECT(out, alg->algorithm)) {
        BIO_free(out);
        ossl_raise(eX509ReqError, NULL);
    }

    return ossl_membio2str(out);
}