verify

static VALUE
ossl_ocspbres_verify(int argc, VALUE *argv, VALUE self)
{
    VALUE certs, store, flags;
    OCSP_BASICRESP *bs;
    STACK_OF(X509) *x509s;
    X509_STORE *x509st;
    int flg, result;

    rb_scan_args(argc, argv, "21", &certs, &store, &flags);
    GetOCSPBasicRes(self, bs);
    x509st = GetX509StorePtr(store);
    flg = NIL_P(flags) ? 0 : NUM2INT(flags);
    x509s = ossl_x509_ary2sk(certs);
#if (OPENSSL_VERSION_NUMBER < 0x1000202fL) || defined(LIBRESSL_VERSION_NUMBER)
    /*
     * OpenSSL had a bug that it doesn't use the certificates in x509s for
     * verifying the chain. This can be a problem when the response is signed by
     * a certificate issued by an intermediate CA.
     *
     *       root_ca
     *         |
     *   intermediate_ca
     *         |-------------|
     *     end_entity    ocsp_signer
     *
     * When the certificate hierarchy is like this, and the response contains
     * only ocsp_signer certificate, the following code wrongly fails.
     *
     *   store = OpenSSL::X509::Store.new; store.add_cert(root_ca)
     *   basic_response.verify([intermediate_ca], store)
     *
     * So add the certificates in x509s to the embedded certificates list first.
     *
     * This is fixed in OpenSSL 0.9.8zg, 1.0.0s, 1.0.1n, 1.0.2b. But it still
     * exists in LibreSSL 2.1.10, 2.2.9, 2.3.6, 2.4.1.
     */
    if (!(flg & (OCSP_NOCHAIN | OCSP_NOVERIFY)) &&
        sk_X509_num(x509s) && sk_X509_num(bs->certs)) {
        int i;

        bs = ASN1_item_dup(ASN1_ITEM_rptr(OCSP_BASICRESP), bs);
        if (!bs) {
            sk_X509_pop_free(x509s, X509_free);
            ossl_raise(eOCSPError, "ASN1_item_dup");
        }

        for (i = 0; i < sk_X509_num(x509s); i++) {
            if (!OCSP_basic_add1_cert(bs, sk_X509_value(x509s, i))) {
                sk_X509_pop_free(x509s, X509_free);
                OCSP_BASICRESP_free(bs);
                ossl_raise(eOCSPError, "OCSP_basic_add1_cert");
            }
        }
        result = OCSP_basic_verify(bs, x509s, x509st, flg);
        OCSP_BASICRESP_free(bs);
    }
    else {
        result = OCSP_basic_verify(bs, x509s, x509st, flg);
    }
#else
    result = OCSP_basic_verify(bs, x509s, x509st, flg);
#endif
    sk_X509_pop_free(x509s, X509_free);
    if (result <= 0)
        ossl_clear_error();

    return result > 0 ? Qtrue : Qfalse;
}