static VALUE 
ossl_x509extfactory_create_ext(int argc, VALUE *argv, VALUE self)
{
    X509V3_CTX *ctx;
    X509_EXTENSION *ext;
    VALUE oid, value, critical, valstr, obj;
    int nid;
#ifdef HAVE_X509V3_EXT_NCONF_NID
    VALUE rconf;
    CONF *conf;
#else
    static LHASH *empty_lhash;
#endif

    rb_scan_args(argc, argv, "21", &oid, &value, &critical);
    StringValue(oid);
    StringValue(value);
    if(NIL_P(critical)) critical = Qfalse;

    nid = OBJ_ln2nid(RSTRING_PTR(oid));
    if(!nid) nid = OBJ_sn2nid(RSTRING_PTR(oid));
    if(!nid) ossl_raise(eX509ExtError, "unknown OID `%s'", RSTRING_PTR(oid));
    valstr = rb_str_new2(RTEST(critical) ? "critical," : "");
    rb_str_append(valstr, value);
    GetX509ExtFactory(self, ctx);
#ifdef HAVE_X509V3_EXT_NCONF_NID
    rconf = rb_iv_get(self, "@config");
    conf = NIL_P(rconf) ? NULL : GetConfigPtr(rconf);
    ext = X509V3_EXT_nconf_nid(conf, ctx, nid, RSTRING_PTR(valstr));
#else
    if (!empty_lhash) empty_lhash = lh_new(NULL, NULL);
    ext = X509V3_EXT_conf_nid(empty_lhash, ctx, nid, RSTRING_PTR(valstr));
#endif
    if (!ext){
        ossl_raise(eX509ExtError, "%s = %s",
                   RSTRING_PTR(oid), RSTRING_PTR(value));
    }
    WrapX509Ext(cX509Ext, obj, ext);

    return obj;
}