OpenSSL::PKey::RSA#export

static VALUE
ossl_rsa_export(int argc, VALUE *argv, VALUE self)
{
    RSA *rsa;
    const BIGNUM *n, *e, *d, *p, *q, *dmp1, *dmq1, *iqmp;
    BIO *out;
    const EVP_CIPHER *ciph = NULL;
    VALUE cipher, pass, str;

    GetRSA(self, rsa);

    rb_scan_args(argc, argv, "02", &cipher, &pass);

    if (!NIL_P(cipher)) {
        ciph = ossl_evp_get_cipherbyname(cipher);
        pass = ossl_pem_passwd_value(pass);
    }
    if (!(out = BIO_new(BIO_s_mem()))) {
        ossl_raise(eRSAError, NULL);
    }
    RSA_get0_key(rsa, &n, &e, &d);
    RSA_get0_factors(rsa, &p, &q);
    RSA_get0_crt_params(rsa, &dmp1, &dmq1, &iqmp);
    if (n && e && d && p && q && dmp1 && dmq1 && iqmp) {
        if (!PEM_write_bio_RSAPrivateKey(out, rsa, ciph, NULL, 0,
                                         ossl_pem_passwd_cb, (void *)pass)) {
            BIO_free(out);
            ossl_raise(eRSAError, NULL);
        }
    } else {
        if (!PEM_write_bio_RSA_PUBKEY(out, rsa)) {
            BIO_free(out);
            ossl_raise(eRSAError, NULL);
        }
    }
    str = ossl_membio2str(out);

    return str;
}