OpenSSL::X509::Certificate#sign

static VALUE
ossl_x509_sign(VALUE self, VALUE key, VALUE digest)
{
    X509 *x509;
    EVP_PKEY *pkey;
    const EVP_MD *md;

    pkey = GetPrivPKeyPtr(key); /* NO NEED TO DUP */
    md = ossl_evp_get_digestbyname(digest);
    GetX509(self, x509);
    if (!X509_sign(x509, pkey, md)) {
        ossl_raise(eX509CertError, NULL);
    }

    return self;
}