private function checkConfigOptions($config)
    {
        if (!isset($config['cas_host'])) {
            throw new Exception("CAS host required!", 500);
        }
        if (!isset($config['cas_port'])) {
            throw new Exception("CAS port required!", 500);
        }
        if (!isset($config['cas_context'])) {
            throw new Exception("CAS path required!", 500);
        }
        if (!isset($config['ca_cert_path'])) {
            throw new Exception("CA cert path for CAS server required!", 500);
        }
    }