app.use((req, res, next) => {
  const auth = { login: 'username', password: 'password' };
  const b64auth = (req.headers.authorization || '').split(' ')[1] || '';
  const [login, password] = new Buffer(b64auth, 'base64').toString().split(':');

  if (login && password && login === auth.login && password === auth.password) {
    return next();
  }

  res.set('WWW-Authenticate', 'Basic realm="401"');
  res.status(401).send('Authentication required.');
});