mikrotik captive portal - timeslot prolongation

mikrotik.js

/*
 * The mikrotik captive portal has a bug, causing login-durations of less than a given amount of time
 * to not be subtracted from the total time you are allowed to stay online.
 * The threshold at which time is actually counted seems to vary.
 * This script automagically logs you out and back in in a given interval, allowing you to keep surfing indefinitely
 */

const portalURL = `http://172.31.0.1/`;
const username = `MyUsername`;
const password = `MyPassword`;
const interval = 20 * 1000;

const fetch = require('node-fetch');
const eventuallyMD5js = fetch(portalURL + 'md5.js').then(r=>r.text());

async function update() {
  const logout = await fetch(portalURL + 'logout');
  const login = await fetch(portalURL + 'login').then(res=>res.text());
  const challengeRegex = /hexMD5\(\'(.*)\'\)/;
  const match = challengeRegex.exec(login)[0];
  const challenge = match.replace(`' + document.login.password.value + '`, password);
  const code = new Function(await eventuallyMD5js + '\nreturn ' + challenge);
  const response = code();
  const loggedin = await fetch(portalURL + 'login', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/x-www-form-urlencoded'
    },
    body: `username=${username}&`
      + `password=${response}&`
      + `dst=&`
      + `popup=true`
  }).then(res=>res.text());
  if (loggedin.includes('You are logged in')) {
    console.log('login successful');
  } else {
    console.error('an error occured', loggedin);
  }
}

async function logout() {
    console.log("Logging out...");
    await fetch(portalURL + 'logout').catch(()=>console.log('logout failed!'));
}

async function backoff(e) {
    console.error(e);
    setTimeout(()=>update().catch(backoff),10000);
}

setInterval(()=>update().catch(backoff), interval);
update();

process.on('SIGINT', async () => {
  await logout();
  process.exit();
});