Rate limiting to prevent malicious behavior in Exp

Question

Someone made me aware of some flaws in an application I'm working on (mostly within my JavaScript on the front-end), that leaves open the possibility of, say, clicking a ton of buttons at once and sending out a ton of transactional emails. This is clearly not good.

I think one way to handle this in ExpressJS is by using app.all() to count the number of requests that happen within a certain timeframe. I'd store this in the session metadata with timestamps, and if more than X requests happen in Y time, I cut them off for awhile until the limit expires.

Has anyone done this before or have any tips/hints to help me out? Something that's easy to drop in and out of my app is preferable. Thanks!

Answer 1

You could use the Collate object in your webpage.

function Collate(timeout) {
  this.timeout = timeout || 1000;
}
Collate.prototype = {
  time: 0,

  idle: function() {
    var t = new Date().getTime();
    return (t - this.time > this.timeout && (this.time = t));
  },

  prefer: function(func) {
    this.func = func;
    clearTimeout(this.timer);
    this.timer = setTimeout(func, this.timeout);
  }
};

If you want a function to run once and not run again within the next 1 second. Like if you want to prevent the user from submitting a form many times, you do this:

var timer = new Collate(3000);  //3 seconds
button1.onclick = function() {
    if(timer.idle()) {
        button1.form.submit();
    } else alert("Don't click too quickly!");
}

//or on the form tag

<script>var submitTimer = new Collate(3000);</script>
<form action="post" onsubmit="return submitTimer.idle();">

If you expect an event to fire multiple times and only want to react to the last time it fires. Like if you want to search after a user has finished typing, you do this:

var timer = new Collate(700); //0.7 seconds
textfield1.onkeyup = function() {
    timer.prefer(function() {
        autocomplete.search(textfield1.value);
    });
};