Whitelisting: You Set The Rules For Security

By  on  

We all know what blacklisting is when it comes to strings: removing specified "bad" characters. While this helps to secure user input, it isn't as secure as whitelisting. Whitelisting is the process of saying "Let me tell you what you can give me" whereas blacklisting says "If I find this, I'll remove it."

A customer recently asked that I create a whitelisting function that allowed letters, digits, whitespace characters, periods, commas, and dashes. Any other characters were to be replaced with spaces.

The PHP

function make_valid($input) 
{ 
	return preg_replace('/[^A-Za-z0-9.,\(\)\s-]/',' ',$input); 
}

The above function uses preg_match() and a small regular expression to remove the rubbish characters.

Recent Features

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

  • By
    Interview with a Pornhub Web Developer

    Regardless of your stance on pornography, it would be impossible to deny the massive impact the adult website industry has had on pushing the web forward. From pushing the browser's video limits to pushing ads through WebSocket so ad blockers don't detect them, you have...

Incredible Demos

  • By
    MooTools Overlay Plugin

    Overlays have become a big part of modern websites; we can probably attribute that to the numerous lightboxes that use them. I've found a ton of overlay code snippets out there but none of them satisfy my taste in code. Many of them are...

  • By
    Assign Anchor IDs Using MooTools 1.2

    One of my favorite uses of the MooTools JavaScript library is the SmoothScroll plugin. I use it on my website, my employer's website, and on many customer websites. The best part about the plugin is that it's so easy to implement. I recently ran...

Discussion

  1. Your way for whitelisting is quite nice. It’s like in Flash where you can specify exactly what characters are allowed by the user.
    This method may work well as a common security filter that replaces get_magic_quotes_gpc(), strip_tags() and htmlentities().
    Good work as usual!

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!