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
    How to Create a RetroPie on Raspberry Pi – Graphical Guide

    Today we get to play amazing games on our super powered game consoles, PCs, VR headsets, and even mobile devices.  While I enjoy playing new games these days, I do long for the retro gaming systems I had when I was a kid: the original Nintendo...

  • By
    Send Text Messages with PHP

    Kids these days, I tell ya.  All they care about is the technology.  The video games.  The bottled water.  Oh, and the texting, always the texting.  Back in my day, all we had was...OK, I had all of these things too.  But I still don't get...

Incredible Demos

  • By
    Fancy FAQs with jQuery Sliders

    Frequently asked questions can be super boring, right? They don't have to be! I've already shown you how to create fancy FAQs with MooTools -- here's how to create the same effect using jQuery. The HTML Simply a series of H3s and DIVs wrapper...

  • By
    iPhone Checkboxes Using MooTools

    One of the sweet user interface enhancements provided by Apple's iPhone is their checkbox-slider functionality. Thomas Reynolds recently released a jQuery plugin that allows you to make your checkboxes look like iPhone sliders. Here's how to implement that functionality using the beloved...

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!