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
    Responsive and Infinitely Scalable JS Animations

    Back in late 2012 it was not easy to find open source projects using requestAnimationFrame() - this is the hook that allows Javascript code to synchronize with a web browser's native paint loop. Animations using this method can run at 60 fps and deliver fantastic...

  • By
    Write Better JavaScript with Promises

    You've probably heard the talk around the water cooler about how promises are the future. All of the cool kids are using them, but you don't see what makes them so special. Can't you just use a callback? What's the big deal? In this article, we'll...

Incredible Demos

  • By
    DWRequest: MooTools 1.2 AJAX Listener & Message Display

    Though MooTools 1.2 is in its second beta stage, its basic syntax and theory changes have been hashed out. The JavaScript library continues to improve and become more flexible. Fellow DZone Zone Leader Boyan Kostadinov wrote a very useful article detailing how you can add a...

  • By
    jQuery Random Link Color Animations

    We all know that we can set a link's :hover color, but what if we want to add a bit more dynamism and flair? jQuery allows you to not only animate to a specified color, but also allows you to animate to a random color. The...

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!