Whitelisting: You Set The Rules For Security
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.
![9 Mind-Blowing Canvas Demos]()
The <canvas> element has been a revelation for the visual experts among our ranks. Canvas provides the means for incredible and efficient animations with the added bonus of no Flash; these developers can flash their awesome JavaScript skills instead. Here are nine unbelievable canvas demos that...
![CSS Gradients]()
With CSS border-radius, I showed you how CSS can bridge the gap between design and development by adding rounded corners to elements. CSS gradients are another step in that direction. Now that CSS gradients are supported in Internet Explorer 8+, Firefox, Safari, and Chrome...
![HTML5 Datalist]()
One of the most used JavaScript widgets over the past decade has been the text box autocomplete widget. Every JavaScript framework has their own autocomplete widget and many of them have become quite advanced. Much like the placeholder attribute's introduction to markup, a frequently used...
![Create Twitter-Style Dropdowns Using MooTools]()
Twitter does some great stuff with JavaScript. What I really appreciate about what they do is that there aren't any epic JS functionalities -- they're all simple touches. One of those simple touches is the "Login" dropdown on their homepage. I've taken...
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!