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.
![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...
![Create a CSS Flipping Animation]()
CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...
![MooTools Typewriter Effect Plugin Upgrade]()
Last week I shared my MooTools Typewriter Class with you. It was pretty well received and I got a few feature requests that I've implemented including "backspacing" and character variance delays. I'm not going to explain the old code, so click here...
![CSS Scoped Styles]()
There are plenty of awesome new attributes we've gotten during the HTML5 revolution: placeholder, download, hidden, and more. Each of these attributes provides us a different level of control over an element on the page, but there's a new element attribute that allows...
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!