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.
![Being a Dev Dad]()
I get asked loads of questions every day but I'm always surprised that they're rarely questions about code or even tech -- many of the questions I get are more about non-dev stuff like what my office is like, what software I use, and oftentimes...
![Create a CSS Cube]()
CSS cubes really showcase what CSS has become over the years, evolving from simple color and dimension directives to a language capable of creating deep, creative visuals. Add animation and you've got something really neat. Unfortunately each CSS cube tutorial I've read is a bit...
![MooTools Text Flipping]()
There are lots and lots of useless but fun JavaScript techniques out there. This is another one of them.
One popular April Fools joke I quickly got tired of was websites transforming their text upside down. I found a jQuery Plugin by Paul...
![9 Incredible CodePen Demos]()
CodePen is a treasure trove of incredible demos harnessing the power of client side languages. The client side is always limited by what browsers provide us but the creativity and cleverness of developers always pushes the boundaries of what we think the front end can do. Thanks to CSS...
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!