<?php
/**
* Usage: Run *every* variable passed in through it.
* The goal of this function is to be a generic function that can be used to
* parse almost any input and render it XSS safe. For more information on
* actual XSS attacks, check out http://ha.ckers.org/xss.html. Another
* excellent site is the XSS Database which details each attack and how it
* works.
*
* Used with permission by the author.
* URL: http://quickwired.com/smallprojects/php_xss_filter_function.php
*
* License:
* This code is public domain, you are free to do whatever you want with it,
* including adding it to your own project which can be under any license.
*
* $Id: RemoveXSS.php 2663 2007-11-05 09:22:23Z ingmars $
*
* @author Travis Puderbaugh <kallahar@quickwired.com>
* @package RemoveXSS
*/
class RemoveXSS {
/**
* Wrapper for the RemoveXSS function.
* Removes potential XSS code from an input string.
*
* Using an external class by Travis Puderbaugh <kallahar@quickwired.com>
*
* @param string Input string
* @return string Input string with potential XSS code removed
*/
function RemoveXSS($val) {
// remove all non-printable characters. CR(0a) and LF(0b) and TAB(9) are allowed
// this prevents some character re-spacing such as <java\0script>
// note that you have to handle splits with \n, \r, and \t later since they *are* allowed in some inputs
$val = preg_replace('/([\x00-\x08][\x0b-\x0c][\x0e-\x20])/', '', $val); // straight replacements, the user should never need these since they're normal characters
// this prevents like <IMG src="http://www.iamle.com/archives/@avascript:alert('XSS')>
$search = "'abcdefghijklmnopqrstuvwxyz';
$search.= 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
$search.= '1234567890!@#$%^&*()';
$search.= '~`";:?+/={}[]-_|\'\\';
for ($i = 0; $i < strlen($search); $i++) { // ;? matches the ;, which is optional
// 0{0,7} matches any padded zeros, which are optional and go up to 8 chars
// @ @ search for the hex values
// @ @ 0{0,7} matches '0' zero to seven times
$val = preg_replace('/(�{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ; }
// now the only remaining whitespace attacks are \t, \n, and \r
$ra1 = array('javascript', 'vbscript', 'expression', 'applet', 'meta', 'xml', 'blink', 'link', 'style', 'script', 'embed', 'object', 'iframe', 'frame', 'frameset', 'ilayer', 'layer', 'bgsound', 'title', 'base'); $ra2 = array('onabort', 'onactivate', 'onafterprint', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut', 'onbeforedeactivate', 'onbeforeeditfocus', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbounce', 'oncellchange', 'onchange', 'onclick', 'oncontextmenu', 'oncontrolselect', 'oncopy', 'oncut', 'ondataavailable', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave', 'ondragover', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdate', 'onfilterchange', 'onfinish', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp', 'onkeydown', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture', 'onmousedown', 'onmouseenter', 'onmouseleave', 'onmousemove', 'onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychange', 'onreadystatechange', 'onreset', 'onresize', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit', 'onrowsdelete', 'onrowsinserted', 'onscroll', 'onselect', 'onselectionchange', 'onselectstart', 'onstart', 'onstop', 'onsubmit', 'onunload'); $found = true; // keep replacing as long as the previous round replaced something
while ($found == true) {
$val_before = $val;
for ($i = 0; $i < sizeof($ra); $i++) { $pattern = '/';
for ($j = 0; $j < strlen($ra[$i]); $j++) { if ($j > 0) {
$pattern .= '(';
$pattern .= '(&#[x|X]0{0,8}([9][a][b]);?)?';
$pattern .= '|(�{0,8}([9][10][13]);?)?';
$pattern .= ')?';
}
$pattern .= $ra[$i][$j];
}
$pattern .= '/i';
$replacement = substr($ra[$i], 0, 2).'<x>'.substr($ra[$i], 2); // add in <> to nerf the tag $val = preg_replace($pattern, $replacement, $val); // filter out the hex tags if ($val_before == $val) {
// no replacements were made, so exit the loop
$found = false;
}
}
}
return $val;
}
}
?>