XSS攻击在最近很是流行，往往在某段代码里一不小心就会被人放上XSS攻击的代码，看到国外有人写上了函数，咱也偷偷懒，悄悄的贴上来。。。
原文如下：

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.

<?php

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 <javascript>

   // note that you have to handle splits with

,

, and 	 later since they *are* allowed in some inputs

   $val = preg_replace('/([x00-x08,x0b-x0c,x0e-x19])/', '', $val);  

   // straight replacements, the user should never need these since they're normal characters

   // this prevents like <IMG SRC=@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

	  $val = preg_replace('/(&#[xX]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); // with a ;

	  // @ @ 0{0,7} matches '0' zero to seven times

	  $val = preg_replace('/(&#0{0,8}'.ord($search[$i]).';?)/', $search[$i], $val); // with a ;

   } 

   // now the only remaining whitespace attacks are 	,

, and 

   $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');

   $ra = array_merge($ra1, $ra2); 

   $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 .= '(&#[xX]0{0,8}([9ab]);)';

			   $pattern .= '|';

			   $pattern .= '|(&#0{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;

}

?>

经过这样的过滤后，应该被攻击的机会会少上很多吧？试试看呢？

---

Discuz系统中 防止XSS漏洞攻击，过滤HTML危险标签属性的PHP函数

function string_remove_xss($html) {

	preg_match_all("/\<([^\<]+)\>/is", $html, $ms);

	$searchs[] = '<';

	$replaces[] = '&lt;';

	$searchs[] = '>';

	$replaces[] = '&gt;';

	if ($ms[1]) {

		$allowtags = 'img|a|font|div|table|tbody|caption|tr|td|th|br|p|b|strong|i|u|em|span|ol|ul|li|blockquote';

		$ms[1] = array_unique($ms[1]);

		foreach ($ms[1] as $value) {

			$searchs[] = "&lt;".$value."&gt;";

			$value = str_replace('&amp;', '_uch_tmp_str_', $value);

			$value = string_htmlspecialchars($value);

			$value = str_replace('_uch_tmp_str_', '&amp;', $value);

			$value = str_replace(array('\\', '/*'), array('.', '/.'), $value);

			$skipkeys = 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','javascript','script','eval','behaviour','expression','style','class');

			$skipstr = implode('|', $skipkeys);

			$value = preg_replace(array("/($skipstr)/i"), '.', $value);

			if (!preg_match("/^[\/|\s]?($allowtags)(\s+|$)/is", $value)) {

				$value = '';

			}

			$replaces[] = empty($value) ? '' : "<" . str_replace('&quot;', '"', $value) . ">";

		}

	}

	$html = str_replace($searchs, $replaces, $html);

	return $html;

}

function string_htmlspecialchars($string, $flags = null) {

	if (is_array($string)) {

		foreach ($string as $key => $val) {

			$string[$key] = string_htmlspecialchars($val, $flags);

		}

	} else {

		if ($flags === null) {

			$string = str_replace(array('&', '"', '<', '>'), array('&amp;', '&quot;', '&lt;', '&gt;'), $string);

			if (strpos($string, '&amp;#') !== false) {

				$string = preg_replace('/&amp;((#(\d{3,5}|x[a-fA-F0-9]{4}));)/', '&\\1', $string);

			}

		} else {

			if (PHP_VERSION < '5.4.0') {

				$string = htmlspecialchars($string, $flags);

			} else {

				if (!defined('CHARSET') || (strtolower(CHARSET) == 'utf-8')) {

					$charset = 'UTF-8';

				} else {

					$charset = 'ISO-8859-1';

				}

				$string = htmlspecialchars($string, $flags, $charset);

			}

		}

	}

	return $string;

}