PHP過濾XSS攻擊的函數

XSS又叫CSS (Cross Site Script) ，跨站指令碼攻擊。它指的是惡意攻擊者往Web頁面裡插入惡意html代碼，當使用者瀏覽該頁之時，嵌入其中Web裡面的html代碼會被執行，進而達到某些人的攻擊目的。

<?php  /*** @去除XSS（跨站指令碼攻擊）的函數* @par $val 字串參數，可能包含惡意的指令碼代碼如<script language="javascript">alert("hello world");</script>* @return  處理後的字串* @Recoded By Androidyue**/function RemoveXSS($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-\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        $val = preg_replace('/(�{0,8}'.ord($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');    $ra = array_merge($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 .= '|(�{0,8}([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;  }//測試一下效果//echo RemoveXSS("<script language='javascript'>alert('hello world');</script>") ;?>