XSS防御函数分享

XSS跨站脚本攻击危害越来越严重，在盲打满天飞的时代，我们如何防御XSS跨站脚本攻击呢？

根据我们的经验是，一切输入都是不可信的，那么我们需要对用户的输入进行过滤，然后再对向网页的输出进行编码。

各脚本程序都有其独有的过滤函数，比如php就有htmlspecialchars，strip_tags等，但是对用户的输入数据，我们要过滤的就太多了，不过还好网上有大牛帮我们写好了过滤函数，小弟拿过来分享给大家。

使用方法

请将以下代码加入到你的核心函数库里面，然后在使用的时候直接调用即可。

  
       // 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   
       $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[$i], 0, 2).''.substr($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;  
    }   
?>

from www.waitalone.cn.thanks for it.