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php防止xss攻击的方法

来源: 作者: 时间:2013-08-30 点击:

XSS又叫CSS (Cross Site Script) ,跨站脚本攻击。它指的是恶意攻击者往Web页面里插入恶意html代码,当用户浏览该页之时,嵌入其中Web里面的html代码会被执行,进而达到某些人的攻击目的。

下面是thinkphp里面的一段代码,用于过滤xss!

 
  1. <?php    
  2.     /** 
  3.     * @去除XSS(跨站脚本攻击)的函数 
  4.     * @par $val 字符串参数,可能包含恶意的脚本代码如<script language="javascript">alert("hello world");</script> 
  5.     * @return  处理后的字符串 
  6.     * @Recoded By Androidyue 
  7.     **/  
        function clean_xss($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 n, r, and t later since they *are* allowed in some inputs
           $val = html_entity_decode(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 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{0,8}([9|10|13]);)';
                       $pattern .= ')*';
                    }
                    $pattern .= $ra[$i][$j];
                 }
                 $pattern .= '[^><]*>/i';
                 $val = preg_replace($pattern, '', $val); // filter out the hex tags
                 if ($val_before == $val) {
                    // no replacements were made, so exit the loop
                    $found = false;
                 }
              }
           }
           return $val;
        }
  8.    //测试一下效果  
  9.    //echo clean_xss("<script language='javascript'>alert('hello world');</script>") ;  
  10. ?>  
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