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php过滤XSS攻击的函数

发布时间:2022-07-30 09:10:48 所属栏目:PHP教程 来源:互联网
导读:PHP站点如何防御XSS攻击呢?看下面的过滤XSS攻击的PHP函数吧,很实用,下面的函数可以用来过滤用户的输入,保证输入是XSS安全的。具体如何过滤,可以参看函数内部,也有注释。 ?php function RemoveXSS($val) { // remove all non-printable characters. CR(
  PHP站点如何防御XSS攻击呢?看下面的过滤XSS攻击的PHP函数吧,很实用,下面的函数可以用来过滤用户的输入,保证输入是XSS安全的。具体如何过滤,可以参看函数内部,也有注释。
 
  <?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 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];  
           } //phpfensi.com
           $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;   
  }    
  ?> 

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