2013.03.10 23:39

PHP XSS (cross site scripting) filter function Web hacking

출처 : http://kallahar.com/smallprojects/php_xss_filter_function.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 <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-\x20])/''', $val); 
    
   // straight replacements, the user should never need these since they're normal characters 
   
// this prevents like <IMG SRC=&#X40&#X61&#X76&#X61&#X73&#X63&#X72&#X69&#X70&#X74&
   // #X3A&#X61&#X6C&#X65&#X72&#X74&#X28&#X27&#X58&#X53&#X53&#X27&#X29>
 
   $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 
    
   // &#x0040 @ search for the hex values 
      $val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($search[$i])).';?)/i', $search[$i], $val); 
      // with a ; 

      // &#00064 @ 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 .= '(&#[x|X]0{0,8}([9][a][b]);?)?'
               $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; 

Posted by k1rha