Php implements XSS security Filtering. phpxss filtration _ PHP Tutorial

Php implements XSS security filtering and phpxss filtering. Php implements XSS security Filtering. phpxss provides an example of how php implements XSS security filtering. Share it with you for your reference. The details are as follows: functionremove_xss ($ val) php implements XSS security filtering and phpxss filtering

This example describes how to implement XSS security filtering in php. Share it with you for your reference. The details are as follows:

function remove_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 
 
    // 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;}
  
 

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Examples in this article describes how php implements XSS security filtering. Share it with you for your reference. Details: function remove_xss ($ val )...