Common php xss attack filtering function, which prevents XSS vulnerability attacks in the Discuz system.

Rule. Another

The goal of this function is to be a generic function that can be used to parse almost any input and render it XSS safe. for more information on actual XSS attacks, check out http://ha.ckers.org/xss.html. another

Removed XSS attack-related php Functions

The goal of this function is to be a generic function that can be used to parse almost any input and render it XSS safe. for more information on actual XSS attacks, check out http://ha.ckers.org/xss.html. another excellent site is the XSS Database which details each attack and how it works.

  * @package RemoveXSS */class RemoveXSS {/** * Wrapper for the RemoveXSS function. * Removes potential XSS code from an input string. * * Using an external class by Travis Puderbaugh 
 
   * * @paramstringInput string * @returnstringInput string with potential XSS code removed */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 
  
   // 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 $search = "'abcdefghijklmnopqrstuvwxyz';$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('/(&#[x|X]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 somethingwhile ($found == true) {$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]);?)?';$pattern .= '|({0,8}([9][10][13]);?)?';$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, $val); // filter out the hex tagsif ($val_before == $val) {// no replacements were made, so exit the loop$found = false;}}}return $val;}}?>
   
  
 

The Discuz system prevents XSS vulnerability attacks and filters PHP functions for HTML dangerous tag attributes.

// Shield htmlfunction checkhtml ($ html) {$ html = stripslashes ($ html); if (! Checkperm ('allowhtml ') {preg_match_all ("/<([^ <] +)>/is", $ html, $ ms ); $ searchs [] = '<'; $ replaces [] = '<'; $ searchs [] = '>'; $ replaces [] = '> '; if ($ ms [1]) {$ allowtags = 'img | a | font | p | table | tbody | caption | tr | td | th | br | p | B | strong | I | u | em | span | ol | ul | li | blockquote | object | param | embed '; // allowed tags $ ms [1] = array_unique ($ ms [1]); foreach ($ ms [1] as $ value) {$ searchs [] = "<". $ value. ">"; $ value = shtmlspecialchars ($ value ); $ Value = str_replace (array ('\', '/*'), array ('. ','/. '), $ value); $ skipkeys = array ('onabort', 'onactivate', 'onafterprint ', 'onafterupdate', 'onbeforeactivate', 'onbeforecopy', 'onbeforecut ', 'handler', 'onbeforeeditfocal ', 'onbeforepaste', 'onbeforeprint', 'onbeforeunload', 'onbeforeupdate', 'onblur', 'onbodychange', 'oncellchang', 'onchange ', 'onclick', 'ontextmenu ', 'oncontrolselect', 'oncopy', 'oncut', 'on Dataavailable ', 'ondatasetchanged', 'ondatasetcomplete', 'ondblclick', 'ondeactivate', 'ondrag', 'ondragend', 'ondragenter', 'ondragleave ', 'ondragover ', 'ondragstart', 'ondrop', 'onerror', 'onerrorupdat', 'onfilterchang', 'onfinish ', 'onfocus', 'onfocusin', 'onfocusout', 'onhelp ', 'onkeylow', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture ', 'onmouselow', 'onmouseenter', 'onmouseleave', 'onmousemove ', 'Onmouseout', 'onmouseover', 'onmouseup', 'onmousewheel', 'onmove ', 'onmoveend', 'onmovestart', 'onpaste', 'onpropertychang ', onreadystatechange, onreset, onresize, onresizeend, onresizestart, onrowenter, onrowexit, onrowsinserted, onscroll ', 'onselect', 'onselectionchang', 'onselectstart', 'onstart', 'onstop', 'onsubmit ', 'onunload', 'javascript', 'script', 'eval ', 'behaviour', 'Expression ', 'Style', 'class'); $ skipstr = implode (' | ', $ skipkeys); $ value = preg_replace (array ("/($ skipstr) /I "),'. ', $ value); if (! Preg_match ("/^ [/| s]? ($ Allowtags) (s + | $)/is ", $ value) {$ value ='';} $ replaces [] = empty ($ value )? '':" <". Str_replace ('"', '"', $ value ). ">" ;}}$ html = str_replace ($ searchs, $ replaces, $ html) ;}$ html = addslashes ($ html); return $ html ;}

Original article address: PHP's common XSS attack filtering function, which prevents XSS vulnerability attacks in the Discuz system and filters the HTML dangerous tag attribute P. Thanks to the original author for sharing.