Php xss filtering and xss Filtering
XSS, also known as CSS (Cross Site Script), is a Cross-Site scripting attack. A malicious attacker inserts malicious html code into a Web page. When a user browses this page, the html code embedded in the Web page is executed, in this way, some people are attacked.
For example, add? Id = 19 "> <div + style % 3 Dwidth % 3 Aexpression (alert (42873)>
This can cause page disorder and even a pop-up box!
Below is a piece of code in thinkphp, used to filter xss
ThinkPHP \ Code \ ThinkPHP \ Common \ extend. php
<? 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 \ 0 script>
// 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 shoshould never need these since they're normal characters
// This prevents like
$ Search = 'abcdefghijklmnopqrstuvwxy ';
$ Search. = 'abcdefghijklmnopqrstuvwxy ';
$ Search. = '2017! @ # $ % ^ &*()';
$ 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;
// @ 0 {0, 7} matches '0' zero to seven times
$ Val = preg_replace ('/(& #0 {0, 8}'. ord ($ search [$ I]). ';?) /', $ Search [$ I], $ val); // with;
}
// 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', 'frameset', 'ilayer', 'lay', 'bgsound ', 'title', 'base ');
$ Ra2 = Array ('onabport', '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', 'onerrorupdat', 'onfilterchang', 'onfinish ', 'oncore', 'onfocusin', 'onfocusout ', 'onhelp', 'onkeylow', 'onkeypress', 'onkeyup', 'onlayoutcomplete', 'onload', 'onlosecapture ', onmousedown, onmouseenter, onmouseleave, onmousemove, onmouseout, onmouseover, onmouseup, onmousewheel, onmove, onmoveend ', 'onmovestart', 'onpaste ', 'onpropertychang', 'onreadystatechang', 'onreset', 'onresizeend', 'onresizestart', 'onrowenter', 'onrowexit ', 'onrowsdelete', 'onrowsinserted', 'onscroll ', 'onselect', 'onselectionchang', 'onselectstart', 'onstart', 'onstop', 'onsubmit ', 'onload ');
$ 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 ';
$ 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;
}
?>
Test:
<?php //echo RemoveXSS("<script language='javascript'>alert('hello world');</script>") ; ?>
In addition, there is another tool: HTML Purifier, which is twice the efficiency of the preceding document. It wants to know what to do later and listen to the next decomposition.
