利用PHP编程防范XSS跨站脚本攻击_PHP

＜?php
$str = "A 'quote' is ＜b＞bold＜/b＞";

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str);

// Outputs: A 'quote' is <b>bold</b>
echo htmlentities($str, ENT_QUOTES);
?＞

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=@avascript:a&
　　　　_#X6Cert('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
　　$val = preg_replace('/(&#[x|X]0{0,8}'.dechex(ord($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);

　$found = true; // keep replacing as long as the previous round replaced something
　while ($found == true) {
　　$val_before = $val;
　　for ($i = 0; $i ＜ sizeof($ra); $i ) {
　　　$pattern = '//m.sbmmt.com/m/';
　　　for ($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[$i], 0, 2).'＜x＞'.substr($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;
　　}
　}
}
}