php实现XSS安全过滤的方法

2024-05-04 23:38:17

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这篇文章主要介绍了php实现XSS安全过滤的方法,实例分析了php针对XSS进行安全过滤的相关技巧,具有一定参考借鉴价值,需要的朋友可以参考下

本文实例讲述了php实现XSS安全过滤的方法。分享给大家供大家参考。具体如下：

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 <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-/x19])/', '', $val);

// straight replacements, the user should never need these since they're normal characters

// this prevents like <IMG SRC=@avascript:alert('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

$val = preg_replace('/(&#[xX]0{0,8}'.dechex(ord($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[$i], 0, 2).'<x>'.substr($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;

}