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和记娱h188下载app:利用PHP编程防范XSS跨站脚本攻击



海内不少论坛都存在跨站脚本破绽,国外也很多这样的例子,以致Google也呈现过,不过在12月初时修正了。(编者注:关于跨站脚本破绽进击,读者可参阅《详解XSS跨站脚本进击》)。跨站进击很轻易就可以构造,而且异常隐蔽,不易被查觉(平日窃守信息后顿时跳转回原页面)。

若何进击,在此不作阐明(也不要问我),主要谈谈若何警备。首先,跨站脚本进击都是因为对用户的输入没有进行严格的过滤造成的,以是我们必须在所稀有据进入我们的网站和数据库之前把可能的危险拦截。针对不法的HTML代码包括单双引号等,可以应用htmlentities() 。

<?php

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

// Outputs: A 'quote' is <b>bold&l和记娱h188下载appt;/b>

echo htmlentities($str);

// Outputs: A 'quote' is <b>bold</b>

echo htmlentities($str, ENT_QUOTES);

?>

这样可以使不法的脚本掉效。

然则要留意一点,htmlentities()默认编码为 ISO-8859-1,假如你的不法脚本编码为其它,那么可能无法过滤掉落,同时浏览器却可以识别和履行。这个问题我先找几个站点测试后再说。

这里供给一个过滤不法脚本的函数:

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 <javascript>

// note that you have to handle splits with

,

, and    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';

$search .= '12345678和记娱h188下载app90!@#$%^&*()';

$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   ,

, and

$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', 'on和记娱h188下载appdragenter', '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'和记娱h188下载app, '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 somet和记娱h188下载apphing

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 .= '(&#[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;

}

}

}

}

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