php过滤非法脚本 允许正常的html标签

过滤有害的js代码,而放行正常的html标签。在网上搜了半天,没发现什么好办法。网上只要有富文本编辑器的地方,普遍存在xss问题。

网上有个remove_xss函数。相对好用。但经过实测,IE下还是有漏洞的。而且,会过滤style、iframe这些我们需要的标签和属性。

网上的remove_xss函数

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';
   $search .= '1234567890!@#$%^&#038;*()';
   $search .= '~`";:?+/={}[]-_|\'\\';
   for ($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
      $val = preg_replace('/(&#0{0,8}'.ord($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{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;
}

测试代码

$test='<p>测试测试<span style="color: #ff6600">带颜色字<span style="font-size: small">小字体</span></span><span style="font-size: small">字是小字体</span></p>
<p>测试<span style="background-color: #99cc00">背景色</span>测试</p>
<p>正常的字符:“javascript:”</p>
<img src="javas	cript:alert(/xss2/)" width=100>
<iframe src="http://www.baidu.com" width="600px" height="330px" style="margin: -33px 0 0 -23px; display=inline;" frameborder="0" marginheight="0" marginwidth="0" scrolling="no"></iframe>
';
echo remove_xss($test);

测试结果

看到了吧,不仅弹出了对话框,还把正常的html样式标签给过滤了!
其过滤之后的代码是这样的:

<p>测试测试<span st<x>yle="color: #ff6600">带颜色字<span st<x>yle="font-size: small">小字体</span></span><span st<x>yle="font-size: small">字是小字体</span></p>
<p>测试<span st<x>yle="background-color: #99cc00">背景色</span>测试</p>
<p>正常的字符:“ja<x>vasc<x>ript:</p>
<img src="javas	cript:alert(/xss2/)" width=100>
<if<x>rame src="http://www.baidu.com" width="600px" height="330px" st<x>yle="margin: -33px 0 0 -23px; display=inline;" fr<x>ameborder="0" marginheight="0" marginwidth="0" scrolling="no"></if<x>rame>

为什么弹出了呢?因为javascript中间的不是空格,而是[tab] !

<img src="javas[tab键]cript:alert(/xss2/)" width=100>

下面我们对函数进行一些修改,把style、iframe等标签统统放行,确保html样式能够正常显示,同时过滤掉[tab]。然后继续测试,这次测试更多xss的情况:

$test='<p>测试测试<span style="color: #ff6600">带颜色字<span style="font-size: small">小字体</span></span><span style="font-size: small">字是小字体</span></p>
<p>测试<span style="background-color: #99cc00">背景色</span>测试</p>
<p>正常的字符:“javascript:”</p>
<img src="javascrip&#116&#58alert(/xss1/)" width=100>
<img src="javas	cript:alert(/xss2/)" width=100>
<img src="#" onerror=alert(/xss3/)>
<img src="#" style="Xss:expression(alert(/xss4/))">
<img src="#"/**/onerror=alert(/xss5/) width=100>
<img src="#" onerror=alert(/xss6/)>
<img src="#" style="Xss:expression(alert(/xss7/));">
<img src="#"/**/onerror=alert(/xss8/) width=100>
<img src="#" style="Xss:ex/**/pression(alert(/xss9/));">
<iframe src="http://www.baidu.com" width="600px" height="330px" style="margin: -33px 0 0 -23px; display=inline;" frameborder="0" marginheight="0" marginwidth="0" scrolling="no"></iframe>
';
echo no_xss($test);

测试结果:

xss

这次html标签是放行了,但又产生了新问题,这样的代码又可以执行了!

<img src="#" style="Xss:ex/**/pression(alert(/xss9/));">

这个怎么过滤?我也不知道。只能用笨方法,把所有情况替换掉。
完整的跨站脚本过滤函数no_xss

function no_xss($str){
	$str = str_replace('	',' ',$str);
	$str = str_replace(':e/*','e',$str);
	$str = str_replace(':ex/*','ex',$str);
	$str = str_replace(':exp/*','exp',$str);
	$str = str_replace(':expr/*','expr',$str);
	$str = str_replace(':expre/*','expre',$str);
	$str = str_replace(':expres/*','expres',$str);
	$str = str_replace(':express/*','express',$str);
	$str = str_replace(':expressi/*','expressi',$str);
	$str = str_replace(':expressio/*','expressio',$str);
	$val=$str;
	$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';
	$search .= '1234567890!@#$%^&#038;*()';
	$search .= '~`";:?+/={}[]-_|\'\\';
	for ($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
		$val = preg_replace('/(&#0{0,8}'.ord($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', 'frameset', 'ilayer', '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{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;  
}

再测试一下:

xss测试

好了,不弹了。
过滤后的代码:

<p>测试测试<span style="color: #ff6600">带颜色字<span style="font-size: small">小字体</span></span><span style="font-size: small">字是小字体</span></p>
<p>测试<span style="background-color: #99cc00">背景色</span>测试</p>
<p>正常的字符:“ja<x>vascript:</p>
<img src="ja<x>vascript:alert(/xss1/)" width=100>
<img src="javas cript:alert(/xss2/)" width=100>
<img src="#" on<x>error=alert(/xss3/)>
<img src="#" style="Xss:ex<x>pression(alert(/xss4/))">
<img src="#"/**/on<x>error=alert(/xss5/) width=100>
<img src="#" on<x>error=alert(/xss6/)>
<img src="#" style="Xss:ex<x>pression(alert(/xss7/));">
<img src="#"/**/on<x>error=alert(/xss8/) width=100>
<img src="#" style="Xssex*/pression(alert(/xss9/));">
<iframe src="http://www.baidu.com" width="600px" height="330px" style="margin: -33px 0 0 -23px; display=inline;" frameborder="0" marginheight="0" marginwidth="0" scrolling="no"></iframe>
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