//来自codeigniter 清理跨站XSS xss_clean

//Security Class 改编成函数

function remove_invisible_characters($str, $url_encoded = TRUE)

{

    $non_displayables = array();

    if ($url_encoded) {

        $non_displayables[] = '/%0[0-8bcef]/';

        $non_displayables[] = '/%1[0-9a-f]/';

    }

    $non_displayables[] = '/[\\x00-\\x08\\x0B\\x0C\\x0E-\\x1F\\x7F]+/S';

    do {

        $str = preg_replace($non_displayables, '', $str, -1, $count);

    } while ($count);

    return $str;

}

function _convert_attribute($match){

	return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);

}

function _decode_entity($match){

	$str = $match[0];

	if (stristr($str, '&') === FALSE){

		return $str;

	}

	$str = html_entity_decode($str, ENT_COMPAT, 'UTF-8');

	$str = preg_replace('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);

	return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);

}

function _compact_exploded_words($matches)

{

	return preg_replace('/\s+/s', '', $matches[1]).$matches[2];

}

function _filter_attributes($str)

{

	$out = '';

	if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches))

	{

		foreach ($matches[0] as $match)

		{

			$out .= preg_replace("#/\*.*?\*/#s", '', $match);

		}

	}

	return $out;

}

function _js_link_removal($match){

	return str_replace(

		$match[1],

		preg_replace(

			'#href=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si',

			'',

			_filter_attributes(str_replace(array('<', '>'), '', $match[1]))

		),

		$match[0]

	);

}

function _js_img_removal($match){

	return str_replace(

		$match[1],

		preg_replace(

			'#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si',

			'',

			_filter_attributes(str_replace(array('<', '>'), '', $match[1]))

		),

		$match[0]

	);

}

function _sanitize_naughty_html($matches){

	// encode opening brace

	$str = '<'.$matches[1].$matches[2].$matches[3];

	// encode captured opening or closing brace to prevent recursive vectors

	$str .= str_replace(array('>', '<'), array('>', '<'),

						$matches[4]);

	return $str;

}

//调用这个函数

//from http://www.cnblogs.com/osfipin/

function xss_clean($str, $is_image = FALSE){

	/*

	 * Is the string an array?

	 *

	 */

	if (is_array($str))

	{

		while (list($key) = each($str))

		{

			$str[$key] = xss_clean($str[$key]);

		}

		return $str;

	}

	$str = remove_invisible_characters($str);

	// Validate Entities in URLs

	$hash = md5(time() + mt_rand(0, 1999999999));

	$str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $hash."\\1=\\2", $str);

	$str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);

	$str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);

	$str = str_replace($hash, '&', $str);

	$str = rawurldecode($str);

	/*

	 * Convert character entities to ASCII

	 *

	 * This permits our tests below to work reliably.

	 * We only convert entities that are within tags since

	 * these are the ones that will pose security problems.

	 *

	 */

	$str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si",  '_convert_attribute', $str);

	$str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si",  '_decode_entity', $str);

	/*

	 * Remove Invisible Characters Again!

	 */

	$str = remove_invisible_characters($str);

	/*

	 * Convert all tabs to spaces

	 *

	 * This prevents strings like this: ja	vascript

	 * NOTE: we deal with spaces between characters later.

	 * NOTE: preg_replace was found to be amazingly slow here on

	 * large blocks of data, so we use str_replace.

	 */

	if (strpos($str, "\t") !== FALSE)

	{

		$str = str_replace("\t", ' ', $str);

	}

	/*

	 * Capture converted string for later comparison

	 */

	$converted_string = $str;

	// Remove Strings that are never allowed

	$_never_allowed_str = array(

		'document.cookie'	=> '[removed]',

		'document.write'	=> '[removed]',

		'.parentNode'		=> '[removed]',

		'.innerHTML'		=> '[removed]',

		'window.location'	=> '[removed]',

		'-moz-binding'		=> '[removed]',

		'<!--'				=> '<!--',

		'-->'				=> '-->',

		'<![CDATA['			=> '<![CDATA[',

		'<comment>'			=> '<comment>'

	);

	$str = str_replace(array_keys($_never_allowed_str), $_never_allowed_str, $str);

	$_never_allowed_regex = array(

		'javascript\s*:',

		'expression\s*(\(|&\#40;)', // CSS and IE

		'vbscript\s*:', // IE, surprise!

		'Redirect\s+302',

		"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"

	);

	foreach ($_never_allowed_regex as $regex)

	{

		$str = preg_replace('#'.$regex.'#is', '[removed]', $str);

	}

	/*

	 * Makes PHP tags safe

	 *

	 * Note: XML tags are inadvertently replaced too:

	 *

	 * <?xml

	 *

	 * But it doesn't seem to pose a problem.

	 */

	if ($is_image === TRUE)

	{

		// Images have a tendency to have the PHP short opening and

		// closing tags every so often so we skip those and only

		// do the long opening tags.

		$str = preg_replace('/<\?(php)/i', "<?\\1", $str);

	}

	else

	{

		$str = str_replace(array('<?', '?'.'>'),  array('<?', '?>'), $str);

	}

	/*

	 * Compact any exploded words

	 *

	 * This corrects words like:  j a v a s c r i p t

	 * These words are compacted back to their correct state.

	 */

	$words = array(

		'javascript', 'expression', 'vbscript', 'script', 'base64',

		'applet', 'alert', 'document', 'write', 'cookie', 'window'

	);

	foreach ($words as $word)

	{

		$temp = '';

		for ($i = 0, $wordlen = strlen($word); $i < $wordlen; $i++)

		{

			$temp .= substr($word, $i, 1)."\s*";

		}

		// We only want to do this when it is followed by a non-word character

		// That way valid stuff like "dealer to" does not become "dealerto"

		$str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', '_compact_exploded_words', $str);

	}

	/*

	 * Remove disallowed Javascript in links or img tags

	 * We used to do some version comparisons and use of stripos for PHP5,

	 * but it is dog slow compared to these simplified non-capturing

	 * preg_match(), especially if the pattern exists in the string

	 */

	do

	{

		$original = $str;

		if (preg_match("/<a/i", $str))

		{

			$str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", '_js_link_removal', $str);

		}

		if (preg_match("/<img/i", $str))

		{

			$str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", '_js_img_removal', $str);

		}

		if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))

		{

			$str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);

		}

	}

	while($original != $str);

	unset($original);

	// Remove evil attributes such as style, onclick and xmlns

	// All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns

	$evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');

	if ($is_image === TRUE)

	{

		/*

		 * Adobe Photoshop puts XML metadata into JFIF images,

		 * including namespacing, so we have to allow this for images.

		 */

		unset($evil_attributes[array_search('xmlns', $evil_attributes)]);

	}

	do {

		$count = 0;

		$attribs = array();

		// find occurrences of illegal attribute strings with quotes (042 and 047 are octal quotes)

		preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*(\042|\047)([^\\2]*?)(\\2)/is', $str, $matches, PREG_SET_ORDER);

		foreach ($matches as $attr)

		{

			$attribs[] = preg_quote($attr[0], '/');

		}

		// find occurrences of illegal attribute strings without quotes

		preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*([^\s>]*)/is', $str, $matches, PREG_SET_ORDER);

		foreach ($matches as $attr)

		{

			$attribs[] = preg_quote($attr[0], '/');

		}

		// replace illegal attribute strings that are inside an html tag

		if (count($attribs) > 0)

		{

			$str = preg_replace('/(<?)(\/?[^><]+?)([^A-Za-z<>\-])(.*?)('.implode('|', $attribs).')(.*?)([\s><]?)([><]*)/i', '$1$2 $4$6$7$8', $str, -1, $count);

		}

	} while ($count);

	/*

	 * Sanitize naughty HTML elements

	 *

	 * If a tag containing any of the words in the list

	 * below is found, the tag gets converted to entities.

	 *

	 * So this: <blink>

	 * Becomes: <blink>

	 */

	$naughty = 'alert|applet|audio|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|isindex|layer|link|meta|object|plaintext|style|script|textarea|title|video|xml|xss';

	$str = preg_replace_callback('#<(/*\s*)('.$naughty.')([^><]*)([><]*)#is','_sanitize_naughty_html', $str);

	/*

	 * Sanitize naughty scripting elements

	 *

	 * Similar to above, only instead of looking for

	 * tags it looks for PHP and JavaScript commands

	 * that are disallowed.  Rather than removing the

	 * code, it simply converts the parenthesis to entities

	 * rendering the code un-executable.

	 *

	 * For example:	eval('some code')

	 * Becomes:		eval('some code')

	 */

	$str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2(\\3)", $str);

	// Final clean up

	// This adds a bit of extra precaution in case

	// something got through the above filters

	$str = str_replace(array_keys($_never_allowed_str), $_never_allowed_str, $str);

	foreach ($_never_allowed_regex as $regex)

	{

		$str = preg_replace('#'.$regex.'#is', '[removed]', $str);

	}

	/*

	 * Images are Handled in a Special Way

	 * - Essentially, we want to know that after all of the character

	 * conversion is done whether any unwanted, likely XSS, code was found.

	 * If not, we return TRUE, as the image is clean.

	 * However, if the string post-conversion does not matched the

	 * string post-removal of XSS, then it fails, as there was unwanted XSS

	 * code found and removed/changed during processing.

	 */

	if ($is_image === TRUE)

	{

		return ($str == $converted_string) ? TRUE: FALSE;

	}

	return $str;

}

///测试

function show($r){

	echo $r;

	echo '<br/>';

	echo xss_clean($r);

	echo '<br/><br/>';

}

show('%3Cscript%3Ealert(’XSS’)%3C/script%3E');

show('%3c/a%3e%3cscript%3ealert(%22xss%22)%3c/script%3e');

show('<IMG SRC="javascript:alert(’XSS’);">');

show('<STYLE type="text/css">BODY{background:url("javascript:alert(’XSS’)")}</STYLE>');