PHP清理跨站XSS xss_clean 函数 整理自codeigniter Security

//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>‘);