《php清除XSS通用类：CI框架的XSS移除类》要点：
本文介绍了php清除XSS通用类：CI框架的XSS移除类，希望对您有用。如果有疑问，可以联系我们。
前端在线编辑器提供给用户录入文章内容，或论坛贴子，因此也会成为用户攻击的一个渠道，其中主要有XSS攻击和图片上传攻击等等。
本文着重讲解XSS攻击和过滤，让网站更安全。
下面是一个CI框架的XSS过滤类。处理这类攻击很好用。
调用：
$str = '
这是一个正常链接 <a href="http://asdfsd.com">链接1</a>，
这是一个有罪恶属性的链接 <a href="http://www.asdfsd.com" onmousemove="alert(\'a\')">链接1</a>，<br />
这是一个图片<img src="http://www.baidu.com/img/baidu_sylogo1.gif" border="0" onclick="alert(\'hi\')" />，
这是一个脚本<script>alert("hi")</script>
这是一个文本框<input type="text" size="14" onmousemove="alert(\'a\')" border="1" /> <br />
这是一个加粗字<strong>STRONG</strong>和<b>B</b>
';
$xssFilter = new cleanXSS();
$str = $xssFilter->xss_clean($str,FALSE);
echo $str;
/*
这是一个正常链接 <a href="http://asdfsd.com">链接1</a>，
这是一个有罪恶属性的链接 <a >链接1</a>，<br />
这是一个图片<img />，
这是一个脚本[removed]alert("hi")[removed]
这是一个文本框<input type="text" size="14" border="1" /><br />
这是一个加粗字<strong>STRONG</strong>和<b>B</b>';
即：
任何有非法属性的脚本均标记为[removed]alert("hi")[removed]
对于链接、图片则只留空标签
注意：框<input type="text" size="14" onmousemove="alert(\'a\')" border="1" /> <br />这两个标
签，后面的<br />如果紧靠前面一个，则会被转化成<br />
*/类文件：
//适用于在线编辑器、URL
class cleanXSS
{
protected $_xss_hash = '';
protected $_never_allowed_str = array( 'document.cookie' => '[removed]', 'document.write' => '[removed]', '.parentNode' => '[removed]', '.innerHTML' => '[removed]', 'window.location' => '[removed]', '-moz-binding' => '[removed]', '<!--' => '<!--', '-->' => '-->', '<![CDATA[' => '<![CDATA[', '<comment>' => '<comment>' );
/* never allowed, regex replacement */
/**
* List of never allowed regex replacement
*
* @var array
* @access protected
*/
protected $_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?" );
public function __construct ()
{
}
public function xss_clean ( $str, $is_image = FALSE )
{
/*
* Is the string an array?
*
*/
if ( is_array ( $str ) ) {
while ( list( $key ) = each ( $str ) ) {
$str[$key] = $this->xss_clean ( $str[$key] );
}
return $str;
}
/*
* Remove Invisible Characters
*/
$str = remove_invisible_characters ( $str );
// Validate Entities in URLs
$str = $this->_validate_entities ( $str );
/*
* URL Decode
*
* Just in case stuff like this is submitted:
*
* <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
*
* Note: Use rawurldecode() so it does not remove plus signs
*
*/
$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", array( $this, '_convert_attribute' ), $str );
$str = preg_replace_callback ( "/<\w+.*?(?=>|<|$)/si", array( $this, '_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
$str = $this->_do_never_allowed ( $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*";
}
// 再删除空白
// 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"
// $temp的值比如："w\s*i\s*n\s*d\s*o\s*w\s*"，substr($temp, 0, -3)即截取头到最后面空格前的一个字母。
$str = preg_replace_callback ( '#(' . substr ( $temp, 0, -3 ) . ')(\W)#is', array( $this, '_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", array( $this, '_js_link_removal' ), $str );
}
if ( preg_match ( "/<img/i", $str ) ) {
$str = preg_replace_callback ( "#<img\s+([^>]*?)(\s?/?>|$)#si", array( $this, '_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
$str = $this->_remove_evil_attributes ( $str, $is_image );
/*
* 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', array( $this, '_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 = $this->_do_never_allowed ( $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;
}
$str = preg_replace ( '/(\[removed\]).*\\1/iUs', '', $str );
return $str;
}
// --------------------------------------------------------------------
/**
* Random Hash for protecting URLs
*
* @return string
*/
public function xss_hash ()
{
if ( $this->_xss_hash == '' ) {
mt_srand ();
$this->_xss_hash = md5 ( time () + mt_rand ( 0, 1999999999 ) );
}
return $this->_xss_hash;
}
// --------------------------------------------------------------------
/**
* HTML Entities Decode
* This function is a replacement for html_entity_decode()
* The reason we are not using html_entity_decode() by itself is because
* while it is not technically correct to leave out the semicolon
* at the end of an entity most browsers will still interpret the entity
* correctly. html_entity_decode() does not convert entities without
* semicolons, so we are left with our own little solution here. Bummer.
*
* @param string
* @param string
* @return string
*/
public function entity_decode ( $str, $charset = 'UTF-8' )
{
if ( stristr ( $str, '&' ) === FALSE ) {
return $str;
}
$str = html_entity_decode ( $str, ENT_COMPAT, $charset );
$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 );
}
// --------------------------------------------------------------------
/**
* Filename Security
* @param string
* @param bool
* @return string
*/
public function sanitize_filename ( $str, $relative_path = FALSE )
{
$bad = array( "../", "<!--", "-->", "<", ">", "'", '"', '&', '$', '#', '{', '}', '[', ']', '=', ';', '?', "%20", "%22", "%3c", // <
"%253c", // <
"%3e", // >
"%0e", // >
"%28", // (
"%29", // )
"%2528", // (
"%26", // &
"%24", // $
"%3f", // ?
"%3b", // ;
"%3d" // =
);
if ( !$relative_path ) {
$bad[] = './';
$bad[] = '/';
}
$str = remove_invisible_characters ( $str, FALSE );
return stripslashes ( str_replace ( $bad, '', $str ) );
}
// ----------------------------------------------------------------
/** $str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);
* Compact Exploded Words
*
* Callback function for xss_clean() to remove whitespace from
* things like j a v a s c r i p t
*
* @param type
* @return type
*/
protected function _compact_exploded_words ( $matches )
{
return preg_replace ( '/\s+/s', '', $matches[1] ) . $matches[2];
}
// --------------------------------------------------------------------
/*
* Remove Evil HTML Attributes (like evenhandlers and style)
*
* It removes the evil attribute and either:
* - Everything up until a space
* For example, everything between the pipes:
* <a |style=document.write('hello');alert('world');| class=link>
* - Everything inside the quotes
* For example, everything between the pipes:
* <a |style="document.write('hello'); alert('world');"| class="link">
*
* @param string $str The string to check
* @param boolean $is_image TRUE if this is an image
* @return string The string with the evil attributes removed
*/
protected function _remove_evil_attributes ( $str, $is_image )
{
// 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 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], '/' );
}
// 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], '/' );
}
// 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 $3$5$6$7', $str, -1, $count );
}
} while ( $count );
return $str;
}
// --------------------------------------------------------------------
/**
* Sanitize Naughty HTML
*
* Callback function for xss_clean() to remove naughty HTML elements
*
* @param array
* @return string
*/
protected 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;
}
// --------------------------------------------------------------------
/**
* JS Link Removal
*
* Callback function for xss_clean() to sanitize links
* This limits the PCRE backtracks, making it more performance friendly
* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
* PHP 5.2+ on link-heavy strings
*
* @param array
* @return string
*/
protected 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', '', $this->_filter_attributes ( str_replace ( array( '<', '>' ), '', $match[1] ) ) ), $match[0] );
}
// --------------------------------------------------------------------
/**
* JS Image Removal
*
* Callback function for xss_clean() to sanitize image tags
* This limits the PCRE backtracks, making it more performance friendly
* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
* PHP 5.2+ on image tag heavy strings
*
* @param array
* @return string
*/
protected 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', '', $this->_filter_attributes ( str_replace ( array( '<', '>' ), '', $match[1] ) ) ), $match[0] );
}
// --------------------------------------------------------------------
/**
* Attribute Conversion
* Used as a callback for XSS Clean
* @param array
* @return string
*/
protected function _convert_attribute ( $match )
{
return str_replace ( array( '>', '<', '\\' ), array( '>', '<', '\\\\' ), $match[0] );
}
// --------------------------------------------------------------------
/**
* Filter Attributes
* Filters tag attributes for consistency and safety
* @param string
* @return string
*/
protected 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;
}
// --------------------------------------------------------------------
/**
* HTML Entity Decode Callback
* Used as a callback for XSS Clean
* @param array
* @return string
*/
protected function _decode_entity ( $match )
{
//return $this->entity_decode($match[0], strtoupper(config_item('charset')));
return $this->entity_decode ( $match[0], 'utf-8' );
}
// --------------------------------------------------------------------
/**
* Validate URL entities
* Called by xss_clean()
* @param string
* @return string
*/
protected function _validate_entities ( $str )
{
/*
* 检测GET变量中的URLs，先用xss_hash()替换掉"&"，稍后再换"&"回
*/
// 901119URL5918AMP18930PROTECT8198 #$this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
$str = preg_replace ( '|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash () . "\\1=\\2", $str );
/*
* 验证标准字符实体。
* 添加一个分号（如无分号的话），这么做是为了稍后转换实体到ASCII符
*/
$str = preg_replace ( '#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str );
/*
* 验证 UTF16 双字节编码 (x00)
* 同上，如无分号则添加分号。
*/
$str = preg_replace ( '#(&\#x?)([0-9A-F]+);?#i', "\\1\\2;", $str );
/*
* Un-Protect GET variables in URLs
*/
$str = str_replace ( $this->xss_hash (), '&', $str );
return $str;
}
// ----------------------------------------------------------------------
/**
* Do Never Allowed
* A utility function for xss_clean()
* @param string
* @return string
*/
protected function _do_never_allowed ( $str )
{
//把其中的document.cookie等替换成[removed]等。
$str = str_replace ( array_keys ( $this->_never_allowed_str ), $this->_never_allowed_str, $str );
foreach ( $this->_never_allowed_regex as $regex ) {
$str = preg_replace ( '#' . $regex . '#is', '[removed]', $str );
}
return $str;
}
}
function remove_invisible_characters ( $str, $url_encoded = TRUE )
{
$non_displayables = array();
// every control character except newline (dec 10)
// carriage return (dec 13), and horizontal tab (dec 09)
if ( $url_encoded ) {
$non_displayables[] = '/%0[0-8bcef]/'; // url encoded 00-08, 11, 12, 14, 15
$non_displayables[] = '/%1[0-9a-f]/'; // url encoded 16-31
}
$non_displayables[] = '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]+/S'; // 00-08, 11, 12, 14-31, 127
do {
$str = preg_replace ( $non_displayables, '', $str, -1, $count );
} while ( $count );
return $str;
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