'[removed]', 'document.write' => '[removed]', '.parentNode' => '[removed]', '.innerHTML' => '[removed]', 'window.location' => '[removed]', '-moz-binding' => '[removed]', '' => '-->', ' '<![CDATA[', '' => '<comment>' ); /** * List of never allowed regex replacement * * @var array * * @access private */ var $_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?" ); /** * Sanitizes submitted data so that Cross Site Scripting Hacks can be prevented. * * This class is taken from the {@link http://codeigniter.com/ CodeIgniter PHP Framework}, * version 2.1.2. * * This method is automatically run for each control when calling {@link Zebra_Form::validate() validate()}, unless * specifically disabled by {@link Zebra_Form_Control::disable_xss_filters() disable_xss_filters()})! * * Following is the original documentation of the class, as found in CodeIgniter: * * Sanitizes data so that Cross Site Scripting Hacks can be prevented. This function does a fair amount of work but * it is extremely thorough, designed to prevent even the most obscure XSS attempts. Nothing is ever 100% foolproof, * of course, but I haven't been able to get anything passed the filter. * * Note: This function should only be used to deal with data upon submission. It's not something that should be used * for general runtime processing. * * This function was based in part on some code and ideas I got from Bitflux: * {@link http://blog.bitflux.ch/wiki/XSS_Prevention} * * To help develop this script I used this great list of vulnerabilities along with a few other hacks I've * harvested from examining vulnerabilities in other programs: {@link http://ha.ckers.org/xss.html} * * @param string $str String to be filtered * * @return string Returns filtered string */ function sanitize($str, $rawurldecode = true) { // Remove Invisible Characters $str = $this->_remove_invisible_characters($str); /* * URL Decode * * Just in case stuff like this is submitted: * * Google * * Note: Use rawurldecode() so it does not remove plus signs */ if ($rawurldecode) $str = rawurldecode($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 = $this->_remove_invisible_characters($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. */ $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: * * '), 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) { $word = implode('\s*', str_split($word)).'\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" $str = preg_replace_callback('#('.substr($word, 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 = $str; if (preg_match('/]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str); } if (preg_match('/]*?)(?:\s?/?\>|$)#si', array($this, '_js_img_removal'), $str); } if (preg_match('/script|xss/i', $str)) { $str = preg_replace('##si', '[removed]', $str); } } while ($original !== $str); unset($original); // Remove evil attributes such as style, onclick and xmlns $str = $this->_remove_evil_attributes($str, false); /* * 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: * 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); return $str; } // -------------------------------------------------------------------- /** * Random Hash for protecting URLs * * @return string * * @access private */ function xss_hash() { if ($this->_xss_hash === '') { mt_srand(); $this->_xss_hash = md5(time() + mt_rand(0, 1999999999)); } return $this->_xss_hash; } // -------------------------------------------------------------------- /** * HTML Entities Decode * * This function is a replacement for html_entity_decode() * * The reason we are not using html_entity_decode() by itself is because * while it is not technically correct to leave out the semicolon * at the end of an entity most browsers will still interpret the entity * correctly. html_entity_decode() does not convert entities without * semicolons, so we are left with our own little solution here. Bummer. * * @param string * @param string * @return string * * @access private */ function entity_decode($str, $charset = NULL) { if (strpos($str, '&') === FALSE) { return $str; } if (empty($charset)) { $charset = 'UTF-8'; } $str = html_entity_decode($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)', $str); } // ---------------------------------------------------------------- /** * Compact Exploded Words * * Callback function for xss_clean() to remove whitespace from * things like j a v a s c r i p t * * @param array * @return string * * @access private */ function _compact_exploded_words($matches) { return preg_replace('/\s+/s', '', $matches[1]).$matches[2]; } // -------------------------------------------------------------------- /** * Remove Evil HTML Attributes (like event handlers and style) * * It removes the evil attribute and either: * - Everything up until a space * For example, everything between the pipes: * * - Everything inside the quotes * For example, everything between the pipes: * * * @param string $str The string to check * @param boolean $is_image TRUE if this is an image * @return string The string with the evil attributes removed * * @access private */ function _remove_evil_attributes($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 $str; } // -------------------------------------------------------------------- /** * Sanitize Naughty HTML * * Callback function for xss_clean() to remove naughty HTML elements * * @param array * @return string * * @access private */ function _sanitize_naughty_html($matches) { return '<'.$matches[1].$matches[2].$matches[3] // encode opening brace // encode captured opening or closing brace to prevent recursive vectors: .str_replace(array('>', '<'), array('>', '<'), $matches[4]); } // -------------------------------------------------------------------- /** * JS Link Removal * * Callback function for xss_clean() to sanitize links * This limits the PCRE backtracks, making it more performance friendly * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in * PHP 5.2+ on link-heavy strings * * @param array * @return string * * @access private */ function _js_link_removal($match) { return str_replace($match[1], preg_replace('#href=.*?(?:alert\(|alert&\#40;|javascript:|livescript:|mocha:|charset=|window\.|document\.|\.cookie|_filter_attributes(str_replace(array('<', '>'), '', $match[1])) ), $match[0]); } // -------------------------------------------------------------------- /** * JS Image Removal * * Callback function for xss_clean() to sanitize image tags * This limits the PCRE backtracks, making it more performance friendly * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in * PHP 5.2+ on image tag heavy strings * * @param array * @return string * * @access private */ function _js_img_removal($match) { return str_replace($match[1], preg_replace('#src=.*?(?:alert\(|alert&\#40;|javascript:|livescript:|mocha:|charset=|window\.|document\.|\.cookie|_filter_attributes(str_replace(array('<', '>'), '', $match[1])) ), $match[0]); } // -------------------------------------------------------------------- /** * Attribute Conversion * * Used as a callback for XSS Clean * * @param array * @return string * * @access private */ function _convert_attribute($match) { return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]); } // -------------------------------------------------------------------- /** * Filter Attributes * * Filters tag attributes for consistency and safety * * @param string * @return string * * @access private */ function _filter_attributes($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 $out; } // -------------------------------------------------------------------- /** * HTML Entity Decode Callback * * Used as a callback for XSS Clean * * @param array * @return string * * @access private */ function _decode_entity($match) { return $this->entity_decode($match[0], strtoupper('UTF-8')); } // -------------------------------------------------------------------- /** * Validate URL entities * * Called by xss_clean() * * @param string * @return string * * @access private */ function _validate_entities($str) { /* * Protect GET variables in URLs */ // 901119URL5918AMP18930PROTECT8198 $str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash().'\\1=\\2', $str); /* * Validate standard character entities * * Add a semicolon if missing. We do this to enable * the conversion of entities to ASCII later. */ $str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', '\\1;\\2', $str); /* * Validate UTF16 two byte encoding (x00) * * Just as above, adds a semicolon if missing. */ $str = preg_replace('#(&\#x?)([0-9A-F]+);?#i', '\\1\\2;', $str); /* * Un-Protect GET variables in URLs */ return str_replace($this->xss_hash(), '&', $str); } // ---------------------------------------------------------------------- /** * Do Never Allowed * * A utility function for xss_clean() * * @param string * @return string * * @access private */ function _do_never_allowed($str) { $str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str); foreach ($this->_never_allowed_regex as $regex) { $str = preg_replace('#'.$regex.'#is', '[removed]', $str); } return $str; } /** * Remove Invisible Characters * * This prevents sandwiching null characters * between ascii characters, like Java\0script. * * @access private * @param string * @return string */ function _remove_invisible_characters($str) { static $non_displayables; if ( ! isset($non_displayables)) { // every control character except newline (dec 10), carriage return (dec 13), and horizontal tab (dec 09), $non_displayables = array( '/%0[0-8bcef]/', // url encoded 00-08, 11, 12, 14, 15 '/%1[0-9a-f]/', // url encoded 16-31 '/[\x00-\x08]/', // 00-08 '/\x0b/', '/\x0c/', // 11, 12 '/[\x0e-\x1f]/' // 14-31 ); } do { $cleaned = $str; $str = preg_replace($non_displayables, '', $str); } while ($cleaned != $str); return $str; } } ?>