<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); /** * CodeIgniter * * An open source application development framework for PHP 4.3.2 or newer * * @package CodeIgniter * @author ExpressionEngine Dev Team * @copyright Copyright (c) 2008 - 2010, EllisLab, Inc. * @license http://codeigniter.com/user_guide/license.html * @link http://codeigniter.com * @since Version 1.0 * @filesource */ // ------------------------------------------------------------------------ /** * Security Class * * @package CodeIgniter * @subpackage Libraries * @category Security * @author ExpressionEngine Dev Team * @link http://codeigniter.com/user_guide/libraries/sessions.html */ class CI_Security { var $xss_hash = ''; var $csrf_hash = ''; var $csrf_expire = 7200; // Two hours (in seconds) var $csrf_token_name = 'ci_csrf_token'; /* never allowed, string replacement */ var $never_allowed_str = array( 'document.cookie' => '[removed]', 'document.write' => '[removed]', '.parentNode' => '[removed]', '.innerHTML' => '[removed]', 'window.location' => '[removed]', '-moz-binding' => '[removed]', '<!--' => '<!--', '-->' => '-->', '<![CDATA[' => '<![CDATA[' ); /* never allowed, regex replacement */ var $never_allowed_regex = array( "javascript\s*:" => '[removed]', "expression\s*(\(|&\#40;)" => '[removed]', // CSS and IE "vbscript\s*:" => '[removed]', // IE, surprise! "Redirect\s+302" => '[removed]' ); function CI_Security() { // Set the CSRF hash $this->_csrf_set_hash(); log_message('debug', "Security Class Initialized"); } // -------------------------------------------------------------------- /** * Verify Cross Site Request Forgery Protection * * @access public * @return null */ function csrf_verify() { // If no POST data exists we will set the CSRF cookie if (count($_POST) == 0) { return $this->csrf_set_cookie(); } // Do the tokens exist in both the _POST and _COOKIE arrays? if ( ! isset($_POST[$this->csrf_token_name]) OR ! isset($_COOKIE[$this->csrf_token_name])) { $this->csrf_show_error(); } // Do the tokens match? if ($_POST[$this->csrf_token_name] != $_COOKIE[$this->csrf_token_name]) { $this->csrf_show_error(); } // We kill this since we're done and we don't want to polute the _POST array unset($_POST[$this->csrf_token_name]); log_message('debug', "CSRF token verified "); } // -------------------------------------------------------------------- /** * Set Cross Site Request Forgery Protection Cookie * * @access public * @return null */ function csrf_set_cookie() { $prefix = ( ! is_string(config_item('cookie_prefix'))) ? '' : config_item('cookie_prefix'); $expire = time() + $this->csrf_expire; setcookie($prefix.$this->csrf_token_name, $this->csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), 0); log_message('debug', "CRSF cookie Set"); } // -------------------------------------------------------------------- /** * Set Cross Site Request Forgery Protection Cookie * * @access public * @return null */ function _csrf_set_hash() { if ($this->csrf_hash == '') { // If the cookie exists we will use it's value. We don't necessarily want to regenerate it with // each page load since a page could contain embedded sub-pages causing this feature to fail if (isset($_COOKIE[$this->csrf_token_name]) AND $_COOKIE[$this->csrf_token_name] != '') { $this->csrf_hash = $_COOKIE[$this->csrf_token_name]; } else { $this->csrf_hash = md5(uniqid(rand(), TRUE)); } } return $this->csrf_hash; } // -------------------------------------------------------------------- /** * Show CSRF Error * * @access public * @return null */ function csrf_show_error() { show_error('The action you have requested is not allowed.'); } // -------------------------------------------------------------------- /** * XSS Clean * * Sanitizes data so that Cross Site Scripting Hacks can be * prevented. This function does a fair amount of work but * it is extremely thorough, designed to prevent even the * most obscure XSS attempts. Nothing is ever 100% foolproof, * of course, but I haven't been able to get anything passed * the filter. * * Note: This function should only be used to deal with data * upon submission. It's not something that should * be used for general runtime processing. * * This function was based in part on some code and ideas I * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention * * To help develop this script I used this great list of * vulnerabilities along with a few other hacks I've * harvested from examining vulnerabilities in other programs: * http://ha.ckers.org/xss.html * * @access public * @param mixed string or array * @return string */ function xss_clean($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 = $this->_remove_invisible_characters($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 */ $str = str_replace($this->xss_hash(), '&', $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 = $this->_remove_invisible_characters($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. * */ if (strpos($str, "\t") !== FALSE) { $str = str_replace("\t", ' ', $str); } /* * Capture converted string for later comparison */ $converted_string = $str; /* * Not Allowed Under Any Conditions */ foreach ($this->never_allowed_str as $key => $val) { $str = str_replace($key, $val, $str); } foreach ($this->never_allowed_regex as $key => $val) { $str = preg_replace("#".$key."#i", $val, $str); } /* * Makes PHP tags safe * * Note: XML tags are inadvertently replaced too: * * <?xml * * But it doesn't seem to pose a problem. * */ if ($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. * */ $words = array('javascript', 'expression', 'vbscript', 'script', 'applet', 'alert', 'document', 'write', 'cookie', 'window'); foreach ($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', 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 JavaScript Event Handlers * * Note: This code is a little blunt. It removes * the event handler and anything up to the closing >, * but it's unlikely to be a problem. * */ $event_handlers = array('[^a-z_\-]on\w*','xmlns'); if ($is_image === TRUE) { /* * Adobe Photoshop puts XML metadata into JFIF images, including namespacing, * so we have to allow this for images. -Paul */ unset($event_handlers[array_search('xmlns', $event_handlers)]); } $str = preg_replace("#<([^><]+?)(".implode('|', $event_handlers).")(\s*=\s*[^><]*)([><]*)#i", "<\\1\\4", $str); /* * 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)", $str); /* * Final clean up * * This adds a bit of extra precaution in case * something got through the above filters * */ foreach ($this->never_allowed_str as $key => $val) { $str = str_replace($key, $val, $str); } foreach ($this->never_allowed_regex as $key => $val) { $str = preg_replace("#".$key."#i", $val, $str); } /* * Images are Handled in a Special Way * - Essentially, we want to know that after all of the character conversion is done whether * any unwanted, likely XSS, code was found. If not, we return TRUE, as the image is clean. * However, if the string post-conversion does not matched the string post-removal of XSS, * then it fails, as there was unwanted XSS code found and removed/changed during processing. */ if ($is_image === TRUE) { if ($str == $converted_string) { return TRUE; } else { return FALSE; } } log_message('debug', "XSS Filtering completed"); return $str; } // -------------------------------------------------------------------- /** * Random Hash for protecting URLs * * @access public * @return string */ function xss_hash() { if ($this->xss_hash == '') { if (phpversion() >= 4.2) mt_srand(); else mt_srand(hexdec(substr(md5(microtime()), -8)) & 0x7fffffff); $this->xss_hash = md5(time() + mt_rand(0, 1999999999)); } return $this->xss_hash; } // -------------------------------------------------------------------- /** * Remove Invisible Characters * * This prevents sandwiching null characters * between ascii characters, like Java\0script. * * @access public * @param string * @return string */ function _remove_invisible_characters($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 $str; } // -------------------------------------------------------------------- /** * Compact Exploded Words * * Callback function for xss_clean() to remove whitespace from * things like j a v a s c r i p t * * @access public * @param type * @return type */ function _compact_exploded_words($matches) { return preg_replace('/\s+/s', '', $matches[1]).$matches[2]; } // -------------------------------------------------------------------- /** * Sanitize Naughty HTML * * Callback function for xss_clean() to remove naughty HTML elements * * @access private * @param array * @return string */ 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 $str; } // -------------------------------------------------------------------- /** * JS Link Removal * * Callback function for xss_clean() to sanitize links * This limits the PCRE backtracks, making it more performance friendly * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in * PHP 5.2+ on link-heavy strings * * @access private * @param array * @return string */ function _js_link_removal($match) { $attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1])); return str_replace($match[1], preg_replace("#href=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]); } /** * JS Image Removal * * Callback function for xss_clean() to sanitize image tags * This limits the PCRE backtracks, making it more performance friendly * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in * PHP 5.2+ on image tag heavy strings * * @access private * @param array * @return string */ function _js_img_removal($match) { $attributes = $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1])); return str_replace($match[1], preg_replace("#src=.*?(alert\(|alert&\#40;|javascript\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si", "", $attributes), $match[0]); } // -------------------------------------------------------------------- /** * Attribute Conversion * * Used as a callback for XSS Clean * * @access public * @param array * @return string */ function _convert_attribute($match) { return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]); } // -------------------------------------------------------------------- /** * Filter Attributes * * Filters tag attributes for consistency and safety * * @access public * @param string * @return string */ function _filter_attributes($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 $out; } // -------------------------------------------------------------------- /** * HTML Entity Decode Callback * * Used as a callback for XSS Clean * * @access public * @param array * @return string */ function _decode_entity($match) { $CI =& get_instance(); $CI->load->helper('typography'); return entity_decode($match[0], strtoupper($CI->config->item('charset'))); } // -------------------------------------------------------------------- /** * Filename Security * * @access public * @param string * @return string */ function sanitize_filename($str) { $bad = array( "../", "./", "<!--", "-->", "<", ">", "'", '"', '&', '$', '#', '{', '}', '[', ']', '=', ';', '?', '/', "%20", "%22", "%3c", // < "%253c", // < "%3e", // > "%0e", // > "%28", // ( "%29", // ) "%2528", // ( "%26", // & "%24", // $ "%3f", // ? "%3b", // ; "%3d" // = ); return stripslashes(str_replace($bad, '', $str)); } } // END Security Class /* End of file Security.php */ /* Location: ./system/libraries/Security.php */