<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed'); /** * CodeIgniter * * An open source application development framework for PHP 5.1.6 or newer * * @package CodeIgniter * @author ExpressionEngine Dev Team * @copyright Copyright (c) 2008 - 2011, 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/security.html */ class CI_Security { /** * Random Hash for protecting URLs * * @var string * @access protected */ protected $_xss_hash = ''; /** * Random Hash for Cross Site Request Forgery Protection Cookie * * @var string * @access protected */ protected $_csrf_hash = ''; /** * Expiration time for Cross Site Request Forgery Protection Cookie * Defaults to two hours (in seconds) * * @var int * @access protected */ protected $_csrf_expire = 7200; /** * Token name for Cross Site Request Forgery Protection Cookie * * @var string * @access protected */ protected $_csrf_token_name = 'ci_csrf_token'; /** * Cookie name for Cross Site Request Forgery Protection Cookie * * @var string * @access protected */ protected $_csrf_cookie_name = 'ci_csrf_token'; /** * List of never allowed strings * * @var array * @access protected */ 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?" ); /** * Constructor */ public function __construct() { // CSRF config foreach(array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key) { if (FALSE !== ($val = config_item($key))) { $this->{'_'.$key} = $val; } } // Append application specific cookie prefix if (config_item('cookie_prefix')) { $this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name; } // Set the CSRF hash $this->_csrf_set_hash(); log_message('debug', "Security Class Initialized"); } // -------------------------------------------------------------------- /** * Verify Cross Site Request Forgery Protection * * @return object */ public function csrf_verify() { // If no POST data exists we will set the CSRF cookie if (count($_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_cookie_name])) { $this->csrf_show_error(); } // Do the tokens match? if ($_POST[$this->_csrf_token_name] != $_COOKIE[$this->_csrf_cookie_name]) { $this->csrf_show_error(); } // We kill this since we're done and we don't want to // polute the _POST array unset($_POST[$this->_csrf_token_name]); // Nothing should last forever unset($_COOKIE[$this->_csrf_cookie_name]); $this->_csrf_set_hash(); $this->csrf_set_cookie(); log_message('debug', "CSRF token verified "); return $this; } // -------------------------------------------------------------------- /** * Set Cross Site Request Forgery Protection Cookie * * @return object */ public function csrf_set_cookie() { $expire = time() + $this->_csrf_expire; $secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0; if ($secure_cookie) { $req = isset($_SERVER['HTTPS']) ? $_SERVER['HTTPS'] : FALSE; if ( ! $req OR $req == 'off') { return FALSE; } } setcookie($this->_csrf_cookie_name, $this->_csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), $secure_cookie); log_message('debug', "CRSF cookie Set"); return $this; } // -------------------------------------------------------------------- /** * Show CSRF Error * * @return void */ public function csrf_show_error() { show_error('The action you have requested is not allowed.'); } // -------------------------------------------------------------------- /** * Get CSRF Hash * * Getter Method * * @return string self::_csrf_hash */ public function get_csrf_hash() { return $this->_csrf_hash; } // -------------------------------------------------------------------- /** * Get CSRF Token Name * * Getter Method * * @return string self::csrf_token_name */ public function get_csrf_token_name() { return $this->_csrf_token_name; } // -------------------------------------------------------------------- /** * XSS Clean * * Sanitizes data so that Cross Site Scripting Hacks can be * prevented. This function does a fair amount of work but * it is extremely thorough, designed to prevent even the * most obscure XSS attempts. Nothing is ever 100% foolproof, * of course, but I haven't been able to get anything passed * the filter. * * Note: This function should only be used to deal with data * upon submission. It's not something that should * be used for general runtime processing. * * This function was based in part on some code and ideas I * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention * * To help develop this script I used this great list of * vulnerabilities along with a few other hacks I've * harvested from examining vulnerabilities in other programs: * http://ha.ckers.org/xss.html * * @param mixed string or array * @param bool * @return string */ public function xss_clean($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*"; } // 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 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; } log_message('debug', "XSS Filtering completed"); 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, '', $str)); } // ---------------------------------------------------------------- /** * Compact Exploded Words * * Callback function for xss_clean() to remove whitespace from * things like j a v a s c r i p t * * @param type * @return type */ protected function _compact_exploded_words($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'))); } // -------------------------------------------------------------------- /** * Validate URL entities * * Called by xss_clean() * * @param string * @return string */ protected 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 */ $str = str_replace($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) { $str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str); foreach ($this->_never_allowed_regex as $regex) { $str = preg_replace('#'.$regex.'#is', '[removed]', $str); } return $str; } // -------------------------------------------------------------------- /** * Set Cross Site Request Forgery Protection Cookie * * @return string */ protected function _csrf_set_hash() { if ($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_cookie_name]) && preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1) { return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name]; } return $this->_csrf_hash = md5(uniqid(rand(), TRUE)); } return $this->_csrf_hash; } } // END Security Class /* End of file Security.php */ /* Location: ./system/libraries/Security.php */