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| -rw-r--r-- | system/libraries/Security.php | 710 |
1 files changed, 710 insertions, 0 deletions
diff --git a/system/libraries/Security.php b/system/libraries/Security.php new file mode 100644 index 000000000..93da59204 --- /dev/null +++ b/system/libraries/Security.php @@ -0,0 +1,710 @@ +<?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 */
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