Input.php

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<?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, EllisLab, Inc.
 * @license             http://codeigniter.com/user_guide/license.html
 * @link                http://codeigniter.com
 * @since               Version 1.0
 * @filesource
 */

// ------------------------------------------------------------------------

/**
 * Input Class
 *
 * Pre-processes global input data for security
 *
 * @package             CodeIgniter
 * @subpackage  Libraries
 * @category    Input
 * @author              ExpressionEngine Dev Team
 * @link                http://codeigniter.com/user_guide/libraries/input.html
 */
class CI_Input {
        var $use_xss_clean              = FALSE;
        var $xss_hash                   = '';
        var $ip_address                 = FALSE;
        var $user_agent                 = FALSE;
        var $allow_get_array    = FALSE;
        
        /* 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]',
                                                                        '<!--'                          => '&lt;!--',
                                                                        '-->'                           => '--&gt;',
                                                                        '<![CDATA['                     => '&lt;![CDATA['
                                                                        );
        /* never allowed, regex replacement */
        var $never_allowed_regex = array(
                                                                                "javascript\s*:"        => '[removed]',
                                                                                "expression\s*\("       => '[removed]', // CSS and IE
                                                                                "Redirect\s+302"        => '[removed]'
                                                                        );
                                
        /**
         * Constructor
         *
         * Sets whether to globally enable the XSS processing
         * and whether to allow the $_GET array
         *
         * @access      public
         */
        function CI_Input()
        {
                log_message('debug', "Input Class Initialized");

                $CFG =& load_class('Config');
                $this->use_xss_clean    = ($CFG->item('global_xss_filtering') === TRUE) ? TRUE : FALSE;
                $this->allow_get_array  = ($CFG->item('enable_query_strings') === TRUE) ? TRUE : FALSE;
                $this->_sanitize_globals();
        }

        // --------------------------------------------------------------------

        /**
         * Sanitize Globals
         *
         * This function does the following:
         *
         * Unsets $_GET data (if query strings are not enabled)
         *
         * Unsets all globals if register_globals is enabled
         *
         * Standardizes newline characters to \n
         *
         * @access      private
         * @return      void
         */
        function _sanitize_globals()
        {
                // Would kind of be "wrong" to unset any of these GLOBALS
                $protected = array('_SERVER', '_GET', '_POST', '_FILES', '_REQUEST', '_SESSION', '_ENV', 'GLOBALS', 'HTTP_RAW_POST_DATA',
                                                        'system_folder', 'application_folder', 'BM', 'EXT', 'CFG', 'URI', 'RTR', 'OUT', 'IN');

                // Unset globals for security. 
                // This is effectively the same as register_globals = off
                foreach (array($_GET, $_POST, $_COOKIE, $_SERVER, $_FILES, $_ENV, (isset($_SESSION) && is_array($_SESSION)) ? $_SESSION : array()) as $global)
                {
                        if ( ! is_array($global))
                        {
                                if ( ! in_array($global, $protected))
                                {
                                        unset($GLOBALS[$global]);
                                }
                        }
                        else
                        {
                                foreach ($global as $key => $val)
                                {
                                        if ( ! in_array($key, $protected))
                                        {
                                                unset($GLOBALS[$key]);
                                        }
                        
                                        if (is_array($val))
                                        {
                                                foreach($val as $k => $v)
                                                {
                                                        if ( ! in_array($k, $protected))
                                                        {
                                                                unset($GLOBALS[$k]);
                                                        }
                                                }
                                        }
                                }
                        }
                }

                // Is $_GET data allowed? If not we'll set the $_GET to an empty array
                if ($this->allow_get_array == FALSE)
                {
                        $_GET = array();
                }
                else
                {
                        $_GET = $this->_clean_input_data($_GET);
                }

                // Clean $_POST Data
                $_POST = $this->_clean_input_data($_POST);
                
                // Clean $_COOKIE Data
                // Also get rid of specially treated cookies that might be set by a server
                // or silly application, that are of no use to a CI application anyway
                // but that when present will trip our 'Disallowed Key Characters' alarm
                // http://www.ietf.org/rfc/rfc2109.txt
                // note that the key names below are single quoted strings, and are not PHP variables
                unset($_COOKIE['$Version']);
                unset($_COOKIE['$Path']);
                unset($_COOKIE['$Domain']);
                $_COOKIE = $this->_clean_input_data($_COOKIE);

                log_message('debug', "Global POST and COOKIE data sanitized");
        }

        // --------------------------------------------------------------------

        /**
         * Clean Input Data
         *
         * This is a helper function. It escapes data and
         * standardizes newline characters to \n
         *
         * @access      private
         * @param       string
         * @return      string
         */
        function _clean_input_data($str)
        {
                if (is_array($str))
                {
                        $new_array = array();
                        foreach ($str as $key => $val)
                        {
                                $new_array[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
                        }
                        return $new_array;
                }

                // We strip slashes if magic quotes is on to keep things consistent
                if (get_magic_quotes_gpc())
                {
                        $str = stripslashes($str);
                }

                // Should we filter the input data?
                if ($this->use_xss_clean === TRUE)
                {
                        $str = $this->xss_clean($str);
                }

                // Standardize newlines
                if (strpos($str, "\r") !== FALSE)
                {
                        $str = str_replace(array("\r\n", "\r"), "\n", $str);
                }
                
                return $str;
        }

        // --------------------------------------------------------------------

        /**
         * Clean Keys
         *
         * This is a helper function. To prevent malicious users
         * from trying to exploit keys we make sure that keys are
         * only named with alpha-numeric text and a few other items.
         *
         * @access      private
         * @param       string
         * @return      string
         */
        function _clean_input_keys($str)
        {
                 if ( ! preg_match("/^[a-z0-9:_\/-]+$/i", $str))
                 {
                        exit('Disallowed Key Characters.');
                 }

                return $str;
        }

        // --------------------------------------------------------------------
        
        /**
         * Fetch from array
         *
         * This is a helper function to retrieve values from global arrays
         *
         * @access      private
         * @param       array
         * @param       string
         * @param       bool
         * @return      string
         */
        function _fetch_from_array(&$array, $index = '', $xss_clean = FALSE)
        {
                if ( ! isset($array[$index]))
                {
                        return FALSE;
                }

                if ($xss_clean === TRUE)
                {
                        return $this->xss_clean($array[$index]);
                }

                return $array[$index];
        }

        // --------------------------------------------------------------------
        
        /**
         * Fetch an item from the GET array
         *
         * @access      public
         * @param       string
         * @param       bool
         * @return      string
         */
        function get($index = '', $xss_clean = FALSE)
        {
                return $this->_fetch_from_array($_GET, $index, $xss_clean);
        }

        // --------------------------------------------------------------------

        /**
         * Fetch an item from the POST array
         *
         * @access      public
         * @param       string
         * @param       bool
         * @return      string
         */
        function post($index = '', $xss_clean = FALSE)
        {
                return $this->_fetch_from_array($_POST, $index, $xss_clean);
        }

        // --------------------------------------------------------------------

        /**
         * Fetch an item from either the GET array or the POST
         *
         * @access      public
         * @param       string  The index key
         * @param       bool    XSS cleaning
         * @return      string
         */
        function get_post($index = '', $xss_clean = FALSE)
        {               
                if ( ! isset($_POST[$index]) )
                {
                        return $this->get($index, $xss_clean);
                }
                else
                {
                        return $this->post($index, $xss_clean);
                }               
        }

        // --------------------------------------------------------------------

        /**
         * Fetch an item from the COOKIE array
         *
         * @access      public
         * @param       string
         * @param       bool
         * @return      string
         */
        function cookie($index = '', $xss_clean = FALSE)
        {
                return $this->_fetch_from_array($_COOKIE, $index, $xss_clean);
        }

        // --------------------------------------------------------------------

        /**
         * Fetch an item from the SERVER array
         *
         * @access      public
         * @param       string
         * @param       bool
         * @return      string
         */
        function server($index = '', $xss_clean = FALSE)
        {
                return $this->_fetch_from_array($_SERVER, $index, $xss_clean);
        }

        // --------------------------------------------------------------------

        /**
         * Fetch the IP Address
         *
         * @access      public
         * @return      string
         */
        function ip_address()
        {
                if ($this->ip_address !== FALSE)
                {
                        return $this->ip_address;
                }

                if ($this->server('REMOTE_ADDR') AND $this->server('HTTP_CLIENT_IP'))
                {
                         $this->ip_address = $_SERVER['HTTP_CLIENT_IP'];
                }
                elseif ($this->server('REMOTE_ADDR'))
                {
                         $this->ip_address = $_SERVER['REMOTE_ADDR'];
                }
                elseif ($this->server('HTTP_CLIENT_IP'))
                {
                         $this->ip_address = $_SERVER['HTTP_CLIENT_IP'];
                }
                elseif ($this->server('HTTP_X_FORWARDED_FOR'))
                {
                         $this->ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
                }

                if ($this->ip_address === FALSE)
                {
                        $this->ip_address = '0.0.0.0';
                        return $this->ip_address;
                }

                if (strstr($this->ip_address, ','))
                {
                        $x = explode(',', $this->ip_address);
                        $this->ip_address = end($x);
                }

                if ( ! $this->valid_ip($this->ip_address))
                {
                        $this->ip_address = '0.0.0.0';
                }
                
                return $this->ip_address;
        }

        // --------------------------------------------------------------------

        /**
         * Validate IP Address
         *
         * Updated version suggested by Geert De Deckere
         * 
         * @access      public
         * @param       string
         * @return      string
         */
        function valid_ip($ip)
        {
                $ip_segments = explode('.', $ip);

                // Always 4 segments needed
                if (count($ip_segments) != 4)
                {
                        return FALSE;
                }
                // IP can not start with 0
                if ($ip_segments[0][0] == '0')
                {
                        return FALSE;
                }
                // Check each segment
                foreach ($ip_segments as $segment)
                {
                        // IP segments must be digits and can not be 
                        // longer than 3 digits or greater then 255
                        if ($segment == '' OR preg_match("/[^0-9]/", $segment) OR $segment > 255 OR strlen($segment) > 3)
                        {
                                return FALSE;
                        }
                }

                return TRUE;
        }

        // --------------------------------------------------------------------

        /**
         * User Agent
         *
         * @access      public
         * @return      string
         */
        function user_agent()
        {
                if ($this->user_agent !== FALSE)
                {
                        return $this->user_agent;
                }

                $this->user_agent = ( ! isset($_SERVER['HTTP_USER_AGENT'])) ? FALSE : $_SERVER['HTTP_USER_AGENT'];

                return $this->user_agent;
        }

        // --------------------------------------------------------------------

        /**
         * Filename Security
         *
         * @access      public
         * @param       string
         * @return      string
         */
        function filename_security($str)
        {
                $bad = array(
                                                "../",
                                                "./",
                                                "<!--",
                                                "-->",
                                                "<",
                                                ">",
                                                "'",
                                                '"',
                                                '&',
                                                '$',
                                                '#',
                                                '{',
                                                '}',
                                                '[',
                                                ']',
                                                '=',
                                                ';',
                                                '?',
                                                "%20",
                                                "%22",
                                                "%3c",          // <
                                                "%253c",        // <
                                                "%3e",          // >
                                                "%0e",          // >
                                                "%28",          // (  
                                                "%29",          // ) 
                                                "%2528",        // (
                                                "%26",          // &
                                                "%24",          // $
                                                "%3f",          // ?
                                                "%3b",          // ;
                                                "%3d"           // =
                                        );

                return stripslashes(str_replace($bad, '', $str));
        }

        // --------------------------------------------------------------------

        /**
         * 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://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:
         * http://ha.ckers.org/xss.html
         *
         * @access      public
         * @param       string
         * @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;", $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, '_html_entity_decode_callback'), $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 = str_replace(array('<?php', '<?PHP'),  array('&lt;?php', '&lt;?PHP'), $str);
                }
                else
                {
                        $str = str_replace(array('<?php', '<?PHP', '<?', '?'.'>'),  array('&lt;?php', '&lt;?PHP', '&lt;?', '?&gt;'), $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: &lt;blink&gt;
                 *
                 */
                $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&#40;'some code'&#41;
                 *
                 */
                $str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2&#40;\\3&#41;", $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
                $str = '&lt;'.$matches[1].$matches[2].$matches[3];
                
                // encode captured opening or closing brace to prevent recursive vectors
                $str .= str_replace(array('>', '<'), array('&gt;', '&lt;'), $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('&gt;', '&lt;'), $match[0]);
        }

        // --------------------------------------------------------------------

        /**
         * HTML Entity Decode Callback
         *
         * Used as a callback for XSS Clean
         *
         * @access      public
         * @param       array
         * @return      string
         */
        function _html_entity_decode_callback($match)
        {
                $CFG =& load_class('Config');
                $charset = $CFG->item('charset');

                return $this->_html_entity_decode($match[0], strtoupper($charset));
        }

        // --------------------------------------------------------------------

        /**
         * HTML Entities Decode
         *
         * This function is a replacement for html_entity_decode()
         *
         * In some versions of PHP the native function does not work
         * when UTF-8 is the specified character set, so this gives us
         * a work-around.  More info here:
         * http://bugs.php.net/bug.php?id=25670
         *
         * @access      private
         * @param       string
         * @param       string
         * @return      string
         */
        /* -------------------------------------------------
        /*  Replacement for html_entity_decode()
        /* -------------------------------------------------*/

        /*
        NOTE: html_entity_decode() has a bug in some PHP versions when UTF-8 is the
        character set, and the PHP developers said they were not back porting the
        fix to versions other than PHP 5.x.
        */
        function _html_entity_decode($str, $charset='UTF-8')
        {
                if (stristr($str, '&') === FALSE) return $str;

                // 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.

                if (function_exists('html_entity_decode') && (strtolower($charset) != 'utf-8' OR version_compare(phpversion(), '5.0.0', '>=')))
                {
                        $str = html_entity_decode($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);
                }

                // Numeric Entities
                $str = preg_replace('~&#x(0*[0-9a-f]{2,5});{0,1}~ei', 'chr(hexdec("\\1"))', $str);
                $str = preg_replace('~&#([0-9]{2,4});{0,1}~e', 'chr(\\1)', $str);

                // Literal Entities - Slightly slow so we do another check
                if (stristr($str, '&') === FALSE)
                {
                        $str = strtr($str, array_flip(get_html_translation_table(HTML_ENTITIES)));
                }

                return $str;
        }

        // --------------------------------------------------------------------
        
        /**
         * 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)
                        {
                                $out .= "{$match}";
                        }                       
                }

                return $out;
        }

        // --------------------------------------------------------------------

}
// END Input class

/* End of file Input.php */
/* Location: ./system/libraries/Input.php */