Encrypt.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
 */

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

/**
 * CodeIgniter Encryption Class
 *
 * Provides two-way keyed encoding using XOR Hashing and Mcrypt
 *
 * @package             CodeIgniter
 * @subpackage  Libraries
 * @category    Libraries
 * @author              ExpressionEngine Dev Team
 * @link                http://codeigniter.com/user_guide/libraries/encryption.html
 */
class CI_Encrypt {

        var $CI;
        var $encryption_key     = '';
        var $_hash_type = 'sha1';
        var $_mcrypt_exists = FALSE;
        var $_mcrypt_cipher;
        var $_mcrypt_mode;

        /**
         * Constructor
         *
         * Simply determines whether the mcrypt library exists.
         *
         */
        function CI_Encrypt()
        {
                $this->CI =& get_instance();
                $this->_mcrypt_exists = ( ! function_exists('mcrypt_encrypt')) ? FALSE : TRUE;
                log_message('debug', "Encrypt Class Initialized");
        }

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

        /**
         * Fetch the encryption key
         *
         * Returns it as MD5 in order to have an exact-length 128 bit key.
         * Mcrypt is sensitive to keys that are not the correct length
         *
         * @access      public
         * @param       string
         * @return      string
         */
        function get_key($key = '')
        {
                if ($key == '')
                {
                        if ($this->encryption_key != '')
                        {
                                return $this->encryption_key;
                        }

                        $CI =& get_instance();
                        $key = $CI->config->item('encryption_key');

                        if ($key === FALSE)
                        {
                                show_error('In order to use the encryption class requires that you set an encryption key in your config file.');
                        }
                }

                return md5($key);
        }

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

        /**
         * Set the encryption key
         *
         * @access      public
         * @param       string
         * @return      void
         */
        function set_key($key = '')
        {
                $this->encryption_key = $key;
        }

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

        /**
         * Encode
         *
         * Encodes the message string using bitwise XOR encoding.
         * The key is combined with a random hash, and then it
         * too gets converted using XOR. The whole thing is then run
         * through mcrypt (if supported) using the randomized key.
         * The end result is a double-encrypted message string
         * that is randomized with each call to this function,
         * even if the supplied message and key are the same.
         *
         * @access      public
         * @param       string  the string to encode
         * @param       string  the key
         * @return      string
         */
        function encode($string, $key = '')
        {
                $key = $this->get_key($key);
                $enc = $this->_xor_encode($string, $key);
                
                if ($this->_mcrypt_exists === TRUE)
                {
                        $enc = $this->mcrypt_encode($enc, $key);
                }
                return base64_encode($enc);
        }

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

        /**
         * Decode
         *
         * Reverses the above process
         *
         * @access      public
         * @param       string
         * @param       string
         * @return      string
         */
        function decode($string, $key = '')
        {
                $key = $this->get_key($key);
                
                if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))
                {
                        return FALSE;
                }

                $dec = base64_decode($string);

                if ($this->_mcrypt_exists === TRUE)
                {
                        if (($dec = $this->mcrypt_decode($dec, $key)) === FALSE)
                        {
                                return FALSE;
                        }
                }

                return $this->_xor_decode($dec, $key);
        }

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

        /**
         * XOR Encode
         *
         * Takes a plain-text string and key as input and generates an
         * encoded bit-string using XOR
         *
         * @access      private
         * @param       string
         * @param       string
         * @return      string
         */
        function _xor_encode($string, $key)
        {
                $rand = '';
                while (strlen($rand) < 32)
                {
                        $rand .= mt_rand(0, mt_getrandmax());
                }

                $rand = $this->hash($rand);

                $enc = '';
                for ($i = 0; $i < strlen($string); $i++)
                {                       
                        $enc .= substr($rand, ($i % strlen($rand)), 1).(substr($rand, ($i % strlen($rand)), 1) ^ substr($string, $i, 1));
                }

                return $this->_xor_merge($enc, $key);
        }

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

        /**
         * XOR Decode
         *
         * Takes an encoded string and key as input and generates the
         * plain-text original message
         *
         * @access      private
         * @param       string
         * @param       string
         * @return      string
         */
        function _xor_decode($string, $key)
        {
                $string = $this->_xor_merge($string, $key);

                $dec = '';
                for ($i = 0; $i < strlen($string); $i++)
                {
                        $dec .= (substr($string, $i++, 1) ^ substr($string, $i, 1));
                }

                return $dec;
        }

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

        /**
         * XOR key + string Combiner
         *
         * Takes a string and key as input and computes the difference using XOR
         *
         * @access      private
         * @param       string
         * @param       string
         * @return      string
         */
        function _xor_merge($string, $key)
        {
                $hash = $this->hash($key);
                $str = '';
                for ($i = 0; $i < strlen($string); $i++)
                {
                        $str .= substr($string, $i, 1) ^ substr($hash, ($i % strlen($hash)), 1);
                }

                return $str;
        }

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

        /**
         * Encrypt using Mcrypt
         *
         * @access      public
         * @param       string
         * @param       string
         * @return      string
         */
        function mcrypt_encode($data, $key)
        {
                $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());
                $init_vect = mcrypt_create_iv($init_size, MCRYPT_RAND);
                return $this->_add_cipher_noise($init_vect.mcrypt_encrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), $key);
        }

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

        /**
         * Decrypt using Mcrypt
         *
         * @access      public
         * @param       string
         * @param       string
         * @return      string
         */
        function mcrypt_decode($data, $key)
        {
                $data = $this->_remove_cipher_noise($data, $key);
                $init_size = mcrypt_get_iv_size($this->_get_cipher(), $this->_get_mode());

                if ($init_size > strlen($data))
                {
                        return FALSE;
                }

                $init_vect = substr($data, 0, $init_size);
                $data = substr($data, $init_size);
                return rtrim(mcrypt_decrypt($this->_get_cipher(), $key, $data, $this->_get_mode(), $init_vect), "\0");
        }

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

        /**
         * Adds permuted noise to the IV + encrypted data to protect
         * against Man-in-the-middle attacks on CBC mode ciphers
         * http://www.ciphersbyritter.com/GLOSSARY.HTM#IV
         *
         * Function description
         *
         * @access      private
         * @param       string
         * @param       string
         * @return      string
         */
        function _add_cipher_noise($data, $key)
        {
                $keyhash = $this->hash($key);
                $keylen = strlen($keyhash);
                $str = '';

                for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j)
                {
                        if ($j >= $keylen)
                        {
                                $j = 0;
                        }

                        $str .= chr((ord($data[$i]) + ord($keyhash[$j])) % 256);
                }

                return $str;
        }

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

        /**
         * Removes permuted noise from the IV + encrypted data, reversing
         * _add_cipher_noise()
         *
         * Function description
         *
         * @access      public
         * @param       type
         * @return      type
         */
        function _remove_cipher_noise($data, $key)
        {
                $keyhash = $this->hash($key);
                $keylen = strlen($keyhash);
                $str = '';

                for ($i = 0, $j = 0, $len = strlen($data); $i < $len; ++$i, ++$j)
                {
                        if ($j >= $keylen)
                        {
                                $j = 0;
                        }

                        $temp = ord($data[$i]) - ord($keyhash[$j]);

                        if ($temp < 0)
                        {
                                $temp = $temp + 256;
                        }
                        
                        $str .= chr($temp);
                }

                return $str;
        }

        // --------------------------------------------------------------------
        
        /**
         * Set the Mcrypt Cipher
         *
         * @access      public
         * @param       constant
         * @return      string
         */
        function set_cipher($cipher)
        {
                $this->_mcrypt_cipher = $cipher;
        }

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

        /**
         * Set the Mcrypt Mode
         *
         * @access      public
         * @param       constant
         * @return      string
         */
        function set_mode($mode)
        {
                $this->_mcrypt_mode = $mode;
        }

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

        /**
         * Get Mcrypt cipher Value
         *
         * @access      private
         * @return      string
         */
        function _get_cipher()
        {
                if ($this->_mcrypt_cipher == '')
                {
                        $this->_mcrypt_cipher = MCRYPT_RIJNDAEL_256;
                }

                return $this->_mcrypt_cipher;
        }

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

        /**
         * Get Mcrypt Mode Value
         *
         * @access      private
         * @return      string
         */
        function _get_mode()
        {
                if ($this->_mcrypt_mode == '')
                {
                        $this->_mcrypt_mode = MCRYPT_MODE_ECB;
                }
                
                return $this->_mcrypt_mode;
        }

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

        /**
         * Set the Hash type
         *
         * @access      public
         * @param       string
         * @return      string
         */
        function set_hash($type = 'sha1')
        {
                $this->_hash_type = ($type != 'sha1' AND $type != 'md5') ? 'sha1' : $type;
        }

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

        /**
         * Hash encode a string
         *
         * @access      public
         * @param       string
         * @return      string
         */     
        function hash($str)
        {
                return ($this->_hash_type == 'sha1') ? $this->sha1($str) : md5($str);
        }

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

        /**
         * Generate an SHA1 Hash
         *
         * @access      public
         * @param       string
         * @return      string
         */
        function sha1($str)
        {
                if ( ! function_exists('sha1'))
                {
                        if ( ! function_exists('mhash'))
                        {
                                require_once(BASEPATH.'libraries/Sha1'.EXT);
                                $SH = new CI_SHA;
                                return $SH->generate($str);
                        }
                        else
                        {
                                return bin2hex(mhash(MHASH_SHA1, $str));
                        }
                }
                else
                {
                        return sha1($str);
                }
        }

}

// END CI_Encrypt class

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