<?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

 */



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



/**

 * 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.

	 *

	 */

	public function __construct()

	{

		$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);



		if ($this->_mcrypt_exists === TRUE)

		{

			$enc = $this->mcrypt_encode($string, $key);

		}

		else

		{

			$enc = $this->_xor_encode($string, $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;

			}

		}

		else

		{

			$dec = $this->_xor_decode($dec, $key);

		}



		return $dec;

	}



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



	/**

	 * Encode from Legacy

	 *

	 * Takes an encoded string from the original Encryption class algorithms and

	 * returns a newly encoded string using the improved method added in 2.0.0

	 * This allows for backwards compatibility and a method to transition to the

	 * new encryption algorithms.

	 *

	 * For more details, see http://codeigniter.com/user_guide/installation/upgrade_200.html#encryption

	 *

	 * @access	public

	 * @param	string

	 * @param	int		(mcrypt mode constant)

	 * @param	string

	 * @return	string

	 */

	function encode_from_legacy($string, $legacy_mode = MCRYPT_MODE_ECB, $key = '')

	{

		if ($this->_mcrypt_exists === FALSE)

		{

			log_message('error', 'Encoding from legacy is available only when Mcrypt is in use.');

			return FALSE;

		}



		// decode it first

		// set mode temporarily to what it was when string was encoded with the legacy

		// algorithm - typically MCRYPT_MODE_ECB

		$current_mode = $this->_get_mode();

		$this->set_mode($legacy_mode);



		$key = $this->get_key($key);



		if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))

		{

			return FALSE;

		}



		$dec = base64_decode($string);



		if (($dec = $this->mcrypt_decode($dec, $key)) === FALSE)

		{

			return FALSE;

		}



		$dec = $this->_xor_decode($dec, $key);



		// set the mcrypt mode back to what it should be, typically MCRYPT_MODE_CBC

		$this->set_mode($current_mode);



		// and re-encode

		return base64_encode($this->mcrypt_encode($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_CBC;

		}



		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.php');

				$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 */