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<?php

/**

 * CodeIgniter

 *

 * An open source application development framework for PHP

 *

 * This content is released under the MIT License (MIT)

 *

 * Copyright (c) 2014 - 2016, British Columbia Institute of Technology

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 *

 * @package	CodeIgniter

 * @author	EllisLab Dev Team

 * @copyright	Copyright (c) 2008 - 2014, EllisLab, Inc. (https://ellislab.com/)

 * @copyright	Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)

 * @license	http://opensource.org/licenses/MIT	MIT License

 * @link	https://codeigniter.com

 * @since	Version 1.0.0

 * @filesource

 */

defined('BASEPATH') OR exit('No direct script access allowed');

/**

 * CodeIgniter Encryption Class

 *

 * Provides two-way keyed encoding using Mcrypt

 *

 * @package		CodeIgniter

 * @subpackage	Libraries

 * @category	Libraries

 * @author		EllisLab Dev Team

 * @link		https://codeigniter.com/user_guide/libraries/encryption.html

 */

class CI_Encrypt {

	/**

	 * Reference to the user's encryption key

	 *

	 * @var string

	 */

	public $encryption_key		= '';

	/**

	 * Type of hash operation

	 *

	 * @var string

	 */

	protected $_hash_type		= 'sha1';

	/**

	 * Flag for the existence of mcrypt

	 *

	 * @var bool

	 */

	protected $_mcrypt_exists	= FALSE;

	/**

	 * Current cipher to be used with mcrypt

	 *

	 * @var string

	 */

	protected $_mcrypt_cipher;

	/**

	 * Method for encrypting/decrypting data

	 *

	 * @var int

	 */

	protected $_mcrypt_mode;

	/**

	 * Initialize Encryption class

	 *

	 * @return	void

	 */

	public function __construct()

	{

		if (($this->_mcrypt_exists = function_exists('mcrypt_encrypt')) === FALSE)

		{

			show_error('The Encrypt library requires the Mcrypt extension.');

		}

		log_message('info', '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

	 *

	 * @param	string

	 * @return	string

	 */

	public function get_key($key = '')

	{

		if ($key === '')

		{

			if ($this->encryption_key !== '')

			{

				return $this->encryption_key;

			}

			$key = config_item('encryption_key');

			if ( ! strlen($key))

			{

				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

	 *

	 * @param	string

	 * @return	CI_Encrypt

	 */

	public function set_key($key = '')

	{

		$this->encryption_key = $key;

		return $this;

	}

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

	/**

	 * 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 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.

	 *

	 * @param	string	the string to encode

	 * @param	string	the key

	 * @return	string

	 */

	public function encode($string, $key = '')

	{

		return base64_encode($this->mcrypt_encode($string, $this->get_key($key)));

	}

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

	/**

	 * Decode

	 *

	 * Reverses the above process

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	public function decode($string, $key = '')

	{

		if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string) OR base64_encode(base64_decode($string)) !== $string)

		{

			return FALSE;

		}

		return $this->mcrypt_decode(base64_decode($string), $this->get_key($key));

	}

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

	/**

	 * 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 https://codeigniter.com/user_guide/installation/upgrade_200.html#encryption

	 *

	 * @param	string

	 * @param	int		(mcrypt mode constant)

	 * @param	string

	 * @return	string

	 */

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

	{

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

		{

			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);

		$dec = base64_decode($string);

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

		{

			$this->set_mode($current_mode);

			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 Decode

	 *

	 * Takes an encoded string and key as input and generates the

	 * plain-text original message

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	protected function _xor_decode($string, $key)

	{

		$string = $this->_xor_merge($string, $key);

		$dec = '';

		for ($i = 0, $l = strlen($string); $i < $l; $i++)

		{

			$dec .= ($string[$i++] ^ $string[$i]);

		}

		return $dec;

	}

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

	/**

	 * XOR key + string Combiner

	 *

	 * Takes a string and key as input and computes the difference using XOR

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	protected function _xor_merge($string, $key)

	{

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

		$str = '';

		for ($i = 0, $ls = strlen($string), $lh = strlen($hash); $i < $ls; $i++)

		{

			$str .= $string[$i] ^ $hash[($i % $lh)];

		}

		return $str;

	}

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

	/**

	 * Encrypt using Mcrypt

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	public 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

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	public 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

	 *

	 * @param	string

	 * @param	string

	 * @return	string

	 */

	protected function _add_cipher_noise($data, $key)

	{

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

		$str = '';

		for ($i = 0, $j = 0, $ld = strlen($data), $lk = strlen($key); $i < $ld; ++$i, ++$j)

		{

			if ($j >= $lk)

			{

				$j = 0;

			}

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

		}

		return $str;

	}

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

	/**

	 * Removes permuted noise from the IV + encrypted data, reversing

	 * _add_cipher_noise()

	 *

	 * Function description

	 *

	 * @param	string	$data

	 * @param	string	$key

	 * @return	string

	 */

	protected function _remove_cipher_noise($data, $key)

	{

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

		$str = '';

		for ($i = 0, $j = 0, $ld = strlen($data), $lk = strlen($key); $i < $ld; ++$i, ++$j)

		{

			if ($j >= $lk)

			{

				$j = 0;

			}

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

			if ($temp < 0)

			{

				$temp += 256;

			}

			$str .= chr($temp);

		}

		return $str;

	}

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

	/**

	 * Set the Mcrypt Cipher

	 *

	 * @param	int

	 * @return	CI_Encrypt

	 */

	public function set_cipher($cipher)

	{

		$this->_mcrypt_cipher = $cipher;

		return $this;

	}

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

	/**

	 * Set the Mcrypt Mode

	 *

	 * @param	int

	 * @return	CI_Encrypt

	 */

	public function set_mode($mode)

	{

		$this->_mcrypt_mode = $mode;

		return $this;

	}

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

	/**

	 * Get Mcrypt cipher Value

	 *

	 * @return	int

	 */

	protected function _get_cipher()

	{

		if ($this->_mcrypt_cipher === NULL)

		{

			return $this->_mcrypt_cipher = MCRYPT_RIJNDAEL_256;

		}

		return $this->_mcrypt_cipher;

	}

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

	/**

	 * Get Mcrypt Mode Value

	 *

	 * @return	int

	 */

	protected function _get_mode()

	{

		if ($this->_mcrypt_mode === NULL)

		{

			return $this->_mcrypt_mode = MCRYPT_MODE_CBC;

		}

		return $this->_mcrypt_mode;

	}

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

	/**

	 * Set the Hash type

	 *

	 * @param	string

	 * @return	void

	 */

	public function set_hash($type = 'sha1')

	{

		$this->_hash_type = in_array($type, hash_algos()) ? $type : 'sha1';

	}

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

	/**

	 * Hash encode a string

	 *

	 * @param	string

	 * @return	string

	 */

	public function hash($str)

	{

		return hash($this->_hash_type, $str);

	}

}