<?php defined('SYSPATH') OR die('No direct script access.');
/**
* The Encrypt library provides two-way encryption of text and binary strings
* using the [Mcrypt](http://php.net/mcrypt) extension, which consists of three
* parts: the key, the cipher, and the mode.
*
* The Key
* : A secret passphrase that is used for encoding and decoding
*
* The Cipher
* : A [cipher](http://php.net/mcrypt.ciphers) determines how the encryption
* is mathematically calculated. By default, the "rijndael-128" cipher
* is used. This is commonly known as "AES-128" and is an industry standard.
*
* The Mode
* : The [mode](http://php.net/mcrypt.constants) determines how the encrypted
* data is written in binary form. By default, the "nofb" mode is used,
* which produces short output with high entropy.
*
* @package Kohana
* @category Security
* @author Kohana Team
* @copyright (c) 2007-2012 Kohana Team
* @license http://kohanaframework.org/license
*/
class Kohana_Encrypt {
/**
* @var string default instance name
*/
public static $default = 'default';
/**
* @var array Encrypt class instances
*/
public static $instances = array();
/**
* @var string RAND type to use
*
* Only MCRYPT_DEV_URANDOM and MCRYPT_DEV_RANDOM are considered safe.
* Using MCRYPT_RAND will silently revert to MCRYPT_DEV_URANDOM
*/
protected static $_rand = MCRYPT_DEV_URANDOM;
/**
* @var string Encryption key
*/
protected $_key;
/**
* @var string mcrypt mode
*/
protected $_mode;
/**
* @var string mcrypt cipher
*/
protected $_cipher;
/**
* @var int the size of the Initialization Vector (IV) in bytes
*/
protected $_iv_size;
/**
* Returns a singleton instance of Encrypt. An encryption key must be
* provided in your "encrypt" configuration file.
*
* $encrypt = Encrypt::instance();
*
* @param string $name configuration group name
* @return Encrypt
*/
public static function instance($name = NULL)
{
if ($name === NULL)
{
// Use the default instance name
$name = Encrypt::$default;
}
if ( ! isset(Encrypt::$instances[$name]))
{
// Load the configuration data
$config = Kohana::$config->load('encrypt')->$name;
if ( ! isset($config['key']))
{
// No default encryption key is provided!
throw new Kohana_Exception('No encryption key is defined in the encryption configuration group: :group',
array(':group' => $name));
}
if ( ! isset($config['mode']))
{
// Add the default mode
$config['mode'] = MCRYPT_MODE_NOFB;
}
if ( ! isset($config['cipher']))
{
// Add the default cipher
$config['cipher'] = MCRYPT_RIJNDAEL_128;
}
// Create a new instance
Encrypt::$instances[$name] = new Encrypt($config['key'], $config['mode'], $config['cipher']);
}
return Encrypt::$instances[$name];
}
/**
* Creates a new mcrypt wrapper.
*
* @param string $key encryption key
* @param string $mode mcrypt mode
* @param string $cipher mcrypt cipher
*/
public function __construct($key, $mode, $cipher)
{
// Find the max length of the key, based on cipher and mode
$size = mcrypt_get_key_size($cipher, $mode);
if (isset($key[$size]))
{
// Shorten the key to the maximum size
$key = substr($key, 0, $size);
}
else if (version_compare(PHP_VERSION, '5.6.0', '>='))
{
$key = $this->_normalize_key($key, $cipher, $mode);
}
// Store the key, mode, and cipher
$this->_key = $key;
$this->_mode = $mode;
$this->_cipher = $cipher;
// Store the IV size
$this->_iv_size = mcrypt_get_iv_size($this->_cipher, $this->_mode);
}
/**
* Encrypts a string and returns an encrypted string that can be decoded.
*
* $data = $encrypt->encode($data);
*
* The encrypted binary data is encoded using [base64](http://php.net/base64_encode)
* to convert it to a string. This string can be stored in a database,
* displayed, and passed using most other means without corruption.
*
* @param string $data data to be encrypted
* @return string
*/
public function encode($data)
{
// Get an initialization vector
$iv = $this->_create_iv();
// Encrypt the data using the configured options and generated iv
$data = mcrypt_encrypt($this->_cipher, $this->_key, $data, $this->_mode, $iv);
// Use base64 encoding to convert to a string
return base64_encode($iv.$data);
}
/**
* Decrypts an encoded string back to its original value.
*
* $data = $encrypt->decode($data);
*
* @param string $data encoded string to be decrypted
* @return FALSE if decryption fails
* @return string
*/
public function decode($data)
{
// Convert the data back to binary
$data = base64_decode($data, TRUE);
if ( ! $data)
{
// Invalid base64 data
return FALSE;
}
// Extract the initialization vector from the data
$iv = substr($data, 0, $this->_iv_size);
if ($this->_iv_size !== strlen($iv))
{
// The iv is not the expected size
return FALSE;
}
// Remove the iv from the data
$data = substr($data, $this->_iv_size);
// Return the decrypted data, trimming the \0 padding bytes from the end of the data
return rtrim(mcrypt_decrypt($this->_cipher, $this->_key, $data, $this->_mode, $iv), "\0");
}
/**
* Proxy for the mcrypt_create_iv function - to allow mocking and testing against KAT vectors
*
* @return string the initialization vector or FALSE on error
*/
protected function _create_iv()
{
/*
* Silently use MCRYPT_DEV_URANDOM when the chosen random number generator
* is not one of those that are considered secure.
*
* Also sets Encrypt::$_rand to MCRYPT_DEV_URANDOM when it's not already set
*/
if ((Encrypt::$_rand !== MCRYPT_DEV_URANDOM) AND ( Encrypt::$_rand !== MCRYPT_DEV_RANDOM))
{
Encrypt::$_rand = MCRYPT_DEV_URANDOM;
}
// Create a random initialization vector of the proper size for the current cipher
return mcrypt_create_iv($this->_iv_size, Encrypt::$_rand);
}
/**
* Normalize key for PHP 5.6 for backwards compatibility
*
* This method is a shim to make PHP 5.6 behave in a B/C way for
* legacy key padding when shorter-than-supported keys are used
*
* @param string $key encryption key
* @param string $cipher mcrypt cipher
* @param string $mode mcrypt mode
*/
protected function _normalize_key($key, $cipher, $mode)
{
// open the cipher
$td = mcrypt_module_open($cipher, '', $mode, '');
// loop through the supported key sizes
foreach (mcrypt_enc_get_supported_key_sizes($td) as $supported) {
// if key is short, needs padding
if (strlen($key) <= $supported)
{
return str_pad($key, $supported, "\0");
}
}
// at this point key must be greater than max supported size, shorten it
return substr($key, 0, mcrypt_get_key_size($cipher, $mode));
}
}