root/trunk/system/libraries/Encrypt.php

<?php
/**
 * The Encrypt library provides two-way encryption of text and binary strings
 * using the MCrypt extension.
 * @see http://php.net/mcrypt
 *
 * $Id$
 *
 * @package    Core
 * @author     Kohana Team
 * @copyright  (c) 2007-2008 Kohana Team
 * @license    http://kohanaphp.com/license.html
 */
class Encrypt_Core {

    // OS-dependant RAND type to use
    protected static $rand;

    // Configuration
    protected $config;

    /**
     * Returns a singleton instance of Encrypt.
     *
     * @param   array  configuration options
     * @return  Encrypt_Core
     */
    public static function instance($config = NULL)
    {
        static $instance;

        // Create the singleton
        empty($instance) and $instance = new Encrypt((array) $config);

        return $instance;
    }

    /**
     * Loads encryption configuration and validates the data.
     *
     * @param   array|string      custom configuration or config group name
     * @throws  Kohana_Exception
     */
    public function __construct($config = FALSE)
    {
        if ( ! defined('MCRYPT_ENCRYPT'))
            throw new Kohana_Exception('encrypt.requires_mcrypt');

        if (is_string($config))
        {
            $name = $config;

            // Test the config group name
            if (($config = Kohana::config('encryption.'.$config)) === NULL)
                throw new Kohana_Exception('encrypt.undefined_group', $name);
        }

        if (is_array($config))
        {
            // Append the default configuration options
            $config += Kohana::config('encryption.default');
        }
        else
        {
            // Load the default group
            $config = Kohana::config('encryption.default');
        }

        if (empty($config['key']))
            throw new Kohana_Exception('encrypt.no_encryption_key');

        // Find the max length of the key, based on cipher and mode
        $size = mcrypt_get_key_size($config['cipher'], $config['mode']);

        if (strlen($config['key']) > $size)
        {
            // Shorten the key to the maximum size
            $config['key'] = substr($config['key'], 0, $size);
        }

        // Find the initialization vector size
        $config['iv_size'] = mcrypt_get_iv_size($config['cipher'], $config['mode']);

        // Cache the config in the object
        $this->config = $config;

        Kohana::log('debug', 'Encrypt Library initialized');
    }

    /**
     * Encrypts a string and returns an encrypted string that can be decoded.
     *
     * @param   string  data to be encrypted
     * @return  string  encrypted data
     */
    public function encode($data)
    {
        // Set the rand type if it has not already been set
        if (self::$rand === NULL)
        {
            if (KOHANA_IS_WIN)
            {
                // Windows only supports the system random number generator
                self::$rand = MCRYPT_RAND;
            }
            else
            {
                if (defined('MCRYPT_DEV_URANDOM'))
                {
                    // Use /dev/urandom
                    self::$rand = MCRYPT_DEV_URANDOM;
                }
                elseif (defined('MCRYPT_DEV_RANDOM'))
                {
                    // Use /dev/random
                    self::$rand = MCRYPT_DEV_RANDOM;
                }
                else
                {
                    // Use the system random number generator
                    self::$rand = MCRYPT_RAND;
                }
            }
        }

        if (self::$rand === MCRYPT_RAND)
        {
            // The system random number generator must always be seeded each
            // time it is used, or it will not produce true random results
            mt_srand();
        }

        // Create a random initialization vector of the proper size for the current cipher
        $iv = mcrypt_create_iv($this->config['iv_size'], self::$rand);

        // Encrypt the data using the configured options and generated iv
        $data = mcrypt_encrypt($this->config['cipher'], $this->config['key'], $data, $this->config['mode'], $iv);

        // Use base64 encoding to convert to a string
        return base64_encode($iv.$data);
    }

    /**
     * Decrypts an encoded string back to its original value.
     *
     * @param   string  encoded string to be decrypted
     * @return  string  decrypted data
     */
    public function decode($data)
    {
        // Convert the data back to binary
        $data = base64_decode($data);

        // Extract the initialization vector from the data
        $iv = substr($data, 0, $this->config['iv_size']);

        // Remove the iv from the data
        $data = substr($data, $this->config['iv_size']);

        // Return the decrypted data, trimming the \0 padding bytes from the end of the data
        return rtrim(mcrypt_decrypt($this->config['cipher'], $this->config['key'], $data, $this->config['mode'], $iv), "\0");
    }

} // End Encrypt