Merge tag '3.1.5' into dev-ci3

Signed-off-by: Florian Pritz <bluewind@xinu.at>

1 files changed, 943 insertions, 0 deletions

diff --git a/system/libraries/Encryption.php b/system/libraries/Encryption.php
new file mode 100644
index 000000000..c1e454dda
--- /dev/null
+++ b/system/libraries/Encryption.php
@@ -0,0 +1,943 @@
+<?php
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP
+ *
+ * This content is released under the MIT License (MIT)
+ *
+ * Copyright (c) 2014 - 2017, 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 - 2017, British Columbia Institute of Technology (http://bcit.ca/)
+ * @license	http://opensource.org/licenses/MIT	MIT License
+ * @link	https://codeigniter.com
+ * @since	Version 3.0.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * CodeIgniter Encryption Class
+ *
+ * Provides two-way keyed encryption via PHP's MCrypt and/or OpenSSL extensions.
+ *
+ * @package		CodeIgniter
+ * @subpackage	Libraries
+ * @category	Libraries
+ * @author		Andrey Andreev
+ * @link		https://codeigniter.com/user_guide/libraries/encryption.html
+ */
+class CI_Encryption {
+
+	/**
+	 * Encryption cipher
+	 *
+	 * @var	string
+	 */
+	protected $_cipher = 'aes-128';
+
+	/**
+	 * Cipher mode
+	 *
+	 * @var	string
+	 */
+	protected $_mode = 'cbc';
+
+	/**
+	 * Cipher handle
+	 *
+	 * @var	mixed
+	 */
+	protected $_handle;
+
+	/**
+	 * Encryption key
+	 *
+	 * @var	string
+	 */
+	protected $_key;
+
+	/**
+	 * PHP extension to be used
+	 *
+	 * @var	string
+	 */
+	protected $_driver;
+
+	/**
+	 * List of usable drivers (PHP extensions)
+	 *
+	 * @var	array
+	 */
+	protected $_drivers = array();
+
+	/**
+	 * List of available modes
+	 *
+	 * @var	array
+	 */
+	protected $_modes = array(
+		'mcrypt' => array(
+			'cbc' => 'cbc',
+			'ecb' => 'ecb',
+			'ofb' => 'nofb',
+			'ofb8' => 'ofb',
+			'cfb' => 'ncfb',
+			'cfb8' => 'cfb',
+			'ctr' => 'ctr',
+			'stream' => 'stream'
+		),
+		'openssl' => array(
+			'cbc' => 'cbc',
+			'ecb' => 'ecb',
+			'ofb' => 'ofb',
+			'cfb' => 'cfb',
+			'cfb8' => 'cfb8',
+			'ctr' => 'ctr',
+			'stream' => '',
+			'xts' => 'xts'
+		)
+	);
+
+	/**
+	 * List of supported HMAC algorithms
+	 *
+	 * name => digest size pairs
+	 *
+	 * @var	array
+	 */
+	protected $_digests = array(
+		'sha224' => 28,
+		'sha256' => 32,
+		'sha384' => 48,
+		'sha512' => 64
+	);
+
+	/**
+	 * mbstring.func_overload flag
+	 *
+	 * @var	bool
+	 */
+	protected static $func_overload;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Class constructor
+	 *
+	 * @param	array	$params	Configuration parameters
+	 * @return	void
+	 */
+	public function __construct(array $params = array())
+	{
+		$this->_drivers = array(
+			'mcrypt'  => defined('MCRYPT_DEV_URANDOM'),
+			'openssl' => extension_loaded('openssl')
+		);
+
+		if ( ! $this->_drivers['mcrypt'] && ! $this->_drivers['openssl'])
+		{
+			show_error('Encryption: Unable to find an available encryption driver.');
+		}
+
+		isset(self::$func_overload) OR self::$func_overload = (extension_loaded('mbstring') && ini_get('mbstring.func_overload'));
+		$this->initialize($params);
+
+		if ( ! isset($this->_key) && self::strlen($key = config_item('encryption_key')) > 0)
+		{
+			$this->_key = $key;
+		}
+
+		log_message('info', 'Encryption Class Initialized');
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Initialize
+	 *
+	 * @param	array	$params	Configuration parameters
+	 * @return	CI_Encryption
+	 */
+	public function initialize(array $params)
+	{
+		if ( ! empty($params['driver']))
+		{
+			if (isset($this->_drivers[$params['driver']]))
+			{
+				if ($this->_drivers[$params['driver']])
+				{
+					$this->_driver = $params['driver'];
+				}
+				else
+				{
+					log_message('error', "Encryption: Driver '".$params['driver']."' is not available.");
+				}
+			}
+			else
+			{
+				log_message('error', "Encryption: Unknown driver '".$params['driver']."' cannot be configured.");
+			}
+		}
+
+		if (empty($this->_driver))
+		{
+			$this->_driver = ($this->_drivers['openssl'] === TRUE)
+				? 'openssl'
+				: 'mcrypt';
+
+			log_message('debug', "Encryption: Auto-configured driver '".$this->_driver."'.");
+		}
+
+		empty($params['cipher']) && $params['cipher'] = $this->_cipher;
+		empty($params['key']) OR $this->_key = $params['key'];
+		$this->{'_'.$this->_driver.'_initialize'}($params);
+		return $this;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Initialize MCrypt
+	 *
+	 * @param	array	$params	Configuration parameters
+	 * @return	void
+	 */
+	protected function _mcrypt_initialize($params)
+	{
+		if ( ! empty($params['cipher']))
+		{
+			$params['cipher'] = strtolower($params['cipher']);
+			$this->_cipher_alias($params['cipher']);
+
+			if ( ! in_array($params['cipher'], mcrypt_list_algorithms(), TRUE))
+			{
+				log_message('error', 'Encryption: MCrypt cipher '.strtoupper($params['cipher']).' is not available.');
+			}
+			else
+			{
+				$this->_cipher = $params['cipher'];
+			}
+		}
+
+		if ( ! empty($params['mode']))
+		{
+			$params['mode'] = strtolower($params['mode']);
+			if ( ! isset($this->_modes['mcrypt'][$params['mode']]))
+			{
+				log_message('error', 'Encryption: MCrypt mode '.strtoupper($params['mode']).' is not available.');
+			}
+			else
+			{
+				$this->_mode = $this->_modes['mcrypt'][$params['mode']];
+			}
+		}
+
+		if (isset($this->_cipher, $this->_mode))
+		{
+			if (is_resource($this->_handle)
+				&& (strtolower(mcrypt_enc_get_algorithms_name($this->_handle)) !== $this->_cipher
+					OR strtolower(mcrypt_enc_get_modes_name($this->_handle)) !== $this->_mode)
+			)
+			{
+				mcrypt_module_close($this->_handle);
+			}
+
+			if ($this->_handle = mcrypt_module_open($this->_cipher, '', $this->_mode, ''))
+			{
+				log_message('info', 'Encryption: MCrypt cipher '.strtoupper($this->_cipher).' initialized in '.strtoupper($this->_mode).' mode.');
+			}
+			else
+			{
+				log_message('error', 'Encryption: Unable to initialize MCrypt with cipher '.strtoupper($this->_cipher).' in '.strtoupper($this->_mode).' mode.');
+			}
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Initialize OpenSSL
+	 *
+	 * @param	array	$params	Configuration parameters
+	 * @return	void
+	 */
+	protected function _openssl_initialize($params)
+	{
+		if ( ! empty($params['cipher']))
+		{
+			$params['cipher'] = strtolower($params['cipher']);
+			$this->_cipher_alias($params['cipher']);
+			$this->_cipher = $params['cipher'];
+		}
+
+		if ( ! empty($params['mode']))
+		{
+			$params['mode'] = strtolower($params['mode']);
+			if ( ! isset($this->_modes['openssl'][$params['mode']]))
+			{
+				log_message('error', 'Encryption: OpenSSL mode '.strtoupper($params['mode']).' is not available.');
+			}
+			else
+			{
+				$this->_mode = $this->_modes['openssl'][$params['mode']];
+			}
+		}
+
+		if (isset($this->_cipher, $this->_mode))
+		{
+			// This is mostly for the stream mode, which doesn't get suffixed in OpenSSL
+			$handle = empty($this->_mode)
+				? $this->_cipher
+				: $this->_cipher.'-'.$this->_mode;
+
+			if ( ! in_array($handle, openssl_get_cipher_methods(), TRUE))
+			{
+				$this->_handle = NULL;
+				log_message('error', 'Encryption: Unable to initialize OpenSSL with method '.strtoupper($handle).'.');
+			}
+			else
+			{
+				$this->_handle = $handle;
+				log_message('info', 'Encryption: OpenSSL initialized with method '.strtoupper($handle).'.');
+			}
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Create a random key
+	 *
+	 * @param	int	$length	Output length
+	 * @return	string
+	 */
+	public function create_key($length)
+	{
+		if (function_exists('random_bytes'))
+		{
+			try
+			{
+				return random_bytes((int) $length);
+			}
+			catch (Exception $e)
+			{
+				log_message('error', $e->getMessage());
+				return FALSE;
+			}
+		}
+		elseif (defined('MCRYPT_DEV_URANDOM'))
+		{
+			return mcrypt_create_iv($length, MCRYPT_DEV_URANDOM);
+		}
+
+		$is_secure = NULL;
+		$key = openssl_random_pseudo_bytes($length, $is_secure);
+		return ($is_secure === TRUE)
+			? $key
+			: FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Encrypt
+	 *
+	 * @param	string	$data	Input data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	public function encrypt($data, array $params = NULL)
+	{
+		if (($params = $this->_get_params($params)) === FALSE)
+		{
+			return FALSE;
+		}
+
+		isset($params['key']) OR $params['key'] = $this->hkdf($this->_key, 'sha512', NULL, self::strlen($this->_key), 'encryption');
+
+		if (($data = $this->{'_'.$this->_driver.'_encrypt'}($data, $params)) === FALSE)
+		{
+			return FALSE;
+		}
+
+		$params['base64'] && $data = base64_encode($data);
+
+		if (isset($params['hmac_digest']))
+		{
+			isset($params['hmac_key']) OR $params['hmac_key'] = $this->hkdf($this->_key, 'sha512', NULL, NULL, 'authentication');
+			return hash_hmac($params['hmac_digest'], $data, $params['hmac_key'], ! $params['base64']).$data;
+		}
+
+		return $data;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Encrypt via MCrypt
+	 *
+	 * @param	string	$data	Input data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	protected function _mcrypt_encrypt($data, $params)
+	{
+		if ( ! is_resource($params['handle']))
+		{
+			return FALSE;
+		}
+
+		// The greater-than-1 comparison is mostly a work-around for a bug,
+		// where 1 is returned for ARCFour instead of 0.
+		$iv = (($iv_size = mcrypt_enc_get_iv_size($params['handle'])) > 1)
+			? $this->create_key($iv_size)
+			: NULL;
+
+		if (mcrypt_generic_init($params['handle'], $params['key'], $iv) < 0)
+		{
+			if ($params['handle'] !== $this->_handle)
+			{
+				mcrypt_module_close($params['handle']);
+			}
+
+			return FALSE;
+		}
+
+		// Use PKCS#7 padding in order to ensure compatibility with OpenSSL
+		// and other implementations outside of PHP.
+		if (in_array(strtolower(mcrypt_enc_get_modes_name($params['handle'])), array('cbc', 'ecb'), TRUE))
+		{
+			$block_size = mcrypt_enc_get_block_size($params['handle']);
+			$pad = $block_size - (self::strlen($data) % $block_size);
+			$data .= str_repeat(chr($pad), $pad);
+		}
+
+		// Work-around for yet another strange behavior in MCrypt.
+		//
+		// When encrypting in ECB mode, the IV is ignored. Yet
+		// mcrypt_enc_get_iv_size() returns a value larger than 0
+		// even if ECB is used AND mcrypt_generic_init() complains
+		// if you don't pass an IV with length equal to the said
+		// return value.
+		//
+		// This probably would've been fine (even though still wasteful),
+		// but OpenSSL isn't that dumb and we need to make the process
+		// portable, so ...
+		$data = (mcrypt_enc_get_modes_name($params['handle']) !== 'ECB')
+			? $iv.mcrypt_generic($params['handle'], $data)
+			: mcrypt_generic($params['handle'], $data);
+
+		mcrypt_generic_deinit($params['handle']);
+		if ($params['handle'] !== $this->_handle)
+		{
+			mcrypt_module_close($params['handle']);
+		}
+
+		return $data;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Encrypt via OpenSSL
+	 *
+	 * @param	string	$data	Input data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	protected function _openssl_encrypt($data, $params)
+	{
+		if (empty($params['handle']))
+		{
+			return FALSE;
+		}
+
+		$iv = ($iv_size = openssl_cipher_iv_length($params['handle']))
+			? $this->create_key($iv_size)
+			: NULL;
+
+		$data = openssl_encrypt(
+			$data,
+			$params['handle'],
+			$params['key'],
+			1, // DO NOT TOUCH!
+			$iv
+		);
+
+		if ($data === FALSE)
+		{
+			return FALSE;
+		}
+
+		return $iv.$data;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Decrypt
+	 *
+	 * @param	string	$data	Encrypted data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	public function decrypt($data, array $params = NULL)
+	{
+		if (($params = $this->_get_params($params)) === FALSE)
+		{
+			return FALSE;
+		}
+
+		if (isset($params['hmac_digest']))
+		{
+			// This might look illogical, but it is done during encryption as well ...
+			// The 'base64' value is effectively an inverted "raw data" parameter
+			$digest_size = ($params['base64'])
+				? $this->_digests[$params['hmac_digest']] * 2
+				: $this->_digests[$params['hmac_digest']];
+
+			if (self::strlen($data) <= $digest_size)
+			{
+				return FALSE;
+			}
+
+			$hmac_input = self::substr($data, 0, $digest_size);
+			$data = self::substr($data, $digest_size);
+
+			isset($params['hmac_key']) OR $params['hmac_key'] = $this->hkdf($this->_key, 'sha512', NULL, NULL, 'authentication');
+			$hmac_check = hash_hmac($params['hmac_digest'], $data, $params['hmac_key'], ! $params['base64']);
+
+			// Time-attack-safe comparison
+			$diff = 0;
+			for ($i = 0; $i < $digest_size; $i++)
+			{
+				$diff |= ord($hmac_input[$i]) ^ ord($hmac_check[$i]);
+			}
+
+			if ($diff !== 0)
+			{
+				return FALSE;
+			}
+		}
+
+		if ($params['base64'])
+		{
+			$data = base64_decode($data);
+		}
+
+		isset($params['key']) OR $params['key'] = $this->hkdf($this->_key, 'sha512', NULL, self::strlen($this->_key), 'encryption');
+
+		return $this->{'_'.$this->_driver.'_decrypt'}($data, $params);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Decrypt via MCrypt
+	 *
+	 * @param	string	$data	Encrypted data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	protected function _mcrypt_decrypt($data, $params)
+	{
+		if ( ! is_resource($params['handle']))
+		{
+			return FALSE;
+		}
+
+		// The greater-than-1 comparison is mostly a work-around for a bug,
+		// where 1 is returned for ARCFour instead of 0.
+		if (($iv_size = mcrypt_enc_get_iv_size($params['handle'])) > 1)
+		{
+			if (mcrypt_enc_get_modes_name($params['handle']) !== 'ECB')
+			{
+				$iv = self::substr($data, 0, $iv_size);
+				$data = self::substr($data, $iv_size);
+			}
+			else
+			{
+				// MCrypt is dumb and this is ignored, only size matters
+				$iv = str_repeat("\x0", $iv_size);
+			}
+		}
+		else
+		{
+			$iv = NULL;
+		}
+
+		if (mcrypt_generic_init($params['handle'], $params['key'], $iv) < 0)
+		{
+			if ($params['handle'] !== $this->_handle)
+			{
+				mcrypt_module_close($params['handle']);
+			}
+
+			return FALSE;
+		}
+
+		$data = mdecrypt_generic($params['handle'], $data);
+		// Remove PKCS#7 padding, if necessary
+		if (in_array(strtolower(mcrypt_enc_get_modes_name($params['handle'])), array('cbc', 'ecb'), TRUE))
+		{
+			$data = self::substr($data, 0, -ord($data[self::strlen($data)-1]));
+		}
+
+		mcrypt_generic_deinit($params['handle']);
+		if ($params['handle'] !== $this->_handle)
+		{
+			mcrypt_module_close($params['handle']);
+		}
+
+		return $data;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Decrypt via OpenSSL
+	 *
+	 * @param	string	$data	Encrypted data
+	 * @param	array	$params	Input parameters
+	 * @return	string
+	 */
+	protected function _openssl_decrypt($data, $params)
+	{
+		if ($iv_size = openssl_cipher_iv_length($params['handle']))
+		{
+			$iv = self::substr($data, 0, $iv_size);
+			$data = self::substr($data, $iv_size);
+		}
+		else
+		{
+			$iv = NULL;
+		}
+
+		return empty($params['handle'])
+			? FALSE
+			: openssl_decrypt(
+				$data,
+				$params['handle'],
+				$params['key'],
+				1, // DO NOT TOUCH!
+				$iv
+			);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Get params
+	 *
+	 * @param	array	$params	Input parameters
+	 * @return	array
+	 */
+	protected function _get_params($params)
+	{
+		if (empty($params))
+		{
+			return isset($this->_cipher, $this->_mode, $this->_key, $this->_handle)
+				? array(
+					'handle' => $this->_handle,
+					'cipher' => $this->_cipher,
+					'mode' => $this->_mode,
+					'key' => NULL,
+					'base64' => TRUE,
+					'hmac_digest' => 'sha512',
+					'hmac_key' => NULL
+				)
+				: FALSE;
+		}
+		elseif ( ! isset($params['cipher'], $params['mode'], $params['key']))
+		{
+			return FALSE;
+		}
+
+		if (isset($params['mode']))
+		{
+			$params['mode'] = strtolower($params['mode']);
+			if ( ! isset($this->_modes[$this->_driver][$params['mode']]))
+			{
+				return FALSE;
+			}
+			else
+			{
+				$params['mode'] = $this->_modes[$this->_driver][$params['mode']];
+			}
+		}
+
+		if (isset($params['hmac']) && $params['hmac'] === FALSE)
+		{
+			$params['hmac_digest'] = $params['hmac_key'] = NULL;
+		}
+		else
+		{
+			if ( ! isset($params['hmac_key']))
+			{
+				return FALSE;
+			}
+			elseif (isset($params['hmac_digest']))
+			{
+				$params['hmac_digest'] = strtolower($params['hmac_digest']);
+				if ( ! isset($this->_digests[$params['hmac_digest']]))
+				{
+					return FALSE;
+				}
+			}
+			else
+			{
+				$params['hmac_digest'] = 'sha512';
+			}
+		}
+
+		$params = array(
+			'handle' => NULL,
+			'cipher' => $params['cipher'],
+			'mode' => $params['mode'],
+			'key' => $params['key'],
+			'base64' => isset($params['raw_data']) ? ! $params['raw_data'] : FALSE,
+			'hmac_digest' => $params['hmac_digest'],
+			'hmac_key' => $params['hmac_key']
+		);
+
+		$this->_cipher_alias($params['cipher']);
+		$params['handle'] = ($params['cipher'] !== $this->_cipher OR $params['mode'] !== $this->_mode)
+			? $this->{'_'.$this->_driver.'_get_handle'}($params['cipher'], $params['mode'])
+			: $this->_handle;
+
+		return $params;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Get MCrypt handle
+	 *
+	 * @param	string	$cipher	Cipher name
+	 * @param	string	$mode	Encryption mode
+	 * @return	resource
+	 */
+	protected function _mcrypt_get_handle($cipher, $mode)
+	{
+		return mcrypt_module_open($cipher, '', $mode, '');
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Get OpenSSL handle
+	 *
+	 * @param	string	$cipher	Cipher name
+	 * @param	string	$mode	Encryption mode
+	 * @return	string
+	 */
+	protected function _openssl_get_handle($cipher, $mode)
+	{
+		// OpenSSL methods aren't suffixed with '-stream' for this mode
+		return ($mode === 'stream')
+			? $cipher
+			: $cipher.'-'.$mode;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Cipher alias
+	 *
+	 * Tries to translate cipher names between MCrypt and OpenSSL's "dialects".
+	 *
+	 * @param	string	$cipher	Cipher name
+	 * @return	void
+	 */
+	protected function _cipher_alias(&$cipher)
+	{
+		static $dictionary;
+
+		if (empty($dictionary))
+		{
+			$dictionary = array(
+				'mcrypt' => array(
+					'aes-128' => 'rijndael-128',
+					'aes-192' => 'rijndael-128',
+					'aes-256' => 'rijndael-128',
+					'des3-ede3' => 'tripledes',
+					'bf' => 'blowfish',
+					'cast5' => 'cast-128',
+					'rc4' => 'arcfour',
+					'rc4-40' => 'arcfour'
+				),
+				'openssl' => array(
+					'rijndael-128' => 'aes-128',
+					'tripledes' => 'des-ede3',
+					'blowfish' => 'bf',
+					'cast-128' => 'cast5',
+					'arcfour' => 'rc4-40',
+					'rc4' => 'rc4-40'
+				)
+			);
+
+			// Notes:
+			//
+			// - Rijndael-128 is, at the same time all three of AES-128,
+			//   AES-192 and AES-256. The only difference between them is
+			//   the key size. Rijndael-192, Rijndael-256 on the other hand
+			//   also have different block sizes and are NOT AES-compatible.
+			//
+			// - Blowfish is said to be supporting key sizes between
+			//   4 and 56 bytes, but it appears that between MCrypt and
+			//   OpenSSL, only those of 16 and more bytes are compatible.
+			//   Also, don't know what MCrypt's 'blowfish-compat' is.
+			//
+			// - CAST-128/CAST5 produces a longer cipher when encrypted via
+			//   OpenSSL, but (strangely enough) can be decrypted by either
+			//   extension anyway.
+			//   Also, it appears that OpenSSL uses 16 rounds regardless of
+			//   the key size, while RFC2144 says that for key sizes lower
+			//   than 11 bytes, only 12 rounds should be used. This makes
+			//   it portable only with keys of between 11 and 16 bytes.
+			//
+			// - RC4 (ARCFour) has a strange implementation under OpenSSL.
+			//   Its 'rc4-40' cipher method seems to work flawlessly, yet
+			//   there's another one, 'rc4' that only works with a 16-byte key.
+			//
+			// - DES is compatible, but doesn't need an alias.
+			//
+			// Other seemingly matching ciphers between MCrypt, OpenSSL:
+			//
+			// - RC2 is NOT compatible and only an obscure forum post
+			//   confirms that it is MCrypt's fault.
+		}
+
+		if (isset($dictionary[$this->_driver][$cipher]))
+		{
+			$cipher = $dictionary[$this->_driver][$cipher];
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * HKDF
+	 *
+	 * @link	https://tools.ietf.org/rfc/rfc5869.txt
+	 * @param	$key	Input key
+	 * @param	$digest	A SHA-2 hashing algorithm
+	 * @param	$salt	Optional salt
+	 * @param	$length	Output length (defaults to the selected digest size)
+	 * @param	$info	Optional context/application-specific info
+	 * @return	string	A pseudo-random key
+	 */
+	public function hkdf($key, $digest = 'sha512', $salt = NULL, $length = NULL, $info = '')
+	{
+		if ( ! isset($this->_digests[$digest]))
+		{
+			return FALSE;
+		}
+
+		if (empty($length) OR ! is_int($length))
+		{
+			$length = $this->_digests[$digest];
+		}
+		elseif ($length > (255 * $this->_digests[$digest]))
+		{
+			return FALSE;
+		}
+
+		self::strlen($salt) OR $salt = str_repeat("\0", $this->_digests[$digest]);
+
+		$prk = hash_hmac($digest, $key, $salt, TRUE);
+		$key = '';
+		for ($key_block = '', $block_index = 1; self::strlen($key) < $length; $block_index++)
+		{
+			$key_block = hash_hmac($digest, $key_block.$info.chr($block_index), $prk, TRUE);
+			$key .= $key_block;
+		}
+
+		return self::substr($key, 0, $length);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * __get() magic
+	 *
+	 * @param	string	$key	Property name
+	 * @return	mixed
+	 */
+	public function __get($key)
+	{
+		// Because aliases
+		if ($key === 'mode')
+		{
+			return array_search($this->_mode, $this->_modes[$this->_driver], TRUE);
+		}
+		elseif (in_array($key, array('cipher', 'driver', 'drivers', 'digests'), TRUE))
+		{
+			return $this->{'_'.$key};
+		}
+
+		return NULL;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe strlen()
+	 *
+	 * @param	string	$str
+	 * @return	int
+	 */
+	protected static function strlen($str)
+	{
+		return (self::$func_overload)
+			? mb_strlen($str, '8bit')
+			: strlen($str);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Byte-safe substr()
+	 *
+	 * @param	string	$str
+	 * @param	int	$start
+	 * @param	int	$length
+	 * @return	string
+	 */
+	protected static function substr($str, $start, $length = NULL)
+	{
+		if (self::$func_overload)
+		{
+			// mb_substr($str, $start, null, '8bit') returns an empty
+			// string on PHP 5.3
+			isset($length) OR $length = ($start >= 0 ? self::strlen($str) - $start : -$start);
+			return mb_substr($str, $start, $length, '8bit');
+		}
+
+		return isset($length)
+			? substr($str, $start, $length)
+			: substr($str, $start);
+	}
+}