<?php
/**
 * SecurityManager class file.
 *
 * @link http://www.yiiframework.com/
 * @copyright Copyright &copy; 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\base;

/**
 * SecurityManager provides private keys, hashing and encryption functions.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class SecurityManager extends Component
{
	const STATE_VALIDATION_KEY = 'Yii.SecurityManager.validationkey';
	const STATE_ENCRYPTION_KEY = 'Yii.SecurityManager.encryptionkey';

	/**
	 * @var string the name of the hashing algorithm to be used by {@link computeHMAC}.
	 * See {@link http://php.net/manual/en/function.hash-algos.php hash-algos} for the list of possible
	 * hash algorithms. Note that if you are using PHP 5.1.1 or below, you can only use 'sha1' or 'md5'.
	 *
	 * Defaults to 'sha1', meaning using SHA1 hash algorithm.
	 */
	public $hashAlgorithm = 'sha1';
	/**
	 * @var mixed the name of the crypt algorithm to be used by {@link encrypt} and {@link decrypt}.
	 * This will be passed as the first parameter to {@link http://php.net/manual/en/function.mcrypt-module-open.php mcrypt_module_open}.
	 *
	 * This property can also be configured as an array. In this case, the array elements will be passed in order
	 * as parameters to mcrypt_module_open. For example, <code>array('rijndael-256', '', 'ofb', '')</code>.
	 *
	 * Defaults to 'des', meaning using DES crypt algorithm.
	 */
	public $cryptAlgorithm = 'des';

	private $_validationKey;
	private $_encryptionKey;

	/**
	 * @return string a randomly generated private key
	 */
	protected function generateRandomKey()
	{
		return sprintf('%08x%08x%08x%08x', mt_rand(), mt_rand(), mt_rand(), mt_rand());
	}

	/**
	 * @return string the private key used to generate HMAC.
	 * If the key is not explicitly set, a random one is generated and returned.
	 */
	public function getValidationKey()
	{
		if ($this->_validationKey !== null) {
			return $this->_validationKey;
		} else {
			if (($key = \Yii::$application->getGlobalState(self::STATE_VALIDATION_KEY)) !== null) {
				$this->setValidationKey($key);
			} else {
				$key = $this->generateRandomKey();
				$this->setValidationKey($key);
				\Yii::$application->setGlobalState(self::STATE_VALIDATION_KEY, $key);
			}
			return $this->_validationKey;
		}
	}

	/**
	 * @param string $value the key used to generate HMAC
	 * @throws CException if the key is empty
	 */
	public function setValidationKey($value)
	{
		if (!empty($value)) {
			$this->_validationKey = $value;
		} else {
			throw new CException(Yii::t('yii|SecurityManager.validationKey cannot be empty.'));
		}
	}

	/**
	 * @return string the private key used to encrypt/decrypt data.
	 * If the key is not explicitly set, a random one is generated and returned.
	 */
	public function getEncryptionKey()
	{
		if ($this->_encryptionKey !== null) {
			return $this->_encryptionKey;
		} else {
			if (($key = \Yii::$application->getGlobalState(self::STATE_ENCRYPTION_KEY)) !== null) {
				$this->setEncryptionKey($key);
			} else {
				$key = $this->generateRandomKey();
				$this->setEncryptionKey($key);
				\Yii::$application->setGlobalState(self::STATE_ENCRYPTION_KEY, $key);
			}
			return $this->_encryptionKey;
		}
	}

	/**
	 * @param string $value the key used to encrypt/decrypt data.
	 * @throws CException if the key is empty
	 */
	public function setEncryptionKey($value)
	{
		if (!empty($value)) {
			$this->_encryptionKey = $value;
		} else {
			throw new CException(Yii::t('yii|SecurityManager.encryptionKey cannot be empty.'));
		}
	}

	/**
	 * This method has been deprecated since version 1.1.3.
	 * Please use {@link hashAlgorithm} instead.
	 * @return string
	 */
	public function getValidation()
	{
		return $this->hashAlgorithm;
	}

	/**
	 * This method has been deprecated since version 1.1.3.
	 * Please use {@link hashAlgorithm} instead.
	 * @param string $value -
	 */
	public function setValidation($value)
	{
		$this->hashAlgorithm = $value;
	}

	/**
	 * Encrypts data.
	 * @param string $data data to be encrypted.
	 * @param string $key the decryption key. This defaults to null, meaning using {@link getEncryptionKey EncryptionKey}.
	 * @return string the encrypted data
	 * @throws CException if PHP Mcrypt extension is not loaded
	 */
	public function encrypt($data, $key = null)
	{
		$module = $this->openCryptModule();
		$key = $this->substr($key === null ? md5($this->getEncryptionKey()) : $key, 0, mcrypt_enc_get_key_size($module));
		srand();
		$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($module), MCRYPT_RAND);
		mcrypt_generic_init($module, $key, $iv);
		$encrypted = $iv . mcrypt_generic($module, $data);
		mcrypt_generic_deinit($module);
		mcrypt_module_close($module);
		return $encrypted;
	}

	/**
	 * Decrypts data
	 * @param string $data data to be decrypted.
	 * @param string $key the decryption key. This defaults to null, meaning using {@link getEncryptionKey EncryptionKey}.
	 * @return string the decrypted data
	 * @throws CException if PHP Mcrypt extension is not loaded
	 */
	public function decrypt($data, $key = null)
	{
		$module = $this->openCryptModule();
		$key = $this->substr($key === null ? md5($this->getEncryptionKey()) : $key, 0, mcrypt_enc_get_key_size($module));
		$ivSize = mcrypt_enc_get_iv_size($module);
		$iv = $this->substr($data, 0, $ivSize);
		mcrypt_generic_init($module, $key, $iv);
		$decrypted = mdecrypt_generic($module, $this->substr($data, $ivSize, $this->strlen($data)));
		mcrypt_generic_deinit($module);
		mcrypt_module_close($module);
		return rtrim($decrypted, "\0");
	}

	/**
	 * Opens the mcrypt module with the configuration specified in {@link cryptAlgorithm}.
	 * @return resource the mycrypt module handle.
	 * @since 1.1.3
	 */
	protected function openCryptModule()
	{
		if (extension_loaded('mcrypt')) {
			if (is_array($this->cryptAlgorithm)) {
				$module = @call_user_func_array('mcrypt_module_open', $this->cryptAlgorithm);
			} else {
				$module = @mcrypt_module_open($this->cryptAlgorithm, '', MCRYPT_MODE_CBC, '');
			}

			if ($module === false) {
				throw new CException(Yii::t('yii|Failed to initialize the mcrypt module.'));
			}

			return $module;
		} else {
			throw new CException(Yii::t('yii|SecurityManager requires PHP mcrypt extension to be loaded in order to use data encryption feature.'));
		}
	}

	/**
	 * Prefixes data with an HMAC.
	 * @param string $data data to be hashed.
	 * @param string $key the private key to be used for generating HMAC. Defaults to null, meaning using {@link validationKey}.
	 * @return string data prefixed with HMAC
	 */
	public function hashData($data, $key = null)
	{
		return $this->computeHMAC($data, $key) . $data;
	}

	/**
	 * Validates if data is tampered.
	 * @param string $data data to be validated. The data must be previously
	 * generated using {@link hashData()}.
	 * @param string $key the private key to be used for generating HMAC. Defaults to null, meaning using {@link validationKey}.
	 * @return string the real data with HMAC stripped off. False if the data
	 * is tampered.
	 */
	public function validateData($data, $key = null)
	{
		$len = $this->strlen($this->computeHMAC('test'));
		if ($this->strlen($data) >= $len) {
			$hmac = $this->substr($data, 0, $len);
			$data2 = $this->substr($data, $len, $this->strlen($data));
			return $hmac === $this->computeHMAC($data2, $key) ? $data2 : false;
		} else {
			return false;
		}
	}

	/**
	 * Computes the HMAC for the data with {@link getValidationKey ValidationKey}.
	 * @param string $data data to be generated HMAC
	 * @param string $key the private key to be used for generating HMAC. Defaults to null, meaning using {@link validationKey}.
	 * @return string the HMAC for the data
	 */
	protected function computeHMAC($data, $key = null)
	{
		if ($key === null) {
			$key = $this->getValidationKey();
		}

		if (function_exists('hash_hmac')) {
			return hash_hmac($this->hashAlgorithm, $data, $key);
		}

		if (!strcasecmp($this->hashAlgorithm, 'sha1')) {
			$pack = 'H40';
			$func = 'sha1';
		} else {
			$pack = 'H32';
			$func = 'md5';
		}
		if ($this->strlen($key) > 64) {
			$key = pack($pack, $func($key));
		}
		if ($this->strlen($key) < 64) {
			$key = str_pad($key, 64, chr(0));
		}
		$key = $this->substr($key, 0, 64);
		return $func((str_repeat(chr(0x5C), 64) ^ $key) . pack($pack, $func((str_repeat(chr(0x36), 64) ^ $key) . $data)));
	}

	/**
	 * Returns the length of the given string.
	 * If available uses the multibyte string function mb_strlen.
	 * @param string $string the string being measured for length
	 * @return int the length of the string
	 */
	private function strlen($string)
	{
		return function_exists('mb_strlen') ? mb_strlen($string, '8bit') : strlen($string);
	}

	/**
	 * Returns the portion of string specified by the start and length parameters.
	 * If available uses the multibyte string function mb_substr
	 * @param string $string the input string. Must be one character or longer.
	 * @param int $start the starting position
	 * @param int $length the desired portion length
	 * @return string the extracted part of string, or FALSE on failure or an empty string.
	 */
	private function substr($string, $start, $length)
	{
		return function_exists('mb_substr') ? mb_substr($string, $start, $length, '8bit') : substr($string, $start, $length);
	}
}