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<?php
/**
 * Core Security
 *
 * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
 * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 *
 * Licensed under The MIT License
 * For full copyright and license information, please see the LICENSE.txt
 * Redistributions of files must retain the above copyright notice.
 *
 * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
 * @link          http://cakephp.org CakePHP(tm) Project
 * @package       Cake.Utility
 * @since         CakePHP(tm) v .0.10.0.1233
 * @license       http://www.opensource.org/licenses/mit-license.php MIT License
 */

App::uses('String', 'Utility');

/**
 * Security Library contains utility methods related to security
 *
 * @package       Cake.Utility
 */
class Security {

/**
 * Default hash method
 *
 * @var string
 */
        public static $hashType = null;

/**
 * Default cost
 *
 * @var string
 */
        public static $hashCost = '10';

/**
 * Get allowed minutes of inactivity based on security level.
 *
 * @deprecated Exists for backwards compatibility only, not used by the core
 * @return int Allowed inactivity in minutes
 */
        public static function inactiveMins() {
                switch (Configure::read('Security.level')) {
                        case 'high':
                                return 10;
                        case 'medium':
                                return 100;
                        case 'low':
                        default:
                                return 300;
                }
        }

/**
 * Generate authorization hash.
 *
 * @return string Hash
 */
        public static function generateAuthKey() {
                return Security::hash(String::uuid());
        }

/**
 * Validate authorization hash.
 *
 * @param string $authKey Authorization hash
 * @return bool Success
 */
        public static function validateAuthKey($authKey) {
                return true;
        }

/**
 * Create a hash from string using given method or fallback on next available method.
 *
 * #### Using Blowfish
 *
 * - Creating Hashes: *Do not supply a salt*. Cake handles salt creation for
 * you ensuring that each hashed password will have a *unique* salt.
 * - Comparing Hashes: Simply pass the originally hashed password as the salt.
 * The salt is prepended to the hash and php handles the parsing automagically.
 * For convenience the `BlowfishPasswordHasher` class is available for use with
 * the AuthComponent.
 * - Do NOT use a constant salt for blowfish!
 *
 * Creating a blowfish/bcrypt hash:
 *
 * {{{
 *      $hash = Security::hash($password, 'blowfish');
 * }}}
 *
 * @param string $string String to hash
 * @param string $type Method to use (sha1/sha256/md5/blowfish)
 * @param mixed $salt If true, automatically prepends the application's salt
 *     value to $string (Security.salt). If you are using blowfish the salt
 *     must be false or a previously generated salt.
 * @return string Hash
 * @link http://book.cakephp.org/2.0/en/core-utility-libraries/security.html#Security::hash
 */
        public static function hash($string, $type = null, $salt = false) {
                if (empty($type)) {
                        $type = self::$hashType;
                }
                $type = strtolower($type);

                if ($type === 'blowfish') {
                        return self::_crypt($string, $salt);
                }
                if ($salt) {
                        if (!is_string($salt)) {
                                $salt = Configure::read('Security.salt');
                        }
                        $string = $salt . $string;
                }

                if (!$type || $type === 'sha1') {
                        if (function_exists('sha1')) {
                                return sha1($string);
                        }
                        $type = 'sha256';
                }

                if ($type === 'sha256' && function_exists('mhash')) {
                        return bin2hex(mhash(MHASH_SHA256, $string));
                }

                if (function_exists('hash')) {
                        return hash($type, $string);
                }
                return md5($string);
        }

/**
 * Sets the default hash method for the Security object. This affects all objects using
 * Security::hash().
 *
 * @param string $hash Method to use (sha1/sha256/md5/blowfish)
 * @return void
 * @see Security::hash()
 */
        public static function setHash($hash) {
                self::$hashType = $hash;
        }

/**
 * Sets the cost for they blowfish hash method.
 *
 * @param int $cost Valid values are 4-31
 * @return void
 */
        public static function setCost($cost) {
                if ($cost < 4 || $cost > 31) {
                        trigger_error(__d(
                                'cake_dev',
                                'Invalid value, cost must be between %s and %s',
                                array(4, 31)
                        ), E_USER_WARNING);
                        return null;
                }
                self::$hashCost = $cost;
        }

/**
 * Runs $text through a XOR cipher.
 *
 * *Note* This is not a cryptographically strong method and should not be used
 * for sensitive data. Additionally this method does *not* work in environments
 * where suhosin is enabled.
 *
 * Instead you should use Security::rijndael() when you need strong
 * encryption.
 *
 * @param string $text Encrypted string to decrypt, normal string to encrypt
 * @param string $key Key to use
 * @return string Encrypted/Decrypted string
 * @deprecated Will be removed in 3.0.
 */
        public static function cipher($text, $key) {
                if (empty($key)) {
                        trigger_error(__d('cake_dev', 'You cannot use an empty key for %s', 'Security::cipher()'), E_USER_WARNING);
                        return '';
                }

                srand(Configure::read('Security.cipherSeed'));
                $out = '';
                $keyLength = strlen($key);
                for ($i = 0, $textLength = strlen($text); $i < $textLength; $i++) {
                        $j = ord(substr($key, $i % $keyLength, 1));
                        while ($j--) {
                                rand(0, 255);
                        }
                        $mask = rand(0, 255);
                        $out .= chr(ord(substr($text, $i, 1)) ^ $mask);
                }
                srand();
                return $out;
        }

/**
 * Encrypts/Decrypts a text using the given key using rijndael method.
 *
 * Prior to 2.3.1, a fixed initialization vector was used. This was not
 * secure. This method now uses a random iv, and will silently upgrade values when
 * they are re-encrypted.
 *
 * @param string $text Encrypted string to decrypt, normal string to encrypt
 * @param string $key Key to use as the encryption key for encrypted data.
 * @param string $operation Operation to perform, encrypt or decrypt
 * @return string Encrypted/Decrypted string
 */
        public static function rijndael($text, $key, $operation) {
                if (empty($key)) {
                        trigger_error(__d('cake_dev', 'You cannot use an empty key for %s', 'Security::rijndael()'), E_USER_WARNING);
                        return '';
                }
                if (empty($operation) || !in_array($operation, array('encrypt', 'decrypt'))) {
                        trigger_error(__d('cake_dev', 'You must specify the operation for Security::rijndael(), either encrypt or decrypt'), E_USER_WARNING);
                        return '';
                }
                if (strlen($key) < 32) {
                        trigger_error(__d('cake_dev', 'You must use a key larger than 32 bytes for Security::rijndael()'), E_USER_WARNING);
                        return '';
                }
                $algorithm = MCRYPT_RIJNDAEL_256;
                $mode = MCRYPT_MODE_CBC;
                $ivSize = mcrypt_get_iv_size($algorithm, $mode);

                $cryptKey = substr($key, 0, 32);

                if ($operation === 'encrypt') {
                        $iv = mcrypt_create_iv($ivSize, MCRYPT_RAND);
                        return $iv . '$$' . mcrypt_encrypt($algorithm, $cryptKey, $text, $mode, $iv);
                }
                // Backwards compatible decrypt with fixed iv
                if (substr($text, $ivSize, 2) !== '$$') {
                        $iv = substr($key, strlen($key) - 32, 32);
                        return rtrim(mcrypt_decrypt($algorithm, $cryptKey, $text, $mode, $iv), "\0");
                }
                $iv = substr($text, 0, $ivSize);
                $text = substr($text, $ivSize + 2);
                return rtrim(mcrypt_decrypt($algorithm, $cryptKey, $text, $mode, $iv), "\0");
        }

/**
 * Generates a pseudo random salt suitable for use with php's crypt() function.
 * The salt length should not exceed 27. The salt will be composed of
 * [./0-9A-Za-z]{$length}.
 *
 * @param int $length The length of the returned salt
 * @return string The generated salt
 */
        protected static function _salt($length = 22) {
                $salt = str_replace(
                        array('+', '='),
                        '.',
                        base64_encode(sha1(uniqid(Configure::read('Security.salt'), true), true))
                );
                return substr($salt, 0, $length);
        }

/**
 * One way encryption using php's crypt() function. To use blowfish hashing see ``Security::hash()``
 *
 * @param string $password The string to be encrypted.
 * @param mixed $salt false to generate a new salt or an existing salt.
 * @return string The hashed string or an empty string on error.
 */
        protected static function _crypt($password, $salt = false) {
                if ($salt === false) {
                        $salt = self::_salt(22);
                        $salt = vsprintf('$2a$%02d$%s', array(self::$hashCost, $salt));
                }

                $invalidCipher = (
                        strpos($salt, '$2y$') !== 0 &&
                        strpos($salt, '$2x$') !== 0 &&
                        strpos($salt, '$2a$') !== 0
                );
                if ($salt === true || $invalidCipher || strlen($salt) < 29) {
                        trigger_error(__d(
                                'cake_dev',
                                'Invalid salt: %s for %s Please visit http://www.php.net/crypt and read the appropriate section for building %s salts.',
                                array($salt, 'blowfish', 'blowfish')
                        ), E_USER_WARNING);
                        return '';
                }
                return crypt($password, $salt);
        }

/**
 * Encrypt a value using AES-256.
 *
 * *Caveat* You cannot properly encrypt/decrypt data with trailing null bytes.
 * Any trailing null bytes will be removed on decryption due to how PHP pads messages
 * with nulls prior to encryption.
 *
 * @param string $plain The value to encrypt.
 * @param string $key The 256 bit/32 byte key to use as a cipher key.
 * @param string $hmacSalt The salt to use for the HMAC process. Leave null to use Security.salt.
 * @return string Encrypted data.
 * @throws CakeException On invalid data or key.
 */
        public static function encrypt($plain, $key, $hmacSalt = null) {
                self::_checkKey($key, 'encrypt()');

                if ($hmacSalt === null) {
                        $hmacSalt = Configure::read('Security.salt');
                }

                // Generate the encryption and hmac key.
                $key = substr(hash('sha256', $key . $hmacSalt), 0, 32);

                $algorithm = MCRYPT_RIJNDAEL_128;
                $mode = MCRYPT_MODE_CBC;

                $ivSize = mcrypt_get_iv_size($algorithm, $mode);
                $iv = mcrypt_create_iv($ivSize, MCRYPT_DEV_URANDOM);
                $ciphertext = $iv . mcrypt_encrypt($algorithm, $key, $plain, $mode, $iv);
                $hmac = hash_hmac('sha256', $ciphertext, $key);
                return $hmac . $ciphertext;
        }

/**
 * Check the encryption key for proper length.
 *
 * @param string $key Key to check.
 * @param string $method The method the key is being checked for.
 * @return void
 * @throws CakeException When key length is not 256 bit/32 bytes
 */
        protected static function _checkKey($key, $method) {
                if (strlen($key) < 32) {
                        throw new CakeException(__d('cake_dev', 'Invalid key for %s, key must be at least 256 bits (32 bytes) long.', $method));
                }
        }

/**
 * Decrypt a value using AES-256.
 *
 * @param string $cipher The ciphertext to decrypt.
 * @param string $key The 256 bit/32 byte key to use as a cipher key.
 * @param string $hmacSalt The salt to use for the HMAC process. Leave null to use Security.salt.
 * @return string Decrypted data. Any trailing null bytes will be removed.
 * @throws CakeException On invalid data or key.
 */
        public static function decrypt($cipher, $key, $hmacSalt = null) {
                self::_checkKey($key, 'decrypt()');
                if (empty($cipher)) {
                        throw new CakeException(__d('cake_dev', 'The data to decrypt cannot be empty.'));
                }
                if ($hmacSalt === null) {
                        $hmacSalt = Configure::read('Security.salt');
                }

                // Generate the encryption and hmac key.
                $key = substr(hash('sha256', $key . $hmacSalt), 0, 32);

                // Split out hmac for comparison
                $macSize = 64;
                $hmac = substr($cipher, 0, $macSize);
                $cipher = substr($cipher, $macSize);

                $compareHmac = hash_hmac('sha256', $cipher, $key);
                if ($hmac !== $compareHmac) {
                        return false;
                }

                $algorithm = MCRYPT_RIJNDAEL_128;
                $mode = MCRYPT_MODE_CBC;
                $ivSize = mcrypt_get_iv_size($algorithm, $mode);

                $iv = substr($cipher, 0, $ivSize);
                $cipher = substr($cipher, $ivSize);
                $plain = mcrypt_decrypt($algorithm, $key, $cipher, $mode, $iv);
                return rtrim($plain, "\0");
        }

}