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<?php
/**
 * Openssl encrypt/decrypt functions
 *
 * Available under the MIT License
 *
 * The MIT License (MIT)
 * Copyright (c) 2016 ionCube Ltd.
 *
 * 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.
 */
class Cryptor {
    private static $instance = null;
    private static $cipher_algo;
    private static $hash_algo;
    private static $keystring;
    private static $iv_num_bytes;
    private static $format;
    private static $hasOpenSSL = true;
    const FORMAT_RAW = 0;
    const FORMAT_B64 = 1;
    const FORMAT_HEX = 2;

    /**
     * Create a Cryptor singleton instance
     * @param array $cryptConfig The cipher algorithm, the hash algorithm and the key.
     * @param [type] $fmt         Optional override for the output encoding. One of FORMAT_RAW, FORMAT_B64 or FORMAT_HEX. Default: FORMAT_B64.
     */
    public static function getInstance($cryptorConfig = null, $fmt = Cryptor::FORMAT_B64) {
        if (is_null(self::$instance)) {
            self::$instance = new self();
            if (!extension_loaded("openssl")) {
                self::$hasOpenSSL = false;
                return self::$instance;
            }
        }
        else {
            return self::$instance;
        }
        // store cryptor configuration
        if (!is_null($cryptorConfig)) {
            if (isset($cryptorConfig['cipherAlgorithm']) && !empty($cryptorConfig['cipherAlgorithm'])) {
                self::$cipher_algo = $cryptorConfig['cipherAlgorithm'];
            }
            else {
                self::$cipher_algo = 'aes-256-cbc';
            }
            if (isset($cryptorConfig['hashAlgorithm']) && !empty($cryptorConfig['hashAlgorithm'])) {
                self::$hash_algo = $cryptorConfig['hashAlgorithm'];
            }
            else {
                self::$hash_algo = 'sha256';
            }
            if (isset($cryptorConfig['key']) && !empty($cryptorConfig['key'])) {
                self::$keystring = $cryptorConfig['key'];
            }
            else {
                throw new \Exception("Cryptor:: - key not set in configuration");
            }
            if ($fmt === Cryptor::FORMAT_RAW || $fmt === Cryptor::FORMAT_B64 || $fmt == Cryptor::FORMAT_HEX) {
                self::$format = $fmt;
            }
            else {
                self::$format = Cryptor::FORMAT_B64;
            }
        }

        if (!in_array(self::$cipher_algo, openssl_get_cipher_methods(true))) {
            throw new \Exception("Cryptor:: - unknown cipher algo {" . self::$cipher_algo . "}");
        }

        if (!in_array(self::$hash_algo, openssl_get_md_methods(true))) {
            throw new \Exception("Cryptor:: - unknown hash algo {" . self::$hash_algo . "}");
        }

        self::$iv_num_bytes = openssl_cipher_iv_length(self::$cipher_algo);

        return self::$instance;
    }
    /**
     * Encrypt a string.
     * @param  string $in  String to encrypt.
     * @param  string $key Optional encryption key.
     * @param  int $fmt Optional override for the output encoding. One of FORMAT_RAW, FORMAT_B64 or FORMAT_HEX.
     * @return string      The encrypted string.
     */
    public static function encryptString($in, $key = null, $fmt = null) {
        if (!self::$hasOpenSSL) {
            return base64_encode($in);
        }
        if ($fmt === null) {
            $fmt = self::$format;
        }
        if ($key === null) {
            $key = self::$keystring;
        }
        // Build an initialization vector
        $iv = openssl_random_pseudo_bytes(self::$iv_num_bytes, $isStrongCrypto);
        if (!$isStrongCrypto) {
            throw new \Exception("Cryptor::encryptString() - Not a strong key");
        }
        // Hash the key
        $keyhash = openssl_digest($key, self::$hash_algo, true);
        // and encrypt
        $opts = OPENSSL_RAW_DATA;
        $encrypted = openssl_encrypt($in, self::$cipher_algo, $keyhash, $opts, $iv);
        if ($encrypted === false) {
            throw new \Exception('Cryptor::encryptString() - Encryption failed: ' . openssl_error_string());
        }
        // The result comprises the IV and encrypted data
        $res = $iv . $encrypted;
        // and format the result if required.
        if ($fmt == Cryptor::FORMAT_B64) {
            $res = base64_encode($res);
        }
        else if ($fmt == Cryptor::FORMAT_HEX) {
            $res = unpack('H*', $res) [1];
        }
        return $res;
    }
    /**
     * Decrypt a string.
     * @param  string $in  String to decrypt.
     * @param  string $key Optional decryption key.
     * @param  int $fmt Optional override for the input encoding. One of FORMAT_RAW, FORMAT_B64 or FORMAT_HEX.
     * @return string      The decrypted string.
     */
    public static function decryptString($in, $key = null, $fmt = null) {
        if (!self::$hasOpenSSL) {
            return base64_decode($in);
        }
        if ($fmt === null) {
            $fmt = self::$format;
        }
        if ($key === null) {
            $key = self::$keystring;
        }
        $raw = $in;
        // Restore the encrypted data if encoded
        if ($fmt == Cryptor::FORMAT_B64) {
            $raw = base64_decode($in);
        }
        else if ($fmt == Cryptor::FORMAT_HEX) {
            $raw = pack('H*', $in);
        }
        // and do an integrity check on the size.
        if (strlen($raw) < self::$iv_num_bytes) {
            throw new \Exception('Cryptor::decryptString() - ' . 'data length ' . strlen($raw) . " is less than iv length {self::$iv_num_bytes}");
        }
        // Extract the initialization vector and encrypted data
        $iv = substr($raw, 0, self::$iv_num_bytes);
        $raw = substr($raw, self::$iv_num_bytes);
        // Hash the key
        $keyhash = openssl_digest($key, self::$hash_algo, true);
        // and decrypt.
        $opts = OPENSSL_RAW_DATA;
        $res = openssl_decrypt($raw, self::$cipher_algo, $keyhash, $opts, $iv);
        if ($res === false) {
            throw new \Exception('Cryptor::decryptString - decryption failed: ' . openssl_error_string());
        }
        return $res;
    }
    /**
     * Static convenience method for encrypting.
     * @param  string $in  String to encrypt.
     * @param  string $key Optional encryption key.
     * @param  int $fmt Optional override for the output encoding. One of FORMAT_RAW, FORMAT_B64 or FORMAT_HEX.
     * @return string      The encrypted string.
     */
    public static function Encrypt($in, $key = null, $fmt = null) {
        return self::encryptString($in, $key, $fmt);
    }
    /**
     * Static convenience method for decrypting.
     * @param  string $in  String to decrypt.
     * @param  string $key Optinal eecryption key.
     * @param  int $fmt Optional override for the input encoding. One of FORMAT_RAW, FORMAT_B64 or FORMAT_HEX.
     * @return string      The decrypted string.
     */
    public static function Decrypt($in, $key = null, $fmt = null) {
        return self::decryptString($in, $key, $fmt);
    }
}