web/private_php/ams/autoload/mycrypt.php

   1 <?php
   2 /**
   3 * Basic encryption/decryption class.
   4 * We use this class atm for encrypting & decrypting the imap passwords.
   5 */
   6 class MyCrypt{
   7
   8     private $config; /**< array that should contain the enc_method & hash_method & key */
   9
  10
  11     /**
  12     * constructor.
  13     * loads the config array with the given argument.
  14     * @param $cryptinfo an array containing the info needed to encrypt & decrypt.(enc_method & hash_method & key)
  15     */
  16     function __construct($cryptinfo) {
  17         $this->config = $cryptinfo;
  18     }
  19
  20     /**
  21     * encrypts by using the given enc_method and hash_method.
  22     * It will first check if the methods are supported, if not it will throw an error, if so it will encrypt the $data
  23     * @param $data the string that we want to encrypt.
  24     * @return the encrypted string.
  25     */
  26     public function encrypt($data) {
  27
  28         self::check_methods($this->config['enc_method'], $this->config['hash_method']);
  29         $iv = self::hashIV($this->config['key'], $this->config['hash_method'], openssl_cipher_iv_length($this->config['enc_method']));
  30         $infostr = sprintf('$%s$%s$', $this->config['enc_method'], $this->config['hash_method']);
  31         return $infostr . openssl_encrypt($data, $this->config['enc_method'], $this->config['key'], false, $iv);
  32     }
  33
  34     /**
  35     * decrypts by using the given enc_method and hash_method.
  36     * @param $edata the encrypted string that we want to decrypt
  37     * @return the decrypted string.
  38     */
  39     public function decrypt($edata) {
  40         $e_arr = explode('$', $edata);
  41         if( count($e_arr) != 4 ) {
  42             Throw new Exception('Given data is missing crucial sections.');
  43         }
  44         $this->config['enc_method'] = $e_arr[1];
  45         $this->config['hash_method'] = $e_arr[2];
  46         self::check_methods($this->config['enc_method'], $this->config['hash_method']);
  47         $iv = self::hashIV($this->config['key'], $this->config['hash_method'], openssl_cipher_iv_length($this->config['enc_method']));
  48         return openssl_decrypt($e_arr[3], $this->config['enc_method'], $this->config['key'], false, $iv);
  49     }
  50
  51     /**
  52     * hashes the key by using a hash method specified.
  53     * @param $key the key to be hashed
  54     * @param $method the metho of hashing to be used
  55     * @param $iv_size the size of the initialization vector.
  56     * @return return the hashed key up till the size of the iv_size param.
  57     */
  58     private static function hashIV($key, $method, $iv_size) {
  59         $myhash = hash($method, $key, TRUE);
  60         while( strlen($myhash) < $iv_size ) {
  61             $myhash .= hash($method, $myhash, TRUE);
  62         }
  63         return substr($myhash, 0, $iv_size);
  64     }
  65
  66     /**
  67     * checks if the encryption and hash methods are supported
  68     * @param $enc the encryption method.
  69     * @param $hash the hash method.
  70     * @throw Exception in case a method is not supported.
  71     */
  72     private static function check_methods($enc, $hash) {
  73
  74         if( ! function_exists('openssl_encrypt') ) {
  75             Throw new Exception('openssl_encrypt() not supported.');
  76         } else if( ! in_array($enc, openssl_get_cipher_methods()) ) {
  77             Throw new Exception('Encryption method ' . $enc . ' not supported.');
  78         } else if( ! in_array(strtolower($hash), hash_algos()) ) {
  79             Throw new Exception('Hashing method ' . $hash . ' not supported.');
  80         }
  81     }
  82
  83
  84
  85 }