LockrAes128CtrSha256KeyWrapper.php in Lockr 7.3

Namespace

Lockr\KeyWrapper

File

vendor/lockr/lockr/src/KeyWrapper/LockrAes128CtrSha256KeyWrapper.php

<?php

namespace Lockr\KeyWrapper;

class LockrAes128CtrSha256KeyWrapper implements KeyWrapperInterface {
  const PREFIX = 'aes-128-ctr-sha256';
  const METHOD = 'aes-128-ctr';
  const HASH_BYTES = 44;

  /**
   * {@inheritdoc}
   */
  public static function enabled() {
    return function_exists('openssl_encrypt');
  }

  /**
   * {@inheritdoc}
   */
  public static function encrypt($plaintext, $key = null) {
    if (is_null($key)) {
      $key = openssl_random_pseudo_bytes(16);
    }
    $iv_len = openssl_cipher_iv_length(self::METHOD);
    $iv = openssl_random_pseudo_bytes($iv_len);
    $hmac_key = openssl_random_pseudo_bytes(32);
    return self::doEncrypt($plaintext, $key, $iv, $hmac_key);
  }

  /**
   * {@inheritdoc}
   */
  public static function reencrypt($plaintext, $wrapping_key) {
    $parts = self::decode($wrapping_key);
    if (!$parts) {
      return false;
    }
    list($key, $iv, $hmac_key) = $parts;
    return self::doEncrypt($plaintext, $key, $iv, $hmac_key);
  }

  /**
   * {@inheritdoc}
   */
  public static function decrypt($ciphertext, $wrapping_key) {
    $parts = self::decode($wrapping_key);
    if (!$parts) {
      return false;
    }
    list($key, $iv, $hmac_key) = $parts;
    $hmac = base64_decode(substr($ciphertext, 0, self::HASH_BYTES));
    $ciphertext = base64_decode(substr($ciphertext, self::HASH_BYTES));
    if (!hash_equals($hmac, self::hmac($ciphertext, $hmac_key))) {
      return false;
    }
    $plaintext = openssl_decrypt($ciphertext, self::METHOD, $key, OPENSSL_RAW_DATA, $iv);
    if ($plaintext === false) {
      return false;
    }
    return $plaintext;
  }
  private static function doEncrypt($plaintext, $key, $iv, $hmac_key) {
    $ciphertext = openssl_encrypt($plaintext, self::METHOD, $key, OPENSSL_RAW_DATA, $iv);
    $hmac = self::hmac($ciphertext, $hmac_key);
    return [
      'ciphertext' => base64_encode($hmac) . base64_encode($ciphertext),
      'encoded' => self::encode($key, $iv, $hmac_key),
    ];
  }
  private static function hmac($data, $key) {
    return hash_hmac('sha256', $data, $key, true);
  }
  private static function encode($key, $iv, $hmac_key) {
    $parts = [
      self::PREFIX,
      base64_encode($key),
      base64_encode($iv),
      base64_encode($hmac_key),
    ];
    return implode('$', $parts);
  }
  private static function decode($wrapping_key) {
    $parts = explode('$', $wrapping_key, 4);
    if (!$parts || count($parts) !== 4) {
      return false;
    }
    list($prefix, $key, $iv, $hmac_key) = $parts;
    if ($prefix !== self::PREFIX) {
      return false;
    }
    return [
      base64_decode($key),
      base64_decode($iv),
      base64_decode($hmac_key),
    ];
  }

}

// ex: ts=4 sts=4 sw=4 et:

Classes

Name	Description
LockrAes128CtrSha256KeyWrapper