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   1  <?php
   2  
   3  declare(strict_types=1);
   4  
   5  /*
   6   * The MIT License (MIT)
   7   *
   8   * Copyright (c) 2014-2019 Spomky-Labs
   9   *
  10   * This software may be modified and distributed under the terms
  11   * of the MIT license.  See the LICENSE file for details.
  12   */
  13  
  14  namespace Cose\Algorithm\Mac;
  15  
  16  use Assert\Assertion;
  17  use Cose\Key\Key;
  18  
  19  abstract class Hmac implements Mac
  20  {
  21      public function hash(string $data, Key $key): string
  22      {
  23          $this->checKey($key);
  24          $signature = hash_hmac($this->getHashAlgorithm(), $data, $key->get(-1), true);
  25  
  26          return mb_substr($signature, 0, $this->getSignatureLength() / 8, '8bit');
  27      }
  28  
  29      public function verify(string $data, Key $key, string $signature): bool
  30      {
  31          return hash_equals($this->hash($data, $key), $signature);
  32      }
  33  
  34      private function checKey(Key $key): void
  35      {
  36          Assertion::eq($key->type(), 4, 'Invalid key. Must be of type symmetric');
  37          Assertion::true($key->has(-1), 'Invalid key. The value of the key is missing');
  38      }
  39  
  40      abstract protected function getHashAlgorithm(): string;
  41  
  42      abstract protected function getSignatureLength(): int;
  43  }