1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Utility class for calculating the HMAC for a given message. We currently
6// only support SHA1 for the hash algorithm, but this can be extended easily.
7
8#ifndef CRYPTO_HMAC_H_
9#define CRYPTO_HMAC_H_
10#pragma once
11
12#include <string>
13
14#include "base/basictypes.h"
15#include "base/memory/scoped_ptr.h"
16
17namespace crypto {
18
19// Simplify the interface and reduce includes by abstracting out the internals.
20struct HMACPlatformData;
21
22class HMAC {
23 public:
24  // The set of supported hash functions. Extend as required.
25  enum HashAlgorithm {
26    SHA1,
27    SHA256,
28  };
29
30  explicit HMAC(HashAlgorithm hash_alg);
31  ~HMAC();
32
33  // Initializes this instance using |key| of the length |key_length|. Call Init
34  // only once. It returns false on the second or later calls.
35  bool Init(const unsigned char* key, int key_length);
36
37  // Initializes this instance using |key|. Call Init only once. It returns
38  // false on the second or later calls.
39  bool Init(const std::string& key) {
40    return Init(reinterpret_cast<const unsigned char*>(key.data()),
41                static_cast<int>(key.size()));
42  }
43
44  // Calculates the HMAC for the message in |data| using the algorithm supplied
45  // to the constructor and the key supplied to the Init method. The HMAC is
46  // returned in |digest|, which has |digest_length| bytes of storage available.
47  bool Sign(const std::string& data, unsigned char* digest, int digest_length);
48
49  // TODO(albertb): Add a Verify method.
50
51 private:
52  HashAlgorithm hash_alg_;
53  scoped_ptr<HMACPlatformData> plat_;
54
55  DISALLOW_COPY_AND_ASSIGN(HMAC);
56};
57
58}  // namespace crypto
59
60#endif  // CRYPTO_HMAC_H_
61