1 // Copyright (c) 2012 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 #include "crypto/hmac.h"
6
7 #include <stddef.h>
8
9 #include <algorithm>
10
11 #include "base/logging.h"
12 #include "crypto/secure_util.h"
13 #include "crypto/symmetric_key.h"
14
15 namespace crypto {
16
Init(SymmetricKey * key)17 bool HMAC::Init(SymmetricKey* key) {
18 std::string raw_key;
19 bool result = key->GetRawKey(&raw_key) && Init(raw_key);
20 // Zero out key copy. This might get optimized away, but one can hope.
21 // Using std::string to store key info at all is a larger problem.
22 std::fill(raw_key.begin(), raw_key.end(), 0);
23 return result;
24 }
25
DigestLength() const26 size_t HMAC::DigestLength() const {
27 switch (hash_alg_) {
28 case SHA1:
29 return 20;
30 case SHA256:
31 return 32;
32 default:
33 NOTREACHED();
34 return 0;
35 }
36 }
37
Verify(const base::StringPiece & data,const base::StringPiece & digest) const38 bool HMAC::Verify(const base::StringPiece& data,
39 const base::StringPiece& digest) const {
40 if (digest.size() != DigestLength())
41 return false;
42 return VerifyTruncated(data, digest);
43 }
44
VerifyTruncated(const base::StringPiece & data,const base::StringPiece & digest) const45 bool HMAC::VerifyTruncated(const base::StringPiece& data,
46 const base::StringPiece& digest) const {
47 if (digest.empty())
48 return false;
49 size_t digest_length = DigestLength();
50 std::unique_ptr<unsigned char[]> computed_digest(
51 new unsigned char[digest_length]);
52 if (!Sign(data, computed_digest.get(), digest_length))
53 return false;
54
55 return SecureMemEqual(digest.data(), computed_digest.get(),
56 std::min(digest.size(), digest_length));
57 }
58
59 } // namespace crypto
60