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 <algorithm>
8
9 #include "base/logging.h"
10 #include "crypto/secure_util.h"
11 #include "crypto/symmetric_key.h"
12
13 namespace crypto {
14
Init(SymmetricKey * key)15 bool HMAC::Init(SymmetricKey* key) {
16 std::string raw_key;
17 bool result = key->GetRawKey(&raw_key) && Init(raw_key);
18 // Zero out key copy. This might get optimized away, but one can hope.
19 // Using std::string to store key info at all is a larger problem.
20 std::fill(raw_key.begin(), raw_key.end(), 0);
21 return result;
22 }
23
DigestLength() const24 size_t HMAC::DigestLength() const {
25 switch (hash_alg_) {
26 case SHA1:
27 return 20;
28 case SHA256:
29 return 32;
30 default:
31 NOTREACHED();
32 return 0;
33 }
34 }
35
Verify(const base::StringPiece & data,const base::StringPiece & digest) const36 bool HMAC::Verify(const base::StringPiece& data,
37 const base::StringPiece& digest) const {
38 if (digest.size() != DigestLength())
39 return false;
40 return VerifyTruncated(data, digest);
41 }
42
VerifyTruncated(const base::StringPiece & data,const base::StringPiece & digest) const43 bool HMAC::VerifyTruncated(const base::StringPiece& data,
44 const base::StringPiece& digest) const {
45 if (digest.empty())
46 return false;
47 size_t digest_length = DigestLength();
48 scoped_ptr<unsigned char[]> computed_digest(
49 new unsigned char[digest_length]);
50 if (!Sign(data, computed_digest.get(), digest_length))
51 return false;
52
53 return SecureMemEqual(digest.data(), computed_digest.get(),
54 std::min(digest.size(), digest_length));
55 }
56
57 } // namespace crypto
58