crypto/hmac.cc

   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
  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
  24 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
  36 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
  43 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_array<unsigned char> computed_digest(
  49       new unsigned char[digest_length]);
  50   if (!Sign(data, computed_digest.get(), static_cast<int>(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