crypto/hmac_openssl.cc

   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 #include "crypto/hmac.h"
   6
   7 #include <openssl/hmac.h>
   8
   9 #include <algorithm>
  10 #include <vector>
  11
  12 #include "base/logging.h"
  13 #include "base/memory/scoped_ptr.h"
  14 #include "base/stl_util.h"
  15 #include "crypto/openssl_util.h"
  16
  17 namespace crypto {
  18
  19 struct HMACPlatformData {
  20   std::vector<unsigned char> key;
  21 };
  22
  23 HMAC::HMAC(HashAlgorithm hash_alg)
  24     : hash_alg_(hash_alg), plat_(new HMACPlatformData()) {
  25   // Only SHA-1 and SHA-256 hash algorithms are supported now.
  26   DCHECK(hash_alg_ == SHA1 || hash_alg_ == SHA256);
  27 }
  28
  29 bool HMAC::Init(const unsigned char* key, size_t key_length) {
  30   // Init must not be called more than once on the same HMAC object.
  31   DCHECK(plat_->key.empty());
  32
  33   plat_->key.assign(key, key + key_length);
  34   if (key_length == 0) {
  35     // Special-case: if the key is empty, use a key with one zero
  36     // byte. OpenSSL's HMAC function breaks when passed a NULL key. (It calls
  37     // HMAC_Init_ex which treats a NULL key as having already been initialized
  38     // with a key previously.) HMAC pads keys with zeros, so this key is
  39     // equivalent.
  40     plat_->key.push_back(0);
  41   }
  42   return true;
  43 }
  44
  45 HMAC::~HMAC() {
  46   // Zero out key copy.
  47   plat_->key.assign(plat_->key.size(), 0);
  48   STLClearObject(&plat_->key);
  49 }
  50
  51 bool HMAC::Sign(const base::StringPiece& data,
  52                 unsigned char* digest,
  53                 size_t digest_length) const {
  54   DCHECK(!plat_->key.empty());  // Init must be called before Sign.
  55
  56   ScopedOpenSSLSafeSizeBuffer<EVP_MAX_MD_SIZE> result(digest, digest_length);
  57   return ::HMAC(hash_alg_ == SHA1 ? EVP_sha1() : EVP_sha256(),
  58                 &plat_->key[0], plat_->key.size(),
  59                 reinterpret_cast<const unsigned char*>(data.data()),
  60                 data.size(),
  61                 result.safe_buffer(), NULL);
  62 }
  63
  64 }  // namespace crypto