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 65
