| // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "crypto/hmac.h" |
| |
| #include <openssl/hmac.h> |
| #include <stddef.h> |
| |
| #include <algorithm> |
| |
| #include "base/logging.h" |
| #include "base/stl_util.h" |
| #include "crypto/openssl_util.h" |
| #include "crypto/secure_util.h" |
| #include "crypto/symmetric_key.h" |
| |
| namespace crypto { |
| |
| HMAC::HMAC(HashAlgorithm hash_alg) : hash_alg_(hash_alg), initialized_(false) { |
| // Only SHA-1 and SHA-256 hash algorithms are supported now. |
| DCHECK(hash_alg_ == SHA1 || hash_alg_ == SHA256); |
| } |
| |
| HMAC::~HMAC() { |
| // Zero out key copy. |
| key_.assign(key_.size(), 0); |
| STLClearObject(&key_); |
| } |
| |
| size_t HMAC::DigestLength() const { |
| switch (hash_alg_) { |
| case SHA1: |
| return 20; |
| case SHA256: |
| return 32; |
| default: |
| NOTREACHED(); |
| return 0; |
| } |
| } |
| |
| bool HMAC::Init(const unsigned char* key, size_t key_length) { |
| // Init must not be called more than once on the same HMAC object. |
| DCHECK(!initialized_); |
| initialized_ = true; |
| key_.assign(key, key + key_length); |
| return true; |
| } |
| |
| bool HMAC::Init(SymmetricKey* key) { |
| std::string raw_key; |
| bool result = key->GetRawKey(&raw_key) && Init(raw_key); |
| // Zero out key copy. This might get optimized away, but one can hope. |
| // Using std::string to store key info at all is a larger problem. |
| std::fill(raw_key.begin(), raw_key.end(), 0); |
| return result; |
| } |
| |
| bool HMAC::Sign(const base::StringPiece& data, |
| unsigned char* digest, |
| size_t digest_length) const { |
| DCHECK(initialized_); |
| |
| ScopedOpenSSLSafeSizeBuffer<EVP_MAX_MD_SIZE> result(digest, digest_length); |
| return !!::HMAC(hash_alg_ == SHA1 ? EVP_sha1() : EVP_sha256(), |
| key_.data(), key_.size(), |
| reinterpret_cast<const unsigned char*>(data.data()), |
| data.size(), result.safe_buffer(), NULL); |
| } |
| |
| bool HMAC::Verify(const base::StringPiece& data, |
| const base::StringPiece& digest) const { |
| if (digest.size() != DigestLength()) |
| return false; |
| return VerifyTruncated(data, digest); |
| } |
| |
| bool HMAC::VerifyTruncated(const base::StringPiece& data, |
| const base::StringPiece& digest) const { |
| if (digest.empty()) |
| return false; |
| size_t digest_length = DigestLength(); |
| std::unique_ptr<unsigned char[]> computed_digest( |
| new unsigned char[digest_length]); |
| if (!Sign(data, computed_digest.get(), digest_length)) |
| return false; |
| |
| return SecureMemEqual(digest.data(), computed_digest.get(), |
| std::min(digest.size(), digest_length)); |
| } |
| |
| } // namespace crypto |