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// 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 <stddef.h>
#include <algorithm>
#include <string>
#include "base/logging.h"
#include "base/stl_util.h"
#include "crypto/openssl_util.h"
#include "crypto/secure_util.h"
#include "crypto/symmetric_key.h"
#include "third_party/boringssl/src/include/openssl/hmac.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);
base::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(), nullptr);
}
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
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