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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/encryptor.h"
#include "base/logging.h"
#include "base/sys_byteorder.h"
namespace crypto {
/////////////////////////////////////////////////////////////////////////////
// Encyptor::Counter Implementation.
Encryptor::Counter::Counter(const base::StringPiece& counter) {
CHECK(sizeof(counter_) == counter.length());
memcpy(&counter_, counter.data(), sizeof(counter_));
}
Encryptor::Counter::~Counter() {
}
bool Encryptor::Counter::Increment() {
uint64 low_num = base::NetToHost64(counter_.components64[1]);
uint64 new_low_num = low_num + 1;
counter_.components64[1] = base::HostToNet64(new_low_num);
// If overflow occured then increment the most significant component.
if (new_low_num < low_num) {
counter_.components64[0] =
base::HostToNet64(base::NetToHost64(counter_.components64[0]) + 1);
}
// TODO(hclam): Return false if counter value overflows.
return true;
}
void Encryptor::Counter::Write(void* buf) {
uint8* buf_ptr = reinterpret_cast<uint8*>(buf);
memcpy(buf_ptr, &counter_, sizeof(counter_));
}
size_t Encryptor::Counter::GetLengthInBytes() const {
return sizeof(counter_);
}
/////////////////////////////////////////////////////////////////////////////
// Partial Encryptor Implementation.
bool Encryptor::SetCounter(const base::StringPiece& counter) {
if (mode_ != CTR)
return false;
if (counter.length() != 16u)
return false;
counter_.reset(new Counter(counter));
return true;
}
bool Encryptor::GenerateCounterMask(size_t plaintext_len,
uint8* mask,
size_t* mask_len) {
DCHECK_EQ(CTR, mode_);
CHECK(mask);
CHECK(mask_len);
const size_t kBlockLength = counter_->GetLengthInBytes();
size_t blocks = (plaintext_len + kBlockLength - 1) / kBlockLength;
CHECK(blocks);
*mask_len = blocks * kBlockLength;
for (size_t i = 0; i < blocks; ++i) {
counter_->Write(mask);
mask += kBlockLength;
bool ret = counter_->Increment();
if (!ret)
return false;
}
return true;
}
void Encryptor::MaskMessage(const void* plaintext,
size_t plaintext_len,
const void* mask,
void* ciphertext) const {
DCHECK_EQ(CTR, mode_);
const uint8* plaintext_ptr = reinterpret_cast<const uint8*>(plaintext);
const uint8* mask_ptr = reinterpret_cast<const uint8*>(mask);
uint8* ciphertext_ptr = reinterpret_cast<uint8*>(ciphertext);
for (size_t i = 0; i < plaintext_len; ++i)
ciphertext_ptr[i] = plaintext_ptr[i] ^ mask_ptr[i];
}
} // namespace crypto
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