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// Copyright 2013 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.
#ifndef COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
#define COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
#include <stdint.h>
#include <string.h>
#include <memory>
#include <string>
namespace autofill {
// This is modified RC4 decryption used for import of Toolbar autofill data
// only. The difference from the Crypto Api implementation is twofold:
// First, it uses a non-standard key size (160 bit), not supported by Microsoft
// (it supports only 40 and 128 bit for RC4). Second, it codes 128 words with
// value 0x0020 at the beginning of the code to enhance security.
//
// This class used in
// components/autofill/core/browser/autofill_ie_toolbar_import_win.cc.
//
// This class should not be used anywhere else!!!
class RC4Decryptor {
public:
explicit RC4Decryptor(wchar_t const* password) {
PrepareKey(reinterpret_cast<const uint8_t*>(password),
wcslen(password) * sizeof(wchar_t));
std::wstring data;
// First 128 bytes should be spaces.
data.resize(128, L' ');
Run(data.c_str());
}
// Run the algorithm
std::wstring Run(const std::wstring& data) {
int data_size = data.length() * sizeof(wchar_t);
std::unique_ptr<wchar_t[]> buffer(new wchar_t[data.length() + 1]);
memset(buffer.get(), 0, (data.length() + 1) * sizeof(wchar_t));
memcpy(buffer.get(), data.c_str(), data_size);
RunInternal(reinterpret_cast<uint8_t*>(buffer.get()), data_size);
std::wstring result(buffer.get());
// Clear the memory
memset(buffer.get(), 0, data_size);
return result;
}
private:
static const int kKeyDataSize = 256;
struct Rc4Key {
uint8_t state[kKeyDataSize];
uint8_t x;
uint8_t y;
};
void SwapByte(uint8_t* byte1, uint8_t* byte2) {
uint8_t temp = *byte1;
*byte1 = *byte2;
*byte2 = temp;
}
void PrepareKey(const uint8_t* key_data, int key_data_len) {
uint8_t index1 = 0;
uint8_t index2 = 0;
uint8_t* state;
short counter;
state = &key_.state[0];
for (counter = 0; counter < kKeyDataSize; ++counter)
state[counter] = static_cast<uint8_t>(counter);
key_.x = key_.y = 0;
for (counter = 0; counter < kKeyDataSize; counter++) {
index2 = (key_data[index1] + state[counter] + index2) % kKeyDataSize;
SwapByte(&state[counter], &state[index2]);
index1 = (index1 + 1) % key_data_len;
}
}
void RunInternal(uint8_t* buffer, int buffer_len) {
uint8_t x, y;
uint8_t xor_index = 0;
uint8_t* state;
int counter;
x = key_.x;
y = key_.y;
state = &key_.state[0];
for (counter = 0; counter < buffer_len; ++counter) {
x = (x + 1) % kKeyDataSize;
y = (state[x] + y) % kKeyDataSize;
SwapByte(&state[x], &state[y]);
xor_index = (state[x] + state[y]) % kKeyDataSize;
buffer[counter] ^= state[xor_index];
}
key_.x = x;
key_.y = y;
}
Rc4Key key_;
};
} // namespace autofill
#endif // COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
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