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      1 // Copyright 2013 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 #ifndef COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
      6 #define COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
      7 
      8 #include <string>
      9 #include "base/basictypes.h"
     10 #include "base/memory/scoped_ptr.h"
     11 
     12 namespace autofill {
     13 
     14 // This is modified RC4 decryption used for import of Toolbar autofill data
     15 // only. The difference from the Crypto Api implementation is twofold:
     16 // First, it uses a non-standard key size (160 bit), not supported by Microsoft
     17 // (it supports only 40 and 128 bit for RC4). Second, it codes 128 words with
     18 // value 0x0020 at the beginning of the code to enhance security.
     19 //
     20 // This class used in
     21 // components/autofill/core/browser/autofill_ie_toolbar_import_win.cc.
     22 //
     23 // This class should not be used anywhere else!!!
     24 class RC4Decryptor {
     25  public:
     26   explicit RC4Decryptor(wchar_t const* password) {
     27     PrepareKey(reinterpret_cast<const uint8 *>(password),
     28                wcslen(password) * sizeof(wchar_t));
     29     std::wstring data;
     30     // First 128 bytes should be spaces.
     31     data.resize(128, L' ');
     32     Run(data.c_str());
     33   }
     34 
     35   // Run the algorithm
     36   std::wstring Run(const std::wstring& data) {
     37     int data_size = data.length() * sizeof(wchar_t);
     38 
     39     scoped_ptr<wchar_t[]> buffer(new wchar_t[data.length() + 1]);
     40     memset(buffer.get(), 0, (data.length() + 1) * sizeof(wchar_t));
     41     memcpy(buffer.get(), data.c_str(), data_size);
     42 
     43     RunInternal(reinterpret_cast<uint8 *>(buffer.get()), data_size);
     44 
     45     std::wstring result(buffer.get());
     46 
     47     // Clear the memory
     48     memset(buffer.get(), 0, data_size);
     49     return result;
     50   }
     51 
     52  private:
     53   static const int kKeyDataSize = 256;
     54   struct Rc4Key {
     55     uint8 state[kKeyDataSize];
     56     uint8 x;
     57     uint8 y;
     58   };
     59 
     60   void SwapByte(uint8* byte1, uint8* byte2) {
     61     uint8 temp = *byte1;
     62     *byte1 = *byte2;
     63     *byte2 = temp;
     64   }
     65 
     66   void PrepareKey(const uint8 *key_data, int key_data_len) {
     67     uint8 index1 = 0;
     68     uint8 index2 = 0;
     69     uint8* state;
     70     short counter;
     71 
     72     state = &key_.state[0];
     73     for (counter = 0; counter < kKeyDataSize; ++counter)
     74       state[counter] = static_cast<uint8>(counter);
     75 
     76     key_.x = key_.y = 0;
     77 
     78     for (counter = 0; counter < kKeyDataSize; counter++) {
     79       index2 = (key_data[index1] + state[counter] + index2) % kKeyDataSize;
     80       SwapByte(&state[counter], &state[index2]);
     81       index1 = (index1 + 1) % key_data_len;
     82     }
     83   }
     84 
     85   void RunInternal(uint8 *buffer, int buffer_len) {
     86     uint8 x, y;
     87     uint8 xor_index = 0;
     88     uint8* state;
     89     int counter;
     90 
     91     x = key_.x;
     92     y = key_.y;
     93     state = &key_.state[0];
     94     for (counter = 0; counter < buffer_len; ++counter) {
     95       x = (x + 1) % kKeyDataSize;
     96       y = (state[x] + y) % kKeyDataSize;
     97       SwapByte(&state[x], &state[y]);
     98       xor_index = (state[x] + state[y]) % kKeyDataSize;
     99       buffer[counter] ^= state[xor_index];
    100     }
    101     key_.x = x;
    102     key_.y = y;
    103   }
    104 
    105   Rc4Key key_;
    106 };
    107 
    108 }  // namespace autofill
    109 
    110 #endif  // COMPONENTS_AUTOFILL_CORE_BROWSER_CRYPTO_RC4_DECRYPTOR_H_
    111