components/os_crypt/ie7_password_win.cc

   1 // Copyright 2014 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 #include "components/os_crypt/ie7_password_win.h"
   6
   7 #include <string>
   8 #include <vector>
   9
  10 #include "base/memory/scoped_ptr.h"
  11 #include "base/sha1.h"
  12 #include "base/strings/string_util.h"
  13 #include "base/strings/stringprintf.h"
  14 #include "crypto/wincrypt_shim.h"
  15
  16 namespace {
  17
  18 // Structures that IE7/IE8 use to store a username/password.
  19 // Some of the fields might have been incorrectly reverse engineered.
  20 struct PreHeader {
  21   DWORD pre_header_size;  // Size of this header structure. Always 12.
  22   DWORD header_size;      // Size of the real Header: sizeof(Header) +
  23                           // item_count * sizeof(Entry);
  24   DWORD data_size;        // Size of the data referenced by the entries.
  25 };
  26
  27 struct Header {
  28   char wick[4];             // The string "WICK". I don't know what it means.
  29   DWORD fixed_header_size;  // The size of this structure without the entries:
  30                             // sizeof(Header).
  31   DWORD item_count;         // Number of entries. Should be even.
  32   wchar_t two_letters[2];   // Two unknown bytes.
  33   DWORD unknown[2];         // Two unknown DWORDs.
  34 };
  35
  36 struct Entry {
  37   DWORD offset;         // Offset where the data referenced by this entry is
  38                         // located.
  39   FILETIME time_stamp;  // Timestamp when the password got added.
  40   DWORD string_length;  // The length of the data string.
  41 };
  42
  43 // Main data structure.
  44 struct PasswordEntry {
  45   PreHeader pre_header;  // Contains the size of the different sections.
  46   Header header;         // Contains the number of items.
  47   Entry entry[1];        // List of entries containing a string. Even-indexed
  48                          // are usernames, odd are passwords. There may be
  49                          // several sets saved for a single url hash.
  50 };
  51 }  // namespace
  52
  53 namespace ie7_password {
  54
  55 bool GetUserPassFromData(const std::vector<unsigned char>& data,
  56                          std::vector<DecryptedCredentials>* credentials) {
  57   const PasswordEntry* information =
  58       reinterpret_cast<const PasswordEntry*>(&data.front());
  59
  60   // Some expected values. If it's not what we expect we don't even try to
  61   // understand the data.
  62   if (information->pre_header.pre_header_size != sizeof(PreHeader))
  63     return false;
  64
  65   const int entry_count = information->header.item_count;
  66   if (entry_count % 2)  // Usernames and Passwords
  67     return false;
  68
  69   if (information->header.fixed_header_size != sizeof(Header))
  70     return false;
  71
  72   const uint8* offset_to_data = &data[0] +
  73                                 information->pre_header.header_size +
  74                                 information->pre_header.pre_header_size;
  75
  76   for (int i = 0; i < entry_count / 2; ++i) {
  77
  78     const Entry* user_entry = &information->entry[2*i];
  79     const Entry* pass_entry = user_entry+1;
  80
  81     DecryptedCredentials c;
  82     c.username = reinterpret_cast<const wchar_t*>(offset_to_data +
  83                                                   user_entry->offset);
  84     c.password = reinterpret_cast<const wchar_t*>(offset_to_data +
  85                                                   pass_entry->offset);
  86     credentials->push_back(c);
  87   }
  88   return true;
  89 }
  90
  91 std::wstring GetUrlHash(const std::wstring& url) {
  92   std::wstring lower_case_url = base::StringToLowerASCII(url);
  93   // Get a data buffer out of our std::wstring to pass to SHA1HashString.
  94   std::string url_buffer(
  95       reinterpret_cast<const char*>(lower_case_url.c_str()),
  96       (lower_case_url.size() + 1) * sizeof(wchar_t));
  97   std::string hash_bin = base::SHA1HashString(url_buffer);
  98
  99   std::wstring url_hash;
 100
 101   // Transform the buffer to an hexadecimal string.
 102   unsigned char checksum = 0;
 103   for (size_t i = 0; i < hash_bin.size(); ++i) {
 104     // std::string gives signed chars, which mess with StringPrintf and
 105     // check_sum.
 106     unsigned char hash_byte = static_cast<unsigned char>(hash_bin[i]);
 107     checksum += hash_byte;
 108     url_hash += base::StringPrintf(L"%2.2X", static_cast<unsigned>(hash_byte));
 109   }
 110   url_hash += base::StringPrintf(L"%2.2X", checksum);
 111
 112   return url_hash;
 113 }
 114
 115 bool DecryptPasswords(const std::wstring& url,
 116                       const std::vector<unsigned char>& data,
 117                       std::vector<DecryptedCredentials>* credentials) {
 118   std::wstring lower_case_url = base::StringToLowerASCII(url);
 119   DATA_BLOB input = {0};
 120   DATA_BLOB output = {0};
 121   DATA_BLOB url_key = {0};
 122
 123   input.pbData = const_cast<unsigned char*>(&data.front());
 124   input.cbData = static_cast<DWORD>((data.size()) *
 125                                     sizeof(std::string::value_type));
 126
 127   url_key.pbData = reinterpret_cast<unsigned char*>(
 128                       const_cast<wchar_t*>(lower_case_url.data()));
 129   url_key.cbData = static_cast<DWORD>((lower_case_url.size() + 1) *
 130                                       sizeof(std::wstring::value_type));
 131
 132   if (CryptUnprotectData(&input, NULL, &url_key, NULL, NULL,
 133                          CRYPTPROTECT_UI_FORBIDDEN, &output)) {
 134     // Now that we have the decrypted information, we need to understand it.
 135     std::vector<unsigned char> decrypted_data;
 136     decrypted_data.resize(output.cbData);
 137     memcpy(&decrypted_data.front(), output.pbData, output.cbData);
 138
 139     GetUserPassFromData(decrypted_data, credentials);
 140
 141     LocalFree(output.pbData);
 142     return true;
 143   }
 144
 145   return false;
 146 }
 147
 148 }  // namespace ie7_password