1    :  // Copyright 2012 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #include "syzygy/common/path_util.h"
  16    :  
  17    :  #include <windows.h>
  18    :  
  19    :  #include "base/logging.h"
  20    :  #include "syzygy/common/com_utils.h"
  21    :  
  22    :  namespace common {
  23    :  
  24    :  bool ConvertDevicePathToDrivePath(const base::FilePath& device_path,
  25  E :                                    base::FilePath* drive_path) {
  26  E :    DCHECK(drive_path != NULL);
  27    :    static const wchar_t kPathSeparator = L'\\';
  28    :  
  29    :    // Get the set of logical drives that exist as a bitmask.
  30  E :    DWORD drive_bits = ::GetLogicalDrives();
  31    :  
  32    :    // For each logical drive get the device name, looking for one that
  33    :    // matches the prefix of device_path.
  34  E :    DWORD drive_bit = 1;
  35  E :    wchar_t drive_letter = L'A';
  36  E :    wchar_t drive[] = { 'A', ':', 0 };
  37  E :    for (; drive_bit != 0; drive_bit <<= 1, ++drive_letter) {
  38    :      // If the bit is not set, this drive does not exist.
  39  E :      if ((drive_bits & drive_bit) == 0)
  40  E :        continue;
  41    :  
  42    :      // Generate the drive name.
  43  E :      drive[0] = drive_letter;
  44    :  
  45    :      // The call to QueryDosDevice is racy, as the system state may have changed
  46    :      // since we called GetLogicalDriveStrings. So on failure we simply log a
  47    :      // warning and continue on our merry way.
  48  E :      wchar_t device[1024] = { 0 };
  49  E :      DWORD device_length = ::QueryDosDevice(drive, device, arraysize(device));
  50  E :      if (device_length == 0) {
  51  i :        DWORD error = ::GetLastError();
  52  i :        LOG(WARNING) << "QueryDosDevice failed: " << common::LogWe(error);
  53  i :      } else {
  54    :        // The string that QueryDosDevice writes is terminated with 2 nulls.
  55  E :        DCHECK_GT(device_length, 2u);
  56  E :        device_length -= 2;
  57  E :        DCHECK_EQ(device_length, ::wcslen(device));
  58    :  
  59    :        // Is this the device we're looking for?
  60  E :        if (_wcsnicmp(device, device_path.value().c_str(), device_length) == 0) {
  61    :          // The device path must consist only of the device name, or must be
  62    :          // immediately followed by a path separator. This prevents matching
  63    :          // "\Device\HarddiskVolume10" with "\Device\HarddiskVolume1".
  64    :          if (device_path.value().size() == device_length ||
  65  E :              device_path.value()[device_length] == kPathSeparator) {
  66    :            // Replace the device name with the drive letter and return the
  67    :            // translated path.
  68    :            *drive_path = base::FilePath(drive).Append(
  69  E :                device_path.value().substr(device_length));
  70  E :            return true;
  71    :          }
  72    :        }
  73    :      }
  74  E :    }
  75    :  
  76    :    // We didn't find a matching device.
  77  E :    *drive_path = device_path;
  78  E :    return true;
  79  E :  }
  80    :  
  81    :  }  // namespace common