Require PLATFORM_FILE_BACKUP_SEMANTICS to open a directory

base/platform_file_win.cc

 // 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 "base/platform_file.h"
 
 #include <io.h>
 
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 68 matching lines @@
   if (flags & PLATFORM_FILE_HIDDEN)
     create_flags |= FILE_ATTRIBUTE_HIDDEN;
   if (flags & PLATFORM_FILE_DELETE_ON_CLOSE)
     create_flags |= FILE_FLAG_DELETE_ON_CLOSE;
   if (flags & PLATFORM_FILE_BACKUP_SEMANTICS)
     create_flags |= FILE_FLAG_BACKUP_SEMANTICS;
 
   HANDLE file = CreateFile(name.value().c_str(), access, sharing, NULL,
                            disposition, create_flags, NULL);
 
+  if (INVALID_HANDLE_VALUE != file){

[Peter Kasting, 2014/03/14 02:23:10]

Drive-by: Please write (file != INVALID_HANDLE_VALUE).  See the "Code
formatting" section of http://dev.chromium.org/developers/coding-style .

+    // Don't allow directories to be opened without the proper flag (block ADS).
+    if (!(flags & PLATFORM_FILE_BACKUP_SEMANTICS)) {
+      BY_HANDLE_FILE_INFORMATION info = { 0 };
+      DCHECK(GetFileInformationByHandle(file, &info));

[Peter Kasting, 2014/03/14 02:23:10]

Never do real work in a DCHECK.  In non-DCHECK builds this will get compiled to
nothing, and |info| will never be initialized.

Do something like this instead:

  bool success = ...;
  DCHECK(success);

+      if (info.dwFileAttributes & (FILE_ATTRIBUTE_DIRECTORY |
+                                   FILE_ATTRIBUTE_REPARSE_POINT)) {
+        CloseHandle(file);
+        file = INVALID_HANDLE_VALUE;
+      }
+    }
+  }
+
   if (created && (INVALID_HANDLE_VALUE != file)) {
     if (flags & (PLATFORM_FILE_OPEN_ALWAYS))
       *created = (ERROR_ALREADY_EXISTS != GetLastError());
     else if (flags & (PLATFORM_FILE_CREATE_ALWAYS | PLATFORM_FILE_CREATE))
       *created = true;
   }
 
   if (error) {
     if (file != kInvalidPlatformFileValue)
       *error = PLATFORM_FILE_OK;
@@ skipping 217 matching lines @@
     case ERROR_DISK_CORRUPT:
       return PLATFORM_FILE_ERROR_IO;
     default:
       UMA_HISTOGRAM_SPARSE_SLOWLY("PlatformFile.UnknownErrors.Windows",
                                   last_error);
       return PLATFORM_FILE_ERROR_FAILED;
   }
 }
 
 }  // namespace base