Don't allow path traversal paths on the base file helpers

base/platform_file.h

 // 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.
 
 #ifndef BASE_PLATFORM_FILE_H_
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 102 matching lines @@
   base::Time last_accessed;
 
   // The creation time of a file.
   base::Time creation_time;
 };
 
 // Creates or opens the given file. If |created| is provided, it will be set to
 // true if a new file was created [or an old one truncated to zero length to
 // simulate a new file, which can happen with PLATFORM_FILE_CREATE_ALWAYS], and
 // false otherwise.  |error_code| can be NULL.
+//
+// This function fails with 'access denied' if the |name| contains path
+// traversal components.
 BASE_EXPORT PlatformFile CreatePlatformFile(const FilePath& name,
                                             int flags,
                                             bool* created,
                                             PlatformFileError* error_code);
 
+// Same as CreatePlatformFile but allows paths with traversal (like \..\)
+// components. Use only with extreme care.
+BASE_EXPORT PlatformFile CreatePlatformFileAllowTraversal(
+    const FilePath& name, int flags, bool* created,

[brettw, 2013/01/07 20:50:26]

Can you horizontally align the params on different lines like the other one
does?

+    PlatformFileError* error_code);
+
 // Closes a file handle. Returns |true| on success and |false| otherwise.
 BASE_EXPORT bool ClosePlatformFile(PlatformFile file);
 
 // Changes current position in the file to an |offset| relative to an origin
 // defined by |whence|. Returns the resultant current position in the file
 // (relative to the start) or -1 in case of error.
 BASE_EXPORT int64 SeekPlatformFile(PlatformFile file,
                                    PlatformFileWhence whence,
                                    int64 offset);
 
@@ skipping 85 matching lines @@
     return temp;
   }
 
  private:
   PlatformFile* value_;
 };
 
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_