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

base/file_util.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.
 
 // This file contains utility functions for dealing with the local
 // filesystem.
 
 #ifndef BASE_FILE_UTIL_H_
 #define BASE_FILE_UTIL_H_
 
@@ skipping 158 matching lines @@
 // otherwise.  If either file can't be read, returns false.
 BASE_EXPORT bool ContentsEqual(const FilePath& filename1,
                                const FilePath& filename2);
 
 // Returns true if the contents of the two text files given are equal, false
 // otherwise.  This routine treats "\r\n" and "\n" as equivalent.
 BASE_EXPORT bool TextContentsEqual(const FilePath& filename1,
                                    const FilePath& filename2);
 
 // Read the file at |path| into |contents|, returning true on success.
+// This function fails if the |path| contains path traversal components ('..').
 // |contents| may be NULL, in which case this function is useful for its
 // side effect of priming the disk cache.
 // Useful for unit tests.
 BASE_EXPORT bool ReadFileToString(const FilePath& path, std::string* contents);
 
 #if defined(OS_POSIX)
 // Read exactly |bytes| bytes from file descriptor |fd|, storing the result
 // in |buffer|. This function is protected against EINTR and partial reads.
 // Returns true iff |bytes| bytes have been successfuly read from |fd|.
 BASE_EXPORT bool ReadFromFD(int fd, char* buffer, size_t bytes);
@@ skipping 430 matching lines @@
 };
 
 // Attempts determine the FileSystemType for |path|.
 // Returns false if |path| doesn't exist.
 BASE_EXPORT bool GetFileSystemType(const FilePath& path, FileSystemType* type);
 #endif
 
 }  // namespace file_util
 
 #endif  // BASE_FILE_UTIL_H_