[update_engine] Fix file creation mask to be 0600

utils.cc

 // Copyright (c) 2009 The Chromium OS 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 "update_engine/utils.h"
 
 #include <sys/mount.h>
 #include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ skipping 32 matching lines @@
     return true;
   }
   return params.app_track != "buildbot-build" &&
       params.app_track != "developer-build";
 }
 
 bool WriteFile(const char* path, const char* data, int data_len) {
   DirectFileWriter writer;
   TEST_AND_RETURN_FALSE_ERRNO(0 == writer.Open(path,
                                                O_WRONLY | O_CREAT | O_TRUNC,
-                                               0666));
+                                               0600));
   ScopedFileWriterCloser closer(&writer);
   TEST_AND_RETURN_FALSE_ERRNO(data_len == writer.Write(data, data_len));
   return true;
 }
 
 bool WriteAll(int fd, const void* buf, size_t count) {
   const char* c_buf = static_cast<const char*>(buf);
   ssize_t bytes_written = 0;
   while (bytes_written < static_cast<ssize_t>(count)) {
     ssize_t rc = write(fd, c_buf + bytes_written, count - bytes_written);
@@ skipping 390 matching lines @@
   int min = value - range / 2;
   int max = value + range - range / 2;
   return base::RandInt(min, max);
 }
 
 const char* const kStatefulPartition = "/mnt/stateful_partition";
 
 }  // namespace utils
 
 }  // namespace chromeos_update_engine