Sandbox the component updater's patcher utility process.

courgette/third_party/bsdiff/bsdiff_apply.cc

 // Copyright 2003, 2004 Colin Percival
 // All rights reserved
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted providing that the following conditions
 // are met:
 // 1. Redistributions of source code must retain the above copyright
 //    notice, this list of conditions and the following disclaimer.
 // 2. Redistributions in binary form must reproduce the above copyright
 //    notice, this list of conditions and the following disclaimer in the
@@ skipping 171 matching lines @@
     return UNEXPECTED_ERROR;
 
   if (CalculateCrc(old_start, old_size) != header.scrc32)
     return CRC_ERROR;
 
   MBS_ApplyPatch(&header, patch_stream, old_start, old_size, new_stream);
 
   return OK;
 }
 
-BSDiffStatus ApplyBinaryPatch(const base::FilePath& old_file_path,
-                              const base::FilePath& patch_file_path,
-                              const base::FilePath& new_file_path) {
+BSDiffStatus ApplyBinaryPatch(base::File old_file,
+                              base::File patch_file,
+                              base::File new_file) {
   // Set up the old stream.
-  base::MemoryMappedFile old_file;
-  if (!old_file.Initialize(old_file_path)) {
+  base::MemoryMappedFile old_file_mem;
+  if (!old_file_mem.Initialize(std::move(old_file))) {
     return READ_ERROR;
   }
   SourceStream old_file_stream;
-  old_file_stream.Init(old_file.data(), old_file.length());
+  old_file_stream.Init(old_file_mem.data(), old_file_mem.length());
 
   // Set up the patch stream.
-  base::MemoryMappedFile patch_file;
-  if (!patch_file.Initialize(patch_file_path)) {
+  base::MemoryMappedFile patch_file_mem;
+  if (!patch_file_mem.Initialize(std::move(patch_file))) {
     return READ_ERROR;
   }
   SourceStream patch_file_stream;
-  patch_file_stream.Init(patch_file.data(), patch_file.length());
+  patch_file_stream.Init(patch_file_mem.data(), patch_file_mem.length());
 
   // Set up the new stream and apply the patch.
   SinkStream new_sink_stream;
   BSDiffStatus status =
       ApplyBinaryPatch(&old_file_stream, &patch_file_stream, &new_sink_stream);
   if (status != OK) {
     return status;
   }
 
   // Write the stream to disk.
-  int written = base::WriteFile(
-      new_file_path, reinterpret_cast<const char*>(new_sink_stream.Buffer()),
+  int written = new_file.Write(
+      0,
+      reinterpret_cast<const char*>(new_sink_stream.Buffer()),
       static_cast<int>(new_sink_stream.Length()));
   if (written != static_cast<int>(new_sink_stream.Length()))
     return WRITE_ERROR;
   return OK;
 }
 
+BSDiffStatus ApplyBinaryPatch(const base::FilePath& old_file_path,
+                              const base::FilePath& patch_file_path,
+                              const base::FilePath& new_file_path) {
+  return ApplyBinaryPatch(
+      base::File(
+          base::FilePath(old_file_path),
+          base::File::FLAG_OPEN | base::File::FLAG_READ),
+      base::File(
+          base::FilePath(patch_file_path),
+          base::File::FLAG_OPEN | base::File::FLAG_READ),
+      base::File(
+          base::FilePath(new_file_path),
+          base::File::FLAG_CREATE_ALWAYS |
+              base::File::FLAG_WRITE |
+              base::File::FLAG_EXCLUSIVE_WRITE));
+}
+
 }  // namespace bsdiff