ipc: Create an unforgeable mechanism to get the process id of the sender.

ipc/attachment_broker_win.cc

 // Copyright 2015 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 "ipc/attachment_broker_win.h"
 
 #include "base/process/process.h"
 #include "ipc/attachment_broker_messages.h"
 #include "ipc/brokerable_attachment.h"
 #include "ipc/handle_attachment_win.h"
 #include "ipc/ipc_sender.h"
 
 namespace IPC {
 
 AttachmentBrokerWin::AttachmentBrokerWin() {
 }
 
 AttachmentBrokerWin::~AttachmentBrokerWin() {
 }
 
 bool AttachmentBrokerWin::SendAttachmentToProcess(
     const BrokerableAttachment* attachment,
     base::ProcessId destination_process) {
   switch (attachment->GetBrokerableType()) {
     case BrokerableAttachment::WIN_HANDLE:
       const internal::HandleAttachmentWin* handle_attachment =
           static_cast<const internal::HandleAttachmentWin*>(attachment);
       internal::HandleAttachmentWin::WireFormat format =
           handle_attachment->GetWireFormat(destination_process);
-      // TODO(erikchen): Replace the call to base::Process::Current().Pid() with
-      // a non-forgeable mechanism. http://crbug.com/513431.
-      return sender_->Send(new AttachmentBrokerMsg_DuplicateWinHandle(
-          format, base::Process::Current().Pid()));
+      return sender_->Send(new AttachmentBrokerMsg_DuplicateWinHandle(format));
   }
   return false;
 }
 
 bool AttachmentBrokerWin::OnMessageReceived(const Message& msg) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(AttachmentBrokerWin, msg)
     IPC_MESSAGE_HANDLER(AttachmentBrokerMsg_WinHandleHasBeenDuplicated,
                         OnWinHandleHasBeenDuplicated)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
 }
 
 void AttachmentBrokerWin::OnWinHandleHasBeenDuplicated(
     const IPC::internal::HandleAttachmentWin::WireFormat& wire_format) {
   // The IPC message was intended for a different process. Ignore it.
   if (wire_format.destination_process != base::Process::Current().Pid())
     return;
 
   scoped_refptr<BrokerableAttachment> attachment(
       new IPC::internal::HandleAttachmentWin(wire_format));
   HandleReceivedAttachment(attachment);
 }
 
 }  // namespace IPC