Enumerate Windows of user desktop on another session

Question

I've a simple question here that is driving me crazy.

I have a windows service in C# which should work on XP, Vista and 7 and be able to enumerate windows of the current user's desktop (if any) for monitoring purposes.

So far :

I have used EnumDesktopWindows passing IntPtr.Zero as the hdesktop parameter because I don't have the handle to user's desktop which results only in enumerating a handful of windows that exist in special desktop which allocated for services (Session0\Winsta0)

I tried EnumWindows, same results as above!

I tried to get Desktop of a known process using GetThreadDesktop API, passing id of one of explorer.exe's threads but it returns 0, so I can't get it's desktop or any other's.

I tried to get input desktop using OpenInputDesktop which apparently returns the desktop inside session0 not desktop of user.

What can I do?!

If you're curious, I'm writing a kiosk application which needs to monitor all windows and prevent dangerous ones like task manager, Internet Options, Cmd, and in general anything that a user should not open.

Any suggestions are welcome. :)

Answer 1

You cannot, without exception, enumerate windows in a another session. You can, on the other hand, create a process in another session if you have the "Act as part of the operating system" (SeTcbPrivilege) Privilege.

See Launching a process in user’s session from a service for how that can be done.

You can end up with two processes, a controller which runs as an NT Service, and the agent which runs in the user's session. The two processes can communicate via a named pipe, with the controller restarting the agent if killed by the user.

You should also be using group policy or other configuration to lock down the client to prevent the other windows from opening in the first place, however. Specifically, Software Restriction Policies will allow you to prevent a non-whitelisted executable from ever running.

If you are using Windows 8.1, you can also use the newly introduced Kiosk Mode.