Question

I run Windows 7.
I run windows service that runs a program with GUI.
I cannot see the GUI of my program because it was started from another session by system or even my user.

Is there a way for me to see my program?
Switch desktop to system user?

Answer 1

Use SetThreadDesktop() to change the thread’s context in your service to the user’s desktop.

• SetThreadDesktop() takes a handle to the desktop as it’s first parameter; to get that handle, use EnumDesktops().
• EnumDesktops() takes a handle to the window station as it’s first parameter; to get that handle, use EnumWindowStations()

To understand what’s going on with Window Stations and Desktops, try reading this overview from from MSDN.

Be cautious with this technique. Higher-privileged processes (i.e., services) interacting with the user’s desktop are the basis for shatter attacks. You need to write a separate application that runs in the user’s context and communicates with your service via pipes or similar.