Session 0 Isolation

Question

Vista puts out a new security preventing Session 0 from accessing hardware like the video card, and the user no longer logs into session 0. I know this means that I cannot show the user a GUI, however, does that also mean I can't show one at all? The way my code is set up right now, it would be more work to make it command line only, however if I can use my existing code and just programmatically manage the GUI it would take a lot less code.

Is this possible?

The article from MSDN says this:

• A service attempts to create a user interface (UI), such as a dialog box, in Session 0. Because the user is not running in Session 0, he or she never sees the UI and therefore cannot provide the input that the service is looking for. The service appears to stop functioning because it is waiting for a user response that does not occur.

Which makes me think it is possible to have an automated UI, but someone told me that you couldn't use SendKeys with a service because it was disabled in Session 0.

EDIT: I don't actually need to show the user the GUI

Answer 1

You can show one; it just doesn't show up.

There is a little notification in the taskbar about there being a GUI window and a way to switch to it.

Anyway, there actually is a TerminalServices API command to switch active session that you could call if you really needed it to show up.

Answer 2

You can write a separate process which provides the UI for your service process. The communication between your UI and service process can be done in various ways (search the web for "inter process communication" or "IPC").

Answer 3

Your service can have a GUI. It's simply that no human will ever see it. As the MSDN quote suggests, a service can display a dialog box. The call to MessageBox won't fail; it just won't ever return — there won't be anyone to press its buttons.

I'm not sure what you mean by wanting to "manage the GUI." Do you actually mean pretending to send input to the controls, as with SendInput? I see no reason that it wouldn't be possible; you'd be injecting input into your own program's queue, after all, and SendInput's Vista-specific warnings don't say anything about that. But I think you'd be making things much more complicated than they need to be. Revisit the idea to alter your program to have no UI at all. (That's not the same as having a console program. Consoles are UI.)

Instead of simulating the mouse messages necessary to click a button, for instance, eliminate the middle-man and simply call directly the function that the button-click event would have called.