Access to external window handles

Question

I am having a problem with the program I am currently working on. It is caused by the increased security in vista/Windows 7, specifically the UIPI which prevents a window with a lower integrity level 'talking' to a higher one.

In my case, i am wanting to tell the window with a high Integrity level to move into our application, It works flawlessly on XP or windows 7 with the security off.

I have tried setting the HWND of the higher IL window directly, rather than using the findwindow() function, this works fine but the program then fails when trying to move it or generally interact with it. The windowhandle is saved by the app to be embedded and read by the app running at a lower IL.

I have also tried setting UIaccess in the manifest to TRUE and digitally signing the program but no luck.

Any ideas on how to solve this problem? thanks.

Answer 1

Just thought i would follow this up for anyone who also struggled as I have finally found a way to do this.

IL = Integrity Level.

I had 2 apps, highIL.exe and lowIL.exe, the highIL wanted to find the lowIL.exe window, set it as a child window and move it into a zone created for it on the highIL.exe. This was blocked by the UIPI in vista+.

In the end i used the ChangeWindowMessageFilter method in vista and the ChangeWindowMessageFilterEx in Windows7, both found in the user32.dll. These functions allow you to poke a hole in the UIPI to allow messages that you want through.

I created a few custom messages using RegisterWindowMessage function, I used this function to register the method in both highIL and lowIL applications, the line looked a little like this:

const UINT MY_MOVEINTWINDOW_MSG = RegisterWindowMessage(_T("MyMsg.MoveWindow"));

The lowIL.exe is then able to send these messages to the highIL.exe window without them being blocked. Then it was a case of just simply adding and writing message handlers.

This method will only work if you have access to both the high and low IL. The MSDN also has a working example of the ChangeWindowMessageFilterEx function on there Website