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Unable to set a hook to a process created in winlogon

Posted on 2004-10-18
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Last Modified: 2013-12-03
Hi,

I am having a problem not being able to hook into a process created by CreateProcess:

    STARTUPINFO si;
    PROCESS_INFORMATION pi;

    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    si.lpDesktop = "Winsta0\\Winlogon";
    ZeroMemory( &pi, sizeof(pi) );

    if(!CreateProcess( NULL,
        TEXT("Notepad.exe"),
        NULL,
        NULL,
        TRUE,
        0,
        NULL,
        NULL,
        &si,
        &pi )
    )
    return false;

    if(!g_hHook_Keyboard)
    {
      g_lpHookProc_Keyboard = (HOOKPROC) HookProcKeyboard;
      b_Success_Keyboard = (NULL != (g_hHook_Keyboard = ::SetWindowsHookEx (WH_KEYBOARD, g_lpHookProc_Keyboard, (HINSTANCE)pi.hProcess, NULL)));
    }

It returns "false" for "b_Success_Keyboard"

Any help will be appreciated..
Thanks a lot.
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Question by:ewong_111
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7 Comments
 
LVL 86

Expert Comment

by:jkr
ID: 12343463
You need to change your process'/threads window station and desktop using the appropriate APIs ('SetProcessWindowStation()'/'SetThreadDesktop()') to the one the process that you want to hook is using, otherwise it won't work.
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Author Comment

by:ewong_111
ID: 12349287
jkr..

I have inserted the follow code before the "if(!g_hHook_Keyboard)"

      HWINSTA h_Winsta = OpenWindowStation((LPCTSTR)"Winsta0", TRUE, GENERIC_ALL);
      if (!SetProcessWindowStation(h_Winsta)) AfxMessageBox("SetProcessWindowStation Failed");

      HDESK h_Desk = OpenDesktop((LPCTSTR)"Winlogon", 0, TRUE, GENERIC_ALL);
      if (!SetThreadDesktop(h_Desk)) AfxMessageBox("SetThreadDesktop Failed");

but unfortunately it still returns "false" for "b_Success_Keyboard"

      if (b_Success_Keyboard) AfxMessageBox("Success on Keyboard Hook");
      else AfxMessageBox("Failed on Keyboard Hook");

but now the AfxMessageBox is showing up in the "Winlogon" desktop now.
Any more ideas?
Thanks a lot.
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Accepted Solution

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jkr earned 500 total points
ID: 12349343
Ay, wasn't paying attention to the term 'Keyboard Hook' - you will not be allowed to install such a hook on the winlogon desktop for security reasons, since that would enable you to grab the passwords that are entered there...
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LVL 2

Author Comment

by:ewong_111
ID: 12349361
so, what kind of hook will be allowed there?
and is it true for Screen-saver also?
Thanks again..
0
 
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Expert Comment

by:jkr
ID: 12354378
Actually, what is it that you have to hook the logon desktop for? To know the purpose might help to find a suggestion around that :o)
0
 
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Author Comment

by:ewong_111
ID: 12360615
jkr,

Thanks a lot for your help, but you have already answered this question in another question I posted.
http://www.experts-exchange.com/Programming/Programming_Platforms/Win_Prog/Q_21174306.html
I guess you just have too many questions each day to answer that you didn't notice it right?
Thanks again for your motivation for helping..

:D
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Expert Comment

by:jkr
ID: 12360863
Well, I thought these were two completely separate issues :o)
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