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From: esmo2000 on 11 Jul 2006 23:13
Hi everyone, I was working through the tutorial MSDN posted at
http://msdn.microsoft.com/msdnmag/issues/05/06/SecurityBriefs/ for
replacing the msgina.dll . I am trying to (like so many others) create

an automatic logon (sadly, no, I cannot use the pgina out there as
amazing as it is! And I don't have time to understand it).
Unfortunately, I am going through a lot of troubles! Here is what I
was trying to do:

I want to have a service which runs on a system account to communicate
with the gina through sockets. The service actually does a few things
(my motivations for keeping it outside of the Gina itself are
complexity and security. Right now it runs on .NET and I don't want to

introduce its vulnerabilities into the Gina for obvious reasons.).
Next, I made a thread which is created when the Gina starts to be
responsible for talking to that service. I got this to work
sucessfully, and the two communicate fine.

The next part was where I had troubles. To be consistent with the
winlogon structure, i used postmessage to post a message to the dialog
window. The end result should be that a control sequence is generated
with logon information sent. In other words, an automatic logon.
However, the postmessage always returns the error message illegal
window handle. This is being drawn write from the GinaModalDialog
class. I checked and the window handle DOES exist when I call
postmessage.

As an extreme measure, I tried testing it like this in the gina.cpp
class:

int Gina::LoggedOutSAS(DWORD dwSasType, PLUID pAuthenticationId, PSID
pLogonSid, PDWORD pdwOptions,
PHANDLE phToken, PWLX_MPR_NOTIFY_INFO
pNprNotifyInfo, PVOID* ppWinLogonProfile) {

ZeroMemory(pNprNotifyInfo, sizeof *pNprNotifyInfo);

*pdwOptions = 0; // we always let WinLogon load the user profile
for us

wchar_t* profilePath = 0;
const wchar_t* domain = 0;
const wchar_t* userName = 0;
const wchar_t* password = 0;

LogonDialog dlg(_pWinLogon);

if(PostMessage(dlg.Gethwnd(), WM_USER+0x1234, NULL, NULL) == 0)

{LDB1(L"Post message failure %d.", GetLastError());}
else {LDB(L"Post message dlgA success.");}

....

}

And as before, the error I get is 1400, invalid window handle. I can
imagine this postmessage failing in other spots, but I'm baffled why
this case could ever fail.

If anyone could help, I would be eternally grateful!

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