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Writing your own logonui.exe


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It has to be possible to write your own logonui.exe (XP Welcome Screen) for Windows XP, but the question is how? I've determined that when you go to log off or switch user, XP calls the executable with the /status parameter (I did this by writing my own that shows a message box of the command line parameters). If the application exits prematurely, Windows calls it again and continues to do so with the same switch.. If you close it too fast too many times, it will just show the classic login screen (probably because it thinks theres an error causing logonui.exe to crash). So... I tried to invoke the login screen by using a normal logonui.exe and using the /status parameter.. but nothing happens. I think logonui.exe has to run as SYSTEM instead of the currently logged in user and thats why its exiting.. How would I run it as SYSTEM? "runas /user:SYSTEM "logonui.exe /status"" asks for a password for SYSTEM.. Is there anything that lets me see more under the hood of what applications (logonui.exe) are doing (writing files, passing parameters, whats being passed to them, etc)? This would give me a big start on this..

The advantages of being able to write your own logonui.exe would be tremendous. As XP has been out for some time now, I think it's about time someone cracked this.. I couldn't find any information on Google though..

Edit: I would post in the boot and login screens forum, but it's not very active and I figured I'd get better responses here (programmers tend to know how stuff works internally better.. or how to figure out how it works)...

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Actually, I think changing/modifying the files breaks the EULA, but in this case you would change a registry entry that redirects the logon screen to a different executable.

For example, by default, the value of the entry is set to "logonui.exe" and C:\WINDOWS\System32\logonui.exe is used.. but if you change the value to say "customlogon.exe" and create your own exe from scratch.. I don't see anything wrong with that..

and like Relativity said.. it's not any worse than hacking uxtheme.dll (or other system files such as tcpip.sys)

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There's a tool that might be of use here to figure out the internals of logonui. It's called Dependency Walker and it allows you to see what functions the program (or dll) imports. It might help you to figure out how logonui does the actual logging in.

I think your idea's a great one. It sure as hell hasen't been done before. I thought about doing this as well, but I didn't bother trying since I know zero about win32api.

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It is possible to write your own msigina.dll (documented in msdn). It will let you control all messages (logon, "applying security settings", etc...) and allows you to replace the classic ctrl+alt+del screen (lock computer, etc...). Not sure if this is exactly what you are looking for though.

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holy **** u guys are freaks. do you honestly care if he mods the logonui, or do u think microsoft is gonna crack down on him and file a lawsuit?

he's not talking about modding logonui. He's talking about making a brand new one from scratch.

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