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LUA Buglight utility finds program failures due to limited user account bugs

Administrators are quite rightly loath to allow regular users to run applications as administrators. Most workstations are set up with a standard limited-user account, which the user logs into and runs applications from; users are not allowed to make changes to the system.

Unfortunately, some programs don't work as a limited user because of defects in their design, and will crash when invoked in a limited-user account (LUA). This is a true defect in the program's design because the vast majority of applications should not require administrative access to work correctly. (If certain aspects of the program's functionality are restricted because the user is not an admin, and the program degrades functionality gracefully, that's not a problem; that's good software engineering.)

Programmer Aaron Margosis has made LUA bugs one of his mainstay -- how they arise, how they can be avoided and how they are the responsibility of the programmer. He has written a program called

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LUA Buglight, which is now available as a public beta. Margosis designed it for systems administrators (as well as programmers)so they can determine if a given program's failure is due to an LUA error of some kind.

LUA Buglight is launched in the context of a limited user (it will not run if you are in admin account) and is designed to intercept or "shim" a number of common Windows APIs. If those APIs try to run and fail because of a privilege problem, LUA Buglight re-calls the same API in the context of an administrator and logs information about the offending API. This way, an admin can log information about a problem app -- whether it's a third-party program or something developed in-house -- and return that information to the developer for a fix. It's also a way to work around such issues in the context of a limited user.

Margosis recommends that you create a clean non-admin account to run the programs in question -- not a member of the Power Users group, not a user that was ever an administrator, but a newly created account to minimize any possible variables.

Note: The admin has to supply proper credentials to make LUA Buglight run APIs as an admin, so it can't be used as an arbitrary elevation-of-privilege attack program. Also, both the regular user and admin user accounts must have non-blank password for the program to work. Finally, LUA Buglight only runs on Windows Server 2003, XP or Vista; it does not support Windows 2000 or any earlier version of Windows.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter, which is devoted to hints, tips, tricks, news and goodies for Windows NT, Windows 2000 and Windows XP users and administrators. He has more than 10 years of Windows experience under his belt and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.

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This was first published in October 2006

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