There is an alternative to LogonUser. It’s documented. In fact, it’s in the
KB in some detail. (It hits a bug in NT 4.0SP6, but that may not bother
you.) If you search the KB for LogonUser, it might even jump out.
There’s Kerberos and X.509 authentication, as well.
Now, is someone paying you to solve this problem, or are you working on this
for fun? Have you ever invested any time in helping anyone else on this list
accomplish something?
While I’m a definitely marginal member of this community, I have a lot of
sympathy for the feeling that some people have expressed that there’s a
one-directional flow of information around here.
So, if someone is paying you to solve this problem, why should you expect
people to necessarily pitch in to help you for free, unless you’ve
demonstrated to share your own expertise on other people’s problems?
As an alternative: in my experience of late, opening up a $99 service
request to MS gets a remarkably high level of service, and, if you pose a
legitimate issue not covered in doc or KB, they may even refund the fee.