Re: windows NTLM auth with sspi enabled fails mysteriously for some customers

On Thu, 27 Feb 2020, Zach Hall via curl-library wrote:

> build with command line option ENABLE_SSPI=yes. For our environment and the
> vast majority of our customers' environments, this hasn't caused a problem,
> However for some it causes login failures. I had one of the customers with
> this problem test logging in with a libcurl.dll built with ENABLE_SSPI=no
> installed in our install directory and they could login without issue.
>
> Any clue why this might be happening?

The primary reason we support "ENABLE_SSPI=yes" builds in addition to having
our own native NTLM implmentation is because of the existance of subtle
differences in implementations and what they support.

Unfortunately, NTLM is a tricky beast (in my humble opinion) and to figure out
the exact differences between the implementations we'd have to run two builds
with otherwise same credentials against a fixed server and try to reverse
engineeer and understand what SSPI does and compare to our own implementation.
An interesting task no doubt, but also challenging and most likely quite time
consuming.

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