This is experimental implementation of NTLMv2 written in c#. Primary use is for HTTP in cases when HttpClient does not work for whatever reason.

It is still somewhat incomplete and based on v32 https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-nlmp/

This does not depend on any particular version and it does not change HttpClient's internals (nor HttpHandler). Instead it wraps the response and in case of 401 it sets Authorization directly and tries again.

It supports plain NTLM as well as Negotiate/SPNEGO as described in https://tools.ietf.org/html/rfc455

If you want to try it, modify Program.cs with your credentials and URI and have fun. Alternatively, export CREDENTIALS='domain\user:password'.

AsnWriter was added in .NET 5.0 and it is used to write SPNEGO header. Plain NTLM should work without it e.g. be portable to older .NET version.