NTLM handshake rejected

[haydenhancock]

What is your question? How do I properly setup Microsoft NTLM with a Microsoft .NET Framework Web API (4.6.1) that uses Windows Authentication.

What is the context? I am trying to call an API endpoint on a Microsoft .NET Framework Web API (4.6.1) using Insomnia Designer and I receive a 401.1 error. When navigating to the endpoint via the browser, it works without issues. This could be a "Pre-Authentication" issue but not entirely sure. I setup a registry entry per Microsoft documentation to disable Pre-Authentication but this did not resolve my issue. I expect it may be related to Pre-Authentication because there are two entries in the Insomnia Designer Timeline:

HTTP/1.1 401 Unauthorized
< Cache-Control: private
< Content-Type: text/html; charset=utf-8
< Server: Microsoft-IIS/10.0
< X-SourceFiles: =?UTF-8?B?QzpcUmVwb3NcRk9QU1xGT1BTV2ViQXBpXGFwaVxQb3J0Zm9saW9PcHRpbWl6YXRpb25cR2V0U2NlbmFyaW9BY3Rpdml0eU5hbWVz?=
< WWW-Authenticate: Negotiate

* NTLM handshake rejected
* Authentication problem. Ignoring this.

< WWW-Authenticate: NTLM
< X-Powered-By: ASP.NET
< Date: Thu, 28 Jan 2021 17:18:52 GMT
< Content-Length: 6250

Again, this works perfectly when calling my endpoint directly in the browser (Edge) but doesn't work in Insomnia Designer. Any advice would be much appreciated.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[dbpieter]

I am facing the same issue. Calling an NTLM protected endpoint works fine through chrome or edge. With insomnia (using same credentials) I always get a 401.

[mos379]

476