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Created Jun 21, 2015
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Ntlm authentication with OWIN
Install-Package Pysco68.Owin.Authentication.Ntlm
using Pysco68.Owin.Authentication.Ntlm;
// considering you already enabled cookie based authentication
// Enable NTLM authentication
// GET /account/ntlmlogin
public IHttpActionResult Ntlmlogin(string redirectUrl)
// create a login challenge if there's no user logged in!
if (this.User == null)
var ap = new AuthenticationProperties()
RedirectUri = redirectUrl
var context = this.Request.GetContext();
// this issues the NTML authentication challenge, which triggers the authentication after
// the 401 answer below (on of the next steps in the OWIN pipeline...)
context.Authentication.Challenge(ap, NtlmAuthenticationDefaults.AuthenticationType);
return Unauthorized();
return Redirect(redirectUrl);
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