Ntlm authentication with OWIN

0 install.ps1

Install-Package Pysco68.Owin.Authentication.Ntlm 

1 Config.cs

using Pysco68.Owin.Authentication.Ntlm;

// considering you already enabled cookie based authentication
// Enable NTLM authentication
app.UseNtlmAuthentication();

2 Ntlm Login Route.cs

// GET /account/ntlmlogin
[AllowAnonymous]
[Route("ntlmlogin")]
[HttpGet]
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);
}