Authentication issues with WWW-Authenticate: Negotiate

I am trying to access a site that is password protected. It is not using basic authentication (even though the same user/pass box pops up in firefox) as the response header is WWW-Authenticate: Negotiate.

I want to automate the login process by sending the correct header.

In basic you would use something like:

Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==

What would I use for negotiate?

The web server is prompting you for a SPNEGO (Simple and Protected GSSAPI Negotiation Mechanism) token.

This is a Microsoft invention for negotiating a type of authentication to use for Web SSO (single-sign-on):

• either NTLM
• or Kerberos.

See:

• Microsoft MSDN Library: HTTP-Based Cross-Platform Authentication by Using the Negotiate Protocol
• RFC 4178: The Simple and Protected Generic Security Service Application Program Interface (GSS-API) Negotiation Mechanism