.netkerberosntlmnegotiatewww-authenticate

How to find if NTLM or Kerberos is used from WWW-Authenticate: Negotiate header

I am programming a client application in .Net that communicates with server via HTTP.

I need to set different request buffering options in case of NTLM and Kerberos authorization.

How to find out if NTLM or Kerberos is used? Is it possible to somehow decode 'WWW-Authenticate: Negotiate' header?

Solution

  • You will find answer here.

    Short answer is:

    1.Capture some successfully authorized request using Fiddler tool.
2.Choose "Inspectors" -> "Headers" tab.
3.Pay attention at "Cookies / Login" section, "Authorization" header.

    If the Authorization token begins with "YII" then Kerberos is used, but if it begins with "TlR" then Kerberos is not used.

    For example Kerberos:

    Authorization: Negotiate YIIVDAYGKwYBE...

    Not Kerberos:

    Authorization: Negotiate TlRMTVNTUA...