title: How to implement Single Sign On using Spring and Active Directory
body: <p>I have a Spring based Web App which I would like to implement a Single Sign On solution on.</p>
  
  <p>The basic flow would be:</p>
  
  <p>1) User logs in into Windows Workstation/Desktop PC (authenticating against organisation's Active Directory)</p>
  
  <p>2) User opens browser and navigates to Spring Web App.</p>
  
  <p>3) Spring Web App <em>somehow</em> confirms that the user is already authenticated against AD and seamlessly lets them in. i.e. no challenge for username and password. Infact, the Spring web app would NEVER show a login form. </p>
  
  <p>Obviously it's step 3 I am having trouble with.</p>
  
  <p>I have looked at Spring Security, Kerberos, SPNEGO but I think I've just confused myself. </p>
  
  <p>If it makes a difference I am using Java 6, running on Jetty with Spring 3. The Jetty instance will be running on a *Nix machine.</p>