Wait just one minute. I have the exact same requirement and nearly the very same environment you mentioned.
I have an IIS6 server with an ISAPI filter directing all requests to a Tomcat 5.5 server.
I implemented Windows Integrated Authentication and my
test servlet that looked for
getAuthType(),
getRemoteUser() and
getUserPrincipal() always return null.
I am successfully using the Tagish JAAS module to manually authenticate form collected usernames/passwords, but when I implement a JAASRealm for the application, it is not picking up the username/password from the client (MSIE7). I continue to get null for the above mentioned servlet methods.
I am also a SharePoint admin here and I am trying to produce a similar login-scheme as that with Tomcat. I want my web server, namely Tomcat 5.5 directly or via IIS6, to pickup the client credentials when the client makes the initial request and simply identify (not necessarily authenticate) the user. I just need the username.
Help!