Is there a detailed guide for using Siteminder with Tomcat .I searched over Google and SO most of the questions were unanswered for this.
Here's the direct link to the Tomcat and JBoss application server agent download with pdf.
or you can search on "CA SiteMinder Application Server Agent for Tomcat" on their support site.
-also-
Here's an open source implementation, although it appears to be based on filters and not Valves which it probably should be.
https://web.archive.org/web/20150405034132/http://www.tony007.com/netegrity.htm
You could write your own JAAS provider. I've done this before and it's not too hard. ( see http://www.kopz.org/public/documents/tomcat/jaasintomcat.html )
I've also written a custom Valve implementation as well for integrating with a different SSO system. It's not as straightforward and i had issues in geronimo with class loading.