Many people have complained about not being able to get OpenSSO authentication to work with Liferay on Tomcat. It is a known issue that OpenSSO does not work with Tomcat 6.0.16 from the 6.x series. So you must use Tomcat 6.0.18 or the older 5.x versions of tomcat. This is due to cookie encoding issues.

On Tomcat 6.0.18, you need to set the cookie encoding to true by following the steps below.

1. Login to OpenSSO as amadmin
2. Goto Configuration -> Server and Sites -> <myserver> -> Security -> Cookie
3. Set  "Encode Cookie Value" to Yes

If this value is no editable, then click on "Inheritance Settings" button. Uncheck "Encode Cookie Value" from inheritance settings and save. Then go back and you should see a check box for Encode Cookie Value.

Also make sure you are using the latest Enterprise 8.0 release of OpenSSO from https://opensso.dev.java.net/public/use/index.html