The SSO gateway is a web application (ssogateway.war) and it contains a web service resposible with sso token generation/deletion
The stub classes are packaged in sso-bindings.jar (located also in lib directory)
For more details please visit this link :
http://list.sipfoundry.org/archive/sipx-dev/msg08807.html
I also added --enable-sso in order to make sso token generation configurable