Here’s a shell script I’ve created (reusing one meant for CAS protected resources), which will allow to connect to a Web application protected by the Shibboleth SSO mechanism.
It uses cURL to navigate through the various jumps required by the protocol, perform the necessary posts, etc.
I haven’t read the Shibboleth specs, so it may not be the best way, and may not work in all cases, but that was enough for my case, at least. Feel free to improve it on Github Gists.
After the connection is succesful, one may reuse the .cookieJar file to perform further cURL connections, or even some automated content mirroring with httrack, for instance (see a previous experiment of mine with httrack for Moodle).