By wrapping a HathiTrust handle with a single sign-on URL, it is possible to construct a link to a HathiTrust resource that automatically passes users from HathiTrust partner institutions through their institution's authentication service, effectively "automatically" logging them into HathiTrust.
URLs must be constructed in the following way:
http://hdl.handle.net/2027/$ID?urlappend=%3Bsignon=swle:$ENTITY_ID
Where $ID is the HathiTrust resource and $ENTITY_ID is your Shibboleth IDP.
For example, given the handle
http://hdl.handle.net/2027/mdp.39015015394847
...and a Shibboleth IDP
https://shibboleth.umich.edu/idp/shibboleth
...you can append the "signon" parameter to automatically pass users through your institution's Shibboleth IDP:
http://hdl.handle.net/2027/mdp.39015015394847?urlappend=%3Bsignon=swle:https://shibboleth.umich.edu/idp/shibboleth
Please contact feedback@issues.hathitrust.org with any questions or comments.