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Invoking UCTrust and InCommon Applications without WAYF Processing

This document describes how to invoke a UCTrust / InCommon Service Provider (SP) without "Where Are You From" (WAYF) processing when the user's campus Identity Provider (IdP) is already known.

The general approach is to invoke the IdP with query string parameters attached to its URL specifying information about the desired SP, as if the IdP had been invoked by the InCommon WAYF. For example, the following URL (with spaces and line breaks removed) could be used by a member of the UCLA community to access the QA instance of At Your Service Online (AYSO).

   https://shb.ais.ucla.edu/shibboleth-idp/SSO?
           shire=https://sseqa.ucop.edu/Shibboleth.sso/SAML/POST&
           target=https://sseqa.ucop.edu/ayso/shibboleth.do&
           providerId=https://sseqa.ucop.edu

The general format of such a URL is:

   IdP_singleSignOnService_Location?
           shire=SP_assertionConsumerService_Location&
           target=SP_Entry_Point&
           providerId=SP_entityDescriptor_entityID

The four query string parameters here are taken from the InCommon metadata for the SP being invoked, as well as the campus's IdP:

  • IdP_singleSignOnService_Location is the Location attribute of the <singleSignOnService> object within the IdP's <entityDescriptor>.
  • SP_assertionConsumerService_Location is the Location attribute of the assertionConsumerService object within the SP's <entityDescriptor>.
  • SP_entry_Point is the URL to which the user's browser should be redirected to invoke the application after the user has been authenticated by the IdP. It does not appear in the InCommon metadata.
  • SP_entityDescriptor_entityID is the entityID attribute of the SP's <entityDescriptor>.

Some considerations:

  • In the long run, it will not be possible for campuses to prepare special links for all Shibboleth-based applications. Campuses should consider if/when their community should become accustomed to interacting with the WAYF.
  • Campus web pages containing these links will likely be discoverable from other campuses via search services like Google, potentially causing confusion for the people who discover those links.  Care should be taken to make the link's text explicit about its purpose. For example, Login to AYSO with your uCInetID or AYSO (UCSC only) would be better than just AYSO.
  • A good tip is to create a short alias URL for this lengthy URL.  The short URL is easier to remember and type, and it provides a single update point if it becomes necessary to modify any of the parameters in the future.
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