The Shibboleth SP does not have an application API per se, but the SessionInitiator mechanism supports a simple redirect protocol capable of triggering, and influencing, the creation of authentication requests.

Initiator Protocol

This protocol supports a small set of query string parameters that correspond to identically named attributes that can be supplied either directly on a <SessionInitiator> element or as content settings on a per-resource basis.

When a query string parameter is used, it overrides any other source of the same setting/property.

Not all SessionInitiator handlers support all the possible parameters. In fact, most are specific to the SAML2 handler. Unsupported parameters are ignored.


The redirection examples shown are illustrated by way of the HTTP Location header that would be returned to a client by an application. Refer to your programming environment's documentation for information on how to generate redirects and produce such a header. Note that you should always be sure to URL-encode any parameter values that you append.

The examples also assume that a SessionInitiator exists at the location "/Login", which is the usual default.

The most common scenario is to simply ask for a login while providing a resource to return the client to afterwards. Typically, this is the resource from which the redirect is generated.


Another common case is to specify the IdP to use. This is a simple way to implement user selection of an IdP from among a small set, for example clicking on a choice of logos. Not coincidentally, the SAMLDS handler is implemented by routing the result of the discovery process back to itself with the entityID parameter set.