IdP-to-IdP Federation/Proxying TO a Shibboleth IdP?

[Cantor, Scott]

Proxying to a Shibboleth IdP is...nothing special for the software. The IdP doesn't know or care what your SP is. If it's another IdP acting as an SP, that's its business.

If you're trying to get into exotic proxying control by actually identifying the services for which the proxy is acting, you're going to find that nothing much but Shibboleth implements any of that, and your proxy probably won't populate the message content that would allow even a modicum of that to be done at the Shiibboleth end.

Proxying is almost always done to hide complexity, not expose it to further control points.

-- Scott