External authentication on a different system than the IdP

[Peter Schober]

* Ian Rifkin <irifkin at brandeis.edu> [2013-07-24 18:44]:
> > 2.) Redirect to IdP.
> >
> 
> Redirected to IdP server, but doesn't reach the actual IdP yet…
> 
> 
> > 3.) External auth handler takes over.
> >
> 
> Yes, this is where mod_cosign comes into play for me

You are *not* describing the ExternalAuthn login handler here (which
is the topic at hand), you're talking about the RemoteUser login
handler. While that also allows to "externalize" authentication the
implementation and the flows talked about above are very different.
-peter