Authentication with SAML2 assertion only

[Marek Denis]

Hi,

Taking standard mod_shib+shibd  setup into consideration I would like
to ask *if* there is any posibility for mod_shib to authenticate the
user if he presents SAML2 authN response only.
So instead of going to SP first, being redirected to the IdP,
authenticating myself with the IdP and getting back to the SP with an
assertion I would get the assertion directly from the IdP and present
it to the SP?
I am almost sure this would not work as-is. Am I right?

Also, I am insterested both in ECP and in standard websso
autentication workflows.

Thank you!

-- 
Marek Denis