I am sure that this is possible, since its open source and extensible
you can do just about anything you want with satchmo/django. How
familiar are you with django?
Not a complete answer but check out (in the source code) satchmo_store-
>contact->templates->registration->login.html. Thats the login form,
you could potentially add that to your index page (the default is
found here satchmo_store->shop->templates->shop->index.html and then
make the rest of the index page auth required. Hope that helps!
-Josh