if I remember correct it was a complicated fix that would definitely mess up future upgrades, but I'll try to point you down the path I took if I can remember it.
keeping people from seeing the store while not logged in is pretty simple... all you have to do is check if user is logged in at start of store.php... with some code like:
Code:
<?php if (!$SC['user']) { header( 'Location: index.php' ) ; } ?>
This will require you to use a different home page than the default store.php and redirect to it whenever user is not logged in. ( i have not used a current version of squirrelcart in years, this may have all changed)
You can include the store login box on this page with
Code:
<? include "$cart_isp_root/login.php" ?>
The tricky part came when you wanted to a let a non logged in user do things like create an account or reset a forgotten password, which all wants to happen inside the store. I built some workarounds for this but cant really remember the process. I had to hack several core files which is a nightmare for upgrades but I guess no upgrades is better than no store in the long run.
Good luck, sorry I couldn't be more helpful, but its just been too long to remember exactly what I ended up doing. If nothing else, at least you know how to check if a user is logged in or not. That should at least get you hacking and see if you can figure it out.