Active Directory and group permissions

I’m trying to modify WordPress to have the following features:

1. Users are created in Active Directory and assigned to groups. Users
   can login to WordPress via Active Directory.

2. Pages can be locked
   down to only be visible to members of certain Active Directory
   groups.

3. A “Downloads” page can be seen by members of any of several
   groups but each group can only see downloads that they have been
   given permission to see (I’m flexible to how this could be represented in WordPress).

Can anyone suggest a plugin that could help? Or a list of plugins and how they could be integrated to do the above?

I’ve been playing with the following so far but was hoping there would be a simpler approach:

1. wordpress.org/plugins/active-directory-integration/ for logging in.
2. wordpress.org/plugins/user-access-manager for locking down pages to groups. I could modify this to automatically add users to groups that match their Active Directory groups when they login.
3. wordpress.org/plugins/wp-better-attachments/ for attaching downloads to a page. I could modify this to hide downloads from users based on their group but how would I associate groups to media files?