Is it possible to authenticate against LDAP server without creating a drupal user account In D7 I have a section of my site I need to limit to authenticated users, but auth needs to take place against LDAP server, not drupal user base. 

My users don't have a Drupal account and I am not supposed to create one for them, I am required to just check in with the LDAP server and if TRUE, grant access to these pages, if FALSE deny access.

All the LDAP modules I have tested create a Drupal user to mirror the LDAP user, as far as I can see. And it seems to me I couldn't even really keep the user "logged in" without a Drupal account... 

What options do I have here, if any?
sorry, I guess you just can't do it that way. 

everything you do in Drupal is tied to your user, even if said user is anonymous. 

Drupal establishes a basic difference between logged and anonymous users, even if you give the latter every permission from the former. 

hence an LDAP solution involves creating Drupal users for everyone, or else they don't get to do what registered users do.