App Lab 3rd party login

Question about App Lab requirements.  Can I require a user to login with credentials in order to access the application's main features, or is that outside the app lab submission guidelines.  I've read through them all, but haven't been able to find clarity on the subject.

Hypothetical Flow would be

1. User opens application

2. User is placed into a lobby 

3. User much input credentials from 3rd party software to access application

4. (If no credentials are present, user can create an account from the lobby)