Suggest you look at the Facebook Connect module instead
One of the better FB integration modules I've seen; I poked quicksketch to take this thing from sandbox to module, and he's done a great job of porting the module and responding to maintenance queries. The code is simple and easy to work with. I did a rough port to D7, which you can find in the issues queue. I'm sure you could rig it to automatically register visitors, although they will still have to grant permission for whatever data you desire through FB. I'm sure you've already checked it out, but the FB documentation will fill you in on the general concepts related to Facebook authorization.
The OAuth Connector module for Drupal 7 claims to be supporting signing up and logging in through OAuth 2 API:s in general and also to support Facebook specifically.
As it is said on a previous post, OAuth Connector may do the job. You have a nice tutorial here http://fuseinteractive.ca/blog/how-allow-facebook-logins-your-drupal-site .
Using Janrain Engage, Drupal sites can authenticate new and existing users with popular social networks, map user profile data from these websites to Drupal fields, and share Drupal content with a user's friends on their social networks.
Here's a quick summary of some notable features:
LOGIN AND REGISTRATION: Allow site visitors to register and login with one of their existing accounts at popular social networks such as Facebook, Google, Yahoo!, Twitter and LinkedIn. Support is included for both the Drupal user login block and the user login page. Quickly and easily converting anonymous site visitors into active registered users.
DATA MAPPING: With permission of the user, you can map a user's social profile data to specific Drupal fields. A variety of fields are supported, including User fields, old-style core Profile fields (for those upgrading from Drupal 6), and Profile2 contributed module fields.
IMPORT PROFILE PICTURE: Import profile photos from a user's social network account and use it as the Drupal profile picture.
SOCIAL SHARING: Make it easy for users to share their Drupal content and comments with friends and followers on other social networks. A "Share" button or link may be included on specific content types, which triggers the Janrain Engage social sharing widget. When a user submits a comment, this widget can be automatically triggered (suggesting to the user that he/she should share the comment).
LINKED ACCOUNT MANAGEMENT: A "Linked accounts" tab is provided to the end user (who has the appropriate module permission). Using this tab, a user can add, remove, or otherwise manage the social network accounts connected to his/her Drupal site account.
INTEGRATION: For those using the popular Rules module, you can configure the full range of Rules-based actions to occur (change a role, send an e-mail, etc.) whenever a user adds or removes a linked account via Janrain Engage. You can also configure the Janrain Engage social sharing widget to launch on various Rule-based events.
VIEWS INTEGRATION: If you use the Views module, you can easily create various views that include such data as linked account ID's, provider information and icon, as well as a link to delete the account. These can be used, for example, to create site-wide analytics about the number of linked accounts of a given type that have been created.
CAPTCHA INTEGRATION: Now you can use any of the popular captcha modules (Mollom, Captcha and its submodules) alongside Janrain Engage. While regular sign-ups will still be required to go through captcha verification, sign-ups via Engage will be automatic.
I tried the Oauth Connector Module but could not get it to work. At the time of this comment, the Oauth Connector module had no commits since Oct 2013 (2 years ago). So, I went with the HybridAuth Social Login module which is currently very actively maintained and it just worked without any hassle.
Taken from the project page:
HybridAuth Social Login integrates HybridAuth library into Drupal and allows your users to login and register using:
- Windows Live
- Github, LastFM, PayPal, Vimeo, Disqus, Instagram, Tumblr, Vkontakte, Mail.ru, Yandex, Odnoklassniki, Twitch.tv, Steam and more