You can configure authentication services with external OAuth suppliers, right now Twitter, Facebook and Google are supported.

1. Create an App on the platform

For each platform, go to their developers section and follow their guides to create an app.

2. Set your CONSUL's url

They'll ask you for your CONSUL's auth URL, and as you can see running rake routes at your CONSUL repo locally:
user_omniauth_authorize GET|POST /users/auth/:provider(.:format) users/omniauth_callbacks#passthru {:provider=>/twitter|facebook|google_oauth2/}
So for example the URL for facebook application would be

3. Set key & secret values

When you complete the application registration you'll get a key and secret values, those need to be stored at your config/secrets.yml file:
twitter_key: ""
twitter_secret: ""
facebook_key: ""
facebook_secret: ""
google_oauth2_key: ""
google_oauth2_secret: ""
NOTE: Also in the case of Google, verify that the APIs Contacts API and Google+ API are enabled for the application.