What is the recommended way to implement oauth / sso ?

My scenario is this:

I have my own site and I want to use Telligent as external authentication. The perfect scenario is when a user which is already logged in in Telligent navigates to my website and it's automatically logged in. The websites are sharing the domain name

What I did is this:

- I'm using .CommunityOAuthLoginUrl(returnUrl) to redirect and make the authentication

- I can check on my side that the user is already logged in in Telligent by reading a cookie - EvolutionSync

Problems :

Is this the right approach ?

How do I get the user information ? In order to make a login on my website I need some more information about the logged user. I can get the user name from the cookie, but I need email, name and some more things. I tried to get data from user.json but I keep getting (403) Forbidden even the user I use in the REST config is an admin.