I am looking for someone who can help me with authentication
I work with C#.NET 4.5

I have multiple MVC websites, 2 webapi's and a ****load of clients which are javascript based (angular2 ,vue etc etc) and apps. everything (except the apps) are hosted on azure.
I want to be able to login using social media as well, and combine logins if the email is equal to another user

I want a single sign-on implementation, it is cross platform, cross domain and preferably cross-browser (but this is optional, and I don't even know if this is possible).
any way to do this?
The person who helps me do this, I uhhh.... send you some steam credits :P
Regards,
Chris