How to set "current_user" in Meteor

Question

When I develop a Meteor app, I can get user's information from third party(not oauth), so how to set current_user variable without Accounts.loginWithPassword or Accounts.loginWith[Service] methods?

Accounts.createUser only return a userid,

Answer 1

I doubt this is even possible as something like this would let anyone with someone's userId log in to their account without their password.