Of course I am not trying to validate just one user. But all I want to do is authenticate the token that Google has posted back on my auth endpoint and make sure 1) It has come from Google 2) Allows me to fetch a user's data (just email) so I know whose account I have to show.

I can write my own authentication using a simple username, hashed password in php easily. I just don't want my user to remember yet one more password for yet another service on the web.