Google / OAuth 2 - Automatic logon

I'm playing a bit with OAuth 2.0 in combination with some Google API. Although the authorization process is quite easy, I'm facing a problem with the automatic authorization after the initial authorization has been completed.

So:

1. Authorization is done for the first time. (user grants access, I get the token etc etc)
2. User exits the application
3. User starts the application again
4. How to logon automatically here?

At point 4, I do have a refresh_token so I should just request a new token using that request_token. But I still keep getting 401 Unauthorized results on my calls.

So what I try to do is that my application can logon silently so that the user doesn't have to grant access every time.

Solution

You should be able to refresh OAuth 2.0 token using the following request:

POST /o/oauth2/token HTTP/1.1
Host: accounts.google.com
Content-Type: application/x-www-form-urlencoded

client_id=21302922996.apps.googleusercontent.com&
client_secret=XTHhXh1SlUNgvyWGwDk1EjXB&
refresh_token=1/6BMfW9j53gdGImsixUH6kU5RsR4zwI9lUVX-tqf8JXQ&
grant_type=refresh_token

As pointed in Google OAuth 2.0 documentation.

I just tried it out using curl and it works as expected:

curl -d client_id=$CLIENT_ID -d client_secret=$CLIENT_SECRET -d refresh_token=$REFRESH_TOKEN -d grant_type=refresh_token https://accounts.google.com/o/oauth2/token

{"access_token":"$ACCESS_TOKEN","token_type":"Bearer","expires_in":3600}