How can I verify a Google authentication API access token?
How can I verify a Google authentication access token?
I need to somehow query Google and ask: Is [given access token] valid for the [[email protected]] Google account?
Short version:
It's clear how an access token supplied through the Google Authentication Api :: OAuth Authentication for Web Applications can be used to then request data from a range of Google services. It is not clear how to check if a given access token is valid for a given Google account. I'd like to know how.
Long version:
I'm developing an API that uses token-based authentication. A token will be returned upon provision of a valid username+password or upon provision of a third-party token from any one of N verifiable services.
One of the third-party services will be Google, allowing a user to authenticate against my service using their Google account. This will later be extended to include Yahoo accounts, trusted OpenID providers and so on.
Schematic example of Google-based access:
alt text http://webignition.net/images/figures/auth_figure002.png
The 'API' entity is under my full control. The 'public interface' entity is any web- or desktop-based app. Some public interfaces are under my control, others will not be and others still I may never even know about.
Therefore I cannot trust the token supplied to the API in step 3. This will be supplied along with the corresponding Google account email address.
I need to somehow query Google and ask: Is this access token valid for [email protected]?
In this case, [email protected] is the Google account unique identifier - the email address someone uses to log in to their Google account. This cannot be assumed to be a Gmail address - someone can have a Google account without having a Gmail account.
The Google documentation clearly states how, with an access token, data can be retrieved from a number of Google services. Nothing seems to state how you can check if a given access token is valid in the first place.
Update The token is valid for N Google services. I can't try a token against a Google service as means of verifying it as I won't know which subset of all Google's services a given user actually uses.
Furthermore, I'll never be using the Google authentication access token to access any Google services, merely as a means of verifying a supposed Google user actually is who they say they are. If there is another way of doing this I'm happy to try.
Answer
For user check, just post get the access token as accessToken and post it and get the response
https://www.googleapis.com/oauth2/v1/tokeninfo?access_token=accessToken
you can try in address bar in browsers too, use httppost and response in java also
response will be like
{
"issued_to": "xxxxxxxxxxxxx-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com",
"audience": "xxxxxxxxxxxxxxx-xxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com",
"user_id": "xxxxxxxxxxxxxxxxxxxxxxx",
"scope": "https://www.googleapis.com/auth/userinfo.profile https://gdata.youtube.com",
"expires_in": 3340,
"access_type": "offline"
}
The scope is the given permission of the accessToken. you can check the scope ids in this link
Update: New API post as below
https://oauth2.googleapis.com/tokeninfo?id_token=XYZ123
Response will be as
{
// These six fields are included in all Google ID Tokens.
"iss": "https://accounts.google.com",
"sub": "110169484474386276334",
"azp": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
"aud": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
"iat": "1433978353",
"exp": "1433981953",
// These seven fields are only included when the user has granted the "profile" and
// "email" OAuth scopes to the application.
"email": "[email protected]",
"email_verified": "true",
"name" : "Test User",
"picture": "https://lh4.googleusercontent.com/-kYgzyAWpZzJ/ABCDEFGHI/AAAJKLMNOP/tIXL9Ir44LE/s99-c/photo.jpg",
"given_name": "Test",
"family_name": "User",
"locale": "en"
}
For more info, https://developers.google.com/identity/sign-in/android/backend-auth