Restrict Login Email with Google OAuth2.0 to Specific Domain Name

Solution 1:

So I've got an answer for you. In the oauth request you can add "hd=domain.com" and it will restrict authentication to users from that domain (I don't know if you can do multiple domains). You can find hd parameter documented here

I'm using the google api libraries from here: http://code.google.com/p/google-api-php-client/wiki/OAuth2 so I had to manually edit the /auth/apiOAuth2.php file to this:

public function createAuthUrl($scope) {
    $params = array(
        'response_type=code',
        'redirect_uri=' . urlencode($this->redirectUri),
        'client_id=' . urlencode($this->clientId),
        'scope=' . urlencode($scope),
        'access_type=' . urlencode($this->accessType),
        'approval_prompt=' . urlencode($this->approvalPrompt),
        'hd=domain.com'
    );

    if (isset($this->state)) {
        $params[] = 'state=' . urlencode($this->state);
    }
    $params = implode('&', $params);
    return self::OAUTH2_AUTH_URL . "?$params";
}

Edit: I'm still working on this app and found this, which may be the more correct answer to this question. https://developers.google.com/google-apps/profiles/

Solution 2:

Client Side:

Using the auth2 init function, you can pass the hosted_domain parameter to restrict the accounts listed on the signin popup to those matching your hosted_domain. You can see this in the documentation here: https://developers.google.com/identity/sign-in/web/reference

Server Side:

Even with a restricted client-side list you will need to verify that the id_token matches the hosted domain you specified. For some implementations this means checking the hd attribute you receive from google after verifying the token.

Full Stack Example:

Web Code:

gapi.load('auth2', function () {
    // init auth2 with your hosted_domain
    // only matching accounts will show up in the list or be accepted
    var auth2 = gapi.auth2.init({
        client_id: "your-client-id.apps.googleusercontent.com",
        hosted_domain: 'your-special-domain.com'
    });

    // setup your signin button
    auth2.attachClickHandler(yourButtonElement, {});

    // when the current user changes
    auth2.currentUser.listen(function (user) {
        // if the user is signed in
        if (user && user.isSignedIn()) {
            // validate the token on your server,
            // your server will need to double check that the
            // `hd` matches your specified `hosted_domain`;
            validateTokenOnYourServer(user.getAuthResponse().id_token)
                .then(function () {
                    console.log('yay');
                })
                .catch(function (err) {
                    auth2.then(function() { auth2.signOut(); });
                });
        }
    });
});

Server Code (using googles Node.js library):

If you're not using Node.js you can view other examples here: https://developers.google.com/identity/sign-in/web/backend-auth

const GoogleAuth = require('google-auth-library');
const Auth = new GoogleAuth();
const authData = JSON.parse(fs.readFileSync(your_auth_creds_json_file));
const oauth = new Auth.OAuth2(authData.web.client_id, authData.web.client_secret);

const acceptableISSs = new Set(
    ['accounts.google.com', 'https://accounts.google.com']
);

const validateToken = (token) => {
    return new Promise((resolve, reject) => {
        if (!token) {
            reject();
        }
        oauth.verifyIdToken(token, null, (err, ticket) => {
            if (err) {
                return reject(err);
            }
            const payload = ticket.getPayload();
            const tokenIsOK = payload &&
                  payload.aud === authData.web.client_id &&
                  new Date(payload.exp * 1000) > new Date() &&
                  acceptableISSs.has(payload.iss) &&
                  payload.hd === 'your-special-domain.com';
            return tokenIsOK ? resolve() : reject();
        });
    });
};