Cómo habilitar el acceso por parte del servidor

Con el procedimiento Agregar acceso anterior, tu app solo autentica al usuario del lado del cliente; en ese caso, puedes acceder a las APIs de Google solo mientras el usuario usa activamente tu app. Si deseas que tus servidores puedan realizar llamadas a las APIs de Google en nombre de los usuarios, posiblemente mientras están sin conexión, tu servidor requiere un token de acceso.

Antes de comenzar

Cómo habilitar el acceso a la API del servidor para tu app

  1. Cuando configures el Acceso con Google, compila el objeto GoogleSignInOptions con el método requestServerAuthCode y especifica los permisos a los que debe acceder el backend de tu app con el método requestScopes.

    Pasa el ID de cliente de tu servidor al método requestServerAuthCode.

    // Configure sign-in to request offline access to the user's ID, basic
// profile, and Google Drive. The first time you request a code you will
// be able to exchange it for an access token and refresh token, which
// you should store. In subsequent calls, the code will only result in
// an access token. By asking for profile access (through
// DEFAULT_SIGN_IN) you will also get an ID Token as a result of the
// code exchange.
String serverClientId = getString(R.string.server_client_id);
GoogleSignInOptions gso = new GoogleSignInOptions.Builder(GoogleSignInOptions.DEFAULT_SIGN_IN)
        .requestScopes(new Scope(Scopes.DRIVE_APPFOLDER))
        .requestServerAuthCode(serverClientId)
        .requestEmail()
        .build();

  2. Después de que el usuario acceda correctamente, obtén un código de Auth con getServerAuthCode:

    Task<GoogleSignInAccount> task = GoogleSignIn.getSignedInAccountFromIntent(data);
try {
    GoogleSignInAccount account = task.getResult(ApiException.class);
    String authCode = account.getServerAuthCode();

    // Show signed-un UI
    updateUI(account);

    // TODO(developer): send code to server and exchange for access/refresh/ID tokens
} catch (ApiException e) {
    Log.w(TAG, "Sign-in failed", e);
    updateUI(null);
}

  3. Envía el código de Auth al backend de tu app con HTTPS POST:

    HttpPost httpPost = new HttpPost("https://yourbackend.example.com/authcode");

try {
    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(1);
    nameValuePairs.add(new BasicNameValuePair("authCode", authCode));
    httpPost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

    HttpResponse response = httpClient.execute(httpPost);
    int statusCode = response.getStatusLine().getStatusCode();
    final String responseBody = EntityUtils.toString(response.getEntity());
} catch (ClientProtocolException e) {
    Log.e(TAG, "Error sending auth code to backend.", e);
} catch (IOException e) {
    Log.e(TAG, "Error sending auth code to backend.", e);
}

  4. En el servidor de backend de tu app, intercambia el código de Auth por acceso y tokens de actualización. Usa el token de acceso para llamar a las APIs de Google en nombre del usuario y, de manera opcional, almacena el token de actualización para adquirir un token de acceso nuevo cuando venza.

    Si solicitaste acceso al perfil, también obtendrás un token de ID con la información básica del perfil del usuario.

    Por ejemplo:

    Java
    // (Receive authCode via HTTPS POST)


if (request.getHeader("X-Requested-With") == null) {
  // Without the `X-Requested-With` header, this request could be forged. Aborts.
}

// Set path to the Web application client_secret_*.json file you downloaded from the
// Google API Console: https://console.cloud.google.com/apis/credentials
// You can also find your Web application client ID and client secret from the
// console and specify them directly when you create the GoogleAuthorizationCodeTokenRequest
// object.
String CLIENT_SECRET_FILE = "/path/to/client_secret.json";

// Exchange auth code for access token
GoogleClientSecrets clientSecrets =
    GoogleClientSecrets.load(
        JacksonFactory.getDefaultInstance(), new FileReader(CLIENT_SECRET_FILE));
GoogleTokenResponse tokenResponse =
          new GoogleAuthorizationCodeTokenRequest(
              new NetHttpTransport(),
              JacksonFactory.getDefaultInstance(),
              "https://oauth2.googleapis.com/token",
              clientSecrets.getDetails().getClientId(),
              clientSecrets.getDetails().getClientSecret(),
              authCode,
              REDIRECT_URI)  // Specify the same redirect URI that you use with your web
                             // app. If you don't have a web version of your app, you can
                             // specify an empty string.
              .execute();

String accessToken = tokenResponse.getAccessToken();

// Use access token to call API
GoogleCredential credential = new GoogleCredential().setAccessToken(accessToken);
Drive drive =
    new Drive.Builder(new NetHttpTransport(), JacksonFactory.getDefaultInstance(), credential)
        .setApplicationName("Auth Code Exchange Demo")
        .build();
File file = drive.files().get("appfolder").execute();

// Get profile info from ID token
GoogleIdToken idToken = tokenResponse.parseIdToken();
GoogleIdToken.Payload payload = idToken.getPayload();
String userId = payload.getSubject();  // Use this value as a key to identify a user.
String email = payload.getEmail();
boolean emailVerified = Boolean.valueOf(payload.getEmailVerified());
String name = (String) payload.get("name");
String pictureUrl = (String) payload.get("picture");
String locale = (String) payload.get("locale");
String familyName = (String) payload.get("family_name");
String givenName = (String) payload.get("given_name");
    Python
    from apiclient import discovery
import httplib2
from oauth2client import client

# (Receive auth_code by HTTPS POST)


# If this request does not have `X-Requested-With` header, this could be a CSRF
if not request.headers.get('X-Requested-With'):
    abort(403)

# Set path to the Web application client_secret_*.json file you downloaded from the
# Google API Console: https://console.cloud.google.com/apis/credentials
CLIENT_SECRET_FILE = '/path/to/client_secret.json'

# Exchange auth code for access token, refresh token, and ID token
credentials = client.credentials_from_clientsecrets_and_code(
    CLIENT_SECRET_FILE,
    ['https://www.googleapis.com/auth/drive.appdata', 'profile', 'email'],
    auth_code)

# Call Google API
http_auth = credentials.authorize(httplib2.Http())
drive_service = discovery.build('drive', 'v3', http=http_auth)
appfolder = drive_service.files().get(fileId='appfolder').execute()

# Get profile info from ID token
userid = credentials.id_token['sub']
email = credentials.id_token['email']