Mengautentikasi dengan server backend

Jika Anda menggunakan Login dengan Google dengan aplikasi atau situs yang berkomunikasi dengan backend server web, Anda mungkin perlu mengidentifikasi pengguna yang sedang masuk di server tersebut. Untuk melakukannya dengan aman, setelah pengguna berhasil login, kirim informasi ke server Anda menggunakan HTTPS. Kemudian, pada server, verifikasi integritas token ID dan menggunakan informasi pengguna yang terdapat dalam token untuk menetapkan sesi atau membuat akun baru.

Kirim token ID ke server Anda

Setelah pengguna berhasil login, dapatkan token ID pengguna:

function onSignIn(googleUser) {
  var id_token = googleUser.getAuthResponse().id_token;
  ...
}

Kemudian, kirim token ID ke server Anda dengan permintaan HTTPS POST:

var xhr = new XMLHttpRequest();
xhr.open('POST', 'https://yourbackend.example.com/tokensignin');
xhr.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xhr.onload = function() {
  console.log('Signed in as: ' + xhr.responseText);
};
xhr.send('idtoken=' + id_token);

Memverifikasi integritas token ID

Setelah menerima token ID melalui HTTPS POST, Anda harus memverifikasi integritas token kata.

To verify that the token is valid, ensure that the following criteria are satisfied:

  • The ID token is properly signed by Google. Use Google's public keys (available in JWK or PEM format) to verify the token's signature. These keys are regularly rotated; examine the Cache-Control header in the response to determine when you should retrieve them again.
  • The value of aud in the ID token is equal to one of your app's client IDs. This check is necessary to prevent ID tokens issued to a malicious app being used to access data about the same user on your app's backend server.
  • The value of iss in the ID token is equal to accounts.google.com or https://accounts.google.com.
  • The expiry time (exp) of the ID token has not passed.
  • If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can check the hd claim, which indicates the hosted domain of the user. This must be used when restricting access to a resource to only members of certain domains. The absence of this claim indicates that the account does not belong to a Google hosted domain.

Using the email, email_verified and hd fields, you can determine if Google hosts and is authoritative for an email address. In the cases where Google is authoritative, the user is known to be the legitimate account owner, and you may skip password or other challenge methods.

Cases where Google is authoritative:

  • email has a @gmail.com suffix, this is a Gmail account.
  • email_verified is true and hd is set, this is a G Suite account.

Users may register for Google Accounts without using Gmail or G Suite. When email does not contain a @gmail.com suffix and hd is absent, Google is not authoritative and password or other challenge methods are recommended to verify the user. email_verified can also be true as Google initially verified the user when the Google account was created, however ownership of the third party email account may have since changed.

Rather than writing your own code to perform these verification steps, we strongly recommend using a Google API client library for your platform, or a general-purpose JWT library. For development and debugging, you can call our tokeninfo validation endpoint.

Using a Google API Client Library

Using one of the Google API Client Libraries (e.g. Java, Node.js, PHP, Python) is the recommended way to validate Google ID tokens in a production environment.

Java

To validate an ID token in Java, use the GoogleIdTokenVerifier object. For example:

import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdToken.Payload;
import com.google.api.client.googleapis.auth.oauth2.GoogleIdTokenVerifier;

...

GoogleIdTokenVerifier verifier = new GoogleIdTokenVerifier.Builder(transport, jsonFactory)
    // Specify the WEB_CLIENT_ID of the app that accesses the backend:
    .setAudience(Collections.singletonList(WEB_CLIENT_ID))
    // Or, if multiple clients access the backend:
    //.setAudience(Arrays.asList(WEB_CLIENT_ID_1, WEB_CLIENT_ID_2, WEB_CLIENT_ID_3))
    .build();

// (Receive idTokenString by HTTPS POST)

GoogleIdToken idToken = verifier.verify(idTokenString);
if (idToken != null) {
  Payload payload = idToken.getPayload();

  // Print user identifier
  String userId = payload.getSubject();
  System.out.println("User ID: " + userId);

  // Get profile information from payload
  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");

  // Use or store profile information
  // ...

} else {
  System.out.println("Invalid ID token.");
}

The GoogleIdTokenVerifier.verify() method verifies the JWT signature, the aud claim, the iss claim, and the exp claim.

If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can verify the hd claim by checking the domain name returned by the Payload.getHostedDomain() method. The domain of the email claim is insufficient to ensure that the account is managed by a domain or organization.

Node.js

To validate an ID token in Node.js, use the Google Auth Library for Node.js. Install the library: 

npm install google-auth-library --save
 Then, call the verifyIdToken() function. For example:

const {OAuth2Client} = require('google-auth-library');
const client = new OAuth2Client();
async function verify() {
  const ticket = await client.verifyIdToken({
      idToken: token,
      audience: WEB_CLIENT_ID,  // Specify the WEB_CLIENT_ID of the app that accesses the backend
      // Or, if multiple clients access the backend:
      //[WEB_CLIENT_ID_1, WEB_CLIENT_ID_2, WEB_CLIENT_ID_3]
  });
  const payload = ticket.getPayload();
  const userid = payload['sub'];
  // If the request specified a Google Workspace domain:
  // const domain = payload['hd'];
}
verify().catch(console.error);

The verifyIdToken function verifies the JWT signature, the aud claim, the exp claim, and the iss claim.

If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can check the hd claim, which indicates the hosted domain of the user. This must be used when restricting access to a resource to only members of certain domains. The absence of this claim indicates that the account does not belong to a Google hosted domain.

PHP

To validate an ID token in PHP, use the Google API Client Library for PHP. Install the library (for example, using Composer): 

composer require google/apiclient
 Then, call the verifyIdToken() function. For example:

require_once 'vendor/autoload.php';

// Get $id_token via HTTPS POST.

$client = new Google_Client(['client_id' => $WEB_CLIENT_ID]);  // Specify the WEB_CLIENT_ID of the app that accesses the backend
$payload = $client->verifyIdToken($id_token);
if ($payload) {
  $userid = $payload['sub'];
  // If the request specified a Google Workspace domain
  //$domain = $payload['hd'];
} else {
  // Invalid ID token
}

The verifyIdToken function verifies the JWT signature, the aud claim, the exp claim, and the iss claim.

If you need to validate that the ID token represents a Google Workspace or Cloud organization account, you can check the hd claim, which indicates the hosted domain of the user. This must be used when restricting access to a resource to only members of certain domains. The absence of this claim indicates that the account does not belong to a Google hosted domain.

Python

To validate an ID token in Python, use the verify_oauth2_token function. For example:

from google.oauth2 import id_token
from google.auth.transport import requests

# (Receive token by HTTPS POST)
# ...

try:
    # Specify the WEB_CLIENT_ID of the app that accesses the backend:
    idinfo = id_token.verify_oauth2_token(token, requests.Request(), WEB_CLIENT_ID)

    # Or, if multiple clients access the backend server:
    # idinfo = id_token.verify_oauth2_token(token, requests.Request())
    # if idinfo['aud'] not in [WEB_CLIENT_ID_1, WEB_CLIENT_ID_2, WEB_CLIENT_ID_3]:
    #     raise ValueError('Could not verify audience.')

    # If the request specified a Google Workspace domain
    # if idinfo['hd'] != DOMAIN_NAME:
    #     raise ValueError('Wrong domain name.')

    # ID token is valid. Get the user's Google Account ID from the decoded token.
    userid = idinfo['sub']
except ValueError:
    # Invalid token
    pass

The verify_oauth2_token function verifies the JWT signature, the aud claim, and the exp claim. You must also verify the hd claim (if applicable) by examining the object that verify_oauth2_token returns. If multiple clients access the backend server, also manually verify the aud claim.

Memanggil endpoint tokeninfo

Cara mudah untuk memvalidasi tanda tangan token ID untuk proses debug adalah dengan gunakan endpoint tokeninfo. Memanggil endpoint ini melibatkan permintaan jaringan tambahan yang melakukan sebagian besar validasi untuk Anda saat menguji validasi dan ekstraksi payload dalam kode Anda sendiri. Tidak cocok untuk digunakan dalam produksi kode karena permintaan dapat terhambat atau mengalami error intermiten.

Untuk memvalidasi token ID menggunakan endpoint tokeninfo, buat HTTPS POST atau GET ke endpoint, dan teruskan token ID di Parameter id_token. Misalnya, untuk memvalidasi token "XYZ123", buat permintaan GET berikut:

https://oauth2.googleapis.com/tokeninfo?id_token=XYZ123

Jika token ditandatangani dengan benar dan iss serta exp klaim memiliki nilai yang diharapkan, Anda akan mendapatkan respons HTTP 200, dengan bagian berisi klaim token ID berformat JSON. Berikut adalah contoh respons:

{
 // 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": "testuser@gmail.com",
 "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"
}

Jika perlu memvalidasi bahwa token ID mewakili akun Google Workspace, Anda dapat memeriksanya klaim hd, yang menunjukkan domain pengguna yang dihosting. Ini harus digunakan saat membatasi akses ke sumber daya hanya untuk anggota domain tertentu. Tidak adanya klaim ini menunjukkan bahwa akun tersebut tidak termasuk dalam domain yang dihosting Google Workspace.

Buat akun atau sesi

Setelah Anda memverifikasi token, periksa apakah pengguna sudah berada di akun pengguna Anda di skrip untuk menyiapkan database. Jika demikian, buat sesi terautentikasi untuk pengguna. Jika pengguna belum ada dalam {i>database<i} pengguna, buat catatan pengguna baru dari informasi dalam payload token ID, dan membuat sesi untuk pengguna. Anda dapat meminta pengguna untuk informasi profil tambahan yang Anda butuhkan saat Anda mendeteksi yang baru dibuat di aplikasi Anda.

Mengamankan pengguna Anda akun dengan Perlindungan Lintas Akun

Jika Anda mengandalkan Google untuk memproses login pengguna, Anda akan otomatis mendapatkan manfaat dari semua fitur dan infrastruktur keamanan yang dibuat Google untuk melindungi data pengguna. Namun, jika Akun Google pengguna disusupi atau ada beberapa masalah peristiwa keamanan yang signifikan, aplikasi Anda juga bisa menjadi rentan terhadap serangan. Untuk melindungi dari peristiwa keamanan besar, gunakan Cross Account Perlindungan untuk menerima notifikasi keamanan dari Google. Saat menerima peristiwa ini, Anda mendapatkan visibilitas terhadap perubahan penting pada keamanan akun Google pengguna dan Anda dapat mengambil tindakan terhadap layanan Anda untuk mengamankan akun Anda.