Memverifikasi token ID Google di sisi server

Setelah Google menampilkan token ID, token tersebut dikirimkan oleh permintaan metode HTTP POST, dengan nama parameter credential, ke endpoint login Anda.

Berikut adalah contoh dalam bahasa Python yang menunjukkan langkah-langkah biasa untuk memvalidasi dan menggunakan token ID:

1. Verifikasi token Pemalsuan Permintaan Lintas Situs (CSRF). Saat Anda mengirimkan kredensial ke endpoint login, kami menggunakan pola cookie pengiriman ganda untuk mencegah serangan CSRF. Sebelum setiap pengiriman, kami membuat token. Kemudian, token dimasukkan ke dalam cookie dan isi postingan, seperti yang ditunjukkan dalam contoh kode berikut:

   csrf_token_cookie = self.request.cookies.get('g_csrf_token')
   if not csrf_token_cookie:
       webapp2.abort(400, 'No CSRF token in Cookie.')
   csrf_token_body = self.request.get('g_csrf_token')
   if not csrf_token_body:
       webapp2.abort(400, 'No CSRF token in post body.')
   if csrf_token_cookie != csrf_token_body:
       webapp2.abort(400, 'Failed to verify double submit cookie.')
   

2. Verifikasi token ID.

   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 Google Workspace account.

   Users may register for Google Accounts without using Gmail or Google Workspace. 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. This ID is unique to each Google Account, making it suitable for
     // use as a primary key during account lookup. Email is not a good choice because it can be
     // changed by the user.
     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();
     // This ID is unique to each Google Account, making it suitable for use as a primary key
     // during account lookup. Email is not a good choice because it can be changed by the user.
     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) {
     // This ID is unique to each Google Account, making it suitable for use as a primary key
     // during account lookup. Email is not a good choice because it can be changed by the user.
     $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.
       # This ID is unique to each Google Account, making it suitable for use as a primary key
       # during account lookup. Email is not a good choice because it can be changed by the user.
       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.

3. Setelah validitas token dikonfirmasi, Anda dapat menggunakan informasi dalam token ID Google untuk mengaitkan status akun situs Anda:

   • Pengguna yang tidak terdaftar: Anda dapat menampilkan antarmuka pengguna (UI) pendaftaran yang memungkinkan pengguna memberikan informasi profil tambahan, jika diperlukan. Hal ini juga memungkinkan pengguna membuat akun baru dan sesi pengguna yang login secara diam-diam.

   • Akun lama yang sudah ada di situs Anda: Anda dapat menampilkan halaman web yang memungkinkan pengguna akhir memasukkan sandi mereka dan menautkan akun lama dengan kredensial Google mereka. Hal ini mengonfirmasi bahwa pengguna memiliki akses ke akun yang ada.

   • Pengguna gabungan yang kembali: Anda dapat memproses login pengguna secara otomatis.