Verificare il token ID di Google sul lato server

Quando utilizzi i servizi di identità Google o il flusso del codice di autorizzazione OAuth 2.0, Google restituisce il token ID utilizzando il metodo POST all'endpoint di reindirizzamento. In alternativa, il flusso implicito OIDC utilizza una richiesta GET. Di conseguenza, la tua applicazione è responsabile della trasmissione sicura di queste credenziali ricevute al tuo server.

    HTTP/1.1 302 Found
    Location: https://<REDIRECT_URI>#access_token=<ACCESS_TOKEN>&token_type=bearer&expires_in=<TIME_IN_SECONDS>&scope=<SCOPE>&state=<STATE_STRING>
    

POST /auth/token-verification HTTP/1.1
Host: example.com
Content-Type: application/json;charset=UTF-8
Cookie: g_csrf_token=<CSRF_TOKEN>
Origin: https://example.com
Content-Length: <LENGTH_OF_JSON_BODY>
    {
      "credential": "<ID_TOKEN>",
      "g_csrf_token": "<CSRF_TOKEN>",
      "client_id": "<CLIENT_ID>"
    }

1. Convalida di g_csrf_token per impedire attacchi di tipo Cross-Site Request Forgery (CSRF):

   • Estrai il valore del token CSRF dal cookie g_csrf_token.
   • Estrai il valore del token CSRF dal corpo della richiesta. La libreria GIS include questo token nel corpo della richiesta POST come parametro, denominato anche g_csrf_token.
   • Confronta i due valori dei token
     • Se entrambi i valori sono presenti e corrispondono completamente, la richiesta viene considerata legittima e proveniente dal tuo dominio.
     • Se i valori non sono presenti o non corrispondono, la richiesta deve essere rifiutata dal server. Questo controllo garantisce che la richiesta sia stata avviata da JavaScript in esecuzione sul tuo dominio, in quanto solo il tuo dominio può accedere al cookie g_csrf_token.

2. Verifica il 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.

   使用 Google API 客户端库

   使用某个 Google API 客户端库（例如 Java、 Node.js、 PHP、 Python） 是在生产环境中验证 Google ID 令牌的推荐方法。

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   Java

   要在 Java 中验证 ID 令牌，请使用 GoogleIdTokenVerifier 对象。例如：

   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.");
   }

   GoogleIdTokenVerifier.verify() 方法验证 JWT 签名、aud 声明、iss 声明以及 exp 项版权主张。

   如果您需要验证 ID 令牌是否代表 Google Workspace 或 Cloud 组织账号，您可以通过检查域名来验证 hd 所有权声明 由 Payload.getHostedDomain() 方法返回。该 email 声明不足以保证账号是由网域管理 或组织。

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   Node.js

   要在 Node.js 中验证 ID 令牌，请使用适用于 Node.js 的 Google Auth 库。 安装该库：

   npm install google-auth-library --save

   然后，调用 verifyIdToken() 函数。例如：

   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);

   verifyIdToken 函数用于验证 JWT 签名、aud 声明、exp 声明 以及 iss 声明。

   如果您需要验证 ID 令牌是否代表 Google Workspace 或 Cloud 组织账号时，您可以查看 hd 声明，该声明表示托管的 用户的网域。将资源访问权限限制为仅允许成员访问时，必须使用此设置 特定网域的用户缺少此声明即表示该账号不属于 Google 托管的域。

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   PHP

   要在 PHP 中验证 ID 令牌，请使用适用于 PHP 的 Google API 客户端库。 安装该库（例如，使用 Composer）：

   composer require google/apiclient

   然后，调用 verifyIdToken() 函数。例如：

   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
   }

   verifyIdToken 函数用于验证 JWT 签名、aud 声明、exp 声明 以及 iss 声明。

   如果您需要验证 ID 令牌是否代表 Google Workspace 或 Cloud 组织账号时，您可以查看 hd 声明，该声明表示托管的 用户的网域。将资源访问权限限制为仅允许成员访问时，必须使用此设置 特定网域的用户缺少此声明即表示该账号不属于 Google 托管的域。

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   Python

   要在 Python 中验证 ID 令牌，请使用 verify_oauth2_token 函数。例如：

   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

   verify_oauth2_token 函数验证 JWT 签名、aud 声明和 exp 声明。 您还必须验证 hd 检查 verify_oauth2_token 返回。如果多个客户端访问 后端服务器，另请手动验证 aud 声明。

3. Una volta confermata la validità del token, puoi utilizzare le informazioni nel token ID Google per correlare lo stato dell'account del tuo sito:

   • Un utente non registrato:puoi mostrare un'interfaccia utente di registrazione che consente all'utente di fornire ulteriori informazioni sul profilo, se necessario. Consente inoltre all'utente di creare automaticamente il nuovo account e una sessione utente con accesso eseguito.

   • Un account esistente già presente nel tuo sito:puoi mostrare una pagina web che consente all'utente finale di inserire la propria password e collegare l'account legacy alle proprie credenziali Google. In questo modo viene confermato che l'utente ha accesso all'account esistente.

   • Un utente federato di ritorno:puoi accedere all'utente in modalità silenziosa.