서버 측에서 Google ID 토큰 확인

Google에서 ID 토큰을 반환하면 HTTP POST 메서드 요청에 의해 매개변수 이름 credential와 함께 로그인 엔드포인트에 제출됩니다.

다음은 ID 토큰을 검증하고 사용하는 일반적인 단계를 보여주는 Python 언어의 예입니다.

  1. 교차 사이트 요청 위조 (CSRF) 토큰을 확인합니다. 로그인 엔드포인트에 사용자 인증 정보를 제출하면 CSRF 공격을 방지하기 위해 double-submit-cookie 패턴이 사용됩니다. 제출할 때마다 토큰이 생성됩니다. 그런 다음 다음 코드 예와 같이 토큰이 쿠키와 게시물 본문 모두에 배치됩니다.

    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. ID 토큰을 확인합니다.

    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
      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.

  3. 토큰의 유효성이 확인되면 Google ID 토큰의 정보를 사용하여 사이트의 계정 상태를 연결할 수 있습니다.

    • 등록되지 않은 사용자: 필요한 경우 사용자가 프로필 정보를 추가로 제공할 수 있는 가입 사용자 인터페이스(UI)를 표시할 수 있습니다. 또한 사용자가 새 계정과 로그인한 사용자 세션을 자동으로 만들 수 있습니다.

    • 사이트에 이미 있는 기존 계정: 최종 사용자가 비밀번호를 입력하고 기존 계정을 Google 사용자 인증 정보와 연결할 수 있는 웹페이지를 표시할 수 있습니다. 이렇게 하면 사용자가 기존 계정에 액세스할 수 있는지 확인할 수 있습니다.

    • 재방문하는 제휴 사용자: 사용자를 자동으로 로그인할 수 있습니다.