使用后端服务器进行身份验证

如果您在与后端服务器通信的应用或网站上使用 Google 登录功能，则可能需要识别该服务器上当前已登录的用户。为了安全地执行此操作，请在用户成功登录后，使用 HTTPS 将该用户的 ID 令牌发送到您的服务器。然后，在服务器上验证 ID 令牌的完整性，并使用令牌中包含的用户信息来建立会话或创建新帐号。

警告：请勿在后端服务器上接受普通的用户 ID，例如可以通过 GIDGoogleUser.userID property 获取的用户 ID。修改后的客户端应用可以将任意用户 ID 发送到您的服务器以模拟用户，因此您必须改用可验证的 ID 令牌来安全地获取服务器端已登录用户的用户 ID。

将 ID 令牌发送到您的服务器

在用户成功登录后，获取其 ID 令牌：

Swift

GIDSignIn.sharedInstance.signIn(withPresenting: self) { signInResult, error in
    guard error == nil else { return }
    guard let signInResult = signInResult else { return }

    signInResult.user.refreshTokensIfNeeded { user, error in
        guard error == nil else { return }
        guard let user = user else { return }

        let idToken = user.idToken
        // Send ID token to backend (example below).
    }
}

Objective-C

[GIDSignIn.sharedInstance signInWithPresentingViewController:self
                                              completion:^(GIDSignInResult * _Nullable signInResult,
                                                           NSError * _Nullable error) {
      if (error) { return; }
      if (signInResult == nil) { return; }

      [signInResult.user refreshTokensIfNeededWithCompletion:^(GIDGoogleUser * _Nullable user,
                                                               NSError * _Nullable error) {
          if (error) { return; }
          if (user == nil) { return; }

          NSString *idToken = user.idToken;
          // Send ID token to backend (example below).
      }];
}];

然后，使用 HTTPS POST 请求将 ID 令牌发送到您的服务器：

Swift

func tokenSignInExample(idToken: String) {
    guard let authData = try? JSONEncoder().encode(["idToken": idToken]) else {
        return
    }
    let url = URL(string: "https://yourbackend.example.com/tokensignin")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/json", forHTTPHeaderField: "Content-Type")

    let task = URLSession.shared.uploadTask(with: request, from: authData) { data, response, error in
        // Handle response from your backend.
    }
    task.resume()
}

Objective-C

NSString *signinEndpoint = @"https://yourbackend.example.com/tokensignin";
NSDictionary *params = @{@"idtoken": idToken};

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:signinEndpoint];
[request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];
[request setHTTPMethod:@"POST"];
[request setHTTPBody:[self httpBodyForParamsDictionary:params]];

NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:request
                                   queue:queue
                       completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
                         if (error) {
                           NSLog(@"Error: %@", error.localizedDescription);
                         } else {
                           NSLog(@"Signed in as %@", data.bytes);
                         }
                       }];

验证 ID 令牌的完整性

通过 HTTPS POST 收到 ID 令牌后，您必须验证令牌的完整性。

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.

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 CLIENT_ID of the app that accesses the backend:
    .setAudience(Collections.singletonList(CLIENT_ID))
    // Or, if multiple clients access the backend:
    //.setAudience(Arrays.asList(CLIENT_ID_1, CLIENT_ID_2, 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: CLIENT_ID,  // Specify the CLIENT_ID of the app that accesses the backend
      // Or, if multiple clients access the backend:
      //[CLIENT_ID_1, CLIENT_ID_2, 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' => $CLIENT_ID]);  // Specify the 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 CLIENT_ID of the app that accesses the backend:
    idinfo = id_token.verify_oauth2_token(token, requests.Request(), CLIENT_ID)

    # Or, if multiple clients access the backend server:
    # idinfo = id_token.verify_oauth2_token(token, requests.Request())
    # if idinfo['aud'] not in [CLIENT_ID_1, CLIENT_ID_2, 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.

调用 tokeninfo 端点

若要验证用于调试的 ID 令牌签名，一种简单的方法是使用 tokeninfo 端点。调用此端点涉及到一个额外的网络请求，该网络请求会为您执行大部分验证，而您在自己的代码中测试适当的验证和载荷提取时。它不适合在生产代码中使用，因为请求可能会受到限制或出现间歇性错误。

如需使用 tokeninfo 端点验证 ID 令牌，请向该端点发出 HTTPS POST 或 GET 请求，并在 id_token 参数中传递您的 ID 令牌。例如，要验证令牌“XYZ123”，可发出以下 GET 请求：

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

如果令牌已正确签名，并且 iss 和 exp 声明具有预期值，您会收到 HTTP 200 响应，其正文包含 JSON 格式的 ID 令牌声明。以下是示例响应：

{
 // 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": "[e-mail]",
 "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"
}

警告：收到这些声明后，您仍然需要检查 aud 声明是否包含应用的某个客户端 ID。如果包含，则表示该令牌有效且适用于您的客户端，您可以安全地检索并使用 sub 声明中用户的唯一 Google ID。

如果您需要验证此 ID 令牌是否代表 Google Workspace 帐号，可以检查 hd 声明，该声明指示用户的托管网域。仅允许特定网域的成员访问资源时，必须使用此方法。缺少此声明表示帐号不属于 Google Workspace 托管网域。

创建账号或会话

验证令牌后，检查用户是否已经在您的用户数据库中。如果是，请为用户建立经过身份验证的会话。如果用户不在您的用户数据库中，请根据 ID 令牌载荷中的信息创建新的用户记录，并为用户建立会话。当您在应用中检测到新创建的用户时，可以提示用户提供所需的任何其他个人资料信息。

使用跨账号保护功能保护用户账号

如果您依靠 Google 让用户登录，则会自动受益于 Google 为保护用户数据而构建的所有安全功能和基础架构。不过，万一用户的 Google 帐号遭到入侵或发生其他重大安全性事件，您的应用也很容易遭到攻击。为了更好地保护您的账号免受任何重大安全性事件的影响，请使用跨账号保护功能接收来自 Google 的安全提醒。收到这些事件后，您就可以深入了解用户 Google 帐号安全性方面的重要变化，然后根据自己的服务采取措施，以确保帐号安全。