使用 OAuth 連結 Google 帳戶

帳戶連結使用業界標準 OAuth 2.0 隱含與授權碼流程。您的服務必須支援符合 OAuth 2.0 規定的授權和憑證交換端點。

在「暗示」流程中，Google 會在使用者的瀏覽器中開啟您的授權端點。成功登入後，會將長期存取憑證傳回 Google。目前從 Google 發出的每個要求都會包含這個存取憑證。

在「授權碼」流程中，您需要兩個端點：

• Authorization 端點，可為尚未登入的使用者顯示登入 UI。授權端點也會建立短期的授權碼來記錄使用者。同意要求的存取權。

• 憑證交換端點，該端點負責兩種交換類型：

  1. 將授權碼提供給長期使用憑證和短期存取憑證。當使用者完成帳戶連結流程時，系統就會執行這個交換作業。
  2. 針對短期存取權杖交換長期更新權杖。 如果 Google 需要這個存取憑證過期，因此需要進行這個交換作業。

選擇 OAuth 2.0 流程

雖然隱含流程比較簡單，但 Google 建議採用隱含流程所核發的存取憑證永遠不會過期。這是因為憑證在隱含流程到期後，必須強制重新連結帳戶。如果您需要基於安全考量而要求憑證過期，強烈建議您改用授權碼流程。

注意：請使用以下按鈕選擇您要實作的 OAuth 2.0 流程。如有需要，系統會重新載入這份指南的內容，使其符合您的選擇。

隱含流程 授權碼

設計指南

本節說明您針對 OAuth 連結流程託管的使用者畫面設計要求和建議。在 Google 應用程式呼叫 API 後，您的平台會向使用者顯示登入 Google 頁面和帳戶連結同意畫面。使用者同意連結帳戶之後，系統就會將他們重新導向 Google 的應用程式。

圖 1.連結 Google 帳戶和同意畫面的帳戶連結。

必要條件

1. 您必須通知使用者的帳戶將連結至 Google，而不是特定的 Google 產品，例如 Google Home 或 Google 助理。

建議

建議您採取下列做法：

1. 顯示 Google 的隱私權政策。在同意畫面中加入 Google 隱私權政策連結。

2. 要分享的資料。使用簡明扼要的用詞告訴使用者 Google 需要哪些資料，以及收集這些資料的原因。

3. 加入明確的行動號召。在同意畫面上註明明確的行動號召 (例如「同意和連結」)。這是因為使用者必須瞭解需要與 Google 分享哪些資料，才能連結自己的帳戶。

4. 取消功能：如果使用者選擇不要進行連結，可以提供取消或取消訂閱的方式。

5. 清除登入程序。確保使用者明確能登入 Google 帳戶，例如使用者名稱和密碼欄位或使用 Google 帳戶登入欄位。

6. 取消連結。提供機制，讓使用者能取消連結，例如 您平台中帳戶設定的網址。您也可以加入 Google 帳戶連結，方便使用者管理已連結帳戶。

7. 可變更使用者帳戶。建議使用者切換帳戶的方法。如果使用者經常擁有多個帳戶，這項功能就特別實用。

   • 如果使用者必須先關閉同意畫面才能切換帳戶，請將可復原的錯誤傳送給 Google，讓使用者可透過 OAuth 連結和隱含流程登入所需帳戶。

8. 加入您的標誌。在同意畫面中顯示公司標誌。 請善用樣式指南來放置標誌。如果您希望一併顯示 Google 的標誌，請參閱標誌和商標一文。

圖 2.使用者登入 Google 和同意畫面的設計指南。

Create the project

Note: You can reuse an existing project and do not need to create a new project primarily for account linking.

To create your project to use account linking:

1. Go to the Google API Console.
2. 單擊創建項目 。
3. 輸入名稱或接受生成的建議。
4. 確認或編輯所有剩餘字段。
5. 點擊創建 。

要查看您的項目ID：

1. Go to the Google API Console.
2. 在登錄頁面的表格中找到您的項目。項目ID出現在ID列中。

Configure your OAuth Consent Screen

The Google Account Linking process includes a consent screen which tells users the application requesting access to their data, what kind of data they are asking for and the terms that apply. You will need to configure your OAuth consent screen before generating a Google API client ID.

1. Open the OAuth consent screen page of the Google APIs console.
2. If prompted, select the project you just created.

3. On the "OAuth consent screen" page, fill out the form and click the “Save” button.

   Application name: The name of the application asking for consent. The name should accurately reflect your application and be consistent with the application name users see elsewhere. The application name will be shown on the Account Linking consent screen.

   Application logo: An image on the consent screen that will help users recognize your app. The logo is shown on Account linking consent screen and on account settings

   Support email: For users to contact you with questions about their consent.

   Scopes for Google APIs: Scopes allow your application to access your user's private Google data. For the Google Account Linking use case, default scope (email, profile, openid) is sufficient, you don’t need to add any sensitive scopes. It is generally a best practice to request scopes incrementally, at the time access is required, rather than up front. Learn more.

   Authorized domains: To protect you and your users, Google only allows applications that authenticate using OAuth to use Authorized Domains. Your applications' links must be hosted on Authorized Domains. Learn more.

   Application Homepage link: Home page for your application. Must be hosted on an Authorized Domain.

   Application Privacy Policy link: Shown on Google Account Linking consent screen. Must be hosted on an Authorized Domain.

   Application Terms of Service link (Optional): Must be hosted on an Authorized Domain.

   

   Figure 1. Google Account Linking Consent Screen for a fictitious Application, Tunery

4. Check "Verification Status", if your application needs verification then click the "Submit For Verification" button to submit your application for verification. Refer to OAuth verification requirements for details.

實作 OAuth 伺服器

An OAuth 2.0 server implementation of the authorization code flow consists of two endpoints, which your service makes available by HTTPS. The first endpoint is the authorization endpoint, which is responsible for finding or obtaining consent from users for data access. The authorization endpoint presents a sign-in UI to your users that aren't already signed in and records consent to the requested access. The second endpoint is the token exchange endpoint, which is used to obtain encrypted strings, called tokens, that authorize a user to access your service.

When a Google application needs to call one of your service's APIs, Google uses these endpoints together to get permission from your users to call these APIs on their behalf.

An OAuth 2.0 authorization code flow session initiated by Google has the following flow:

1. Google opens your authorization endpoint in the user's browser. If the flow started on a voice-only device for an Action, Google transfers the execution to a phone.
2. The user signs in, if not signed in already, and grants Google permission to access their data with your API, if they haven't already granted permission.
3. Your service creates an authorization code and returns it to Google. To do so, redirect the user's browser back to Google with the authorization code attached to the request.
4. Google sends the authorization code to your token exchange endpoint, which verifies the authenticity of the code and returns an access token and a refresh token. The access token is a short-lived token that your service accepts as credentials to access APIs. The refresh token is a long-lived token that Google can store and use to acquire new access tokens when they expire.
5. After the user has completed the account linking flow, every subsequent request sent from Google contains an access token.

Handle authorization requests

When you need to perform account linking using the OAuth 2.0 authorization code flow, Google sends the user to your authorization endpoint with a request that includes the following parameters:

Authorization endpoint parameters
client_id	The Client ID you assigned to Google.
redirect_uri	The URL to which you send the response to this request.
state	A bookkeeping value that is passed back to Google unchanged in the redirect URI.
scope	Optional: A space-delimited set of scope strings that specify the data Google is requesting authorization for.
response_type	The type of value to return in the response. For the OAuth 2.0 authorization code flow, the response type is always code.
user_locale	The Google Account language setting in RFC5646 format, used to localize your content in the user's preferred language.

For example, if your authorization endpoint is available at https://myservice.example.com/auth, a request might look like the following:

GET https://myservice.example.com/auth?client_id=GOOGLE_CLIENT_ID&redirect_uri=REDIRECT_URI&state=STATE_STRING&scope=REQUESTED_SCOPES&response_type=code&user_locale=LOCALE

For your authorization endpoint to handle sign-in requests, do the following steps:

1. Verify that the client_id matches the Client ID you assigned to Google, and that the redirect_uri matches the redirect URL provided by Google for your service. These checks are important to prevent granting access to unintended or misconfigured client apps. If you support multiple OAuth 2.0 flows, also confirm that the response_type is code.
2. Check if the user is signed in to your service. If the user isn't signed in, complete your service's sign-in or sign-up flow.
3. Generate an authorization code for Google to use to access your API. The authorization code can be any string value, but it must uniquely represent the user, the client the token is for, and the code's expiration time, and it must not be guessable. You typically issue authorization codes that expire after approximately 10 minutes.
4. Confirm that the URL specified by the redirect_uri parameter has the following form:

     https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID
     https://oauth-redirect-sandbox.googleusercontent.com/r/YOUR_PROJECT_ID
     

5. Redirect the user's browser to the URL specified by the redirect_uri parameter. Include the authorization code you just generated and the original, unmodified state value when you redirect by appending the code and state parameters. The following is an example of the resulting URL:

   https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID?code=AUTHORIZATION_CODE&state=STATE_STRING

Handle token exchange requests

Your service's token exchange endpoint is responsible for two kinds of token exchanges:

• Exchange authorization codes for access tokens and refresh tokens
• Exchange refresh tokens for access tokens

Token exchange requests include the following parameters:

Token exchange endpoint parameters
client_id	A string that identifies the request origin as Google. This string must be registered within your system as Google's unique identifier.
client_secret	A secret string that you registered with Google for your service.
grant_type	The type of token being exchanged. It's either authorization_code or refresh_token.
code	When grant_type=authorization_code, this parameter is the code Google received from either your sign-in or token exchange endpoint.
redirect_uri	When grant_type=authorization_code, this parameter is the URL used in the initial authorization request.
refresh_token	When grant_type=refresh_token, this parameter is the refresh token Google received from your token exchange endpoint.

Exchange authorization codes for access tokens and refresh tokens

After the user signs in and your authorization endpoint returns a short-lived authorization code to Google, Google sends a request to your token exchange endpoint to exchange the authorization code for an access token and a refresh token.

For these requests, the value of grant_type is authorization_code, and the value of code is the value of the authorization code you previously granted to Google. The following is an example of a request to exchange an authorization code for an access token and a refresh token:

POST /token HTTP/1.1
Host: oauth2.example.com
Content-Type: application/x-www-form-urlencoded

client_id=GOOGLE_CLIENT_ID&client_secret=GOOGLE_CLIENT_SECRET&grant_type=authorization_code&code=AUTHORIZATION_CODE&redirect_uri=REDIRECT_URI

To exchange authorization codes for an access token and a refresh token, your token exchange endpoint responds to POST requests by executing the following steps:

1. Verify that the client_id identifies the request origin as an authorized origin, and that the client_secret matches the expected value.
2. Verify that the authorization code is valid and not expired, and that the client ID specified in the request matches the client ID associated with the authorization code.
3. Confirm that the URL specified by the redirect_uri parameter is identical to the value used in the initial authorization request.
4. If you can't verify all of the above criteria, return an HTTP 400 Bad Request error with {"error": "invalid_grant"} as the body.
5. Otherwise, use the user ID from the authorization code to generate a refresh token and an access token. These tokens can be any string value, but they must uniquely represent the user and the client the token is for, and they must not be guessable. For access tokens, also record the expiration time of the token, which is typically an hour after you issue the token. Refresh tokens don't expire.
6. Return the following JSON object in the body of the HTTPS response:

   {
   "token_type": "Bearer",
   "access_token": "ACCESS_TOKEN",
   "refresh_token": "REFRESH_TOKEN",
   "expires_in": SECONDS_TO_EXPIRATION
   }
   

Google stores the access token and the refresh token for the user and records the expiration of the access token. When the access token expires, Google uses the refresh token to get a new access token from your token exchange endpoint.

Exchange refresh tokens for access tokens

When an access token expires, Google sends a request to your token exchange endpoint to exchange a refresh token for a new access token.

For these requests, the value of grant_type is refresh_token, and the value of refresh_token is the value of the refresh token you previously granted to Google. The following is an example of a request to exchange a refresh token for an access token:

POST /token HTTP/1.1
Host: oauth2.example.com
Content-Type: application/x-www-form-urlencoded

client_id=GOOGLE_CLIENT_ID&client_secret=GOOGLE_CLIENT_SECRET&grant_type=refresh_token&refresh_token=REFRESH_TOKEN

To exchange a refresh token for an access token, your token exchange endpoint responds to POST requests by executing the following steps:

1. Verify that the client_id identifies the request origin as Google, and that the client_secret matches the expected value.
2. Verify that the refresh token is valid, and that the client ID specified in the request matches the client ID associated with the refresh token.
3. If you can't verify all of the above criteria, return an HTTP 400 Bad Request error with {"error": "invalid_grant"} as the body.
4. Otherwise, use the user ID from the refresh token to generate an access token. These tokens can be any string value, but they must uniquely represent the user and the client the token is for, and they must not be guessable. For access tokens, also record the expiration time of the token, typically an hour after you issue the token.
5. Return the following JSON object in the body of the HTTPS response:

   {
   "token_type": "Bearer",
   "access_token": "ACCESS_TOKEN",
   "expires_in": SECONDS_TO_EXPIRATION
   }

Note: You can optionally return a new refresh_token in your response. For more information about when returning a new refresh_token is preferred, see Working with tokens.

Handle userinfo requests

The userinfo endpoint is an OAuth 2.0 protected resource that return claims about the linked user. Implementing and hosting the userinfo endpoint is optional, except for the following use cases:

• Linked Account Sign-In with Google One Tap.
• Frictionless subscription on AndroidTV.

After the access token has been successfully retrieved from your token endpoint, Google sends a request to your userinfo endpoint to retrieve basic profile information about the linked user.

userinfo endpoint request headers
Authorization header	The access token of type Bearer.

For example, if your userinfo endpoint is available at https://myservice.example.com/userinfo, a request might look like the following:

GET /userinfo HTTP/1.1
Host: myservice.example.com
Authorization: Bearer ACCESS_TOKEN

For your userinfo endpoint to handle requests, do the following steps:

1. Extract access token from the Authorization header and return information for the user associated with the access token.
2. If the access token is invalid, return an HTTP 401 Unauthorized error with using the WWW-Authenticate Response Header. Below is an example of a userinfo error response:

   HTTP/1.1 401 Unauthorized
   WWW-Authenticate: error="invalid_token",
   error_description="The Access Token expired"
   

   If a 401 Unauthorized, or any other unsuccessful error response is returned during the linking process, the error will be non-recoverable, the retrieved token will be discarded and the user will have to initiate the linking process again.

3. If the access token is valid, return and HTTP 200 response with the following JSON object in the body of the HTTPS response:

   {
   "sub": "USER_UUID",
   "email": "EMAIL_ADDRESS",
   "given_name": "FIRST_NAME",
   "family_name": "LAST_NAME",
   "name": "FULL_NAME",
   "picture": "PROFILE_PICTURE",
   }
   

   If your userinfo endpoint returns an HTTP 200 success response, the retrieved token and claims are registered against the user's Google account.

   userinfo endpoint response
   sub	A unique ID that identifies the user in your system.
   email	Email address of the user.
   given_name	Optional: First name of the user.
   family_name	Optional: Last name of the user.
   name	Optional: Full name of the user.
   picture	Optional: Profile picture of the user.

驗證實作

您可以通过使用验证实现的OAuth 2.0游乐场工具。

在工具中，执行以下步骤：

1. 单击配置打开的OAuth 2.0配置窗口。
2. 在OAuth流场中，选择客户端。
3. 在OAuth端点字段中，选择自定义。
4. 在相应字段中指定您的 OAuth 2.0 端点和您分配给 Google 的客户端 ID。
5. 在步骤1部分，不要选择任何谷歌范围。相反，将此字段留空或键入对您的服务器有效的范围（如果不使用 OAuth 范围，则输入任意字符串）。当您完成后，单击授权的API。
6. 在步骤2和步骤3段，完成OAuth 2.0流程和验证每个步骤按预期工作。

您可以通过验证您的实现谷歌帐户链接演示工具。

在工具中，执行以下步骤：

1. 点击登录在与谷歌按钮。
2. 选择您要关联的帐户。
3. 输入服务标识。
4. （可选）输入您将请求访问的一个或多个范围。
5. 单击开始演示。
6. 出现提示时，确认您可以同意并拒绝链接请求。
7. 确认您被重定向到您的平台。