導入 OAuth 2.0 伺服器

每個 Cloud-to-cloud 整合都必須包含使用者驗證機制。

驗證可讓您將使用者的 Google 帳戶連結至驗證系統中的使用者帳戶。這樣一來，當智慧住宅服務收到意圖時，您就能識別使用者。Google 智慧住宅僅支援使用授權碼流程的 OAuth。

本頁面說明如何設定 OAuth 2.0 伺服器，使其與 Cloud-to-cloud 整合服務搭配運作。

透過 OAuth 連結 Google 帳戶

在授權碼流程中，您需要兩個端點：

• 授權端點，會向尚未登入的使用者顯示登入 UI。授權端點也會建立短效授權碼，記錄使用者對所要求存取權的同意聲明。

• 權杖交換端點，負責兩種交換：

  1. 將授權碼換成長期有效的更新權杖和短期存取權杖。使用者進行帳戶連結流程時，就會發生這個交換。
  2. 將長期有效的更新權杖換成短期有效的存取權杖。如果 Google 需要新的存取權杖，因為現有的存取權杖已過期，就會發生此交換。

設計指南

本節將說明您為 OAuth 連結流程代管的使用者畫面，相關設計要求和建議。在 Google 應用程式呼叫此方法後，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後，系統會將他們重新導向 Google 應用程式。

需求條件

1. 您必須說明使用者的帳戶將連結至 Google，而不是 Google Home 或 Google 助理等特定 Google 產品。
2. 您必須提供 Google 授權聲明，例如「登入即表示您授權 Google 控制您的裝置」。請參閱 Google Home 開發人員政策的「Google 裝置控制授權」一節。
3. 您必須開啟 Web OAuth 連結頁面，並確保使用者有明確的 Google 帳戶登入方式，例如使用者名稱和密碼欄位。請勿使用 Google 登入 (GSI) 方法，因為這會讓使用者不必前往 Web OAuth 連結頁面，即可完成連結。這違反了 Google 政策。

建議

建議您採取以下做法：

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

2. 要共用的資料。使用簡潔明瞭的用語，告知使用者 Google 需要哪些資料，以及原因。

3. 明確的行動號召。在同意聲明畫面上清楚列出行動號召，例如「同意並連結」。這是因為使用者需要瞭解自己必須與 Google 分享哪些資料，才能連結帳戶。

4. 可取消訂閱。如果使用者選擇不連結，請提供返回或取消的選項。

5. 明確的登入程序。請確保使用者有明確的方法登入 Google 帳戶，例如使用者名稱和密碼欄位，或是「使用 Google 帳戶登入」功能。

6. 可取消連結。提供使用者解除連結的機制，例如您平台上的帳戶設定網址。或者，您也可以加入 Google 帳戶的連結，讓使用者管理已連結的帳戶。

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

   • 如果使用者必須關閉同意畫面才能切換帳戶，請將可復原的錯誤傳送至 Google，方便使用者透過 OAuth 連結登入所需帳戶。

8. 加入標誌。在同意畫面上顯示公司標誌。請依照您的樣式規範放置標誌。如果您也想顯示 Google 的標誌，請參閱標誌和商標。

授權碼流程

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:

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

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:

Configure how Google sends credentials to your server

Depending on its implementation, your authorization server expects to receive client credentials either in the request body, or in the request header.

By default, Google sends the credentials in the request body. If your authorization server requires the client credentials to be in the request header, you must configure your Cloud-to-cloud integration accordingly:

Go to the Developer Console

1. From the list of projects, click Open next to the project you want to work with.

2. Under Cloud-to-Cloud, select Develop.

3. Click Open next your integration.

4. Scroll down to the Permissions (optional) section and select the Have Google transmit Client ID and secret via HTTP basic auth header checkbox.

5. Click Save to save your changes.

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
   }

處理使用者資訊要求

userinfo 端點是 OAuth 2.0 受保護的資源，可傳回已連結使用者的聲明。除了下列用途外，不一定要實作並代管 userinfo 端點：

• 使用 Google One Tap 登入已連結帳戶。
• 在 AndroidTV 上順暢訂閱。

成功從權杖端點擷取存取權杖後，Google 會向您的使用者資訊端點傳送要求，以擷取已連結使用者的基本個人資料。

舉例來說，如果您的 userinfo 端點位於 https://myservice.example.com/userinfo，要求可能如下所示：

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

為了讓 userinfo 端點處理要求，請按照下列步驟操作：

1. 從授權標頭擷取存取權杖，然後為與存取權杖相關聯的使用者傳回資訊。
2. 如果存取權杖無效，請使用 WWW-Authenticate 回應標頭傳回 HTTP 401 Unauthorized 錯誤。以下是 userinfo 錯誤回應的範例：

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

   如果連結過程中傳回 401 未授權錯誤或其他失敗錯誤回應，將無法復原錯誤，擷取到的憑證將遭到捨棄，使用者必須再次啟動連結程序。

3. 如果存取權杖有效，則傳回並傳回 HTTP 200 回應，且 HTTPS 內文含有下列 JSON 物件 回覆：

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

   如果您的 userinfo 端點傳回 HTTP 200 成功回應，則會根據使用者的 Google 帳戶登錄擷取的權杖和憑證附加資訊。

   userinfo 端點回應
   sub	用來在系統中識別使用者的專屬 ID。
   email	使用者的電子郵件地址。
   given_name	選填：使用者的名字。
   family_name	選填：使用者的姓氏。
   name	選填：使用者全名。
   picture	選用：使用者的個人資料相片。