使用 OAuth 进行 Google 帐号关联

帐号使用行业标准的 OAuth 2.0 隐式和授权代码流程来关联。您的服务必须支持符合 OAuth 2.0 规范的授权和令牌交换端点。

In the implicit flow, Google opens your authorization endpoint in the user's browser. After successful sign in, you return a long-lived access token to Google. This access token is now included in every request sent from Google.

In the authorization code flow, you need two endpoints:

• The authorization endpoint, which presents the sign-in UI to your users that aren't already signed in. The authorization endpoint also creates a short-lived authorization code to record users' consent to the requested access.

• The token exchange endpoint, which is responsible for two types of exchanges:

  1. Exchanges an authorization code for a long-lived refresh token and a short-lived access token. This exchange happens when the user goes through the account linking flow.
  2. Exchanges a long-lived refresh token for a short-lived access token. This exchange happens when Google needs a new access token because the one it had expired.

Choose an OAuth 2.0 flow

Although the implicit flow is simpler to implement, Google recommends that access tokens issued by the implicit flow never expire. This is because the user is forced to link their account again after a token expires with the implicit flow. If you need token expiration for security reasons, we strongly recommend that you use the authorization code flow instead.

Design guidelines

This section describes the design requirements and recommendations for the user screen that you host for OAuth linking flows. After it's called by Google's app, your platform displays a sign in to Google page and account linking consent screen to the user. The user is directed back to Google's app after giving their consent to link accounts.

Requirements

1. You must communicate that the user’s account will be linked to Google, not a specific Google product like Google Home or Google Assistant.

Recommendations

We recommend that you do the following:

1. Display Google's Privacy Policy. Include a link to Google’s Privacy Policy on the consent screen.

2. Data to be shared. Use clear and concise language to tell the user what data of theirs Google requires and why.

3. Clear call-to-action. State a clear call-to-action on your consent screen, such as “Agree and link.” This is because users need to understand what data they're required to share with Google to link their accounts.

4. Ability to cancel. Provide a way for users to go back or cancel, if they choose not to link.

5. Clear sign-in process. Ensure that users have clear method for signing in to their Google account, such as fields for their username and password or Sign in with Google.

6. Ability to unlink. Offer a mechanism for users to unlink, such as a URL to their account settings on your platform. Alternatively, you can include a link to Google Account where users can manage their linked account.

7. Ability to change user account. Suggest a method for users to switch their account(s). This is especially beneficial if users tend to have multiple accounts.

   • If a user must close the consent screen to switch accounts, send a recoverable error to Google so the user can sign in to the desired account with OAuth linking and the implicit flow.

8. Include your logo. Display your company logo on the consent screen. Use your style guidelines to place your logo. If you wish to also display Google's logo, see Logos and trademarks.

创建项目

如需创建项目以使用帐号关联，请按以下步骤操作：

1. Go to the Google API Console.
2. 单击创建项目 。
3. 输入名称或接受生成的建议。
4. 确认或编辑所有剩余字段。
5. 点击创建 。

要查看您的项目ID：

1. Go to the Google API Console.
2. 在登录页面的表格中找到您的项目。项目ID出现在ID列中。

配置 OAuth 权限请求页面

Google 帐号关联流程包括一个同意屏幕，用于告知用户请求访问其数据的应用、用户要求的数据类型以及适用的条款。您需要先配置 OAuth 权限请求页面，然后才能生成 Google API 客户端 ID。

1. 打开 Google API 控制台的 OAuth 同意屏幕页面。
2. 如果出现提示，请选择您刚刚创建的项目。

3. 在“OAuth 同意屏幕”页面上，填写表单，然后点击“保存”按钮。

   应用名称：请求用户同意的应用的名称。该名称应准确反映您的应用，并与用户在别处看到的应用名称保持一致。应用名称将显示在帐号关联同意屏幕上。

   应用徽标：同意屏幕上的图片，有助于用户识别您的应用。徽标会显示在帐号关联同意屏幕和帐号设置中

   支持电子邮件地址：供用户就其同意情况与您联系。

   Google API 的范围：范围允许您的应用访问用户的私有 Google 数据。对于 Google 帐号关联用例，默认范围（电子邮件、个人资料、OpenID）就足够了，您无需添加任何敏感范围。最佳做法一般是在需要访问时逐步请求作用域，而不是预先请求。了解详情。

   已获授权的网域：为保护您和您的用户，Google 仅允许使用 OAuth 进行身份验证的应用使用已获授权的网域。您应用的链接必须托管在已获授权的网域上。了解详情。

   应用首页链接：您的应用的首页。必须托管在已获授权的网域上。

   应用隐私权政策链接：在 Google 帐号关联同意屏幕上显示。必须托管在已获授权的网域上。

   应用服务条款链接（可选）：必须托管在已获授权的网域上。

   

   图 1. 一款虚构应用 Tunery 的 Google 帐号关联同意屏幕

4. 查看“验证状态”。如果您的申请需要验证，请点击“提交验证”按钮，提交您的申请。如需了解详情，请参阅 OAuth 验证要求。

实现 OAuth 服务器

To support the OAuth 2.0 implicit flow, your service makes an authorization endpoint available by HTTPS. This endpoint is responsible for authentication and 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.

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

A typical OAuth 2.0 implicit flow session initiated by Google has the following flow:

1. Google opens your authorization endpoint in the user's browser. 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.
2. Your service creates an access token and returns it to Google. To do so, redirect the user's browser back to Google with the access token attached to the request.
3. Google calls your service's APIs and attaches the access token with each request. Your service verifies that the access token grants Google authorization to access the API and then completes the API call.

Handle authorization requests

When a Google application needs to perform account linking via an OAuth 2.0 implicit 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.
response_type	The type of value to return in the response. For the OAuth 2.0 implicit flow, the response type is always token.
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&response_type=token&user_locale=LOCALE

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

1. Verify the client_id and redirect_uri values to prevent granting access to unintended or misconfigured client apps:

   • Confirm that the client_id matches the client ID you assigned to Google.
   • 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
     

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 access token for Google to use to access your API. The access token can be any string value, but it must uniquely represent the user and the client the token is for and must not be guessable.

4. Send an HTTP response that redirects the user's browser to the URL specified by the redirect_uri parameter. Include all of the following parameters in the URL fragment:

   • access_token: The access token you just generated
   • token_type: The string bearer
   • state: The unmodified state value from the original request

   The following is an example of the resulting URL:

   https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID#access_token=ACCESS_TOKEN&token_type=bearer&state=STATE_STRING

Google's OAuth 2.0 redirect handler receives the access token and confirms that the state value hasn't changed. After Google has obtained an access token for your service, Google attaches the token to subsequent calls to your service APIs.

处理 userinfo 请求

userinfo 端点是受 OAuth 2.0 保护的资源，会返回关联用户的声明。实现和托管 userinfo 端点是可选的，但以下用例除外：

• 使用 Google One Tap 登录关联的账号。
• Android TV 提供顺畅的订阅体验。

从您的令牌端点成功检索到访问令牌后，Google 会向您的 userinfo 端点发送请求，以检索关联用户的基本个人资料信息。

userinfo 端点请求标头
Authorization header	Bearer 类型的访问令牌。

例如，如果您的 userinfo 端点可通过 https://myservice.example.com/userinfo 时，请求可能如下所示：

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

为了让 userinfo 端点能够处理请求，请执行以下步骤：

1. 从 Authorization 标头中提取访问令牌，并返回与访问令牌相关联的用户的信息。
2. 如果访问令牌无效，则使用 WWW-Authenticate 响应标头返回 HTTP 401 Unauthorized 错误。下面是一个 userinfo 错误响应示例：

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

   如果在关联过程中返回 401 未经授权错误或任何其他失败的错误响应，该错误将无法恢复，检索到的令牌将被舍弃，并且用户必须重新开始关联流程。

3. 如果访问令牌有效，则返回 HTTPS 正文中包含以下 JSON 对象的 HTTP 200 响应 回复：

   {
   "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 端点返回 HTTP 200 成功响应，则系统会针对用户的 Google 账号注册检索到的令牌和声明。

   userinfo 端点响应
   sub	系统中用于识别用户的唯一 ID。
   email	用户的电子邮件地址。
   given_name	可选：用户的名字。
   family_name	可选：用户的姓氏。
   name	可选：用户的全名。
   picture	可选：用户的个人资料照片。

验证您的实现

You can validate your implementation by using the OAuth 2.0 Playground tool.

In the tool, do the following steps:

1. Click Configuration settings to open the OAuth 2.0 Configuration window.
2. In the OAuth flow field, select Client-side.
3. In the OAuth Endpoints field, select Custom.
4. Specify your OAuth 2.0 endpoint and the client ID you assigned to Google in the corresponding fields.
5. In the Step 1 section, don't select any Google scopes. Instead, leave this field blank or type a scope valid for your server (or an arbitrary string if you don't use OAuth scopes). When you're done, click Authorize APIs.
6. In the Step 2 and Step 3 sections, go through the OAuth 2.0 flow and verify that each step works as intended.

You can validate your implementation by using the Google Account Linking Demo tool.

In the tool, do the following steps:

1. Click the Sign-in with Google button.
2. Choose the account you'd like to link.
3. Enter the service ID.
4. Optionally enter one or more scopes that you will request access for.
5. Click Start Demo.
6. When prompted, confirm that you may consent and deny the linking request.
7. Confirm that you are redirected to your platform.