实现 OAuth 2.0 服务器

每个 Cloud-to-cloud 集成都必须包含用户身份验证机制。

通过身份验证，您可以将用户的 Google 账号与用户在您的身份验证系统中的账号相关联。这样，您就可以在您的执行方式接收到智能家居 intent 时识别用户。Google 智能家居仅支持包含授权代码流程的 OAuth。

本页介绍了如何设置 OAuth 2.0 服务器，以使其可与 Cloud-to-cloud 集成。

使用 OAuth 进行 Google 账号关联

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.

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.

This figure shows the steps for a user to link their Google account to your authentication system. The first screenshot shows user-initiated linking from your platform. The second image shows user sign-in to Google, while the third shows the user consent and confirmation for linking their Google account with your app. The final screenshot shows a successfully linked user account in the Google app.
Figure 1. Account linking user sign in to Google and consent screens.

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.
  2. You must have a Google authorization statement such as "By signing in, you are authorizing Google to control your devices." See the Google Device Control Authorization section of the Google Home Developer Policies.
  3. You must provide a way for users to go back or cancel, if they choose not to link.
  4. You must open the Web OAuth linking page and ensure users have a clear method for signing in to their Google Account, such as fields for their username and password. Don't use the Google Sign-In (GSI) method that enables users to link without being taken to the Web OAuth Linking page. It is a violation of Google policy.

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 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.

  5. 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.

  6. 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.

授权代码流程

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:

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.

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
}

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：

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。
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