Account linking with OAuth and Google Sign-In (Dialogflow)

The OAuth and Google Sign-In linking type adds Google Sign-In on top of OAuth based account linking. This provides seamless voice-based linking for Google users while also enabling account linking for users who registered to your service with a non-Google identity.

This linking type begins with Google Sign-In, which allows you to check if the user's Google profile information exists in your system. If the user's information isn't found in your system, a standard OAuth flow begins. The user can also choose to create a new account with their Google profile information.

Figure 1: After your Action gets access to the user's Google profile, you can use it to find a match for the user in your authentication system.

To perform account linking with OAuth and Google Sign-In, follow these general steps:

1. First, ask the user to give consent to access their Google profile.
2. Use the information in their profile to identify the user.
3. If you can't find a match for the Google user in your authentication system, the flow proceeds depending on whether you configured your Actions project in the Actions console to allow user account creation via voice or only on your website.
   • If you allow account creation via voice, validate the ID token received from Google. You can then create a user based on the profile information contained in the ID token.
   • If you don't allow account creation via voice, the user is transferred to a browser where they can load your authorization page and complete the user creation flow.

Figure 2. A visual representation of the OAuth and Google Sign-In flow when a user's information is not found in your system.

Support account creation via voice

If you allow user account creation via voice, the Assistant asks the user whether they want to do the following:

• Create a new account on your system using their Google account information, or
• Sign in to your authentication system with a different account if they have an existing non-Google account.

Allowing account creation via voice is recommended if you want to minimize the friction of the account creation flow. The user only needs to leave the voice flow if they want to sign in using an existing non-Google account.

Disallow account creation via voice

If you disallowed user account creation via voice, the Assistant opens the URL to the web site that you provided for user authentication. If the interaction is happening on a device that doesn't have a screen, the Assistant directs the user to a phone to continue the account linking flow.

Disallowing creation is recommended if:

• You do not want to allow users that have non-Google accounts to create a new user account and want them to link to their existing user accounts in your authentication system instead. For example, if you offer a loyalty program, you might want to make sure that the user doesn't lose the points accrued on their existing account.

• You need to have full control of the account creation flow. For example, you could disallow creation if you need to show your terms of service to the user during account creation.

Note: Select one of the flow options below to learn more about implementing the selected flow. If needed, the content of the guide will be reloaded to adapt to your choice.

Allow account creation via voice Disallow account creation via voice

Implement OAuth and Google Sign-In account linking

Accounts are linked with industry standard OAuth 2.0 flows. Actions on Google supports the implicit and authorization code flows.

Note: If you're implementing account linking to handle financial information, note that additional policies may apply to your Action. It can take us up to six weeks to review an Action with account linking for financial information, so factor that time in when planning your release schedule. To ease the review process, make sure you comply with the financial services policies before submitting your Action for review.

In the implicit code 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 the Assistant to your Action.

In the authorization code flow, you need two endpoints:

• The authorization endpoint, which is responsible for presenting the sign-in UI to your users that aren't already signed in and recording consent to the requested access in the form of a short-lived authorization code.
• 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.

Although the implicit code flow is simpler to implement, Google recommends that access tokens issued using the implicit flow never expire, because using token expiration with the implicit flow forces the user to link their account again. If you need token expiration for security reasons, you should strongly consider using the auth code flow instead.

Note: Please choose which OAuth2 flow you want to implement. If needed, the content of this guide reloads to adapt to your choice.

Auth code Implicit flow

Configure the project

To configure your project to use OAuth and Google Sign-In account linking, follow these steps:

1. Open the Actions console and select the project you want to use.
2. Click on the Develop tab and choose Account linking.
3. Enable the switch next to Account linking.
4. In the Account creation section, select Yes.

5. In Linking type, select OAuth & Google Sign In and Implicit.

   

6. In Client Information, do the following:

   • Assign a value to Client ID issued by your Actions to Google to identify requests coming from Google.
   • Insert the URLs for your Authorization and Token Exchange endpoints.

7. Click Save.

Implement your OAuth server

To support the OAuth 2.0 implicit flow, your service makes an authorization endpoint available by HTTPS. This endpoint is responsible for authenticating 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 your Action 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 by redirecting 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 your Action needs to perform account linking via an OAuth2 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.

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

GET https://myservice.example.com/auth?client_id=GOOGLE_CLIENT_ID&redirect_uri=REDIRECT_URI&state=STATE_STRING&response_type=token

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

     YOUR_PROJECT_ID is the ID found on the Project settings page of the Actions Console.

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 that Google will 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 will receive the access token and confirm that the state value hasn't changed. After Google has obtained an access token for your service, Google will attach the token to subsequent calls to your Action as part of the AppRequest.

Handle automatic linking

After the user gives your Action consent to access their Google profile, Google sends a request that contains a signed assertion of the Google user's identity. The assertion contains information that includes the user's Google Account ID, name, and email address. The token exchange endpoint configured for your project handles that request.

If the corresponding Google account is already present in your authentication system, your token exchange endpoint returns a token for the user. If the Google account doesn't match an existing user, your token exchange endpoint returns a user_not_found error.

The request has the following form:

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

grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer&intent=get&assertion=JWT&consent_code=CONSENT_CODE&scope=SCOPES

Your token exchange endpoint must be able to handle the following parameters:

Token endpoint parameters
grant_type	The type of token being exchanged. For these requests, this parameter has the value urn:ietf:params:oauth:grant-type:jwt-bearer.
intent	For these requests, the value of this parameter is `get`.
assertion	A JSON Web Token (JWT) that provides a signed assertion of the Google user's identity. The JWT contains information that includes the user's Google Account ID, name, and email address.
consent_code	Optional: When present, a one-time code that indicates that the user has granted consent for your Action to access the specified scopes.
scope	Optional: Any scopes you configured Google to request from users.

When your token exchange endpoint receives the linking request, it should do the following:

Validate and decode the JWT assertion

You can validate and decode the JWT assertion by using a JWT-decoding library for your language. Use Google's public keys (available in JWK or PEM format) to verify the token's signature.

Note: The keys should not be hardcoded. Instead, follow OpenID connect discovery protocol and check the cache-control header to decide how long the key should be cached.

When decoded, the JWT assertion looks like the following example:

{
  "sub": 1234567890,        // The unique ID of the user's Google Account
  "iss": "https://accounts.google.com",        // The assertion's issuer
  "aud": "123-abc.apps.googleusercontent.com", // Your server's client ID
  "iat": 233366400,         // Unix timestamp of the assertion's creation time
  "exp": 233370000,         // Unix timestamp of the assertion's expiration time
  "name": "Jan Jansen",
  "given_name": "Jan",
  "family_name": "Jansen",
  "email": "[e-mail]", // If present, the user's email address
  "locale": "en_US"
}

In addition to verifying the token's signature, verify that the assertion's issuer (iss field) is https://accounts.google.com and that the audience (aud field) is the client ID assigned to your Action.

Check if the Google account is already present in your authentication system

Check whether either of the following conditions are true:

• The Google Account ID, found in the assertion's sub field, is in your user database.
• The email address in the assertion matches a user in your user database.

If either condition is true, the user has already signed up and you can issue an access token.

If neither the Google Account ID nor the email address specified in the assertion matches a user in your database, the user hasn't signed up yet. In this case, your token exchange endpoint should reply with a HTTP 401 error, that specifies error=user_not_found, as in the following example:

HTTP/1.1 401 Unauthorized
Content-Type: application/json;charset=UTF-8

{
  "error":"user_not_found",
}

When Google receives the 401 error response with a user_not_found error, Google calls your token exchange endpoint with the value of the intent parameter set to create and sending an ID token that contains the user's profile information with the request.

通过 Google 登录功能处理账号创建

当用户需要在您的服务中创建账号时，Google 会 向令牌交换端点发送的请求 intent=create，如以下示例所示：

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

response_type=token&grant_type=urn:ietf:params:oauth:grant-type:jwt-bearer&scope=SCOPES&intent=create&consent_code=CONSENT_CODE&assertion=JWT[&NEW_ACCOUNT_INFO]

assertion 参数包含 JSON Web 令牌 (JWT)，可提供 Google 用户的身份的已签名断言。JWT 包含 其中包含用户的 Google 账号 ID、姓名和电子邮件地址 为您的服务创建一个新账号。

如需响应账号创建请求，您的令牌交换端点必须执行以下操作 以下：

Validate and decode the JWT assertion

You can validate and decode the JWT assertion by using a JWT-decoding library for your language. Use Google's public keys (available in JWK or PEM format) to verify the token's signature.

Note: The keys should not be hardcoded. Instead, follow OpenID connect discovery protocol and check the cache-control header to decide how long the key should be cached.

When decoded, the JWT assertion looks like the following example:

{
  "sub": 1234567890,        // The unique ID of the user's Google Account
  "iss": "https://accounts.google.com",        // The assertion's issuer
  "aud": "123-abc.apps.googleusercontent.com", // Your server's client ID
  "iat": 233366400,         // Unix timestamp of the assertion's creation time
  "exp": 233370000,         // Unix timestamp of the assertion's expiration time
  "name": "Jan Jansen",
  "given_name": "Jan",
  "family_name": "Jansen",
  "email": "[e-mail]", // If present, the user's email address
  "locale": "en_US"
}

In addition to verifying the token's signature, verify that the assertion's issuer (iss field) is https://accounts.google.com and that the audience (aud field) is the client ID assigned to your Action.

验证用户信息并创建新账号

请检查以下任一条件是否成立：

• Google 账号 ID 可在断言的 sub 字段中找到，也可位于您的用户数据库中。
• 断言中的电子邮件地址与用户数据库中的用户匹配。

如果满足上述任一条件，则提示用户将其现有账号关联 通过使用 HTTP 401 错误响应请求 error=linking_error，并将用户的电子邮件地址为 login_hint，如 示例：

HTTP/1.1 401 Unauthorized
Content-Type: application/json;charset=UTF-8

{
  "error":"linking_error",
  "login_hint":"[e-mail]"
}

如果以上两个条件都不满足，请使用相应信息创建一个新的用户账号 。新账号通常不会设置密码。时间是 建议您将 Google 登录功能添加到其他平台，以便用户能够 在您的应用的各个界面上通过 Google 投放广告。或者，您也可以 通过电子邮件向用户发送链接，启动密码恢复流程，以便用户设置 密码，以便在其他平台上登录。

创建完成后，发出一个访问令牌 并在 HTTPS 响应的正文，如以下示例所示：

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

Start the authentication flow

Warning: Don't give users a required account linking prompt at the start of the conversation with your Action. Instead, give unauthenticated users a guest flow to show how your Action works, and then only ask for account linking if it's necessary to proceed. If users are leaving the Action consistently because of account linking issues, Google will not actively promote the Action, which may decrease the Action's user traffic.

Note that only verified users can perform account linking. If the user is a guest, account linking will fail. Learn about identifying and handling guest users.

Use the Account Sign-in helper intent to start the authentication flow.

Dialogflow (Node.js)

const app = dialogflow({
  // REPLACE THE PLACEHOLDER WITH THE CLIENT_ID OF YOUR ACTIONS PROJECT
  clientId: CLIENT_ID,
})

// Intent that starts the account linking flow.
app.intent('Start Signin', conv => {
  conv.ask(new SignIn('To get your account details'))
})

Dialogflow (Java)

private String clientId = "<your_client_id>";

@ForIntent("Start Signin")
public ActionResponse text(ActionRequest request) {
  ResponseBuilder rb = getResponseBuilder(request);
  return rb.add(new SignIn().setContext("To get your account details")).build();
}

Actions SDK (Node.js)

const app = actionssdk({
  clientId: CLIENT_ID,
})

app.intent('Start Signin', conv => {
  conv.ask(new SignIn('To get your account details'))
})

Actions SDK (Java)

private String clientId = "<your_client_id>";

@ForIntent("actions.intent.TEXT")
public ActionResponse text(ActionRequest request) {
  ResponseBuilder rb = getResponseBuilder(request);
  return rb.add(new SignIn().setContext("To get your account details")).build();
}

Handle data access requests

If the Assistant request contains an access token, check first that the access token is valid and not expired and then retrieve from your user account database the user account associated with the token.