The OAuth-based Google Sign-in "Streamlined" 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.
To perform account linking with the Streamlined linking type, follow these general steps:
- First, ask the user to give consent to access their Google profile.
- Use the information in their profile to identify the user.
- 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.
Support account creation via voice
If you allow user account creation via voice, 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, 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, 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.
Implement OAuth-based Google Sign-in "Streamlined" linking
Accounts are linked with industry standard OAuth 2.0 flows. Actions on Google supports the implicit and authorization code flows.
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:
- 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.
- 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.
Configure the project
To configure your project to use Streamlined linking, follow these steps:
- Open the Actions console and select the project you want to use.
- Click on the Develop tab and choose Account linking.
- Enable the switch next to Account linking.
- In the Account creation section, select No, I only want to allow account creation on my website.
In Linking type, select OAuth & Google Sign In and Authorization code.
In Client Information, do the following:
- Assign a value to Client ID issued by your Actions to Google to identify requests coming from Google.
- Take note of the value of Client ID issued by Google to your Actions.
- Insert the URLs for your Authorization and Token Exchange endpoints.
Click Save.
Implement your OAuth server
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 the Action user to access your service.
When your Action 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.
OAuth 2.0 auth code flow session initiated by Google has the following flow:
- Google opens your authorization endpoint in the user's browser. If the flow started on a voice-only device for an Action, Google would transfer the execution to a phone.
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.
Your service creates an authorization code and returns it to Google by redirecting the user's browser back to Google with the authorization code attached to the request.
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.
After the user has completed the account linking flow, every subsequent request sent from the Assistant to your fulfillment webhook contains an access token.
Handle authorization requests
When your Action needs to perform account linking via an 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 Google client ID you registered with 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 string code . |
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&scope=REQUESTED_SCOPES&response_type=code
For your authorization endpoint to handle sign-in requests, do the following steps:
Verify that the
client_id
matches the Google client ID you registered with Google, and that theredirect_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
iscode
.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.
Generate an authorization code that Google will 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.
Confirm that the URL specified by the
redirect_uri
parameter has the following form: YOUR_PROJECT_ID is the ID found on the Project settings page of the Actions Console.https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID
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 thecode
andstate
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. Either
authorization_code or refresh_token . |
code |
When grant_type=authorization_code , 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 , 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 executing the following steps:
- Verify that the
client_id
identifies the request origin as an authorized origin, and that theclient_secret
matches the expected value. - Verify the following:
- The authorization code is valid and not expired, and the client ID specified in the request matches the client ID associated with the authorization code.
- The URL specified by the
redirect_uri
parameter is identical to the value used in the initial authorization request.
- If you cannot verify all of the above criteria, return an HTTP
400 Bad Request error with
{"error": "invalid_grant"}
as the body. - Otherwise, using the user ID from the authorization code, 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 (typically an hour after you issue the token). Refresh tokens do not expire.
- 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 executing the following steps:
- Verify that the
client_id
identifies the request origin as Google, and that theclient_secret
matches the expected value. - 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.
- If you cannot verify all of the above criteria, return an HTTP
400 Bad Request error with
{"error": "invalid_grant"}
as the body. - 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).
- Return the following JSON object in the body of the HTTPS
response:
{ "token_type": "Bearer", "access_token": "ACCESS_TOKEN", "expires_in": SECONDS_TO_EXPIRATION }
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.
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": "jan@gmail.com", // 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", }
user_not_found
error, Google
sends the user to your authorization endpoint.
Design the voice user interface for the authentication flow
Check if the user is verified and start the account linking flow
- Open your Actions Builder project in the Actions Console.
- Create a new scene to start account linking in your Action:
- Click Scenes.
- Click the add (+) icon to add a new scene.
- In the newly created scene, click the add add icon for Conditions.
- Add a condition that checks if the user associated with the conversation is a
a verified user. If the check fails, your Action can't perform account linking
during the conversation, and should fall back to providing access to
functionality that doesn't require account linking.
- In the
Enter new expression
field under Condition, enter the following logic:user.verificationStatus != "VERIFIED"
- Under Transition, select a scene that doesn't require account linking or a scene that is the entry point to guest-only functionality.
- In the
- Click the add add icon for Conditions.
- Add a condition to trigger an account linking flow if the user doesn't have
an associated identity.
- In the
Enter new expression
field under Condition, enter the following logic::user.verificationStatus == "VERIFIED"
- Under Transition, select the Account Linking system scene.
- Click Save.
- In the
After saving, a new account linking system scene called <SceneName>_AccountLinking
is added to your project.
Customize the account linking scene
- Under Scenes, select the account linking system scene.
- Click Send prompt and add a short sentence to describe to the user why the Action needs to access their identity (for example "To save your preferences").
- Click Save.
- Under Conditions, click If user successfully completes account linking.
- Configure how the flow should proceed if the user agrees to link their account. For example, call the webhook to process any custom business logic required and transition back to the originating scene.
- Click Save.
- Under Conditions, click If user cancels or dismisses account linking.
- Configure how the flow should proceed if the user doesn't agree to link their account. For example, send an acknowledging message and redirect to scenes that provide functionality that doesn't require account linking.
- Click Save.
- Under Conditions, click If system or network error occurs.
- Configure how the flow should proceed if the account linking flow can't be completed because of system or network errors. For example, send an acknowledging message and redirect to scenes that provide functionality that doesn't require account linking.
- Click Save.
Handle data access requests
If you use information contained in the Google ID token to create an account for the user, check first if the user asserted by the ID token included in the Assistant request matches an existing user in your db.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.