Vinculación de Cuentas de Google con OAuth

Las cuentas se vinculan con los flujos implícitos y de código de autorización de OAuth 2.0 estándar de la industria. Tu servicio debe admitir extremos de autorización y de intercambio de tokens que cumplan con OAuth 2.0.

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.

Create the project

To create your project to use account linking:

1. Go to the Google API Console.
2. Click Create project.
3. Enter a name or accept the generated suggestion.
4. Confirm or edit any remaining fields.
5. Click Create.

To view your project ID:

1. Go to the Google API Console.
2. Find your project in the table on the landing page. The project ID appears in the ID column.

Configure your OAuth Consent Screen

The Google Account Linking process includes a consent screen which tells users the application requesting access to their data, what kind of data they are asking for and the terms that apply. You will need to configure your OAuth consent screen before generating a Google API client ID.

1. Open the OAuth consent screen page of the Google APIs console.
2. If prompted, select the project you just created.

3. On the "OAuth consent screen" page, fill out the form and click the “Save” button.

   Application name: The name of the application asking for consent. The name should accurately reflect your application and be consistent with the application name users see elsewhere. The application name will be shown on the Account Linking consent screen.

   Application logo: An image on the consent screen that will help users recognize your app. The logo is shown on Account linking consent screen and on account settings

   Support email: For users to contact you with questions about their consent.

   Scopes for Google APIs: Scopes allow your application to access your user's private Google data. For the Google Account Linking use case, default scope (email, profile, openid) is sufficient, you don’t need to add any sensitive scopes. It is generally a best practice to request scopes incrementally, at the time access is required, rather than up front. Learn more.

   Authorized domains: To protect you and your users, Google only allows applications that authenticate using OAuth to use Authorized Domains. Your applications' links must be hosted on Authorized Domains. Learn more.

   Application Homepage link: Home page for your application. Must be hosted on an Authorized Domain.

   Application Privacy Policy link: Shown on Google Account Linking consent screen. Must be hosted on an Authorized Domain.

   Application Terms of Service link (Optional): Must be hosted on an Authorized Domain.

   

   Figure 1. Google Account Linking Consent Screen for a fictitious Application, Tunery

4. Check "Verification Status", if your application needs verification then click the "Submit For Verification" button to submit your application for verification. Refer to OAuth verification requirements for details.

Implementa tu servidor de OAuth

Para admitir el flujo implícito de OAuth 2.0, tu servicio hace una autorización de destino disponible a través de HTTPS. Este extremo es responsable de la autenticación y obtener el consentimiento de los usuarios para acceder a los datos. El extremo de autorización presenta una IU de acceso a los usuarios que aún no accedieron y registra el acceso solicitado.

Cuando una aplicación de Google necesita llamar a una de las APIs autorizadas de tu servicio Google usa este extremo a fin de obtener permiso de los usuarios para llamar a estas APIs por ellos.

Una sesión típica de flujo implícito de OAuth 2.0 que inicia Google tiene la siguiente flujo:

1. Google abre el extremo de autorización en el navegador del usuario. El usuario accede a la cuenta, si aún no lo hizo, y le otorga permiso a Google para acceder a sus datos con tu API, si aún no han otorgado permiso.
2. Tu servicio crea un token de acceso y lo devuelve a Google. Para ello, vuelve a redireccionar el navegador del usuario a Google con el permiso de acceso. token asociado a la solicitud.
3. Google llama a las APIs de tu servicio y adjunta el token de acceso con cada solicitud. Tu servicio verifica que el token de acceso otorgue a Google autorización para acceder a la API y, luego, completa la llamada a la API.

Maneja solicitudes de autorización

Cuando una aplicación de Google necesita vincular cuentas mediante OAuth 2.0 implícito, Google envía al usuario a tu extremo de autorización con un que incluya los siguientes parámetros:

Por ejemplo, si tu extremo de autorización está disponible en https://myservice.example.com/auth, una solicitud podría verse de la siguiente manera:

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

Para que tu extremo de autorización controle las solicitudes de acceso, haz lo siguiente pasos:

1. Verifica los valores client_id y redirect_uri para evita que se otorgue acceso a apps cliente no deseadas o configuradas incorrectamente:

   • Confirma que client_id coincida con el ID de cliente que asignados a Google.
   • Confirma que la URL especificada por redirect_uri tiene la siguiente forma:

     https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID
     https://oauth-redirect-sandbox.googleusercontent.com/r/YOUR_PROJECT_ID
     

2. Verifica si el usuario accedió a tu servicio. Si el usuario no está firmado completa el flujo de acceso o registro del servicio.

3. Genera un token de acceso para que Google acceda a tu API. El el token de acceso puede ser cualquier valor de cadena, pero debe representar de forma única usuario y cliente para el que es el token y no se debe poder adivinar.

4. Envía una respuesta HTTP que redirecciona el navegador del usuario a la URL especificadas por el parámetro redirect_uri. Incluye todos los siguientes parámetros en el fragmento de URL:

   • access_token: El token de acceso que acabas de generar
   • token_type: Es la cadena bearer.
   • state: Es el valor de estado sin modificar del original. solicitud

   El siguiente es un ejemplo de la URL resultante:

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

El controlador de redireccionamiento de OAuth 2.0 de Google recibe el token de acceso y confirma que el valor de state no haya cambiado. Después de que Google obtiene una token de acceso para tu servicio, Google lo conectará a las llamadas posteriores a tus APIs de servicio.

Handle userinfo requests

The userinfo endpoint is an OAuth 2.0 protected resource that return claims about the linked user. Implementing and hosting the userinfo endpoint is optional, except for the following use cases:

• Linked Account Sign-In with Google One Tap.
• Frictionless subscription on AndroidTV.

After the access token has been successfully retrieved from your token endpoint, Google sends a request to your userinfo endpoint to retrieve basic profile information about the linked user.

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

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

For your userinfo endpoint to handle requests, do the following steps:

1. Extract access token from the Authorization header and return information for the user associated with the access token.
2. If the access token is invalid, return an HTTP 401 Unauthorized error with using the WWW-Authenticate Response Header. Below is an example of a userinfo error response:

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

   If a 401 Unauthorized, or any other unsuccessful error response is returned during the linking process, the error will be non-recoverable, the retrieved token will be discarded and the user will have to initiate the linking process again.

3. If the access token is valid, return and HTTP 200 response with the following JSON object in the body of the HTTPS response:

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

   If your userinfo endpoint returns an HTTP 200 success response, the retrieved token and claims are registered against the user's Google account.

   userinfo endpoint response
   sub	A unique ID that identifies the user in your system.
   email	Email address of the user.
   given_name	Optional: First name of the user.
   family_name	Optional: Last name of the user.
   name	Optional: Full name of the user.
   picture	Optional: Profile picture of the user.

Cómo validar la implementación

Puedes validar tu implementación con la herramienta OAuth 2.0 Playground.

En la herramienta, sigue estos pasos:

1. Haz clic en Configuración settings para abrir la ventana de configuración de OAuth 2.0.
2. En el campo Flujo de OAuth, selecciona Del cliente.
3. En el campo Extremos de OAuth, selecciona Personalizado.
4. Especifica tu extremo de OAuth 2.0 y el ID de cliente que le asignaste a Google en los campos correspondientes.
5. En la sección Paso 1, no selecciones ningún alcance de Google. En su lugar, deja este campo en blanco o escribe un alcance válido para tu servidor (o una cadena arbitraria si no usas permisos de OAuth). Cuando termines, haz clic en Autorizar APIs.
6. En las secciones Paso 2 y Paso 3, revisa el flujo de OAuth 2.0 y verifica que cada paso funcione según lo previsto.

Puedes validar tu implementación con la herramienta de demostración de vinculación de Cuentas de Google.

En la herramienta, sigue estos pasos:

1. Haz clic en el botón Acceder con Google.
2. Elige la cuenta que quieres vincular.
3. Ingresa el ID del servicio.
4. De forma opcional, ingresa uno o más permisos para los que solicitarás acceso.
5. Haz clic en Iniciar demostración.
6. Cuando se te solicite, confirma que puedes dar tu consentimiento y rechazar la solicitud de vinculación.
7. Confirma que se te redireccionó a tu plataforma.