Vinculação simplificada com o OAuth e o Login do Google

Visão geral

A vinculação simplificada do Login do Google baseado em OAuth adiciona o Login do Google aos Vinculação do OAuth. Isso proporciona uma experiência de vinculação perfeita para usuários do Google e também permite a criação de contas, o que permite que o usuário crie uma nova conta no seu serviço usando a própria Conta do Google.

Para vincular a conta com o OAuth e o Login do Google, siga estas instruções etapas:

1. Primeiro, peça ao usuário que dê consentimento para acessar o perfil do Google dele.
2. Use as informações no perfil para verificar se a conta de usuário existe.
3. Vincule as contas dos usuários atuais.
4. Se você não encontrar uma correspondência para o usuário do Google no seu sistema de autenticação, validar o token de ID recebido do Google. Em seguida, é possível criar um nas informações de perfil contidas no token de ID.

Figura 1. Vinculação de contas no smartphone do usuário com a vinculação simplificada

Requisitos para a vinculação simplificada

• Implemente o fluxo de vinculação OAuth da Web básica. Seu serviço precisa ser compatível com OAuth 2.0 autorização e troca de token.
• O endpoint de troca de token precisa oferecer suporte a declarações JSON Web Token (JWT) e implementar as intents check, create e get.

• Registre seu ID do cliente da API do Google.

Implementar seu servidor OAuth

Seu endpoint de troca de token precisa oferecer suporte às intents check, create e get. Confira abaixo as etapas concluídas no fluxo de vinculação de contas e indique quando as diferentes intents são chamadas:

1. O usuário tem uma conta no seu sistema de autenticação? (O usuário decide selecionando SIM ou NÃO)
   1. SIM : o usuário utiliza o e-mail associado à Conta do Google para fazer login na sua plataforma? (O usuário decide selecionando SIM ou NÃO)
      1. SIM : o usuário tem uma conta correspondente no sistema de autenticação? (check intent é chamado para confirmar)
         1. SIM : get intent será chamado, e a conta será vinculada se a intent recebida retornar.
         2. NÃO : criar uma nova conta? (O usuário decide selecionando SIM ou NÃO)
            1. SIM : create intent será chamado, e a conta será vinculada se a intent criar retornar.
            2. NÃO : o fluxo de OAuth da Web é acionado, o usuário é direcionado para o navegador e tem a opção de vincular com um e-mail diferente.
      2. NÃO : o fluxo OAuth da Web é acionado, o usuário é direcionado para o navegador e tem a opção de vincular com um e-mail diferente.
   2. NÃO : o usuário tem uma conta correspondente no seu sistema de autenticação? (check intent é chamado para confirmar)
      1. SIM : get intent será chamado, e a conta será vinculada se a intent recebida retornar.
      2. NÃO : create intent é chamado, e a conta é vinculada se a intent de criação retornar.

Check for an existing user account (check intent)

After the user gives 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 responds with account_found=true. If the Google account doesn't match an existing user, your token exchange endpoint returns an HTTP 404 Not Found error with account_found=false.

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=check&assertion=JWT&scope=SCOPES&client_id=GOOGLE_CLIENT_ID&client_secret=GOOGLE_CLIENT_SECRET

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

To respond to the check intent requests, your token exchange endpoint must perform the following steps:

• Validate and decode the JWT assertion.
• Check if the Google account is already present in your authentication system.

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 formats, 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
  "email_verified": true,   // true, if Google has verified the email address
  "hd": "example.com",      // If present, the host domain of the user's GSuite email address
                            // If present, a URL to user's profile picture
  "picture": "https://lh3.googleusercontent.com/a-/AOh14GjlTnZKHAeb94A-FmEbwZv7uJD986VOF1mJGb2YYQ",
  "locale": "en_US"         // User's locale, from browser or phone settings
}

In addition to verifying the token's signature, verify that the assertion's issuer (iss field) is https://accounts.google.com, that the audience (aud field) is your assigned client ID, and that the token has not expired (exp field).

Using the email, email_verified and hd fields you can determine if Google hosts and is authoritative for an email address. In cases where Google is authoritative the user is currently known to be the legitimate account owner and you may skip password or other challenges methods. Otherwise, these methods can be used to verify the account prior to linking.

Cases where Google is authoritative:

• email has a @gmail.com suffix, this is a Gmail account.
• email_verified is true and hd is set, this is a G Suite account.

Users may register for Google Accounts without using Gmail or G Suite. When email does not contain a @gmail.com suffix and hd is absent Google is not authoritative and password or other challenge methods are recommended to verify the user. email_verified can also be true as Google initially verified the user when the Google account was created, however ownership of the third party email account may have since changed.

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. In that case, return a response like the following:

HTTP/1.1 200 Success
Content-Type: application/json;charset=UTF-8

{
  "account_found":"true",
}

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 needs to reply with a HTTP 404 error that specifies "account_found": "false", as in the following example:

HTTP/1.1 404 Not found
Content-Type: application/json;charset=UTF-8

{
  "account_found":"false",
}

Handle automatic linking (get intent)

After the user gives 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 linking_error error and optional login_hint.

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&scope=SCOPES&client_id=GOOGLE_CLIENT_ID&client_secret=GOOGLE_CLIENT_SECRET

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

To respond to the get intent requests, your token exchange endpoint must perform the following steps:

• Validate and decode the JWT assertion.
• Check if the Google account is already present in your authentication system.

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 formats, 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
  "email_verified": true,   // true, if Google has verified the email address
  "hd": "example.com",      // If present, the host domain of the user's GSuite email address
                            // If present, a URL to user's profile picture
  "picture": "https://lh3.googleusercontent.com/a-/AOh14GjlTnZKHAeb94A-FmEbwZv7uJD986VOF1mJGb2YYQ",
  "locale": "en_US"         // User's locale, from browser or phone settings
}

In addition to verifying the token's signature, verify that the assertion's issuer (iss field) is https://accounts.google.com, that the audience (aud field) is your assigned client ID, and that the token has not expired (exp field).

Using the email, email_verified and hd fields you can determine if Google hosts and is authoritative for an email address. In cases where Google is authoritative the user is currently known to be the legitimate account owner and you may skip password or other challenges methods. Otherwise, these methods can be used to verify the account prior to linking.

Cases where Google is authoritative:

• email has a @gmail.com suffix, this is a Gmail account.
• email_verified is true and hd is set, this is a G Suite account.

Users may register for Google Accounts without using Gmail or G Suite. When email does not contain a @gmail.com suffix and hd is absent Google is not authoritative and password or other challenge methods are recommended to verify the user. email_verified can also be true as Google initially verified the user when the Google account was created, however ownership of the third party email account may have since changed.

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 an account is found for the user, issue an access token and return the values in a JSON object in the body of your HTTPS response, like in the following example:

{
  "token_type": "Bearer",
  "access_token": "ACCESS_TOKEN",

  "expires_in": SECONDS_TO_EXPIRATION
}

In some cases, account linking based on ID token might fail for the user. If it does so for any reason, your token exchange endpoint needs to reply with a HTTP 401 error that specifies error=linking_error, as the following example shows:

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

{
  "error":"linking_error",
  "login_hint":"foo@bar.com"
}

When Google receives a 401 error response with linking_error, Google sends the user to your authorization endpoint with login_hint as a parameter. The user completes account linking using the OAuth linking flow in their browser.

Processar a criação de contas pelo Login do Google (criar intent)

Quando um usuário precisa criar uma conta no seu serviço, o Google faz uma solicitação ao endpoint de troca de token que especifica intent=create.

A solicitação tem o seguinte formato:

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&assertion=JWT&client_id=GOOGLE_CLIENT_ID&client_secret=GOOGLE_CLIENT_SECRET

Seu endpoint de troca de token precisa lidar com os seguintes parâmetros:

O JWT no parâmetro assertion contém o ID da Conta do Google do usuário, nome e endereço de e-mail, que podem ser usados para criar uma nova conta no seu serviço.

Para responder às solicitações da intent create, o endpoint de troca de token precisa executar as seguintes etapas:

• Valide e decodifique a declaração do JWT.
• Valide as informações do usuário e crie uma nova conta.

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 formats, 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
  "email_verified": true,   // true, if Google has verified the email address
  "hd": "example.com",      // If present, the host domain of the user's GSuite email address
                            // If present, a URL to user's profile picture
  "picture": "https://lh3.googleusercontent.com/a-/AOh14GjlTnZKHAeb94A-FmEbwZv7uJD986VOF1mJGb2YYQ",
  "locale": "en_US"         // User's locale, from browser or phone settings
}

In addition to verifying the token's signature, verify that the assertion's issuer (iss field) is https://accounts.google.com, that the audience (aud field) is your assigned client ID, and that the token has not expired (exp field).

Using the email, email_verified and hd fields you can determine if Google hosts and is authoritative for an email address. In cases where Google is authoritative the user is currently known to be the legitimate account owner and you may skip password or other challenges methods. Otherwise, these methods can be used to verify the account prior to linking.

Cases where Google is authoritative:

• email has a @gmail.com suffix, this is a Gmail account.
• email_verified is true and hd is set, this is a G Suite account.

Users may register for Google Accounts without using Gmail or G Suite. When email does not contain a @gmail.com suffix and hd is absent Google is not authoritative and password or other challenge methods are recommended to verify the user. email_verified can also be true as Google initially verified the user when the Google account was created, however ownership of the third party email account may have since changed.

Valide as informações do usuário e crie uma nova conta

Verifique se uma das condições a seguir é verdadeira:

• O ID da Conta do Google, encontrado no campo sub da declaração, está no seu nome de usuário no seu banco de dados.
• O endereço de e-mail na declaração corresponde a um usuário no seu banco de dados de usuários.

Se alguma das condições for verdadeira, solicite que o usuário vincule a conta atual com a Conta do Google. Para isso, responda à solicitação com um erro HTTP 401 que especifica error=linking_error e dá o endereço de e-mail do usuário como o login_hint. Veja a seguir um exemplo de resposta:

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

{
  "error":"linking_error",
  "login_hint":"foo@bar.com"
}

Quando o Google recebe uma resposta de erro 401 com linking_error, ele envia o usuário ao endpoint de autorização com login_hint como parâmetro. A o usuário conclui a vinculação da conta usando o fluxo de vinculação OAuth no navegador.

Se nenhuma das condições for verdadeira, crie uma nova conta de usuário com as informações. fornecidos no JWT. Contas novas geralmente não têm uma senha definida. Está recomendamos que você adicione o Login do Google a outras plataformas para permitir que os usuários fazer login com o Google em todas as plataformas do seu aplicativo. Você também pode pode enviar ao usuário por e-mail um link que inicie o fluxo de recuperação de senha para permitir que o que o usuário defina uma senha para fazer login em outras plataformas.

Quando a criação for concluída, emita um token de acesso e retorna os valores em um objeto JSON o corpo da sua resposta HTTPS, como no exemplo a seguir:

{
  "token_type": "Bearer",
  "access_token": "ACCESS_TOKEN",

  "expires_in": SECONDS_TO_EXPIRATION
}

Receber seu ID do cliente da API do Google

Será necessário fornecer o ID do cliente da API do Google durante o processo de registro da vinculação de contas.

Para conseguir o ID do cliente da API usando o projeto que você criou durante as etapas de vinculação OAuth. Para isso, siga estas etapas:

1. Abra a página Credenciais do Console de APIs do Google.

2. Crie ou selecione um projeto de APIs do Google.

   Se o projeto não tiver um ID do cliente para o tipo de aplicativo da Web, clique em Criar credenciais > ID do cliente OAuth para criar um. Certifique-se de incluir o domínio do site na caixa Origens JavaScript autorizadas. Quando você realiza testes ou desenvolvimentos locais, é preciso adicionar http://localhost e http://localhost:<port_number> no campo Origens JavaScript autorizadas.

Como validar a implementação

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.