OAuth로 Google 계정 연결

계정은 업계 표준 OAuth 2.0 암시적 흐름 및 승인 코드 흐름을 사용하여 연결됩니다. 서비스가 OAuth 2.0을 준수하는 승인 및 토큰 교환 엔드포인트를 지원해야 합니다.

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.

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.

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.

프로젝트 만들기

계정 연결을 사용할 프로젝트를 만들려면 다음 단계를 따르세요.

  2. 프로젝트 만들기를 클릭합니다.
  3. 이름을 입력하거나 생성된 추천을 수락합니다.
  4. 나머지 필드를 확인하거나 수정합니다.
  5. 만들기를 클릭합니다.

프로젝트 ID를 확인하려면 다음 단계를 따르세요.

  2. 방문 페이지의 표에서 프로젝트를 찾습니다. 프로젝트 ID는 ID 열에 표시됩니다.

Google 계정 연결 프로세스에는 사용자에게 데이터 액세스를 요청하는 애플리케이션, 요청하는 데이터의 종류, 적용되는 약관을 알려주는 동의 화면이 포함됩니다. Google API 클라이언트 ID를 생성하기 전에 OAuth 동의 화면을 구성해야 합니다.

  1. Google API 콘솔의 OAuth 동의 화면 페이지를 엽니다.
  2. 메시지가 표시되면 방금 만든 프로젝트를 선택합니다.

  3. 'OAuth 동의 화면' 페이지에서 양식을 작성하고 '저장' 버튼을 클릭합니다.

    애플리케이션 이름: 동의를 요청하는 애플리케이션의 이름입니다. 이름은 애플리케이션을 정확하게 반영해야 하며 사용자가 다른 곳에서 보는 애플리케이션 이름과 일치해야 합니다. 애플리케이션 이름은 계정 연결 동의 화면에 표시됩니다.

    애플리케이션 로고: 사용자가 앱을 인식하는 데 도움이 되는 동의 화면의 이미지입니다. 로고는 계정 연결 동의 화면과 계정 설정에 표시됩니다.

    지원 이메일: 사용자가 동의에 대해 문의할 수 있습니다.

    Google API 범위: 범위를 사용하면 애플리케이션이 사용자의 비공개 Google 데이터에 액세스할 수 있습니다. Google 계정 연결 사용 사례의 경우 기본 범위 (이메일, 프로필, openid)로 충분하며 민감한 범위를 추가할 필요가 없습니다. 일반적으로 액세스가 필요한 시점에 미리 요청하는 대신 점진적으로 범위를 요청하는 것이 좋습니다. 자세히 알아보기

    승인된 도메인: 나와 내 사용자를 보호하기 위해 Google에서는 OAuth를 사용하여 인증하는 애플리케이션만 승인된 도메인을 사용할 수 있도록 허용합니다. 애플리케이션의 링크는 승인된 도메인에서 호스팅되어야 합니다. 자세히 알아보기

    애플리케이션 홈페이지 링크: 애플리케이션의 홈페이지입니다. 승인된 도메인에서 호스팅해야 합니다.

    애플리케이션 개인정보처리방침 링크: Google 계정 연결 동의 화면에 표시됩니다. 승인된 도메인에서 호스팅해야 합니다.

    애플리케이션 서비스 약관 링크 (선택사항): 승인된 도메인에서 호스팅되어야 합니다.

    그림 1. 가상 애플리케이션 Tunery의 Google 계정 연결 동의 화면

  4. '인증 상태'를 확인합니다. 애플리케이션에 인증이 필요한 경우 '인증을 위해 제출' 버튼을 클릭하여 인증을 위해 애플리케이션을 제출합니다. 자세한 내용은 OAuth 인증 요구사항을 참고하세요.

OAuth 서버 구현

To support the OAuth 2.0 implicit flow, your service makes an authorization endpoint available by HTTPS. This endpoint is responsible for authentication 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 a Google application 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. To do so, redirect 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 a Google application needs to perform account linking via an OAuth 2.0 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.
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&response_type=token&user_locale=LOCALE

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

  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 for Google to 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 receives the access token and confirms that the state value hasn't changed. After Google has obtained an access token for your service, Google attaches the token to subsequent calls to your service APIs.

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:

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.

userinfo endpoint request headers
Authorization header The access token of type Bearer.

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.

구현 확인

OAuth 2.0 플레이그라운드 도구를 사용하여 구현을 검증할 수 있습니다.

도구에서 다음 단계를 수행합니다.

  1. 구성 을 클릭하여 OAuth 2.0 구성 창을 엽니다.
  2. OAuth 흐름 입력란에서 클라이언트 측을 선택합니다.
  3. OAuth 엔드포인트 필드에서 맞춤을 선택합니다.
  4. 해당 필드에 OAuth 2.0 엔드포인트와 Google에 할당한 클라이언트 ID를 지정합니다.
  5. 1단계 섹션에서 Google 범위를 선택하지 않습니다. 대신 이 필드를 비워 두거나 서버에 유효한 범위 (또는 OAuth 범위를 사용하지 않는 경우 임의의 문자열)를 입력합니다. 완료되면 API 승인을 클릭합니다.
  6. 2단계 및 3단계 섹션에서 OAuth 2.0 흐름을 진행하고 각 단계가 의도한 대로 작동하는지 확인합니다.

Google 계정 연결 데모 도구를 사용하여 구현을 확인할 수 있습니다.

도구에서 다음 단계를 수행합니다.

  1. Google 계정으로 로그인 버튼을 클릭합니다.
  2. 연결할 계정을 선택합니다.
  3. 서비스 ID를 입력합니다.
  4. 원하는 경우 액세스를 요청할 범위를 하나 이상 입력합니다.
  5. 데모 시작을 클릭합니다.
  6. 메시지가 표시되면 연결 요청에 동의하고 거부할 수 있음을 확인합니다.
  7. 플랫폼으로 리디렉션되는지 확인합니다.