アカウントは、業界標準の OAuth 2.0 インプリシット フローと認可コードフローを使用してリンクされます。サービスは、OAuth 2.0 準拠の認可エンドポイントとトークン交換エンドポイントをサポートする必要があります。
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:
- 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.
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
- 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:
Display Google's Privacy Policy. Include a link to Google’s Privacy Policy on the consent screen.
Data to be shared. Use clear and concise language to tell the user what data of theirs Google requires and why.
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.
Ability to cancel. Provide a way for users to go back or cancel, if they choose not to link.
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.
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.
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.
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.
プロジェクトを作成する
アカウントのリンクを使用するプロジェクトを作成するには:
- Go to the Google API Console.
- [ プロジェクトを作成]をクリックします 。
- 名前を入力するか、生成された提案を受け入れます。
- 残りのフィールドを確認または編集します。
- 作成をクリックします 。
プロジェクトIDを表示するには:
- Go to the Google API Console.
- ランディングページの表でプロジェクトを見つけます。 ID列にプロジェクトIDが表示されます。
OAuth 同意画面を構成する
Google アカウントのリンクのプロセスには、データへのアクセスをリクエストするアプリがユーザーに対し、どのようなデータを要求し、適用される規約があるかを伝える同意画面が含まれます。Google API クライアント ID を生成する前に、OAuth 同意画面を構成する必要があります。
- Google API コンソールの OAuth 同意画面ページを開きます。
- プロンプトが表示されたら、作成したプロジェクトを選択します。
[OAuth 同意画面] ページで、フォームに記入して [保存] ボタンをクリックします。
アプリケーション名: 同意を求めるアプリの名前。名前は、アプリを正確に反映し、ユーザーが他の場所で目にするアプリ名と一貫している必要があります。アプリケーション名は、アカウントのリンクの同意画面に表示されます。
アプリのロゴ: ユーザーがアプリを認識できるように、同意画面に表示する画像。ロゴは、アカウントのリンクに関する同意画面とアカウント設定に表示されます。
サポートメール: ユーザーが同意について問い合わせる際に使用するメールです。
Google API のスコープ: スコープを使用すると、アプリケーションがユーザーの非公開の Google データにアクセスできるようになります。Google アカウントのリンクのユースケースでは、デフォルトのスコープ(email、profile、openid)で十分であり、機密性の高いスコープを追加する必要はありません。通常、事前にではなく、アクセスが必要になったときにスコープを段階的にリクエストすることをおすすめします。詳細
承認済みドメイン: デベロッパーとユーザーを保護するため、Google では OAuth を使用して認証するアプリケーションのみに承認済みドメインの使用を許可しています。アプリのリンクは、承認済みドメインでホストする必要があります。詳細
アプリケーションのホームページへのリンク: アプリケーションのホームページ。承認済みドメインでホストされている必要があります。
アプリケーションのプライバシー ポリシーのリンク: Google アカウントのリンクの同意画面に表示されます。承認済みドメインでホストされている必要があります。
アプリケーションの利用規約へのリンク(省略可): 承認済みドメインでホストされている必要があります。
図 1. 架空のアプリ「Tunery」の Google アカウントのリンクに関する同意画面
[確認ステータス] を確認します。アプリの確認が必要な場合は、[確認のために送信] ボタンをクリックして確認のためにアプリを送信します。詳しくは、OAuth 検証の要件をご覧ください。
OAuth サーバーを実装する
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 a user to access your service.
When a Google application 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.
An OAuth 2.0 authorization 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 transfers 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. To do so, redirect 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 Google contains an access token.
Handle authorization requests
When you need to perform account linking using the 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 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. |
scope |
Optional: A space-delimited set of scope strings that specify the data Google is requesting authorization for. |
response_type |
The type of value to return in the response. For the OAuth 2.0
authorization code flow, the response type is always code .
|
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&scope=REQUESTED_SCOPES&response_type=code&user_locale=LOCALE
For your authorization endpoint to handle sign-in requests, do the following steps:
- Verify that the
client_id
matches the Client ID you assigned to 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 theresponse_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 for Google to 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:https://oauth-redirect.googleusercontent.com/r/YOUR_PROJECT_ID https://oauth-redirect-sandbox.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. It's either
authorization_code or refresh_token . |
code |
When grant_type=authorization_code , this parameter is 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 , this parameter is 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 by 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 that the authorization code is valid and not expired, and that the client ID specified in the request matches the client ID associated with the authorization code.
- Confirm that the URL specified by the
redirect_uri
parameter is identical to the value used in the initial authorization request. - If you can't 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 authorization code to 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, which is typically an hour after you issue the token. Refresh tokens don't 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 by 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 can't 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 }
userinfo リクエストを処理する
userinfo エンドポイントは、OAuth 2.0 で保護されたリソースで、リンクされたユーザーに関するクレームを返します。userinfo エンドポイントの実装とホストは任意ですが、以下のユースケースを除きます。
- Google One タップによるリンクされたアカウントへのログイン。
- Android TV のスムーズな定期購入。
トークン エンドポイントからアクセス トークンが正常に取得されると、Google は、リンクされたユーザーに関する基本的なプロフィール情報を取得するためのリクエストを userinfo エンドポイントに送信します。
userinfo エンドポイント リクエスト ヘッダー | |
---|---|
Authorization header |
Bearer タイプのアクセス トークン。 |
たとえば、userinfo エンドポイントが
https://myservice.example.com/userinfo
の場合、リクエストは次のようになります。
GET /userinfo HTTP/1.1 Host: myservice.example.com Authorization: Bearer ACCESS_TOKEN
userinfo エンドポイントでリクエストを処理するには、次の手順を行います。
- Authorization ヘッダーからアクセス トークンを抽出し、そのアクセス トークンに関連付けられたユーザーの情報を返します。
- アクセス トークンが無効な場合は、
WWW-Authenticate
レスポンス ヘッダーを使用して HTTP 401 Unauthorized エラーを返します。userinfo エラー レスポンスの例を次に示します。HTTP/1.1 401 Unauthorized WWW-Authenticate: error="invalid_token", error_description="The Access Token expired"
リンク処理中に 401 Unauthorized またはその他の失敗したエラー レスポンスが返された場合、そのエラーは修復不能となり、取得したトークンは破棄されるため、ユーザーはリンク処理をやり直す必要があります。 アクセス トークンが有効な場合は、HTTPS の本文に次の JSON オブジェクトを含む HTTP 200 レスポンスを返します。 レスポンス:
{ "sub": "USER_UUID", "email": "EMAIL_ADDRESS", "given_name": "FIRST_NAME", "family_name": "LAST_NAME", "name": "FULL_NAME", "picture": "PROFILE_PICTURE", }
userinfo エンドポイントが HTTP 200 成功レスポンスを返すと、取得したトークンとクレームがユーザーの Google アカウントに登録されます。userinfo エンドポイント レスポンス sub
システム内でユーザーを識別する一意の ID。 email
ユーザーのメールアドレス。 given_name
省略可: ユーザーの名。 family_name
省略可: ユーザーの姓。 name
省略可: ユーザーの氏名。 picture
省略可: ユーザーのプロフィール写真。
実装の検証
You can validate your implementation by using the OAuth 2.0 Playground tool.
In the tool, do the following steps:
- Click Configuration to open the OAuth 2.0 Configuration window.
- In the OAuth flow field, select Client-side.
- In the OAuth Endpoints field, select Custom.
- Specify your OAuth 2.0 endpoint and the client ID you assigned to Google in the corresponding fields.
- 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.
- 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:
- Click the Sign-in with Google button.
- Choose the account you'd like to link.
- Enter the service ID.
- Optionally enter one or more scopes that you will request access for.
- Click Start Demo.
- When prompted, confirm that you may consent and deny the linking request.
- Confirm that you are redirected to your platform.