77 lines
3.3 KiB
Markdown
77 lines
3.3 KiB
Markdown
# GitLab as OAuth2 authentication service provider
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This document is about using GitLab as an OAuth authentication service provider
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to sign in to other services.
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If you want to use:
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- The [OAuth2](https://oauth.net/2/) protocol to access GitLab resources on user's behalf,
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see [OAuth2 provider](../api/oauth2.md)
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- Other OAuth authentication service providers to sign in to
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GitLab, see the [OAuth2 client documentation](omniauth.md).
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- The related API, see [Applications API](../api/applications.md).
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## Introduction to OAuth
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[OAuth](https://oauth.net/2/) provides to client applications a 'secure delegated access' to server
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resources on behalf of a resource owner. In fact, OAuth allows an authorization
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server to issue access tokens to third-party clients with the approval of the
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resource owner, or the end-user.
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OAuth is mostly used as a Single Sign-On service (SSO), but you can find a
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lot of different uses for this functionality. For example, you can allow users
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to sign in to your application with their GitLab.com account, or GitLab.com
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can be used for authentication to your GitLab instance
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(see [GitLab OmniAuth](gitlab.md)).
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The 'GitLab Importer' feature is also using the OAuth protocol to give access
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to repositories without sharing user credentials to your GitLab.com account.
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GitLab supports two ways of adding a new OAuth2 application to an instance. You
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can either add an application as a regular user or add it in the Admin Area.
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What this means is that GitLab can actually have instance-wide and a user-wide
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applications. There is no difference between them except for the different
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permission levels they are set (user/admin). The default callback URL is
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`http://your-gitlab.example.com/users/auth/gitlab/callback`
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## Adding an application through the profile
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In order to add a new application via your profile, navigate to
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**Profile Settings > Applications** and select **New Application**.
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In the application form, enter a **Name** (arbitrary), and make sure to set up
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correctly the **Redirect URI** which is the URL where users will be sent after
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they authorize with GitLab.
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When you hit **Submit** you will be provided with the application ID and
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the application secret which you can then use with your application that
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connects to GitLab.
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## OAuth applications in the Admin Area
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To create an application that does not belong to a certain user, you can create
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it from the Admin Area.
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You're also able to mark an application as _trusted_ when creating it through the Admin Area. By doing that,
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the user authorization step is automatically skipped for this application.
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## Authorized applications
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Every application you authorized to use your GitLab credentials will be shown
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in the **Authorized applications** section under **Profile Settings > Applications**.
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GitLab's OAuth applications support scopes, which allow various actions that any given
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application can perform such as `read_user` and `api`. There are many more scopes
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available.
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At any time you can revoke any access by just clicking **Revoke**.
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