debian-mirror-gitlab/doc/integration/oauth_provider.md

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# GitLab as OAuth2 authentication service provider

This document describes how you can use GitLab as an OAuth 2
authentication service provider.

If you want to use:

- The [OAuth2](https://oauth.net/2/) protocol to access GitLab resources on user's behalf,
  see [OAuth2 provider](../api/oauth2.md).
- Other OAuth 2 authentication service providers to sign in to
  GitLab, see the [OAuth2 client documentation](omniauth.md).
- The related API, see [Applications API](../api/applications.md).

## Introduction to OAuth

[OAuth 2](https://oauth.net/2/) provides to client applications a 'secure delegated
access' to server resources on behalf of a resource owner. OAuth 2 allows
authorization servers to issue access tokens to third-party clients with the approval
of the resource owner or the end-user.

OAuth 2 can be used:

- To allow users to sign in to your application with their GitLab.com account.
- To set up GitLab.com for authentication to your GitLab instance.
(see [GitLab OmniAuth](gitlab.md)).

The 'GitLab Importer' feature also uses OAuth 2 to give access
to repositories without sharing user credentials to your GitLab.com account.

GitLab supports two ways of adding a new OAuth 2 application to an instance:

- As a regular user, for applications owned by an individual.
- Through the Admin Area menu for instance-wide apps.

The only difference between these two methods is the [permission](../user/permissions.md)
levels. The default callback URL is `http://your-gitlab.example.com/users/auth/gitlab/callback`.

## Add an application through the profile

To add a new application via your profile:

1. In the top-right corner, select your avatar.
1. Select **Edit profile**.
1. In the left sidebar, select **Applications**.
1. Enter a **Name**, **Redirect URI** and OAuth 2 scopes as defined in [Authorized Applications](#authorized-applications).
   The **Redirect URI** is the URL where users are sent after they authorize with GitLab.
1. Select **Save application**. GitLab displays:

   - Application ID: OAuth 2 Client ID.
   - Secret: OAuth 2 Client Secret.

## OAuth applications in the Admin Area

To create an application for your GitLab instance, select
**Admin Area > Applications > New application**.

When creating an **Admin Area** application, you can mark it as _trusted_.
The user authorization step is automatically skipped for this application.

## Authorized applications

Every application you authorize with your GitLab credentials is shown
in the **Authorized applications** section under **Settings > Applications**.

The GitLab OAuth 2 applications support scopes, which allow various actions that any given
application can perform. Available scopes are depicted in the following table.

| Scope              | Description |
| ------------------ | ----------- |
| `api`              | Grants complete read/write access to the API, including all groups and projects, the container registry, and the package registry. |
| `read_user`        | Grants read-only access to the authenticated user's profile through the /user API endpoint, which includes username, public email, and full name. Also grants access to read-only API endpoints under /users. |
| `read_api`         |  Grants read access to the API, including all groups and projects, the container registry, and the package registry. |
| `read_repository`  |  Grants read-only access to repositories on private projects using Git-over-HTTP or the Repository Files API. |
| `write_repository` | Grants read-write access to repositories on private projects using Git-over-HTTP (not using the API). |
| `read_registry`    |  Grants read-only access to container registry images on private projects. |
| `write_registry`   | Grants read-only access to container registry images on private projects. |
| `sudo`             | Grants permission to perform API actions as any user in the system, when authenticated as an administrator user. |
| `openid`           | Grants permission to authenticate with GitLab using [OpenID Connect](openid_connect_provider.md). Also gives read-only access to the user's profile and group memberships. |
| `profile`          |  Grants read-only access to the user's profile data using [OpenID Connect](openid_connect_provider.md). |
| `email`            |  Grants read-only access to the user's primary email address using [OpenID Connect](openid_connect_provider.md). |

At any time you can revoke any access by clicking **Revoke**.