Integrate your server with GitLab.com

DETAILS: Tier: Free, Premium, Ultimate Offering: Self-managed

Import projects from GitLab.com and login to your GitLab instance with your GitLab.com account.

To enable the GitLab.com OmniAuth provider you must register your application with GitLab.com. GitLab.com generates an application ID and secret key for you to use.

Sign in to GitLab.com.
On the left sidebar, select your avatar.
Select Edit profile.
On the left sidebar, select Applications.
Provide the required details for Add new application.
- Name: This can be anything. Consider something like <Organization>'s GitLab or <Your Name>'s GitLab or something else descriptive.
- Redirect URI:
```
# You can also use a non-SSL URL, but you should use SSL URLs.
https://your-gitlab.example.com/import/gitlab/callback
https://your-gitlab.example.com/users/auth/gitlab/callback
```
The first link is required for the importer and second for authentication.

If you:
- Plan to use the importer, you can leave scopes as they are.
- Only want to use this application for authentication, we recommend using a more minimal set of scopes. read_user is sufficient.
Select Save application.
You should now see an Application ID and Secret. Keep this page open as you continue configuration.
On your GitLab server, open the configuration file.

For Linux package installations:
```
sudo editor /etc/gitlab/gitlab.rb
```
For self-compiled installations:
```
cd /home/git/gitlab

sudo -u git -H editor config/gitlab.yml
```
Configure the common settings to add gitlab as a single sign-on provider. This enables Just-In-Time account provisioning for users who do not have an existing GitLab account.

Add the provider configuration:

For Linux package installations authenticating against GitLab.com:

gitlab_rails['omniauth_providers'] = [
  {
    name: "gitlab",
    # label: "Provider name", # optional label for login button, defaults to "GitLab.com"
    app_id: "YOUR_APP_ID",
    app_secret: "YOUR_APP_SECRET",
    args: { scope: "read_user" } # optional: defaults to the scopes of the application
  }
]

Or, for Linux package installations authenticating against a different GitLab instance:

gitlab_rails['omniauth_providers'] = [
  {
    name: "gitlab",
    label: "Provider name", # optional label for login button, defaults to "GitLab.com"
    app_id: "YOUR_APP_ID",
    app_secret: "YOUR_APP_SECRET",
    args: { scope: "read_user", # optional: defaults to the scopes of the application
            client_options: { site: "https://gitlab.example.com" } }
  }
]

For self-compiled installations authenticating against GitLab.com:

- { name: 'gitlab',
    # label: 'Provider name', # optional label for login button, defaults to "GitLab.com"
    app_id: 'YOUR_APP_ID',
    app_secret: 'YOUR_APP_SECRET',

Or, for self-compiled installations to authenticate against a different GitLab instance:

- { name: 'gitlab',
    label: 'Provider name', # optional label for login button, defaults to "GitLab.com"
    app_id: 'YOUR_APP_ID',
    app_secret: 'YOUR_APP_SECRET',
    args: { "client_options": { "site": 'https://gitlab.example.com' } }

NOTE: In GitLab 15.1 and earlier, the site parameter requires an /api/v4 suffix. We recommend you drop this suffix after you upgrade to GitLab 15.2 or later.

Change 'YOUR_APP_ID' to the Application ID from the GitLab.com application page.
Change 'YOUR_APP_SECRET' to the secret from the GitLab.com application page.
Save the configuration file.
Implement these changes by using the appropriate method:
- For Linux package installations, reconfigure GitLab.
- For self-compiled installations, restart GitLab.

On the sign-in page, there should now be a GitLab.com icon following the regular sign-in form. Select the icon to begin the authentication process. GitLab.com asks the user to sign in and authorize the GitLab application. If everything goes well, the user is returned to your GitLab instance and is signed in.

Reduce access privileges on sign in

Introduced in GitLab 14.8 with a flag named omniauth_login_minimal_scopes. Disabled by default.

Enabled on GitLab.com in GitLab 14.9.

Feature flag omniauth_login_minimal_scopes removed in GitLab 15.2

If you use a GitLab instance for authentication, you can reduce access rights when an OAuth application is used for sign in.

Any OAuth application can advertise the purpose of the application with the authorization parameter: gl_auth_type=login. If the application is configured with api or read_api, the access token is issued with read_user for login, because no higher permissions are needed.

The GitLab OAuth client is configured to pass this parameter, but other applications can also pass it.