Integrate with GitLab

Support level: authentik

What is GitLab

GitLab is a complete DevOps platform with features for version control, CI/CD, issue tracking, and collaboration, facilitating efficient software development and deployment workflows.

-- https://about.gitlab.com/what-is-gitlab/

info

In case something goes wrong with the configuration or you need to log in as admin, you can use the URL https://gitlab.company/users/sign_in?auto_sign_in=false to log in using the built-in authentication.

Preparation

The following placeholders are used in this guide:

• gitlab.company is the FQDN of the GitLab installation.
• authentik.company is the FQDN of the authentik installation.

note

This documentation lists only the settings that you need to change from their default values. Be aware that any changes other than those explicitly mentioned in this guide could cause issues accessing your application.

Configuration methods

There are two ways to configure single sign-on for GitLab. You can configure it via SAML authentication or via OpenID Connect.

SAML

authentik Configuration

To support the integration of GitLab with authentik, you need to create an application/provider pair in authentik.

Create an Application and Provider in authentik

1. Log in to authentik as an admin and open the authentik Admin interface.
2. Navigate to Applications > Applications and click Create with Provider.
   • Application: Provide a descriptive name, an optional group, and UI settings. Take note of the slug as it will be required later.
   • Choose a Provider type: Select SAML Provider.
   • Configure the Provider:
     • Set the ACS URL to https://gitlab.company/users/auth/saml/callback.
     • Set the Audience and Issuer to https://gitlab.company.
     • Set the Service Provider Binding to Post.
     • Under Advanced protocol settings, select an available signing certificate.
3. Click Submit to save the new application and provider.

GitLab configuration

Paste the following block in your /etc/gitlab/gitlab.rb file:

gitlab_rails['omniauth_enabled'] = true
gitlab_rails['omniauth_allow_single_sign_on'] = ['saml']
gitlab_rails['omniauth_sync_email_from_provider'] = 'saml'
gitlab_rails['omniauth_sync_profile_from_provider'] = ['saml']
gitlab_rails['omniauth_sync_profile_attributes'] = ['email']
gitlab_rails['omniauth_auto_sign_in_with_provider'] = 'saml'
gitlab_rails['omniauth_block_auto_created_users'] = false
gitlab_rails['omniauth_auto_link_saml_user'] = true
gitlab_rails['omniauth_providers'] = [
  {
    name: 'saml',
    args: {
      assertion_consumer_service_url: 'https://gitlab.company/users/auth/saml/callback',
      # Shown when navigating to certificates in authentik
      idp_cert_fingerprint: '4E:1E:CD:67:4A:67:5A:E9:6A:D0:3C:E6:DD:7A:F2:44:2E:76:00:6A',
      idp_sso_target_url: 'https://authentik.company/application/saml/<gitlab application slug>/sso/binding/redirect/',
      issuer: 'https://gitlab.company',
      name_identifier_format: 'urn:oasis:names:tc:SAML:2.0:nameid-format:persistent',
      attribute_statements: {
        email: ['http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress'],
        first_name: ['http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name'],
        nickname: ['http://schemas.goauthentik.io/2021/02/saml/username']
      }
    },
    label: 'authentik'
  }
]

Run gitlab-ctl reconfigure or restart the container after making changes.

OIDC

authentik configuration

To support the integration of GitLab with authentik, you need to create an application/provider pair in authentik.

Create an application and provider in authentik

1. Log in to authentik as an admin, and open the authentik Admin interface.
2. Navigate to Applications > Applications and click Create with Provider to create an application and provider pair. (Alternatively you can first create a provider separately, then create the application and connect it with the provider.)

• Application: provide a descriptive name, an optional group for the type of application, the policy engine mode, and optional UI settings.
• Choose a Provider type: select OAuth2/OpenID Connect as the provider type.
• Configure the Provider: provide a name (or accept the auto-provided name), the authorization flow to use for this provider, and the following required configurations.
  • Note the Client ID,Client Secret, and slug values because they will be required later.
  • Set a Strict redirect URI to https://gitlab.company/users/auth/openid_connect/callback.
  • Select any available signing key.
  • Under Advanced protocol settings, set the Subject mode to Based on the User's Email.
• Configure Bindings (optional): you can create a binding (policy, group, or user) to manage the listing and access to applications on a user's My applications page.

3. Click Submit to save the new application and provider.

GitLab configuration

Paste the following block in your /etc/gitlab/gitlab.rb file:

gitlab_rails['omniauth_allow_single_sign_on'] = ['openid_connect']
gitlab_rails['omniauth_sync_email_from_provider'] = 'openid_connect'
gitlab_rails['omniauth_sync_profile_from_provider'] = ['openid_connect']
gitlab_rails['omniauth_sync_profile_attributes'] = ['email']
gitlab_rails['omniauth_auto_sign_in_with_provider'] = 'openid_connect'
gitlab_rails['omniauth_block_auto_created_users'] = false
gitlab_rails['omniauth_auto_link_user'] = ['openid_connect']
gitlab_rails['omniauth_providers'] = [
  {
    name: 'openid_connect',
    label: 'My Company OIDC Login',
    args: {
      name: 'openid_connect',
      scope: ['openid','profile','email'],
      response_type: 'code',
      issuer: 'https://authentik.company/application/o/gitlab-slug/',
      discovery: true,
      client_auth_method: 'query',
      uid_field: 'preferred_username',
      send_scope_to_token_endpoint: 'true',
      pkce: true,
      client_options: {
        identifier: '${OIDC_CLIENT_ID}',
        secret: '${OIDC_CLIENT_SECRET}',
        redirect_uri: 'https://gitlab.company/users/auth/openid_connect/callback'
      }
    }
  }
]

For further GitLab provider arguments, check the GitLab docs.