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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.

Authentication​

There are 2 ways to configure single sign on (SSO) for GitLab:

SAML auth​

Preparation​

The following placeholders will be used:

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

Create an application in authentik and note the slug, as this will be used later. Create a SAML provider with the following parameters:

  • ACS URL: https://gitlab.company/users/auth/saml/callback
  • Audience: https://gitlab.company
  • Issuer: https://gitlab.company
  • Binding: Redirect

Under Advanced protocol settings, set a certificate for Signing Certificate.

GitLab Configuration​

Paste the following block in your /etc/gitlab/gitlab.rb file, after replacing the placeholder values from above. To get the value for idp_cert_fingerprint, navigate to the authentik Admin interface, expand the System section and select Certificates. Then, expand the selected certificate and copy the SHA1 Certificate Fingerprint.

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'
  }
]

Afterwards, either run gitlab-ctl reconfigure if you're running GitLab Omnibus, or restart the container if you're using the container.

OpenID Connect auth​

Preparation​

The following placeholders will be used:

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

Create an application in authentik and note the slug, as this will be used later. Create a OAuth2 Provider with the following parameters:

  • Client type: Confidential
  • Redirect URI/Origins: https://gitlab.company/users/auth/openid_connect/callback
  • Scopes: email, openid, profile
  • Subject mode: Based on the Users's Email
  • Include claims in id_token: True

Under Advanced protocol settings, set a certificate for Signing Certificate.

GitLab Configuration​

Paste the following block in your /etc/gitlab/gitlab.rb file, after replacing the placeholder values from above.

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_saml_user'] = true
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 args have a look at the specific GitLab docs at https://docs.gitlab.com/ee/integration/openid_connect_provider.html