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GitLab Authentication Provider

The Backstage core-plugin-api package comes with a GitLab authentication provider that can authenticate users using GitLab OAuth.

Create an OAuth App on GitLab​

To support GitLab authentication, you must create an Application from the GitLab settings. The Redirect URI should point to your Backstage backend auth handler.

  1. Set Application Name to backstage-dev or something along those lines.
  2. The Authorization Callback URL should match the redirect URI set in Backstage.
    1. Set this to http://localhost:7007/api/auth/gitlab/handler/frame for local development.
    2. Set this to http://{APP_FQDN}:{APP_BACKEND_PORT}/api/auth/gitlab/handler/frame for non-local deployments.
    3. Select the following scopes from the list:
      • api Grants full read-write access to the api. This is only required if users need to be able to create merge requests with their own permissions.
      • 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_repository Grants read-only access to repositories on private projects using Git-over-HTTP (not using the API).
      • write_repository Grants read-write access to repositories on private projects using Git-over-HTTP (not using the API).
      • openid Grants permission to authenticate with GitLab using OpenID Connect. 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.
      • email Grants read-only access to the user's primary email address using OpenID Connect.

Configuration​

The provider configuration can then be added to your app-config.yaml under the root auth configuration:

auth:
  environment: development
  providers:
    gitlab:
      development:
        clientId: ${AUTH_GITLAB_CLIENT_ID}
        clientSecret: ${AUTH_GITLAB_CLIENT_SECRET}
        ## uncomment if using self-hosted GitLab
        # audience: https://gitlab.company.com
        ## uncomment if using a custom redirect URI
        # callbackUrl: https://${BASE_URL}/api/auth/gitlab/handler/frame
        signIn:
          resolvers:
            # See https://backstage.io/docs/auth/gitlab/provider#resolvers for more resolvers
            - resolver: usernameMatchingUserEntityName

The GitLab provider is a structure with three configuration keys:

  • clientId: The Application ID that you generated on GitLab, e.g. 4928c033ab3d592845c044a653bc20583baf84f2e67b954c6fdb32a532ab76c9
  • clientSecret: The Application secret
  • audience (optional): The base URL for the self-hosted GitLab instance, e.g. https://gitlab.company.com
  • callbackUrl (optional): The URL matching the Redirect URI registered when creating your GitLab OAuth App, e.g. https://$backstage.acme.corp/api/auth/gitlab/handler/frame Note: Due to a peculiarity with GitLab OAuth, ensure there is no trailing / after 'frame' in the URL.

Resolvers​

This provider includes several resolvers out of the box that you can use:

  • emailMatchingUserEntityProfileEmail: Matches the email address from the auth provider with the User entity that has a matching spec.profile.email. If no match is found it will throw a NotFoundError.
  • emailLocalPartMatchingUserEntityName: Matches the local part of the email address from the auth provider with the User entity that has a matching name. If no match is found it will throw a NotFoundError.
  • usernameMatchingUserEntityName: Matches the username from the auth provider with the User entity that has a matching name. If no match is found it will throw a NotFoundError.
Note

The resolvers will be tried in order, but will only be skipped if they throw a NotFoundError.

If these resolvers do not fit your needs you can build a custom resolver, this is covered in the Building Custom Resolvers section of the Sign-in Identities and Resolvers documentation.

Backend Installation​

To add the provider to the backend we will first need to install the package by running this command:

from your Backstage root directory
yarn --cwd packages/backend add @backstage/plugin-auth-backend-module-gitlab-provider

Then we will need to add this line:

in packages/backend/src/index.ts
backend.add(import('@backstage/plugin-auth-backend'));
backend.add(import('@backstage/plugin-auth-backend-module-gitlab-provider'));

Adding the provider to the Backstage frontend​

To add the provider to the frontend, add the gitlabAuthApi reference and SignInPage component as shown in Adding the provider to the sign-in page.