Integrate your GitLab instance with GitHub

You can integrate your GitLab instance with GitHub.com and GitHub Enterprise. This integration enables users to import projects from GitHub, or sign in to your GitLab instance with their GitHub account.

Security check

Some integrations risk compromising GitLab accounts. To help mitigate this OAuth 2 covert redirect vulnerability, append /users/auth to the end of the authorization callback URL.

However, as far as we know, GitHub does not validate the subdomain part of the redirect_uri. This means that a subdomain takeover, an XSS, or an open redirect on any subdomain of your website could enable the covert redirect attack.

Enabling GitHub OAuth

To enable the GitHub OmniAuth provider, you need an OAuth 2 Client ID and Client Secret from GitHub. To get these credentials, sign into GitHub and follow their procedure for Creating an OAuth App.

When you create an OAuth 2 app in GitHub, you need the following information:

  • The URL of your GitLab instance, such as https://gitlab.example.com.
  • The authorization callback URL; in this case, https://gitlab.example.com/users/auth. Include the port number if your GitLab instance uses a non-default port.

See Initial OmniAuth Configuration for initial settings.

After you have configured the GitHub provider, you need the following information. You must substitute that information in the GitLab configuration file in these next steps.

Setting from GitHub Substitute in the GitLab configuration file Description
Client ID YOUR_APP_ID OAuth 2 Client ID
Client Secret YOUR_APP_SECRET OAuth 2 Client Secret
URL https://github.example.com/ GitHub Deployment URL

Follow these steps to incorporate the GitHub OAuth 2 app in your GitLab server:

For Omnibus installations

  1. Edit /etc/gitlab/gitlab.rb:

    For GitHub.com: 

    gitlab_rails['omniauth_providers'] = [
  {
    "name" => "github",
    "app_id" => "YOUR_APP_ID",
    "app_secret" => "YOUR_APP_SECRET",
    "args" => { "scope" => "user:email" }
  }
]

    For GitHub Enterprise: 

    gitlab_rails['omniauth_providers'] = [
  {
    "name" => "github",
    "app_id" => "YOUR_APP_ID",
    "app_secret" => "YOUR_APP_SECRET",
    "url" => "https://github.example.com/",
    "args" => { "scope" => "user:email" }
  }
]

    Replace https://github.example.com/ with your GitHub URL.

  2. Save the file and reconfigure GitLab for the changes to take effect.

For installations from source

  1. Navigate to your repository and edit config/gitlab.yml:

    For GitHub.com: 

    - { name: 'github', app_id: 'YOUR_APP_ID',
    app_secret: 'YOUR_APP_SECRET',
    args: { scope: 'user:email' } }

    For GitHub Enterprise: 

    - { name: 'github',
    app_id: 'YOUR_APP_ID',
    app_secret: 'YOUR_APP_SECRET',
    url: "https://github.example.com/",
    args: { scope: 'user:email' } }

    Replace https://github.example.com/ with your GitHub URL.

  2. Save the file and restart GitLab for the changes to take effect.

  1. Refresh the GitLab sign in page. You should now see a GitHub icon below the regular sign in form.

  2. Click the icon to begin the authentication process. GitHub asks the user to sign in and authorize the GitLab application.

GitHub Enterprise with self-signed Certificate

If you are attempting to import projects from GitHub Enterprise with a self-signed certificate and the imports are failing, you must disable SSL verification. It should be disabled by adding verify_ssl to false in the provider configuration and changing the global Git sslVerify option to false in the GitLab server.

For Omnibus package: 

gitlab_rails['omniauth_providers'] = [
  {
    "name" => "github",
    "app_id" => "YOUR_APP_ID",
    "app_secret" => "YOUR_APP_SECRET",
    "url" => "https://github.example.com/",
    "verify_ssl" => false,
    "args" => { "scope" => "user:email" }
  }
]

You must also disable Git SSL verification on the server hosting GitLab. 

omnibus_gitconfig['system'] = { "http" => ["sslVerify = false"] }

For installation from source: 

- { name: 'github',
    app_id: 'YOUR_APP_ID',
    app_secret: 'YOUR_APP_SECRET',
    url: "https://github.example.com/",
    verify_ssl: false,
    args: { scope: 'user:email' } }

You must also disable Git SSL verification on the server hosting GitLab. 

git config --global http.sslVerify false

For the changes to take effect, reconfigure GitLab if you installed via Omnibus, or restart GitLab if you installed from source.

Troubleshooting

Error 500 when trying to sign in to GitLab via GitHub Enterprise

Check the production.log on your GitLab server to obtain further details. If you are getting the error like Faraday::ConnectionFailed (execution expired) in the log, there may be a connectivity issue between your GitLab instance and GitHub Enterprise. To verify it, start the rails console and run the commands below replacing <github_url> with the URL of your GitHub Enterprise instance: 

uri = URI.parse("https://<github_url>") # replace `GitHub-URL` with the real one here
http = Net::HTTP.new(uri.host, uri.port)
http.use_ssl = true
http.verify_mode = 1
response = http.request(Net::HTTP::Get.new(uri.request_uri))

If you are getting a similar execution expired error, it confirms the theory about the network connectivity. In that case, make sure that the GitLab server is able to reach your GitHub enterprise instance.

Signing in using your GitHub account without a pre-existing GitLab account is not allowed

If you’re getting the message Signing in using your GitHub account without a pre-existing GitLab account is not allowed. Create a GitLab account first, and then connect it to your GitHub account when signing in, in GitLab:

  1. In the top-right corner, select your avatar.
  2. Select Edit profile.
  3. In the left sidebar, select Account.
  4. In the Social sign-in section, select Connect to GitHub.

After that, you should be able to sign in via GitHub successfully.