gitlab-org--gitlab-foss/doc/integration/github.md

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Use GitHub as an authentication provider (FREE SELF)

You can integrate your GitLab instance with GitHub.com and GitHub Enterprise. You can import projects from GitHub, or sign in to GitLab with your GitHub credentials.

Create an OAuth app in GitHub

To enable the GitHub OmniAuth provider, you need an OAuth 2.0 client ID and client secret from GitHub:

1. Sign in to GitHub.
2. Create an OAuth App and provide the following information:
   • The URL of your GitLab instance, such as https://gitlab.example.com.
   • The authorization callback URL, such as, https://gitlab.example.com/users/auth. Include the port number if your GitLab instance uses a non-default port.

Check for security vulnerabilities

For some integrations, the OAuth 2 covert redirect vulnerability can compromise GitLab accounts. To mitigate this vulnerability, append /users/auth to the authorization callback URL.

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

Enable GitHub OAuth in GitLab

1. Configure the initial settings in GitLab.

2. Edit the GitLab configuration file using the following information:

   GitHub setting	Value in the GitLab configuration file	Description
   Client ID	YOUR_APP_ID	OAuth 2.0 client ID
   Client secret	YOUR_APP_SECRET	OAuth 2.0 client secret
   URL	https://github.example.com/	GitHub deployment URL

   • For Omnibus installations

     1. Open the /etc/gitlab/gitlab.rb file.

        For GitHub.com, update the following section:

        gitlab_rails['omniauth_providers'] = [
          {
            name: "github",
            # label: "Provider name", # optional label for login button, defaults to "GitHub"
            app_id: "YOUR_APP_ID",
            app_secret: "YOUR_APP_SECRET",
            args: { scope: "user:email" }
          }
        ]
        

        For GitHub Enterprise, update the following section and replace https://github.example.com/ with your GitHub URL:

        gitlab_rails['omniauth_providers'] = [
          {
            name: "github",
            # label: "Provider name", # optional label for login button, defaults to "GitHub"
            app_id: "YOUR_APP_ID",
            app_secret: "YOUR_APP_SECRET",
            url: "https://github.example.com/",
            args: { scope: "user:email" }
          }
        ]
        

     2. Save the file and reconfigure GitLab.

   • For installations from source

     1. Open the config/gitlab.yml file.

        For GitHub.com, update the following section:

        - { name: 'github',
            # label: 'Provider name', # optional label for login button, defaults to "GitHub"
            app_id: 'YOUR_APP_ID',
            app_secret: 'YOUR_APP_SECRET',
            args: { scope: 'user:email' } }
        

        For GitHub Enterprise, update the following section and replace https://github.example.com/ with your GitHub URL:

        - { name: 'github',
            # label: 'Provider name', # optional label for login button, defaults to "GitHub"
            app_id: 'YOUR_APP_ID',
            app_secret: 'YOUR_APP_SECRET',
            url: "https://github.example.com/",
            args: { scope: 'user:email' } }
        

     2. Save the file and restart GitLab.

3. Refresh the GitLab sign-in page. A GitHub icon should display below the sign-in form.

4. Select the icon. Sign in to GitHub 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",
    # label: "Provider name", # optional label for login button, defaults to "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',
    # label: 'Provider name', # optional label for login button, defaults to "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. On 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.