How do I use let’s encrypt with gitlab?

The by far best solution I was able to find for now is described in this blog post. I won’t recite everything, but the key points are:

• Use the webroot authenticator for Let’s Encrypt
• Create the folder /var/www/letsencrypt and use this directory as webroot-path for Let’s Encrypt

• Change the following config values in /etc/gitlab/gitlab.rb and run gitlab-ctl reconfigure after that:

  nginx['redirect_http_to_https'] = true
  nginx['ssl_certificate']= "/etc/letsencrypt/live/gitlab.yourdomain.com/fullchain.pem"
  nginx['ssl_certificate_key'] = "/etc/letsencrypt/live/gitlab.yourdomain.com/privkey.pem"
  nginx['custom_gitlab_server_config']="location ^~ /.well-known {\n alias /var/www/letsencrypt/.well-known;\n}\n"
  

• If you are using Mattermost which is shipped with the Omnibus package then you can additionally set these options in /etc/gitlab/gitlab.rb:

  mattermost_nginx['redirect_http_to_https'] = true
  mattermost_nginx['ssl_certificate']= "/etc/letsencrypt/live/gitlab.yourdomain.com/fullchain.pem"
  mattermost_nginx['ssl_certificate_key'] = "/etc/letsencrypt/live/gitlab.yourdomain.com/privkey.pem"
  mattermost_nginx['custom_gitlab_mattermost_server_config']="location ^~ /.well-known {\n alias /var/www/letsencrypt/.well-known;\n}\n"
  

• After requesting your first certificate remember to change the external_url to https://... and again run gitlab-ctl reconfigure

This method is very elegant since it just mounts the directory /var/www/letsencrypt/.well-known used by the Let’s Encrypt authenticator into the Gitlab web-root via a custom Nginx configuration and authentication is always possible when Gitlab is running. This means that you can automatically renew the Let’s Encrypt certificates.