An OmniAuth strategy for implementing Sign-in with Slack using OpenID Connect.

Official documentation: https://api.slack.com/authentication/sign-in-with-slack

Sponsored by Kisko Labs.

Using Bundler:

bundle add omniauth-slack-openid

Using RubyGems:

gem install omniauth-slack-openid

gem 'omniauth-slack-openid'

Create Slack app and configure OAuth & Permissions to have the following Redirect URLs:

• https://localhost:3000/user/auth/slack_openid/callback

Copy Client ID and Client Secret to your environment (e.g. .env.local file):

SLACK_CLIENT_ID=1234567890.1234567890
SLACK_CLIENT_SECRET=1234567890abcdef1234567890abcdef

Add the following to your config/initializers/devise.rb:

  config.omniauth(
    :slack_openid,
    ENV.fetch("SLACK_CLIENT_ID"),
    ENV.fetch("SLACK_CLIENT_SECRET"),
    {
      scope: "openid,email,profile",
      redirect_uri: Rails.env.development? ? "https://localhost:3000/user/auth/slack_openid/callback" : nil,
      provider_ignores_state: Rails.env.development?
    }
  )

In order to test the callback in development, try logging in and then manually update URL to use http instead of https.

Gem has own generate_uid method that concatenates team_id and user_id, you can use it with custom parameters:

def resolve_user_session(team_id, user_id)
  uid = OmniAuth::Strategies::SlackOpenid.generate_uid(team_id, user_id)
  UserSession.find_by(uid: uid, provider: "slack-openid")
end

Bug reports and pull requests are welcome on GitHub at https://github.com/amkisko/omniauth-slack-openid.rb

rm omniauth-slack-openid-*.gem
gem build omniauth-slack-openid.gemspec
gem push omniauth-slack-openid-*.gem

The gem is available as open source under the terms of the MIT License.