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Balrog logo

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Balrog is a lightweight authorization library for Ruby on Rails >= 5 written by Pixie Labs that can protect your routes. Balrog can be configured to authorize users using a simple password or single sign-on or both.

  • If you choose to protect your routes with a password, the password will be stored as a password hash, not plain text, and Balrog provides a lightweight HTML form that can be styled and used with password managers.
  • If you choose to configure Balrog to use SSO, you can whitelist multiple email domains, allowing groups of users access parts of your app, without circulating a password.
  • Balrog's authentication can and should be configured to expire, requiring users to sign-in again in accordance with OWASP best practices.
  • Balrog can also be used to restrict access to mounted Rack applications like Sidekiq.

Table of Contents


Add the gem to your Gemfile:

gem 'balrog'

Run the installer to generate an initializer:

$ bundle exec rails generate balrog:install
Enter New Password: 
Confirm New Password: 
      create  config/initializers/balrog.rb

Regenerating a password hash

If you need to create a new password, modify the hash in the Balrog initializer. You can generate a new hash with the provided Rake task:

$ bundle exec rails balrog:generate_hash
New password: *******
Type again: *******


Copy this hash into config/initializers/balrog.rb

Restricting access in a controller

class AdminController < ApplicationController
  before_action :authenticate_with_balrog!

Restricting access to mounted Rack applications within config/routes.rb

Use the .use method to add Balrog to the 'stack'.

For example with Sidekiq::Web...

# Then we tell SideKiq to use Balrog::RoutesMiddleware
Sidekiq::Web.use Balrog::RoutesMiddleware

mount Sidekiq::Web => '/sidekiq'

N.B. If you are mounting Sidekiq Web, you need to disable Sidekiq Web's session in config/initializers/sidekiq.rb.

require 'sidekiq/web'

# In order to force sidekiq to use the rails app's session,
# we need to disable the Sidekiq's session.

Logout button

To add a logout button, you can call the balrog_logout_button view helper method and pass in a hash of HTML options to style it. After logout, the user will be redirected to the root of the app.

For example, in your view:

<ul class='nav'>
  <li><%= balrog_logout_button 'Admin Logout' %></li>

Other usage examples:

<%= balrog_logout_button %>
<%= balrog_logout_button "Leave this place" %>
<%= balrog_logout_button "Click me", class: 'fancy-button--with-custom-text' %>
<%= balrog_logout_button class: 'fancy-button--with-default-text' %>

Changing session expiry length

set_session_expiry requires the user to login again after a period of time. To customise this value, open config/initializers/balrog.rb after running balrog:install and change the argument being passed to set_session_expiry.

The argument passed to set_session_expiry can be any of the Rails time extensions.

If you don't want sessions to expire, remove set_session_expiry from the initializer completely.

Balrog::Middleware.setup do |config|
  config.password_hash '$2a$12$BLz7XCFdG9YfwL64KlTgY.T3FY55aQk8SZEzHfpHfw15F2uN1kuSi'
  config.set_session_expiry 30.minutes

Configuring the Balrog gate view

We built Balrog to have a default view and stylesheet so that you can drop Balrog into your project and everything should “just work”. However, we don't want to be in your way if you needed to customise your Balrog gate view.

If you want to customise the Balrog view, you can run the balrog:view generator, which will copy the required view and layout to your application:

$ rails generate balrog:view

After running the generator, you can now add elements and classes to the views/balrog/gate.html.erb, add styles to the assets/stylesheets/application.css and import the application stylesheet in app/views/layouts/balrog.html.erb. For an example, see the dummy-rails-app in the spec folder.

Single Sign On

To add single sign on you will need to add the omniauth gem to your gem file, along with the omniauth gem for your chosen provider.

In config/initializers/balrog.rb, call config.set_omniauth in the setup block. .set_omniauth takes the same arguments as the OmniAuth::Builder#provider method, a provider and any required keys.

To whitelist any email addresses with a specific domain, call config.set_domain_whitelistin the setup block and pass in the domain. If you want to whitelist multiple domains, you can pass multiple domains to the .set_domain_whitelist.

Balrog does not require a password to be set if you wish to use single sign-on only.

Balrog::Middleware.setup do |config|
  credentials = Rails.application.credentials
  config.set_omniauth :google_oauth2, credentials.google_client_id, credentials.google_client_secret
  config.set_domain_whitelist '', ''

Please note: there is currently a CSRF vulnerability which affects OmniAuth (designated CVE-2015-9284) that requires mitigation at the application level. More details on how to do this can be found on the Omniauth Wiki.

Upgrading from 1.1 to 2.0

To upgrade, you will need to change your Balrog initializer.

  1. Instead of calling Rails.application.config.middleware.use Balrog::Middleware, you will now need to call Balrog::Middleware.setup.

  2. Change the block you pass into these methods. #password_hash and #set_session_expiry now need to called on a block parameter, e.g set_session_expiry 30.minutes needs to be changed to config.set_session_expiry 30.minutes.

See below for code examples.

# Balrog 1.1
Rails.application.config.middleware.use Balrog::Middleware do
  password_hash '$2a$12$I8Fp3e2GfSdM7KFyoMx56.BVdHeeyk9DQWKkdsxw7USvU/mC8a8.q'
  set_session_expiry 30.minutes
# Balrog 2.0
Balrog::Middleware.setup do |config|
  config.set_password_hash '$2a$12$9lquJW6mVYYS1pD1xYMGzulyC6sEDuLIUfkA/Y7F3RQ8psLNYyLeO'
  config.set_session_expiry 30.minutes


Running the tests

Tests are part of the dummy Rails app within the spec folder. To run the tests:

$ cd spec/dummy-rails-app
$ bundle
$ rails generate active_record:session_migration
$ redis-server

Then in a different terminal:

$ cd spec/dummy-rails-app
$ rspec

Before contributing, please read the code of conduct.

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet.
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it.
  • Fork the project.
  • Start a feature/bugfix branch.
  • Commit and push until you are happy with your contribution.
  • Please try not to mess with the package.json, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so we can cherry-pick around it.


  • Restricting access via routes.rb
  • Test coverage


A lightweight authorization library for Ruby on Rails that protects your routes with a simple password form.





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