Rack JWT Bastion

JWT authentication middleware for multi-tenant Rack applications.

Note: This is version 0.0.0 - a placeholder release to reserve the gem name. Implementation is in progress.

Features

• JWT token validation with configurable algorithms
• Multi-tenant support with company group validation
• Subdomain-based tenant isolation
• Company slug access control
• Configurable path exclusions for public endpoints
• Custom payload validation
• Debug mode for development

Installation

Add this line to your application's Gemfile:

gem 'rack_jwt_bastion'

And then execute:

bundle install

Or install it yourself as:

gem install rack_jwt_bastion

Quick Start

Rails Application

# config/application.rb
config.middleware.insert_before 0, RackJwtBastion::Middleware, {
  jwt_secret: ENV['JWT_SECRET'],
  company_header_name: 'X-Company-Group-Id',
  skip_paths: ['/api/v1/login', '/api/v1/refresh', '/health']
}

Sinatra Application

require 'rack_jwt_bastion'

use RackJwtBastion::Middleware, {
  jwt_secret: ENV['JWT_SECRET'],
  company_header_name: 'X-Company-Group-Id',
  skip_paths: ['/login', '/health']
}

Pure Rack Application

require 'rack_jwt_bastion'

app = Rack::Builder.new do
  use RackJwtBastion::Middleware, {
    jwt_secret: ENV['JWT_SECRET'],
    validate_subdomain: true,
    validate_company_slug: true
  }

  run YourApp.new
end

Configuration Options

Basic Configuration

RackJwtBastion::Middleware.new(app, {
  # JWT Settings (Required)
  jwt_secret: ENV['JWT_SECRET'],
  jwt_algorithm: 'HS256',  # Default: 'HS256'

  # Multi-Tenant Settings
  company_header_name: 'X-Company-Group-Id',  # Default: 'X-Company-Group-Id'
  validate_subdomain: true,     # Default: false
  validate_company_slug: true,  # Default: false

  # Path Configuration
  skip_paths: ['/health', '/api/v1/login', '/api/v1/refresh'],
  company_slug_pattern: /^\/api\/v1\/([^\/]+)\//,  # Default pattern

  # Response Customization
  unauthorized_response: { error: 'Authentication required' },
  forbidden_response: { error: 'Access denied' },

  # Debugging
  debug_mode: Rails.env.development?  # Default: false
})

Advanced Configuration

RackJwtBastion::Middleware.new(app, {
  jwt_secret: ENV['JWT_SECRET'],

  # Custom Payload Validation
  custom_payload_validator: ->(payload, request) {
    # Return true if valid, false if invalid
    payload['role'] == 'admin' || payload['permissions'].include?('read')
  },

  # Flexible Payload Mapping
  payload_mapping: {
    user_id: :sub,                    # Map 'sub' claim to user_id
    company_group_id: :company_id,    # Map 'company_id' claim
    company_group_domain: :domain,    # Map 'domain' claim
    company_slugs: :accessible_companies  # Map array of accessible companies
  },

  # Custom Tenant Extraction
  tenant_strategy: :custom,
  tenant_extractor: ->(request) {
    # Extract tenant from custom header or logic
    request.get_header('HTTP_X_TENANT_ID')
  }
})

Multi-Tenant Support

Rack JWT Bastion provides multiple strategies for multi-tenant authentication:

Subdomain Validation

# Validates that the JWT's domain matches the request subdomain
config.validate_subdomain = true

Company Slug Validation

# Validates that the requested company slug is accessible to the user
config.validate_company_slug = true
config.company_slug_pattern = /^\/api\/v1\/([^\/]+)\//

Header-Based Validation

# Validates the X-Company-Group-Id header against JWT payload
config.company_header_name = 'X-Company-Group-Id'

JWT Payload Structure

The middleware expects JWT payloads with the following structure:

{
  "user_id": 12345,
  "company_group_id": 67890,
  "company_group_domain": "acme.example.com", 
  "company_slugs": ["acme", "acme-corp"],
  "roles": ["admin", "user"],
  "exp": 1640995200,
  "iat": 1640991600
}

You can customize the payload mapping using the payload_mapping configuration option.

Security Features

• JWT signature verification
• Token expiration validation
• Company/tenant access control
• Subdomain validation
• Request path filtering for public endpoints

Performance

• Skip paths are checked before JWT processing
• Low memory footprint
• Compatible with JWT caching strategies

Error Handling

The middleware returns appropriate HTTP status codes:

• 401 Unauthorized - Missing, invalid, or expired JWT
• 403 Forbidden - Valid JWT but insufficient permissions/access

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

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

Code of Conduct

Everyone interacting in the Rack JWT Bastion project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.