devise jwtable

devise_initializer.rb

Devise.setup do |config|
  config.warden do |manager|
    manager.intercept_401 = false
    manager.default_strategies(scope: :user).unshift :jwtable
  end
end

jwtable.rb

module Devise
  module Models
    # To add jwtable to your User model add 
    # ```devise ...., :jwtablea```
    module Jwtable
      class Strategy < Devise::Strategies::Authenticatable
        JWT_REG = /^Bearer:?\s+(.*?);?$/

        def store
          false
        end

        def valid?
          request.headers['HTTP_AUTHORIZATION'].present?
        end

        def authenticate!
          match = JWT_REG.match(request.headers['HTTP_AUTHORIZATION'])

          if match.blank? || match[1].blank?
            fail!('Authorization header required')
          else
            claims, user = user_and_claims_from_token(match[1])
            env['jwt.claims'] = claims
            success! user
          end
        rescue JWT::DecodeError, JWT::ExpiredSignature, JWT::VerificationError => e
          fail!(e.message)
        end

        def user_and_claims_from_token(jwt)
          claims = JWT.decode(jwt, Rails.application.secrets.jwt_secret).first
          case claims['sub']
          when /^User:\d+/
            [claims, User.find(claims['sub'].split(':').last)]
          else
            [claims, nil]
          end
        end
      end
    end
  end
end

# for warden, `:jwtable_strategy` is just a name to identify the strategy
Warden::Strategies.add :jwtable, Devise::Models::Jwtable::Strategy
Devise.add_module :jwtable, strategy: true

user.rb

class User < ActiveRecord::Base
  devise :database_authenticatable, :jwtable
end