Config warden Rails 4.0.2

warden.rb

Rails.configuration.middleware.use RailsWarden::Manager do |manager|
    manager.default_strategies :remember_token
    #manager.failure_app = LoginController
end

 # Setup Session Serialization
class Warden::SessionSerializer
  def serialize(record)
    [record.class, record.id]
  end

  def deserialize(keys)
    klass, id = keys
    klass.find(id)
  end
end

# RememberToken cookie strategy

class RememberTokenStrategy < Warden::Strategies::Base
  def valid?
    cookies[:remember_token]
  end

  def authenticate!
    u = User.find_by(remember_token: User.encrypt( cookies[:remember_token]) )

    if u
      success! u
    else
      fail! t('session.message.error')
    end
  end
end

Warden::Strategies.add(:remember_token, RememberTokenStrategy)