gistfile1.rb

use Rack::Session::Cookie
use Rack::OpenID
use RailsWarden::Manager do |manager|
  manager.default_strategies :openid
  manager.failure_app = ExceptionsController
end

class OpenIDStrategy < Warden::Strategies::Base
  def authenticate!
    if resp = request.env['rack.openid.response']
      if resp.status == :failure || resp.status == :missing
        fail! "OpenID authentication failed"
      elsif resp.status == :cancel
        fail! "OpenID authentication canceled"
      elsif resp.status == :success
        if user = User.first(:identity_url => resp.identity_url)
          success! user
        else
          fail! "No user with given OpenID"
        end
      end
    elsif openid_url = request.params[:openid_url]
      custom!([401, { "WWW-Authenticate" => Rack::OpenID.build_header(:identifier => openid_url) }, []])
    end
  end
end
Warden::Strategies.add(:openid, OpenIDStrategy)

class UsersController
  def login
    request.env["warden"].authenticate!
    redirect_to "/dashboard"
  end
end