gistfile1.rhtml

This application is only for me. Or can you tell the secret?
<form method="post" action="<%= current_action %>">
  <input id="<%= param_name%>" name="<%= param_name%>" type="password" />
  <button class="submitButton" type="submit" name="commit">Here I am!</button>
</form>  

only-for-me.rb

class OnlyForMe
  require 'erb'
  require 'tilt'

  class InvalidConfiguration < StandardError; end
  
  attr_reader :param_name
  
  # here all keys, that were authenticated are stored
  @@accepted_keys = []
  
  def initialize(app, opts = {})
    @app = app
    # list of all passwords that we accept
    @secret_phrases = opts[:secret_phrases] || ["password"] 
    raise InvalidConfiguration unless @secret_phrases.is_a?(Array)
    # name of parameter used in the authentication form
    @param_name = opts[:param_name] || 'secret_phrase'
    # name of the cookie in wich we store authentication key 
    @cookie_name = opts[:cookie_name] || 'only.for.me'
    # how long should session last?
    @expires = opts[:expires] || 1.hour
    # provide template with one form and a field.
    # template is 
    @template_path = opts[:template_path]
  end
  
  def call(env) 
    # if user is authenticated we just call the application
    return @app.call(env) if @@accepted_keys.include?(read_key(env))
    
    request = Rack::Request.new(env)
    
    if @secret_phrases.include?(request.params[@param_name])
      # When user sends request with proper secret phrase we prepare a new key for him
      new_key =  Digest::MD5.hexdigest("Only for me %s %s" % [ Time.now.to_f, rand])
      @@accepted_keys << new_key
      # and redirect him to application.
      status, headers, body = [301, {"Location" => env["REQUEST_PATH"] }, "Redirected!"]
      # with key stored in cookie
      send_with_key(new_key, body, status, headers)
    else
      #if user is not authorized, we show him authentication page
      page = Tilt.new(@template_path).render(self, :current_action => env['HTTP_PATH'])
      return [200, {"Content-Type" => "text/html"}, [page]]
    end
  end
  
  # read authentication key from cookie
  def read_key(env)
    request = Rack::Request.new(env)
    request.cookies[@cookie_name]
  end
  
  # pack authentication key into cookie and attach it to response 
  def send_with_key(data, body, status, headers)
    cookie = Hash.new
    cookie[:value] = data
    cookie[:expires] = Time.now + @expires
    response = Rack::Response.new(body, status, headers)
    response.set_cookie(@cookie_name, cookie)
    response.to_a
  end
  
end