CAPTCHA plugin for Sinatra apps

gistfile1.rb

#           NAME: recaptcha
#        VERSION: 1.0
#         AUTHOR: Peter Cooper [ http://www.rubyinside.com/ github:peterc twitter:peterc ]
#    DESCRIPTION: Sinatra plugin to provide CAPTCHA support through recaptcha.net
#  COMPATIBILITY: 0.3.2 /and/ latest rtomayko Hoboken builds!
#        LICENSE: Use for what you want, just don't claim full credit unless you make significant changes
#
#   INSTRUCTIONS: 
#                 0. Check out an extended client code example at the footer of this file
#                 1. Ensure _this_ file is lib/recaptcha.rb within your app's directory structure
#                 2. Set RECAPTCHA_PRIVATE and RECAPTCHA_PUBLIC with your Recaptcha.net-provided keys
#                 3. Require from app with require 'lib/recaptcha'
#                 4. Use show_captcha from a view to get a CAPTCHA for a form
#                 5. In response method, use:
# captcha_valid?(params[:recaptcha_challenge_field], params[:recaptcha_response_field])
#                    to determine validity of response.
#                 6. Act appropriately based on the results of step 5!


require 'net/http'

module Sinatra
  module Plugins
    module Recaptcha
      RECAPTCHA_PRIVATE = "-- fill me in --"
      RECAPTCHA_PUBLIC = "-- fill me in --"
      RECAPTCHA_URL = "http://api-verify.recaptcha.net/verify"
      
      def captcha_valid?(challenge, response, private_key = Sinatra::Plugins::Recaptcha::RECAPTCHA_PRIVATE)
        begin
          res = Net::HTTP.post_form(URI.parse(RECAPTCHA_URL), { :privatekey => private_key, :remoteip => request.env["REMOTE_ADDR"], :challenge => challenge, :response => response })
          res.body.index("true") == 0
        rescue
          false
        end
      end
      
      def show_captcha(public_key = Sinatra::Plugins::Recaptcha::RECAPTCHA_PUBLIC)
        %{<script type="text/javascript"
           src="http://api.recaptcha.net/challenge?k=#{public_key}">
        </script>
      
        <noscript>
           <iframe src="http://api.recaptcha.net/noscript?k=#{public_key}"
               height="300" width="500" frameborder="0"></iframe><br>
           <textarea name="recaptcha_challenge_field" rows="3" cols="40">
           </textarea>
           <input type="hidden" name="recaptcha_response_field" 
               value="manual_challenge">
        </noscript>}
      end
    end
  end
end

# Little hack to make it work with both Sinatra 0.3.2 and latest experimental builds
(Sinatra::Base rescue Sinatra::EventContext).send(:include, Sinatra::Plugins::Recaptcha) 



# EXTENDED CLIENT CODE EXAMPLE
#
# get '/' do
#   %{
# 	<form method="post" action="/submit">
# 		<input type="text" name="whatever" value="" />
#     #{show_captcha}
# 		<input type="submit" />
# 	</form>
#   }
# end
# 
# post '/submit' do
#   if captcha_valid?(params[:recaptcha_challenge_field], params[:recaptcha_response_field])
#     "CAPTCHA passed"
#   else
#     redirect '/'
#   end
# end