captcha.py

import urllib
from google.appengine.api import urlfetch

"""
    Adapted from http://pypi.python.org/pypi/recaptcha-client
    to use with Google App Engine
    by Joscha Feth <joscha@feth.com>
    Version 0.1
"""

API_SSL_SERVER  ="https://api-secure.recaptcha.net"
API_SERVER      ="http://api.recaptcha.net"
VERIFY_SERVER   ="api-verify.recaptcha.net"

class RecaptchaResponse(object):
    def __init__(self, is_valid, error_code=None):
        self.is_valid   = is_valid
        self.error_code = error_code

def displayhtml (public_key,
                 use_ssl = False,
                 error = None):
    """Gets the HTML to display for reCAPTCHA

    public_key -- The public api key
    use_ssl -- Should the request be sent over ssl?
    error -- An error message to display (from RecaptchaResponse.error_code)"""

    error_param = ''
    if error:
        error_param = '&error=%s' % error

    if use_ssl:
        server = API_SSL_SERVER
    else:
        server = API_SERVER

    return """<script type="text/javascript" src="%(ApiServer)s/challenge?k=%(PublicKey)s%(ErrorParam)s"></script>

<noscript>
  <iframe src="%(ApiServer)s/noscript?k=%(PublicKey)s%(ErrorParam)s" 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>
""" % {
        'ApiServer' : server,
        'PublicKey' : public_key,
        'ErrorParam' : error_param,
        }


def submit (recaptcha_challenge_field,
            recaptcha_response_field,
            private_key,
            remoteip):
    """
    Submits a reCAPTCHA request for verification. Returns RecaptchaResponse
    for the request

    recaptcha_challenge_field -- The value of recaptcha_challenge_field from the form
    recaptcha_response_field -- The value of recaptcha_response_field from the form
    private_key -- your reCAPTCHA private key
    remoteip -- the user's ip address
    """

    if not (recaptcha_response_field and recaptcha_challenge_field and
            len (recaptcha_response_field) and len (recaptcha_challenge_field)):
        return RecaptchaResponse (is_valid = False, error_code = 'incorrect-captcha-sol')
    
    headers = {
               'Content-type':  'application/x-www-form-urlencoded',
               "User-agent"  :  "reCAPTCHA GAE Python"
               }         
    
    params = urllib.urlencode ({
	    'privatekey': private_key,
        'remoteip' : remoteip,
	    'challenge': recaptcha_challenge_field,
	    'response' : recaptcha_response_field,
	    })

    httpresp = urlfetch.fetch(
                   url      = "http://%s/verify" % VERIFY_SERVER,
                   payload  = params,
                   method   = urlfetch.POST,
                   headers  = headers
                    )     
    
    if httpresp.status_code == 200:
        # response was fine
        
        # get the return values
        return_values = httpresp.content.splitlines();
        
        # get the return code (true/false)
        return_code = return_values[0]
        
        if return_code == "true":
            # yep, filled perfectly
            return RecaptchaResponse (is_valid=True)
        else:
            # nope, something went wrong
            return RecaptchaResponse (is_valid=False, error_code = return_values [1])
    else:
        # recaptcha server was not reachable
        return RecaptchaResponse (is_valid=False, error_code = "recaptcha-not-reachable")