commit c9496cd45c295e292b5966ad022e2c305f2dbe37 Author: Isis Lovecruft isis@torproject.org Date: Wed Mar 12 00:03:18 2014 +0000

Rewrite GimpCaptchaProtectedResource to use RSA & HMAC keys for verification. --- lib/bridgedb/HTTPServer.py | 56 ++++++++++++++++++++++++++++++++++---------- 1 file changed, 43 insertions(+), 13 deletions(-)

diff --git a/lib/bridgedb/HTTPServer.py b/lib/bridgedb/HTTPServer.py index 4deac25..ff9c7f3 100644 --- a/lib/bridgedb/HTTPServer.py +++ b/lib/bridgedb/HTTPServer.py @@ -115,9 +115,10 @@ def replaceErrorPage(error, template_name=None): class CaptchaProtectedResource(twisted.web.resource.Resource): """A general resource protected by some form of CAPTCHA."""

+ isLeaf = True + def __init__(self, useForwardedHeader=False, resource=None): twisted.web.resource.Resource.__init__(self) - self.isLeaf = resource.isLeaf self.useForwardedHeader = useForwardedHeader self.resource = resource

@@ -234,9 +235,33 @@ class GimpCaptchaProtectedResource(CaptchaProtectedResource): .. _gimp-captcha: https://github.com/isislovecruft/gimp-captcha """

- def __init__(self, captchaDir='', - useForwardedHeader=False, resource=None): + def __init__(self, secretKey=None, publicKey=None, hmacKey=None, + captchaDir='', useForwardedHeader=False, resource=None): + """Protect a **resource** via this one, using a local CAPTCHA cache. + + :param str secretkey: A PKCS#1 OAEP-padded, private RSA key, used for + verifying the client's solution to the CAPTCHA. See + :func:`bridgedb.crypto.getRSAKey` and the + ``GIMP_CAPTCHA_RSA_KEYFILE`` config setting. + :param str publickey: A PKCS#1 OAEP-padded, public RSA key, used for + creating the ``captcha_challenge_field`` string to give to a + client. + :param bytes hmacKey: The master HMAC key, used for validating CAPTCHA + challenge strings in :meth:`captcha.GimpCaptcha.check`. The file + where this key is stored can be set via the + ``GIMP_CAPTCHA_HMAC_KEYFILE`` option in the config file. + :param str captchaDir: The directory where the cached CAPTCHA images + are stored. See the ``GIMP_CAPTCHA_DIR`` config setting. + :param bool useForwardedHeader: If ``True``, obtain the client's IP + address from the ``X-Forwarded-For`` HTTP header. + :type resource: :api:`twisted.web.resource.Resource` + :param resource: The resource to serve if the client successfully + passes the CAPTCHA challenge. + """ CaptchaProtectedResource.__init__(self, useForwardedHeader, resource) + self.secretKey = secretKey + self.publicKey = publicKey + self.hmacKey = hmacKey self.captchaDir = captchaDir

def checkSolution(self, request): @@ -255,12 +280,15 @@ class GimpCaptchaProtectedResource(CaptchaProtectedResource): :rtupe: bool :returns: True, if the CAPTCHA solution was valid; False otherwise. """ - challenge, response = self.extractClientSolution(request) + challenge, solution = self.extractClientSolution(request) clientIP = self.getClientIP(request) - solution = captcha.GimpCaptcha.check(challenge, response, clientIP) - logging.debug("Captcha from %r. Parameters: %r" - % (Util.logSafely(clientIP), request.args)) - return solution + clientHMACKey = crypto.getHMAC(self.hmacKey, clientIP) + valid = captcha.GimpCaptcha.check(challenge, solution, + self.secretKey, clientHMACKey) + logging.debug("%sorrect captcha from %r: %r." % ( + "C" if valid else "Inc", Util.logSafely(clientIP), solution)) + + return valid

def getCaptchaImage(self, request): """Get a random CAPTCHA image from our **captchaDir**. @@ -276,18 +304,20 @@ class GimpCaptchaProtectedResource(CaptchaProtectedResource): - ``image`` is a string holding a binary, JPEG-encoded image. - ``challenge`` is a unique string associated with the request. """ + # Create a new HMAC key, specific to requests from this client: clientIP = self.getClientIP(request) - c = captcha.GimpCaptcha(self.captchaDir, clientIP) - + clientHMACKey = crypto.getHMAC(self.hmacKey, clientIP) + capt = captcha.GimpCaptcha(self.secretKey, self.publicKey, + clientHMACKey, self.captchaDir) try: - c.get() + capt.get() except captcha.GimpCaptchaError as error: logging.error(error) except Exception as error: logging.error("Unhandled error while retrieving Gimp captcha!") - logging.error(error) + logging.exception(error)

- return (c.image, c.challenge) + return (capt.image, capt.challenge)

def render_GET(self, request): """Get a random CAPTCHA from our local cache directory and serve it to