nonce.py

import hashlib
import datetime
import urllib

# TODO: Create a thin wrapper to use settings.SECRET_KEY


def create(secret, **kwargs):
    """Create a signed, timestamped single use nonce from the given kwargs"""
    m = hashlib.md5()
    microseconds = datetime.datetime.now().microsecond
    m.update(str(microseconds))
    # Create a safe sorted string so that kwargs do not have to be
    # unicode or even the same order.
    m.update(urllib.urlencode(sorted(kwargs.iteritems(),
                                     key=lambda (k, v): k)))
    m.update(secret)
    return "{ms}|{md5}".format(ms=microseconds, md5=m.hexdigest())


def verify(nonce, secret, expires=None, **kwargs):
    """
    Return boolean if the given nonce matches the wkargs
    and has not expired

    expires: timedelta when added to the timestamp is greaterthan now.
    """
    microseconds, md5 = nonce.split('|')
    # TODO: add expires check
    m = hashlib.md5()
    m.update(microseconds)
    m.update(urllib.urlencode(sorted(kwargs.iteritems(),
                                     key=lambda (k, v): k)))
    m.update(secret)
    return md5 == m.hexdigest()