# Twisted, the Framework of Your Internet
# Copyright (C) 2001 Matthew W. Lefkowitz
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""

Utility functions for authorization.

These are currently for challenge-response shared secret authentication.

Maintainer: U{Glyph Lefkowitz<mailto:glyph@twistedmatrix.com>}

Stability: semi-stable

"""

# System Imports
import md5
import random

from twisted.cred.error import Unauthorized

def respond(challenge, password):
    """Respond to a challenge.
    This is useful for challenge/response authentication.
    """
    m = md5.new()
    m.update(password)
    hashedPassword = m.digest()
    m = md5.new()
    m.update(hashedPassword)
    m.update(challenge)
    doubleHashedPassword = m.digest()
    return doubleHashedPassword

def challenge():
    """I return some random data.
    """
    crap = ''
    for x in range(random.randrange(15,25)):
        crap = crap + chr(random.randint(65,90))
    crap = md5.new(crap).digest()
    return crap