auth_tkt.py

##########################################################################
#
# Copyright (c) 2005 Imaginary Landscape LLC and Contributors.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
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# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
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# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
##########################################################################

import time as time_mod
import md5
import cgi
import Cookie

class AuthTicket(object):

    """
    This class represents an authentication token.  You must pass in
    the shared secret, the userid, and the IP address.  Optionally you
    can include tokens (a list of strings, representing role names),
    'user_data', which is arbitrary data available for your own use in
    later scripts.  Lastly, you can override the cookie name and
    timestamp.

    Once you provide all the arguments, use .cookie_value() to
    generate the appropriate authentication ticket.  .cookie()
    generates a Cookie object, the str() of which is the complete
    cookie header to be sent.

    CGI usage::

        token = auth_ticket.AuthTicket('sharedsecret', 'username',
            os.environ['REMOTE_ADDR'], tokens=['admin'])
        print 'Status: 200 OK'
        print 'Content-type: text/html'
        print token.cookie()
        print
        ... redirect HTML ...

    Webware usage::

        token = auth_ticket.AuthTicket('sharedsecret', 'username',
            self.request().environ()['REMOTE_ADDR'], tokens=['admin'])
        self.response().setCookie('auth_tkt', token.cookie_value())

    Be careful not to do an HTTP redirect after login; use meta
    refresh or Javascript -- some browsers have bugs where cookies
    aren't saved when set on a redirect.
    """

    def __init__(self, secret, userid, ip, tokens=(), user_data='',
                 time=None, cookie_name='auth_tkt',
                 secure=False):
        self.secret = secret
        self.userid = userid
        self.ip = ip
        self.tokens = ','.join(tokens)
        self.user_data = user_data
        if time is None:
            self.time = time_mod.time()
        else:
            self.time = time
        self.cookie_name = cookie_name
        self.secure = secure

    def ipts(self):
        ip_chars = ''.join(map(chr, map(int, self.ip.split('.'))))
        t = int(self.time)
        ts = ((t & 0xff000000) >> 24,
              (t & 0xff0000) >> 16,
              (t & 0xff00) >> 8,
              t & 0xff)
        ts_chars = ''.join(map(chr, ts))
        return ip_chars + ts_chars

    def digest0(self):
        return md5.new(
            self.ipts() + self.secret
            + self.userid + '\0' + self.tokens
            + '\0' + self.user_data).hexdigest()

    def digest(self):
        return md5.new(self.digest0() + self.secret).hexdigest()

    def cookie_value(self):
        v = '%s%08x%s!' % (self.digest(), int(self.time), self.userid)
        if self.tokens:
            v += self.tokens + '!'
        v += self.user_data
        return v

    def cookie(self):
        c = Cookie.SimpleCookie()
        c[self.cookie_name] = self.cookie_value().encode('base64').strip()
        c[self.cookie_name]['path'] = '/'
        if self.secure:
            c[self.cookie_name]['secure'] = 'true'
        return c