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#!/usr/bin/env python

# Copyright (C) 2011 GRNET S.A. 

#

# 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 2 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, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Generate a hash from a given password

This program takes a password as an argument and

returns to standard output a hash followed by a newline.

To do this, it generates a random salt internally.

"""

import sys

import crypt 

from string import ascii_letters, digits

from random import choice

from os.path import basename

from optparse import OptionParser

# This dictionary maps the hashing algorithm method

# with its <ID> as documented in:

# http://www.akkadia.org/drepper/SHA-crypt.txt

HASH_ID_FROM_METHOD = {

    'md5': '1',

    'blowfish': '2a',

    'sun-md5': 'md5',

    'sha256': '5',

    'sha512': '6'

}

def random_salt(length=8):

    pool = ascii_letters + digits + "/" + "."

    return ''.join(choice(pool) for i in range(length))

def parse_arguments(input_args):

    usage = "usage: %prog [-h] [-m encrypt-method] <password>"

    parser = OptionParser(usage=usage)

    parser.add_option("-m", "--encrypt-method",

                        dest="encrypt_method",

                        type='choice',

                        default="sha512",

                        choices=HASH_ID_FROM_METHOD.keys(),

                        help="encrypt password with ENCRYPT_METHOD [%default] \

                        (supported: " + ", ".join(HASH_ID_FROM_METHOD.keys()) +")",

    )

    (opts, args) = parser.parse_args(input_args)

    if len(args) != 1:

        parser.error('password is missing')

    return (args[0], opts.encrypt_method)

def main():

    (password, method) = parse_arguments(sys.argv[1:])

    salt = random_salt()

    hash = crypt.crypt(password, "$"+HASH_ID_FROM_METHOD[method]+"$"+salt)

    sys.stdout.write("%s\n" % (hash))

    return 0

if __name__ == "__main__":

        sys.exit(main())

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