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:mod:`crypt` --- Function to check Unix passwords
=================================================
.. module:: crypt
:platform: Unix
:synopsis: The crypt() function used to check Unix passwords.
.. moduleauthor:: Steven D. Majewski <sdm7g@virginia.edu>
.. sectionauthor:: Steven D. Majewski <sdm7g@virginia.edu>
.. sectionauthor:: Peter Funk <pf@artcom-gmbh.de>
.. index::
single: crypt(3)
pair: cipher; DES
This module implements an interface to the :manpage:`crypt(3)` routine, which is
a one-way hash function based upon a modified DES algorithm; see the Unix man
page for further details. Possible uses include allowing Python scripts to
accept typed passwords from the user, or attempting to crack Unix passwords with
a dictionary.
.. index:: single: crypt(3)
Notice that the behavior of this module depends on the actual implementation of
the :manpage:`crypt(3)` routine in the running system. Therefore, any
extensions available on the current implementation will also be available on
this module.
.. function:: crypt(word, salt)
*word* will usually be a user's password as typed at a prompt or in a graphical
interface. *salt* is usually a random two-character string which will be used
to perturb the DES algorithm in one of 4096 ways. The characters in *salt* must
be in the set ``[./a-zA-Z0-9]``. Returns the hashed password as a string, which
will be composed of characters from the same alphabet as the salt (the first two
characters represent the salt itself).
.. index:: single: crypt(3)
Since a few :manpage:`crypt(3)` extensions allow different values, with
different sizes in the *salt*, it is recommended to use the full crypted
password as salt when checking for a password.
A simple example illustrating typical use::
import crypt, getpass, pwd
def raw_input(prompt):
import sys
sys.stdout.write(prompt)
sys.stdout.flush()
return sys.stdin.readline()
def login():
username = raw_input('Python login:')
cryptedpasswd = pwd.getpwnam(username)[1]
if cryptedpasswd:
if cryptedpasswd == 'x' or cryptedpasswd == '*':
raise "Sorry, currently no support for shadow passwords"
cleartext = getpass.getpass()
return crypt.crypt(cleartext, cryptedpasswd) == cryptedpasswd
else:
return 1
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