1 

     2 :mod:`crypt` --- Function to check Unix passwords

     3 =================================================

     4 

     5 .. module:: crypt

     6    :platform: Unix

     7    :synopsis: The crypt() function used to check Unix passwords.

     8 .. moduleauthor:: Steven D. Majewski <sdm7g@virginia.edu>

     9 .. sectionauthor:: Steven D. Majewski <sdm7g@virginia.edu>

    10 .. sectionauthor:: Peter Funk <pf@artcom-gmbh.de>

    11 

    12 

    13 .. index::

    14    single: crypt(3)

    15    pair: cipher; DES

    16 

    17 This module implements an interface to the :manpage:`crypt(3)` routine, which is

    18 a one-way hash function based upon a modified DES algorithm; see the Unix man

    19 page for further details.  Possible uses include allowing Python scripts to

    20 accept typed passwords from the user, or attempting to crack Unix passwords with

    21 a dictionary.

    22 

    23 .. index:: single: crypt(3)

    24 

    25 Notice that the behavior of this module depends on the actual implementation  of

    26 the :manpage:`crypt(3)` routine in the running system.  Therefore, any

    27 extensions available on the current implementation will also  be available on

    28 this module.

    29 

    30 

    31 .. function:: crypt(word, salt)

    32 

    33    *word* will usually be a user's password as typed at a prompt or  in a graphical

    34    interface.  *salt* is usually a random two-character string which will be used

    35    to perturb the DES algorithm in one of 4096 ways.  The characters in *salt* must

    36    be in the set ``[./a-zA-Z0-9]``.  Returns the hashed password as a string, which

    37    will be composed of characters from the same alphabet as the salt (the first two

    38    characters represent the salt itself).

    39 

    40    .. index:: single: crypt(3)

    41 

    42    Since a few :manpage:`crypt(3)` extensions allow different values, with

    43    different sizes in the *salt*, it is recommended to use  the full crypted

    44    password as salt when checking for a password.

    45 

    46 A simple example illustrating typical use::

    47 

    48    import crypt, getpass, pwd

    49 

    50    def login():

    51        username = raw_input('Python login:')

    52        cryptedpasswd = pwd.getpwnam(username)[1]

    53        if cryptedpasswd:

    54            if cryptedpasswd == 'x' or cryptedpasswd == '*': 

    55                raise "Sorry, currently no support for shadow passwords"

    56            cleartext = getpass.getpass()

    57            return crypt.crypt(cleartext, cryptedpasswd) == cryptedpasswd

    58        else:

    59            return 1

    60