8.4 crypt -- Function to check Unix passwords
Keywords: lib

# 8.4 `crypt` -- Function to check Unix passwords

Availability: Unix.

This module implements an interface to the 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.

`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).

A simple example illustrating typical use:

      import crypt, getpass, pwd

      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[:2]) == cryptedpasswd
          else:
              return 1