0
  "   +ˆl–Ým_JJh¥ ² ¸È®2ò˜´oÑ‚tÐ¿Î ¾    +.. highlightlang:: c


.. _abstract:

**********************
Abstract Objects Layer
**********************

The functions in this chapter interact with Python objects regardless of their
type, or with wide classes of object types (e.g. all numerical types, or all
sequence types).  When used on object types for which they do not apply, they
will raise a Python exception.

It is not possible to use these functions on objects that are not properly
initialized, such as a list object that has been created by :c:func:`PyList_New`,
but whose items have not been set to some non-\ ``NULL`` value yet.

.. toctree::

   object.rst
   number.rst
   sequence.rst
   mapping.rst
   iter.rst
   objbuffer.rst
     -ˆÒÑƒŸÐ¿Î ô    -
: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 login():
       username = raw_input('Python login:')
       cryptedpasswd = pwd.getpwnam(username)[1]
       if cryptedpasswd:
           if cryptedpasswd == 'x' or cryptedpasswd == '*':
               raise NotImplementedError(
                   "Sorry, currently no support for shadow passwords")
           cleartext = getpass.getpass()
           return crypt.crypt(cleartext, cryptedpasswd) == cryptedpasswd
       else:
           return 1

  "   /ˆl–Ãa¾”ªeJu@·pÜlJbÑ¿Òƒ ÀÏ     /Random number generation
========================

When generating random data for use in cryptographic operations, such as an
initialization vector for encryption in
:class:`~cryptography.hazmat.primitives.ciphers.modes.CBC` mode, you do not
want to use the standard :mod:`random` module APIs. This is because they do not
provide a cryptographically secure random number generator, which can result in
major security issues depending on the algorithms in use.

Therefore, it is our recommendation to `always use your operating system's
provided random number generator`_, which is available as :func:`os.urandom`.
For example, if you need 16 bytes of random data for an initialization vector,
you can obtain them with:

.. doctest::

    >>> import os
    >>> iv = os.urandom(16)

This will use ``/dev/urandom`` on UNIX platforms, and ``CryptGenRandom`` on
Windows.

If you need your random number as an integer (for example, for
:meth:`~cryptography.x509.Certifica