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.. index:: Django; hash formats
=============================================================
:samp:`passlib.hash.django_{digest}` - Django-specific Hashes
=============================================================
.. currentmodule:: passlib.hash
The `Django <http://www.djangoproject.com>`_ web framework
provides a module for storing user accounts and passwords
(:mod:`!django.contrib.auth`).
This module's password hashing code supports a few simple salted digests,
stored using the format :samp:`{id}${salt}${checksum}` (where :samp:`{id}`
is an identifier assigned by Django).
Passlib provides support for all the hashes used up to and including
Django 1.4
.. seealso::
* :ref:`passlib.apps.django_context <django-contexts>` -
a set of premade contexts which mimic Django's builtin hashing policy,
and can read all of the formats listed below.
..
* :mod:`passlib.ext.django` - a plugin that
updates Django to use a stronger hashing scheme,
and migrates existing hashes as users log in.
.. _django-1.4-hashes:
Django 1.4 Hashes
=================
Django 1.4 introduced a new "hashers" framework, as well as
three new modern large-salt variable-cost hash algorithms:
* :class:`django_pbkdf2_sha256` - a PBKDF2-HMAC-SHA256 based hash.
* :class:`django_pbkdf2_sha1` - a PBKDF2-HMAC-SHA1 based hash.
* :class:`django_bcrypt` - a wrapper around :class:`~passlib.hash.bcrypt`.
These classes can be used directly as follows::
>>> from passlib.hash import django_pbkdf2_sha256 as handler
>>> # encrypt password
>>> h = handler.encrypt("password")
>>> h
'pbkdf2_sha256$10000$s1w0UXDd00XB$+4ORmyvVWAQvoAEWlDgN34vlaJx1ZTZpa1pCSRey2Yk='
>>> # verify password
>>> handler.verify("password", h)
True
>>> handler.verify("eville", h)
False
.. seealso:: the generic :ref:`PasswordHash usage examples <password-hash-examples>`
Interface
---------
.. autoclass:: django_pbkdf2_sha256()
.. autoclass:: django_pbkdf2_sha1()
.. data:: django_bcrypt()
This class implements Django 1.4's BCrypt wrapper, and follows the :ref:`password-hash-api`.
This is identical to :class:`!bcrypt` itself, but with
the Django-specific prefix ``"bcrypt$"`` prepended.
See :doc:`/lib/passlib.hash.bcrypt` for more details,
the usage and behavior is identical.
This should be compatible with the hashes generated by
Django 1.4's :class:`!BCryptPasswordHasher` class.
.. versionadded:: 1.6
Format
------
An example :class:`!django_pbkdf2_sha256` hash (of ``password``) is:
``pbkdf2_sha256$10000$s1w0UXDd00XB$+4ORmyvVWAQvoAEWlDgN34vlaJx1ZTZpa1pCSRey2Yk=``
Both of Django's PBKDF2 hashes have the same basic format,
:samp:`{ident}${rounds}${salt}${checksum}`, where:
* :samp:`{ident}` is an identifier (``pbkdf2_sha256`` in the case of the example).
* :samp:`{rounds}` is a variable cost parameter encoded in decimal.
* :samp:`{salt}` consists of (usually 12) alphanumeric digits
(``s1w0UXDd00XB`` in the example).
* :samp:`{checksum}` is the base64 encoding the PBKDF2 digest.
The digest porition is generated by passing the ``utf-8`` encoded password,
the ``ascii``-encoded salt string, and the number of rounds into
PBKDF2 using the HMAC-SHA256 prf; and generated a 32 byte checksum,
which is then encoding using base64.
The other PBKDF2 wrapper functions similarly.
Django 1.0 Hashes
=================
.. warning::
All of the following hashes are very susceptible to brute-force attacks;
since they are simple single-round salted digests.
They should not be used for any purpose
besides manipulating existing Django password hashes.
Django 1.0 supports some basic salted digests, as well as some
legacy hashes:
* :class:`django_salted_sha1` - simple salted SHA1 digest, Django 1.0-1.3's default.
* :class:`django_salted_md5` - simple salted MD5 digest.
* :class:`django_des_crypt` - support for legacy :class:`des_crypt` hashes,
shoehorned into Django's hash format.
These classes can be used directly as follows::
>>> from passlib.hash import django_salted_sha1 as handler
>>> # encrypt password
>>> h = handler.encrypt("password")
>>> h
'sha1$c6218$161d1ac8ab38979c5a31cbaba4a67378e7e60845'
>>> # verify password
>>> handler.verify("password", h)
True
>>> handler.verify("eville", h)
False
.. seealso:: the generic :ref:`PasswordHash usage examples <password-hash-examples>`
Interface
---------
.. autoclass:: django_salted_md5()
.. autoclass:: django_salted_sha1()
Format
------
An example :class:`!django_salted_sha1` hash (of ``password``) is:
``sha1$f8793$c4cd18eb02375a037885706d414d68d521ca18c7``
Both of Django's salted hashes have the same basic format,
:samp:`{ident}${salt}${checksum}`, where:
* :samp:`{ident}` is an identifier (``sha1`` in the case of the example,
``md5`` for :class:`!django_salted_md5`).
* :samp:`{salt}` consists of (usually 5) lowercase hexidecimal digits (``f8793`` in the example).
* :samp:`{checksum}` is lowercase hexidecimal encoding of the checksum.
The checksum is generated by concatenating the salt digits followed
by the password, and hashing them using the specified digest (MD5 or SHA-1).
The digest is then encoded to hexidecimal.
If the password is unicode, it is converted to ``utf-8`` first.
Security Issues
---------------
Django's salted hashes should not be considered very secure.
* They use only a single round of digests with known collision
and pre-image attacks (SHA1 & MD5).
* While it could be increased, they currently use only 20 bits
of entropy in their salt, which is borderline insufficient to defeat
rainbow tables.
* They digest the encoded hexidecimal salt, not the raw bytes,
increasing the odds that a particular salt+password string
will be present in a pre-computed tables of ascii digests.
Des Crypt Wrapper
=================
.. autoclass:: django_des_crypt()
Format
------
An example :class:`!django_des_crypt` hash (of ``password``) is
``crypt$cd1a4$cdlRbNJGImptk``; the general format is the same
as the salted hashes: :samp:`{ident}${salt}${checksum}`, where:
* :samp:`{ident}` is the identifier ``crypt``.
* :samp:`{salt}` is 5 lowercase hexidecimal digits (``cd1a4`` in the example).
* :samp:`{checksum}` is a :class:`!des_crypt` hash (``cdlRbNJGImptk`` in the example).
It should be noted that this class essentially just shoe-horns
:class:`des_crypt` into a format compatible with the Django salted hashes (above).
It has a few quirks, such as the fact that only the first two characters
of the salt are used by :class:`!des_crypt`, and they are in turn
duplicated as the first two characters of the checksum.
For security issues relating to :class:`!django_des_crypt`,
see :class:`des_crypt`.
Other Hashes
============
.. autoclass:: django_disabled()
.. note::
Some older (pre-1.0) versions of Django encoded
passwords using :class:`~passlib.hash.hex_md5`,
though this has been deprecated by Django,
and should become increasingly rare.
|
