=============================================================
:samp:`passlib.hash.ldap_{digest}` - RFC2307 Standard Digests
=============================================================

.. currentmodule:: passlib.hash

Passlib provides support for all the standard
LDAP hash formats specified by :rfc:`2307`.
This includes ``{MD5}``, ``{SMD5}``, ``{SHA}``, ``{SSHA}``.
These schemes range from somewhat to very insecure,
and should not be used except when required.

.. note::

    RFC 2307 also specifies a ``{CRYPT}`` scheme,
    which is supposed to wrap the host OS's :func:`!crypt()`.
    Being host-dependant, this scheme is somewhat different,
    and is details in :doc:`passlib.hash.ldap_crypt`.

.. seealso::

    * :doc:`passlib.hash.ldap_crypt`

    * :mod:`!passlib.apps` for a :ref:`list of premade ldap contexts <ldap-contexts>`.

Usage
=====
These classes all wrap the underlying hashlib implementations,
and are mainly useful only for plugging them into a :class:`~passlib.context.CryptContext`.
However, they can be used directly as follows::

    >>> from passlib.hash import ldap_salted_md5 as lsm

    >>> #encrypt password
    >>> h = lsm.encrypt("password")
    >>> h
    '{SMD5}OqsUXNHIhHbznxrqHoIM+ZT8DmE='

    >>> lms.identify(h) #check if hash is recognized
    True
    >>> lms.identify('JQMuyS6H.AGMo') #check if some other hash is recognized
    False

    >>> lms.verify("password", h) #verify correct password
    True
    >>> lms.verify("secret", h) #verify incorrect password
    False

Plain Hashes
============
.. warning::

    These hashes should be considered secure in any manner,
    as they are nothing but raw MD5 & SHA-1 digests,
    which are extremely vulnerable to brute-force attacks.

.. autoclass:: ldap_md5()
.. autoclass:: ldap_sha1()

Format
------

These hashes have the format :samp:`{prefix}{checksum}`.

* :samp:`{prefix}` is `{MD5}` for ldap_md5, and `{SHA}` for ldap_sha1.
* :samp:`{checksum}` is the base64 encoding
  of the raw message digest of the password,
  using the appropriate digest algorithm.

An example ldap_md5 hash (of ``password``) is ``{MD5}X03MO1qnZdYdgyfeuILPmQ==``.
An example ldap_sha1 hash (of ``password``) is ``{SHA}W6ph5Mm5Pz8GgiULbPgzG37mj9g=``.

Salted Hashes
=============
.. autoclass:: ldap_salted_md5()
.. autoclass:: ldap_salted_sha1()

These hashes have the format :samp:`{prefix}{data}`.

* :samp:`{prefix}` is `{SMD5}` for ldap_salted_md5,
  and `{SSHA}` for ldap_salted_sha1.
* :samp:`{data}` is the base64 encoding of :samp:`{checksum}{salt}`;
  and in turn :samp:`{salt}` is a multi-byte binary salt,
  and :samp:`{checksum}` is the raw digest of the
  the string :samp:`{password}{salt}`,
  using the appropriate digest algorithm.

Format
------

An example hash (of ``password``) is ``{SMD5}jNoSMNY0cybfuBWiaGlFw3Mfi/U=``.
After decoding, this results in a raw salt string ``s\x1f\x8b\xf5``,
and a raw MD5 checksum of ``\x8c\xda\x120\xd64s&\xdf\xb8\x15\xa2hiE\xc3``.

An example hash (of ``password``) is ``{SSHA}pKqkNr1tq3wtQqk+UcPyA3HnA2NsU5NJ``.
After decoding, this results in a raw salt string ``lS\x93I``,
and a raw SHA1 checksum of ``\xa4\xaa\xa46\xbdm\xab|-B\xa9>Q\xc3\xf2\x03q\xe7\x03c``.

Security Issues
---------------
The LDAP 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).

* They currently use only 32 bits of entropy in their salt,
  which is only borderline sufficient to defeat rainbow tables,
  and cannot (portably) be increased.

Plaintext
=========
.. autoclass:: ldap_plaintext()

This handler does not hash passwords at all,
rather it encoded them into UTF-8.
The only difference between this class and :class:`~passlib.hash.plaintext`
is that this class will NOT recognize any strings that use
the ``{SCHEME}HASH`` format.

Deviations
==========

* The salt size for the salted digests appears to vary between applications.
  While OpenLDAP is fixed at 4 bytes, some systems appear to use 8 or more.
  Passlib can accept and generate strings with salts between 4-16 bytes,
  though various servers may differ in what they can handle.

.. rubric:: Footnotes

.. [#pwd] The manpage for :command:`slappasswd` - `<http://gd.tuwien.ac.at/linuxcommand.org/man_pages/slappasswd8.html>`_.

.. [#rfc] The basic format for these hashes is laid out in RFC 2307 - `<http://www.ietf.org/rfc/rfc2307.txt>`_

.. [#] OpenLDAP hash documentation - `<http://www.openldap.org/doc/admin24/security.html>`_