==================================================================
:class:`passlib.hash.mssql2005` - MS SQL 2005 password hash
==================================================================

.. currentmodule:: passlib.hash

This class implements the hash algorithm used by Microsoft SQL Server 2005
to store it's user account passwords, replacing the slightly less secure
:class:`~passlib.hash.mssql2000` variant.

.. warning::

    This hash is not very secure, and should not be used for any purposes
    besides manipulating existing MSSQL 2005 password hashes.

.. seealso::

    :class:`~passlib.hash.mssql2000`

Usage
=====
This class can be used directly as follows (note that this class requires
a username for all encrypt/verify operations)::

    >>> from passlib.hash import mssql2005 as m25

    >>> #encrypt password using specified username
    >>> h = m25.encrypt("password")
    >>> h
    '0x01006ACDF9FF5D2E211B392EEF1175EFFE13B3A368CE2F94038B'

    >>> m25.identify(h) #check if hash is recognized
    True
    >>> m25.identify('$1$3azHgidD$SrJPt7B.9rekpmwJwtON31') #check if some other hash is recognized
    False

    >>> m25.verify("password", h) #verify correct password
    True
    >>> m25.verify("letmein", h) #verify incorrect password
    False

Interface
=========
.. autoclass:: mssql2005()

.. rst-class:: html-toggle

Format & Algorithm
==================
MSSQL 2005 hashes are usually presented as a series of 52 upper-case
hexidecimal characters, prefixed by ``0x``. An example MSSQL 2005 hash
(of ``"password"``)::

    0x01006ACDF9FF5D2E211B392EEF1175EFFE13B3A368CE2F94038B

This encodes 26 bytes of raw data, consisting of:

* a 2-byte constant ``0100``
* 4 byte of salt (``6ACDF9FF`` in the example)
* 20 byte digest (``5D2E211B392EEF1175EFFE13B3A368CE2F94038B``
  in the example).

The digest is generated by encoding the unicode password using
``UTF-16-LE``, and calculating ``SHA1(encoded_secret + salt)``.

This format and algorithm is identical to :doc:`mssql2000 <passlib.hash.mssql2000>`,
except that this hash omits the 2nd case-insensitive
digest used by MSSQL 2000.

.. note::

    MSSQL 2005 hashes do not actually have a native textual format, as they
    are stored as raw bytes in an SQL table. However, when external programs
    deal with them, MSSQL generally encodes raw bytes as upper-case hexidecimal,
    prefixed with ``0x``. This is the representation Passlib uses.

Security Issues
===============
This algorithm is reasonably weak, and shouldn't be used for any
purpose besides manipulating existing MSSQL 2005 hashes. This mainly due to
it's simplicity, and years of research on high-speed SHA1
implementations, which makes efficient brute force attacks feasible.

.. rubric:: Footnotes

.. [#] Overview hash algorithms used by MSSQL -
   `<https://blogs.msdn.com/b/lcris/archive/2007/04/30/sql-server-2005-about-login-password-hashes.aspx?Redirected=true>`_.

.. [#] Description of MSSQL 2000/2005 algorithm -
   `<http://www.theregister.co.uk/2002/07/08/cracking_ms_sql_server_passwords/>`_.