"""Wrapper to the POSIX crypt library call and associated functionality."""

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import _crypt

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import string as _string

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from random import SystemRandom as _SystemRandom

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from collections import namedtuple as _namedtuple

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_saltchars = _string.ascii_letters + _string.digits + './'

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_sr = _SystemRandom()

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class _Method(_namedtuple('_Method', 'name ident salt_chars total_size')):

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"""Class representing a salt method per the Modular Crypt Format or the

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legacy 2-character crypt method."""

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def __repr__(self):

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return '<crypt.METHOD_{}>'.format(self.name)

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def mksalt(method=None):

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"""Generate a salt for the specified method.

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If not specified, the strongest available method will be used.

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"""

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if method is None:

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method = methods[0]

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s = '${}$'.format(method.ident) if method.ident else ''

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s += ''.join(_sr.choice(_saltchars) for char in range(method.salt_chars))

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return s

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def crypt(word, salt=None):

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"""Return a string representing the one-way hash of a password, with a salt

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prepended.

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If ``salt`` is not specified or is ``None``, the strongest

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available method will be selected and a salt generated. Otherwise,

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``salt`` may be one of the ``crypt.METHOD_*`` values, or a string as

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returned by ``crypt.mksalt()``.

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"""

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if salt is None or isinstance(salt, _Method):

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salt = mksalt(salt)

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return _crypt.crypt(word, salt)

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# available salting/crypto methods

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METHOD_CRYPT = _Method('CRYPT', None, 2, 13)

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METHOD_MD5 = _Method('MD5', '1', 8, 34)

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METHOD_SHA256 = _Method('SHA256', '5', 16, 63)

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METHOD_SHA512 = _Method('SHA512', '6', 16, 106)

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methods = []

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for _method in (METHOD_SHA512, METHOD_SHA256, METHOD_MD5, METHOD_CRYPT):

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_result = crypt('', _method)

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if _result and len(_result) == _method.total_size:

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methods.append(_method)

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del _result, _method

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