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104 lines
3.3 KiB
Python
104 lines
3.3 KiB
Python
"""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, *, rounds=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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if rounds is not None and not isinstance(rounds, int):
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raise TypeError(f'{rounds.__class__.__name__} object cannot be '
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f'interpreted as an integer')
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if not method.ident: # traditional
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s = ''
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else: # modular
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s = f'${method.ident}$'
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if method.ident and method.ident[0] == '2': # Blowfish variants
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if rounds is None:
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log_rounds = 12
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else:
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log_rounds = int.bit_length(rounds-1)
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if rounds != 1 << log_rounds:
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raise ValueError('rounds must be a power of 2')
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if not 4 <= log_rounds <= 31:
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raise ValueError('rounds out of the range 2**4 to 2**31')
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s += f'{log_rounds:02d}$'
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elif method.ident in ('5', '6'): # SHA-2
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if rounds is not None:
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if not 1000 <= rounds <= 999_999_999:
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raise ValueError('rounds out of the range 1000 to 999_999_999')
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s += f'rounds={rounds}$'
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elif rounds is not None:
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raise ValueError(f"{method} doesn't support the rounds argument")
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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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methods = []
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def _add_method(name, *args, rounds=None):
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method = _Method(name, *args)
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globals()['METHOD_' + name] = method
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salt = mksalt(method, rounds=rounds)
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result = crypt('', salt)
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if result and len(result) == method.total_size:
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methods.append(method)
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return True
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return False
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_add_method('SHA512', '6', 16, 106)
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_add_method('SHA256', '5', 16, 63)
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# Choose the strongest supported version of Blowfish hashing.
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# Early versions have flaws. Version 'a' fixes flaws of
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# the initial implementation, 'b' fixes flaws of 'a'.
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# 'y' is the same as 'b', for compatibility
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# with openwall crypt_blowfish.
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for _v in 'b', 'y', 'a', '':
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if _add_method('BLOWFISH', '2' + _v, 22, 59 + len(_v), rounds=1<<4):
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break
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_add_method('MD5', '1', 8, 34)
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_add_method('CRYPT', None, 2, 13)
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del _v, _add_method
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