"""Wrapper to the POSIX crypt library call and associated functionality.""" import sys as _sys try: import _crypt except ModuleNotFoundError: if _sys.platform == 'win32': raise ImportError("The crypt module is not supported on Windows") else: raise ImportError("The required _crypt module was not built as part of CPython") import string as _string from random import SystemRandom as _SystemRandom from collections import namedtuple as _namedtuple _saltchars = _string.ascii_letters + _string.digits + './' _sr = _SystemRandom() class _Method(_namedtuple('_Method', 'name ident salt_chars total_size')): """Class representing a salt method per the Modular Crypt Format or the legacy 2-character crypt method.""" def __repr__(self): return '<crypt.METHOD_{}>'.format(self.name) def mksalt(method=None, *, rounds=None): """Generate a salt for the specified method. If not specified, the strongest available method will be used. """ if method is None: method = methods[0] if rounds is not None and not isinstance(rounds, int): raise TypeError(f'{rounds.__class__.__name__} object cannot be ' f'interpreted as an integer') if not method.ident: # traditional s = '' else: # modular s = f'${method.ident}$' if method.ident and method.ident[0] == '2': # Blowfish variants if rounds is None: log_rounds = 12 else: log_rounds = int.bit_length(rounds-1) if rounds != 1 << log_rounds: raise ValueError('rounds must be a power of 2') if not 4 <= log_rounds <= 31: raise ValueError('rounds out of the range 2**4 to 2**31') s += f'{log_rounds:02d}$' elif method.ident in ('5', '6'): # SHA-2 if rounds is not None: if not 1000 <= rounds <= 999_999_999: raise ValueError('rounds out of the range 1000 to 999_999_999') s += f'rounds={rounds}$' elif rounds is not None: raise ValueError(f"{method} doesn't support the rounds argument") s += ''.join(_sr.choice(_saltchars) for char in range(method.salt_chars)) return s def crypt(word, salt=None): """Return a string representing the one-way hash of a password, with a salt prepended. If ``salt`` is not specified or is ``None``, the strongest available method will be selected and a salt generated. Otherwise, ``salt`` may be one of the ``crypt.METHOD_*`` values, or a string as returned by ``crypt.mksalt()``. """ if salt is None or isinstance(salt, _Method): salt = mksalt(salt) return _crypt.crypt(word, salt) # available salting/crypto methods methods = [] def _add_method(name, *args, rounds=None): method = _Method(name, *args) globals()['METHOD_' + name] = method salt = mksalt(method, rounds=rounds) result = crypt('', salt) if result and len(result) == method.total_size: methods.append(method) return True return False _add_method('SHA512', '6', 16, 106) _add_method('SHA256', '5', 16, 63) # Choose the strongest supported version of Blowfish hashing. # Early versions have flaws. Version 'a' fixes flaws of # the initial implementation, 'b' fixes flaws of 'a'. # 'y' is the same as 'b', for compatibility # with openwall crypt_blowfish. for _v in 'b', 'y', 'a', '': if _add_method('BLOWFISH', '2' + _v, 22, 59 + len(_v), rounds=1<<4): break _add_method('MD5', '1', 8, 34) _add_method('CRYPT', None, 2, 13) del _v, _add_method