1"""Wrapper to the POSIX crypt library call and associated functionality.""" 2 3import sys as _sys 4 5try: 6 import _crypt 7except ModuleNotFoundError: 8 if _sys.platform == 'win32': 9 raise ImportError("The crypt module is not supported on Windows") 10 else: 11 raise ImportError("The required _crypt module was not built as part of CPython") 12 13import string as _string 14from random import SystemRandom as _SystemRandom 15from collections import namedtuple as _namedtuple 16 17 18_saltchars = _string.ascii_letters + _string.digits + './' 19_sr = _SystemRandom() 20 21 22class _Method(_namedtuple('_Method', 'name ident salt_chars total_size')): 23 24 """Class representing a salt method per the Modular Crypt Format or the 25 legacy 2-character crypt method.""" 26 27 def __repr__(self): 28 return '<crypt.METHOD_{}>'.format(self.name) 29 30 31def mksalt(method=None, *, rounds=None): 32 """Generate a salt for the specified method. 33 34 If not specified, the strongest available method will be used. 35 36 """ 37 if method is None: 38 method = methods[0] 39 if rounds is not None and not isinstance(rounds, int): 40 raise TypeError(f'{rounds.__class__.__name__} object cannot be ' 41 f'interpreted as an integer') 42 if not method.ident: # traditional 43 s = '' 44 else: # modular 45 s = f'${method.ident}$' 46 47 if method.ident and method.ident[0] == '2': # Blowfish variants 48 if rounds is None: 49 log_rounds = 12 50 else: 51 log_rounds = int.bit_length(rounds-1) 52 if rounds != 1 << log_rounds: 53 raise ValueError('rounds must be a power of 2') 54 if not 4 <= log_rounds <= 31: 55 raise ValueError('rounds out of the range 2**4 to 2**31') 56 s += f'{log_rounds:02d}$' 57 elif method.ident in ('5', '6'): # SHA-2 58 if rounds is not None: 59 if not 1000 <= rounds <= 999_999_999: 60 raise ValueError('rounds out of the range 1000 to 999_999_999') 61 s += f'rounds={rounds}$' 62 elif rounds is not None: 63 raise ValueError(f"{method} doesn't support the rounds argument") 64 65 s += ''.join(_sr.choice(_saltchars) for char in range(method.salt_chars)) 66 return s 67 68 69def crypt(word, salt=None): 70 """Return a string representing the one-way hash of a password, with a salt 71 prepended. 72 73 If ``salt`` is not specified or is ``None``, the strongest 74 available method will be selected and a salt generated. Otherwise, 75 ``salt`` may be one of the ``crypt.METHOD_*`` values, or a string as 76 returned by ``crypt.mksalt()``. 77 78 """ 79 if salt is None or isinstance(salt, _Method): 80 salt = mksalt(salt) 81 return _crypt.crypt(word, salt) 82 83 84# available salting/crypto methods 85methods = [] 86 87def _add_method(name, *args, rounds=None): 88 method = _Method(name, *args) 89 globals()['METHOD_' + name] = method 90 salt = mksalt(method, rounds=rounds) 91 result = crypt('', salt) 92 if result and len(result) == method.total_size: 93 methods.append(method) 94 return True 95 return False 96 97_add_method('SHA512', '6', 16, 106) 98_add_method('SHA256', '5', 16, 63) 99 100# Choose the strongest supported version of Blowfish hashing. 101# Early versions have flaws. Version 'a' fixes flaws of 102# the initial implementation, 'b' fixes flaws of 'a'. 103# 'y' is the same as 'b', for compatibility 104# with openwall crypt_blowfish. 105for _v in 'b', 'y', 'a', '': 106 if _add_method('BLOWFISH', '2' + _v, 22, 59 + len(_v), rounds=1<<4): 107 break 108 109_add_method('MD5', '1', 8, 34) 110_add_method('CRYPT', None, 2, 13) 111 112del _v, _add_method 113