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 errno 14import string as _string 15from random import SystemRandom as _SystemRandom 16from collections import namedtuple as _namedtuple 17 18 19_saltchars = _string.ascii_letters + _string.digits + './' 20_sr = _SystemRandom() 21 22 23class _Method(_namedtuple('_Method', 'name ident salt_chars total_size')): 24 25 """Class representing a salt method per the Modular Crypt Format or the 26 legacy 2-character crypt method.""" 27 28 def __repr__(self): 29 return '<crypt.METHOD_{}>'.format(self.name) 30 31 32def mksalt(method=None, *, rounds=None): 33 """Generate a salt for the specified method. 34 35 If not specified, the strongest available method will be used. 36 37 """ 38 if method is None: 39 method = methods[0] 40 if rounds is not None and not isinstance(rounds, int): 41 raise TypeError(f'{rounds.__class__.__name__} object cannot be ' 42 f'interpreted as an integer') 43 if not method.ident: # traditional 44 s = '' 45 else: # modular 46 s = f'${method.ident}$' 47 48 if method.ident and method.ident[0] == '2': # Blowfish variants 49 if rounds is None: 50 log_rounds = 12 51 else: 52 log_rounds = int.bit_length(rounds-1) 53 if rounds != 1 << log_rounds: 54 raise ValueError('rounds must be a power of 2') 55 if not 4 <= log_rounds <= 31: 56 raise ValueError('rounds out of the range 2**4 to 2**31') 57 s += f'{log_rounds:02d}$' 58 elif method.ident in ('5', '6'): # SHA-2 59 if rounds is not None: 60 if not 1000 <= rounds <= 999_999_999: 61 raise ValueError('rounds out of the range 1000 to 999_999_999') 62 s += f'rounds={rounds}$' 63 elif rounds is not None: 64 raise ValueError(f"{method} doesn't support the rounds argument") 65 66 s += ''.join(_sr.choice(_saltchars) for char in range(method.salt_chars)) 67 return s 68 69 70def crypt(word, salt=None): 71 """Return a string representing the one-way hash of a password, with a salt 72 prepended. 73 74 If ``salt`` is not specified or is ``None``, the strongest 75 available method will be selected and a salt generated. Otherwise, 76 ``salt`` may be one of the ``crypt.METHOD_*`` values, or a string as 77 returned by ``crypt.mksalt()``. 78 79 """ 80 if salt is None or isinstance(salt, _Method): 81 salt = mksalt(salt) 82 return _crypt.crypt(word, salt) 83 84 85# available salting/crypto methods 86methods = [] 87 88def _add_method(name, *args, rounds=None): 89 method = _Method(name, *args) 90 globals()['METHOD_' + name] = method 91 salt = mksalt(method, rounds=rounds) 92 result = None 93 try: 94 result = crypt('', salt) 95 except OSError as e: 96 # Not all libc libraries support all encryption methods. 97 if e.errno == errno.EINVAL: 98 return False 99 raise 100 if result and len(result) == method.total_size: 101 methods.append(method) 102 return True 103 return False 104 105_add_method('SHA512', '6', 16, 106) 106_add_method('SHA256', '5', 16, 63) 107 108# Choose the strongest supported version of Blowfish hashing. 109# Early versions have flaws. Version 'a' fixes flaws of 110# the initial implementation, 'b' fixes flaws of 'a'. 111# 'y' is the same as 'b', for compatibility 112# with openwall crypt_blowfish. 113for _v in 'b', 'y', 'a', '': 114 if _add_method('BLOWFISH', '2' + _v, 22, 59 + len(_v), rounds=1<<4): 115 break 116 117_add_method('MD5', '1', 8, 34) 118_add_method('CRYPT', None, 2, 13) 119 120del _v, _add_method 121