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'''Wrapper to the POSIX crypt library call and associated functionality.
'''
import _crypt
saltchars = 'abcdefghijklmnopqrstuvwxyz'
saltchars += saltchars.upper()
saltchars += '0123456789./'
class _MethodClass:
'''Class representing a salt method per the Modular Crypt Format or the
legacy 2-character crypt method.'''
def __init__(self, name, ident, salt_chars, total_size):
self.name = name
self.ident = ident
self.salt_chars = salt_chars
self.total_size = total_size
def __repr__(self):
return '<crypt.METHOD_%s>' % self.name
# available salting/crypto methods
METHOD_CRYPT = _MethodClass('CRYPT', None, 2, 13)
METHOD_MD5 = _MethodClass('MD5', '1', 8, 34)
METHOD_SHA256 = _MethodClass('SHA256', '5', 16, 63)
METHOD_SHA512 = _MethodClass('SHA512', '6', 16, 106)
def methods():
'''Return a list of methods that are available in the platform ``crypt()``
library, sorted from strongest to weakest. This is guaranteed to always
return at least ``[METHOD_CRYPT]``'''
method_list = [ METHOD_SHA512, METHOD_SHA256, METHOD_MD5 ]
ret = [ method for method in method_list
if len(crypt('', method)) == method.total_size ]
ret.append(METHOD_CRYPT)
return ret
def mksalt(method = None):
'''Generate a salt for the specified method. If not specified, the
strongest available method will be used.'''
import random
if method == None: method = methods()[0]
s = '$%s$' % method.ident if method.ident else ''
s += ''.join([ random.choice(saltchars) for x in range(method.salt_chars) ])
return(s)
def crypt(word, salt = None):
'''Return a string representing the one-way hash of a password, preturbed
by a salt. 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 == None: salt = mksalt()
elif isinstance(salt, _MethodClass): salt = mksalt(salt)
return(_crypt.crypt(word, salt))
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