diff options
| -rw-r--r-- | Doc/library/crypt.rst | 106 | ||||
| -rw-r--r-- | Lib/crypt.py | 61 | ||||
| -rw-r--r-- | Lib/test/test_crypt.py | 17 | ||||
| -rw-r--r-- | Misc/NEWS | 4 | ||||
| -rw-r--r-- | Modules/Setup.dist | 2 | ||||
| -rw-r--r-- | Modules/_cryptmodule.c (renamed from Modules/cryptmodule.c) | 4 | ||||
| -rw-r--r-- | setup.py | 2 |
7 files changed, 183 insertions, 13 deletions
diff --git a/Doc/library/crypt.rst b/Doc/library/crypt.rst index 0be571e..a5556cf 100644 --- a/Doc/library/crypt.rst +++ b/Doc/library/crypt.rst @@ -15,9 +15,9 @@ This module implements an interface to the :manpage:`crypt(3)` routine, which is a one-way hash function based upon a modified DES algorithm; see the Unix man -page for further details. Possible uses include allowing Python scripts to -accept typed passwords from the user, or attempting to crack Unix passwords with -a dictionary. +page for further details. Possible uses include storing hashed passwords +so you can check passwords without storing the actual password, or attempting +to crack Unix passwords with a dictionary. .. index:: single: crypt(3) @@ -26,15 +26,67 @@ the :manpage:`crypt(3)` routine in the running system. Therefore, any extensions available on the current implementation will also be available on this module. +Hashing Methods +--------------- -.. function:: crypt(word, salt) +The :mod:`crypt` module defines the list of hashing methods (not all methods +are available on all platforms): + +.. data:: METHOD_SHA512 + + A Modular Crypt Format method with 16 character salt and 86 character + hash. This is the strongest method. + +.. versionadded:: 3.3 + +.. data:: METHOD_SHA256 + + Another Modular Crypt Format method with 16 character salt and 43 + character hash. + +.. versionadded:: 3.3 + +.. data:: METHOD_MD5 + + Another Modular Crypt Format method with 8 character salt and 22 + character hash. + +.. versionadded:: 3.3 + +.. data:: METHOD_CRYPT + + The traditional method with a 2 character salt and 13 characters of + hash. This is the weakest method. + +.. versionadded:: 3.3 + +Module Functions +---------------- + +The :mod:`crypt` module defines the following functions: + +.. function:: crypt(word, salt=None) *word* will usually be a user's password as typed at a prompt or in a graphical - interface. *salt* is usually a random two-character string which will be used - to perturb the DES algorithm in one of 4096 ways. The characters in *salt* must - be in the set ``[./a-zA-Z0-9]``. Returns the hashed password as a string, which - will be composed of characters from the same alphabet as the salt (the first two - characters represent the salt itself). + interface. The optional *salt* is either a string as returned from + :func:`mksalt`, one of the ``crypt.METHOD_*`` values (though not all + may be available on all platforms), or a full encrypted password + including salt, as returned by this function. If *salt* is not + provided, the strongest method will be used (as returned by + :func:`methods`. + + Checking a password is usually done by passing the plain-text password + as *word* and the full results of a previous :func:`crypt` call, + which should be the same as the results of this call. + + *salt* (either a random 2 or 16 character string, possibly prefixed with + ``$digit$`` to indicate the method) which will be used to perturb the + encryption algorithm. The characters in *salt* must be in the set + ``[./a-zA-Z0-9]``, with the exception of Modular Crypt Format which + prefixes a ``$digit$``. + + Returns the hashed password as a string, which will be composed of + characters from the same alphabet as the salt. .. index:: single: crypt(3) @@ -42,6 +94,34 @@ this module. different sizes in the *salt*, it is recommended to use the full crypted password as salt when checking for a password. +.. versionchanged:: 3.3 + Before version 3.3, *salt* must be specified as a string and cannot + accept ``crypt.METHOD_*`` values (which don't exist anyway). + +.. function:: methods() + + Return a list of available password hashing algorithms, as + ``crypt.METHOD_*`` objects. This list is sorted from strongest to + weakest, and is guaranteed to have at least ``crypt.METHOD_CRYPT``. + +.. versionadded:: 3.3 + +.. function:: mksalt(method=None) + + Return a randomly generated salt of the specified method. If no + *method* is given, the strongest method available as returned by + :func:`methods` is used. + + The return value is a string either of 2 characters in length for + ``crypt.METHOD_CRYPT``, or 19 characters starting with ``$digit$`` and + 16 random characters from the set ``[./a-zA-Z0-9]``, suitable for + passing as the *salt* argument to :func:`crypt`. + +.. versionadded:: 3.3 + +Examples +-------- + A simple example illustrating typical use:: import crypt, getpass, pwd @@ -57,3 +137,11 @@ A simple example illustrating typical use:: else: return 1 +To generate a hash of a password using the strongest available method and +check it against the original:: + + import crypt + + hashed = crypt.crypt(plaintext) + if hashed != crypt.crypt(plaintext, hashed): + raise "Hashed version doesn't validate against original" diff --git a/Lib/crypt.py b/Lib/crypt.py new file mode 100644 index 0000000..dc62dba --- /dev/null +++ b/Lib/crypt.py @@ -0,0 +1,61 @@ +'''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)) diff --git a/Lib/test/test_crypt.py b/Lib/test/test_crypt.py index 2adb28d..cb4234b 100644 --- a/Lib/test/test_crypt.py +++ b/Lib/test/test_crypt.py @@ -10,6 +10,23 @@ class CryptTestCase(unittest.TestCase): if support.verbose: print('Test encryption: ', c) + def test_salt(self): + self.assertEqual(len(crypt.saltchars), 64) + for method in crypt.methods(): + salt = crypt.mksalt(method) + self.assertEqual(len(salt), + method.salt_chars + (3 if method.ident else 0)) + + def test_saltedcrypt(self): + for method in crypt.methods(): + pw = crypt.crypt('assword', method) + self.assertEqual(len(pw), method.total_size) + pw = crypt.crypt('assword', crypt.mksalt(method)) + self.assertEqual(len(pw), method.total_size) + + def test_methods(self): + self.assertTrue(len(crypt.methods()) > 1) + def test_main(): support.run_unittest(CryptTestCase) @@ -27,6 +27,10 @@ Core and Builtins Library ------- +- Issue #10924: Adding salt and Modular Crypt Format to crypt library. + Moved old C wrapper to _crypt, and added a Python wrapper with + enhanced salt generation and simpler API for password generation. + - Issue #11074: Make 'tokenize' so it can be reloaded. - Issue #11085: Moved collections abstract base classes into a separate diff --git a/Modules/Setup.dist b/Modules/Setup.dist index e1c8fe4..56f3314 100644 --- a/Modules/Setup.dist +++ b/Modules/Setup.dist @@ -207,7 +207,7 @@ _symtable symtablemodule.c # # First, look at Setup.config; configure may have set this for you. -#crypt cryptmodule.c # -lcrypt # crypt(3); needs -lcrypt on some systems +#_crypt _cryptmodule.c # -lcrypt # crypt(3); needs -lcrypt on some systems # Some more UNIX dependent modules -- off by default, since these diff --git a/Modules/cryptmodule.c b/Modules/_cryptmodule.c index d5a42ff..5100788 100644 --- a/Modules/cryptmodule.c +++ b/Modules/_cryptmodule.c @@ -45,7 +45,7 @@ static PyMethodDef crypt_methods[] = { static struct PyModuleDef cryptmodule = { PyModuleDef_HEAD_INIT, - "crypt", + "_crypt", NULL, -1, crypt_methods, @@ -56,7 +56,7 @@ static struct PyModuleDef cryptmodule = { }; PyMODINIT_FUNC -PyInit_crypt(void) +PyInit__crypt(void) { return PyModule_Create(&cryptmodule); } @@ -636,7 +636,7 @@ class PyBuildExt(build_ext): libs = ['crypt'] else: libs = [] - exts.append( Extension('crypt', ['cryptmodule.c'], libraries=libs) ) + exts.append( Extension('_crypt', ['_cryptmodule.c'], libraries=libs) ) # CSV files exts.append( Extension('_csv', ['_csv.c']) ) |