bpo-31702: Allow to specify rounds for SHA-2 hashing in crypt.mksalt(). (#4110)

The log_rounds parameter for Blowfish has been replaced with the rounds parameter.
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Serhiy Storchaka 2017-11-16 13:22:51 +02:00 committed by GitHub
parent ccb0442a33
commit cede8c9edb
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5 changed files with 74 additions and 28 deletions

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@ -116,7 +116,7 @@ The :mod:`crypt` module defines the following functions:
Accept ``crypt.METHOD_*`` values in addition to strings for *salt*.
.. function:: mksalt(method=None, *, log_rounds=12)
.. function:: mksalt(method=None, *, rounds=None)
Return a randomly generated salt of the specified method. If no
*method* is given, the strongest method available as returned by
@ -125,14 +125,18 @@ The :mod:`crypt` module defines the following functions:
The return value is a string suitable for passing as the *salt* argument
to :func:`crypt`.
*log_rounds* specifies the binary logarithm of the number of rounds
for ``crypt.METHOD_BLOWFISH``, and is ignored otherwise. ``8`` specifies
``256`` rounds.
*rounds* specifies the number of rounds for ``METHOD_SHA256``,
``METHOD_SHA512`` and ``METHOD_BLOWFISH``.
For ``METHOD_SHA256`` and ``METHOD_SHA512`` it must be an integer between
``1000`` and ``999_999_999``, the default is ``5000``. For
``METHOD_BLOWFISH`` it must be a power of two between ``16`` (2\ :sup:`4`)
and ``2_147_483_648`` (2\ :sup:`31`), the default is ``4096``
(2\ :sup:`12`).
.. versionadded:: 3.3
.. versionchanged:: 3.7
Added the *log_rounds* parameter.
Added the *rounds* parameter.
Examples

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@ -280,6 +280,9 @@ crypt
Added support for the Blowfish method.
(Contributed by Serhiy Storchaka in :issue:`31664`.)
The :func:`~crypt.mksalt` function now allows to specify the number of rounds
for hashing. (Contributed by Serhiy Storchaka in :issue:`31702`.)
dis
---

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@ -19,7 +19,7 @@ class _Method(_namedtuple('_Method', 'name ident salt_chars total_size')):
return '<crypt.METHOD_{}>'.format(self.name)
def mksalt(method=None, *, log_rounds=12):
def mksalt(method=None, *, rounds=None):
"""Generate a salt for the specified method.
If not specified, the strongest available method will be used.
@ -27,12 +27,32 @@ def mksalt(method=None, *, log_rounds=12):
"""
if method is None:
method = methods[0]
if not method.ident:
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 = ''
elif method.ident[0] == '2':
s = f'${method.ident}${log_rounds:02d}$'
else:
else: # modular
s = f'${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
@ -55,10 +75,10 @@ def crypt(word, salt=None):
# available salting/crypto methods
methods = []
def _add_method(name, *args):
def _add_method(name, *args, rounds=None):
method = _Method(name, *args)
globals()['METHOD_' + name] = method
salt = mksalt(method, log_rounds=4)
salt = mksalt(method, rounds=rounds)
result = crypt('', salt)
if result and len(result) == method.total_size:
methods.append(method)
@ -74,7 +94,7 @@ _add_method('SHA256', '5', 16, 63)
# '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)):
if _add_method('BLOWFISH', '2' + _v, 22, 59 + len(_v), rounds=1<<4):
break
_add_method('MD5', '1', 8, 34)

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@ -39,12 +39,26 @@ class CryptTestCase(unittest.TestCase):
else:
self.assertEqual(crypt.methods[-1], crypt.METHOD_CRYPT)
@unittest.skipUnless(crypt.METHOD_SHA256 in crypt.methods or
crypt.METHOD_SHA512 in crypt.methods,
'requires support of SHA-2')
def test_sha2_rounds(self):
for method in (crypt.METHOD_SHA256, crypt.METHOD_SHA512):
for rounds in 1000, 10_000, 100_000:
salt = crypt.mksalt(method, rounds=rounds)
self.assertIn('$rounds=%d$' % rounds, salt)
self.assertEqual(len(salt) - method.salt_chars,
11 + len(str(rounds)))
cr = crypt.crypt('mypassword', salt)
self.assertTrue(cr)
cr2 = crypt.crypt('mypassword', cr)
self.assertEqual(cr2, cr)
@unittest.skipUnless(crypt.METHOD_BLOWFISH in crypt.methods,
'requires support of Blowfish')
def test_log_rounds(self):
self.assertEqual(len(crypt._saltchars), 64)
def test_blowfish_rounds(self):
for log_rounds in range(4, 11):
salt = crypt.mksalt(crypt.METHOD_BLOWFISH, log_rounds=log_rounds)
salt = crypt.mksalt(crypt.METHOD_BLOWFISH, rounds=1 << log_rounds)
self.assertIn('$%02d$' % log_rounds, salt)
self.assertIn(len(salt) - crypt.METHOD_BLOWFISH.salt_chars, {6, 7})
cr = crypt.crypt('mypassword', salt)
@ -52,18 +66,21 @@ class CryptTestCase(unittest.TestCase):
cr2 = crypt.crypt('mypassword', cr)
self.assertEqual(cr2, cr)
@unittest.skipUnless(crypt.METHOD_BLOWFISH in crypt.methods,
'requires support of Blowfish')
def test_invalid_log_rounds(self):
for log_rounds in (1, -1, 999):
salt = crypt.mksalt(crypt.METHOD_BLOWFISH, log_rounds=log_rounds)
cr = crypt.crypt('mypassword', salt)
if cr is not None:
# On failure the openwall implementation returns a magic
# string that is shorter than 13 characters and is guaranteed
# to differ from a salt.
self.assertNotEqual(cr, salt)
self.assertLess(len(cr), 13)
def test_invalid_rounds(self):
for method in (crypt.METHOD_SHA256, crypt.METHOD_SHA512,
crypt.METHOD_BLOWFISH):
with self.assertRaises(TypeError):
crypt.mksalt(method, rounds='4096')
with self.assertRaises(TypeError):
crypt.mksalt(method, rounds=4096.0)
for rounds in (0, 1, -1, 1<<999):
with self.assertRaises(ValueError):
crypt.mksalt(method, rounds=rounds)
with self.assertRaises(ValueError):
crypt.mksalt(crypt.METHOD_BLOWFISH, rounds=1000)
for method in (crypt.METHOD_CRYPT, crypt.METHOD_MD5):
with self.assertRaisesRegex(ValueError, 'support'):
crypt.mksalt(method, rounds=4096)
if __name__ == "__main__":

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@ -0,0 +1,2 @@
crypt.mksalt() now allows to specify the number of rounds for SHA-256 and
SHA-512 hashing.