Python3 is removing crypt.crypt and not replacing it with anything ¯\_(ツ)_/¯
Sat 13 Jan 2024 16:53 CET
Python 3.13 will, for inscrutable reasons, remove the crypt
module from
the standard library. The excuses given in PEP
0594 boil down to “here are some
good reasons why new code shouldn’t use this module.” What about existing
code? Ah well.
So anyway, for those of us who need some way of generating $6$
SHAcrypt
SHA-512 shadow-password-database entries from Python, stick the following
module into your codebase (you can also download it, shacrypt512.py) and replace code like
crypt.crypt(password, salt=crypt.METHOD_SHA512)
crypt.crypt(password, '$6$salt$...')
crypt.crypt(password, '$6$salt$...') == '$6$salt$...'
with
shacrypt512.shacrypt(password.encode('utf-8'))
shacrypt512.shacrypt(password.encode('utf-8'), b'salt')
shacrypt512.password_ok(password.encode('utf-8'), '$6$salt$...')
respectively.
Without further ado, here’s shacrypt512.py:
# SHAcrypt using SHA-512, after https://akkadia.org/drepper/SHA-crypt.txt.
#
# Copyright © 2024 Tony Garnock-Jones.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import hashlib
import secrets
alphabet = \
[ord(c) for c in './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz']
permutation = [
[0, 21, 42], [22, 43, 1], [44, 2, 23], [3, 24, 45],
[25, 46, 4], [47, 5, 26], [6, 27, 48], [28, 49, 7],
[50, 8, 29], [9, 30, 51], [31, 52, 10], [53, 11, 32],
[12, 33, 54], [34, 55, 13], [56, 14, 35], [15, 36, 57],
[37, 58, 16], [59, 17, 38], [18, 39, 60], [40, 61, 19],
[62, 20, 41], [-1, -1, 63],
]
def encode(bs64):
result = bytearray(4 * len(permutation))
i = 0
for group in permutation:
g = lambda j: bs64[j] if j != -1 else 0
bits = g(group[0]) << 16 | g(group[1]) << 8 | g(group[2])
result[i] = alphabet[bits & 63]
result[i+1] = alphabet[(bits >> 6) & 63]
result[i+2] = alphabet[(bits >> 12) & 63]
result[i+3] = alphabet[(bits >> 18) & 63]
i = i + 4
return bytes(result).decode('ascii')[:-2]
def repeats_of(n, bs): return bs * int(n / len(bs)) + bs[:n % len(bs)]
def digest(bs): return hashlib.sha512(bs).digest()
def shacrypt(password, salt = None, rounds = 5000):
if salt is None: salt = encode(secrets.token_bytes(64))[:16].encode('ascii')
salt = salt[:16]
B = digest(password + salt + password)
Ainput = password + salt + repeats_of(len(password), B)
v = len(password)
while v > 0:
Ainput = Ainput + (B if v & 1 else password)
v = v >> 1
A = digest(Ainput)
DP = digest(password * len(password))
P = repeats_of(len(password), DP)
DS = digest(salt * (16+A[0]))
S = repeats_of(len(salt), DS)
C = A
for round in range(rounds):
Cinput = b''
Cinput = Cinput + (P if round & 1 else C)
if round % 3: Cinput = Cinput + S
if round % 7: Cinput = Cinput + P
Cinput = Cinput + (C if round & 1 else P)
C = digest(Cinput)
if rounds == 5000:
return '$6$' + salt.decode('ascii') + '$' + encode(C)
else:
return '$6$rounds=' + str(rounds) + '$' + salt.decode('ascii') + '$' + encode(C)
#---------------------------------------------------------------------------
def extract_salt_and_rounds(i): # i must be '$6$...'
pieces = i.split('$')
if pieces[1] != '6': raise TypeError('shacrypt512 only supports $6$ hashes')
if pieces[2].startswith('rounds='):
rounds = int(pieces[2][7:])
if rounds < 1000: rounds = 1000
if rounds > 999999999: rounds = 999999999
return (pieces[3].encode('ascii'), rounds)
else:
return (pieces[2].encode('ascii'), 5000)
def password_ok(input_password, existing_crypted_password):
(salt, rounds) = extract_salt_and_rounds(existing_crypted_password)
return existing_crypted_password == shacrypt(input_password, salt, rounds)
if __name__ == '__main__':
_test_password = 'Hello world!'.encode('ascii')
_test_salt = 'saltstring'.encode('ascii')
_test_rounds = 5000
_test_crypted_password = '$6$saltstring$svn8UoSVapNtMuq1ukKS4tPQd8iKwSMHWjl/O817G3uBnIFNjnQJuesI68u4OTLiBFdcbYEdFCoEOfaS35inz1'
assert shacrypt(_test_password, _test_salt, _test_rounds) == _test_crypted_password
assert password_ok(_test_password, _test_crypted_password)
_test_password = 'Hello world!'.encode('ascii')
_test_salt = 'saltstringsaltstring'.encode('ascii')
_test_rounds = 10000
_test_crypted_password = '$6$rounds=10000$saltstringsaltst$OW1/O6BYHV6BcXZu8QVeXbDWra3Oeqh0sbHbbMCVNSnCM/UrjmM0Dp8vOuZeHBy/YTBmSK6H9qs/y3RnOaw5v.'
assert shacrypt(_test_password, _test_salt, _test_rounds) == _test_crypted_password
assert password_ok(_test_password, _test_crypted_password)
import sys
salt = None if len(sys.argv) < 2 else sys.argv[1].encode('ascii')
print(shacrypt(sys.stdin.readline().strip().encode('utf-8'), salt))