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# Copyright (C) 2018 Lars Wirzenius
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import codecs
from Cryptodome.Random import get_random_bytes
from Cryptodome.Protocol.KDF import scrypt
class SecretHasher:
# The following have been chosen based on:
# https://www.pycryptodome.org/en/latest/src/protocol/kdf.html
# Corrections, with references, welcome.
_salt_size = 16
_key_len = 128
_N = 16384
_r = 8
_p = 1
_version = 1
_ok_args = ['salt', 'key_len', 'N', 'r', 'p']
def get_salt(self):
return get_random_bytes(self._salt_size)
def set_n(self, n):
self._N = n
def _full_hash(self, cleartext, **kwargs):
assert kwargs == self._filter_kwargs(kwargs)
hashed_binary = scrypt(cleartext, **kwargs)
params = {
'version': self._version,
'hash': self.hex_encode(hashed_binary),
'salt': self.hex_encode(kwargs['salt'])
}
for key in kwargs:
if key not in params:
params[key] = kwargs[key]
return params
def hex_encode(self, byte_string):
return codecs.encode(byte_string, 'hex').decode('ascii')
def hex_decode(self, hex_string):
return codecs.decode(bytes(hex_string, 'ascii'), 'hex')
def _filter_kwargs(self, kwargs):
return {
key: kwargs[key]
for key in self._ok_args
}
def hash(self, cleartext, salt=None):
if salt is None:
salt = self.get_salt()
assert isinstance(salt, bytes)
kwargs = {
'salt': salt,
'key_len': self._key_len,
'N': self._N,
'r': self._r,
'p': self._p,
}
return self._full_hash(cleartext, **kwargs)
def is_correct(self, hashed, cleartext):
kwargs = self._filter_kwargs(hashed)
salt = self.hex_decode(kwargs.pop('salt'))
h2 = self._full_hash(cleartext, salt=salt, **kwargs)
return hashed == h2
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