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# Copyright [2017] [Adam Bishop]
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Imported from https://github.com/TheMysteriousX/SNMPv3-Hash-Generator
import hashlib
import string
import secrets
from itertools import repeat
P_LEN = 32
E_LEN = 16
class Hashgen(object):
@staticmethod
def md5(bytes):
return hashlib.md5(bytes).digest().hex()
@staticmethod
def sha1(bytes):
return hashlib.sha1(bytes).digest().hex()
@staticmethod
def expand(s, l):
reps = l // len(s) + 1 # approximation; worst case: overrun = l + len(s)
return ''.join(list(repeat(s, reps)))[:l]
@classmethod
def kdf(cls, password):
data = cls.expand(password, 1048576).encode('utf-8')
return hashlib.sha1(data).digest()
@staticmethod
def random_string(len=P_LEN, alphabet=(string.ascii_letters + string.digits)):
return ''.join(secrets.choice(alphabet) for _ in range(len))
@staticmethod
def random_engine(len=E_LEN):
return secrets.token_hex(len)
@classmethod
def derive_msg(cls, passphrase, engine):
# Parameter derivation á la rfc3414
Ku = cls.kdf(passphrase)
E = bytearray.fromhex(engine)
return b''.join([Ku, E, Ku])
# Define available hash algorithms
algs = {
'sha1': sha1,
'md5': md5,
}
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