55 lines
1.9 KiB
Python
55 lines
1.9 KiB
Python
# MIT License
|
|
#
|
|
# Copyright (c) 2022 Mark Qvist / unsigned.io
|
|
#
|
|
# 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
|
|
from math import ceil
|
|
from RNS.Cryptography import HMAC
|
|
|
|
def hkdf(length=None, derive_from=None, salt=None, context=None):
|
|
hash_len = 32
|
|
|
|
def hmac_sha256(key, data):
|
|
return HMAC.new(key, data).digest()
|
|
|
|
if length == None or length < 1:
|
|
raise ValueError("Invalid output key length")
|
|
|
|
if derive_from == None or derive_from == "":
|
|
raise ValueError("Cannot derive key from empty input material")
|
|
|
|
if salt == None or len(salt) == 0:
|
|
salt = bytes([0] * hash_len)
|
|
|
|
if context == None:
|
|
context = b""
|
|
|
|
pseudorandom_key = hmac_sha256(salt, derive_from)
|
|
|
|
block = b""
|
|
derived = b""
|
|
|
|
for i in range(ceil(length / hash_len)):
|
|
block = hmac_sha256(pseudorandom_key, block + context + bytes([i + 1]))
|
|
derived += block
|
|
|
|
return derived[:length]
|