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https://github.com/markqvist/Reticulum.git
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ddb7a92c15
The second if isn't needed since we initialize the salt with zeroes earlier. If instead we meant to pass an empty bytes class to the HMAC implementation, the end result would be the same, since it's gonna get padded with zeroes in the HMAC code.
55 lines
1.9 KiB
Python
55 lines
1.9 KiB
Python
# MIT License
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#
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# Copyright (c) 2022 Mark Qvist / unsigned.io
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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import hashlib
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from math import ceil
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from RNS.Cryptography import HMAC
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def hkdf(length=None, derive_from=None, salt=None, context=None):
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hash_len = 32
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def hmac_sha256(key, data):
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return HMAC.new(key, data).digest()
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if length == None or length < 1:
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raise ValueError("Invalid output key length")
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if derive_from == None or derive_from == "":
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raise ValueError("Cannot derive key from empty input material")
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if salt == None or len(salt) == 0:
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salt = bytes([0] * hash_len)
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if context == None:
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context = b""
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pseudorandom_key = hmac_sha256(salt, derive_from)
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block = b""
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derived = b""
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for i in range(ceil(length / hash_len)):
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block = hmac_sha256(pseudorandom_key, block + context + bytes([i + 1]))
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derived += block
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return derived[:length]
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