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https://github.com/markqvist/Reticulum.git
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58 lines
2.0 KiB
Python
58 lines
2.0 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 salt == None:
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salt = b""
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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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