134 lines
4.2 KiB
Python
134 lines
4.2 KiB
Python
# hkdf.py
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#
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# Copyright (C) 2025 wolfSSL Inc.
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#
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# This file is part of wolfSSL. (formerly known as CyaSSL)
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#
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# wolfSSL is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# wolfSSL is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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# pylint: disable=no-member,no-name-in-module
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from wolfcrypt._ffi import ffi as _ffi
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from wolfcrypt._ffi import lib as _lib
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from wolfcrypt.exceptions import WolfCryptError
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from wolfcrypt.utils import t2b
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if _lib.HKDF_ENABLED:
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def HKDF(hash_cls, in_key, salt=None, info=None, out_len=None):
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"""
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Perform HKDF Extract-and-Expand in one call (wraps wc_HKDF).
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Parameters:
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- hash_cls: hash class, see `wolfcrypt.hashes`.
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- in_key: input key material (IKM) as bytes or str.
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- salt: optional salt value (bytes or str). If None, treated as empty.
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- info: optional context/application info (bytes or str). If None,
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treated as empty.
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- out_len: desired length of output keying material (bytes). If None,
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defaults to the digest size of the hash.
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Returns:
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- bytes object containing the derived key of length `out_len`.
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Raises:
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- WolfCryptError on failure.
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- ValueError for invalid arguments.
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"""
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in_key = t2b(in_key)
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salt = b"" if salt is None else t2b(salt)
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info = b"" if info is None else t2b(info)
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if out_len is None:
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out_len = hash_cls.digest_size
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out = _ffi.new("byte[%d]" % out_len)
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ret = _lib.wc_HKDF(
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hash_cls._type,
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in_key,
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len(in_key),
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salt,
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len(salt),
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info,
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len(info),
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out,
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out_len,
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)
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if ret != 0:
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raise WolfCryptError("HKDF error (%d)" % ret)
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return _ffi.buffer(out, out_len)[:]
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def HKDF_Extract(hash_cls, salt, in_key):
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"""
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HKDF-Extract: PRK = HMAC-Hash(salt, IKM)
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Wraps wc_HKDF_Extract.
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Parameters:
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- hash_cls: hash class, see `wolfcrypt.hashes`.
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- salt: bytes/str (can be None -> treated as empty).
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- in_key: input key material (IKM) as bytes/str.
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Returns:
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- PRK as bytes (length == hash digest size).
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Raises WolfCryptError on failure.
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"""
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salt = b"" if salt is None else t2b(salt)
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in_key = t2b(in_key)
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out_len = hash_cls.digest_size
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out = _ffi.new("byte[%d]" % out_len)
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ret = _lib.wc_HKDF_Extract(hash_cls._type, salt, len(salt), in_key, len(in_key), out)
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if ret != 0:
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raise WolfCryptError("HKDF_Extract error (%d)" % ret)
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return _ffi.buffer(out, out_len)[:]
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def HKDF_Expand(hash_cls, prk, info, out_len):
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"""
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HKDF-Expand: OKM = HKDF-Expand(PRK, info, L)
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Wraps wc_HKDF_Expand.
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Parameters:
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- hash_cls: hash class, see `wolfcrypt.hashes`.
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- prk: pseudorandom key (output from HKDF-Extract) as bytes/str.
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- info: optional context/application info (bytes/str). If None, treated as empty.
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- out_len: length of output keying material in bytes.
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Returns:
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- OKM as bytes of length `out_len`.
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Raises WolfCryptError on failure.
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"""
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prk = t2b(prk)
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info = b"" if info is None else t2b(info)
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if out_len is None or out_len <= 0:
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raise ValueError("out_len must be a positive integer")
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out = _ffi.new("byte[%d]" % out_len)
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ret = _lib.wc_HKDF_Expand(
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hash_cls._type, prk, len(prk), info, len(info), out, out_len
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)
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if ret != 0:
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raise WolfCryptError("HKDF_Expand error (%d)" % ret)
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return _ffi.buffer(out, out_len)[:]
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