112 lines
3.7 KiB
Python
112 lines
3.7 KiB
Python
###############################################################################
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#
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# The MIT License (MIT)
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#
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# Copyright (c) Crossbar.io Technologies GmbH
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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
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# all 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
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# THE SOFTWARE.
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#
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###############################################################################
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import hashlib
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from typing import Optional
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import argon2
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import hkdf
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def stretch_argon2_secret(email: str, password: str, salt: Optional[bytes] = None) -> bytes:
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"""
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Compute argon2id based secret from user email and password only. This uses Argon2id
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for stretching a potentially weak user password/PIN and subsequent HKDF based key
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extending to derive private key material (PKM) for different usage contexts.
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The Argon2 parameters used are the following:
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* kdf ``argon2id-13``
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* time cost ``4096``
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* memory cost ``512``
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* parallelism ``1``
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See `draft-irtf-cfrg-argon2 <https://datatracker.ietf.org/doc/draft-irtf-cfrg-argon2/>`__ and
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`argon2-cffi <https://argon2-cffi.readthedocs.io/en/stable/>`__.
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:param email: User email.
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:param password: User password.
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:param salt: Optional salt to use (must be 16 bytes long). If none is given, compute salt
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from email as ``salt = SHA256(email)[:16]``.
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:return: The computed private key material (256b, 32 octets).
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"""
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if not salt:
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m = hashlib.sha256()
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m.update(email.encode('utf8'))
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salt = m.digest()[:16]
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assert len(salt) == 16
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pkm = argon2.low_level.hash_secret_raw(
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secret=password.encode('utf8'),
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salt=salt,
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time_cost=4096,
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memory_cost=512,
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parallelism=1,
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hash_len=32,
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type=argon2.low_level.Type.ID,
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version=19,
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)
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return pkm
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def expand_argon2_secret(pkm: bytes, context: bytes, salt: Optional[bytes] = None) -> bytes:
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"""
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Expand ``pkm`` and ``context`` into a key of length ``bytes`` using
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HKDF's expand function based on HMAC SHA-512). See the HKDF draft RFC and paper for usage notes.
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:param pkm:
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:param context:
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:param salt:
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:return:
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"""
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kdf = hkdf.Hkdf(salt=salt, input_key_material=pkm, hash=hashlib.sha512)
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key = kdf.expand(info=context, length=32)
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return key
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def pkm_from_argon2_secret(email: str, password: str, context: str, salt: Optional[bytes] = None) -> bytes:
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"""
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:param email:
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:param password:
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:param context:
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:param salt:
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:return:
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"""
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if not salt:
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m = hashlib.sha256()
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m.update(email.encode('utf8'))
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salt = m.digest()[:16]
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assert len(salt) == 16
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context = context.encode('utf8')
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pkm = stretch_argon2_secret(email=email, password=password, salt=salt)
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key = expand_argon2_secret(pkm=pkm, context=context, salt=salt)
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return key
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