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Add ConcatKDF from NIST SP 800-56A
The implemention allows the use an HMAC function as per Revision 2 of the document. Conformance of the formatting of the OtherInfo argument is responsability of the calling application. Signed-off-by: Simo Sorce <simo@redhat.com>
This commit is contained in:
Simo Sorce
parent
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commit
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3 changed files with 563 additions and 0 deletions
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@ -324,6 +324,192 @@ Different KDFs are suitable for different tasks such as:
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``key_material`` generates the same key as the ``expected_key``, and
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raises an exception if they do not match.
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.. currentmodule:: cryptography.hazmat.primitives.kdf.concatkdf
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.. class:: ConcatKDFHash(algorithm, length, otherinfo, backend)
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.. versionadded:: 1.0
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ConcatKDFHash (Concatenation Key Derivation Function) is defined by the
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NIST Special Publication `NIST SP 800-56Ar2`_ document, to be used to
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derive keys for use after a Key Exchange negotiation operation.
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.. warning::
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ConcatKDFHash should not be used for password storage.
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.. doctest::
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>>> import os
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>>> from cryptography.hazmat.primitives import hashes
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>>> from cryptography.hazmat.primitives.kdf.concatkdf import ConcatKDFHash
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>>> from cryptography.hazmat.backends import default_backend
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>>> backend = default_backend()
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>>> salt = os.urandom(16)
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>>> otherinfo = b"concatkdf-example"
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>>> ckdf = ConcatKDFHash(
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... algorithm=hashes.SHA256(),
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... length=256,
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... otherinfo=otherinfo,
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... backend=backend
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... )
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>>> key = ckdf.derive(b"input key")
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>>> ckdf = ConcatKDFHash(
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... algorithm=hashes.SHA256(),
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... length=256,
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... otherinfo=otherinfo,
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... backend=backend
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... )
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>>> ckdf.verify(b"input key", key)
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:param algorithm: An instance of a
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:class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
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provider
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:param int length: The desired length of the derived key in bytes.
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Maximum is ``hashlen * (2^32 -1)``.
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:param bytes otherinfo: Application specific context information.
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If ``None`` is explicitly passed an empty byte string will be used.
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:param backend: A
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:class:`~cryptography.hazmat.backends.interfaces.HashBackend`
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provider.
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:raises cryptography.exceptions.UnsupportedAlgorithm: This is raised
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if the provided ``backend`` does not implement
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:class:`~cryptography.hazmat.backends.interfaces.HashBackend`
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:raises TypeError: This exception is raised if ``otherinfo`` is not
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``bytes``.
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.. method:: derive(key_material)
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:param bytes key_material: The input key material.
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:return bytes: The derived key.
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:raises TypeError: This exception is raised if ``key_material`` is
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not ``bytes``.
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Derives a new key from the input key material by performing both the
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extract and expand operations.
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.. method:: verify(key_material, expected_key)
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:param bytes key_material: The input key material. This is the same as
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``key_material`` in :meth:`derive`.
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:param bytes expected_key: The expected result of deriving a new key,
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this is the same as the return value of
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:meth:`derive`.
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:raises cryptography.exceptions.InvalidKey: This is raised when the
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derived key does not match
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the expected key.
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:raises cryptography.exceptions.AlreadyFinalized: This is raised when
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:meth:`derive` or
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:meth:`verify` is
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called more than
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once.
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This checks whether deriving a new key from the supplied
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``key_material`` generates the same key as the ``expected_key``, and
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raises an exception if they do not match.
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.. class:: ConcatKDFHMAC(algorithm, length, salt, otherinfo, backend)
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.. versionadded:: 1.0
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Similar to ConcatKFDHash but uses an HMAC function instead.
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.. warning::
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ConcatKDFHMAC should not be used for password storage.
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.. doctest::
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>>> import os
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>>> from cryptography.hazmat.primitives import hashes
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>>> from cryptography.hazmat.primitives.kdf.concatkdf import ConcatKDFHMAC
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>>> from cryptography.hazmat.backends import default_backend
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>>> backend = default_backend()
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>>> salt = os.urandom(16)
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>>> otherinfo = b"concatkdf-example"
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>>> ckdf = ConcatKDFHMAC(
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... algorithm=hashes.SHA256(),
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... length=256,
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... salt=salt,
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... otherinfo=otherinfo,
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... backend=backend
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... )
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>>> key = ckdf.derive(b"input key")
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>>> ckdf = ConcatKDFHMAC(
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... algorithm=hashes.SHA256(),
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... length=256,
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... salt=salt,
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... otherinfo=otherinfo,
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... backend=backend
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... )
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>>> ckdf.verify(b"input key", key)
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:param algorithm: An instance of a
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:class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
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provider
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:param int length: The desired length of the derived key in bytes. Maximum
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is ``hashlen * (2^32 -1)``.
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:param bytes salt: A salt. Randomizes the KDF's output. Optional, but
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highly recommended. Ideally as many bits of entropy as the security
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level of the hash: often that means cryptographically random and as
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long as the hash output. Does not have to be secret, but may cause
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stronger security guarantees if secret; If ``None`` is explicitly
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passed a default salt of ``algorithm.block_size`` null bytes will be
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used.
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:param bytes otherinfo: Application specific context information.
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If ``None`` is explicitly passed an empty byte string will be used.
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:param backend: A
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:class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
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provider.
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:raises cryptography.exceptions.UnsupportedAlgorithm: This is raised if the
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provided ``backend`` does not implement
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:class:`~cryptography.hazmat.backends.interfaces.HMACBackend`
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:raises TypeError: This exception is raised if ``salt`` or ``otherinfo``
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is not ``bytes``.
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.. method:: derive(key_material)
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:param bytes key_material: The input key material.
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:return bytes: The derived key.
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:raises TypeError: This exception is raised if ``key_material`` is not
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``bytes``.
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Derives a new key from the input key material by performing both the
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extract and expand operations.
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.. method:: verify(key_material, expected_key)
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:param bytes key_material: The input key material. This is the same as
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``key_material`` in :meth:`derive`.
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:param bytes expected_key: The expected result of deriving a new key,
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this is the same as the return value of
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:meth:`derive`.
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:raises cryptography.exceptions.InvalidKey: This is raised when the
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derived key does not match
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the expected key.
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:raises cryptography.exceptions.AlreadyFinalized: This is raised when
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:meth:`derive` or
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:meth:`verify` is
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called more than
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once.
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This checks whether deriving a new key from the supplied
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``key_material`` generates the same key as the ``expected_key``, and
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raises an exception if they do not match.
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Interface
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~~~~~~~~~
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@ -372,6 +558,7 @@ Interface
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.. _`NIST SP 800-132`: http://csrc.nist.gov/publications/nistpubs/800-132/nist-sp800-132.pdf
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.. _`NIST SP 800-56Ar2`: http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-56Ar2.pdf
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.. _`Password Storage Cheat Sheet`: https://www.owasp.org/index.php/Password_Storage_Cheat_Sheet
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.. _`PBKDF2`: https://en.wikipedia.org/wiki/PBKDF2
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.. _`scrypt`: https://en.wikipedia.org/wiki/Scrypt
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125
src/cryptography/hazmat/primitives/kdf/concatkdf.py
Normal file
125
src/cryptography/hazmat/primitives/kdf/concatkdf.py
Normal file
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@ -0,0 +1,125 @@
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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import struct
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from cryptography import utils
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from cryptography.exceptions import (
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AlreadyFinalized, InvalidKey, UnsupportedAlgorithm, _Reasons
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)
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from cryptography.hazmat.backends.interfaces import HMACBackend
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from cryptography.hazmat.backends.interfaces import HashBackend
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from cryptography.hazmat.primitives import constant_time, hashes, hmac
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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def _int_to_u32be(n):
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return struct.pack('>I', n)
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def _common_args_checks(algorithm, length, otherinfo):
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max_length = algorithm.digest_size * (2 ** 32 - 1)
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if length > max_length:
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raise ValueError(
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"Can not derive keys larger than {0} bits.".format(
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max_length
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))
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if not (otherinfo is None or isinstance(otherinfo, bytes)):
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raise TypeError("otherinfo must be bytes.")
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def _concatkdf_derive(key_material, length, auxfn, otherinfo):
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if not isinstance(key_material, bytes):
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raise TypeError("key_material must be bytes.")
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output = [b""]
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outlen = 0
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counter = 1
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while (length > outlen):
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h = auxfn()
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h.update(_int_to_u32be(counter))
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h.update(key_material)
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h.update(otherinfo)
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output.append(h.finalize())
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outlen += len(output[-1])
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counter += 1
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return b"".join(output)[:length]
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@utils.register_interface(KeyDerivationFunction)
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class ConcatKDFHash(object):
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def __init__(self, algorithm, length, otherinfo, backend):
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo = otherinfo
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if self._otherinfo is None:
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self._otherinfo = b""
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if not isinstance(backend, HashBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HashBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE
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)
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self._backend = backend
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self._used = False
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def _hash(self):
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return hashes.Hash(self._algorithm, self._backend)
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def derive(self, key_material):
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(key_material, self._length,
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self._hash, self._otherinfo)
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def verify(self, key_material, expected_key):
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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@utils.register_interface(KeyDerivationFunction)
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class ConcatKDFHMAC(object):
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def __init__(self, algorithm, length, salt, otherinfo, backend):
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo = otherinfo
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if self._otherinfo is None:
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self._otherinfo = b""
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if not (salt is None or isinstance(salt, bytes)):
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raise TypeError("salt must be bytes.")
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if salt is None:
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salt = b"\x00" * algorithm.block_size
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self._salt = salt
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE
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)
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self._backend = backend
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self._used = False
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def _hmac(self):
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return hmac.HMAC(self._salt, self._algorithm, self._backend)
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def derive(self, key_material):
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(key_material, self._length,
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self._hmac, self._otherinfo)
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def verify(self, key_material, expected_key):
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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251
tests/hazmat/primitives/test_concatkdf.py
Normal file
251
tests/hazmat/primitives/test_concatkdf.py
Normal file
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@ -0,0 +1,251 @@
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import absolute_import, division, print_function
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import binascii
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import pytest
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from cryptography.exceptions import (
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AlreadyFinalized, InvalidKey, _Reasons
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)
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from cryptography.hazmat.backends.interfaces import HMACBackend
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from cryptography.hazmat.backends.interfaces import HashBackend
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from cryptography.hazmat.primitives import hashes
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from cryptography.hazmat.primitives.kdf.concatkdf import ConcatKDFHMAC
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from cryptography.hazmat.primitives.kdf.concatkdf import ConcatKDFHash
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from ...utils import raises_unsupported_algorithm
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@pytest.mark.requires_backend_interface(interface=HashBackend)
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class TestConcatKDFHash(object):
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def test_length_limit(self, backend):
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big_length = hashes.SHA256().digest_size * (2 ** 32 - 1) + 1
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with pytest.raises(ValueError):
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ConcatKDFHash(hashes.SHA256(), big_length, None, backend)
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def test_already_finalized(self, backend):
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ckdf = ConcatKDFHash(hashes.SHA256(), 16, None, backend)
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ckdf.derive(b"\x01" * 16)
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with pytest.raises(AlreadyFinalized):
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ckdf.derive(b"\x02" * 16)
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def test_derive(self, backend):
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prk = binascii.unhexlify(
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b"52169af5c485dcc2321eb8d26d5efa21fb9b93c98e38412ee2484cf14f0d0d23"
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)
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okm = binascii.unhexlify(b"1c3bc9e7c4547c5191c0d478cccaed55")
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oinfo = binascii.unhexlify(
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b"a1b2c3d4e53728157e634612c12d6d5223e204aeea4341565369647bd184bcd2"
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b"46f72971f292badaa2fe4124612cba"
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)
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ckdf = ConcatKDFHash(hashes.SHA256(), 16, oinfo, backend)
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assert ckdf.derive(prk) == okm
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def test_verify(self, backend):
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prk = binascii.unhexlify(
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b"52169af5c485dcc2321eb8d26d5efa21fb9b93c98e38412ee2484cf14f0d0d23"
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)
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okm = binascii.unhexlify(b"1c3bc9e7c4547c5191c0d478cccaed55")
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oinfo = binascii.unhexlify(
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b"a1b2c3d4e53728157e634612c12d6d5223e204aeea4341565369647bd184bcd2"
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b"46f72971f292badaa2fe4124612cba"
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)
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ckdf = ConcatKDFHash(hashes.SHA256(), 16, oinfo, backend)
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assert ckdf.verify(prk, okm) is None
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def test_invalid_verify(self, backend):
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prk = binascii.unhexlify(
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b"52169af5c485dcc2321eb8d26d5efa21fb9b93c98e38412ee2484cf14f0d0d23"
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)
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oinfo = binascii.unhexlify(
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b"a1b2c3d4e53728157e634612c12d6d5223e204aeea4341565369647bd184bcd2"
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b"46f72971f292badaa2fe4124612cba"
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)
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ckdf = ConcatKDFHash(hashes.SHA256(), 16, oinfo, backend)
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with pytest.raises(InvalidKey):
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ckdf.verify(prk, b"wrong key")
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def test_unicode_typeerror(self, backend):
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with pytest.raises(TypeError):
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ConcatKDFHash(
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hashes.SHA256(),
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16,
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otherinfo=u"foo",
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backend=backend
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)
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with pytest.raises(TypeError):
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ckdf = ConcatKDFHash(
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hashes.SHA256(),
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16,
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otherinfo=None,
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backend=backend
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)
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ckdf.derive(u"foo")
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with pytest.raises(TypeError):
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ckdf = ConcatKDFHash(
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hashes.SHA256(),
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16,
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otherinfo=None,
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backend=backend
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)
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ckdf.verify(u"foo", b"bar")
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with pytest.raises(TypeError):
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ckdf = ConcatKDFHash(
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hashes.SHA256(),
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16,
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otherinfo=None,
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backend=backend
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)
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ckdf.verify(b"foo", u"bar")
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@pytest.mark.requires_backend_interface(interface=HMACBackend)
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class TestConcatKDFHMAC(object):
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def test_length_limit(self, backend):
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big_length = hashes.SHA256().digest_size * (2 ** 32 - 1) + 1
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with pytest.raises(ValueError):
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ConcatKDFHMAC(hashes.SHA256(), big_length, None, None, backend)
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def test_already_finalized(self, backend):
|
||||
ckdf = ConcatKDFHMAC(hashes.SHA256(), 16, None, None, backend)
|
||||
|
||||
ckdf.derive(b"\x01" * 16)
|
||||
|
||||
with pytest.raises(AlreadyFinalized):
|
||||
ckdf.derive(b"\x02" * 16)
|
||||
|
||||
def test_derive(self, backend):
|
||||
prk = binascii.unhexlify(
|
||||
b"013951627c1dea63ea2d7702dd24e963eef5faac6b4af7e4"
|
||||
b"b831cde499dff1ce45f6179f741c728aa733583b02409208"
|
||||
b"8f0af7fce1d045edbc5790931e8d5ca79c73"
|
||||
)
|
||||
|
||||
okm = binascii.unhexlify(b"64ce901db10d558661f10b6836a122a7"
|
||||
b"605323ce2f39bf27eaaac8b34cf89f2f")
|
||||
|
||||
oinfo = binascii.unhexlify(
|
||||
b"a1b2c3d4e55e600be5f367e0e8a465f4bf2704db00c9325c"
|
||||
b"9fbd216d12b49160b2ae5157650f43415653696421e68e"
|
||||
)
|
||||
|
||||
ckdf = ConcatKDFHMAC(hashes.SHA512(), 32, None, oinfo, backend)
|
||||
|
||||
assert ckdf.derive(prk) == okm
|
||||
|
||||
def test_verify(self, backend):
|
||||
prk = binascii.unhexlify(
|
||||
b"013951627c1dea63ea2d7702dd24e963eef5faac6b4af7e4"
|
||||
b"b831cde499dff1ce45f6179f741c728aa733583b02409208"
|
||||
b"8f0af7fce1d045edbc5790931e8d5ca79c73"
|
||||
)
|
||||
|
||||
okm = binascii.unhexlify(b"64ce901db10d558661f10b6836a122a7"
|
||||
b"605323ce2f39bf27eaaac8b34cf89f2f")
|
||||
|
||||
oinfo = binascii.unhexlify(
|
||||
b"a1b2c3d4e55e600be5f367e0e8a465f4bf2704db00c9325c"
|
||||
b"9fbd216d12b49160b2ae5157650f43415653696421e68e"
|
||||
)
|
||||
|
||||
ckdf = ConcatKDFHMAC(hashes.SHA512(), 32, None, oinfo, backend)
|
||||
|
||||
assert ckdf.verify(prk, okm) is None
|
||||
|
||||
def test_invalid_verify(self, backend):
|
||||
prk = binascii.unhexlify(
|
||||
b"013951627c1dea63ea2d7702dd24e963eef5faac6b4af7e4"
|
||||
b"b831cde499dff1ce45f6179f741c728aa733583b02409208"
|
||||
b"8f0af7fce1d045edbc5790931e8d5ca79c73"
|
||||
)
|
||||
|
||||
oinfo = binascii.unhexlify(
|
||||
b"a1b2c3d4e55e600be5f367e0e8a465f4bf2704db00c9325c"
|
||||
b"9fbd216d12b49160b2ae5157650f43415653696421e68e"
|
||||
)
|
||||
|
||||
ckdf = ConcatKDFHMAC(hashes.SHA512(), 32, None, oinfo, backend)
|
||||
|
||||
with pytest.raises(InvalidKey):
|
||||
ckdf.verify(prk, b"wrong key")
|
||||
|
||||
def test_unicode_typeerror(self, backend):
|
||||
with pytest.raises(TypeError):
|
||||
ConcatKDFHMAC(
|
||||
hashes.SHA256(),
|
||||
16, salt=u"foo",
|
||||
otherinfo=None,
|
||||
backend=backend
|
||||
)
|
||||
|
||||
with pytest.raises(TypeError):
|
||||
ConcatKDFHMAC(
|
||||
hashes.SHA256(),
|
||||
16, salt=None,
|
||||
otherinfo=u"foo",
|
||||
backend=backend
|
||||
)
|
||||
|
||||
with pytest.raises(TypeError):
|
||||
ckdf = ConcatKDFHMAC(
|
||||
hashes.SHA256(),
|
||||
16, salt=None,
|
||||
otherinfo=None,
|
||||
backend=backend
|
||||
)
|
||||
|
||||
ckdf.derive(u"foo")
|
||||
|
||||
with pytest.raises(TypeError):
|
||||
ckdf = ConcatKDFHMAC(
|
||||
hashes.SHA256(),
|
||||
16, salt=None,
|
||||
otherinfo=None,
|
||||
backend=backend
|
||||
)
|
||||
|
||||
ckdf.verify(u"foo", b"bar")
|
||||
|
||||
with pytest.raises(TypeError):
|
||||
ckdf = ConcatKDFHMAC(
|
||||
hashes.SHA256(),
|
||||
16, salt=None,
|
||||
otherinfo=None,
|
||||
backend=backend
|
||||
)
|
||||
|
||||
ckdf.verify(b"foo", u"bar")
|
||||
|
||||
|
||||
def test_invalid_backend():
|
||||
pretend_backend = object()
|
||||
|
||||
with raises_unsupported_algorithm(_Reasons.BACKEND_MISSING_INTERFACE):
|
||||
ConcatKDFHash(hashes.SHA256(), 16, None, pretend_backend)
|
||||
with raises_unsupported_algorithm(_Reasons.BACKEND_MISSING_INTERFACE):
|
||||
ConcatKDFHMAC(hashes.SHA256(), 16, None, None, pretend_backend)
|
||||
Loading…
Reference in a new issue