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- # ===================================================================
- #
- # Copyright (c) 2021, Legrandin <helderijs@gmail.com>
- # All rights reserved.
- #
- # Redistribution and use in source and binary forms, with or without
- # modification, are permitted provided that the following conditions
- # are met:
- #
- # 1. Redistributions of source code must retain the above copyright
- # notice, this list of conditions and the following disclaimer.
- # 2. Redistributions in binary form must reproduce the above copyright
- # notice, this list of conditions and the following disclaimer in
- # the documentation and/or other materials provided with the
- # distribution.
- #
- # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- # POSSIBILITY OF SUCH DAMAGE.
- # ===================================================================
- from binascii import unhexlify
- from Crypto.Util.py3compat import bord, tobytes, is_bytes
- from Crypto.Random import get_random_bytes
- from . import cSHAKE128, SHA3_256
- from .cSHAKE128 import _bytepad, _encode_str, _right_encode
- class KMAC_Hash(object):
- """A KMAC hash object.
- Do not instantiate directly.
- Use the :func:`new` function.
- """
- def __init__(self, data, key, mac_len, custom,
- oid_variant, cshake, rate):
- # See https://tools.ietf.org/html/rfc8702
- self.oid = "2.16.840.1.101.3.4.2." + oid_variant
- self.digest_size = mac_len
- self._mac = None
- partial_newX = _bytepad(_encode_str(tobytes(key)), rate)
- self._cshake = cshake._new(partial_newX, custom, b"KMAC")
- if data:
- self._cshake.update(data)
- def update(self, data):
- """Authenticate the next chunk of message.
- Args:
- data (bytes/bytearray/memoryview): The next chunk of the message to
- authenticate.
- """
- if self._mac:
- raise TypeError("You can only call 'digest' or 'hexdigest' on this object")
- self._cshake.update(data)
- return self
- def digest(self):
- """Return the **binary** (non-printable) MAC tag of the message.
- :return: The MAC tag. Binary form.
- :rtype: byte string
- """
- if not self._mac:
- self._cshake.update(_right_encode(self.digest_size * 8))
- self._mac = self._cshake.read(self.digest_size)
- return self._mac
- def hexdigest(self):
- """Return the **printable** MAC tag of the message.
- :return: The MAC tag. Hexadecimal encoded.
- :rtype: string
- """
- return "".join(["%02x" % bord(x) for x in tuple(self.digest())])
- def verify(self, mac_tag):
- """Verify that a given **binary** MAC (computed by another party)
- is valid.
- Args:
- mac_tag (bytes/bytearray/memoryview): the expected MAC of the message.
- Raises:
- ValueError: if the MAC does not match. It means that the message
- has been tampered with or that the MAC key is incorrect.
- """
- secret = get_random_bytes(16)
- mac1 = SHA3_256.new(secret + mac_tag)
- mac2 = SHA3_256.new(secret + self.digest())
- if mac1.digest() != mac2.digest():
- raise ValueError("MAC check failed")
- def hexverify(self, hex_mac_tag):
- """Verify that a given **printable** MAC (computed by another party)
- is valid.
- Args:
- hex_mac_tag (string): the expected MAC of the message, as a hexadecimal string.
- Raises:
- ValueError: if the MAC does not match. It means that the message
- has been tampered with or that the MAC key is incorrect.
- """
- self.verify(unhexlify(tobytes(hex_mac_tag)))
- def new(self, **kwargs):
- """Return a new instance of a KMAC hash object.
- See :func:`new`.
- """
- if "mac_len" not in kwargs:
- kwargs["mac_len"] = self.digest_size
- return new(**kwargs)
- def new(**kwargs):
- """Create a new KMAC128 object.
- Args:
- key (bytes/bytearray/memoryview):
- The key to use to compute the MAC.
- It must be at least 128 bits long (16 bytes).
- data (bytes/bytearray/memoryview):
- Optional. The very first chunk of the message to authenticate.
- It is equivalent to an early call to :meth:`KMAC_Hash.update`.
- mac_len (integer):
- Optional. The size of the authentication tag, in bytes.
- Default is 64. Minimum is 8.
- custom (bytes/bytearray/memoryview):
- Optional. A customization byte string (``S`` in SP 800-185).
- Returns:
- A :class:`KMAC_Hash` hash object
- """
- key = kwargs.pop("key", None)
- if not is_bytes(key):
- raise TypeError("You must pass a key to KMAC128")
- if len(key) < 16:
- raise ValueError("The key must be at least 128 bits long (16 bytes)")
- data = kwargs.pop("data", None)
- mac_len = kwargs.pop("mac_len", 64)
- if mac_len < 8:
- raise ValueError("'mac_len' must be 8 bytes or more")
- custom = kwargs.pop("custom", b"")
- if kwargs:
- raise TypeError("Unknown parameters: " + str(kwargs))
- return KMAC_Hash(data, key, mac_len, custom, "19", cSHAKE128, 168)
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