File size: 5,949 Bytes
0a06673 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 |
# ===================================================================
#
# Copyright (c) 2021, Legrandin <[email protected]>
# 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)
|