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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 Crypto.Util.py3compat import bchr
from Crypto.Util._raw_api import (VoidPointer, SmartPointer,
create_string_buffer,
get_raw_buffer, c_size_t,
c_uint8_ptr, c_ubyte)
from Crypto.Util.number import long_to_bytes
from Crypto.Hash.keccak import _raw_keccak_lib
def _left_encode(x):
"""Left encode function as defined in NIST SP 800-185"""
assert (x < (1 << 2040) and x >= 0)
# Get number of bytes needed to represent this integer.
num = 1 if x == 0 else (x.bit_length() + 7) // 8
return bchr(num) + long_to_bytes(x)
def _right_encode(x):
"""Right encode function as defined in NIST SP 800-185"""
assert (x < (1 << 2040) and x >= 0)
# Get number of bytes needed to represent this integer.
num = 1 if x == 0 else (x.bit_length() + 7) // 8
return long_to_bytes(x) + bchr(num)
def _encode_str(x):
"""Encode string function as defined in NIST SP 800-185"""
bitlen = len(x) * 8
if bitlen >= (1 << 2040):
raise ValueError("String too large to encode in cSHAKE")
return _left_encode(bitlen) + x
def _bytepad(x, length):
"""Zero pad byte string as defined in NIST SP 800-185"""
to_pad = _left_encode(length) + x
# Note: this implementation works with byte aligned strings,
# hence no additional bit padding is needed at this point.
npad = (length - len(to_pad) % length) % length
return to_pad + b'\x00' * npad
class cSHAKE_XOF(object):
"""A cSHAKE hash object.
Do not instantiate directly.
Use the :func:`new` function.
"""
def __init__(self, data, custom, capacity, function):
state = VoidPointer()
if custom or function:
prefix_unpad = _encode_str(function) + _encode_str(custom)
prefix = _bytepad(prefix_unpad, (1600 - capacity)//8)
self._padding = 0x04
else:
prefix = None
self._padding = 0x1F # for SHAKE
result = _raw_keccak_lib.keccak_init(state.address_of(),
c_size_t(capacity//8),
c_ubyte(24))
if result:
raise ValueError("Error %d while instantiating cSHAKE"
% result)
self._state = SmartPointer(state.get(),
_raw_keccak_lib.keccak_destroy)
self._is_squeezing = False
if prefix:
self.update(prefix)
if data:
self.update(data)
def update(self, data):
"""Continue hashing of a message by consuming the next chunk of data.
Args:
data (byte string/byte array/memoryview): The next chunk of the message being hashed.
"""
if self._is_squeezing:
raise TypeError("You cannot call 'update' after the first 'read'")
result = _raw_keccak_lib.keccak_absorb(self._state.get(),
c_uint8_ptr(data),
c_size_t(len(data)))
if result:
raise ValueError("Error %d while updating %s state"
% (result, self.name))
return self
def read(self, length):
"""
Compute the next piece of XOF output.
.. note::
You cannot use :meth:`update` anymore after the first call to
:meth:`read`.
Args:
length (integer): the amount of bytes this method must return
:return: the next piece of XOF output (of the given length)
:rtype: byte string
"""
self._is_squeezing = True
bfr = create_string_buffer(length)
result = _raw_keccak_lib.keccak_squeeze(self._state.get(),
bfr,
c_size_t(length),
c_ubyte(self._padding))
if result:
raise ValueError("Error %d while extracting from %s"
% (result, self.name))
return get_raw_buffer(bfr)
def _new(data, custom, function):
# Use Keccak[256]
return cSHAKE_XOF(data, custom, 256, function)
def new(data=None, custom=None):
"""Return a fresh instance of a cSHAKE128 object.
Args:
data (bytes/bytearray/memoryview):
Optional.
The very first chunk of the message to hash.
It is equivalent to an early call to :meth:`update`.
custom (bytes):
Optional.
A customization bytestring (``S`` in SP 800-185).
:Return: A :class:`cSHAKE_XOF` object
"""
# Use Keccak[256]
return cSHAKE_XOF(data, custom, 256, b'')
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