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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, concat_buffers
- 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 concat_buffers(_left_encode(bitlen), x)
- def _bytepad(x, length):
- """Zero pad byte string as defined in NIST SP 800-185"""
- to_pad = concat_buffers(_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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