# ===================================================================
#
# Copyright (c) 2021, Legrandin <[email protected]>
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# are met:
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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from Cryptodome.Util._raw_api import (VoidPointer, SmartPointer,
create_string_buffer,
get_raw_buffer, c_size_t,
c_uint8_ptr, c_ubyte)
from Cryptodome.Util.number import long_to_bytes
from Cryptodome.Util.py3compat import bchr
from .keccak import _raw_keccak_lib
def _length_encode(x):
if x == 0:
return b'\x00'
S = long_to_bytes(x)
return S + bchr(len(S))
# Possible states for a KangarooTwelve instance, which depend on the amount of data processed so far.
SHORT_MSG = 1 # Still within the first 8192 bytes, but it is not certain we will exceed them.
LONG_MSG_S0 = 2 # Still within the first 8192 bytes, and it is certain we will exceed them.
LONG_MSG_SX = 3 # Beyond the first 8192 bytes.
SQUEEZING = 4 # No more data to process.
class K12_XOF(object):
"""A KangarooTwelve hash object.
Do not instantiate directly.
Use the :func:`new` function.
"""
def __init__(self, data, custom):
if custom == None:
custom = b''
self._custom = custom + _length_encode(len(custom))
self._state = SHORT_MSG
self._padding = None # Final padding is only decided in read()
# Internal hash that consumes FinalNode
self._hash1 = self._create_keccak()
self._length1 = 0
# Internal hash that produces CV_i (reset each time)
self._hash2 = None
self._length2 = 0
# Incremented by one for each 8192-byte block
self._ctr = 0
if data:
self.update(data)
def _create_keccak(self):
state = VoidPointer()
result = _raw_keccak_lib.keccak_init(state.address_of(),
c_size_t(32), # 32 bytes of capacity (256 bits)
c_ubyte(12)) # Reduced number of rounds
if result:
raise ValueError("Error %d while instantiating KangarooTwelve"
% result)
return SmartPointer(state.get(), _raw_keccak_lib.keccak_destroy)
def _update(self, data, hash_obj):
result = _raw_keccak_lib.keccak_absorb(hash_obj.get(),
c_uint8_ptr(data),
c_size_t(len(data)))
if result:
raise ValueError("Error %d while updating KangarooTwelve state"
% result)
def _squeeze(self, hash_obj, length, padding):
bfr = create_string_buffer(length)
result = _raw_keccak_lib.keccak_squeeze(hash_obj.get(),
bfr,
c_size_t(length),
c_ubyte(padding))
if result:
raise ValueError("Error %d while extracting from KangarooTwelve"
% result)
return get_raw_buffer(bfr)
def _reset(self, hash_obj):
result = _raw_keccak_lib.keccak_reset(hash_obj.get())
if result:
raise ValueError("Error %d while resetting KangarooTwelve state"
% result)
def update(self, data):
"""Hash the next piece of data.
.. note::
For better performance, submit chunks with a length multiple of 8192 bytes.
Args:
data (byte string/byte array/memoryview): The next chunk of the
message to hash.
"""
if self._state == SQUEEZING:
raise TypeError("You cannot call 'update' after the first 'read'")
if self._state == SHORT_MSG:
next_length = self._length1 + len(data)
if next_length + len(self._custom) <= 8192:
self._length1 = next_length
self._update(data, self._hash1)
return self
# Switch to tree hashing
self._state = LONG_MSG_S0
if self._state == LONG_MSG_S0:
data_mem = memoryview(data)
assert(self._length1 < 8192)
dtc = min(len(data), 8192 - self._length1)
self._update(data_mem[:dtc], self._hash1)
self._length1 += dtc
if self._length1 < 8192:
return self
# Finish hashing S_0 and start S_1
assert(self._length1 == 8192)
divider = b'\x03' + b'\x00' * 7
self._update(divider, self._hash1)
self._length1 += 8
self._hash2 = self._create_keccak()
self._length2 = 0
self._ctr = 1
self._state = LONG_MSG_SX
return self.update(data_mem[dtc:])
# LONG_MSG_SX
assert(self._state == LONG_MSG_SX)
index = 0
len_data = len(data)
# All iteractions could actually run in parallel
data_mem = memoryview(data)
while index < len_data:
new_index = min(index + 8192 - self._length2, len_data)
self._update(data_mem[index:new_index], self._hash2)
self._length2 += new_index - index
index = new_index
if self._length2 == 8192:
cv_i = self._squeeze(self._hash2, 32, 0x0B)
self._update(cv_i, self._hash1)
self._length1 += 32
self._reset(self._hash2)
self._length2 = 0
self._ctr += 1
return self
def read(self, length):
"""
Produce more bytes of the digest.
.. 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
"""
custom_was_consumed = False
if self._state == SHORT_MSG:
self._update(self._custom, self._hash1)
self._padding = 0x07
self._state = SQUEEZING
if self._state == LONG_MSG_S0:
self.update(self._custom)
custom_was_consumed = True
assert(self._state == LONG_MSG_SX)
if self._state == LONG_MSG_SX:
if not custom_was_consumed:
self.update(self._custom)
# Is there still some leftover data in hash2?
if self._length2 > 0:
cv_i = self._squeeze(self._hash2, 32, 0x0B)
self._update(cv_i, self._hash1)
self._length1 += 32
self._reset(self._hash2)
self._length2 = 0
self._ctr += 1
trailer = _length_encode(self._ctr - 1) + b'\xFF\xFF'
self._update(trailer, self._hash1)
self._padding = 0x06
self._state = SQUEEZING
return self._squeeze(self._hash1, length, self._padding)
def new(self, data=None, custom=b''):
return type(self)(data, custom)
def new(data=None, custom=None):
"""Return a fresh instance of a KangarooTwelve 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 byte string.
:Return: A :class:`K12_XOF` object
"""
return K12_XOF(data, custom)