/usr/lib/python3/dist-packages/Cryptodome/Util/strxor.py is in python3-pycryptodome 3.4.7-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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#
# Copyright (c) 2014, 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 Cryptodome.Util._raw_api import (load_pycryptodome_raw_lib, c_size_t,
create_string_buffer, get_raw_buffer,
expect_byte_string)
_raw_strxor = load_pycryptodome_raw_lib("Cryptodome.Util._strxor",
"""
void strxor(const uint8_t *in1,
const uint8_t *in2,
uint8_t *out, size_t len);
void strxor_c(const uint8_t *in,
uint8_t c,
uint8_t *out,
size_t len);
""")
def strxor(term1, term2):
"""XOR of two byte strings.
They must have equal length.
Return:
A new byte string, :data:`term1` xored with :data:`term2`.
"""
expect_byte_string(term1)
expect_byte_string(term2)
if len(term1) != len(term2):
raise ValueError("Only byte strings of equal length can be xored")
result = create_string_buffer(len(term1))
_raw_strxor.strxor(term1, term2, result, c_size_t(len(term1)))
return get_raw_buffer(result)
def strxor_c(term, c):
"""XOR of a byte string with a repeated sequence of characters.
Return:
A new byte string, :data:`term` with all its bytes xored with :data:`c`.
"""
expect_byte_string(term)
if not 0 <= c < 256:
raise ValueError("c must be in range(256)")
result = create_string_buffer(len(term))
_raw_strxor.strxor_c(term, c, result, c_size_t(len(term)))
return get_raw_buffer(result)
def _strxor_direct(term1, term2, result):
"""Very fast XOR - check conditions!"""
_raw_strxor.strxor(term1, term2, result, c_size_t(len(term1)))
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