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strxor.py
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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 Crypto.Util._raw_api import (load_pycryptodome_raw_lib, c_size_t, create_string_buffer, get_raw_buffer, c_uint8_ptr, is_writeable_buffer) _raw_strxor = load_pycryptodome_raw_lib( "Crypto.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, output=None): """From two byte strings of equal length, create a third one which is the byte-by-byte XOR of the two. Args: term1 (bytes/bytearray/memoryview): The first byte string to XOR. term2 (bytes/bytearray/memoryview): The second byte string to XOR. output (bytearray/memoryview): The location where the result will be written to. It must have the same length as ``term1`` and ``term2``. If ``None``, the result is returned. :Return: If ``output`` is ``None``, a new byte string with the result. Otherwise ``None``. .. note:: ``term1`` and ``term2`` must have the same length. """ if len(term1) != len(term2): raise ValueError("Only byte strings of equal length can be xored") if output is None: result = create_string_buffer(len(term1)) else: # Note: output may overlap with either input result = output if not is_writeable_buffer(output): raise TypeError("output must be a bytearray or a writeable memoryview") if len(term1) != len(output): raise ValueError("output must have the same length as the input" " (%d bytes)" % len(term1)) _raw_strxor.strxor(c_uint8_ptr(term1), c_uint8_ptr(term2), c_uint8_ptr(result), c_size_t(len(term1))) if output is None: return get_raw_buffer(result) else: return None def strxor_c(term, c, output=None): """From a byte string, create a second one of equal length where each byte is XOR-red with the same value. Args: term(bytes/bytearray/memoryview): The byte string to XOR. c (int): Every byte in the string will be XOR-ed with this value. It must be between 0 and 255 (included). output (None or bytearray/memoryview): The location where the result will be written to. It must have the same length as ``term``. If ``None``, the result is returned. Return: If ``output`` is ``None``, a new ``bytes`` string with the result. Otherwise ``None``. """ if not 0 <= c < 256: raise ValueError("c must be in range(256)") if output is None: result = create_string_buffer(len(term)) else: # Note: output may overlap with either input result = output if not is_writeable_buffer(output): raise TypeError("output must be a bytearray or a writeable memoryview") if len(term) != len(output): raise ValueError("output must have the same length as the input" " (%d bytes)" % len(term)) _raw_strxor.strxor_c(c_uint8_ptr(term), c, c_uint8_ptr(result), c_size_t(len(term)) ) if output is None: return get_raw_buffer(result) else: return None def _strxor_direct(term1, term2, result): """Very fast XOR - check conditions!""" _raw_strxor.strxor(term1, term2, result, c_size_t(len(term1)))