diff options
Diffstat (limited to 'rsa/transform.py')
| -rw-r--r-- | rsa/transform.py | 167 |
1 files changed, 12 insertions, 155 deletions
diff --git a/rsa/transform.py b/rsa/transform.py index 628d0af..03c4a77 100644 --- a/rsa/transform.py +++ b/rsa/transform.py @@ -1,5 +1,3 @@ -# -*- coding: utf-8 -*- -# # Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu> # # Licensed under the Apache License, Version 2.0 (the "License"); @@ -19,16 +17,10 @@ From bytes to a number, number to bytes, etc. """ -from __future__ import absolute_import - -import binascii -from struct import pack +import math -from rsa._compat import byte, is_integer -from rsa import common, machine_size - -def bytes2int(raw_bytes): +def bytes2int(raw_bytes: bytes) -> int: r"""Converts a list of bytes or an 8-bit string to an integer. When using unicode strings, encode it to some encoding like UTF8 first. @@ -39,110 +31,14 @@ def bytes2int(raw_bytes): 8405007 """ + return int.from_bytes(raw_bytes, 'big', signed=False) - return int(binascii.hexlify(raw_bytes), 16) - - -def _int2bytes(number, block_size=None): - r"""Converts a number to a string of bytes. - - Usage:: - - >>> _int2bytes(123456789) - b'\x07[\xcd\x15' - >>> bytes2int(_int2bytes(123456789)) - 123456789 - - >>> _int2bytes(123456789, 6) - b'\x00\x00\x07[\xcd\x15' - >>> bytes2int(_int2bytes(123456789, 128)) - 123456789 - - >>> _int2bytes(123456789, 3) - Traceback (most recent call last): - ... - OverflowError: Needed 4 bytes for number, but block size is 3 - - @param number: the number to convert - @param block_size: the number of bytes to output. If the number encoded to - bytes is less than this, the block will be zero-padded. When not given, - the returned block is not padded. - - @throws OverflowError when block_size is given and the number takes up more - bytes than fit into the block. - """ - - # Type checking - if not is_integer(number): - raise TypeError("You must pass an integer for 'number', not %s" % - number.__class__) - - if number < 0: - raise ValueError('Negative numbers cannot be used: %i' % number) - - # Do some bounds checking - if number == 0: - needed_bytes = 1 - raw_bytes = [b'\x00'] - else: - needed_bytes = common.byte_size(number) - raw_bytes = [] - - # You cannot compare None > 0 in Python 3x. It will fail with a TypeError. - if block_size and block_size > 0: - if needed_bytes > block_size: - raise OverflowError('Needed %i bytes for number, but block size ' - 'is %i' % (needed_bytes, block_size)) - - # Convert the number to bytes. - while number > 0: - raw_bytes.insert(0, byte(number & 0xFF)) - number >>= 8 - - # Pad with zeroes to fill the block - if block_size and block_size > 0: - padding = (block_size - needed_bytes) * b'\x00' - else: - padding = b'' - - return padding + b''.join(raw_bytes) - - -def bytes_leading(raw_bytes, needle=b'\x00'): - """ - Finds the number of prefixed byte occurrences in the haystack. - - Useful when you want to deal with padding. - :param raw_bytes: - Raw bytes. - :param needle: - The byte to count. Default \x00. - :returns: - The number of leading needle bytes. - """ - - leading = 0 - # Indexing keeps compatibility between Python 2.x and Python 3.x - _byte = needle[0] - for x in raw_bytes: - if x == _byte: - leading += 1 - else: - break - return leading - - -def int2bytes(number, fill_size=None, chunk_size=None, overflow=False): +def int2bytes(number: int, fill_size: int = 0) -> bytes: """ - Convert an unsigned integer to bytes (base-256 representation):: - - Does not preserve leading zeros if you don't specify a chunk size or - fill size. + Convert an unsigned integer to bytes (big-endian):: - .. NOTE: - You must not specify both fill_size and chunk_size. Only one - of them is allowed. + Does not preserve leading zeros if you don't specify a fill size. :param number: Integer value @@ -150,15 +46,6 @@ def int2bytes(number, fill_size=None, chunk_size=None, overflow=False): If the optional fill size is given the length of the resulting byte string is expected to be the fill size and will be padded with prefix zero bytes to satisfy that length. - :param chunk_size: - If optional chunk size is given and greater than zero, pad the front of - the byte string with binary zeros so that the length is a multiple of - ``chunk_size``. - :param overflow: - ``False`` (default). If this is ``True``, no ``OverflowError`` - will be raised when the fill_size is shorter than the length - of the generated byte sequence. Instead the byte sequence will - be returned as is. :returns: Raw bytes (base-256 representation). :raises: @@ -171,42 +58,12 @@ def int2bytes(number, fill_size=None, chunk_size=None, overflow=False): if number < 0: raise ValueError("Number must be an unsigned integer: %d" % number) - if fill_size and chunk_size: - raise ValueError("You can either fill or pad chunks, but not both") - - # Ensure these are integers. - number & 1 - - raw_bytes = b'' - - # Pack the integer one machine word at a time into bytes. - num = number - word_bits, _, max_uint, pack_type = machine_size.get_word_alignment(num) - pack_format = ">%s" % pack_type - while num > 0: - raw_bytes = pack(pack_format, num & max_uint) + raw_bytes - num >>= word_bits - # Obtain the index of the first non-zero byte. - zero_leading = bytes_leading(raw_bytes) - if number == 0: - raw_bytes = b'\x00' - # De-padding. - raw_bytes = raw_bytes[zero_leading:] - - length = len(raw_bytes) - if fill_size and fill_size > 0: - if not overflow and length > fill_size: - raise OverflowError( - "Need %d bytes for number, but fill size is %d" % - (length, fill_size) - ) - raw_bytes = raw_bytes.rjust(fill_size, b'\x00') - elif chunk_size and chunk_size > 0: - remainder = length % chunk_size - if remainder: - padding_size = chunk_size - remainder - raw_bytes = raw_bytes.rjust(length + padding_size, b'\x00') - return raw_bytes + bytes_required = max(1, math.ceil(number.bit_length() / 8)) + + if fill_size > 0: + return number.to_bytes(fill_size, 'big') + + return number.to_bytes(bytes_required, 'big') if __name__ == '__main__': |