145 lines
5.2 KiB
Python
145 lines
5.2 KiB
Python
# ===================================================================
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#
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# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in
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# the documentation and/or other materials provided with the
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# distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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# ===================================================================
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"""Fast, arbitrary precision integers.
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:undocumented: __package__
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"""
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__all__ = ["Integer"]
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from Crypto.Util.py3compat import *
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from Crypto import Random
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try:
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from Crypto.Math._Numbers_gmp import Integer
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from Crypto.Math._Numbers_gmp import implementation as _implementation
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except (ImportError, OSError):
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from Crypto.Math._Numbers_int import Integer
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_implementation = { }
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def _random(**kwargs):
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"""Generate a random natural integer of a certain size.
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:Keywords:
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exact_bits : positive integer
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The length in bits of the resulting random Integer number.
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The number is guaranteed to fulfil the relation:
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2^bits > result >= 2^(bits - 1)
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max_bits : positive integer
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The maximum length in bits of the resulting random Integer number.
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The number is guaranteed to fulfil the relation:
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2^bits > result >=0
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randfunc : callable
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A function that returns a random byte string. The length of the
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byte string is passed as parameter. Optional.
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If not provided (or ``None``), randomness is read from the system RNG.
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:Return: a Integer object
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"""
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exact_bits = kwargs.pop("exact_bits", None)
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max_bits = kwargs.pop("max_bits", None)
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randfunc = kwargs.pop("randfunc", None)
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if randfunc is None:
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randfunc = Random.new().read
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if exact_bits is None and max_bits is None:
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raise ValueError("Either 'exact_bits' or 'max_bits' must be specified")
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if exact_bits is not None and max_bits is not None:
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raise ValueError("'exact_bits' and 'max_bits' are mutually exclusive")
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bits = exact_bits or max_bits
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bytes_needed = ((bits - 1) // 8) + 1
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significant_bits_msb = 8 - (bytes_needed * 8 - bits)
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msb = bord(randfunc(1)[0])
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if exact_bits is not None:
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msb |= 1 << (significant_bits_msb - 1)
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msb &= (1 << significant_bits_msb) - 1
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return Integer.from_bytes(bchr(msb) + randfunc(bytes_needed - 1))
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def _random_range(**kwargs):
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"""Generate a random integer within a given internal.
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:Keywords:
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min_inclusive : integer
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The lower end of the interval (inclusive).
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max_inclusive : integer
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The higher end of the interval (inclusive).
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max_exclusive : integer
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The higher end of the interval (exclusive).
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randfunc : callable
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A function that returns a random byte string. The length of the
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byte string is passed as parameter. Optional.
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If not provided (or ``None``), randomness is read from the system RNG.
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:Returns:
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An Integer randomly taken in the given interval.
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"""
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min_inclusive = kwargs.pop("min_inclusive", None)
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max_inclusive = kwargs.pop("max_inclusive", None)
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max_exclusive = kwargs.pop("max_exclusive", None)
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randfunc = kwargs.pop("randfunc", None)
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if kwargs:
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raise ValueError("Unknown keywords: " + str(kwargs.keys))
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if None not in (max_inclusive, max_exclusive):
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raise ValueError("max_inclusive and max_exclusive cannot be both"
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" specified")
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if max_exclusive is not None:
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max_inclusive = max_exclusive - 1
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if None in (min_inclusive, max_inclusive):
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raise ValueError("Missing keyword to identify the interval")
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if randfunc is None:
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randfunc = Random.new().read
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norm_maximum = max_inclusive - min_inclusive
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bits_needed = Integer(norm_maximum).size_in_bits()
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norm_candidate = -1
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while not 0 <= norm_candidate <= norm_maximum:
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norm_candidate = _random(
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max_bits=bits_needed,
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randfunc=randfunc
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)
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return norm_candidate + min_inclusive
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Integer.random = staticmethod(_random)
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Integer.random_range = staticmethod(_random_range)
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