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https://github.com/ansible-collections/community.crypto.git
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0ef6494ad2
* Fix quick_is_not_prime() for small primes. Add some tests.
* Fix return value of convert_int_to_bytes(0, 0) on Python 2.
* Add some more test cases.
* Simplify the changelog and point out that these errors only happen for cases not happening in regular use.
(cherry picked from commit 0c62837296)
91 lines
2.8 KiB
Python
91 lines
2.8 KiB
Python
# -*- coding: utf-8 -*-
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#
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# (c) 2019, Felix Fontein <felix@fontein.de>
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#
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# Ansible is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# Ansible is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with Ansible. If not, see <http://www.gnu.org/licenses/>.
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from __future__ import absolute_import, division, print_function
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__metaclass__ = type
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import sys
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def binary_exp_mod(f, e, m):
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'''Computes f^e mod m in O(log e) multiplications modulo m.'''
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# Compute len_e = floor(log_2(e))
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len_e = -1
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x = e
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while x > 0:
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x >>= 1
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len_e += 1
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# Compute f**e mod m
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result = 1
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for k in range(len_e, -1, -1):
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result = (result * result) % m
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if ((e >> k) & 1) != 0:
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result = (result * f) % m
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return result
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def simple_gcd(a, b):
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'''Compute GCD of its two inputs.'''
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while b != 0:
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a, b = b, a % b
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return a
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def quick_is_not_prime(n):
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'''Does some quick checks to see if we can poke a hole into the primality of n.
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A result of `False` does **not** mean that the number is prime; it just means
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that we couldn't detect quickly whether it is not prime.
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'''
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if n <= 2:
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return n < 2
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# The constant in the next line is the product of all primes < 200
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prime_product = 7799922041683461553249199106329813876687996789903550945093032474868511536164700810
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gcd = simple_gcd(n, prime_product)
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if gcd > 1:
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if n < 200 and gcd == n:
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# Explicitly check for all primes < 200
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return n not in (
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2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83,
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89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179,
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181, 191, 193, 197, 199,
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)
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return True
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# TODO: maybe do some iterations of Miller-Rabin to increase confidence
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# (https://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test)
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return False
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python_version = (sys.version_info[0], sys.version_info[1])
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if python_version >= (2, 7) or python_version >= (3, 1):
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# Ansible still supports Python 2.6 on remote nodes
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def count_bits(no):
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no = abs(no)
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if no == 0:
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return 0
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return no.bit_length()
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else:
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# Slow, but works
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def count_bits(no):
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no = abs(no)
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count = 0
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while no > 0:
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no >>= 1
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count += 1
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return count
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