1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
|
## rndg.py
##
## cryptographically secure pseudo-random number generator.
## When possible use OpenSSL PRNG combined with os.random,
## if OpenSSL PRNG is not available, use only os.random.
##
## Copyright (C) 2013 Fedor Brunner <fedor.brunner@azet.sk>
##
## This file is part of Gajim.
##
## Gajim is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published
## by the Free Software Foundation; version 3 only.
##
## Gajim is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Gajim. If not, see <http://www.gnu.org/licenses/>.
USE_PYOPENSSL = False
try:
import OpenSSL.rand
import binascii, os
USE_PYOPENSSL = True
except ImportError:
import random
if not USE_PYOPENSSL:
getrandbits = random.SystemRandom().getrandbits
else:
def getrandbits(k):
"""getrandbits(k) -> x. Generates a long int with k random bits."""
if k <= 0:
raise ValueError('number of bits must be greater than zero')
if k != int(k):
raise TypeError('number of bits should be an integer')
bytes = (k + 7) // 8 # bits / 8 and rounded up
# Add system entropy to OpenSSL PRNG
OpenSSL.rand.add(os.urandom(bytes), bytes)
# Extract random bytes from OpenSSL PRNG
random_str = OpenSSL.rand.bytes(bytes)
x = int(binascii.hexlify(random_str), 16)
return x >> (bytes * 8 - k) # trim excess bits
|
