Current File : //lib/python3.6/site-packages/dns/entropy.py
# Copyright (C) 2009, 2011 Nominum, Inc.
#
# Permission to use, copy, modify, and distribute this software and its
# documentation for any purpose with or without fee is hereby granted,
# provided that the above copyright notice and this permission notice
# appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
import os
import random
import time
from ._compat import long, binary_type
try:
import threading as _threading
except ImportError:
import dummy_threading as _threading
class EntropyPool(object):
def __init__(self, seed=None):
self.pool_index = 0
self.digest = None
self.next_byte = 0
self.lock = _threading.Lock()
try:
import hashlib
self.hash = hashlib.sha1()
self.hash_len = 20
except ImportError:
try:
import sha
self.hash = sha.new()
self.hash_len = 20
except ImportError:
import md5 # pylint: disable=import-error
self.hash = md5.new()
self.hash_len = 16
self.pool = bytearray(b'\0' * self.hash_len)
if seed is not None:
self.stir(bytearray(seed))
self.seeded = True
self.seed_pid = os.getpid()
else:
self.seeded = False
self.seed_pid = 0
def stir(self, entropy, already_locked=False):
if not already_locked:
self.lock.acquire()
try:
for c in entropy:
if self.pool_index == self.hash_len:
self.pool_index = 0
b = c & 0xff
self.pool[self.pool_index] ^= b
self.pool_index += 1
finally:
if not already_locked:
self.lock.release()
def _maybe_seed(self):
if not self.seeded or self.seed_pid != os.getpid():
try:
seed = os.urandom(16)
except Exception:
try:
r = open('/dev/urandom', 'rb', 0)
try:
seed = r.read(16)
finally:
r.close()
except Exception:
seed = str(time.time())
self.seeded = True
self.seed_pid = os.getpid()
self.digest = None
seed = bytearray(seed)
self.stir(seed, True)
def random_8(self):
self.lock.acquire()
try:
self._maybe_seed()
if self.digest is None or self.next_byte == self.hash_len:
self.hash.update(binary_type(self.pool))
self.digest = bytearray(self.hash.digest())
self.stir(self.digest, True)
self.next_byte = 0
value = self.digest[self.next_byte]
self.next_byte += 1
finally:
self.lock.release()
return value
def random_16(self):
return self.random_8() * 256 + self.random_8()
def random_32(self):
return self.random_16() * 65536 + self.random_16()
def random_between(self, first, last):
size = last - first + 1
if size > long(4294967296):
raise ValueError('too big')
if size > 65536:
rand = self.random_32
max = long(4294967295)
elif size > 256:
rand = self.random_16
max = 65535
else:
rand = self.random_8
max = 255
return first + size * rand() // (max + 1)
pool = EntropyPool()
try:
system_random = random.SystemRandom()
except Exception:
system_random = None
def random_16():
if system_random is not None:
return system_random.randrange(0, 65536)
else:
return pool.random_16()
def between(first, last):
if system_random is not None:
return system_random.randrange(first, last + 1)
else:
return pool.random_between(first, last)
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