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| Current File : //usr/lib64/python2.7/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 time
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:
try:
import sha
self.hash = sha.new()
self.hash_len = 20
except:
import md5
self.hash = md5.new()
self.hash_len = 16
self.pool = '\0' * self.hash_len
if not seed is None:
self.stir(seed)
self.seeded = True
else:
self.seeded = False
def stir(self, entropy, already_locked=False):
if not already_locked:
self.lock.acquire()
try:
bytes = [ord(c) for c in self.pool]
for c in entropy:
if self.pool_index == self.hash_len:
self.pool_index = 0
b = ord(c) & 0xff
bytes[self.pool_index] ^= b
self.pool_index += 1
self.pool = ''.join([chr(c) for c in bytes])
finally:
if not already_locked:
self.lock.release()
def _maybe_seed(self):
if not self.seeded:
try:
seed = os.urandom(16)
except:
try:
r = file('/dev/urandom', 'r', 0)
try:
seed = r.read(16)
finally:
r.close()
except:
seed = str(time.time())
self.seeded = True
self.stir(seed, True)
def random_8(self):
self.lock.acquire()
self._maybe_seed()
try:
if self.digest is None or self.next_byte == self.hash_len:
self.hash.update(self.pool)
self.digest = self.hash.digest()
self.stir(self.digest, True)
self.next_byte = 0
value = ord(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 > 4294967296L:
raise ValueError('too big')
if size > 65536:
rand = self.random_32
max = 4294967295L
elif size > 256:
rand = self.random_16
max = 65535
else:
rand = self.random_8
max = 255
return (first + size * rand() // (max + 1))
pool = EntropyPool()
def random_16():
return pool.random_16()
def between(first, last):
return pool.random_between(first, last)