# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2009-2017 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 hashlib
import os
import random
import threading
import time
from typing import Any, Optional
class EntropyPool:
# This is an entropy pool for Python implementations that do not
# have a working SystemRandom. I'm not sure there are any, but
# leaving this code doesn't hurt anything as the library code
# is used if present.
def __init__(self, seed: Optional[bytes] = None):
self.pool_index = 0
self.digest: Optional[bytearray] = None
self.next_byte = 0
self.lock = threading.Lock()
self.hash = hashlib.sha1()
self.hash_len = 20
self.pool = bytearray(b"\0" * self.hash_len)
if seed is not None:
self._stir(seed)
self.seeded = True
self.seed_pid = os.getpid()
else:
self.seeded = False
self.seed_pid = 0
def _stir(self, entropy: bytes) -> None:
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
def stir(self, entropy: bytes) -> None:
with self.lock:
self._stir(entropy)
def _maybe_seed(self) -> None:
if not self.seeded or self.seed_pid != os.getpid():
try:
seed = os.urandom(16)
except Exception: # pragma: no cover
try:
with open("/dev/urandom", "rb", 0) as r:
seed = r.read(16)
except Exception:
seed = str(time.time()).encode()
self.seeded = True
self.seed_pid = os.getpid()
self.digest = None
seed = bytearray(seed)
self._stir(seed)
def random_8(self) -> int:
with self.lock:
self._maybe_seed()
if self.digest is None or self.next_byte == self.hash_len:
self.hash.update(bytes(self.pool))
self.digest = bytearray(self.hash.digest())
self._stir(self.digest)
self.next_byte = 0
value = self.digest[self.next_byte]
self.next_byte += 1
return value
def random_16(self) -> int:
return self.random_8() * 256 + self.random_8()
def random_32(self) -> int:
return self.random_16() * 65536 + self.random_16()
def random_between(self, first: int, last: int) -> int:
size = last - first + 1
if size > 4294967296:
raise ValueError("too big")
if size > 65536:
rand = self.random_32
max = 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()
system_random: Optional[Any]
try:
system_random = random.SystemRandom()
except Exception: # pragma: no cover
system_random = None
def random_16() -> int:
if system_random is not None:
return system_random.randrange(0, 65536)
else:
return pool.random_16()
def between(first: int, last: int) -> int:
if system_random is not None:
return system_random.randrange(first, last + 1)
else:
return pool.random_between(first, last)
