131 lines
4.1 KiB
Python
131 lines
4.1 KiB
Python
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
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# Copyright (C) 2009-2017 Nominum, Inc.
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#
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# Permission to use, copy, modify, and distribute this software and its
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# documentation for any purpose with or without fee is hereby granted,
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# provided that the above copyright notice and this permission notice
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# appear in all copies.
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#
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# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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import hashlib
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import os
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import random
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import threading
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import time
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from typing import Any, Optional
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class EntropyPool:
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# This is an entropy pool for Python implementations that do not
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# have a working SystemRandom. I'm not sure there are any, but
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# leaving this code doesn't hurt anything as the library code
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# is used if present.
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def __init__(self, seed: Optional[bytes] = None):
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self.pool_index = 0
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self.digest: Optional[bytearray] = None
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self.next_byte = 0
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self.lock = threading.Lock()
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self.hash = hashlib.sha1()
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self.hash_len = 20
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self.pool = bytearray(b"\0" * self.hash_len)
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if seed is not None:
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self._stir(seed)
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self.seeded = True
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self.seed_pid = os.getpid()
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else:
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self.seeded = False
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self.seed_pid = 0
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def _stir(self, entropy: bytes) -> None:
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for c in entropy:
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if self.pool_index == self.hash_len:
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self.pool_index = 0
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b = c & 0xFF
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self.pool[self.pool_index] ^= b
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self.pool_index += 1
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def stir(self, entropy: bytes) -> None:
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with self.lock:
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self._stir(entropy)
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def _maybe_seed(self) -> None:
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if not self.seeded or self.seed_pid != os.getpid():
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try:
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seed = os.urandom(16)
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except Exception: # pragma: no cover
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try:
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with open("/dev/urandom", "rb", 0) as r:
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seed = r.read(16)
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except Exception:
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seed = str(time.time()).encode()
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self.seeded = True
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self.seed_pid = os.getpid()
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self.digest = None
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seed = bytearray(seed)
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self._stir(seed)
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def random_8(self) -> int:
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with self.lock:
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self._maybe_seed()
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if self.digest is None or self.next_byte == self.hash_len:
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self.hash.update(bytes(self.pool))
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self.digest = bytearray(self.hash.digest())
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self._stir(self.digest)
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self.next_byte = 0
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value = self.digest[self.next_byte]
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self.next_byte += 1
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return value
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def random_16(self) -> int:
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return self.random_8() * 256 + self.random_8()
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def random_32(self) -> int:
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return self.random_16() * 65536 + self.random_16()
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def random_between(self, first: int, last: int) -> int:
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size = last - first + 1
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if size > 4294967296:
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raise ValueError("too big")
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if size > 65536:
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rand = self.random_32
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max = 4294967295
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elif size > 256:
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rand = self.random_16
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max = 65535
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else:
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rand = self.random_8
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max = 255
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return first + size * rand() // (max + 1)
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pool = EntropyPool()
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system_random: Optional[Any]
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try:
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system_random = random.SystemRandom()
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except Exception: # pragma: no cover
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system_random = None
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def random_16() -> int:
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if system_random is not None:
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return system_random.randrange(0, 65536)
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else:
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return pool.random_16()
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def between(first: int, last: int) -> int:
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if system_random is not None:
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return system_random.randrange(first, last + 1)
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else:
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return pool.random_between(first, last)
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