Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/dns/entropy.py: 41%

1# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license 

2 

3# Copyright (C) 2009-2017 Nominum, Inc. 

4# 

5# Permission to use, copy, modify, and distribute this software and its 

6# documentation for any purpose with or without fee is hereby granted, 

7# provided that the above copyright notice and this permission notice 

8# appear in all copies. 

9# 

10# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES 

11# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 

12# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR 

13# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 

14# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 

15# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT 

16# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 

17 

18import hashlib 

19import os 

20import random 

21import threading 

22import time 

23from typing import Any, Optional 

24 

25 

26class EntropyPool: 

27 # This is an entropy pool for Python implementations that do not 

28 # have a working SystemRandom. I'm not sure there are any, but 

29 # leaving this code doesn't hurt anything as the library code 

30 # is used if present. 

31 

32 def __init__(self, seed: Optional[bytes] = None): 

33 self.pool_index = 0 

34 self.digest: Optional[bytearray] = None 

35 self.next_byte = 0 

36 self.lock = threading.Lock() 

37 self.hash = hashlib.sha1() 

38 self.hash_len = 20 

39 self.pool = bytearray(b"\0" * self.hash_len) 

40 if seed is not None: 

41 self._stir(seed) 

42 self.seeded = True 

43 self.seed_pid = os.getpid() 

44 else: 

45 self.seeded = False 

46 self.seed_pid = 0 

47 

48 def _stir(self, entropy: bytes) -> None: 

49 for c in entropy: 

50 if self.pool_index == self.hash_len: 

51 self.pool_index = 0 

52 b = c & 0xFF 

53 self.pool[self.pool_index] ^= b 

54 self.pool_index += 1 

55 

56 def stir(self, entropy: bytes) -> None: 

57 with self.lock: 

58 self._stir(entropy) 

59 

60 def _maybe_seed(self) -> None: 

61 if not self.seeded or self.seed_pid != os.getpid(): 

62 try: 

63 seed = os.urandom(16) 

64 except Exception: # pragma: no cover 

65 try: 

66 with open("/dev/urandom", "rb", 0) as r: 

67 seed = r.read(16) 

68 except Exception: 

69 seed = str(time.time()).encode() 

70 self.seeded = True 

71 self.seed_pid = os.getpid() 

72 self.digest = None 

73 seed = bytearray(seed) 

74 self._stir(seed) 

75 

76 def random_8(self) -> int: 

77 with self.lock: 

78 self._maybe_seed() 

79 if self.digest is None or self.next_byte == self.hash_len: 

80 self.hash.update(bytes(self.pool)) 

81 self.digest = bytearray(self.hash.digest()) 

82 self._stir(self.digest) 

83 self.next_byte = 0 

84 value = self.digest[self.next_byte] 

85 self.next_byte += 1 

86 return value 

87 

88 def random_16(self) -> int: 

89 return self.random_8() * 256 + self.random_8() 

90 

91 def random_32(self) -> int: 

92 return self.random_16() * 65536 + self.random_16() 

93 

94 def random_between(self, first: int, last: int) -> int: 

95 size = last - first + 1 

96 if size > 4294967296: 

97 raise ValueError("too big") 

98 if size > 65536: 

99 rand = self.random_32 

100 max = 4294967295 

101 elif size > 256: 

102 rand = self.random_16 

103 max = 65535 

104 else: 

105 rand = self.random_8 

106 max = 255 

107 return first + size * rand() // (max + 1) 

108 

109 

110pool = EntropyPool() 

111 

112system_random: Optional[Any] 

113try: 

114 system_random = random.SystemRandom() 

115except Exception: # pragma: no cover 

116 system_random = None 

117 

118 

119def random_16() -> int: 

120 if system_random is not None: 

121 return system_random.randrange(0, 65536) 

122 else: 

123 return pool.random_16() 

124 

125 

126def between(first: int, last: int) -> int: 

127 if system_random is not None: 

128 return system_random.randrange(first, last + 1) 

129 else: 

130 return pool.random_between(first, last)