paramiko.rng

+ 1 #!/usr/bin/python + 2 # -*- coding: ascii -*- + 3 # Copyright (C) 2008 Dwayne C. Litzenberger <dlitz@dlitz.net> + 4 # Copyright (C) 2008 Open Systems Canada Limited + 5 # + 6 # This file is part of paramiko. + 7 # + 8 # Paramiko is free software; you can redistribute it and/or modify it under the + 9 # terms of the GNU Lesser General Public License as published by the Free + 10 # Software Foundation; either version 2.1 of the License, or (at your option) + 11 # any later version. + 12 # + 13 # Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY + 14 # WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR + 15 # A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more + 16 # details. + 17 # + 18 # You should have received a copy of the GNU Lesser General Public License + 19 # along with Paramiko; if not, write to the Free Software Foundation, Inc., + 20 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + 21 +

22 -class error(Exception): +

23 pass +

24 + 25 # Try to import the "winrandom" module + 26 try: + 27 from Crypto.Util import winrandom as _winrandom + 28 except ImportError: + 29 _winrandom = None + 30 + 31 # Try to import the "urandom" module + 32 try: + 33 from os import urandom as _urandom + 34 except ImportError: + 35 _urandom = None + 36 + 37 +

38 -class _RNG(object): +

39 - def __init__(self, readfunc): +

40 self.read = readfunc +

41 +

42 - def randomize(self): +

43 # According to "Cryptanalysis of the Random Number Generator of the + 44 # Windows Operating System", by Leo Dorrendorf and Zvi Gutterman + 45 # and Benny Pinkas <http://eprint.iacr.org/2007/419>, + 46 # CryptGenRandom only updates its internal state using kernel-provided + 47 # random data every 128KiB of output. + 48 self.read(128*1024) # discard 128 KiB of output +

49 +

50 -def _open_winrandom(): +

51 if _winrandom is None: + 52 raise error("Crypto.Util.winrandom module not found") + 53 + 54 # Check that we can open the winrandom module + 55 try: + 56 r0 = _winrandom.new() + 57 r1 = _winrandom.new() + 58 except Exception, exc: + 59 raise error("winrandom.new() failed: %s" % str(exc), exc) + 60 + 61 # Check that we can read from the winrandom module + 62 try: + 63 x = r0.get_bytes(20) + 64 y = r1.get_bytes(20) + 65 except Exception, exc: + 66 raise error("winrandom get_bytes failed: %s" % str(exc), exc) + 67 + 68 # Check that the requested number of bytes are returned + 69 if len(x) != 20 or len(y) != 20: + 70 raise error("Error reading from winrandom: input truncated") + 71 + 72 # Check that different reads return different data + 73 if x == y: + 74 raise error("winrandom broken: returning identical data") + 75 + 76 return _RNG(r0.get_bytes) +

77 +

78 -def _open_urandom(): +

79 if _urandom is None: + 80 raise error("os.urandom function not found") + 81 + 82 # Check that we can read from os.urandom() + 83 try: + 84 x = _urandom(20) + 85 y = _urandom(20) + 86 except Exception, exc: + 87 raise error("os.urandom failed: %s" % str(exc), exc) + 88 + 89 # Check that the requested number of bytes are returned + 90 if len(x) != 20 or len(y) != 20: + 91 raise error("os.urandom failed: input truncated") + 92 + 93 # Check that different reads return different data + 94 if x == y: + 95 raise error("os.urandom failed: returning identical data") + 96 + 97 return _RNG(_urandom) +

98 +

99 -def open_rng_device(): +

100 # Try using the Crypto.Util.winrandom module +101 try: +102 return _open_winrandom() +103 except error: +104 pass +105 +106 # Several versions of PyCrypto do not contain the winrandom module, but +107 # Python >= 2.4 has os.urandom, so try to use that. +108 try: +109 return _open_urandom() +110 except error: +111 pass +112 +113 # SECURITY NOTE: DO NOT USE Crypto.Util.randpool.RandomPool HERE! +114 # If we got to this point, RandomPool will silently run with very little +115 # entropy. (This is current as of PyCrypto 2.0.1). +116 # See http://www.lag.net/pipermail/paramiko/2008-January/000599.html +117 # and http://www.lag.net/pipermail/paramiko/2008-April/000678.html +118 +119 raise error("Unable to find a strong random entropy source. You cannot run this software securely under the current configuration.") +

120 +121 # vim:set ts=4 sw=4 sts=4 expandtab: +122 +

Source Code for Module paramiko.rng_win32