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