Source Code for Module paramiko.rng_win32

  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