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#!/usr/bin/python
# -*- coding: ascii -*-
# Copyright (C) 2008 Dwayne C. Litzenberger <dlitz@dlitz.net>
# Copyright (C) 2008 Open Systems Canada Limited
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
class error(Exception):
pass
# Try to import the "winrandom" module
try:
from Crypto.Util import winrandom as _winrandom
except ImportError:
_winrandom = None
# Try to import the "urandom" module
try:
from os import urandom as _urandom
except ImportError:
_urandom = None
class _RNG(object):
def __init__(self, readfunc):
self.read = readfunc
def randomize(self):
# According to "Cryptanalysis of the Random Number Generator of the
# Windows Operating System", by Leo Dorrendorf and Zvi Gutterman
# and Benny Pinkas <http://eprint.iacr.org/2007/419>,
# CryptGenRandom only updates its internal state using kernel-provided
# random data every 128KiB of output.
self.read(128*1024) # discard 128 KiB of output
def _open_winrandom():
if _winrandom is None:
raise error("Crypto.Util.winrandom module not found")
# Check that we can open the winrandom module
try:
r0 = _winrandom.new()
r1 = _winrandom.new()
except Exception, exc:
raise error("winrandom.new() failed: %s" % str(exc), exc)
# Check that we can read from the winrandom module
try:
x = r0.get_bytes(20)
y = r1.get_bytes(20)
except Exception, exc:
raise error("winrandom get_bytes failed: %s" % str(exc), exc)
# Check that the requested number of bytes are returned
if len(x) != 20 or len(y) != 20:
raise error("Error reading from winrandom: input truncated")
# Check that different reads return different data
if x == y:
raise error("winrandom broken: returning identical data")
return _RNG(r0.get_bytes)
def _open_urandom():
if _urandom is None:
raise error("os.urandom function not found")
# Check that we can read from os.urandom()
try:
x = _urandom(20)
y = _urandom(20)
except Exception, exc:
raise error("os.urandom failed: %s" % str(exc), exc)
# Check that the requested number of bytes are returned
if len(x) != 20 or len(y) != 20:
raise error("os.urandom failed: input truncated")
# Check that different reads return different data
if x == y:
raise error("os.urandom failed: returning identical data")
return _RNG(_urandom)
def open_rng_device():
# Try using the Crypto.Util.winrandom module
try:
return _open_winrandom()
except error:
pass
# Several versions of PyCrypto do not contain the winrandom module, but
# Python >= 2.4 has os.urandom, so try to use that.
try:
return _open_urandom()
except error:
pass
# SECURITY NOTE: DO NOT USE Crypto.Util.randpool.RandomPool HERE!
# If we got to this point, RandomPool will silently run with very little
# entropy. (This is current as of PyCrypto 2.0.1).
# See http://www.lag.net/pipermail/paramiko/2008-January/000599.html
# and http://www.lag.net/pipermail/paramiko/2008-April/000678.html
raise error("Unable to find a strong random entropy source. You cannot run this software securely under the current configuration.")
# vim:set ts=4 sw=4 sts=4 expandtab:
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