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106 lines
3.8 KiB
Python
106 lines
3.8 KiB
Python
#!/usr/bin/python
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# Copyright 2012 Citrix Systems, Inc. Licensed under the
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# Apache License, Version 2.0 (the "License"); you may not use this
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# file except in compliance with the License. Citrix Systems, Inc.
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# reserves all rights not expressly granted by the License.
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# You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# Automatically generated by addcopyright.py at 04/03/2012
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# -*- coding: ascii -*-
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# Copyright (C) 2008 Dwayne C. Litzenberger <dlitz@dlitz.net>
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# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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import sys
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import threading
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from Crypto.Util.randpool import RandomPool as _RandomPool
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try:
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import platform
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except ImportError:
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platform = None # Not available using Python 2.2
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def _strxor(a, b):
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assert len(a) == len(b)
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return "".join(map(lambda x, y: chr(ord(x) ^ ord(y)), a, b))
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## Find a strong random entropy source, depending on the detected platform.
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## WARNING TO DEVELOPERS: This will fail on some systems, but do NOT use
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## Crypto.Util.randpool.RandomPool as a fall-back. RandomPool will happily run
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## with very little entropy, thus _silently_ defeating any security that
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## Paramiko attempts to provide. (This is current as of PyCrypto 2.0.1).
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if ((platform is not None and platform.system().lower() == 'windows') or
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sys.platform == 'win32'):
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# MS Windows
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from paramiko import rng_win32
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rng_device = rng_win32.open_rng_device()
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else:
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# Assume POSIX (any system where /dev/urandom exists)
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from paramiko import rng_posix
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rng_device = rng_posix.open_rng_device()
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class StrongLockingRandomPool(object):
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"""Wrapper around RandomPool guaranteeing strong random numbers.
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Crypto.Util.randpool.RandomPool will silently operate even if it is seeded
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with little or no entropy, and it provides no prediction resistance if its
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state is ever compromised throughout its runtime. It is also not thread-safe.
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This wrapper augments RandomPool by XORing its output with random bits from
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the operating system, and by controlling access to the underlying
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RandomPool using an exclusive lock.
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"""
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def __init__(self, instance=None):
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if instance is None:
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instance = _RandomPool()
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self.randpool = instance
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self.randpool_lock = threading.Lock()
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self.entropy = rng_device
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# Stir 256 bits of entropy from the RNG device into the RandomPool.
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self.randpool.stir(self.entropy.read(32))
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self.entropy.randomize()
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def stir(self, s=''):
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self.randpool_lock.acquire()
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try:
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self.randpool.stir(s)
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finally:
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self.randpool_lock.release()
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self.entropy.randomize()
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def randomize(self, N=0):
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self.randpool_lock.acquire()
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try:
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self.randpool.randomize(N)
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finally:
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self.randpool_lock.release()
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self.entropy.randomize()
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def add_event(self, s=''):
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self.randpool_lock.acquire()
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try:
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self.randpool.add_event(s)
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finally:
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self.randpool_lock.release()
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def get_bytes(self, N):
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self.randpool_lock.acquire()
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try:
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randpool_data = self.randpool.get_bytes(N)
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finally:
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self.randpool_lock.release()
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entropy_data = self.entropy.read(N)
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result = _strxor(randpool_data, entropy_data)
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assert len(randpool_data) == N and len(entropy_data) == N and len(result) == N
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return result
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# vim:set ts=4 sw=4 sts=4 expandtab:
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