74 lines
2.6 KiB
Python
74 lines
2.6 KiB
Python
#
|
|
# Random/OSRNG/nt.py : OS entropy source for MS Windows
|
|
#
|
|
# Written in 2008 by Dwayne C. Litzenberger <dlitz@dlitz.net>
|
|
#
|
|
# ===================================================================
|
|
# The contents of this file are dedicated to the public domain. To
|
|
# the extent that dedication to the public domain is not available,
|
|
# everyone is granted a worldwide, perpetual, royalty-free,
|
|
# non-exclusive license to exercise all rights associated with the
|
|
# contents of this file for any purpose whatsoever.
|
|
# No rights are reserved.
|
|
#
|
|
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
|
|
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
|
|
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
|
|
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
|
|
# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
|
|
# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
|
|
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
|
|
# SOFTWARE.
|
|
# ===================================================================
|
|
|
|
|
|
__revision__ = "$Id$"
|
|
__all__ = ['WindowsRNG']
|
|
|
|
import winrandom
|
|
from .rng_base import BaseRNG
|
|
|
|
class WindowsRNG(BaseRNG):
|
|
|
|
name = "<CryptGenRandom>"
|
|
|
|
def __init__(self):
|
|
self.__winrand = winrandom.new()
|
|
BaseRNG.__init__(self)
|
|
|
|
def flush(self):
|
|
"""Work around weakness in Windows RNG.
|
|
|
|
The CryptGenRandom mechanism in some versions of Windows allows an
|
|
attacker to learn 128 KiB of past and future output. As a workaround,
|
|
this function reads 128 KiB of 'random' data from Windows and discards
|
|
it.
|
|
|
|
For more information about the weaknesses in CryptGenRandom, see
|
|
_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
|
|
"""
|
|
if self.closed:
|
|
raise ValueError("I/O operation on closed file")
|
|
data = self.__winrand.get_bytes(128*1024)
|
|
assert (len(data) == 128*1024)
|
|
BaseRNG.flush(self)
|
|
|
|
def _close(self):
|
|
self.__winrand = None
|
|
|
|
def _read(self, N):
|
|
# Unfortunately, research shows that CryptGenRandom doesn't provide
|
|
# forward secrecy and fails the next-bit test unless we apply a
|
|
# workaround, which we do here. See http://eprint.iacr.org/2007/419
|
|
# for information on the vulnerability.
|
|
self.flush()
|
|
data = self.__winrand.get_bytes(N)
|
|
self.flush()
|
|
return data
|
|
|
|
def new(*args, **kwargs):
|
|
return WindowsRNG(*args, **kwargs)
|
|
|
|
# vim:set ts=4 sw=4 sts=4 expandtab:
|