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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.
import os
import stat
class error(Exception):
pass
class _RNG(object):
def __init__(self, file):
self.file = file
def read(self, bytes):
return self.file.read(bytes)
def close(self):
return self.file.close()
def randomize(self):
return
def open_rng_device(device_path=None):
"""Open /dev/urandom and perform some sanity checks."""
f = None
g = None
if device_path is None:
device_path = "/dev/urandom"
try:
# Try to open /dev/urandom now so that paramiko will be able to access
# it even if os.chroot() is invoked later.
try:
f = open(device_path, "rb", 0)
except EnvironmentError:
raise error("Unable to open /dev/urandom")
# Open a second file descriptor for sanity checking later.
try:
g = open(device_path, "rb", 0)
except EnvironmentError:
raise error("Unable to open /dev/urandom")
# Check that /dev/urandom is a character special device, not a regular file.
st = os.fstat(f.fileno()) # f
if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode):
raise error("/dev/urandom is not a character special device")
st = os.fstat(g.fileno()) # g
if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode):
raise error("/dev/urandom is not a character special device")
# Check that /dev/urandom always returns the number of bytes requested
x = f.read(20)
y = g.read(20)
if len(x) != 20 or len(y) != 20:
raise error("Error reading from /dev/urandom: input truncated")
# Check that different reads return different data
if x == y:
raise error("/dev/urandom is broken; returning identical data: %r == %r" % (x, y))
# Close the duplicate file object
g.close()
# Return the first file object
return _RNG(f)
except error:
if f is not None:
f.close()
if g is not None:
g.close()
raise
# vim:set ts=4 sw=4 sts=4 expandtab:
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