paramiko.rng

Source Code for Module paramiko.rng_posix

+ 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 import os +23 import stat +24 +

25 -class error(Exception): +

26 pass +

27 +

28 -class _RNG(object): +

29 - def __init__(self, file): +

30 self.file = file +

31 +

32 - def read(self, bytes): +

33 return self.file.read(bytes) +

34 +

35 - def close(self): +

36 return self.file.close() +

37 +

38 - def randomize(self): +

39 return +

40 +

41 -def open_rng_device(device_path=None): +

42 """Open /dev/urandom and perform some sanity checks.""" +43 +44 f = None +45 g = None +46 +47 if device_path is None: +48 device_path = "/dev/urandom" +49 +50 try: +51 # Try to open /dev/urandom now so that paramiko will be able to access +52 # it even if os.chroot() is invoked later. +53 try: +54 f = open(device_path, "rb", 0) +55 except EnvironmentError: +56 raise error("Unable to open /dev/urandom") +57 +58 # Open a second file descriptor for sanity checking later. +59 try: +60 g = open(device_path, "rb", 0) +61 except EnvironmentError: +62 raise error("Unable to open /dev/urandom") +63 +64 # Check that /dev/urandom is a character special device, not a regular file. +65 st = os.fstat(f.fileno()) # f +66 if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode): +67 raise error("/dev/urandom is not a character special device") +68 +69 st = os.fstat(g.fileno()) # g +70 if stat.S_ISREG(st.st_mode) or not stat.S_ISCHR(st.st_mode): +71 raise error("/dev/urandom is not a character special device") +72 +73 # Check that /dev/urandom always returns the number of bytes requested +74 x = f.read(20) +75 y = g.read(20) +76 if len(x) != 20 or len(y) != 20: +77 raise error("Error reading from /dev/urandom: input truncated") +78 +79 # Check that different reads return different data +80 if x == y: +81 raise error("/dev/urandom is broken; returning identical data: %r == %r" % (x, y)) +82 +83 # Close the duplicate file object +84 g.close() +85 +86 # Return the first file object +87 return _RNG(f) +88 +89 except error: +90 if f is not None: +91 f.close() +92 if g is not None: +93 g.close() +94 raise +

95 +96 # vim:set ts=4 sw=4 sts=4 expandtab: +97 +