1 files changed, 121 insertions, 0 deletions
diff --git a/paramiko/rng_win32.py b/paramiko/rng_win32.py
new file mode 100644
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--- /dev/null
+++ b/paramiko/rng_win32.py
@@ -0,0 +1,121 @@
+#!/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: