From 84eebc02f6088347ab1a76c3e53330538a0ab044 Mon Sep 17 00:00:00 2001
From: Robey Pointer <robey@lag.net>
Date: Mon, 21 Jan 2008 11:42:16 -0800
Subject: [PATCH] [project @ robey@lag.net-20080121194216-q3n5ovpeyiqjua6p]
 patch from dwayne litzenberger to fix the PRNG to be more resilient when
 using windows, and some forking/threading environments.

---
 paramiko/common.py   | 16 +-------
 paramiko/osrandom.py | 93 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+), 14 deletions(-)
 create mode 100644 paramiko/osrandom.py

diff --git a/paramiko/common.py b/paramiko/common.py
index 2dffad1..89b34cf 100644
--- a/paramiko/common.py
+++ b/paramiko/common.py
@@ -95,22 +95,10 @@ CONNECTION_FAILED_CODE = {
 DISCONNECT_SERVICE_NOT_AVAILABLE, DISCONNECT_AUTH_CANCELLED_BY_USER, \
     DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE = 7, 13, 14
 
-
-from Crypto.Util.randpool import PersistentRandomPool, RandomPool
+from osrandom import OSRandomPool
 
 # keep a crypto-strong PRNG nearby
-import os
-try:
-    randpool = PersistentRandomPool(os.path.join(os.path.expanduser('~'), '/.randpool'))
-except:
-    # the above will likely fail on Windows - fall back to non-persistent random pool
-    randpool = RandomPool()
-
-try:
-    randpool.randomize()
-except:
-    # earlier versions of pyCrypto (pre-2.0) don't have randomize()
-    pass
+randpool = OSRandomPool()
 
 import sys
 if sys.version_info < (2, 3):
diff --git a/paramiko/osrandom.py b/paramiko/osrandom.py
new file mode 100644
index 0000000..47c8f44
--- /dev/null
+++ b/paramiko/osrandom.py
@@ -0,0 +1,93 @@
+#!/usr/bin/python
+# -*- coding: ascii -*-
+# Copyright (C) 2008  Dwayne C. Litzenberger <dlitz@dlitz.net>
+#
+# 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 sys
+
+# Detect an OS random number source
+osrandom_source = None
+
+# Try os.urandom
+if osrandom_source is None:
+    try:
+        from os import urandom
+        osrandom_source = "os.urandom"
+    except ImportError:
+        pass
+
+# Try winrandom
+if osrandom_source is None:
+    try:
+        from Crypto.Util import winrandom
+        osrandom_source = "winrandom"
+    except ImportError:
+        pass
+
+# Try /dev/urandom
+if osrandom_source is None:
+    try:
+        _dev_urandom = open("/dev/urandom", "rb", 0)
+        def urandom(bytes):
+            return _def_urandom.read(bytes)
+        osrandom_source = "/dev/urandom"
+    except (OSError, IOError):
+        pass
+
+# Give up
+if osrandom_source is None:
+    raise ImportError("Cannot find OS entropy source")
+
+class BaseOSRandomPool(object):
+    def __init__(self, numbytes=160, cipher=None, hash=None):
+        pass
+
+    def stir(self, s=''):
+        # 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.
+        if osrandom_source == 'winrandom' or sys.platform == 'win32':
+            self.get_bytes(128*1024)    # discard 128 KiB of output
+
+    def randomize(self, N=0):
+        self.stir()
+
+    def add_event(self, s=None):
+        pass
+
+class WinrandomOSRandomPool(BaseOSRandomPool):
+    def __init__(self, numbytes=160, cipher=None, hash=None):
+        self._wr = winrandom.new()
+        self.get_bytes = self._wr.get_bytes
+        self.randomize()
+
+class UrandomOSRandomPool(BaseOSRandomPool):
+    def __init__(self, numbytes=160, cipher=None, hash=None):
+        self.get_bytes = urandom
+        self.randomize()
+
+if osrandom_source in ("/dev/urandom", "os.urandom"):
+    OSRandomPool = UrandomOSRandomPool
+elif osrandom_source == "winrandom":
+    OSRandomPool = WinrandomOSRandomPool
+else:
+    raise AssertionError("Unrecognized osrandom_source %r" % (osrandom_source,))
+
+# vim:set ts=4 sw=4 sts=4 expandtab: