Switch from using PyCrypto's Random to using os.urandom.

There's several reasons for this change:

1) It's faster for reads up to 1024 bytes (nearly 10x faster for 16 byte reads)
2) It receives considerably more security review since it's in the kernel.
3) It's yet another step towards running on PyPy.
4) Using userspace CSPRNGs is considered something of an anti-pattern. See:
   http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/
   http://webcache.googleusercontent.com/search?q=cache:2nTvpCgKZXIJ:www.2uo.de/myths-about-urandom/+&cd=3&hl=en&ct=clnk&gl=us

1 files changed, 9 insertions, 7 deletions

diff --git a/paramiko/dsskey.py b/paramiko/dsskey.py
index c26966e8..446353a0 100644
--- a/paramiko/dsskey.py
+++ b/paramiko/dsskey.py
@@ -20,11 +20,13 @@
 DSS keys.
 """
 
+import os
+
 from Crypto.PublicKey import DSA
 from Crypto.Hash import SHA
 
 from paramiko import util
-from paramiko.common import zero_byte, rng
+from paramiko.common import zero_byte
 from paramiko.py3compat import long
 from paramiko.ssh_exception import SSHException
 from paramiko.message import Message
@@ -91,17 +93,17 @@ class DSSKey (PKey):
 
     def get_bits(self):
         return self.size
-        
+
     def can_sign(self):
         return self.x is not None
 
-    def sign_ssh_data(self, rng, data):
+    def sign_ssh_data(self, data):
         digest = SHA.new(data).digest()
         dss = DSA.construct((long(self.y), long(self.g), long(self.p), long(self.q), long(self.x)))
         # generate a suitable k
         qsize = len(util.deflate_long(self.q, 0))
         while True:
-            k = util.inflate_long(rng.read(qsize), 1)
+            k = util.inflate_long(os.urandom(qsize), 1)
             if (k > 2) and (k < self.q):
                 break
         r, s = dss.sign(util.inflate_long(digest, 1), k)
@@ -163,7 +165,7 @@ class DSSKey (PKey):
             by ``pyCrypto.PublicKey``).
         :return: new `.DSSKey` private key
         """
-        dsa = DSA.generate(bits, rng.read, progress_func)
+        dsa = DSA.generate(bits, os.urandom, progress_func)
         key = DSSKey(vals=(dsa.p, dsa.q, dsa.g, dsa.y))
         key.x = dsa.x
         return key
@@ -174,11 +176,11 @@ class DSSKey (PKey):
     def _from_private_key_file(self, filename, password):
         data = self._read_private_key_file('DSA', filename, password)
         self._decode_key(data)
-    
+
     def _from_private_key(self, file_obj, password):
         data = self._read_private_key('DSA', file_obj, password)
         self._decode_key(data)
-    
+
     def _decode_key(self, data):
         # private key file contains:
         # DSAPrivateKey = { version = 0, p, q, g, y, x }