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

paramiko/agent.py

@@ -364,7 +364,7 @@ class AgentKey(PKey):
     def get_name(self):
         return self.name
 
-    def sign_ssh_data(self, rng, data):
+    def sign_ssh_data(self, data):
         msg = Message()
         msg.add_byte(cSSH2_AGENTC_SIGN_REQUEST)
         msg.add_string(self.blob)

paramiko/auth_handler.py

@@ -206,7 +206,7 @@ class AuthHandler (object):
                 m.add_string(self.private_key.get_name())
                 m.add_string(self.private_key)
                 blob = self._get_session_blob(self.private_key, 'ssh-connection', self.username)
-                sig = self.private_key.sign_ssh_data(self.transport.rng, blob)
+                sig = self.private_key.sign_ssh_data(blob)
                 m.add_string(sig)
             elif self.auth_method == 'keyboard-interactive':
                 m.add_string('')

paramiko/channel.py

@@ -21,9 +21,10 @@ Abstraction for an SSH2 channel.
 """
 
 import binascii
+import os
+import socket
 import time
 import threading
-import socket
 
 from paramiko import util
 from paramiko.common import cMSG_CHANNEL_REQUEST, cMSG_CHANNEL_WINDOW_ADJUST, \
@@ -358,7 +359,7 @@ class Channel (object):
         if auth_protocol is None:
             auth_protocol = 'MIT-MAGIC-COOKIE-1'
         if auth_cookie is None:
-            auth_cookie = binascii.hexlify(self.transport.rng.read(16))
+            auth_cookie = binascii.hexlify(os.urandom(16))
 
         m = Message()
         m.add_byte(cMSG_CHANNEL_REQUEST)

paramiko/common.py

@@ -126,11 +126,6 @@ CONNECTION_FAILED_CODE = {
 DISCONNECT_SERVICE_NOT_AVAILABLE, DISCONNECT_AUTH_CANCELLED_BY_USER, \
     DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE = 7, 13, 14
 
-from Crypto import Random
-
-# keep a crypto-strong PRNG nearby
-rng = Random.new()
-
 zero_byte = byte_chr(0)
 one_byte = byte_chr(1)
 four_byte = byte_chr(4)

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
@@ -95,13 +97,13 @@ class DSSKey (PKey):
     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

paramiko/ecdsakey.py

@@ -21,11 +21,14 @@ L{ECDSAKey}
 """
 
 import binascii
-from ecdsa import SigningKey, VerifyingKey, der, curves
+import os
-from Crypto.Hash import SHA256
-from ecdsa.test_pyecdsa import ECDSA
-from paramiko.common import four_byte, one_byte
 
+from ecdsa import SigningKey, VerifyingKey, der, curves
+from ecdsa.test_pyecdsa import ECDSA
+
+from Crypto.Hash import SHA256
+
+from paramiko.common import four_byte, one_byte
 from paramiko.message import Message
 from paramiko.pkey import PKey
 from paramiko.py3compat import byte_chr, u
@@ -97,9 +100,9 @@ class ECDSAKey (PKey):
     def can_sign(self):
         return self.signing_key is not None
 
-    def sign_ssh_data(self, rpool, data):
+    def sign_ssh_data(self, data):
         digest = SHA256.new(data).digest()
-        sig = self.signing_key.sign_digest(digest, entropy=rpool.read,
+        sig = self.signing_key.sign_digest(digest, entropy=os.urandom,
                                            sigencode=self._sigencode)
         m = Message()
         m.add_string('ecdsa-sha2-nistp256')

paramiko/hostkeys.py

@@ -18,8 +18,10 @@
 
 
 import binascii
+import os
+
 from Crypto.Hash import SHA, HMAC
-from paramiko.common import rng
+
 from paramiko.py3compat import b, u, encodebytes, decodebytes
 
 try:
@@ -262,7 +264,7 @@ class HostKeys (MutableMapping):
         :return: the hashed hostname as a `str`
         """
         if salt is None:
-            salt = rng.read(SHA.digest_size)
+            salt = os.urandom(SHA.digest_size)
         else:
             if salt.startswith('|1|'):
                 salt = salt.split('|')[2]

paramiko/kex_gex.py

@@ -22,6 +22,8 @@ generator "g" are provided by the server.  A bit more work is required on the
 client side, and a B{lot} more on the server side.
 """
 
+import os
+
 from Crypto.Hash import SHA
 
 from paramiko import util
@@ -101,7 +103,7 @@ class KexGex (object):
             qhbyte <<= 1
             qmask >>= 1
         while True:
-            x_bytes = self.transport.rng.read(byte_count)
+            x_bytes = os.urandom(byte_count)
             x_bytes = byte_mask(x_bytes[0], qmask) + x_bytes[1:]
             x = util.inflate_long(x_bytes, 1)
             if (x > 1) and (x < q):
@@ -206,7 +208,7 @@ class KexGex (object):
         H = SHA.new(hm.asbytes()).digest()
         self.transport._set_K_H(K, H)
         # sign it
-        sig = self.transport.get_server_key().sign_ssh_data(self.transport.rng, H)
+        sig = self.transport.get_server_key().sign_ssh_data(H)
         # send reply
         m = Message()
         m.add_byte(c_MSG_KEXDH_GEX_REPLY)

paramiko/kex_group1.py

@@ -21,6 +21,8 @@ Standard SSH key exchange ("kex" if you wanna sound cool).  Diffie-Hellman of
 1024 bit key halves, using a known "p" prime and "g" generator.
 """
 
+import os
+
 from Crypto.Hash import SHA
 
 from paramiko import util
@@ -82,7 +84,7 @@ class KexGroup1(object):
         # potential x where the first 63 bits are 1, because some of those will be
         # larger than q (but this is a tiny tiny subset of potential x).
         while 1:
-            x_bytes = self.transport.rng.read(128)
+            x_bytes = os.urandom(128)
             x_bytes = byte_mask(x_bytes[0], 0x7f) + x_bytes[1:]
             if (x_bytes[:8] != b7fffffffffffffff and
                     x_bytes[:8] != b0000000000000000):
@@ -127,7 +129,7 @@ class KexGroup1(object):
         H = SHA.new(hm.asbytes()).digest()
         self.transport._set_K_H(K, H)
         # sign it
-        sig = self.transport.get_server_key().sign_ssh_data(self.transport.rng, H)
+        sig = self.transport.get_server_key().sign_ssh_data(H)
         # send reply
         m = Message()
         m.add_byte(c_MSG_KEXDH_REPLY)

paramiko/packet.py

@@ -21,6 +21,7 @@ Packet handling
 """
 
 import errno
+import os
 import socket
 import struct
 import threading
@@ -28,7 +29,7 @@ import time
 
 from paramiko import util
 from paramiko.common import linefeed_byte, cr_byte_value, asbytes, MSG_NAMES, \
-    DEBUG, xffffffff, zero_byte, rng
+    DEBUG, xffffffff, zero_byte
 from paramiko.py3compat import u, byte_ord
 from paramiko.ssh_exception import SSHException, ProxyCommandFailure
 from paramiko.message import Message
@@ -455,7 +456,7 @@ class Packetizer (object):
             # don't waste random bytes for the padding
             packet += (zero_byte * padding)
         else:
-            packet += rng.read(padding)
+            packet += os.urandom(padding)
         return packet
 
     def _trigger_rekey(self):

paramiko/pkey.py

@@ -28,7 +28,7 @@ from Crypto.Hash import MD5
 from Crypto.Cipher import DES3, AES
 
 from paramiko import util
-from paramiko.common import o600, rng, zero_byte
+from paramiko.common import o600, zero_byte
 from paramiko.py3compat import u, encodebytes, decodebytes, b
 from paramiko.ssh_exception import SSHException, PasswordRequiredException
 
@@ -138,12 +138,11 @@ class PKey (object):
         """
         return u(encodebytes(self.asbytes())).replace('\n', '')
 
-    def sign_ssh_data(self, rng, data):
+    def sign_ssh_data(self, data):
         """
         Sign a blob of data with this private key, and return a `.Message`
         representing an SSH signature message.
 
-        :param .Crypto.Util.rng.RandomPool rng: a secure random number generator.
         :param str data: the data to sign.
         :return: an SSH signature `message <.Message>`.
         """
@@ -331,11 +330,11 @@ class PKey (object):
             keysize = self._CIPHER_TABLE[cipher_name]['keysize']
             blocksize = self._CIPHER_TABLE[cipher_name]['blocksize']
             mode = self._CIPHER_TABLE[cipher_name]['mode']
-            salt = rng.read(16)
+            salt = os.urandom(16)
             key = util.generate_key_bytes(MD5, salt, password, keysize)
             if len(data) % blocksize != 0:
                 n = blocksize - len(data) % blocksize
-                #data += rng.read(n)
+                #data += os.urandom(n)
                 # that would make more sense ^, but it confuses openssh.
                 data += zero_byte * n
             data = cipher.new(key, mode, salt).encrypt(data)

paramiko/primes.py

@@ -20,6 +20,8 @@
 Utility functions for dealing with primes.
 """
 
+import os
+
 from Crypto.Util import number
 
 from paramiko import util
@@ -27,12 +29,12 @@ from paramiko.py3compat import byte_mask, long
 from paramiko.ssh_exception import SSHException
 
 
-def _generate_prime(bits, rng):
+def _generate_prime(bits):
     """primtive attempt at prime generation"""
     hbyte_mask = pow(2, bits % 8) - 1
     while True:
         # loop catches the case where we increment n into a higher bit-range
-        x = rng.read((bits + 7) // 8)
+        x = os.urandom((bits + 7) // 8)
         if hbyte_mask > 0:
             x = byte_mask(x[0], hbyte_mask) + x[1:]
         n = util.inflate_long(x, 1)
@@ -45,7 +47,7 @@ def _generate_prime(bits, rng):
     return n
 
 
-def _roll_random(rng, n):
+def _roll_random(n):
     """returns a random # from 0 to N-1"""
     bits = util.bit_length(n - 1)
     byte_count = (bits + 7) // 8
@@ -58,7 +60,7 @@ def _roll_random(rng, n):
     # fits, so i can't guarantee that this loop will ever finish, but the odds
     # of it looping forever should be infinitesimal.
     while True:
-        x = rng.read(byte_count)
+        x = os.urandom(byte_count)
         if hbyte_mask > 0:
             x = byte_mask(x[0], hbyte_mask) + x[1:]
         num = util.inflate_long(x, 1)
@@ -73,11 +75,10 @@ class ModulusPack (object):
     on systems that have such a file.
     """
 
-    def __init__(self, rpool):
+    def __init__(self):
         # pack is a hash of: bits -> [ (generator, modulus) ... ]
         self.pack = {}
         self.discarded = []
-        self.rng = rpool
 
     def _parse_modulus(self, line):
         timestamp, mod_type, tests, tries, size, generator, modulus = line.split()
@@ -147,5 +148,5 @@ class ModulusPack (object):
             if min > good:
                 good = bitsizes[-1]
         # now pick a random modulus of this bitsize
-        n = _roll_random(self.rng, len(self.pack[good]))
+        n = _roll_random(len(self.pack[good]))
         return self.pack[good][n]

paramiko/rsakey.py

@@ -20,11 +20,13 @@
 RSA keys.
 """
 
+import os
+
 from Crypto.PublicKey import RSA
 from Crypto.Hash import SHA
 
 from paramiko import util
-from paramiko.common import rng, max_byte, zero_byte, one_byte
+from paramiko.common import max_byte, zero_byte, one_byte
 from paramiko.message import Message
 from paramiko.ber import BER, BERException
 from paramiko.pkey import PKey
@@ -90,7 +92,7 @@ class RSAKey (PKey):
     def can_sign(self):
         return self.d is not None
 
-    def sign_ssh_data(self, rpool, data):
+    def sign_ssh_data(self, data):
         digest = SHA.new(data).digest()
         rsa = RSA.construct((long(self.n), long(self.e), long(self.d)))
         sig = util.deflate_long(rsa.sign(self._pkcs1imify(digest), bytes())[0], 0)
@@ -140,7 +142,7 @@ class RSAKey (PKey):
             by ``pyCrypto.PublicKey``).
         :return: new `.RSAKey` private key
         """
-        rsa = RSA.generate(bits, rng.read, progress_func)
+        rsa = RSA.generate(bits, os.urandom, progress_func)
         key = RSAKey(vals=(rsa.e, rsa.n))
         key.d = rsa.d
         key.p = rsa.p

paramiko/transport.py

@@ -20,6 +20,7 @@
 Core protocol implementation
 """
 
+import os
 import socket
 import sys
 import threading
@@ -30,7 +31,7 @@ import paramiko
 from paramiko import util
 from paramiko.auth_handler import AuthHandler
 from paramiko.channel import Channel
-from paramiko.common import rng, xffffffff, cMSG_CHANNEL_OPEN, cMSG_IGNORE, \
+from paramiko.common import xffffffff, cMSG_CHANNEL_OPEN, cMSG_IGNORE, \
     cMSG_GLOBAL_REQUEST, DEBUG, MSG_KEXINIT, MSG_IGNORE, MSG_DISCONNECT, \
     MSG_DEBUG, ERROR, WARNING, cMSG_UNIMPLEMENTED, INFO, cMSG_KEXINIT, \
     cMSG_NEWKEYS, MSG_NEWKEYS, cMSG_REQUEST_SUCCESS, cMSG_REQUEST_FAILURE, \
@@ -57,7 +58,6 @@ from paramiko.ssh_exception import (SSHException, BadAuthenticationType,
                                     ChannelException, ProxyCommandFailure)
 from paramiko.util import retry_on_signal
 
-from Crypto import Random
 from Crypto.Cipher import Blowfish, AES, DES3, ARC4
 from Crypto.Hash import SHA, MD5
 try:
@@ -192,7 +192,6 @@ class Transport (threading.Thread):
         # okay, normal socket-ish flow here...
         threading.Thread.__init__(self)
         self.setDaemon(True)
-        self.rng = rng
         self.sock = sock
         # Python < 2.3 doesn't have the settimeout method - RogerB
         try:
@@ -339,7 +338,6 @@ class Transport (threading.Thread):
         # synchronous, wait for a result
         self.completion_event = event = threading.Event()
         self.start()
-        Random.atfork()
         while True:
             event.wait(0.1)
             if not self.active:
@@ -475,7 +473,7 @@ class Transport (threading.Thread):
 
         .. note:: This has no effect when used in client mode.
         """
-        Transport._modulus_pack = ModulusPack(rng)
+        Transport._modulus_pack = ModulusPack()
         # places to look for the openssh "moduli" file
         file_list = ['/etc/ssh/moduli', '/usr/local/etc/moduli']
         if filename is not None:
@@ -732,8 +730,8 @@ class Transport (threading.Thread):
         m = Message()
         m.add_byte(cMSG_IGNORE)
         if byte_count is None:
-            byte_count = (byte_ord(rng.read(1)) % 32) + 10
+            byte_count = (byte_ord(os.urandom(1)) % 32) + 10
-        m.add_bytes(rng.read(byte_count))
+        m.add_bytes(os.urandom(byte_count))
         self._send_user_message(m)
 
     def renegotiate_keys(self):
@@ -1402,10 +1400,6 @@ class Transport (threading.Thread):
         # interpreter shutdown.
         self.sys = sys
 
-        # Required to prevent RNG errors when running inside many subprocess
-        # containers.
-        Random.atfork()
-
         # active=True occurs before the thread is launched, to avoid a race
         _active_threads.append(self)
         if self.server_mode:
@@ -1590,7 +1584,7 @@ class Transport (threading.Thread):
 
         m = Message()
         m.add_byte(cMSG_KEXINIT)
-        m.add_bytes(rng.read(16))
+        m.add_bytes(os.urandom(16))
         m.add_list(self._preferred_kex)
         m.add_list(available_server_keys)
         m.add_list(self._preferred_ciphers)

tests/test_kex.py

@@ -21,7 +21,9 @@ Some unit tests for the key exchange protocols.
 """
 
 from binascii import hexlify
+import os
 import unittest
+
 import paramiko.util
 from paramiko.kex_group1 import KexGroup1
 from paramiko.kex_gex import KexGex
@@ -29,9 +31,8 @@ from paramiko import Message
 from paramiko.common import byte_chr
 
 
-class FakeRng (object):
+def dummy_urandom(n):
-    def read(self, n):
+    return byte_chr(0xcc) * n
-        return byte_chr(0xcc) * n
 
 
 class FakeKey (object):
@@ -41,7 +42,7 @@ class FakeKey (object):
     def asbytes(self):
         return b'fake-key'
 
-    def sign_ssh_data(self, rng, H):
+    def sign_ssh_data(self, H):
         return b'fake-sig'
 
 
@@ -53,8 +54,7 @@ class FakeModulusPack (object):
         return self.G, self.P
 
 
-class FakeTransport (object):
+class FakeTransport(object):
-    rng = FakeRng()
     local_version = 'SSH-2.0-paramiko_1.0'
     remote_version = 'SSH-2.0-lame'
     local_kex_init = 'local-kex-init'
@@ -91,10 +91,11 @@ class KexTest (unittest.TestCase):
     K = 14730343317708716439807310032871972459448364195094179797249681733965528989482751523943515690110179031004049109375612685505881911274101441415545039654102474376472240501616988799699744135291070488314748284283496055223852115360852283821334858541043710301057312858051901453919067023103730011648890038847384890504
 
     def setUp(self):
-        pass
+        self._original_urandom = os.urandom
+        os.urandom = dummy_urandom
 
     def tearDown(self):
-        pass
+        os.urandom = self._original_urandom
 
     def test_1_group1_client(self):
         transport = FakeTransport()

tests/test_pkey.py

@@ -22,9 +22,10 @@ Some unit tests for public/private key objects.
 
 from binascii import hexlify
 import unittest
+
 from paramiko import RSAKey, DSSKey, ECDSAKey, Message, util
 from paramiko.py3compat import StringIO, byte_chr, b, bytes
-from paramiko.common import rng
+
 from tests.util import test_path
 
 # from openssh's ssh-keygen
@@ -166,7 +167,7 @@ class KeyTest (unittest.TestCase):
     def test_8_sign_rsa(self):
         # verify that the rsa private key can sign and verify
         key = RSAKey.from_private_key_file(test_path('test_rsa.key'))
-        msg = key.sign_ssh_data(rng, b'ice weasels')
+        msg = key.sign_ssh_data(b'ice weasels')
         self.assertTrue(type(msg) is Message)
         msg.rewind()
         self.assertEqual('ssh-rsa', msg.get_text())
@@ -179,7 +180,7 @@ class KeyTest (unittest.TestCase):
     def test_9_sign_dss(self):
         # verify that the dss private key can sign and verify
         key = DSSKey.from_private_key_file(test_path('test_dss.key'))
-        msg = key.sign_ssh_data(rng, b'ice weasels')
+        msg = key.sign_ssh_data(b'ice weasels')
         self.assertTrue(type(msg) is Message)
         msg.rewind()
         self.assertEqual('ssh-dss', msg.get_text())
@@ -193,13 +194,13 @@ class KeyTest (unittest.TestCase):
 
     def test_A_generate_rsa(self):
         key = RSAKey.generate(1024)
-        msg = key.sign_ssh_data(rng, b'jerri blank')
+        msg = key.sign_ssh_data(b'jerri blank')
         msg.rewind()
         self.assertTrue(key.verify_ssh_sig(b'jerri blank', msg))
 
     def test_B_generate_dss(self):
         key = DSSKey.generate(1024)
-        msg = key.sign_ssh_data(rng, b'jerri blank')
+        msg = key.sign_ssh_data(b'jerri blank')
         msg.rewind()
         self.assertTrue(key.verify_ssh_sig(b'jerri blank', msg))
 
@@ -240,7 +241,7 @@ class KeyTest (unittest.TestCase):
     def test_13_sign_ecdsa(self):
         # verify that the rsa private key can sign and verify
         key = ECDSAKey.from_private_key_file(test_path('test_ecdsa.key'))
-        msg = key.sign_ssh_data(rng, b'ice weasels')
+        msg = key.sign_ssh_data(b'ice weasels')
         self.assertTrue(type(msg) is Message)
         msg.rewind()
         self.assertEqual('ecdsa-sha2-nistp256', msg.get_text())

tests/test_util.py

@@ -153,12 +153,6 @@ class UtilTest(ParamikoTest):
         finally:
             os.unlink('hostfile.temp')
 
-    def test_6_random(self):
-        from paramiko.common import rng
-        # just verify that we can pull out 32 bytes and not get an exception.
-        x = rng.read(32)
-        self.assertEqual(len(x), 32)
-
     def test_7_host_config_expose_issue_33(self):
         test_config_file = """
 Host www13.*