svn commit: r315226 - in stable/11: lib/libc/gen sys/libkern

[Xin LI]

Author: delphij
Date: Tue Mar 14 06:10:40 2017
New Revision: 315226
URL: https://svnweb.freebsd.org/changeset/base/315226

Log:
  MFC r315225:
  
  Discard first 3072 bytes of RC4 keystream, this is a bandaid
  that allows us to work on switching to a more modern PRNG.
  
  Submitted by:	Steven Chamberlain <steven pyro eu org>
  Approved by:	so

Modified:
  stable/11/lib/libc/gen/arc4random.c
  stable/11/sys/libkern/arc4random.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/lib/libc/gen/arc4random.c
==============================================================================
--- stable/11/lib/libc/gen/arc4random.c	Tue Mar 14 06:00:44 2017	(r315225)
+++ stable/11/lib/libc/gen/arc4random.c	Tue Mar 14 06:10:40 2017	(r315226)
@@ -171,7 +171,7 @@ arc4_stir(void)
 	 * Discard early keystream, as per recommendations in:
 	 * "(Not So) Random Shuffles of RC4" by Ilya Mironov.
 	 */
-	for (i = 0; i < 1024; i++)
+	for (i = 0; i < 3072; i++)
 		(void)arc4_getbyte();
 	arc4_count = 1600000;
 }

Modified: stable/11/sys/libkern/arc4random.c
==============================================================================
--- stable/11/sys/libkern/arc4random.c	Tue Mar 14 06:00:44 2017	(r315225)
+++ stable/11/sys/libkern/arc4random.c	Tue Mar 14 06:10:40 2017	(r315226)
@@ -72,11 +72,11 @@ arc4_randomstir(void)
 	/*
 	 * Throw away the first N words of output, as suggested in the
 	 * paper "Weaknesses in the Key Scheduling Algorithm of RC4"
-	 * by Fluher, Mantin, and Shamir.  (N = 256 in our case.)
+	 * by Fluher, Mantin, and Shamir.  (N = 768 in our case.)
 	 *
 	 * http://dl.acm.org/citation.cfm?id=646557.694759
 	 */
-	for (n = 0; n < 256*4; n++)
+	for (n = 0; n < 768*4; n++)
 		arc4_randbyte();
 	mtx_unlock(&arc4_mtx);
 }