Date: Fri, 6 Oct 2000 11:23:15 -0700 From: Alfred Perlstein <bright@wintelcom.net> To: Warner Losh <imp@village.org> Cc: Dmitry Valdov <dv@dv.ru>, Ruslan Ermilov <ru@sunbay.com>, Fernando Schapachnik <fpscha@via-net-works.net.ar>, security@FreeBSD.ORG Subject: Re: HERT advisory: FreeBSD IP Spoofing (fwd) Message-ID: <20001006112315.A266@fw.wintelcom.net> In-Reply-To: <20001006103657.D27736@fw.wintelcom.net>; from bright@wintelcom.net on Fri, Oct 06, 2000 at 10:36:57AM -0700 References: <Pine.BSF.3.95q.1001006163649.9906B-100000@xkis.kis.ru> <200010061713.LAA09674@harmony.village.org> <20001006103657.D27736@fw.wintelcom.net>
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* Alfred Perlstein <bright@wintelcom.net> [001006 10:37] wrote:
> * Warner Losh <imp@village.org> [001006 10:15] wrote:
> > In message <Pine.BSF.3.95q.1001006163649.9906B-100000@xkis.kis.ru> Dmitry Valdov writes:
> > : And how about 2.x branch?
> >
> > I don't think anybody has backported it yet.
>
> I'm on it.
I just booted a box, things look OK, please review as this is a bit
more complex than the other patches because of a lack of arc4 random
in 2.2.x
Index: i386/conf/files.i386
===================================================================
RCS file: /home/ncvs/src/sys/i386/conf/Attic/files.i386,v
retrieving revision 1.141.2.25
diff -u -u -r1.141.2.25 files.i386
--- i386/conf/files.i386 1999/09/05 08:10:53 1.141.2.25
+++ i386/conf/files.i386 2000/10/06 15:56:50
@@ -256,6 +256,7 @@
libkern/strncpy.c standard
libkern/udivdi3.c standard
libkern/umoddi3.c standard
+libkern/arc4random.c standard
gnu/i386/fpemul/div_small.s optional gpl_math_emulate
gnu/i386/fpemul/errors.c optional gpl_math_emulate
gnu/i386/fpemul/fpu_arith.c optional gpl_math_emulate
Index: libkern/arc4random.c
===================================================================
RCS file: arc4random.c
diff -N arc4random.c
--- /dev/null Fri Oct 6 02:19:19 2000
+++ arc4random.c Fri Oct 6 09:18:44 2000
@@ -0,0 +1,111 @@
+/*-
+ * THE BEER-WARE LICENSE
+ *
+ * <dan@FreeBSD.ORG> wrote this file. As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you
+ * think this stuff is worth it, you can buy me a beer in return.
+ *
+ * Dan Moschuk
+ *
+ * $FreeBSD: src/sys/libkern/arc4random.c,v 1.6 2000/09/11 19:34:04 jhb Exp $
+ */
+
+#include <sys/types.h>
+#include <sys/libkern.h>
+
+#define ARC4_MAXRUNS 64
+
+static u_int8_t arc4_i, arc4_j;
+static int arc4_initialized = 0;
+static int arc4_numruns = 0;
+static u_int8_t arc4_sbox[256];
+
+static __inline void
+arc4_swap(u_int8_t *a, u_int8_t *b)
+{
+ u_int8_t c;
+
+ c = *a;
+ *a = *b;
+ *b = c;
+}
+
+/*
+ * Stir our S-box.
+ */
+static void
+arc4_randomstir (void)
+{
+ u_int8_t key[256];
+ int r, n;
+
+ /* r = read_random(key, sizeof(key)); */
+ r = 0; /* XXX MarkM - revisit this when /dev/random is done */
+ /* if r == 0 || -1, just use what was on the stack */
+ if (r > 0)
+ {
+ for (n = r; n < sizeof(key); n++)
+ key[n] = key[n % r];
+ }
+
+ for (n = 0; n < 256; n++)
+ {
+ arc4_j = (arc4_j + arc4_sbox[n] + key[n]) % 256;
+ arc4_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]);
+ }
+}
+
+/*
+ * Initialize our S-box to its beginning defaults.
+ */
+static void
+arc4_init(void)
+{
+ int n;
+
+ arc4_i = arc4_j = 0;
+ for (n = 0; n < 256; n++)
+ arc4_sbox[n] = (u_int8_t) n;
+
+ arc4_randomstir();
+ arc4_initialized = 1;
+}
+
+/*
+ * Generate a random byte.
+ */
+static u_int8_t
+arc4_randbyte(void)
+{
+ u_int8_t arc4_t;
+
+ arc4_i = (arc4_i + 1) % 256;
+ arc4_j = (arc4_j + arc4_sbox[arc4_i]) % 256;
+
+ arc4_swap(&arc4_sbox[arc4_i], &arc4_sbox[arc4_j]);
+
+ arc4_t = (arc4_sbox[arc4_i] + arc4_sbox[arc4_j]) % 256;
+ return arc4_sbox[arc4_t];
+}
+
+u_int32_t
+arc4random(void)
+{
+ u_int32_t ret;
+
+ /* Initialize array if needed. */
+ if (!arc4_initialized)
+ arc4_init();
+ if (++arc4_numruns > ARC4_MAXRUNS)
+ {
+ arc4_randomstir();
+ arc4_numruns = 0;
+ }
+
+ ret = arc4_randbyte();
+ ret |= arc4_randbyte() << 8;
+ ret |= arc4_randbyte() << 16;
+ ret |= arc4_randbyte() << 24;
+
+ return ret;
+}
Index: netinet/tcp_seq.h
===================================================================
RCS file: /home/ncvs/src/sys/netinet/tcp_seq.h,v
retrieving revision 1.6.4.1
diff -u -u -r1.6.4.1 tcp_seq.h
--- netinet/tcp_seq.h 1999/09/05 08:18:43 1.6.4.1
+++ netinet/tcp_seq.h 2000/10/06 15:57:39
@@ -91,7 +91,7 @@
* number in the range [0-0x3ffff] that is hard to predict.
*/
#ifndef tcp_random18
-#define tcp_random18() ((random() >> 14) & 0x3ffff)
+#define tcp_random18() (arc4random() & 0x3ffff)
#endif
#define TCP_ISSINCR (122*1024 + tcp_random18())
Index: netinet/tcp_subr.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/tcp_subr.c,v
retrieving revision 1.31.2.5
diff -u -u -r1.31.2.5 tcp_subr.c
--- netinet/tcp_subr.c 1999/09/05 08:18:43 1.31.2.5
+++ netinet/tcp_subr.c 2000/10/06 15:58:29
@@ -104,7 +104,7 @@
tcp_init()
{
- tcp_iss = random(); /* wrong, but better than a constant */
+ tcp_iss = arc4random(); /* wrong, but better than a constant */
tcp_ccgen = 1;
tcp_cleartaocache();
LIST_INIT(&tcb);
Index: sys/libkern.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/libkern.h,v
retrieving revision 1.14.2.1
diff -u -u -r1.14.2.1 libkern.h
--- sys/libkern.h 1999/09/05 08:22:31 1.14.2.1
+++ sys/libkern.h 2000/10/06 16:19:38
@@ -61,6 +61,7 @@
static __inline u_long ulmin(u_long a, u_long b) { return (a < b ? a : b); }
/* Prototypes for non-quad routines. */
+u_int32_t arc4random __P((void));
int bcmp __P((const void *, const void *, size_t));
#ifndef HAVE_INLINE_FFS
int ffs __P((int));
thanks,
--
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."
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