Date: Sun, 28 Nov 1999 17:45:16 -0500 From: Dan Moschuk <dan@FreeBSD.ORG> To: Mike Smith <msmith@FreeBSD.ORG> Cc: Warner Losh <imp@village.org>, cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: Re: cvs commit: src/sys/i386/conf files.i386 src/sys/kern kern_fork.c src/sys/libkern arc4random.c src/sys/sys libkern.h Message-ID: <19991128174516.B11396@spirit.jaded.net> In-Reply-To: <199911282015.MAA00314@mass.cdrom.com>; from msmith@FreeBSD.ORG on Sun, Nov 28, 1999 at 12:15:23PM -0800 References: <199911281929.MAA86006@harmony.village.org> <199911282015.MAA00314@mass.cdrom.com>
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| > Reviewed, but not completely approved by imp.... The main problem
| > with this, like I said in other mail, is it not using the /dev/random
| > entropy pool for this.
|
| I actually effectively vetoed this commit (on IRC) for it's failure to do
| just that. I expect Dan to pay close attention to the feedback and DTRT
| (which should include using the libc arcfour code as well, if he's not
| already).
This patch should address the concerns. Note that I am not using arc4random()
from libc, it contains functions which we don't need inside the kernel.
Index: arc4random.c
===================================================================
RCS file: /home/ncvs/src/sys/libkern/arc4random.c,v
retrieving revision 1.1
diff -u -r1.1 arc4random.c
--- arc4random.c 1999/11/28 17:51:08 1.1
+++ arc4random.c 1999/11/28 22:38:22
@@ -11,12 +11,16 @@
*/
#include <sys/libkern.h>
-#include <sys/time.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];
+extern u_int read_random (void *, u_int);
+
static __inline void
arc4_swap(u_int8_t *a, u_int8_t *b)
{
@@ -28,29 +32,38 @@
}
/*
- * Initialize our S-box to its beginning defaults.
+ * Stir our S-box.
*/
static void
-arc4_init(void)
+arc4_randomstir (void)
{
- struct timespec ts;
u_int8_t key[256];
- int n;
+ int r, n;
- for (n = 0; n < 256; n++)
- arc4_sbox[n] = (u_int8_t) n;
+ r = read_random(key, sizeof(key));
+ for (n = r; n < sizeof(key); n++)
+ key[n] = key[n % r];
- nanotime(&ts);
- srandom(ts.tv_sec ^ ts.tv_nsec);
for (n = 0; n < 256; n++)
- key[n] = random() % 256;
-
- arc4_i = arc4_j = 0;
- for (n = 0; n < 256; n++)
{
- arc4_j = arc4_j + arc4_sbox[n] + key[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;
}
@@ -79,11 +92,17 @@
/* 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;
+ arc4_numruns++;
return ret;
}
--
Dan Moschuk (TFreak!dan@freebsd.org)
"Cure for global warming: One giant heatsink and dual fans!"
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