Date: Sun, 28 Nov 1999 01:24:20 -0500 From: Dan Moschuk <dan@freebsd.org> To: freebsd-audit@freebsd.org Subject: Last random PID patch before commit Message-ID: <19991128012420.A48334@spirit.jaded.net>
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Here's the last functionality change before I commit this. I doubt that using
random() to generate the key used to shuffle the ARC4 algorithm is the
absolute best way of doing it, but, It Works(tm). The other option I looked
at was read_random(), but I'm not 100% certain that it will have built up
sufficient entropy by the time the code is called (usually at bootup).
At any rate...
Index: i386/conf/files.i386
===================================================================
RCS file: /home/ncvs/src/sys/i386/conf/files.i386,v
retrieving revision 1.281
diff -u -r1.281 files.i386
--- files.i386 1999/11/25 20:45:45 1.281
+++ files.i386 1999/11/28 06:04:52
@@ -373,6 +373,7 @@
isa/syscons_isa.c optional sc
isa/vga_isa.c optional vga
kern/subr_diskmbr.c standard
+libkern/arc4random.c standard
libkern/bcd.c standard
libkern/divdi3.c standard
libkern/index.c standard
Index: kern/kern_fork.c
===================================================================
RCS file: /home/ncvs/src/sys/kern/kern_fork.c,v
retrieving revision 1.69
diff -u -r1.69 kern_fork.c
--- kern_fork.c 1999/11/19 21:29:03 1.69
+++ kern_fork.c 1999/11/28 06:05:02
@@ -142,6 +142,9 @@
int nprocs = 1; /* process 0 */
static int nextpid = 0;
+static int randompid = 0;
+SYSCTL_INT(_kern, OID_AUTO, randompid, CTLFLAG_RW, &randompid, 0, "");
+
int
fork1(p1, flags, procp)
struct proc *p1;
@@ -262,8 +265,8 @@
* restart somewhat above 0, as the low-numbered procs
* tend to include daemons that don't exit.
*/
- if (nextpid >= PID_MAX) {
- nextpid = 100;
+ if (nextpid >= PID_MAX || randompid) {
+ nextpid = (randompid) ? arc4random() % PID_MAX : 100;
pidchecked = 0;
}
if (nextpid >= pidchecked) {
Index: libkern/arc4random.c
===================================================================
RCS file: arc4random.c
diff -N arc4random.c
--- /dev/null Sat Nov 27 21:16:45 1999
+++ arc4random.c Sat Nov 27 22:05:05 1999
@@ -0,0 +1,95 @@
+/*-
+ * 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
+ *
+ * $FreeBSD$
+ */
+
+#include <sys/libkern.h>
+#include <sys/time.h>
+
+static u_int8_t arc4_i, arc4_j;
+static int arc4_initialized = 0;
+static u_int8_t arc4_sbox[256];
+
+static void arc4_init __P((void));
+static u_int8_t arc4_randbyte __P((void));
+static __inline void arc4_swap __P((u_int8_t *, u_int8_t *));
+
+static __inline void
+arc4_swap(a, b)
+ u_int8_t *a;
+ u_int8_t *b;
+{
+ u_int8_t c;
+
+ c = *a;
+ *a = *b;
+ *b = c;
+}
+
+/*
+ * Initialize our S-box to its beginning defaults.
+ */
+static void
+arc4_init(void)
+{
+ struct timespec ts;
+ u_int8_t key[256];
+ int n;
+
+ for (n = 0; n < 256; n++)
+ arc4_sbox[n] = (u_int8_t) n;
+
+ 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_swap(&arc4_sbox[n], &arc4_sbox[arc4_j]);
+ }
+ 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();
+
+ ret = arc4_randbyte();
+ ret |= arc4_randbyte() << 8;
+ ret |= arc4_randbyte() << 16;
+ ret |= arc4_randbyte() << 24;
+
+ return ret;
+}
Index: sys/libkern.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/libkern.h,v
retrieving revision 1.18
diff -u -r1.18 libkern.h
--- libkern.h 1999/11/21 04:26:47 1.18
+++ libkern.h 1999/11/28 06:05:29
@@ -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));
--
Dan Moschuk (TFreak!dan@freebsd.org)
"Cure for global warming: One giant heatsink and dual fans!"
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