Re: [PATCH] rand.c updates from FreeBSD RELENG_5
This is a multi-part message in MIME format.
--------------060103030002050400010004
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Joerg Sonnenberger wrote:
> On Wed, May 12, 2004 at 07:29:09PM -0500, William M. Grim wrote:
>
>>@@ -85,14 +88,24 @@
>> value is provided, the functions are automatically
>> seeded with a value of 1.
>> .Pp
>>+The
>>+.Fn sranddev
>>+function initializes a seed using the
>>+.Xr random 4
>>+random number device which returns good random numbers,
>>+suitable for cryptographic use.
>
>
> This part of the patch is out-of-sync.
Thanks for pointing that out Joerg. I will learn to pay more attention
to things like this.
I have redone the rand.3 patch and attached it. I tested it against
what is currently in DFly's CVS and did not witness any problems. Let
me know how it goes.
Thanks again,
Mike
--------------060103030002050400010004
Content-Type: text/plain;
name="rand.c.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="rand.c.patch"
--- rand.c 2004-05-12 15:43:31.000000000 -0500
+++ rand.c.new 2004-05-12 15:42:39.000000000 -0500
@@ -32,14 +32,20 @@
*
* Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
*
- * $FreeBSD: src/lib/libc/stdlib/rand.c,v 1.2.2.1 2001/03/05 11:33:57 obrien Exp $
+ * $FreeBSD: src/lib/libc/stdlib/rand.c,v 1.15 2001/03/05 11:33:57 ache Exp $
* $DragonFly: src/lib/libc/stdlib/rand.c,v 1.2 2003/06/17 04:26:46 dillon Exp $
- *
- * @(#)rand.c 8.1 (Berkeley) 6/14/93
*/
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93";
+#endif /* LIBC_SCCS and not lint */
+#include <sys/cdefs.h>
+
+#include <sys/time.h> /* for sranddev() */
#include <sys/types.h>
+#include <fcntl.h> /* for sranddev() */
#include <stdlib.h>
+#include <unistd.h> /* for sranddev() */
#ifdef TEST
#include <stdio.h>
@@ -48,7 +54,34 @@
static int
do_rand(unsigned long *ctx)
{
+#ifdef USE_WEAK_SEEDING
+/*
+ * Historic implementation compatibility.
+ * The random sequences do not vary much with the seed,
+ * even with overflowing.
+ */
return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
+#else /* !USE_WEAK_SEEDING */
+/*
+ * Compute x = (7^5 * x) mod (2^31 - 1)
+ * wihout overflowing 31 bits:
+ * (2^31 - 1) = 127773 * (7^5) + 2836
+ * From "Random number generators: good ones are hard to find",
+ * Park and Miller, Communications of the ACM, vol. 31, no. 10,
+ * October 1988, p. 1195.
+ */
+ long hi, lo, x;
+
+ /* Can't be initialized with 0, so use another value. */
+ if (*ctx == 0)
+ *ctx = 123459876;
+ hi = *ctx / 127773;
+ lo = *ctx % 127773;
+ x = 16807 * lo - 2836 * hi;
+ if (x < 0)
+ x += 0x7fffffff;
+ return ((*ctx = x) % ((u_long)RAND_MAX + 1));
+#endif /* !USE_WEAK_SEEDING */
}
@@ -56,8 +89,10 @@
rand_r(unsigned int *ctx)
{
u_long val = (u_long) *ctx;
- *ctx = do_rand(&val);
- return (int) *ctx;
+ int r = do_rand(&val);
+
+ *ctx = (unsigned int) val;
+ return (r);
}
@@ -66,7 +101,7 @@
int
rand()
{
- return do_rand(&next);
+ return (do_rand(&next));
}
void
@@ -76,6 +111,42 @@
next = seed;
}
+
+/*
+ * sranddev:
+ *
+ * Many programs choose the seed value in a totally predictable manner.
+ * This often causes problems. We seed the generator using the much more
+ * secure random(4) interface.
+ *
+ * FreeBSD chooses to use /dev/random for their seed. However, because
+ * of possible problems surrounding /dev/random, we use /dev/urandom for now,
+ * which is guaranteed not to block and will produce a "good enough" seed
+ * for us for the time being.
+ */
+void
+sranddev()
+{
+ int fd, done;
+
+ done = 0;
+ fd = _open("/dev/urandom", O_RDONLY, 0);
+ if (fd >= 0) {
+ if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next))
+ done = 1;
+ _close(fd);
+ }
+
+ if (!done) {
+ struct timeval tv;
+ unsigned long junk;
+
+ gettimeofday(&tv, NULL);
+ srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk);
+ }
+}
+
+
#ifdef TEST
main()
--------------060103030002050400010004--
討論串 (同標題文章)
完整討論串 (本文為第 16 之 18 篇)：