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libc arc4_stir: use only kern.arandom sysctl

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The sysctl cannot fail. If it does fail on some FreeBSD derivative or
after some future change, just abort() so that the problem will be found
and fixed.

It's preferable to provide an arc4random() function that cannot fail and
cannot return poor quality random data. While abort() is not normally
suitable for a library, it makes sense here.

Reviewed by:	ed, jonathan, markm
MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D8077
This commit is contained in:
Ed Maste 2016-10-03 13:12:44 +00:00
parent 6a3536aaee
commit 5c1ea1fcd0
1 changed files with 5 additions and 23 deletions
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28
lib/libc/gen/arc4random.c
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@ -137,35 +137,17 @@ arc4_sysctl(u_char *buf, size_t size)
static void
arc4_stir(void)
{
int done, fd, i;
struct {
struct timeval tv;
pid_t pid;
u_char rnd[KEYSIZE];
} rdat;
u_char rdat[KEYSIZE];
int i;
if (!rs_initialized) {
arc4_init();
rs_initialized = 1;
}
done = 0;
if (arc4_sysctl((u_char *)&rdat, KEYSIZE) == KEYSIZE)
done = 1;
if (!done) {
fd = _open(RANDOMDEV, O_RDONLY | O_CLOEXEC, 0);
if (fd >= 0) {
if (_read(fd, &rdat, KEYSIZE) == KEYSIZE)
done = 1;
(void)_close(fd);
}
}
if (!done) {
(void)gettimeofday(&rdat.tv, NULL);
rdat.pid = getpid();
/* We'll just take whatever was on the stack too... */
}
if (arc4_sysctl(rdat, KEYSIZE) != KEYSIZE)
abort(); /* Random sysctl cannot fail. */
arc4_addrandom((u_char *)&rdat, KEYSIZE);
arc4_addrandom(rdat, KEYSIZE);
/*
* Discard early keystream, as per recommendations in: