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[src/trunk]: src/sys/kern Don't reject seed file entropy estimates, until one...
details: https://anonhg.NetBSD.org/src/rev/52b46a72f791
branches: trunk
changeset: 971853:52b46a72f791
user: riastradh <riastradh%NetBSD.org@localhost>
date: Wed May 06 18:31:05 2020 +0000
description:
Don't reject seed file entropy estimates, until one is nonzero.
We try to avoid counting the seed file's entropy twice, e.g. once
from the boot loader and once from rndctl via /etc/rc.d/random_seed.
But previously, if you had a /var/db/entropy-file that was deemed to
have zero entropy, that would prevent rndctl -L from _ever_ setting a
nonzero entropy estimate, even if you (say) copy a seed file over
from another machine (over a non-eavesdroppable medium) and try to
load it in with rndctl -L, e.g. via `/etc/rc.d/random_seed start'.
Now we accept the first _nonzero_ entropy estimate from a seed file.
The operator can still always trick the kernel into believing there's
entropy in the system by writing data to /dev/random, if the operator
knows something the kernel doesn't; this only affects the _automated_
seed file loading.
diffstat:
sys/kern/kern_entropy.c | 11 ++++++-----
1 files changed, 6 insertions(+), 5 deletions(-)
diffs (46 lines):
diff -r 32e7437f289c -r 52b46a72f791 sys/kern/kern_entropy.c
--- a/sys/kern/kern_entropy.c Wed May 06 18:15:40 2020 +0000
+++ b/sys/kern/kern_entropy.c Wed May 06 18:31:05 2020 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_entropy.c,v 1.10 2020/05/05 15:31:42 riastradh Exp $ */
+/* $NetBSD: kern_entropy.c,v 1.11 2020/05/06 18:31:05 riastradh Exp $ */
/*-
* Copyright (c) 2019 The NetBSD Foundation, Inc.
@@ -77,7 +77,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.10 2020/05/05 15:31:42 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_entropy.c,v 1.11 2020/05/06 18:31:05 riastradh Exp $");
#include <sys/param.h>
#include <sys/types.h>
@@ -550,7 +550,7 @@
if (E->stage >= ENTROPY_WARM)
mutex_enter(&E->lock);
seeded = E->seeded;
- E->seeded = true;
+ E->seeded = (seed->entropy > 0);
if (E->stage >= ENTROPY_WARM)
mutex_exit(&E->lock);
@@ -563,7 +563,8 @@
printf("entropy: double-seeded by bootloader\n");
seed->entropy = 0;
} else {
- printf("entropy: entering seed from bootloader\n");
+ printf("entropy: entering seed from bootloader"
+ " with %u bits of entropy\n", (unsigned)seed->entropy);
}
/* Enter it into the pool and promptly zero it. */
@@ -2197,7 +2198,7 @@
* load a seed from disk that we have already loaded
* from the bootloader, so we don't double-count it.
*/
- if (privileged) {
+ if (privileged && rdata->entropy && rdata->len) {
mutex_enter(&E->lock);
if (!E->seeded) {
entropybits = MIN(rdata->entropy,
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