diff options
| author | Mark Johnston <markj@FreeBSD.org> | 2025-09-08 14:46:12 +0000 |
|---|---|---|
| committer | Mark Johnston <markj@FreeBSD.org> | 2025-09-08 15:21:43 +0000 |
| commit | 480928ae657d81e41f8c10837cd1cf0ca87b14ae (patch) | |
| tree | 468237d1c655d49f588ab930228a1c2ac006d2e6 | |
| parent | f865264f6a5eba4025c0f6284a48f383717fd74e (diff) | |
random: Exclude the timestamp from healthtest for pure sources
So-called pure sources provide entropy at regular intervals, so the
timestamp counter provides little entropy. Exclude it from health
testing for such sources.
Reviewed by: cem, emaste
MFC after: 2 weeks
Sponsored by: Stormshield
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D52233
| -rw-r--r-- | sys/dev/random/random_harvestq.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/sys/dev/random/random_harvestq.c b/sys/dev/random/random_harvestq.c index c308f6f80d59..2d7af254c52c 100644 --- a/sys/dev/random/random_harvestq.c +++ b/sys/dev/random/random_harvestq.c @@ -343,7 +343,17 @@ copy_event(uint32_t dst[static HARVESTSIZE + 1], { memset(dst, 0, sizeof(uint32_t) * (HARVESTSIZE + 1)); memcpy(dst, event->he_entropy, event->he_size); - dst[HARVESTSIZE] = event->he_somecounter; + if (event->he_source <= RANDOM_ENVIRONMENTAL_END) { + /* + * For pure entropy sources the timestamp counter is generally + * quite determinstic since samples are taken at regular + * intervals, so does not contribute much to the entropy. To + * make health tests more effective, exclude it from the sample, + * since it might otherwise defeat the health tests in a + * scenario where the source is stuck. + */ + dst[HARVESTSIZE] = event->he_somecounter; + } } static void |