Author: cem Date: Wed May 8 14:54:32 2019 New Revision: 347329 URL: https://svnweb.freebsd.org/changeset/base/347329
Log: random(4): Don't complain noisily when an entropy source is slow Mjg@ reports that RDSEED (r347239) causes a lot of logspam from this printf, and I don't feel that it is especially useful (even ratelimited). There are many other quality/quantity checks we're not performing on entropy sources; lack of high frequency availability does not disqualify a good entropy source. There is some discussion in the linked Differential about what logging might be appropriate and/or polling policy for slower TRNG sources. Please feel free to chime in if you have opinions. Reported by: mjg Reviewed by: markm, delphij Approved by: secteam(delphij) X-MFC-With: r347239 Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D20195 Modified: head/sys/dev/random/random_harvestq.c Modified: head/sys/dev/random/random_harvestq.c ============================================================================== --- head/sys/dev/random/random_harvestq.c Wed May 8 13:35:51 2019 (r347328) +++ head/sys/dev/random/random_harvestq.c Wed May 8 14:54:32 2019 (r347329) @@ -235,15 +235,19 @@ random_sources_feed(void) for (i = 0; i < p_random_alg_context->ra_poolcount*local_read_rate; i++) { n = rrs->rrs_source->rs_read(entropy, sizeof(entropy)); KASSERT((n <= sizeof(entropy)), ("%s: rs_read returned too much data (%u > %zu)", __func__, n, sizeof(entropy))); - /* It would appear that in some circumstances (e.g. virtualisation), - * the underlying hardware entropy source might not always return - * random numbers. Accept this but make a noise. If too much happens, - * can that source be trusted? + /* + * Sometimes the HW entropy source doesn't have anything + * ready for us. This isn't necessarily untrustworthy. + * We don't perform any other verification of an entropy + * source (i.e., length is allowed to be anywhere from 1 + * to sizeof(entropy), quality is unchecked, etc), so + * don't balk verbosely at slow random sources either. + * There are reports that RDSEED on x86 metal falls + * behind the rate at which we query it, for example. + * But it's still a better entropy source than RDRAND. */ - if (n == 0) { - printf("%s: rs_read for hardware device '%s' returned no entropy.\n", __func__, rrs->rrs_source->rs_ident); + if (n == 0) continue; - } random_harvest_direct(entropy, n, rrs->rrs_source->rs_source); } } _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
