Commit 6895cade authored by Kyle Evans's avatar Kyle Evans
Browse files

kern: random: drop read_rate and associated functionality

Refer to discussion in PR 230808 for a less incomplete discussion, but
the gist of this change is that we currently collect orders of magnitude
more entropy than we need.

The excess comes from bytes being read out of /dev/*random.  The default
rate at which we collect entropy without the read_rate increase is
already more than we need to recover from a compromise of an internal
state.

Reviewed by:	#csprng (cem, delphij, markm)
Differential Revision:	https://reviews.freebsd.org/D32021
parent 7bc13692
......@@ -75,8 +75,6 @@ __FBSDID("$FreeBSD$");
static void random_kthread(void);
static void random_sources_feed(void);
static u_int read_rate;
/*
* Random must initialize much earlier than epoch, but we can initialize the
* epoch code before SMP starts. Prior to SMP, we can safely bypass
......@@ -231,7 +229,7 @@ random_sources_feed(void)
uint32_t entropy[HARVESTSIZE];
struct epoch_tracker et;
struct random_sources *rrs;
u_int i, n, local_read_rate;
u_int i, n;
bool rse_warm;
rse_warm = epoch_inited;
......@@ -240,15 +238,10 @@ random_sources_feed(void)
* Step over all of live entropy sources, and feed their output
* to the system-wide RNG.
*/
local_read_rate = atomic_readandclear_32(&read_rate);
/* Perform at least one read per round */
local_read_rate = MAX(local_read_rate, 1);
/* But not exceeding RANDOM_KEYSIZE_WORDS */
local_read_rate = MIN(local_read_rate, RANDOM_KEYSIZE_WORDS);
if (rse_warm)
epoch_enter_preempt(rs_epoch, &et);
CK_LIST_FOREACH(rrs, &source_list, rrs_entries) {
for (i = 0; i < p_random_alg_context->ra_poolcount*local_read_rate; i++) {
for (i = 0; i < p_random_alg_context->ra_poolcount; 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)));
/*
......@@ -272,13 +265,6 @@ random_sources_feed(void)
explicit_bzero(entropy, sizeof(entropy));
}
void
read_rate_increment(u_int chunk)
{
atomic_add_32(&read_rate, chunk);
}
/* ARGSUSED */
static int
random_check_uint_harvestmask(SYSCTL_HANDLER_ARGS)
......
......@@ -42,8 +42,6 @@ struct harvest_event {
uint8_t he_source; /* origin of the entropy */
};
void read_rate_increment(u_int);
#define RANDOM_HARVEST_INIT_LOCK(x) mtx_init(&harvest_context.hc_mtx, "entropy harvest mutex", NULL, MTX_SPIN)
#define RANDOM_HARVEST_LOCK(x) mtx_lock_spin(&harvest_context.hc_mtx)
#define RANDOM_HARVEST_UNLOCK(x) mtx_unlock_spin(&harvest_context.hc_mtx)
......
......@@ -187,7 +187,6 @@ int
if (error != 0)
return (error);
read_rate_increment(howmany(uio->uio_resid + 1, sizeof(uint32_t)));
total_read = 0;
/* Easy to deal with the trivial 0 byte case. */
......@@ -286,7 +285,6 @@ void
(void)randomdev_wait_until_seeded(SEEDWAIT_UNINTERRUPTIBLE);
}
read_rate_increment(roundup2(len, sizeof(uint32_t)));
p_random_alg_context->ra_read(random_buf, len);
}
......
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