/*-
* Copyright (c) 2017 The FreeBSD Foundation
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer
* in this position and unchanged.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/types.h>
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
#include <sys/linker.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/random.h>
#include <sys/smp.h>
#include <sys/time.h>
#include <crypto/chacha20/chacha.h>
#include <crypto/sha2/sha256.h>
#include <dev/random/randomdev.h>
#include <machine/cpu.h>
#define CHACHA20_RESEED_BYTES 65536
#define CHACHA20_RESEED_SECONDS 300
#define CHACHA20_KEYBYTES 32
#define CHACHA20_BUFFER_SIZE 64
CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN);
int arc4rand_iniseed_state = ARC4_ENTR_NONE;
MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures");
struct chacha20_s {
struct mtx mtx;
int numbytes;
time_t t_reseed;
u_int8_t m_buffer[CHACHA20_BUFFER_SIZE];
struct chacha_ctx ctx;
} __aligned(CACHE_LINE_SIZE);
static struct chacha20_s *chacha20inst = NULL;
#define CHACHA20_FOREACH(_chacha20) \
for (_chacha20 = &chacha20inst[0]; \
_chacha20 <= &chacha20inst[mp_maxid]; \
_chacha20++)
/*
* Mix up the current context.
*/
static void
chacha20_randomstir(struct chacha20_s *chacha20)
{
struct timeval tv_now;
u_int8_t key[CHACHA20_KEYBYTES];
if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) {
SHA256_CTX ctx;
uint64_t cc;
uint32_t fver;
if (!arc4random_bypassed_before_seeding) {
arc4random_bypassed_before_seeding = true;
if (!random_bypass_disable_warnings)
printf("arc4random: WARNING: initial seeding "
"bypassed the cryptographic random device "
"because it was not yet seeded and the "
"knob 'bypass_before_seeding' was "
"enabled.\n");
}
/* Last ditch effort to inject something in a bad condition. */
cc = get_cyclecount();
SHA256_Init(&ctx);
SHA256_Update(&ctx, key, sizeof(key));
SHA256_Update(&ctx, &cc, sizeof(cc));
fver = __FreeBSD_version;
SHA256_Update(&ctx, &fver, sizeof(fver));
_Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH,
"make sure 256 bits is still 256 bits");
SHA256_Final(key, &ctx);
} else {
/*
* If the loader(8) did not have an entropy stash from the
* previous shutdown to load, then we will block. The answer is
* to make sure there is an entropy stash at shutdown time.
*
* On the other hand, if the random_bypass_before_seeding knob
* was set and we landed in this branch, we know this won't
* block because we know the random device is seeded.
*/
read_random(key, CHACHA20_KEYBYTES);
}
getmicrouptime(&tv_now);
mtx_lock(&chacha20->mtx);
chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8);
chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec);
/* Reset for next reseed cycle. */
chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS;
chacha20->numbytes = 0;
mtx_unlock(&chacha20->mtx);
}
/*
* Initialize the contexts.
*/
static void
chacha20_init(void)
{
struct chacha20_s *chacha20;
chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s),
M_CHACHA20RANDOM, M_NOWAIT | M_ZERO);
KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error"));
CHACHA20_FOREACH(chacha20) {
mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF);
chacha20->t_reseed = -1;
chacha20->numbytes = 0;
explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE);
explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx));
}
}
SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL);
static void
chacha20_uninit(void)
{
struct chacha20_s *chacha20;
CHACHA20_FOREACH(chacha20)
mtx_destroy(&chacha20->mtx);
free(chacha20inst, M_CHACHA20RANDOM);
}
SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL);
/*
* MPSAFE
*/
void
arc4rand(void *ptr, u_int len, int reseed)
{
struct chacha20_s *chacha20;
struct timeval tv;
u_int length;
u_int8_t *p;
if (__predict_false(reseed ||
(arc4rand_iniseed_state == ARC4_ENTR_HAVE &&
atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED))))
CHACHA20_FOREACH(chacha20)
chacha20_randomstir(chacha20);
getmicrouptime(&tv);
chacha20 = &chacha20inst[curcpu];
/* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */
if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed))
chacha20_randomstir(chacha20);
p = ptr;
mtx_lock(&chacha20->mtx);
while (len) {
length = MIN(CHACHA20_BUFFER_SIZE, len);
chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length);
p += length;
len -= length;
chacha20->numbytes += length;
if (chacha20->numbytes > CHACHA20_RESEED_BYTES) {
mtx_unlock(&chacha20->mtx);
chacha20_randomstir(chacha20);
mtx_lock(&chacha20->mtx);
}
}
mtx_unlock(&chacha20->mtx);
}
uint32_t
arc4random(void)
{
uint32_t ret;
arc4rand(&ret, sizeof(ret), 0);
return ret;
}
void
arc4random_buf(void *ptr, size_t len)
{
arc4rand(ptr, len, 0);
}