/*-
* Copyright (c) 2017 W. Dean Freeman
* Copyright (c) 2013-2015 Mark R V Murray
* 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.
*
*/
/*
* This implementation of Fortuna is based on the descriptions found in
* ISBN 978-0-470-47424-2 "Cryptography Engineering" by Ferguson, Schneier
* and Kohno ("FS&K").
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/limits.h>
#ifdef _KERNEL
#include <sys/fail.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/random.h>
#include <sys/sdt.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <machine/cpu.h>
#else /* !_KERNEL */
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <threads.h>
#include "unit_test.h"
#endif /* _KERNEL */
#include <crypto/chacha20/chacha.h>
#include <crypto/rijndael/rijndael-api-fst.h>
#include <crypto/sha2/sha256.h>
#include <dev/random/hash.h>
#include <dev/random/randomdev.h>
#ifdef _KERNEL
#include <dev/random/random_harvestq.h>
#endif
#include <dev/random/uint128.h>
#include <dev/random/fortuna.h>
/* Defined in FS&K */
#define RANDOM_FORTUNA_NPOOLS 32 /* The number of accumulation pools */
#define RANDOM_FORTUNA_DEFPOOLSIZE 64 /* The default pool size/length for a (re)seed */
#define RANDOM_FORTUNA_MAX_READ (1 << 20) /* Max bytes from AES before rekeying */
#define RANDOM_FORTUNA_BLOCKS_PER_KEY (1 << 16) /* Max blocks from AES before rekeying */
CTASSERT(RANDOM_FORTUNA_BLOCKS_PER_KEY * RANDOM_BLOCKSIZE ==
RANDOM_FORTUNA_MAX_READ);
/*
* The allowable range of RANDOM_FORTUNA_DEFPOOLSIZE. The default value is above.
* Making RANDOM_FORTUNA_DEFPOOLSIZE too large will mean a long time between reseeds,
* and too small may compromise initial security but get faster reseeds.
*/
#define RANDOM_FORTUNA_MINPOOLSIZE 16
#define RANDOM_FORTUNA_MAXPOOLSIZE INT_MAX
CTASSERT(RANDOM_FORTUNA_MINPOOLSIZE <= RANDOM_FORTUNA_DEFPOOLSIZE);
CTASSERT(RANDOM_FORTUNA_DEFPOOLSIZE <= RANDOM_FORTUNA_MAXPOOLSIZE);
/* This algorithm (and code) presumes that RANDOM_KEYSIZE is twice as large as RANDOM_BLOCKSIZE */
CTASSERT(RANDOM_BLOCKSIZE == sizeof(uint128_t));
CTASSERT(RANDOM_KEYSIZE == 2*RANDOM_BLOCKSIZE);
/* Probes for dtrace(1) */
#ifdef _KERNEL
SDT_PROVIDER_DECLARE(random);
SDT_PROVIDER_DEFINE(random);
SDT_PROBE_DEFINE2(random, fortuna, event_processor, debug, "u_int", "struct fs_pool *");
#endif /* _KERNEL */
/*
* This is the beastie that needs protecting. It contains all of the
* state that we are excited about. Exactly one is instantiated.
*/
static struct fortuna_state {
struct fs_pool { /* P_i */
u_int fsp_length; /* Only the first one is used by Fortuna */
struct randomdev_hash fsp_hash;
} fs_pool[RANDOM_FORTUNA_NPOOLS];
u_int fs_reseedcount; /* ReseedCnt */
uint128_t fs_counter; /* C */
union randomdev_key fs_key; /* K */
u_int fs_minpoolsize; /* Extras */
/* Extras for the OS */
#ifdef _KERNEL
/* For use when 'pacing' the reseeds */
sbintime_t fs_lasttime;
#endif
/* Reseed lock */
mtx_t fs_mtx;
} fortuna_state;
/*
* This knob enables or disables the "Concurrent Reads" Fortuna feature.
*
* The benefit of Concurrent Reads is improved concurrency in Fortuna. That is
* reflected in two related aspects:
*
* 1. Concurrent full-rate devrandom readers can achieve similar throughput to
* a single reader thread (at least up to a modest number of cores; the
* non-concurrent design falls over at 2 readers).
*
* 2. The rand_harvestq process spends much less time spinning when one or more
* readers is processing a large request. Partially this is due to
* rand_harvestq / ra_event_processor design, which only passes one event at
* a time to the underlying algorithm. Each time, Fortuna must take its
* global state mutex, potentially blocking on a reader. Our adaptive
* mutexes assume that a lock holder currently on CPU will release the lock
* quickly, and spin if the owning thread is currently running.
*
* (There is no reason rand_harvestq necessarily has to use the same lock as
* the generator, or that it must necessarily drop and retake locks
* repeatedly, but that is the current status quo.)
*
* The concern is that the reduced lock scope might results in a less safe
* random(4) design. However, the reduced-lock scope design is still
* fundamentally Fortuna. This is discussed below.
*
* Fortuna Read() only needs mutual exclusion between readers to correctly
* update the shared read-side state: C, the 128-bit counter; and K, the
* current cipher/PRF key.
*
* In the Fortuna design, the global counter C should provide an independent
* range of values per request.
*
* Under lock, we can save a copy of C on the stack, and increment the global C
* by the number of blocks a Read request will require.
*
* Still under lock, we can save a copy of the key K on the stack, and then
* perform the usual key erasure K' <- Keystream(C, K, ...). This does require
* generating 256 bits (32 bytes) of cryptographic keystream output with the
* global lock held, but that's all; none of the API keystream generation must
* be performed under lock.
*
* At this point, we may unlock.
*
* Some example timelines below (to oversimplify, all requests are in units of
* native blocks, and the keysize happens to be equal or less to the native
* blocksize of the underlying cipher, and the same sequence of two requests
* arrive in the same order). The possibly expensive consumer keystream
* generation portion is marked with '**'.
*
* Status Quo fortuna_read() Reduced-scope locking
* ------------------------- ---------------------
* C=C_0, K=K_0 C=C_0, K=K_0
* <Thr 1 requests N blocks> <Thr 1 requests N blocks>
* 1:Lock() 1:Lock()
* <Thr 2 requests M blocks> <Thr 2 requests M blocks>
* 1:GenBytes() 1:stack_C := C_0
* 1: Keystream(C_0, K_0, N) 1:stack_K := K_0
* 1: <N blocks generated>** 1:C' := C_0 + N
* 1: C' := C_0 + N 1:K' := Keystream(C', K_0, 1)
* 1: <- Keystream 1: <1 block generated>
* 1: K' := Keystream(C', K_0, 1) 1: C'' := C' + 1
* 1: <1 block generated> 1: <- Keystream
* 1: C'' := C' + 1 1:Unlock()
* 1: <- Keystream
* 1: <- GenBytes()
* 1:Unlock()
*
* Just prior to unlock, shared state is identical:
* ------------------------------------------------
* C'' == C_0 + N + 1 C'' == C_0 + N + 1
* K' == keystream generated from K' == keystream generated from
* C_0 + N, K_0. C_0 + N, K_0.
* K_0 has been erased. K_0 has been erased.
*
* After both designs unlock, the 2nd reader is unblocked.
*
* 2:Lock() 2:Lock()
* 2:GenBytes() 2:stack_C' := C''
* 2: Keystream(C'', K', M) 2:stack_K' := K'
* 2: <M blocks generated>** 2:C''' := C'' + M
* 2: C''' := C'' + M 2:K'' := Keystream(C''', K', 1)
* 2: <- Keystream 2: <1 block generated>
* 2: K'' := Keystream(C''', K', 1) 2: C'''' := C''' + 1
* 2: <1 block generated> 2: <- Keystream
* 2: C'''' := C''' + 1 2:Unlock()
* 2: <- Keystream
* 2: <- GenBytes()
* 2:Unlock()
*
* Just prior to unlock, global state is identical:
* ------------------------------------------------------
*
* C'''' == (C_0 + N + 1) + M + 1 C'''' == (C_0 + N + 1) + M + 1
* K'' == keystream generated from K'' == keystream generated from
* C_0 + N + 1 + M, K'. C_0 + N + 1 + M, K'.
* K' has been erased. K' has been erased.
*
* Finally, in the new design, the two consumer threads can finish the
* remainder of the generation at any time (including simultaneously):
*
* 1: GenBytes()
* 1: Keystream(stack_C, stack_K, N)
* 1: <N blocks generated>**
* 1: <- Keystream
* 1: <- GenBytes
* 1:ExplicitBzero(stack_C, stack_K)
*
* 2: GenBytes()
* 2: Keystream(stack_C', stack_K', M)
* 2: <M blocks generated>**
* 2: <- Keystream
* 2: <- GenBytes
* 2:ExplicitBzero(stack_C', stack_K')
*
* The generated user keystream for both threads is identical between the two
* implementations:
*
* 1: Keystream(C_0, K_0, N) 1: Keystream(stack_C, stack_K, N)
* 2: Keystream(C'', K', M) 2: Keystream(stack_C', stack_K', M)
*
* (stack_C == C_0; stack_K == K_0; stack_C' == C''; stack_K' == K'.)
*/
static bool fortuna_concurrent_read __read_frequently = true;
#ifdef _KERNEL
static struct sysctl_ctx_list random_clist;
RANDOM_CHECK_UINT(fs_minpoolsize, RANDOM_FORTUNA_MINPOOLSIZE, RANDOM_FORTUNA_MAXPOOLSIZE);
#else
static uint8_t zero_region[RANDOM_ZERO_BLOCKSIZE];
#endif
static void random_fortuna_pre_read(void);
static void random_fortuna_read(uint8_t *, size_t);
static bool random_fortuna_seeded(void);
static bool random_fortuna_seeded_internal(void);
static void random_fortuna_process_event(struct harvest_event *);
static void random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount);
#ifdef RANDOM_LOADABLE
static
#endif
const struct random_algorithm random_alg_context = {
.ra_ident = "Fortuna",
.ra_pre_read = random_fortuna_pre_read,
.ra_read = random_fortuna_read,
.ra_seeded = random_fortuna_seeded,
.ra_event_processor = random_fortuna_process_event,
.ra_poolcount = RANDOM_FORTUNA_NPOOLS,
};
/* ARGSUSED */
static void
random_fortuna_init_alg(void *unused __unused)
{
int i;
#ifdef _KERNEL
struct sysctl_oid *random_fortuna_o;
#endif
#ifdef RANDOM_LOADABLE
p_random_alg_context = &random_alg_context;
#endif
RANDOM_RESEED_INIT_LOCK();
/*
* Fortuna parameters. Do not adjust these unless you have
* have a very good clue about what they do!
*/
fortuna_state.fs_minpoolsize = RANDOM_FORTUNA_DEFPOOLSIZE;
#ifdef _KERNEL
fortuna_state.fs_lasttime = 0;
random_fortuna_o = SYSCTL_ADD_NODE(&random_clist,
SYSCTL_STATIC_CHILDREN(_kern_random),
OID_AUTO, "fortuna", CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"Fortuna Parameters");
SYSCTL_ADD_PROC(&random_clist,
SYSCTL_CHILDREN(random_fortuna_o), OID_AUTO, "minpoolsize",
CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE,
&fortuna_state.fs_minpoolsize, RANDOM_FORTUNA_DEFPOOLSIZE,
random_check_uint_fs_minpoolsize, "IU",
"Minimum pool size necessary to cause a reseed");
KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0 at startup"));
SYSCTL_ADD_BOOL(&random_clist, SYSCTL_CHILDREN(random_fortuna_o),
OID_AUTO, "concurrent_read", CTLFLAG_RDTUN,
&fortuna_concurrent_read, 0, "If non-zero, enable "
"feature to improve concurrent Fortuna performance.");
#endif
/*-
* FS&K - InitializePRNG()
* - P_i = \epsilon
* - ReseedCNT = 0
*/
for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
fortuna_state.fs_pool[i].fsp_length = 0;
}
fortuna_state.fs_reseedcount = 0;
/*-
* FS&K - InitializeGenerator()
* - C = 0
* - K = 0
*/
fortuna_state.fs_counter = UINT128_ZERO;
explicit_bzero(&fortuna_state.fs_key, sizeof(fortuna_state.fs_key));
}
SYSINIT(random_alg, SI_SUB_RANDOM, SI_ORDER_SECOND, random_fortuna_init_alg,
NULL);
/*-
* FS&K - AddRandomEvent()
* Process a single stochastic event off the harvest queue
*/
static void
random_fortuna_process_event(struct harvest_event *event)
{
u_int pl;
RANDOM_RESEED_LOCK();
/*-
* FS&K - P_i = P_i|<harvested stuff>
* Accumulate the event into the appropriate pool
* where each event carries the destination information.
*
* The hash_init() and hash_finish() calls are done in
* random_fortuna_pre_read().
*
* We must be locked against pool state modification which can happen
* during accumulation/reseeding and reading/regating.
*/
pl = event->he_destination % RANDOM_FORTUNA_NPOOLS;
/*
* If a VM generation ID changes (clone and play or VM rewind), we want
* to incorporate that as soon as possible. Override destingation pool
* for immediate next use.
*/
if (event->he_source == RANDOM_PURE_VMGENID)
pl = 0;
/*
* We ignore low entropy static/counter fields towards the end of the
* he_event structure in order to increase measurable entropy when
* conducting SP800-90B entropy analysis measurements of seed material
* fed into PRNG.
* -- wdf
*/
KASSERT(event->he_size <= sizeof(event->he_entropy),
("%s: event->he_size: %hhu > sizeof(event->he_entropy): %zu\n",
__func__, event->he_size, sizeof(event->he_entropy)));
randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
&event->he_somecounter, sizeof(event->he_somecounter));
randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
event->he_entropy, event->he_size);
/*-
* Don't wrap the length. This is a "saturating" add.
* XXX: FIX!!: We don't actually need lengths for anything but fs_pool[0],
* but it's been useful debugging to see them all.
*/
fortuna_state.fs_pool[pl].fsp_length = MIN(RANDOM_FORTUNA_MAXPOOLSIZE,
fortuna_state.fs_pool[pl].fsp_length +
sizeof(event->he_somecounter) + event->he_size);
RANDOM_RESEED_UNLOCK();
}
/*-
* FS&K - Reseed()
* This introduces new key material into the output generator.
* Additionally it increments the output generator's counter
* variable C. When C > 0, the output generator is seeded and
* will deliver output.
* The entropy_data buffer passed is a very specific size; the
* product of RANDOM_FORTUNA_NPOOLS and RANDOM_KEYSIZE.
*/
static void
random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount)
{
struct randomdev_hash context;
uint8_t hash[RANDOM_KEYSIZE];
const void *keymaterial;
size_t keysz;
bool seeded;
RANDOM_RESEED_ASSERT_LOCK_OWNED();
seeded = random_fortuna_seeded_internal();
if (seeded) {
randomdev_getkey(&fortuna_state.fs_key, &keymaterial, &keysz);
KASSERT(keysz == RANDOM_KEYSIZE, ("%s: key size %zu not %u",
__func__, keysz, (unsigned)RANDOM_KEYSIZE));
}
/*-
* FS&K - K = Hd(K|s) where Hd(m) is H(H(0^512|m))
* - C = C + 1
*/
randomdev_hash_init(&context);
randomdev_hash_iterate(&context, zero_region, RANDOM_ZERO_BLOCKSIZE);
if (seeded)
randomdev_hash_iterate(&context, keymaterial, keysz);
randomdev_hash_iterate(&context, entropy_data, RANDOM_KEYSIZE*blockcount);
randomdev_hash_finish(&context, hash);
randomdev_hash_init(&context);
randomdev_hash_iterate(&context, hash, RANDOM_KEYSIZE);
randomdev_hash_finish(&context, hash);
randomdev_encrypt_init(&fortuna_state.fs_key, hash);
explicit_bzero(hash, sizeof(hash));
/* Unblock the device if this is the first time we are reseeding. */
if (uint128_is_zero(fortuna_state.fs_counter))
randomdev_unblock();
uint128_increment(&fortuna_state.fs_counter);
}
/*-
* FS&K - RandomData() (Part 1)
* Used to return processed entropy from the PRNG. There is a pre_read
* required to be present (but it can be a stub) in order to allow
* specific actions at the begin of the read.
*/
void
random_fortuna_pre_read(void)
{
#ifdef _KERNEL
sbintime_t now;
#endif
struct randomdev_hash context;
uint32_t s[RANDOM_FORTUNA_NPOOLS*RANDOM_KEYSIZE_WORDS];
uint8_t temp[RANDOM_KEYSIZE];
u_int i;
KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0"));
RANDOM_RESEED_LOCK();
#ifdef _KERNEL
/* FS&K - Use 'getsbinuptime()' to prevent reseed-spamming. */
now = getsbinuptime();
#endif
if (fortuna_state.fs_pool[0].fsp_length < fortuna_state.fs_minpoolsize
#ifdef _KERNEL
/*
* FS&K - Use 'getsbinuptime()' to prevent reseed-spamming, but do
* not block initial seeding (fs_lasttime == 0).
*/
|| (__predict_true(fortuna_state.fs_lasttime != 0) &&
now - fortuna_state.fs_lasttime <= SBT_1S/10)
#endif
) {
RANDOM_RESEED_UNLOCK();
return;
}
#ifdef _KERNEL
/*
* When set, pretend we do not have enough entropy to reseed yet.
*/
KFAIL_POINT_CODE(DEBUG_FP, random_fortuna_pre_read, {
if (RETURN_VALUE != 0) {
RANDOM_RESEED_UNLOCK();
return;
}
});
#endif
#ifdef _KERNEL
fortuna_state.fs_lasttime = now;
#endif
/* FS&K - ReseedCNT = ReseedCNT + 1 */
fortuna_state.fs_reseedcount++;
/* s = \epsilon at start */
for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
/* FS&K - if Divides(ReseedCnt, 2^i) ... */
if ((fortuna_state.fs_reseedcount % (1 << i)) == 0) {
/*-
* FS&K - temp = (P_i)
* - P_i = \epsilon
* - s = s|H(temp)
*/
randomdev_hash_finish(&fortuna_state.fs_pool[i].fsp_hash, temp);
randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
fortuna_state.fs_pool[i].fsp_length = 0;
randomdev_hash_init(&context);
randomdev_hash_iterate(&context, temp, RANDOM_KEYSIZE);
randomdev_hash_finish(&context, s + i*RANDOM_KEYSIZE_WORDS);
} else
break;
}
#ifdef _KERNEL
SDT_PROBE2(random, fortuna, event_processor, debug, fortuna_state.fs_reseedcount, fortuna_state.fs_pool);
#endif
/* FS&K */
random_fortuna_reseed_internal(s, i);
RANDOM_RESEED_UNLOCK();
/* Clean up and secure */
explicit_bzero(s, sizeof(s));
explicit_bzero(temp, sizeof(temp));
}
/*
* This is basically GenerateBlocks() from FS&K.
*
* It differs in two ways:
*
* 1. Chacha20 is tolerant of non-block-multiple request sizes, so we do not
* need to handle any remainder bytes specially and can just pass the length
* directly to the PRF construction; and
*
* 2. Chacha20 is a 512-bit block size cipher (whereas AES has 128-bit block
* size, regardless of key size). This means Chacha does not require re-keying
* every 1MiB. This is implied by the math in FS&K 9.4 and mentioned
* explicitly in the conclusion, "If we had a block cipher with a 256-bit [or
* greater] block size, then the collisions would not have been an issue at
* all" (p. 144).
*
* 3. In conventional ("locked") mode, we produce a maximum of PAGE_SIZE output
* at a time before dropping the lock, to not bully the lock especially. This
* has been the status quo since 2015 (r284959).
*
* The upstream caller random_fortuna_read is responsible for zeroing out
* sensitive buffers provided as parameters to this routine.
*/
enum {
FORTUNA_UNLOCKED = false,
FORTUNA_LOCKED = true
};
static void
random_fortuna_genbytes(uint8_t *buf, size_t bytecount,
uint8_t newkey[static RANDOM_KEYSIZE], uint128_t *p_counter,
union randomdev_key *p_key, bool locked)
{
uint8_t remainder_buf[RANDOM_BLOCKSIZE];
size_t chunk_size;
if (locked)
RANDOM_RESEED_ASSERT_LOCK_OWNED();
else
RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
/*
* Easy case: don't have to worry about bullying the global mutex,
* don't have to worry about rekeying Chacha; API is byte-oriented.
*/
if (!locked && random_chachamode) {
randomdev_keystream(p_key, p_counter, buf, bytecount);
return;
}
if (locked) {
/*
* While holding the global lock, limit PRF generation to
* mitigate, but not eliminate, bullying symptoms.
*/
chunk_size = PAGE_SIZE;
} else {
/*
* 128-bit block ciphers like AES must be re-keyed at 1MB
* intervals to avoid unacceptable statistical differentiation
* from true random data (FS&K 9.4, p. 143-144).
*/
MPASS(!random_chachamode);
chunk_size = RANDOM_FORTUNA_MAX_READ;
}
chunk_size = MIN(bytecount, chunk_size);
if (!random_chachamode)
chunk_size = rounddown(chunk_size, RANDOM_BLOCKSIZE);
while (bytecount >= chunk_size && chunk_size > 0) {
randomdev_keystream(p_key, p_counter, buf, chunk_size);
buf += chunk_size;
bytecount -= chunk_size;
/* We have to rekey if there is any data remaining to be
* generated, in two scenarios:
*
* locked: we need to rekey before we unlock and release the
* global state to another consumer; or
*
* unlocked: we need to rekey because we're in AES mode and are
* required to rekey at chunk_size==1MB. But we do not need to
* rekey during the last trailing <1MB chunk.
*/
if (bytecount > 0) {
if (locked || chunk_size == RANDOM_FORTUNA_MAX_READ) {
randomdev_keystream(p_key, p_counter, newkey,
RANDOM_KEYSIZE);
randomdev_encrypt_init(p_key, newkey);
}
/*
* If we're holding the global lock, yield it briefly
* now.
*/
if (locked) {
RANDOM_RESEED_UNLOCK();
RANDOM_RESEED_LOCK();
}
/*
* At the trailing end, scale down chunk_size from 1MB or
* PAGE_SIZE to all remaining full blocks (AES) or all
* remaining bytes (Chacha).
*/
if (bytecount < chunk_size) {
if (random_chachamode)
chunk_size = bytecount;
else if (bytecount >= RANDOM_BLOCKSIZE)
chunk_size = rounddown(bytecount,
RANDOM_BLOCKSIZE);
else
break;
}
}
}
/*
* Generate any partial AES block remaining into a temporary buffer and
* copy the desired substring out.
*/
if (bytecount > 0) {
MPASS(!random_chachamode);
randomdev_keystream(p_key, p_counter, remainder_buf,
sizeof(remainder_buf));
}
/*
* In locked mode, re-key global K before dropping the lock, which we
* don't need for memcpy/bzero below.
*/
if (locked) {
randomdev_keystream(p_key, p_counter, newkey, RANDOM_KEYSIZE);
randomdev_encrypt_init(p_key, newkey);
RANDOM_RESEED_UNLOCK();
}
if (bytecount > 0) {
memcpy(buf, remainder_buf, bytecount);
explicit_bzero(remainder_buf, sizeof(remainder_buf));
}
}
/*
* Handle only "concurrency-enabled" Fortuna reads to simplify logic.
*
* Caller (random_fortuna_read) is responsible for zeroing out sensitive
* buffers provided as parameters to this routine.
*/
static void
random_fortuna_read_concurrent(uint8_t *buf, size_t bytecount,
uint8_t newkey[static RANDOM_KEYSIZE])
{
union randomdev_key key_copy;
uint128_t counter_copy;
size_t blockcount;
MPASS(fortuna_concurrent_read);
/*
* Compute number of blocks required for the PRF request ('delta C').
* We will step the global counter 'C' by this number under lock, and
* then actually consume the counter values outside the lock.
*
* This ensures that contemporaneous but independent requests for
* randomness receive distinct 'C' values and thus independent PRF
* results.
*/
if (random_chachamode) {
blockcount = howmany(bytecount, CHACHA_BLOCKLEN);
} else {
blockcount = howmany(bytecount, RANDOM_BLOCKSIZE);
/*
* Need to account for the additional blocks generated by
* rekeying when updating the global fs_counter.
*/
blockcount += RANDOM_KEYS_PER_BLOCK *
(blockcount / RANDOM_FORTUNA_BLOCKS_PER_KEY);
}
RANDOM_RESEED_LOCK();
KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
/*
* Save the original counter and key values that will be used as the
* PRF for this particular consumer.
*/
memcpy(&counter_copy, &fortuna_state.fs_counter, sizeof(counter_copy));
memcpy(&key_copy, &fortuna_state.fs_key, sizeof(key_copy));
/*
* Step the counter as if we had generated 'bytecount' blocks for this
* consumer. I.e., ensure that the next consumer gets an independent
* range of counter values once we drop the global lock.
*/
uint128_add64(&fortuna_state.fs_counter, blockcount);
/*
* We still need to Rekey the global 'K' between independent calls;
* this is no different from conventional Fortuna. Note that
* 'randomdev_keystream()' will step the fs_counter 'C' appropriately
* for the blocks needed for the 'newkey'.
*
* (This is part of PseudoRandomData() in FS&K, 9.4.4.)
*/
randomdev_keystream(&fortuna_state.fs_key, &fortuna_state.fs_counter,
newkey, RANDOM_KEYSIZE);
randomdev_encrypt_init(&fortuna_state.fs_key, newkey);
/*
* We have everything we need to generate a unique PRF for this
* consumer without touching global state.
*/
RANDOM_RESEED_UNLOCK();
random_fortuna_genbytes(buf, bytecount, newkey, &counter_copy,
&key_copy, FORTUNA_UNLOCKED);
RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
explicit_bzero(&counter_copy, sizeof(counter_copy));
explicit_bzero(&key_copy, sizeof(key_copy));
}
/*-
* FS&K - RandomData() (Part 2)
* Main read from Fortuna, continued. May be called multiple times after
* the random_fortuna_pre_read() above.
*
* The supplied buf MAY not be a multiple of RANDOM_BLOCKSIZE in size; it is
* the responsibility of the algorithm to accommodate partial block reads, if a
* block output mode is used.
*/
void
random_fortuna_read(uint8_t *buf, size_t bytecount)
{
uint8_t newkey[RANDOM_KEYSIZE];
if (fortuna_concurrent_read) {
random_fortuna_read_concurrent(buf, bytecount, newkey);
goto out;
}
RANDOM_RESEED_LOCK();
KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
random_fortuna_genbytes(buf, bytecount, newkey,
&fortuna_state.fs_counter, &fortuna_state.fs_key, FORTUNA_LOCKED);
/* Returns unlocked */
RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
out:
explicit_bzero(newkey, sizeof(newkey));
}
#ifdef _KERNEL
static bool block_seeded_status = false;
SYSCTL_BOOL(_kern_random, OID_AUTO, block_seeded_status, CTLFLAG_RWTUN,
&block_seeded_status, 0,
"If non-zero, pretend Fortuna is in an unseeded state. By setting "
"this as a tunable, boot can be tested as if the random device is "
"unavailable.");
#endif
static bool
random_fortuna_seeded_internal(void)
{
return (!uint128_is_zero(fortuna_state.fs_counter));
}
static bool
random_fortuna_seeded(void)
{
#ifdef _KERNEL
if (block_seeded_status)
return (false);
#endif
if (__predict_true(random_fortuna_seeded_internal()))
return (true);
/*
* Maybe we have enough entropy in the zeroth pool but just haven't
* kicked the initial seed step. Do so now.
*/
random_fortuna_pre_read();
return (random_fortuna_seeded_internal());
}
