2 * Copyright (c) 2017 W. Dean Freeman
3 * Copyright (c) 2013-2015 Mark R V Murray
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer
11 * in this position and unchanged.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 * This implementation of Fortuna is based on the descriptions found in
31 * ISBN 978-0-470-47424-2 "Cryptography Engineering" by Ferguson, Schneier
35 #include <sys/cdefs.h>
36 __FBSDID("$FreeBSD$");
38 #include <sys/param.h>
39 #include <sys/limits.h>
43 #include <sys/kernel.h>
45 #include <sys/malloc.h>
46 #include <sys/mutex.h>
47 #include <sys/random.h>
49 #include <sys/sysctl.h>
50 #include <sys/systm.h>
52 #include <machine/cpu.h>
61 #include "unit_test.h"
64 #include <crypto/chacha20/chacha.h>
65 #include <crypto/rijndael/rijndael-api-fst.h>
66 #include <crypto/sha2/sha256.h>
68 #include <dev/random/hash.h>
69 #include <dev/random/randomdev.h>
71 #include <dev/random/random_harvestq.h>
73 #include <dev/random/uint128.h>
74 #include <dev/random/fortuna.h>
77 #define RANDOM_FORTUNA_NPOOLS 32 /* The number of accumulation pools */
78 #define RANDOM_FORTUNA_DEFPOOLSIZE 64 /* The default pool size/length for a (re)seed */
79 #define RANDOM_FORTUNA_MAX_READ (1 << 20) /* Max bytes from AES before rekeying */
80 #define RANDOM_FORTUNA_BLOCKS_PER_KEY (1 << 16) /* Max blocks from AES before rekeying */
81 CTASSERT(RANDOM_FORTUNA_BLOCKS_PER_KEY * RANDOM_BLOCKSIZE ==
82 RANDOM_FORTUNA_MAX_READ);
85 * The allowable range of RANDOM_FORTUNA_DEFPOOLSIZE. The default value is above.
86 * Making RANDOM_FORTUNA_DEFPOOLSIZE too large will mean a long time between reseeds,
87 * and too small may compromise initial security but get faster reseeds.
89 #define RANDOM_FORTUNA_MINPOOLSIZE 16
90 #define RANDOM_FORTUNA_MAXPOOLSIZE INT_MAX
91 CTASSERT(RANDOM_FORTUNA_MINPOOLSIZE <= RANDOM_FORTUNA_DEFPOOLSIZE);
92 CTASSERT(RANDOM_FORTUNA_DEFPOOLSIZE <= RANDOM_FORTUNA_MAXPOOLSIZE);
94 /* This algorithm (and code) presumes that RANDOM_KEYSIZE is twice as large as RANDOM_BLOCKSIZE */
95 CTASSERT(RANDOM_BLOCKSIZE == sizeof(uint128_t));
96 CTASSERT(RANDOM_KEYSIZE == 2*RANDOM_BLOCKSIZE);
98 /* Probes for dtrace(1) */
100 SDT_PROVIDER_DECLARE(random);
101 SDT_PROVIDER_DEFINE(random);
102 SDT_PROBE_DEFINE2(random, fortuna, event_processor, debug, "u_int", "struct fs_pool *");
106 * This is the beastie that needs protecting. It contains all of the
107 * state that we are excited about. Exactly one is instantiated.
109 static struct fortuna_state {
110 struct fs_pool { /* P_i */
111 u_int fsp_length; /* Only the first one is used by Fortuna */
112 struct randomdev_hash fsp_hash;
113 } fs_pool[RANDOM_FORTUNA_NPOOLS];
114 u_int fs_reseedcount; /* ReseedCnt */
115 uint128_t fs_counter; /* C */
116 union randomdev_key fs_key; /* K */
117 u_int fs_minpoolsize; /* Extras */
118 /* Extras for the OS */
120 /* For use when 'pacing' the reseeds */
121 sbintime_t fs_lasttime;
128 * This knob enables or disables Concurrent Reads. The plan is to turn it on
129 * by default sometime before 13.0 branches.
131 * The benefit is improved concurrency in Fortuna. That is reflected in two
134 * 1. Concurrent devrandom readers can achieve similar throughput to a single
137 * 2. The rand_harvestq process spends much less time spinning when one or more
138 * readers is processing a large request. Partially this is due to
139 * rand_harvestq / ra_event_processor design, which only passes one event at
140 * a time to the underlying algorithm. Each time, Fortuna must take its
141 * global state mutex, potentially blocking on a reader. Our adaptive
142 * mutexes assume that a lock holder currently on CPU will release the lock
143 * quickly, and spin if the owning thread is currently running.
145 * The concern is that the reduced lock scope might results in a less safe
146 * random(4) design. However, the reduced-lock scope design is still
147 * fundamentally Fortuna. This is discussed below.
149 * Fortuna Read() only needs mutual exclusion between readers to correctly
150 * update the shared read-side state: just C, the 128-bit counter, and K, the
151 * current cipher key.
153 * In the Fortuna design, the global counter C should provide an independent
154 * range of values per generator (CTR-mode cipher or similar) invocation.
156 * Under lock, we can save a copy of C on the stack, and increment the global C
157 * by the number of blocks a Read request will require.
159 * Still under lock, we can save a copy of the key K on the stack, and then
160 * perform the usual key erasure K' <- Keystream(C, K, ...). This does require
161 * generating 256 bits (32 bytes) of cryptographic keystream output with the
162 * global lock held, but that's all; none of the user keystream generation must
163 * be performed under lock.
165 * At this point, we may unlock.
167 * Some example timelines below (to oversimplify, all requests are in units of
168 * native blocks, and the keysize happens to be equal or less to the native
169 * blocksize of the underlying cipher, and the same sequence of two requests
170 * arrive in the same order). The possibly expensive consumer keystream
171 * generation portion is marked with '**'.
173 * Status Quo fortuna_read() Reduced-scope locking
174 * ------------------------- ---------------------
175 * C=C_0, K=K_0 C=C_0, K=K_0
176 * <Thr 1 requests N blocks> <Thr 1 requests N blocks>
178 * <Thr 2 requests M blocks> <Thr 2 requests M blocks>
179 * 1:GenBytes() 1:stack_C := C_0
180 * 1: Keystream(C_0, K_0, N) 1:stack_K := K_0
181 * 1: <N blocks generated>** 1:C' := C_0 + N
182 * 1: C' := C_0 + N 1:K' := Keystream(C', K_0, 1)
183 * 1: <- Keystream 1: <1 block generated>
184 * 1: K' := Keystream(C', K_0, 1) 1: C'' := C' + 1
185 * 1: <1 block generated> 1: <- Keystream
186 * 1: C'' := C' + 1 1:Unlock()
191 * Just prior to unlock, shared state is identical:
192 * ------------------------------------------------
193 * C'' == C_0 + N + 1 C'' == C_0 + N + 1
194 * K' == keystream generated from K' == keystream generated from
195 * C_0 + N, K_0. C_0 + N, K_0.
196 * K_0 has been erased. K_0 has been erased.
198 * After both designs unlock, the 2nd reader is unblocked.
201 * 2:GenBytes() 2:stack_C' := C''
202 * 2: Keystream(C'', K', M) 2:stack_K' := K'
203 * 2: <M blocks generated>** 2:C''' := C'' + M
204 * 2: C''' := C'' + M 2:K'' := Keystream(C''', K', 1)
205 * 2: <- Keystream 2: <1 block generated>
206 * 2: K'' := Keystream(C''', K', 1) 2: C'''' := C''' + 1
207 * 2: <1 block generated> 2: <- Keystream
208 * 2: C'''' := C''' + 1 2:Unlock()
213 * Just prior to unlock, shared state is still identical:
214 * ------------------------------------------------------
216 * C'''' == (C_0 + N + 1) + M + 1 C'''' == (C_0 + N + 1) + M + 1
217 * K'' == keystream generated from K'' == keystream generated from
218 * C_0 + N + 1 + M, K'. C_0 + N + 1 + M, K'.
219 * K' has been erased. K' has been erased.
221 * Finally, in the new design, the two consumer threads can finish the
222 * remainder of the generation at any time (including simultaneously):
225 * 1: Keystream(stack_C, stack_K, N)
226 * 1: <N blocks generated>**
229 * 1:ExplicitBzero(stack_C, stack_K)
232 * 2: Keystream(stack_C', stack_K', M)
233 * 2: <M blocks generated>**
236 * 2:ExplicitBzero(stack_C', stack_K')
238 * The generated user keystream for both threads is identical between the two
241 * 1: Keystream(C_0, K_0, N) 1: Keystream(stack_C, stack_K, N)
242 * 2: Keystream(C'', K', M) 2: Keystream(stack_C', stack_K', M)
244 * (stack_C == C_0; stack_K == K_0; stack_C' == C''; stack_K' == K'.)
246 static bool fortuna_concurrent_read __read_frequently = false;
249 static struct sysctl_ctx_list random_clist;
250 RANDOM_CHECK_UINT(fs_minpoolsize, RANDOM_FORTUNA_MINPOOLSIZE, RANDOM_FORTUNA_MAXPOOLSIZE);
252 static uint8_t zero_region[RANDOM_ZERO_BLOCKSIZE];
255 static void random_fortuna_pre_read(void);
256 static void random_fortuna_read(uint8_t *, size_t);
257 static bool random_fortuna_seeded(void);
258 static bool random_fortuna_seeded_internal(void);
259 static void random_fortuna_process_event(struct harvest_event *);
260 static void random_fortuna_init_alg(void *);
261 static void random_fortuna_deinit_alg(void *);
263 static void random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount);
265 struct random_algorithm random_alg_context = {
266 .ra_ident = "Fortuna",
267 .ra_init_alg = random_fortuna_init_alg,
268 .ra_deinit_alg = random_fortuna_deinit_alg,
269 .ra_pre_read = random_fortuna_pre_read,
270 .ra_read = random_fortuna_read,
271 .ra_seeded = random_fortuna_seeded,
272 .ra_event_processor = random_fortuna_process_event,
273 .ra_poolcount = RANDOM_FORTUNA_NPOOLS,
278 random_fortuna_init_alg(void *unused __unused)
282 struct sysctl_oid *random_fortuna_o;
285 RANDOM_RESEED_INIT_LOCK();
287 * Fortuna parameters. Do not adjust these unless you have
288 * have a very good clue about what they do!
290 fortuna_state.fs_minpoolsize = RANDOM_FORTUNA_DEFPOOLSIZE;
292 fortuna_state.fs_lasttime = 0;
293 random_fortuna_o = SYSCTL_ADD_NODE(&random_clist,
294 SYSCTL_STATIC_CHILDREN(_kern_random),
295 OID_AUTO, "fortuna", CTLFLAG_RW, 0,
296 "Fortuna Parameters");
297 SYSCTL_ADD_PROC(&random_clist,
298 SYSCTL_CHILDREN(random_fortuna_o), OID_AUTO,
299 "minpoolsize", CTLTYPE_UINT | CTLFLAG_RWTUN,
300 &fortuna_state.fs_minpoolsize, RANDOM_FORTUNA_DEFPOOLSIZE,
301 random_check_uint_fs_minpoolsize, "IU",
302 "Minimum pool size necessary to cause a reseed");
303 KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0 at startup"));
305 SYSCTL_ADD_BOOL(&random_clist, SYSCTL_CHILDREN(random_fortuna_o),
306 OID_AUTO, "concurrent_read", CTLFLAG_RDTUN,
307 &fortuna_concurrent_read, 0, "If non-zero, enable "
308 "feature to improve concurrent Fortuna performance.");
312 * FS&K - InitializePRNG()
316 for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
317 randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
318 fortuna_state.fs_pool[i].fsp_length = 0;
320 fortuna_state.fs_reseedcount = 0;
322 * FS&K - InitializeGenerator()
326 fortuna_state.fs_counter = UINT128_ZERO;
327 explicit_bzero(&fortuna_state.fs_key, sizeof(fortuna_state.fs_key));
332 random_fortuna_deinit_alg(void *unused __unused)
335 RANDOM_RESEED_DEINIT_LOCK();
336 explicit_bzero(&fortuna_state, sizeof(fortuna_state));
338 sysctl_ctx_free(&random_clist);
343 * FS&K - AddRandomEvent()
344 * Process a single stochastic event off the harvest queue
347 random_fortuna_process_event(struct harvest_event *event)
351 RANDOM_RESEED_LOCK();
353 * FS&K - P_i = P_i|<harvested stuff>
354 * Accumulate the event into the appropriate pool
355 * where each event carries the destination information.
357 * The hash_init() and hash_finish() calls are done in
358 * random_fortuna_pre_read().
360 * We must be locked against pool state modification which can happen
361 * during accumulation/reseeding and reading/regating.
363 pl = event->he_destination % RANDOM_FORTUNA_NPOOLS;
365 * We ignore low entropy static/counter fields towards the end of the
366 * he_event structure in order to increase measurable entropy when
367 * conducting SP800-90B entropy analysis measurements of seed material
371 KASSERT(event->he_size <= sizeof(event->he_entropy),
372 ("%s: event->he_size: %hhu > sizeof(event->he_entropy): %zu\n",
373 __func__, event->he_size, sizeof(event->he_entropy)));
374 randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
375 &event->he_somecounter, sizeof(event->he_somecounter));
376 randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
377 event->he_entropy, event->he_size);
380 * Don't wrap the length. This is a "saturating" add.
381 * XXX: FIX!!: We don't actually need lengths for anything but fs_pool[0],
382 * but it's been useful debugging to see them all.
384 fortuna_state.fs_pool[pl].fsp_length = MIN(RANDOM_FORTUNA_MAXPOOLSIZE,
385 fortuna_state.fs_pool[pl].fsp_length +
386 sizeof(event->he_somecounter) + event->he_size);
387 RANDOM_RESEED_UNLOCK();
392 * This introduces new key material into the output generator.
393 * Additionally it increments the output generator's counter
394 * variable C. When C > 0, the output generator is seeded and
395 * will deliver output.
396 * The entropy_data buffer passed is a very specific size; the
397 * product of RANDOM_FORTUNA_NPOOLS and RANDOM_KEYSIZE.
400 random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount)
402 struct randomdev_hash context;
403 uint8_t hash[RANDOM_KEYSIZE];
404 const void *keymaterial;
408 RANDOM_RESEED_ASSERT_LOCK_OWNED();
410 seeded = random_fortuna_seeded_internal();
412 randomdev_getkey(&fortuna_state.fs_key, &keymaterial, &keysz);
413 KASSERT(keysz == RANDOM_KEYSIZE, ("%s: key size %zu not %u",
414 __func__, keysz, (unsigned)RANDOM_KEYSIZE));
418 * FS&K - K = Hd(K|s) where Hd(m) is H(H(0^512|m))
421 randomdev_hash_init(&context);
422 randomdev_hash_iterate(&context, zero_region, RANDOM_ZERO_BLOCKSIZE);
424 randomdev_hash_iterate(&context, keymaterial, keysz);
425 randomdev_hash_iterate(&context, entropy_data, RANDOM_KEYSIZE*blockcount);
426 randomdev_hash_finish(&context, hash);
427 randomdev_hash_init(&context);
428 randomdev_hash_iterate(&context, hash, RANDOM_KEYSIZE);
429 randomdev_hash_finish(&context, hash);
430 randomdev_encrypt_init(&fortuna_state.fs_key, hash);
431 explicit_bzero(hash, sizeof(hash));
432 /* Unblock the device if this is the first time we are reseeding. */
433 if (uint128_is_zero(fortuna_state.fs_counter))
435 uint128_increment(&fortuna_state.fs_counter);
439 * FS&K - RandomData() (Part 1)
440 * Used to return processed entropy from the PRNG. There is a pre_read
441 * required to be present (but it can be a stub) in order to allow
442 * specific actions at the begin of the read.
445 random_fortuna_pre_read(void)
450 struct randomdev_hash context;
451 uint32_t s[RANDOM_FORTUNA_NPOOLS*RANDOM_KEYSIZE_WORDS];
452 uint8_t temp[RANDOM_KEYSIZE];
455 KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0"));
456 RANDOM_RESEED_LOCK();
458 /* FS&K - Use 'getsbinuptime()' to prevent reseed-spamming. */
459 now = getsbinuptime();
462 if (fortuna_state.fs_pool[0].fsp_length < fortuna_state.fs_minpoolsize
465 * FS&K - Use 'getsbinuptime()' to prevent reseed-spamming, but do
466 * not block initial seeding (fs_lasttime == 0).
468 || (__predict_true(fortuna_state.fs_lasttime != 0) &&
469 now - fortuna_state.fs_lasttime <= SBT_1S/10)
472 RANDOM_RESEED_UNLOCK();
478 * When set, pretend we do not have enough entropy to reseed yet.
480 KFAIL_POINT_CODE(DEBUG_FP, random_fortuna_pre_read, {
481 if (RETURN_VALUE != 0) {
482 RANDOM_RESEED_UNLOCK();
489 fortuna_state.fs_lasttime = now;
492 /* FS&K - ReseedCNT = ReseedCNT + 1 */
493 fortuna_state.fs_reseedcount++;
494 /* s = \epsilon at start */
495 for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
496 /* FS&K - if Divides(ReseedCnt, 2^i) ... */
497 if ((fortuna_state.fs_reseedcount % (1 << i)) == 0) {
499 * FS&K - temp = (P_i)
503 randomdev_hash_finish(&fortuna_state.fs_pool[i].fsp_hash, temp);
504 randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
505 fortuna_state.fs_pool[i].fsp_length = 0;
506 randomdev_hash_init(&context);
507 randomdev_hash_iterate(&context, temp, RANDOM_KEYSIZE);
508 randomdev_hash_finish(&context, s + i*RANDOM_KEYSIZE_WORDS);
513 SDT_PROBE2(random, fortuna, event_processor, debug, fortuna_state.fs_reseedcount, fortuna_state.fs_pool);
516 random_fortuna_reseed_internal(s, i);
517 RANDOM_RESEED_UNLOCK();
519 /* Clean up and secure */
520 explicit_bzero(s, sizeof(s));
521 explicit_bzero(temp, sizeof(temp));
525 * This is basically GenerateBlocks() from FS&K.
527 * It differs in two ways:
529 * 1. Chacha20 is tolerant of non-block-multiple request sizes, so we do not
530 * need to handle any remainder bytes specially and can just pass the length
531 * directly to the PRF construction; and
533 * 2. Chacha20 is a 512-bit block size cipher (whereas AES has 128-bit block
534 * size, regardless of key size). This means Chacha does not require re-keying
535 * every 1MiB. This is implied by the math in FS&K 9.4 and mentioned
536 * explicitly in the conclusion, "If we had a block cipher with a 256-bit [or
537 * greater] block size, then the collisions would not have been an issue at
540 * 3. In conventional ("locked") mode, we produce a maximum of PAGE_SIZE output
541 * at a time before dropping the lock, to not bully the lock especially. This
542 * has been the status quo since 2015 (r284959).
544 * The upstream caller random_fortuna_read is responsible for zeroing out
545 * sensitive buffers provided as parameters to this routine.
548 FORTUNA_UNLOCKED = false,
549 FORTUNA_LOCKED = true
552 random_fortuna_genbytes(uint8_t *buf, size_t bytecount,
553 uint8_t newkey[static RANDOM_KEYSIZE], uint128_t *p_counter,
554 union randomdev_key *p_key, bool locked)
556 uint8_t remainder_buf[RANDOM_BLOCKSIZE];
560 RANDOM_RESEED_ASSERT_LOCK_OWNED();
562 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
565 * Easy case: don't have to worry about bullying the global mutex,
566 * don't have to worry about rekeying Chacha; API is byte-oriented.
568 if (!locked && random_chachamode) {
569 randomdev_keystream(p_key, p_counter, buf, bytecount);
575 * While holding the global lock, limit PRF generation to
576 * mitigate, but not eliminate, bullying symptoms.
578 chunk_size = PAGE_SIZE;
581 * 128-bit block ciphers like AES must be re-keyed at 1MB
582 * intervals to avoid unacceptable statistical differentiation
583 * from true random data (FS&K 9.4, p. 143-144).
585 MPASS(!random_chachamode);
586 chunk_size = RANDOM_FORTUNA_MAX_READ;
589 chunk_size = MIN(bytecount, chunk_size);
590 if (!random_chachamode)
591 chunk_size = rounddown(chunk_size, RANDOM_BLOCKSIZE);
593 while (bytecount >= chunk_size && chunk_size > 0) {
594 randomdev_keystream(p_key, p_counter, buf, chunk_size);
597 bytecount -= chunk_size;
599 /* We have to rekey if there is any data remaining to be
600 * generated, in two scenarios:
602 * locked: we need to rekey before we unlock and release the
603 * global state to another consumer; or
605 * unlocked: we need to rekey because we're in AES mode and are
606 * required to rekey at chunk_size==1MB. But we do not need to
607 * rekey during the last trailing <1MB chunk.
610 if (locked || chunk_size == RANDOM_FORTUNA_MAX_READ) {
611 randomdev_keystream(p_key, p_counter, newkey,
613 randomdev_encrypt_init(p_key, newkey);
617 * If we're holding the global lock, yield it briefly
621 RANDOM_RESEED_UNLOCK();
622 RANDOM_RESEED_LOCK();
626 * At the trailing end, scale down chunk_size from 1MB or
627 * PAGE_SIZE to all remaining full blocks (AES) or all
628 * remaining bytes (Chacha).
630 if (bytecount < chunk_size) {
631 if (random_chachamode)
632 chunk_size = bytecount;
633 else if (bytecount >= RANDOM_BLOCKSIZE)
634 chunk_size = rounddown(bytecount,
643 * Generate any partial AES block remaining into a temporary buffer and
644 * copy the desired substring out.
647 MPASS(!random_chachamode);
649 randomdev_keystream(p_key, p_counter, remainder_buf,
650 sizeof(remainder_buf));
654 * In locked mode, re-key global K before dropping the lock, which we
655 * don't need for memcpy/bzero below.
658 randomdev_keystream(p_key, p_counter, newkey, RANDOM_KEYSIZE);
659 randomdev_encrypt_init(p_key, newkey);
660 RANDOM_RESEED_UNLOCK();
664 memcpy(buf, remainder_buf, bytecount);
665 explicit_bzero(remainder_buf, sizeof(remainder_buf));
671 * Handle only "concurrency-enabled" Fortuna reads to simplify logic.
673 * Caller (random_fortuna_read) is responsible for zeroing out sensitive
674 * buffers provided as parameters to this routine.
677 random_fortuna_read_concurrent(uint8_t *buf, size_t bytecount,
678 uint8_t newkey[static RANDOM_KEYSIZE])
680 union randomdev_key key_copy;
681 uint128_t counter_copy;
684 MPASS(fortuna_concurrent_read);
687 * Compute number of blocks required for the PRF request ('delta C').
688 * We will step the global counter 'C' by this number under lock, and
689 * then actually consume the counter values outside the lock.
691 * This ensures that contemporaneous but independent requests for
692 * randomness receive distinct 'C' values and thus independent PRF
695 if (random_chachamode) {
696 blockcount = howmany(bytecount, CHACHA_BLOCKLEN);
698 blockcount = howmany(bytecount, RANDOM_BLOCKSIZE);
701 * Need to account for the additional blocks generated by
702 * rekeying when updating the global fs_counter.
704 blockcount += RANDOM_KEYS_PER_BLOCK *
705 (blockcount / RANDOM_FORTUNA_BLOCKS_PER_KEY);
708 RANDOM_RESEED_LOCK();
709 KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
712 * Save the original counter and key values that will be used as the
713 * PRF for this particular consumer.
715 memcpy(&counter_copy, &fortuna_state.fs_counter, sizeof(counter_copy));
716 memcpy(&key_copy, &fortuna_state.fs_key, sizeof(key_copy));
719 * Step the counter as if we had generated 'bytecount' blocks for this
720 * consumer. I.e., ensure that the next consumer gets an independent
721 * range of counter values once we drop the global lock.
723 uint128_add64(&fortuna_state.fs_counter, blockcount);
726 * We still need to Rekey the global 'K' between independent calls;
727 * this is no different from conventional Fortuna. Note that
728 * 'randomdev_keystream()' will step the fs_counter 'C' appropriately
729 * for the blocks needed for the 'newkey'.
731 * (This is part of PseudoRandomData() in FS&K, 9.4.4.)
733 randomdev_keystream(&fortuna_state.fs_key, &fortuna_state.fs_counter,
734 newkey, RANDOM_KEYSIZE);
735 randomdev_encrypt_init(&fortuna_state.fs_key, newkey);
738 * We have everything we need to generate a unique PRF for this
739 * consumer without touching global state.
741 RANDOM_RESEED_UNLOCK();
743 random_fortuna_genbytes(buf, bytecount, newkey, &counter_copy,
744 &key_copy, FORTUNA_UNLOCKED);
745 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
747 explicit_bzero(&counter_copy, sizeof(counter_copy));
748 explicit_bzero(&key_copy, sizeof(key_copy));
752 * FS&K - RandomData() (Part 2)
753 * Main read from Fortuna, continued. May be called multiple times after
754 * the random_fortuna_pre_read() above.
756 * The supplied buf MAY not be a multiple of RANDOM_BLOCKSIZE in size; it is
757 * the responsibility of the algorithm to accommodate partial block reads, if a
758 * block output mode is used.
761 random_fortuna_read(uint8_t *buf, size_t bytecount)
763 uint8_t newkey[RANDOM_KEYSIZE];
765 if (fortuna_concurrent_read) {
766 random_fortuna_read_concurrent(buf, bytecount, newkey);
770 RANDOM_RESEED_LOCK();
771 KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
773 random_fortuna_genbytes(buf, bytecount, newkey,
774 &fortuna_state.fs_counter, &fortuna_state.fs_key, FORTUNA_LOCKED);
775 /* Returns unlocked */
776 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
779 explicit_bzero(newkey, sizeof(newkey));
783 static bool block_seeded_status = false;
784 SYSCTL_BOOL(_kern_random, OID_AUTO, block_seeded_status, CTLFLAG_RWTUN,
785 &block_seeded_status, 0,
786 "If non-zero, pretend Fortuna is in an unseeded state. By setting "
787 "this as a tunable, boot can be tested as if the random device is "
792 random_fortuna_seeded_internal(void)
794 return (!uint128_is_zero(fortuna_state.fs_counter));
798 random_fortuna_seeded(void)
802 if (block_seeded_status)
806 if (__predict_true(random_fortuna_seeded_internal()))
810 * Maybe we have enough entropy in the zeroth pool but just haven't
811 * kicked the initial seed step. Do so now.
813 random_fortuna_pre_read();
815 return (random_fortuna_seeded_internal());