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 the "Concurrent Reads" Fortuna feature.
130 * The benefit of Concurrent Reads is improved concurrency in Fortuna. That is
131 * reflected in two related aspects:
133 * 1. Concurrent full-rate devrandom readers can achieve similar throughput to
134 * a single reader thread (at least up to a modest number of cores; the
135 * non-concurrent design falls over at 2 readers).
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 * (There is no reason rand_harvestq necessarily has to use the same lock as
146 * the generator, or that it must necessarily drop and retake locks
147 * repeatedly, but that is the current status quo.)
149 * The concern is that the reduced lock scope might results in a less safe
150 * random(4) design. However, the reduced-lock scope design is still
151 * fundamentally Fortuna. This is discussed below.
153 * Fortuna Read() only needs mutual exclusion between readers to correctly
154 * update the shared read-side state: C, the 128-bit counter; and K, the
155 * current cipher/PRF key.
157 * In the Fortuna design, the global counter C should provide an independent
158 * range of values per request.
160 * Under lock, we can save a copy of C on the stack, and increment the global C
161 * by the number of blocks a Read request will require.
163 * Still under lock, we can save a copy of the key K on the stack, and then
164 * perform the usual key erasure K' <- Keystream(C, K, ...). This does require
165 * generating 256 bits (32 bytes) of cryptographic keystream output with the
166 * global lock held, but that's all; none of the API keystream generation must
167 * be performed under lock.
169 * At this point, we may unlock.
171 * Some example timelines below (to oversimplify, all requests are in units of
172 * native blocks, and the keysize happens to be equal or less to the native
173 * blocksize of the underlying cipher, and the same sequence of two requests
174 * arrive in the same order). The possibly expensive consumer keystream
175 * generation portion is marked with '**'.
177 * Status Quo fortuna_read() Reduced-scope locking
178 * ------------------------- ---------------------
179 * C=C_0, K=K_0 C=C_0, K=K_0
180 * <Thr 1 requests N blocks> <Thr 1 requests N blocks>
182 * <Thr 2 requests M blocks> <Thr 2 requests M blocks>
183 * 1:GenBytes() 1:stack_C := C_0
184 * 1: Keystream(C_0, K_0, N) 1:stack_K := K_0
185 * 1: <N blocks generated>** 1:C' := C_0 + N
186 * 1: C' := C_0 + N 1:K' := Keystream(C', K_0, 1)
187 * 1: <- Keystream 1: <1 block generated>
188 * 1: K' := Keystream(C', K_0, 1) 1: C'' := C' + 1
189 * 1: <1 block generated> 1: <- Keystream
190 * 1: C'' := C' + 1 1:Unlock()
195 * Just prior to unlock, shared state is identical:
196 * ------------------------------------------------
197 * C'' == C_0 + N + 1 C'' == C_0 + N + 1
198 * K' == keystream generated from K' == keystream generated from
199 * C_0 + N, K_0. C_0 + N, K_0.
200 * K_0 has been erased. K_0 has been erased.
202 * After both designs unlock, the 2nd reader is unblocked.
205 * 2:GenBytes() 2:stack_C' := C''
206 * 2: Keystream(C'', K', M) 2:stack_K' := K'
207 * 2: <M blocks generated>** 2:C''' := C'' + M
208 * 2: C''' := C'' + M 2:K'' := Keystream(C''', K', 1)
209 * 2: <- Keystream 2: <1 block generated>
210 * 2: K'' := Keystream(C''', K', 1) 2: C'''' := C''' + 1
211 * 2: <1 block generated> 2: <- Keystream
212 * 2: C'''' := C''' + 1 2:Unlock()
217 * Just prior to unlock, global state is identical:
218 * ------------------------------------------------------
220 * C'''' == (C_0 + N + 1) + M + 1 C'''' == (C_0 + N + 1) + M + 1
221 * K'' == keystream generated from K'' == keystream generated from
222 * C_0 + N + 1 + M, K'. C_0 + N + 1 + M, K'.
223 * K' has been erased. K' has been erased.
225 * Finally, in the new design, the two consumer threads can finish the
226 * remainder of the generation at any time (including simultaneously):
229 * 1: Keystream(stack_C, stack_K, N)
230 * 1: <N blocks generated>**
233 * 1:ExplicitBzero(stack_C, stack_K)
236 * 2: Keystream(stack_C', stack_K', M)
237 * 2: <M blocks generated>**
240 * 2:ExplicitBzero(stack_C', stack_K')
242 * The generated user keystream for both threads is identical between the two
245 * 1: Keystream(C_0, K_0, N) 1: Keystream(stack_C, stack_K, N)
246 * 2: Keystream(C'', K', M) 2: Keystream(stack_C', stack_K', M)
248 * (stack_C == C_0; stack_K == K_0; stack_C' == C''; stack_K' == K'.)
250 static bool fortuna_concurrent_read __read_frequently = true;
253 static struct sysctl_ctx_list random_clist;
254 RANDOM_CHECK_UINT(fs_minpoolsize, RANDOM_FORTUNA_MINPOOLSIZE, RANDOM_FORTUNA_MAXPOOLSIZE);
256 static uint8_t zero_region[RANDOM_ZERO_BLOCKSIZE];
259 static void random_fortuna_pre_read(void);
260 static void random_fortuna_read(uint8_t *, size_t);
261 static bool random_fortuna_seeded(void);
262 static bool random_fortuna_seeded_internal(void);
263 static void random_fortuna_process_event(struct harvest_event *);
265 static void random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount);
267 #ifdef RANDOM_LOADABLE
270 const struct random_algorithm random_alg_context = {
271 .ra_ident = "Fortuna",
272 .ra_pre_read = random_fortuna_pre_read,
273 .ra_read = random_fortuna_read,
274 .ra_seeded = random_fortuna_seeded,
275 .ra_event_processor = random_fortuna_process_event,
276 .ra_poolcount = RANDOM_FORTUNA_NPOOLS,
281 random_fortuna_init_alg(void *unused __unused)
285 struct sysctl_oid *random_fortuna_o;
288 #ifdef RANDOM_LOADABLE
289 p_random_alg_context = &random_alg_context;
292 RANDOM_RESEED_INIT_LOCK();
294 * Fortuna parameters. Do not adjust these unless you have
295 * have a very good clue about what they do!
297 fortuna_state.fs_minpoolsize = RANDOM_FORTUNA_DEFPOOLSIZE;
299 fortuna_state.fs_lasttime = 0;
300 random_fortuna_o = SYSCTL_ADD_NODE(&random_clist,
301 SYSCTL_STATIC_CHILDREN(_kern_random),
302 OID_AUTO, "fortuna", CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
303 "Fortuna Parameters");
304 SYSCTL_ADD_PROC(&random_clist,
305 SYSCTL_CHILDREN(random_fortuna_o), OID_AUTO, "minpoolsize",
306 CTLTYPE_UINT | CTLFLAG_RWTUN | CTLFLAG_MPSAFE,
307 &fortuna_state.fs_minpoolsize, RANDOM_FORTUNA_DEFPOOLSIZE,
308 random_check_uint_fs_minpoolsize, "IU",
309 "Minimum pool size necessary to cause a reseed");
310 KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0 at startup"));
312 SYSCTL_ADD_BOOL(&random_clist, SYSCTL_CHILDREN(random_fortuna_o),
313 OID_AUTO, "concurrent_read", CTLFLAG_RDTUN,
314 &fortuna_concurrent_read, 0, "If non-zero, enable "
315 "feature to improve concurrent Fortuna performance.");
319 * FS&K - InitializePRNG()
323 for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
324 randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
325 fortuna_state.fs_pool[i].fsp_length = 0;
327 fortuna_state.fs_reseedcount = 0;
329 * FS&K - InitializeGenerator()
333 fortuna_state.fs_counter = UINT128_ZERO;
334 explicit_bzero(&fortuna_state.fs_key, sizeof(fortuna_state.fs_key));
336 SYSINIT(random_alg, SI_SUB_RANDOM, SI_ORDER_SECOND, random_fortuna_init_alg,
340 * FS&K - AddRandomEvent()
341 * Process a single stochastic event off the harvest queue
344 random_fortuna_process_event(struct harvest_event *event)
348 RANDOM_RESEED_LOCK();
350 * FS&K - P_i = P_i|<harvested stuff>
351 * Accumulate the event into the appropriate pool
352 * where each event carries the destination information.
354 * The hash_init() and hash_finish() calls are done in
355 * random_fortuna_pre_read().
357 * We must be locked against pool state modification which can happen
358 * during accumulation/reseeding and reading/regating.
360 pl = event->he_destination % RANDOM_FORTUNA_NPOOLS;
362 * If a VM generation ID changes (clone and play or VM rewind), we want
363 * to incorporate that as soon as possible. Override destingation pool
364 * for immediate next use.
366 if (event->he_source == RANDOM_PURE_VMGENID)
369 * We ignore low entropy static/counter fields towards the end of the
370 * he_event structure in order to increase measurable entropy when
371 * conducting SP800-90B entropy analysis measurements of seed material
375 KASSERT(event->he_size <= sizeof(event->he_entropy),
376 ("%s: event->he_size: %hhu > sizeof(event->he_entropy): %zu\n",
377 __func__, event->he_size, sizeof(event->he_entropy)));
378 randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
379 &event->he_somecounter, sizeof(event->he_somecounter));
380 randomdev_hash_iterate(&fortuna_state.fs_pool[pl].fsp_hash,
381 event->he_entropy, event->he_size);
384 * Don't wrap the length. This is a "saturating" add.
385 * XXX: FIX!!: We don't actually need lengths for anything but fs_pool[0],
386 * but it's been useful debugging to see them all.
388 fortuna_state.fs_pool[pl].fsp_length = MIN(RANDOM_FORTUNA_MAXPOOLSIZE,
389 fortuna_state.fs_pool[pl].fsp_length +
390 sizeof(event->he_somecounter) + event->he_size);
391 RANDOM_RESEED_UNLOCK();
396 * This introduces new key material into the output generator.
397 * Additionally it increments the output generator's counter
398 * variable C. When C > 0, the output generator is seeded and
399 * will deliver output.
400 * The entropy_data buffer passed is a very specific size; the
401 * product of RANDOM_FORTUNA_NPOOLS and RANDOM_KEYSIZE.
404 random_fortuna_reseed_internal(uint32_t *entropy_data, u_int blockcount)
406 struct randomdev_hash context;
407 uint8_t hash[RANDOM_KEYSIZE];
408 const void *keymaterial;
412 RANDOM_RESEED_ASSERT_LOCK_OWNED();
414 seeded = random_fortuna_seeded_internal();
416 randomdev_getkey(&fortuna_state.fs_key, &keymaterial, &keysz);
417 KASSERT(keysz == RANDOM_KEYSIZE, ("%s: key size %zu not %u",
418 __func__, keysz, (unsigned)RANDOM_KEYSIZE));
422 * FS&K - K = Hd(K|s) where Hd(m) is H(H(0^512|m))
425 randomdev_hash_init(&context);
426 randomdev_hash_iterate(&context, zero_region, RANDOM_ZERO_BLOCKSIZE);
428 randomdev_hash_iterate(&context, keymaterial, keysz);
429 randomdev_hash_iterate(&context, entropy_data, RANDOM_KEYSIZE*blockcount);
430 randomdev_hash_finish(&context, hash);
431 randomdev_hash_init(&context);
432 randomdev_hash_iterate(&context, hash, RANDOM_KEYSIZE);
433 randomdev_hash_finish(&context, hash);
434 randomdev_encrypt_init(&fortuna_state.fs_key, hash);
435 explicit_bzero(hash, sizeof(hash));
436 /* Unblock the device if this is the first time we are reseeding. */
437 if (uint128_is_zero(fortuna_state.fs_counter))
439 uint128_increment(&fortuna_state.fs_counter);
443 * FS&K - RandomData() (Part 1)
444 * Used to return processed entropy from the PRNG. There is a pre_read
445 * required to be present (but it can be a stub) in order to allow
446 * specific actions at the begin of the read.
449 random_fortuna_pre_read(void)
454 struct randomdev_hash context;
455 uint32_t s[RANDOM_FORTUNA_NPOOLS*RANDOM_KEYSIZE_WORDS];
456 uint8_t temp[RANDOM_KEYSIZE];
459 KASSERT(fortuna_state.fs_minpoolsize > 0, ("random: Fortuna threshold must be > 0"));
460 RANDOM_RESEED_LOCK();
462 /* FS&K - Use 'getsbinuptime()' to prevent reseed-spamming. */
463 now = getsbinuptime();
466 if (fortuna_state.fs_pool[0].fsp_length < fortuna_state.fs_minpoolsize
469 * FS&K - Use 'getsbinuptime()' to prevent reseed-spamming, but do
470 * not block initial seeding (fs_lasttime == 0).
472 || (__predict_true(fortuna_state.fs_lasttime != 0) &&
473 now - fortuna_state.fs_lasttime <= SBT_1S/10)
476 RANDOM_RESEED_UNLOCK();
482 * When set, pretend we do not have enough entropy to reseed yet.
484 KFAIL_POINT_CODE(DEBUG_FP, random_fortuna_pre_read, {
485 if (RETURN_VALUE != 0) {
486 RANDOM_RESEED_UNLOCK();
493 fortuna_state.fs_lasttime = now;
496 /* FS&K - ReseedCNT = ReseedCNT + 1 */
497 fortuna_state.fs_reseedcount++;
498 /* s = \epsilon at start */
499 for (i = 0; i < RANDOM_FORTUNA_NPOOLS; i++) {
500 /* FS&K - if Divides(ReseedCnt, 2^i) ... */
501 if ((fortuna_state.fs_reseedcount % (1 << i)) == 0) {
503 * FS&K - temp = (P_i)
507 randomdev_hash_finish(&fortuna_state.fs_pool[i].fsp_hash, temp);
508 randomdev_hash_init(&fortuna_state.fs_pool[i].fsp_hash);
509 fortuna_state.fs_pool[i].fsp_length = 0;
510 randomdev_hash_init(&context);
511 randomdev_hash_iterate(&context, temp, RANDOM_KEYSIZE);
512 randomdev_hash_finish(&context, s + i*RANDOM_KEYSIZE_WORDS);
517 SDT_PROBE2(random, fortuna, event_processor, debug, fortuna_state.fs_reseedcount, fortuna_state.fs_pool);
520 random_fortuna_reseed_internal(s, i);
521 RANDOM_RESEED_UNLOCK();
523 /* Clean up and secure */
524 explicit_bzero(s, sizeof(s));
525 explicit_bzero(temp, sizeof(temp));
529 * This is basically GenerateBlocks() from FS&K.
531 * It differs in two ways:
533 * 1. Chacha20 is tolerant of non-block-multiple request sizes, so we do not
534 * need to handle any remainder bytes specially and can just pass the length
535 * directly to the PRF construction; and
537 * 2. Chacha20 is a 512-bit block size cipher (whereas AES has 128-bit block
538 * size, regardless of key size). This means Chacha does not require re-keying
539 * every 1MiB. This is implied by the math in FS&K 9.4 and mentioned
540 * explicitly in the conclusion, "If we had a block cipher with a 256-bit [or
541 * greater] block size, then the collisions would not have been an issue at
544 * 3. In conventional ("locked") mode, we produce a maximum of PAGE_SIZE output
545 * at a time before dropping the lock, to not bully the lock especially. This
546 * has been the status quo since 2015 (r284959).
548 * The upstream caller random_fortuna_read is responsible for zeroing out
549 * sensitive buffers provided as parameters to this routine.
552 FORTUNA_UNLOCKED = false,
553 FORTUNA_LOCKED = true
556 random_fortuna_genbytes(uint8_t *buf, size_t bytecount,
557 uint8_t newkey[static RANDOM_KEYSIZE], uint128_t *p_counter,
558 union randomdev_key *p_key, bool locked)
560 uint8_t remainder_buf[RANDOM_BLOCKSIZE];
564 RANDOM_RESEED_ASSERT_LOCK_OWNED();
566 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
569 * Easy case: don't have to worry about bullying the global mutex,
570 * don't have to worry about rekeying Chacha; API is byte-oriented.
572 if (!locked && random_chachamode) {
573 randomdev_keystream(p_key, p_counter, buf, bytecount);
579 * While holding the global lock, limit PRF generation to
580 * mitigate, but not eliminate, bullying symptoms.
582 chunk_size = PAGE_SIZE;
585 * 128-bit block ciphers like AES must be re-keyed at 1MB
586 * intervals to avoid unacceptable statistical differentiation
587 * from true random data (FS&K 9.4, p. 143-144).
589 MPASS(!random_chachamode);
590 chunk_size = RANDOM_FORTUNA_MAX_READ;
593 chunk_size = MIN(bytecount, chunk_size);
594 if (!random_chachamode)
595 chunk_size = rounddown(chunk_size, RANDOM_BLOCKSIZE);
597 while (bytecount >= chunk_size && chunk_size > 0) {
598 randomdev_keystream(p_key, p_counter, buf, chunk_size);
601 bytecount -= chunk_size;
603 /* We have to rekey if there is any data remaining to be
604 * generated, in two scenarios:
606 * locked: we need to rekey before we unlock and release the
607 * global state to another consumer; or
609 * unlocked: we need to rekey because we're in AES mode and are
610 * required to rekey at chunk_size==1MB. But we do not need to
611 * rekey during the last trailing <1MB chunk.
614 if (locked || chunk_size == RANDOM_FORTUNA_MAX_READ) {
615 randomdev_keystream(p_key, p_counter, newkey,
617 randomdev_encrypt_init(p_key, newkey);
621 * If we're holding the global lock, yield it briefly
625 RANDOM_RESEED_UNLOCK();
626 RANDOM_RESEED_LOCK();
630 * At the trailing end, scale down chunk_size from 1MB or
631 * PAGE_SIZE to all remaining full blocks (AES) or all
632 * remaining bytes (Chacha).
634 if (bytecount < chunk_size) {
635 if (random_chachamode)
636 chunk_size = bytecount;
637 else if (bytecount >= RANDOM_BLOCKSIZE)
638 chunk_size = rounddown(bytecount,
647 * Generate any partial AES block remaining into a temporary buffer and
648 * copy the desired substring out.
651 MPASS(!random_chachamode);
653 randomdev_keystream(p_key, p_counter, remainder_buf,
654 sizeof(remainder_buf));
658 * In locked mode, re-key global K before dropping the lock, which we
659 * don't need for memcpy/bzero below.
662 randomdev_keystream(p_key, p_counter, newkey, RANDOM_KEYSIZE);
663 randomdev_encrypt_init(p_key, newkey);
664 RANDOM_RESEED_UNLOCK();
668 memcpy(buf, remainder_buf, bytecount);
669 explicit_bzero(remainder_buf, sizeof(remainder_buf));
675 * Handle only "concurrency-enabled" Fortuna reads to simplify logic.
677 * Caller (random_fortuna_read) is responsible for zeroing out sensitive
678 * buffers provided as parameters to this routine.
681 random_fortuna_read_concurrent(uint8_t *buf, size_t bytecount,
682 uint8_t newkey[static RANDOM_KEYSIZE])
684 union randomdev_key key_copy;
685 uint128_t counter_copy;
688 MPASS(fortuna_concurrent_read);
691 * Compute number of blocks required for the PRF request ('delta C').
692 * We will step the global counter 'C' by this number under lock, and
693 * then actually consume the counter values outside the lock.
695 * This ensures that contemporaneous but independent requests for
696 * randomness receive distinct 'C' values and thus independent PRF
699 if (random_chachamode) {
700 blockcount = howmany(bytecount, CHACHA_BLOCKLEN);
702 blockcount = howmany(bytecount, RANDOM_BLOCKSIZE);
705 * Need to account for the additional blocks generated by
706 * rekeying when updating the global fs_counter.
708 blockcount += RANDOM_KEYS_PER_BLOCK *
709 (blockcount / RANDOM_FORTUNA_BLOCKS_PER_KEY);
712 RANDOM_RESEED_LOCK();
713 KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
716 * Save the original counter and key values that will be used as the
717 * PRF for this particular consumer.
719 memcpy(&counter_copy, &fortuna_state.fs_counter, sizeof(counter_copy));
720 memcpy(&key_copy, &fortuna_state.fs_key, sizeof(key_copy));
723 * Step the counter as if we had generated 'bytecount' blocks for this
724 * consumer. I.e., ensure that the next consumer gets an independent
725 * range of counter values once we drop the global lock.
727 uint128_add64(&fortuna_state.fs_counter, blockcount);
730 * We still need to Rekey the global 'K' between independent calls;
731 * this is no different from conventional Fortuna. Note that
732 * 'randomdev_keystream()' will step the fs_counter 'C' appropriately
733 * for the blocks needed for the 'newkey'.
735 * (This is part of PseudoRandomData() in FS&K, 9.4.4.)
737 randomdev_keystream(&fortuna_state.fs_key, &fortuna_state.fs_counter,
738 newkey, RANDOM_KEYSIZE);
739 randomdev_encrypt_init(&fortuna_state.fs_key, newkey);
742 * We have everything we need to generate a unique PRF for this
743 * consumer without touching global state.
745 RANDOM_RESEED_UNLOCK();
747 random_fortuna_genbytes(buf, bytecount, newkey, &counter_copy,
748 &key_copy, FORTUNA_UNLOCKED);
749 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
751 explicit_bzero(&counter_copy, sizeof(counter_copy));
752 explicit_bzero(&key_copy, sizeof(key_copy));
756 * FS&K - RandomData() (Part 2)
757 * Main read from Fortuna, continued. May be called multiple times after
758 * the random_fortuna_pre_read() above.
760 * The supplied buf MAY not be a multiple of RANDOM_BLOCKSIZE in size; it is
761 * the responsibility of the algorithm to accommodate partial block reads, if a
762 * block output mode is used.
765 random_fortuna_read(uint8_t *buf, size_t bytecount)
767 uint8_t newkey[RANDOM_KEYSIZE];
769 if (fortuna_concurrent_read) {
770 random_fortuna_read_concurrent(buf, bytecount, newkey);
774 RANDOM_RESEED_LOCK();
775 KASSERT(!uint128_is_zero(fortuna_state.fs_counter), ("FS&K: C != 0"));
777 random_fortuna_genbytes(buf, bytecount, newkey,
778 &fortuna_state.fs_counter, &fortuna_state.fs_key, FORTUNA_LOCKED);
779 /* Returns unlocked */
780 RANDOM_RESEED_ASSERT_LOCK_NOT_OWNED();
783 explicit_bzero(newkey, sizeof(newkey));
787 static bool block_seeded_status = false;
788 SYSCTL_BOOL(_kern_random, OID_AUTO, block_seeded_status, CTLFLAG_RWTUN,
789 &block_seeded_status, 0,
790 "If non-zero, pretend Fortuna is in an unseeded state. By setting "
791 "this as a tunable, boot can be tested as if the random device is "
796 random_fortuna_seeded_internal(void)
798 return (!uint128_is_zero(fortuna_state.fs_counter));
802 random_fortuna_seeded(void)
806 if (block_seeded_status)
810 if (__predict_true(random_fortuna_seeded_internal()))
814 * Maybe we have enough entropy in the zeroth pool but just haven't
815 * kicked the initial seed step. Do so now.
817 random_fortuna_pre_read();
819 return (random_fortuna_seeded_internal());