1 /* $OpenBSD: rnd.c,v 1.225 2022/11/03 04:56:47 guenther Exp $ */ 2 3 /* 4 * Copyright (c) 2011,2020 Theo de Raadt. 5 * Copyright (c) 2008 Damien Miller. 6 * Copyright (c) 1996, 1997, 2000-2002 Michael Shalayeff. 7 * Copyright (c) 2013 Markus Friedl. 8 * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. 9 * All rights reserved. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, and the entire permission notice in its entirety, 16 * including the disclaimer of warranties. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. The name of the author may not be used to endorse or promote 21 * products derived from this software without specific prior 22 * written permission. 23 * 24 * ALTERNATIVELY, this product may be distributed under the terms of 25 * the GNU Public License, in which case the provisions of the GPL are 26 * required INSTEAD OF the above restrictions. (This clause is 27 * necessary due to a potential bad interaction between the GPL and 28 * the restrictions contained in a BSD-style copyright.) 29 * 30 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED 31 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 33 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 34 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 35 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 36 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 38 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 39 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 40 * OF THE POSSIBILITY OF SUCH DAMAGE. 41 */ 42 43 /* 44 * The bootblocks pre-fill the kernel .openbsd.randomdata section with seed 45 * material (on-disk from previous boot, hopefully mixed with a hardware rng). 46 * The first arc4random(9) call initializes this seed material as a chacha 47 * state. Calls can be done early in kernel bootstrap code -- early use is 48 * encouraged. 49 * 50 * After the kernel timeout subsystem is initialized, random_start() prepares 51 * the entropy collection mechanism enqueue_randomness() and timeout-driven 52 * mixing into the chacha state. The first submissions come from device 53 * probes, later on interrupt-time submissions are more common. Entropy 54 * data (and timing information) get mixed over the entropy input ring 55 * rnd_event_space[] -- the goal is to collect damage. 56 * 57 * Based upon timeouts, a selection of the entropy ring rnd_event_space[] 58 * CRC bit-distributed and XOR mixed into entropy_pool[]. 59 * 60 * From time to time, entropy_pool[] is SHA512-whitened, mixed with time 61 * information again, XOR'd with the inner and outer states of the existing 62 * chacha state, to create a new chacha state. 63 * 64 * During early boot (until cold=0), enqueue operations are immediately 65 * dequeued, and mixed into the chacha. 66 */ 67 68 #include <sys/param.h> 69 #include <sys/event.h> 70 #include <sys/ioctl.h> 71 #include <sys/malloc.h> 72 #include <sys/timeout.h> 73 #include <sys/atomic.h> 74 #include <sys/task.h> 75 #include <sys/msgbuf.h> 76 #include <sys/mount.h> 77 #include <sys/syscallargs.h> 78 79 #include <crypto/sha2.h> 80 81 #define KEYSTREAM_ONLY 82 #include <crypto/chacha_private.h> 83 84 #include <uvm/uvm_extern.h> 85 86 /* 87 * For the purposes of better mixing, we use the CRC-32 polynomial as 88 * well to make a twisted Generalized Feedback Shift Register 89 * 90 * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM 91 * Transactions on Modeling and Computer Simulation 2(3):179-194. 92 * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators 93 * II. ACM Transactions on Modeling and Computer Simulation 4:254-266) 94 */ 95 96 /* 97 * Stirring polynomial over GF(2). Used in add_entropy_words() below. 98 * 99 * The polynomial terms are chosen to be evenly spaced (minimum RMS 100 * distance from evenly spaced; except for the last tap, which is 1 to 101 * get the twisting happening as fast as possible. 102 * 103 * The resultant polynomial is: 104 * 2^POOLWORDS + 2^POOL_TAP1 + 2^POOL_TAP2 + 2^POOL_TAP3 + 2^POOL_TAP4 + 1 105 */ 106 #define POOLWORDS 2048 107 #define POOLBYTES (POOLWORDS*4) 108 #define POOLMASK (POOLWORDS - 1) 109 #define POOL_TAP1 1638 110 #define POOL_TAP2 1231 111 #define POOL_TAP3 819 112 #define POOL_TAP4 411 113 114 /* 115 * Raw entropy collection from device drivers; at interrupt context or not. 116 * enqueue_randomness() is used to submit data into the entropy input ring. 117 */ 118 119 #define QEVLEN 128 /* must be a power of 2 */ 120 #define QEVCONSUME 8 /* how many events to consume a time */ 121 122 #define KEYSZ 32 123 #define IVSZ 8 124 #define BLOCKSZ 64 125 #define RSBUFSZ (16*BLOCKSZ) 126 #define EBUFSIZE KEYSZ + IVSZ 127 128 struct rand_event { 129 u_int re_time; 130 u_int re_val; 131 } rnd_event_space[QEVLEN]; 132 133 u_int rnd_event_cons; 134 u_int rnd_event_prod; 135 int rnd_cold = 1; 136 int rnd_slowextract = 1; 137 138 void rnd_reinit(void *v); /* timeout to start reinit */ 139 void rnd_init(void *); /* actually do the reinit */ 140 141 static u_int32_t entropy_pool[POOLWORDS]; 142 u_int32_t entropy_pool0[POOLWORDS] __attribute__((section(".openbsd.randomdata"))); 143 144 void dequeue_randomness(void *); 145 void add_entropy_words(const u_int32_t *, u_int); 146 void extract_entropy(u_int8_t *) 147 __attribute__((__bounded__(__minbytes__,1,EBUFSIZE))); 148 149 struct timeout rnd_timeout = TIMEOUT_INITIALIZER(dequeue_randomness, NULL); 150 151 int filt_randomread(struct knote *, long); 152 void filt_randomdetach(struct knote *); 153 int filt_randomwrite(struct knote *, long); 154 155 static void _rs_seed(u_char *, size_t); 156 static void _rs_clearseed(const void *p, size_t s); 157 158 const struct filterops randomread_filtops = { 159 .f_flags = FILTEROP_ISFD, 160 .f_attach = NULL, 161 .f_detach = filt_randomdetach, 162 .f_event = filt_randomread, 163 }; 164 165 const struct filterops randomwrite_filtops = { 166 .f_flags = FILTEROP_ISFD, 167 .f_attach = NULL, 168 .f_detach = filt_randomdetach, 169 .f_event = filt_randomwrite, 170 }; 171 172 /* 173 * This function mixes entropy and timing into the entropy input ring. 174 */ 175 void 176 enqueue_randomness(u_int val) 177 { 178 struct rand_event *rep; 179 int e; 180 181 e = (atomic_inc_int_nv(&rnd_event_prod) - 1) & (QEVLEN-1); 182 rep = &rnd_event_space[e]; 183 rep->re_time += cpu_rnd_messybits(); 184 rep->re_val += val; 185 186 if (rnd_cold) { 187 dequeue_randomness(NULL); 188 rnd_init(NULL); 189 if (!cold) 190 rnd_cold = 0; 191 } else if (!timeout_pending(&rnd_timeout) && 192 (rnd_event_prod - rnd_event_cons) > QEVCONSUME) { 193 rnd_slowextract = min(rnd_slowextract * 2, 5000); 194 timeout_add_msec(&rnd_timeout, rnd_slowextract * 10); 195 } 196 } 197 198 /* 199 * This function merges entropy ring information into the buffer using 200 * a polynomial to spread the bits. 201 */ 202 void 203 add_entropy_words(const u_int32_t *buf, u_int n) 204 { 205 /* derived from IEEE 802.3 CRC-32 */ 206 static const u_int32_t twist_table[8] = { 207 0x00000000, 0x3b6e20c8, 0x76dc4190, 0x4db26158, 208 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 209 }; 210 static u_int entropy_add_ptr; 211 static u_char entropy_input_rotate; 212 213 for (; n--; buf++) { 214 u_int32_t w = (*buf << entropy_input_rotate) | 215 (*buf >> ((32 - entropy_input_rotate) & 31)); 216 u_int i = entropy_add_ptr = 217 (entropy_add_ptr - 1) & POOLMASK; 218 /* 219 * Normally, we add 7 bits of rotation to the pool. 220 * At the beginning of the pool, add an extra 7 bits 221 * rotation, so that successive passes spread the 222 * input bits across the pool evenly. 223 */ 224 entropy_input_rotate = 225 (entropy_input_rotate + (i ? 7 : 14)) & 31; 226 227 /* XOR pool contents corresponding to polynomial terms */ 228 w ^= entropy_pool[(i + POOL_TAP1) & POOLMASK] ^ 229 entropy_pool[(i + POOL_TAP2) & POOLMASK] ^ 230 entropy_pool[(i + POOL_TAP3) & POOLMASK] ^ 231 entropy_pool[(i + POOL_TAP4) & POOLMASK] ^ 232 entropy_pool[(i + 1) & POOLMASK] ^ 233 entropy_pool[i]; /* + 2^POOLWORDS */ 234 235 entropy_pool[i] = (w >> 3) ^ twist_table[w & 7]; 236 } 237 } 238 239 /* 240 * Pulls entropy out of the queue and merges it into the pool with the 241 * CRC. This takes a mix of fresh entries from the producer end of the 242 * queue and entries from the consumer end of the queue which are 243 * likely to have collected more damage. 244 */ 245 /* ARGSUSED */ 246 void 247 dequeue_randomness(void *v) 248 { 249 u_int32_t buf[2]; 250 u_int startp, startc, i; 251 252 if (!rnd_cold) 253 timeout_del(&rnd_timeout); 254 255 /* Some very new damage */ 256 startp = rnd_event_prod - QEVCONSUME; 257 for (i = 0; i < QEVCONSUME; i++) { 258 u_int e = (startp + i) & (QEVLEN-1); 259 260 buf[0] = rnd_event_space[e].re_time; 261 buf[1] = rnd_event_space[e].re_val; 262 add_entropy_words(buf, 2); 263 } 264 /* and some probably more damaged */ 265 startc = rnd_event_cons; 266 for (i = 0; i < QEVCONSUME; i++) { 267 u_int e = (startc + i) & (QEVLEN-1); 268 269 buf[0] = rnd_event_space[e].re_time; 270 buf[1] = rnd_event_space[e].re_val; 271 add_entropy_words(buf, 2); 272 } 273 rnd_event_cons = startp + QEVCONSUME; 274 } 275 276 /* 277 * Grabs a chunk from the entropy_pool[] and slams it through SHA512 when 278 * requested. 279 */ 280 void 281 extract_entropy(u_int8_t *buf) 282 { 283 static u_int32_t extract_pool[POOLWORDS]; 284 u_char digest[SHA512_DIGEST_LENGTH]; 285 SHA2_CTX shactx; 286 287 #if SHA512_DIGEST_LENGTH < EBUFSIZE 288 #error "need more bigger hash output" 289 #endif 290 291 /* 292 * INTENTIONALLY not protected by any lock. Races during 293 * memcpy() result in acceptable input data; races during 294 * SHA512Update() would create nasty data dependencies. We 295 * do not rely on this as a benefit, but if it happens, cool. 296 */ 297 memcpy(extract_pool, entropy_pool, sizeof(extract_pool)); 298 299 /* Hash the pool to get the output */ 300 SHA512Init(&shactx); 301 SHA512Update(&shactx, (u_int8_t *)extract_pool, sizeof(extract_pool)); 302 SHA512Final(digest, &shactx); 303 304 /* Copy data to destination buffer */ 305 memcpy(buf, digest, EBUFSIZE); 306 307 /* 308 * Modify pool so next hash will produce different results. 309 * During boot-time enqueue/dequeue stage, avoid recursion. 310 */ 311 if (!rnd_cold) 312 enqueue_randomness(extract_pool[0]); 313 dequeue_randomness(NULL); 314 315 /* Wipe data from memory */ 316 explicit_bzero(extract_pool, sizeof(extract_pool)); 317 explicit_bzero(digest, sizeof(digest)); 318 } 319 320 /* random keystream by ChaCha */ 321 322 struct mutex rndlock = MUTEX_INITIALIZER(IPL_HIGH); 323 struct timeout rndreinit_timeout = TIMEOUT_INITIALIZER(rnd_reinit, NULL); 324 struct task rnd_task = TASK_INITIALIZER(rnd_init, NULL); 325 326 static chacha_ctx rs; /* chacha context for random keystream */ 327 /* keystream blocks (also chacha seed from boot) */ 328 static u_char rs_buf[RSBUFSZ]; 329 u_char rs_buf0[RSBUFSZ] __attribute__((section(".openbsd.randomdata"))); 330 static size_t rs_have; /* valid bytes at end of rs_buf */ 331 static size_t rs_count; /* bytes till reseed */ 332 333 void 334 suspend_randomness(void) 335 { 336 struct timespec ts; 337 338 getnanotime(&ts); 339 enqueue_randomness(ts.tv_sec); 340 enqueue_randomness(ts.tv_nsec); 341 342 dequeue_randomness(NULL); 343 rs_count = 0; 344 arc4random_buf(entropy_pool, sizeof(entropy_pool)); 345 } 346 347 void 348 resume_randomness(char *buf, size_t buflen) 349 { 350 struct timespec ts; 351 352 if (buf && buflen) 353 _rs_seed(buf, buflen); 354 getnanotime(&ts); 355 enqueue_randomness(ts.tv_sec); 356 enqueue_randomness(ts.tv_nsec); 357 358 dequeue_randomness(NULL); 359 rs_count = 0; 360 } 361 362 static inline void _rs_rekey(u_char *dat, size_t datlen); 363 364 static inline void 365 _rs_init(u_char *buf, size_t n) 366 { 367 KASSERT(n >= KEYSZ + IVSZ); 368 chacha_keysetup(&rs, buf, KEYSZ * 8); 369 chacha_ivsetup(&rs, buf + KEYSZ, NULL); 370 } 371 372 static void 373 _rs_seed(u_char *buf, size_t n) 374 { 375 _rs_rekey(buf, n); 376 377 /* invalidate rs_buf */ 378 rs_have = 0; 379 memset(rs_buf, 0, sizeof(rs_buf)); 380 381 rs_count = 1600000; 382 } 383 384 static void 385 _rs_stir(int do_lock) 386 { 387 struct timespec ts; 388 u_int8_t buf[EBUFSIZE], *p; 389 int i; 390 391 /* 392 * Use SHA512 PRNG data and a system timespec; early in the boot 393 * process this is the best we can do -- some architectures do 394 * not collect entropy very well during this time, but may have 395 * clock information which is better than nothing. 396 */ 397 extract_entropy(buf); 398 399 nanotime(&ts); 400 for (p = (u_int8_t *)&ts, i = 0; i < sizeof(ts); i++) 401 buf[i] ^= p[i]; 402 403 if (do_lock) 404 mtx_enter(&rndlock); 405 _rs_seed(buf, sizeof(buf)); 406 if (do_lock) 407 mtx_leave(&rndlock); 408 explicit_bzero(buf, sizeof(buf)); 409 410 /* encourage fast-dequeue again */ 411 rnd_slowextract = 1; 412 } 413 414 static inline void 415 _rs_stir_if_needed(size_t len) 416 { 417 static int rs_initialized; 418 419 if (!rs_initialized) { 420 memcpy(entropy_pool, entropy_pool0, sizeof(entropy_pool)); 421 memcpy(rs_buf, rs_buf0, sizeof(rs_buf)); 422 /* seeds cannot be cleaned yet, random_start() will do so */ 423 _rs_init(rs_buf, KEYSZ + IVSZ); 424 rs_count = 1024 * 1024 * 1024; /* until main() runs */ 425 rs_initialized = 1; 426 } else if (rs_count <= len) 427 _rs_stir(0); 428 else 429 rs_count -= len; 430 } 431 432 static void 433 _rs_clearseed(const void *p, size_t s) 434 { 435 struct kmem_dyn_mode kd_avoidalias; 436 vaddr_t va = trunc_page((vaddr_t)p); 437 vsize_t off = (vaddr_t)p - va; 438 vsize_t len; 439 vaddr_t rwva; 440 paddr_t pa; 441 442 while (s > 0) { 443 pmap_extract(pmap_kernel(), va, &pa); 444 445 memset(&kd_avoidalias, 0, sizeof(kd_avoidalias)); 446 kd_avoidalias.kd_prefer = pa; 447 kd_avoidalias.kd_waitok = 1; 448 rwva = (vaddr_t)km_alloc(PAGE_SIZE, &kv_any, &kp_none, 449 &kd_avoidalias); 450 if (!rwva) 451 panic("_rs_clearseed"); 452 453 pmap_kenter_pa(rwva, pa, PROT_READ | PROT_WRITE); 454 pmap_update(pmap_kernel()); 455 456 len = MIN(s, PAGE_SIZE - off); 457 explicit_bzero((void *)(rwva + off), len); 458 459 pmap_kremove(rwva, PAGE_SIZE); 460 km_free((void *)rwva, PAGE_SIZE, &kv_any, &kp_none); 461 462 va += PAGE_SIZE; 463 s -= len; 464 off = 0; 465 } 466 } 467 468 static inline void 469 _rs_rekey(u_char *dat, size_t datlen) 470 { 471 #ifndef KEYSTREAM_ONLY 472 memset(rs_buf, 0, sizeof(rs_buf)); 473 #endif 474 /* fill rs_buf with the keystream */ 475 chacha_encrypt_bytes(&rs, rs_buf, rs_buf, sizeof(rs_buf)); 476 /* mix in optional user provided data */ 477 if (dat) { 478 size_t i, m; 479 480 m = MIN(datlen, KEYSZ + IVSZ); 481 for (i = 0; i < m; i++) 482 rs_buf[i] ^= dat[i]; 483 } 484 /* immediately reinit for backtracking resistance */ 485 _rs_init(rs_buf, KEYSZ + IVSZ); 486 memset(rs_buf, 0, KEYSZ + IVSZ); 487 rs_have = sizeof(rs_buf) - KEYSZ - IVSZ; 488 } 489 490 static inline void 491 _rs_random_buf(void *_buf, size_t n) 492 { 493 u_char *buf = (u_char *)_buf; 494 size_t m; 495 496 _rs_stir_if_needed(n); 497 while (n > 0) { 498 if (rs_have > 0) { 499 m = MIN(n, rs_have); 500 memcpy(buf, rs_buf + sizeof(rs_buf) - rs_have, m); 501 memset(rs_buf + sizeof(rs_buf) - rs_have, 0, m); 502 buf += m; 503 n -= m; 504 rs_have -= m; 505 } 506 if (rs_have == 0) 507 _rs_rekey(NULL, 0); 508 } 509 } 510 511 static inline void 512 _rs_random_u32(u_int32_t *val) 513 { 514 _rs_stir_if_needed(sizeof(*val)); 515 if (rs_have < sizeof(*val)) 516 _rs_rekey(NULL, 0); 517 memcpy(val, rs_buf + sizeof(rs_buf) - rs_have, sizeof(*val)); 518 memset(rs_buf + sizeof(rs_buf) - rs_have, 0, sizeof(*val)); 519 rs_have -= sizeof(*val); 520 } 521 522 /* Return one word of randomness from a ChaCha20 generator */ 523 u_int32_t 524 arc4random(void) 525 { 526 u_int32_t ret; 527 528 mtx_enter(&rndlock); 529 _rs_random_u32(&ret); 530 mtx_leave(&rndlock); 531 return ret; 532 } 533 534 /* 535 * Fill a buffer of arbitrary length with ChaCha20-derived randomness. 536 */ 537 void 538 arc4random_buf(void *buf, size_t n) 539 { 540 mtx_enter(&rndlock); 541 _rs_random_buf(buf, n); 542 mtx_leave(&rndlock); 543 } 544 545 /* 546 * Allocate a new ChaCha20 context for the caller to use. 547 */ 548 struct arc4random_ctx * 549 arc4random_ctx_new(void) 550 { 551 char keybuf[KEYSZ + IVSZ]; 552 553 chacha_ctx *ctx = malloc(sizeof(chacha_ctx), M_TEMP, M_WAITOK); 554 arc4random_buf(keybuf, KEYSZ + IVSZ); 555 chacha_keysetup(ctx, keybuf, KEYSZ * 8); 556 chacha_ivsetup(ctx, keybuf + KEYSZ, NULL); 557 explicit_bzero(keybuf, sizeof(keybuf)); 558 return (struct arc4random_ctx *)ctx; 559 } 560 561 /* 562 * Free a ChaCha20 context created by arc4random_ctx_new() 563 */ 564 void 565 arc4random_ctx_free(struct arc4random_ctx *ctx) 566 { 567 explicit_bzero(ctx, sizeof(chacha_ctx)); 568 free(ctx, M_TEMP, sizeof(chacha_ctx)); 569 } 570 571 /* 572 * Use a given ChaCha20 context to fill a buffer 573 */ 574 void 575 arc4random_ctx_buf(struct arc4random_ctx *ctx, void *buf, size_t n) 576 { 577 #ifndef KEYSTREAM_ONLY 578 memset(buf, 0, n); 579 #endif 580 chacha_encrypt_bytes((chacha_ctx *)ctx, buf, buf, n); 581 } 582 583 /* 584 * Calculate a uniformly distributed random number less than upper_bound 585 * avoiding "modulo bias". 586 * 587 * Uniformity is achieved by generating new random numbers until the one 588 * returned is outside the range [0, 2**32 % upper_bound). This 589 * guarantees the selected random number will be inside 590 * [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound) 591 * after reduction modulo upper_bound. 592 */ 593 u_int32_t 594 arc4random_uniform(u_int32_t upper_bound) 595 { 596 u_int32_t r, min; 597 598 if (upper_bound < 2) 599 return 0; 600 601 /* 2**32 % x == (2**32 - x) % x */ 602 min = -upper_bound % upper_bound; 603 604 /* 605 * This could theoretically loop forever but each retry has 606 * p > 0.5 (worst case, usually far better) of selecting a 607 * number inside the range we need, so it should rarely need 608 * to re-roll. 609 */ 610 for (;;) { 611 r = arc4random(); 612 if (r >= min) 613 break; 614 } 615 616 return r % upper_bound; 617 } 618 619 /* ARGSUSED */ 620 void 621 rnd_init(void *null) 622 { 623 _rs_stir(1); 624 } 625 626 /* 627 * Called by timeout to mark arc4 for stirring, 628 */ 629 void 630 rnd_reinit(void *v) 631 { 632 task_add(systq, &rnd_task); 633 /* 10 minutes, per dm@'s suggestion */ 634 timeout_add_sec(&rndreinit_timeout, 10 * 60); 635 } 636 637 /* 638 * Start periodic services inside the random subsystem, which pull 639 * entropy forward, hash it, and re-seed the random stream as needed. 640 */ 641 void 642 random_start(int goodseed) 643 { 644 extern char etext[]; 645 646 #if !defined(NO_PROPOLICE) 647 extern long __guard_local; 648 649 if (__guard_local == 0) 650 printf("warning: no entropy supplied by boot loader\n"); 651 #endif 652 653 _rs_clearseed(entropy_pool0, sizeof(entropy_pool0)); 654 _rs_clearseed(rs_buf0, sizeof(rs_buf0)); 655 656 /* Message buffer may contain data from previous boot */ 657 if (msgbufp->msg_magic == MSG_MAGIC) 658 add_entropy_words((u_int32_t *)msgbufp->msg_bufc, 659 msgbufp->msg_bufs / sizeof(u_int32_t)); 660 add_entropy_words((u_int32_t *)etext - 32*1024, 661 8192/sizeof(u_int32_t)); 662 663 dequeue_randomness(NULL); 664 rnd_init(NULL); 665 rnd_reinit(NULL); 666 667 if (goodseed) 668 printf("random: good seed from bootblocks\n"); 669 else { 670 /* XXX kernel should work harder here */ 671 printf("random: boothowto does not indicate good seed\n"); 672 } 673 } 674 675 int 676 randomopen(dev_t dev, int flag, int mode, struct proc *p) 677 { 678 return 0; 679 } 680 681 int 682 randomclose(dev_t dev, int flag, int mode, struct proc *p) 683 { 684 return 0; 685 } 686 687 /* 688 * Maximum number of bytes to serve directly from the main ChaCha 689 * pool. Larger requests are served from a discrete ChaCha instance keyed 690 * from the main pool. 691 */ 692 #define RND_MAIN_MAX_BYTES 2048 693 694 int 695 randomread(dev_t dev, struct uio *uio, int ioflag) 696 { 697 struct arc4random_ctx *lctx = NULL; 698 size_t total = uio->uio_resid; 699 u_char *buf; 700 int ret = 0; 701 702 if (uio->uio_resid == 0) 703 return 0; 704 705 buf = malloc(POOLBYTES, M_TEMP, M_WAITOK); 706 if (total > RND_MAIN_MAX_BYTES) 707 lctx = arc4random_ctx_new(); 708 709 while (ret == 0 && uio->uio_resid > 0) { 710 size_t n = ulmin(POOLBYTES, uio->uio_resid); 711 712 if (lctx != NULL) 713 arc4random_ctx_buf(lctx, buf, n); 714 else 715 arc4random_buf(buf, n); 716 ret = uiomove(buf, n, uio); 717 if (ret == 0 && uio->uio_resid > 0) 718 yield(); 719 } 720 if (lctx != NULL) 721 arc4random_ctx_free(lctx); 722 explicit_bzero(buf, POOLBYTES); 723 free(buf, M_TEMP, POOLBYTES); 724 return ret; 725 } 726 727 int 728 randomwrite(dev_t dev, struct uio *uio, int flags) 729 { 730 int ret = 0, newdata = 0; 731 u_int32_t *buf; 732 733 if (uio->uio_resid == 0) 734 return 0; 735 736 buf = malloc(POOLBYTES, M_TEMP, M_WAITOK); 737 738 while (ret == 0 && uio->uio_resid > 0) { 739 size_t n = ulmin(POOLBYTES, uio->uio_resid); 740 741 ret = uiomove(buf, n, uio); 742 if (ret != 0) 743 break; 744 while (n % sizeof(u_int32_t)) 745 ((u_int8_t *)buf)[n++] = 0; 746 add_entropy_words(buf, n / 4); 747 if (uio->uio_resid > 0) 748 yield(); 749 newdata = 1; 750 } 751 752 if (newdata) 753 rnd_init(NULL); 754 755 explicit_bzero(buf, POOLBYTES); 756 free(buf, M_TEMP, POOLBYTES); 757 return ret; 758 } 759 760 int 761 randomkqfilter(dev_t dev, struct knote *kn) 762 { 763 switch (kn->kn_filter) { 764 case EVFILT_READ: 765 kn->kn_fop = &randomread_filtops; 766 break; 767 case EVFILT_WRITE: 768 kn->kn_fop = &randomwrite_filtops; 769 break; 770 default: 771 return (EINVAL); 772 } 773 774 return (0); 775 } 776 777 void 778 filt_randomdetach(struct knote *kn) 779 { 780 } 781 782 int 783 filt_randomread(struct knote *kn, long hint) 784 { 785 kn->kn_data = RND_MAIN_MAX_BYTES; 786 return (1); 787 } 788 789 int 790 filt_randomwrite(struct knote *kn, long hint) 791 { 792 kn->kn_data = POOLBYTES; 793 return (1); 794 } 795 796 int 797 randomioctl(dev_t dev, u_long cmd, caddr_t data, int flag, struct proc *p) 798 { 799 switch (cmd) { 800 case FIOASYNC: 801 /* No async flag in softc so this is a no-op. */ 802 break; 803 case FIONBIO: 804 /* Handled in the upper FS layer. */ 805 break; 806 default: 807 return ENOTTY; 808 } 809 return 0; 810 } 811 812 int 813 sys_getentropy(struct proc *p, void *v, register_t *retval) 814 { 815 struct sys_getentropy_args /* { 816 syscallarg(void *) buf; 817 syscallarg(size_t) nbyte; 818 } */ *uap = v; 819 char buf[256]; 820 int error; 821 822 if (SCARG(uap, nbyte) > sizeof(buf)) 823 return (EIO); 824 arc4random_buf(buf, SCARG(uap, nbyte)); 825 if ((error = copyout(buf, SCARG(uap, buf), SCARG(uap, nbyte))) != 0) 826 return (error); 827 explicit_bzero(buf, sizeof(buf)); 828 *retval = 0; 829 return (0); 830 } 831