1 /*- 2 * Copyright (c) 2017 Oliver Pinter 3 * Copyright (c) 2000-2015 Mark R V Murray 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 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. 15 * 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. 26 * 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <sys/param.h> 33 #include <sys/systm.h> 34 #include <sys/bus.h> 35 #include <sys/conf.h> 36 #include <sys/fcntl.h> 37 #include <sys/filio.h> 38 #include <sys/kernel.h> 39 #include <sys/kthread.h> 40 #include <sys/lock.h> 41 #include <sys/module.h> 42 #include <sys/malloc.h> 43 #include <sys/poll.h> 44 #include <sys/proc.h> 45 #include <sys/random.h> 46 #include <sys/sbuf.h> 47 #include <sys/selinfo.h> 48 #include <sys/sysctl.h> 49 #include <sys/systm.h> 50 #include <sys/uio.h> 51 #include <sys/unistd.h> 52 53 #include <crypto/rijndael/rijndael-api-fst.h> 54 #include <crypto/sha2/sha256.h> 55 56 #include <dev/random/hash.h> 57 #include <dev/random/randomdev.h> 58 #include <dev/random/random_harvestq.h> 59 60 #define RANDOM_UNIT 0 61 62 /* 63 * In loadable random, the core randomdev.c / random(9) routines have static 64 * visibility and an alternative name to avoid conflicting with the function 65 * pointers of the real names in the core kernel. random_alg_context_init 66 * installs pointers to the loadable static names into the core kernel's 67 * function pointers at SI_SUB_RANDOM:SI_ORDER_SECOND. 68 */ 69 #if defined(RANDOM_LOADABLE) 70 static int (read_random_uio)(struct uio *, bool); 71 static void (read_random)(void *, u_int); 72 static bool (is_random_seeded)(void); 73 #endif 74 75 static d_read_t randomdev_read; 76 static d_write_t randomdev_write; 77 static d_poll_t randomdev_poll; 78 static d_ioctl_t randomdev_ioctl; 79 80 static struct cdevsw random_cdevsw = { 81 .d_name = "random", 82 .d_version = D_VERSION, 83 .d_read = randomdev_read, 84 .d_write = randomdev_write, 85 .d_poll = randomdev_poll, 86 .d_ioctl = randomdev_ioctl, 87 }; 88 89 /* For use with make_dev(9)/destroy_dev(9). */ 90 static struct cdev *random_dev; 91 92 #if defined(RANDOM_LOADABLE) 93 static void 94 random_alg_context_init(void *dummy __unused) 95 { 96 _read_random_uio = (read_random_uio); 97 _read_random = (read_random); 98 _is_random_seeded = (is_random_seeded); 99 } 100 SYSINIT(random_device, SI_SUB_RANDOM, SI_ORDER_SECOND, random_alg_context_init, 101 NULL); 102 #endif 103 104 static struct selinfo rsel; 105 106 /* 107 * This is the read uio(9) interface for random(4). 108 */ 109 /* ARGSUSED */ 110 static int 111 randomdev_read(struct cdev *dev __unused, struct uio *uio, int flags) 112 { 113 114 return ((read_random_uio)(uio, (flags & O_NONBLOCK) != 0)); 115 } 116 117 /* 118 * If the random device is not seeded, blocks until it is seeded. 119 * 120 * Returns zero when the random device is seeded. 121 * 122 * If the 'interruptible' parameter is true, and the device is unseeded, this 123 * routine may be interrupted. If interrupted, it will return either ERESTART 124 * or EINTR. 125 */ 126 #define SEEDWAIT_INTERRUPTIBLE true 127 #define SEEDWAIT_UNINTERRUPTIBLE false 128 static int 129 randomdev_wait_until_seeded(bool interruptible) 130 { 131 int error, spamcount, slpflags; 132 133 slpflags = interruptible ? PCATCH : 0; 134 135 error = 0; 136 spamcount = 0; 137 while (!p_random_alg_context->ra_seeded()) { 138 /* keep tapping away at the pre-read until we seed/unblock. */ 139 p_random_alg_context->ra_pre_read(); 140 /* Only bother the console every 10 seconds or so */ 141 if (spamcount == 0) 142 printf("random: %s unblock wait\n", __func__); 143 spamcount = (spamcount + 1) % 100; 144 error = tsleep(p_random_alg_context, slpflags, "randseed", 145 hz / 10); 146 if (error == ERESTART || error == EINTR) { 147 KASSERT(interruptible, 148 ("unexpected wake of non-interruptible sleep")); 149 break; 150 } 151 /* Squash tsleep timeout condition */ 152 if (error == EWOULDBLOCK) 153 error = 0; 154 KASSERT(error == 0, ("unexpected tsleep error %d", error)); 155 } 156 return (error); 157 } 158 159 int 160 (read_random_uio)(struct uio *uio, bool nonblock) 161 { 162 /* 16 MiB takes about 0.08 s CPU time on my 2017 AMD Zen CPU */ 163 #define SIGCHK_PERIOD (16 * 1024 * 1024) 164 const size_t sigchk_period = SIGCHK_PERIOD; 165 CTASSERT(SIGCHK_PERIOD % PAGE_SIZE == 0); 166 #undef SIGCHK_PERIOD 167 168 uint8_t *random_buf; 169 size_t total_read, read_len; 170 ssize_t bufsize; 171 int error; 172 173 174 KASSERT(uio->uio_rw == UIO_READ, ("%s: bogus write", __func__)); 175 KASSERT(uio->uio_resid >= 0, ("%s: bogus negative resid", __func__)); 176 177 p_random_alg_context->ra_pre_read(); 178 error = 0; 179 /* (Un)Blocking logic */ 180 if (!p_random_alg_context->ra_seeded()) { 181 if (nonblock) 182 error = EWOULDBLOCK; 183 else 184 error = randomdev_wait_until_seeded( 185 SEEDWAIT_INTERRUPTIBLE); 186 } 187 if (error != 0) 188 return (error); 189 190 read_rate_increment(howmany(uio->uio_resid + 1, sizeof(uint32_t))); 191 total_read = 0; 192 193 /* Easy to deal with the trivial 0 byte case. */ 194 if (__predict_false(uio->uio_resid == 0)) 195 return (0); 196 197 /* 198 * If memory is plentiful, use maximally sized requests to avoid 199 * per-call algorithm overhead. But fall back to a single page 200 * allocation if the full request isn't immediately available. 201 */ 202 bufsize = MIN(sigchk_period, (size_t)uio->uio_resid); 203 random_buf = malloc(bufsize, M_ENTROPY, M_NOWAIT); 204 if (random_buf == NULL) { 205 bufsize = PAGE_SIZE; 206 random_buf = malloc(bufsize, M_ENTROPY, M_WAITOK); 207 } 208 209 error = 0; 210 while (uio->uio_resid > 0 && error == 0) { 211 read_len = MIN((size_t)uio->uio_resid, bufsize); 212 213 p_random_alg_context->ra_read(random_buf, read_len); 214 215 /* 216 * uiomove() may yield the CPU before each 'read_len' bytes (up 217 * to bufsize) are copied out. 218 */ 219 error = uiomove(random_buf, read_len, uio); 220 total_read += read_len; 221 222 /* 223 * Poll for signals every few MBs to avoid very long 224 * uninterruptible syscalls. 225 */ 226 if (error == 0 && uio->uio_resid != 0 && 227 total_read % sigchk_period == 0) { 228 error = tsleep_sbt(p_random_alg_context, PCATCH, 229 "randrd", SBT_1NS, 0, C_HARDCLOCK); 230 /* Squash tsleep timeout condition */ 231 if (error == EWOULDBLOCK) 232 error = 0; 233 } 234 } 235 236 /* 237 * Short reads due to signal interrupt should not indicate error. 238 * Instead, the uio will reflect that the read was shorter than 239 * requested. 240 */ 241 if (error == ERESTART || error == EINTR) 242 error = 0; 243 244 explicit_bzero(random_buf, bufsize); 245 free(random_buf, M_ENTROPY); 246 return (error); 247 } 248 249 /*- 250 * Kernel API version of read_random(). This is similar to read_random_uio(), 251 * except it doesn't interface with uio(9). It cannot assumed that random_buf 252 * is a multiple of RANDOM_BLOCKSIZE bytes. 253 * 254 * If the tunable 'kern.random.initial_seeding.bypass_before_seeding' is set 255 * non-zero, silently fail to emit random data (matching the pre-r346250 256 * behavior). If read_random is called prior to seeding and bypassed because 257 * of this tunable, the condition is reported in the read-only sysctl 258 * 'kern.random.initial_seeding.read_random_bypassed_before_seeding'. 259 */ 260 void 261 (read_random)(void *random_buf, u_int len) 262 { 263 264 KASSERT(random_buf != NULL, ("No suitable random buffer in %s", __func__)); 265 p_random_alg_context->ra_pre_read(); 266 267 if (len == 0) 268 return; 269 270 /* (Un)Blocking logic */ 271 if (__predict_false(!p_random_alg_context->ra_seeded())) { 272 if (random_bypass_before_seeding) { 273 if (!read_random_bypassed_before_seeding) { 274 if (!random_bypass_disable_warnings) 275 printf("read_random: WARNING: bypassing" 276 " request for random data because " 277 "the random device is not yet " 278 "seeded and the knob " 279 "'bypass_before_seeding' was " 280 "enabled.\n"); 281 read_random_bypassed_before_seeding = true; 282 } 283 /* Avoid potentially leaking stack garbage */ 284 memset(random_buf, 0, len); 285 return; 286 } 287 288 (void)randomdev_wait_until_seeded(SEEDWAIT_UNINTERRUPTIBLE); 289 } 290 read_rate_increment(roundup2(len, sizeof(uint32_t))); 291 p_random_alg_context->ra_read(random_buf, len); 292 } 293 294 bool 295 (is_random_seeded)(void) 296 { 297 return (p_random_alg_context->ra_seeded()); 298 } 299 300 static __inline void 301 randomdev_accumulate(uint8_t *buf, u_int count) 302 { 303 static u_int destination = 0; 304 static struct harvest_event event; 305 static struct randomdev_hash hash; 306 static uint32_t entropy_data[RANDOM_KEYSIZE_WORDS]; 307 uint32_t timestamp; 308 int i; 309 310 /* Extra timing here is helpful to scrape scheduler jitter entropy */ 311 randomdev_hash_init(&hash); 312 timestamp = (uint32_t)get_cyclecount(); 313 randomdev_hash_iterate(&hash, ×tamp, sizeof(timestamp)); 314 randomdev_hash_iterate(&hash, buf, count); 315 timestamp = (uint32_t)get_cyclecount(); 316 randomdev_hash_iterate(&hash, ×tamp, sizeof(timestamp)); 317 randomdev_hash_finish(&hash, entropy_data); 318 for (i = 0; i < RANDOM_KEYSIZE_WORDS; i += sizeof(event.he_entropy)/sizeof(event.he_entropy[0])) { 319 event.he_somecounter = (uint32_t)get_cyclecount(); 320 event.he_size = sizeof(event.he_entropy); 321 event.he_source = RANDOM_CACHED; 322 event.he_destination = destination++; /* Harmless cheating */ 323 memcpy(event.he_entropy, entropy_data + i, sizeof(event.he_entropy)); 324 p_random_alg_context->ra_event_processor(&event); 325 } 326 explicit_bzero(&event, sizeof(event)); 327 explicit_bzero(entropy_data, sizeof(entropy_data)); 328 } 329 330 /* ARGSUSED */ 331 static int 332 randomdev_write(struct cdev *dev __unused, struct uio *uio, int flags __unused) 333 { 334 uint8_t *random_buf; 335 int c, error = 0; 336 ssize_t nbytes; 337 338 random_buf = malloc(PAGE_SIZE, M_ENTROPY, M_WAITOK); 339 nbytes = uio->uio_resid; 340 while (uio->uio_resid > 0 && error == 0) { 341 c = MIN(uio->uio_resid, PAGE_SIZE); 342 error = uiomove(random_buf, c, uio); 343 if (error) 344 break; 345 randomdev_accumulate(random_buf, c); 346 tsleep(p_random_alg_context, 0, "randwr", hz/10); 347 } 348 if (nbytes != uio->uio_resid && (error == ERESTART || error == EINTR)) 349 /* Partial write, not error. */ 350 error = 0; 351 free(random_buf, M_ENTROPY); 352 return (error); 353 } 354 355 /* ARGSUSED */ 356 static int 357 randomdev_poll(struct cdev *dev __unused, int events, struct thread *td __unused) 358 { 359 360 if (events & (POLLIN | POLLRDNORM)) { 361 if (p_random_alg_context->ra_seeded()) 362 events &= (POLLIN | POLLRDNORM); 363 else 364 selrecord(td, &rsel); 365 } 366 return (events); 367 } 368 369 /* This will be called by the entropy processor when it seeds itself and becomes secure */ 370 void 371 randomdev_unblock(void) 372 { 373 374 selwakeuppri(&rsel, PUSER); 375 wakeup(p_random_alg_context); 376 printf("random: unblocking device.\n"); 377 /* Do random(9) a favour while we are about it. */ 378 (void)atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_NONE, ARC4_ENTR_HAVE); 379 } 380 381 /* ARGSUSED */ 382 static int 383 randomdev_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t addr __unused, 384 int flags __unused, struct thread *td __unused) 385 { 386 int error = 0; 387 388 switch (cmd) { 389 /* Really handled in upper layer */ 390 case FIOASYNC: 391 case FIONBIO: 392 break; 393 default: 394 error = ENOTTY; 395 } 396 397 return (error); 398 } 399 400 /* ARGSUSED */ 401 static int 402 randomdev_modevent(module_t mod __unused, int type, void *data __unused) 403 { 404 int error = 0; 405 406 switch (type) { 407 case MOD_LOAD: 408 printf("random: entropy device external interface\n"); 409 random_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &random_cdevsw, 410 RANDOM_UNIT, NULL, UID_ROOT, GID_WHEEL, 0644, "random"); 411 make_dev_alias(random_dev, "urandom"); /* compatibility */ 412 break; 413 case MOD_UNLOAD: 414 error = EBUSY; 415 break; 416 case MOD_SHUTDOWN: 417 break; 418 default: 419 error = EOPNOTSUPP; 420 break; 421 } 422 return (error); 423 } 424 425 static moduledata_t randomdev_mod = { 426 "random_device", 427 randomdev_modevent, 428 0 429 }; 430 431 DECLARE_MODULE(random_device, randomdev_mod, SI_SUB_DRIVERS, SI_ORDER_FIRST); 432 MODULE_VERSION(random_device, 1); 433 MODULE_DEPEND(random_device, crypto, 1, 1, 1); 434 MODULE_DEPEND(random_device, random_harvestq, 1, 1, 1); 435