1 /* $OpenBSD: getentropy_solaris.c,v 1.4 2014/07/12 20:41:47 wouter Exp $ */ 2 3 /* 4 * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org> 5 * Copyright (c) 2014 Bob Beck <beck@obtuse.com> 6 * 7 * Permission to use, copy, modify, and distribute this software for any 8 * purpose with or without fee is hereby granted, provided that the above 9 * copyright notice and this permission notice appear in all copies. 10 * 11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 18 */ 19 #include "config.h" 20 21 #include <sys/types.h> 22 #include <sys/param.h> 23 #include <sys/ioctl.h> 24 #include <sys/resource.h> 25 #include <sys/syscall.h> 26 #include <sys/statvfs.h> 27 #include <sys/socket.h> 28 #include <sys/mount.h> 29 #include <sys/mman.h> 30 #include <sys/stat.h> 31 #include <sys/time.h> 32 #include <stdlib.h> 33 #ifdef HAVE_STDINT_H 34 #include <stdint.h> 35 #endif 36 #include <stdio.h> 37 #include <termios.h> 38 #include <fcntl.h> 39 #include <signal.h> 40 #include <string.h> 41 #include <errno.h> 42 #include <unistd.h> 43 #include <time.h> 44 #ifdef HAVE_SYS_SHA2_H 45 #include <sys/sha2.h> 46 #define SHA512_Init SHA512Init 47 #define SHA512_Update SHA512Update 48 #define SHA512_Final SHA512Final 49 #else 50 #include <openssl/sha.h> 51 #endif 52 53 #include <sys/vfs.h> 54 #include <sys/statfs.h> 55 #include <sys/loadavg.h> 56 57 #define REPEAT 5 58 #define min(a, b) (((a) < (b)) ? (a) : (b)) 59 60 #define HX(a, b) \ 61 do { \ 62 if ((a)) \ 63 HD(errno); \ 64 else \ 65 HD(b); \ 66 } while (0) 67 68 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l))) 69 #define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x))) 70 #define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*))) 71 72 int getentropy(void *buf, size_t len); 73 74 #ifdef CAN_REFERENCE_MAIN 75 extern int main(int, char *argv[]); 76 #endif 77 static int gotdata(char *buf, size_t len); 78 static int getentropy_urandom(void *buf, size_t len, const char *path, 79 int devfscheck); 80 static int getentropy_fallback(void *buf, size_t len); 81 82 int 83 getentropy(void *buf, size_t len) 84 { 85 int ret = -1; 86 87 if (len > 256) { 88 errno = EIO; 89 return -1; 90 } 91 92 /* 93 * Try to get entropy with /dev/urandom 94 * 95 * Solaris provides /dev/urandom as a symbolic link to 96 * /devices/pseudo/random@0:urandom which is provided by 97 * a devfs filesystem. Best practice is to use O_NOFOLLOW, 98 * so we must try the unpublished name directly. 99 * 100 * This can fail if the process is inside a chroot which lacks 101 * the devfs mount, or if file descriptors are exhausted. 102 */ 103 ret = getentropy_urandom(buf, len, 104 "/devices/pseudo/random@0:urandom", 1); 105 if (ret != -1) 106 return (ret); 107 108 /* 109 * Unfortunately, chroot spaces on Solaris are sometimes setup 110 * with direct device node of the well-known /dev/urandom name 111 * (perhaps to avoid dragging all of devfs into the space). 112 * 113 * This can fail if the process is inside a chroot or if file 114 * descriptors are exhausted. 115 */ 116 ret = getentropy_urandom(buf, len, "/dev/urandom", 0); 117 if (ret != -1) 118 return (ret); 119 120 /* 121 * Entropy collection via /dev/urandom has failed. 122 * 123 * No other API exists for collecting entropy, and we have 124 * no failsafe way to get it on Solaris that is not sensitive 125 * to resource exhaustion. 126 * 127 * We have very few options: 128 * - Even syslog_r is unsafe to call at this low level, so 129 * there is no way to alert the user or program. 130 * - Cannot call abort() because some systems have unsafe 131 * corefiles. 132 * - Could raise(SIGKILL) resulting in silent program termination. 133 * - Return EIO, to hint that arc4random's stir function 134 * should raise(SIGKILL) 135 * - Do the best under the circumstances.... 136 * 137 * This code path exists to bring light to the issue that Solaris 138 * does not provide a failsafe API for entropy collection. 139 * 140 * We hope this demonstrates that Solaris should consider 141 * providing a new failsafe API which works in a chroot or 142 * when file descriptors are exhausted. 143 */ 144 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK 145 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK 146 raise(SIGKILL); 147 #endif 148 ret = getentropy_fallback(buf, len); 149 if (ret != -1) 150 return (ret); 151 152 errno = EIO; 153 return (ret); 154 } 155 156 /* 157 * Basic sanity checking; wish we could do better. 158 */ 159 static int 160 gotdata(char *buf, size_t len) 161 { 162 char any_set = 0; 163 size_t i; 164 165 for (i = 0; i < len; ++i) 166 any_set |= buf[i]; 167 if (any_set == 0) 168 return -1; 169 return 0; 170 } 171 172 static int 173 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck) 174 { 175 struct stat st; 176 size_t i; 177 int fd, flags; 178 int save_errno = errno; 179 180 start: 181 182 flags = O_RDONLY; 183 #ifdef O_NOFOLLOW 184 flags |= O_NOFOLLOW; 185 #endif 186 #ifdef O_CLOEXEC 187 flags |= O_CLOEXEC; 188 #endif 189 fd = open(path, flags, 0); 190 if (fd == -1) { 191 if (errno == EINTR) 192 goto start; 193 goto nodevrandom; 194 } 195 #ifndef O_CLOEXEC 196 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC); 197 #endif 198 199 /* Lightly verify that the device node looks sane */ 200 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) || 201 (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) { 202 close(fd); 203 goto nodevrandom; 204 } 205 for (i = 0; i < len; ) { 206 size_t wanted = len - i; 207 ssize_t ret = read(fd, (char *)buf + i, wanted); 208 209 if (ret == -1) { 210 if (errno == EAGAIN || errno == EINTR) 211 continue; 212 close(fd); 213 goto nodevrandom; 214 } 215 i += ret; 216 } 217 close(fd); 218 if (gotdata(buf, len) == 0) { 219 errno = save_errno; 220 return 0; /* satisfied */ 221 } 222 nodevrandom: 223 errno = EIO; 224 return -1; 225 } 226 227 static const int cl[] = { 228 CLOCK_REALTIME, 229 #ifdef CLOCK_MONOTONIC 230 CLOCK_MONOTONIC, 231 #endif 232 #ifdef CLOCK_MONOTONIC_RAW 233 CLOCK_MONOTONIC_RAW, 234 #endif 235 #ifdef CLOCK_TAI 236 CLOCK_TAI, 237 #endif 238 #ifdef CLOCK_VIRTUAL 239 CLOCK_VIRTUAL, 240 #endif 241 #ifdef CLOCK_UPTIME 242 CLOCK_UPTIME, 243 #endif 244 #ifdef CLOCK_PROCESS_CPUTIME_ID 245 CLOCK_PROCESS_CPUTIME_ID, 246 #endif 247 #ifdef CLOCK_THREAD_CPUTIME_ID 248 CLOCK_THREAD_CPUTIME_ID, 249 #endif 250 }; 251 252 static int 253 getentropy_fallback(void *buf, size_t len) 254 { 255 uint8_t results[SHA512_DIGEST_LENGTH]; 256 int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat; 257 static int cnt; 258 struct timespec ts; 259 struct timeval tv; 260 double loadavg[3]; 261 struct rusage ru; 262 sigset_t sigset; 263 struct stat st; 264 SHA512_CTX ctx; 265 static pid_t lastpid; 266 pid_t pid; 267 size_t i, ii, m; 268 char *p; 269 270 pid = getpid(); 271 if (lastpid == pid) { 272 faster = 1; 273 repeat = 2; 274 } else { 275 faster = 0; 276 lastpid = pid; 277 repeat = REPEAT; 278 } 279 for (i = 0; i < len; ) { 280 int j; 281 SHA512_Init(&ctx); 282 for (j = 0; j < repeat; j++) { 283 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 284 if (e != -1) { 285 cnt += (int)tv.tv_sec; 286 cnt += (int)tv.tv_usec; 287 } 288 289 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++) 290 HX(clock_gettime(cl[ii], &ts) == -1, ts); 291 292 HX((pid = getpid()) == -1, pid); 293 HX((pid = getsid(pid)) == -1, pid); 294 HX((pid = getppid()) == -1, pid); 295 HX((pid = getpgid(0)) == -1, pid); 296 HX((e = getpriority(0, 0)) == -1, e); 297 HX((getloadavg(loadavg, 3) == -1), loadavg); 298 299 if (!faster) { 300 ts.tv_sec = 0; 301 ts.tv_nsec = 1; 302 (void) nanosleep(&ts, NULL); 303 } 304 305 HX(sigpending(&sigset) == -1, sigset); 306 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1, 307 sigset); 308 309 #ifdef CAN_REFERENCE_MAIN 310 HF(main); /* an addr in program */ 311 #endif 312 HF(getentropy); /* an addr in this library */ 313 HF(printf); /* an addr in libc */ 314 p = (char *)&p; 315 HD(p); /* an addr on stack */ 316 p = (char *)&errno; 317 HD(p); /* the addr of errno */ 318 319 if (i == 0) { 320 struct sockaddr_storage ss; 321 struct statvfs stvfs; 322 struct termios tios; 323 socklen_t ssl; 324 off_t off; 325 326 /* 327 * Prime-sized mappings encourage fragmentation; 328 * thus exposing some address entropy. 329 */ 330 struct mm { 331 size_t npg; 332 void *p; 333 } mm[] = { 334 { 17, MAP_FAILED }, { 3, MAP_FAILED }, 335 { 11, MAP_FAILED }, { 2, MAP_FAILED }, 336 { 5, MAP_FAILED }, { 3, MAP_FAILED }, 337 { 7, MAP_FAILED }, { 1, MAP_FAILED }, 338 { 57, MAP_FAILED }, { 3, MAP_FAILED }, 339 { 131, MAP_FAILED }, { 1, MAP_FAILED }, 340 }; 341 342 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 343 HX(mm[m].p = mmap(NULL, 344 mm[m].npg * pgs, 345 PROT_READ|PROT_WRITE, 346 MAP_PRIVATE|MAP_ANON, -1, 347 (off_t)0), mm[m].p); 348 if (mm[m].p != MAP_FAILED) { 349 size_t mo; 350 351 /* Touch some memory... */ 352 p = mm[m].p; 353 mo = cnt % 354 (mm[m].npg * pgs - 1); 355 p[mo] = 1; 356 cnt += (int)((long)(mm[m].p) 357 / pgs); 358 } 359 360 /* Check cnts and times... */ 361 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); 362 ii++) { 363 HX((e = clock_gettime(cl[ii], 364 &ts)) == -1, ts); 365 if (e != -1) 366 cnt += (int)ts.tv_nsec; 367 } 368 369 HX((e = getrusage(RUSAGE_SELF, 370 &ru)) == -1, ru); 371 if (e != -1) { 372 cnt += (int)ru.ru_utime.tv_sec; 373 cnt += (int)ru.ru_utime.tv_usec; 374 } 375 } 376 377 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 378 if (mm[m].p != MAP_FAILED) 379 munmap(mm[m].p, mm[m].npg * pgs); 380 mm[m].p = MAP_FAILED; 381 } 382 383 HX(stat(".", &st) == -1, st); 384 HX(statvfs(".", &stvfs) == -1, stvfs); 385 386 HX(stat("/", &st) == -1, st); 387 HX(statvfs("/", &stvfs) == -1, stvfs); 388 389 HX((e = fstat(0, &st)) == -1, st); 390 if (e == -1) { 391 if (S_ISREG(st.st_mode) || 392 S_ISFIFO(st.st_mode) || 393 S_ISSOCK(st.st_mode)) { 394 HX(fstatvfs(0, &stvfs) == -1, 395 stvfs); 396 HX((off = lseek(0, (off_t)0, 397 SEEK_CUR)) < 0, off); 398 } 399 if (S_ISCHR(st.st_mode)) { 400 HX(tcgetattr(0, &tios) == -1, 401 tios); 402 } else if (S_ISSOCK(st.st_mode)) { 403 memset(&ss, 0, sizeof ss); 404 ssl = sizeof(ss); 405 HX(getpeername(0, 406 (void *)&ss, &ssl) == -1, 407 ss); 408 } 409 } 410 411 HX((e = getrusage(RUSAGE_CHILDREN, 412 &ru)) == -1, ru); 413 if (e != -1) { 414 cnt += (int)ru.ru_utime.tv_sec; 415 cnt += (int)ru.ru_utime.tv_usec; 416 } 417 } else { 418 /* Subsequent hashes absorb previous result */ 419 HD(results); 420 } 421 422 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 423 if (e != -1) { 424 cnt += (int)tv.tv_sec; 425 cnt += (int)tv.tv_usec; 426 } 427 428 HD(cnt); 429 } 430 SHA512_Final(results, &ctx); 431 memcpy((char *)buf + i, results, min(sizeof(results), len - i)); 432 i += min(sizeof(results), len - i); 433 } 434 memset(results, 0, sizeof results); 435 if (gotdata(buf, len) == 0) { 436 errno = save_errno; 437 return 0; /* satisfied */ 438 } 439 errno = EIO; 440 return -1; 441 } 442