getentropy_solaris.c (10911B)
1 /* $OpenBSD: getentropy_solaris.c,v 1.8 2014/07/19 16:12:00 deraadt 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 * Emulation of getentropy(2) as documented at: 20 * http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2 21 */ 22 23 #include <sys/types.h> 24 #include <sys/param.h> 25 #include <sys/ioctl.h> 26 #include <sys/resource.h> 27 #include <sys/syscall.h> 28 #include <sys/statvfs.h> 29 #include <sys/socket.h> 30 #include <sys/mount.h> 31 #include <sys/mman.h> 32 #include <sys/stat.h> 33 #include <sys/time.h> 34 #include <stdlib.h> 35 #include <stdint.h> 36 #include <stdio.h> 37 #include <link.h> 38 #include <termios.h> 39 #include <fcntl.h> 40 #include <signal.h> 41 #include <string.h> 42 #include <errno.h> 43 #include <unistd.h> 44 #include <time.h> 45 #include <sys/sha2.h> 46 #define SHA512_Init SHA512Init 47 #define SHA512_Update SHA512Update 48 #define SHA512_Final SHA512Final 49 50 #include <sys/vfs.h> 51 #include <sys/statfs.h> 52 #include <sys/loadavg.h> 53 54 #define REPEAT 5 55 #define min(a, b) (((a) < (b)) ? (a) : (b)) 56 57 #define HX(a, b) \ 58 do { \ 59 if ((a)) \ 60 HD(errno); \ 61 else \ 62 HD(b); \ 63 } while (0) 64 65 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l))) 66 #define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x))) 67 #define HF(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (void*))) 68 69 int getentropy(void *buf, size_t len); 70 71 static int gotdata(char *buf, size_t len); 72 static int getentropy_urandom(void *buf, size_t len, const char *path, 73 int devfscheck); 74 static int getentropy_fallback(void *buf, size_t len); 75 static int getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data); 76 77 int 78 getentropy(void *buf, size_t len) 79 { 80 int ret = -1; 81 82 if (len > 256) { 83 errno = EIO; 84 return -1; 85 } 86 87 /* 88 * Try to get entropy with /dev/urandom 89 * 90 * Solaris provides /dev/urandom as a symbolic link to 91 * /devices/pseudo/random@0:urandom which is provided by 92 * a devfs filesystem. Best practice is to use O_NOFOLLOW, 93 * so we must try the unpublished name directly. 94 * 95 * This can fail if the process is inside a chroot which lacks 96 * the devfs mount, or if file descriptors are exhausted. 97 */ 98 ret = getentropy_urandom(buf, len, 99 "/devices/pseudo/random@0:urandom", 1); 100 if (ret != -1) 101 return (ret); 102 103 /* 104 * Unfortunately, chroot spaces on Solaris are sometimes setup 105 * with direct device node of the well-known /dev/urandom name 106 * (perhaps to avoid dragging all of devfs into the space). 107 * 108 * This can fail if the process is inside a chroot or if file 109 * descriptors are exhausted. 110 */ 111 ret = getentropy_urandom(buf, len, "/dev/urandom", 0); 112 if (ret != -1) 113 return (ret); 114 115 /* 116 * Entropy collection via /dev/urandom has failed. 117 * 118 * No other API exists for collecting entropy, and we have 119 * no failsafe way to get it on Solaris that is not sensitive 120 * to resource exhaustion. 121 * 122 * We have very few options: 123 * - Even syslog_r is unsafe to call at this low level, so 124 * there is no way to alert the user or program. 125 * - Cannot call abort() because some systems have unsafe 126 * corefiles. 127 * - Could raise(SIGKILL) resulting in silent program termination. 128 * - Return EIO, to hint that arc4random's stir function 129 * should raise(SIGKILL) 130 * - Do the best under the circumstances.... 131 * 132 * This code path exists to bring light to the issue that Solaris 133 * does not provide a failsafe API for entropy collection. 134 * 135 * We hope this demonstrates that Solaris should consider 136 * providing a new failsafe API which works in a chroot or 137 * when file descriptors are exhausted. 138 */ 139 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK 140 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK 141 raise(SIGKILL); 142 #endif 143 ret = getentropy_fallback(buf, len); 144 if (ret != -1) 145 return (ret); 146 147 errno = EIO; 148 return (ret); 149 } 150 151 /* 152 * Basic sanity checking; wish we could do better. 153 */ 154 static int 155 gotdata(char *buf, size_t len) 156 { 157 char any_set = 0; 158 size_t i; 159 160 for (i = 0; i < len; ++i) 161 any_set |= buf[i]; 162 if (any_set == 0) 163 return -1; 164 return 0; 165 } 166 167 static int 168 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck) 169 { 170 struct stat st; 171 size_t i; 172 int fd, flags; 173 int save_errno = errno; 174 175 start: 176 177 flags = O_RDONLY; 178 #ifdef O_NOFOLLOW 179 flags |= O_NOFOLLOW; 180 #endif 181 #ifdef O_CLOEXEC 182 flags |= O_CLOEXEC; 183 #endif 184 fd = open(path, flags, 0); 185 if (fd == -1) { 186 if (errno == EINTR) 187 goto start; 188 goto nodevrandom; 189 } 190 #ifndef O_CLOEXEC 191 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC); 192 #endif 193 194 /* Lightly verify that the device node looks sane */ 195 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) || 196 (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) { 197 close(fd); 198 goto nodevrandom; 199 } 200 for (i = 0; i < len; ) { 201 size_t wanted = len - i; 202 ssize_t ret = read(fd, (char *)buf + i, wanted); 203 204 if (ret == -1) { 205 if (errno == EAGAIN || errno == EINTR) 206 continue; 207 close(fd); 208 goto nodevrandom; 209 } 210 i += ret; 211 } 212 close(fd); 213 if (gotdata(buf, len) == 0) { 214 errno = save_errno; 215 return 0; /* satisfied */ 216 } 217 nodevrandom: 218 errno = EIO; 219 return -1; 220 } 221 222 static const int cl[] = { 223 CLOCK_REALTIME, 224 #ifdef CLOCK_MONOTONIC 225 CLOCK_MONOTONIC, 226 #endif 227 #ifdef CLOCK_MONOTONIC_RAW 228 CLOCK_MONOTONIC_RAW, 229 #endif 230 #ifdef CLOCK_TAI 231 CLOCK_TAI, 232 #endif 233 #ifdef CLOCK_VIRTUAL 234 CLOCK_VIRTUAL, 235 #endif 236 #ifdef CLOCK_UPTIME 237 CLOCK_UPTIME, 238 #endif 239 #ifdef CLOCK_PROCESS_CPUTIME_ID 240 CLOCK_PROCESS_CPUTIME_ID, 241 #endif 242 #ifdef CLOCK_THREAD_CPUTIME_ID 243 CLOCK_THREAD_CPUTIME_ID, 244 #endif 245 }; 246 247 static int 248 getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data) 249 { 250 SHA512_CTX *ctx = data; 251 252 SHA512_Update(ctx, &info->dlpi_addr, sizeof (info->dlpi_addr)); 253 return 0; 254 } 255 256 static int 257 getentropy_fallback(void *buf, size_t len) 258 { 259 uint8_t results[SHA512_DIGEST_LENGTH]; 260 int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat; 261 static int cnt; 262 struct timespec ts; 263 struct timeval tv; 264 double loadavg[3]; 265 struct rusage ru; 266 sigset_t sigset; 267 struct stat st; 268 SHA512_CTX ctx; 269 static pid_t lastpid; 270 pid_t pid; 271 size_t i, ii, m; 272 char *p; 273 274 pid = getpid(); 275 if (lastpid == pid) { 276 faster = 1; 277 repeat = 2; 278 } else { 279 faster = 0; 280 lastpid = pid; 281 repeat = REPEAT; 282 } 283 for (i = 0; i < len; ) { 284 int j; 285 SHA512_Init(&ctx); 286 for (j = 0; j < repeat; j++) { 287 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 288 if (e != -1) { 289 cnt += (int)tv.tv_sec; 290 cnt += (int)tv.tv_usec; 291 } 292 293 dl_iterate_phdr(getentropy_phdr, &ctx); 294 295 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++) 296 HX(clock_gettime(cl[ii], &ts) == -1, ts); 297 298 HX((pid = getpid()) == -1, pid); 299 HX((pid = getsid(pid)) == -1, pid); 300 HX((pid = getppid()) == -1, pid); 301 HX((pid = getpgid(0)) == -1, pid); 302 HX((e = getpriority(0, 0)) == -1, e); 303 HX((getloadavg(loadavg, 3) == -1), loadavg); 304 305 if (!faster) { 306 ts.tv_sec = 0; 307 ts.tv_nsec = 1; 308 (void) nanosleep(&ts, NULL); 309 } 310 311 HX(sigpending(&sigset) == -1, sigset); 312 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1, 313 sigset); 314 315 HF(getentropy); /* an addr in this library */ 316 HF(printf); /* an addr in libc */ 317 p = (char *)&p; 318 HD(p); /* an addr on stack */ 319 p = (char *)&errno; 320 HD(p); /* the addr of errno */ 321 322 if (i == 0) { 323 struct sockaddr_storage ss; 324 struct statvfs stvfs; 325 struct termios tios; 326 socklen_t ssl; 327 off_t off; 328 329 /* 330 * Prime-sized mappings encourage fragmentation; 331 * thus exposing some address entropy. 332 */ 333 struct mm { 334 size_t npg; 335 void *p; 336 } mm[] = { 337 { 17, MAP_FAILED }, { 3, MAP_FAILED }, 338 { 11, MAP_FAILED }, { 2, MAP_FAILED }, 339 { 5, MAP_FAILED }, { 3, MAP_FAILED }, 340 { 7, MAP_FAILED }, { 1, MAP_FAILED }, 341 { 57, MAP_FAILED }, { 3, MAP_FAILED }, 342 { 131, MAP_FAILED }, { 1, MAP_FAILED }, 343 }; 344 345 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 346 HX(mm[m].p = mmap(NULL, 347 mm[m].npg * pgs, 348 PROT_READ|PROT_WRITE, 349 MAP_PRIVATE|MAP_ANON, -1, 350 (off_t)0), mm[m].p); 351 if (mm[m].p != MAP_FAILED) { 352 size_t mo; 353 354 /* Touch some memory... */ 355 p = mm[m].p; 356 mo = cnt % 357 (mm[m].npg * pgs - 1); 358 p[mo] = 1; 359 cnt += (int)((long)(mm[m].p) 360 / pgs); 361 } 362 363 /* Check cnts and times... */ 364 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); 365 ii++) { 366 HX((e = clock_gettime(cl[ii], 367 &ts)) == -1, ts); 368 if (e != -1) 369 cnt += (int)ts.tv_nsec; 370 } 371 372 HX((e = getrusage(RUSAGE_SELF, 373 &ru)) == -1, ru); 374 if (e != -1) { 375 cnt += (int)ru.ru_utime.tv_sec; 376 cnt += (int)ru.ru_utime.tv_usec; 377 } 378 } 379 380 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 381 if (mm[m].p != MAP_FAILED) 382 munmap(mm[m].p, mm[m].npg * pgs); 383 mm[m].p = MAP_FAILED; 384 } 385 386 HX(stat(".", &st) == -1, st); 387 HX(statvfs(".", &stvfs) == -1, stvfs); 388 389 HX(stat("/", &st) == -1, st); 390 HX(statvfs("/", &stvfs) == -1, stvfs); 391 392 HX((e = fstat(0, &st)) == -1, st); 393 if (e == -1) { 394 if (S_ISREG(st.st_mode) || 395 S_ISFIFO(st.st_mode) || 396 S_ISSOCK(st.st_mode)) { 397 HX(fstatvfs(0, &stvfs) == -1, 398 stvfs); 399 HX((off = lseek(0, (off_t)0, 400 SEEK_CUR)) < 0, off); 401 } 402 if (S_ISCHR(st.st_mode)) { 403 HX(tcgetattr(0, &tios) == -1, 404 tios); 405 } else if (S_ISSOCK(st.st_mode)) { 406 memset(&ss, 0, sizeof ss); 407 ssl = sizeof(ss); 408 HX(getpeername(0, 409 (void *)&ss, &ssl) == -1, 410 ss); 411 } 412 } 413 414 HX((e = getrusage(RUSAGE_CHILDREN, 415 &ru)) == -1, ru); 416 if (e != -1) { 417 cnt += (int)ru.ru_utime.tv_sec; 418 cnt += (int)ru.ru_utime.tv_usec; 419 } 420 } else { 421 /* Subsequent hashes absorb previous result */ 422 HD(results); 423 } 424 425 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 426 if (e != -1) { 427 cnt += (int)tv.tv_sec; 428 cnt += (int)tv.tv_usec; 429 } 430 431 HD(cnt); 432 } 433 SHA512_Final(results, &ctx); 434 memcpy((char *)buf + i, results, min(sizeof(results), len - i)); 435 i += min(sizeof(results), len - i); 436 } 437 explicit_bzero(&ctx, sizeof ctx); 438 explicit_bzero(results, sizeof results); 439 if (gotdata(buf, len) == 0) { 440 errno = save_errno; 441 return 0; /* satisfied */ 442 } 443 errno = EIO; 444 return -1; 445 }