1 /* $OpenBSD: getentropy_solaris.c,v 1.3 2014/07/12 14:46:31 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 20 #include <sys/types.h> 21 #include <sys/param.h> 22 #include <sys/ioctl.h> 23 #include <sys/resource.h> 24 #include <sys/syscall.h> 25 #include <sys/statvfs.h> 26 #include <sys/socket.h> 27 #include <sys/mount.h> 28 #include <sys/mman.h> 29 #include <sys/stat.h> 30 #include <sys/time.h> 31 #include <stdlib.h> 32 #include <stdint.h> 33 #include <stdio.h> 34 #include <termios.h> 35 #include <fcntl.h> 36 #include <signal.h> 37 #include <string.h> 38 #include <errno.h> 39 #include <unistd.h> 40 #include <time.h> 41 #include <sys/sha2.h> 42 #define SHA512_Init SHA512Init 43 #define SHA512_Update SHA512Update 44 #define SHA512_Final SHA512Final 45 46 #include <sys/vfs.h> 47 #include <sys/statfs.h> 48 #include <sys/loadavg.h> 49 50 #define REPEAT 5 51 #define min(a, b) (((a) < (b)) ? (a) : (b)) 52 53 #define HX(a, b) \ 54 do { \ 55 if ((a)) \ 56 HD(errno); \ 57 else \ 58 HD(b); \ 59 } while (0) 60 61 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l))) 62 #define HD(x) (SHA512_Update(&ctx, (char *)&(x), sizeof (x))) 63 64 int getentropy(void *buf, size_t len); 65 66 extern int main(int, char *argv[]); 67 static int gotdata(char *buf, size_t len); 68 static int getentropy_urandom(void *buf, size_t len, const char *path, 69 int devfscheck); 70 static int getentropy_fallback(void *buf, size_t len); 71 72 int 73 getentropy(void *buf, size_t len) 74 { 75 int ret = -1; 76 77 if (len > 256) { 78 errno = EIO; 79 return -1; 80 } 81 82 /* 83 * Try to get entropy with /dev/urandom 84 * 85 * Solaris provides /dev/urandom as a symbolic link to 86 * /devices/pseudo/random@0:urandom which is provided by 87 * a devfs filesystem. Best practice is to use O_NOFOLLOW, 88 * so we must try the unpublished name directly. 89 * 90 * This can fail if the process is inside a chroot which lacks 91 * the devfs mount, or if file descriptors are exhausted. 92 */ 93 ret = getentropy_urandom(buf, len, 94 "/devices/pseudo/random@0:urandom", 1); 95 if (ret != -1) 96 return (ret); 97 98 /* 99 * Unfortunately, chroot spaces on Solaris are sometimes setup 100 * with direct device node of the well-known /dev/urandom name 101 * (perhaps to avoid dragging all of devfs into the space). 102 * 103 * This can fail if the process is inside a chroot or if file 104 * descriptors are exhausted. 105 */ 106 ret = getentropy_urandom(buf, len, "/dev/urandom", 0); 107 if (ret != -1) 108 return (ret); 109 110 /* 111 * Entropy collection via /dev/urandom has failed. 112 * 113 * No other API exists for collecting entropy, and we have 114 * no failsafe way to get it on Solaris that is not sensitive 115 * to resource exhaustion. 116 * 117 * We have very few options: 118 * - Even syslog_r is unsafe to call at this low level, so 119 * there is no way to alert the user or program. 120 * - Cannot call abort() because some systems have unsafe 121 * corefiles. 122 * - Could raise(SIGKILL) resulting in silent program termination. 123 * - Return EIO, to hint that arc4random's stir function 124 * should raise(SIGKILL) 125 * - Do the best under the circumstances.... 126 * 127 * This code path exists to bring light to the issue that Solaris 128 * does not provide a failsafe API for entropy collection. 129 * 130 * We hope this demonstrates that Solaris should consider 131 * providing a new failsafe API which works in a chroot or 132 * when file descriptors are exhausted. 133 */ 134 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK 135 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK 136 raise(SIGKILL); 137 #endif 138 ret = getentropy_fallback(buf, len); 139 if (ret != -1) 140 return (ret); 141 142 errno = EIO; 143 return (ret); 144 } 145 146 /* 147 * Basic sanity checking; wish we could do better. 148 */ 149 static int 150 gotdata(char *buf, size_t len) 151 { 152 char any_set = 0; 153 size_t i; 154 155 for (i = 0; i < len; ++i) 156 any_set |= buf[i]; 157 if (any_set == 0) 158 return -1; 159 return 0; 160 } 161 162 static int 163 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck) 164 { 165 struct stat st; 166 size_t i; 167 int fd, flags; 168 int save_errno = errno; 169 170 start: 171 172 flags = O_RDONLY; 173 #ifdef O_NOFOLLOW 174 flags |= O_NOFOLLOW; 175 #endif 176 #ifdef O_CLOEXEC 177 flags |= O_CLOEXEC; 178 #endif 179 fd = open(path, flags, 0); 180 if (fd == -1) { 181 if (errno == EINTR) 182 goto start; 183 goto nodevrandom; 184 } 185 #ifndef O_CLOEXEC 186 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC); 187 #endif 188 189 /* Lightly verify that the device node looks sane */ 190 if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) || 191 (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) { 192 close(fd); 193 goto nodevrandom; 194 } 195 for (i = 0; i < len; ) { 196 size_t wanted = len - i; 197 ssize_t ret = read(fd, buf + i, wanted); 198 199 if (ret == -1) { 200 if (errno == EAGAIN || errno == EINTR) 201 continue; 202 close(fd); 203 goto nodevrandom; 204 } 205 i += ret; 206 } 207 close(fd); 208 if (gotdata(buf, len) == 0) { 209 errno = save_errno; 210 return 0; /* satisfied */ 211 } 212 nodevrandom: 213 errno = EIO; 214 return -1; 215 } 216 217 static const int cl[] = { 218 CLOCK_REALTIME, 219 #ifdef CLOCK_MONOTONIC 220 CLOCK_MONOTONIC, 221 #endif 222 #ifdef CLOCK_MONOTONIC_RAW 223 CLOCK_MONOTONIC_RAW, 224 #endif 225 #ifdef CLOCK_TAI 226 CLOCK_TAI, 227 #endif 228 #ifdef CLOCK_VIRTUAL 229 CLOCK_VIRTUAL, 230 #endif 231 #ifdef CLOCK_UPTIME 232 CLOCK_UPTIME, 233 #endif 234 #ifdef CLOCK_PROCESS_CPUTIME_ID 235 CLOCK_PROCESS_CPUTIME_ID, 236 #endif 237 #ifdef CLOCK_THREAD_CPUTIME_ID 238 CLOCK_THREAD_CPUTIME_ID, 239 #endif 240 }; 241 242 static int 243 getentropy_fallback(void *buf, size_t len) 244 { 245 uint8_t results[SHA512_DIGEST_LENGTH]; 246 int save_errno = errno, e, m, pgs = getpagesize(), faster = 0, repeat; 247 static int cnt; 248 struct timespec ts; 249 struct timeval tv; 250 double loadavg[3]; 251 struct rusage ru; 252 sigset_t sigset; 253 struct stat st; 254 SHA512_CTX ctx; 255 static pid_t lastpid; 256 pid_t pid; 257 size_t i, ii; 258 char *p; 259 260 pid = getpid(); 261 if (lastpid == pid) { 262 faster = 1; 263 repeat = 2; 264 } else { 265 faster = 0; 266 lastpid = pid; 267 repeat = REPEAT; 268 } 269 for (i = 0; i < len; ) { 270 int j; 271 SHA512_Init(&ctx); 272 for (j = 0; j < repeat; j++) { 273 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 274 if (e != -1) { 275 cnt += (int)tv.tv_sec; 276 cnt += (int)tv.tv_usec; 277 } 278 279 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++) 280 HX(clock_gettime(cl[ii], &ts) == -1, ts); 281 282 HX((pid = getpid()) == -1, pid); 283 HX((pid = getsid(pid)) == -1, pid); 284 HX((pid = getppid()) == -1, pid); 285 HX((pid = getpgid(0)) == -1, pid); 286 HX((m = getpriority(0, 0)) == -1, m); 287 HX((getloadavg(loadavg, 3) == -1), loadavg); 288 289 if (!faster) { 290 ts.tv_sec = 0; 291 ts.tv_nsec = 1; 292 (void) nanosleep(&ts, NULL); 293 } 294 295 HX(sigpending(&sigset) == -1, sigset); 296 HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1, 297 sigset); 298 299 HD(main); /* an addr in program */ 300 HD(getentropy); /* an addr in this library */ 301 HD(printf); /* an addr in libc */ 302 p = (char *)&p; 303 HD(p); /* an addr on stack */ 304 p = (char *)&errno; 305 HD(p); /* the addr of errno */ 306 307 if (i == 0) { 308 struct sockaddr_storage ss; 309 struct statvfs stvfs; 310 struct termios tios; 311 socklen_t ssl; 312 off_t off; 313 314 /* 315 * Prime-sized mappings encourage fragmentation; 316 * thus exposing some address entropy. 317 */ 318 struct mm { 319 size_t npg; 320 void *p; 321 } mm[] = { 322 { 17, MAP_FAILED }, { 3, MAP_FAILED }, 323 { 11, MAP_FAILED }, { 2, MAP_FAILED }, 324 { 5, MAP_FAILED }, { 3, MAP_FAILED }, 325 { 7, MAP_FAILED }, { 1, MAP_FAILED }, 326 { 57, MAP_FAILED }, { 3, MAP_FAILED }, 327 { 131, MAP_FAILED }, { 1, MAP_FAILED }, 328 }; 329 330 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 331 HX(mm[m].p = mmap(NULL, 332 mm[m].npg * pgs, 333 PROT_READ|PROT_WRITE, 334 MAP_PRIVATE|MAP_ANON, -1, 335 (off_t)0), mm[m].p); 336 if (mm[m].p != MAP_FAILED) { 337 size_t mo; 338 339 /* Touch some memory... */ 340 p = mm[m].p; 341 mo = cnt % 342 (mm[m].npg * pgs - 1); 343 p[mo] = 1; 344 cnt += (int)((long)(mm[m].p) 345 / pgs); 346 } 347 348 /* Check cnts and times... */ 349 for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); 350 ii++) { 351 HX((e = clock_gettime(cl[ii], 352 &ts)) == -1, ts); 353 if (e != -1) 354 cnt += (int)ts.tv_nsec; 355 } 356 357 HX((e = getrusage(RUSAGE_SELF, 358 &ru)) == -1, ru); 359 if (e != -1) { 360 cnt += (int)ru.ru_utime.tv_sec; 361 cnt += (int)ru.ru_utime.tv_usec; 362 } 363 } 364 365 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) { 366 if (mm[m].p != MAP_FAILED) 367 munmap(mm[m].p, mm[m].npg * pgs); 368 mm[m].p = MAP_FAILED; 369 } 370 371 HX(stat(".", &st) == -1, st); 372 HX(statvfs(".", &stvfs) == -1, stvfs); 373 374 HX(stat("/", &st) == -1, st); 375 HX(statvfs("/", &stvfs) == -1, stvfs); 376 377 HX((e = fstat(0, &st)) == -1, st); 378 if (e == -1) { 379 if (S_ISREG(st.st_mode) || 380 S_ISFIFO(st.st_mode) || 381 S_ISSOCK(st.st_mode)) { 382 HX(fstatvfs(0, &stvfs) == -1, 383 stvfs); 384 HX((off = lseek(0, (off_t)0, 385 SEEK_CUR)) < 0, off); 386 } 387 if (S_ISCHR(st.st_mode)) { 388 HX(tcgetattr(0, &tios) == -1, 389 tios); 390 } else if (S_ISSOCK(st.st_mode)) { 391 memset(&ss, 0, sizeof ss); 392 ssl = sizeof(ss); 393 HX(getpeername(0, 394 (void *)&ss, &ssl) == -1, 395 ss); 396 } 397 } 398 399 HX((e = getrusage(RUSAGE_CHILDREN, 400 &ru)) == -1, ru); 401 if (e != -1) { 402 cnt += (int)ru.ru_utime.tv_sec; 403 cnt += (int)ru.ru_utime.tv_usec; 404 } 405 } else { 406 /* Subsequent hashes absorb previous result */ 407 HD(results); 408 } 409 410 HX((e = gettimeofday(&tv, NULL)) == -1, tv); 411 if (e != -1) { 412 cnt += (int)tv.tv_sec; 413 cnt += (int)tv.tv_usec; 414 } 415 416 HD(cnt); 417 } 418 SHA512_Final(results, &ctx); 419 memcpy(buf + i, results, min(sizeof(results), len - i)); 420 i += min(sizeof(results), len - i); 421 } 422 memset(results, 0, sizeof results); 423 if (gotdata(buf, len) == 0) { 424 errno = save_errno; 425 return 0; /* satisfied */ 426 } 427 errno = EIO; 428 return -1; 429 } 430