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 Best practice is to use O_NOFOLLOW, 92 * so we must try the unpublished name directly. 93 * 94 * This can fail if the process is inside a chroot which lacks 95 * the devfs mount, or if file descriptors are exhausted. 96 */ 97 ret =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