lib/libcrypto/arc4random/getentropy_solaris.c

   1 /*      $OpenBSD: getentropy_solaris.c,v 1.12 2016/08/07 03:27:21 tb 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://man.openbsd.org/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 }