contrib/unbound/compat/getentropy_solaris.c

   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 }