unbound/compat/getentropy_solaris.c

   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 }