contrib/unbound/compat/getentropy_solaris.c

   1 /*      $OpenBSD: getentropy_solaris.c,v 1.13 2018/11/20 08:04:28 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  * Emulation of getentropy(2) as documented at:
  20  * http://man.openbsd.org/getentropy.2
  21  */
  22
  23 #include "config.h"
  24 #include <sys/types.h>
  25 #include <sys/param.h>
  26 #include <sys/ioctl.h>
  27 #include <sys/resource.h>
  28 #include <sys/syscall.h>
  29 #include <sys/statvfs.h>
  30 #include <sys/socket.h>
  31 #include <sys/mount.h>
  32 #include <sys/mman.h>
  33 #include <sys/stat.h>
  34 #include <sys/time.h>
  35 #include <stdlib.h>
  36 #ifdef HAVE_STDINT_H
  37 #include <stdint.h>
  38 #endif
  39 #include <stdio.h>
  40 #include <link.h>
  41 #include <termios.h>
  42 #include <fcntl.h>
  43 #include <signal.h>
  44 #include <string.h>
  45 #include <errno.h>
  46 #include <unistd.h>
  47 #include <time.h>
  48 #ifdef HAVE_SYS_SHA2_H
  49 #include <sys/sha2.h>
  50 #define SHA512_Init SHA512Init
  51 #define SHA512_Update SHA512Update
  52 #define SHA512_Final SHA512Final
  53 #else
  54 #include "openssl/sha.h"
  55 #endif
  56
  57 #include <sys/vfs.h>
  58 #include <sys/statfs.h>
  59 #include <sys/loadavg.h>
  60
  61 #define REPEAT 5
  62 #define min(a, b) (((a) < (b)) ? (a) : (b))
  63
  64 #define HX(a, b) \
  65         do { \
  66                 if ((a)) \
  67                         HD(errno); \
  68                 else \
  69                         HD(b); \
  70         } while (0)
  71
  72 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
  73 #define HD(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
  74 #define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
  75
  76 int     getentropy(void *buf, size_t len);
  77
  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 static int getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data);
  82
  83 int
  84 getentropy(void *buf, size_t len)
  85 {
  86         int ret = -1;
  87
  88         if (len > 256) {
  89                 errno = EIO;
  90                 return (-1);
  91         }
  92
  93         /*
  94          * Try to get entropy with /dev/urandom
  95          *
  96          * Solaris provides /dev/urandom as a symbolic link to
  97          * /devices/pseudo/random@0:urandom which is provided by
  98          * a devfs filesystem.  Best practice is to use O_NOFOLLOW,
  99          * so we must try the unpublished name directly.
 100          *
 101          * This can fail if the process is inside a chroot which lacks
 102          * the devfs mount, or if file descriptors are exhausted.
 103          */
 104         ret = getentropy_urandom(buf, len,
 105             "/devices/pseudo/random@0:urandom", 1);
 106         if (ret != -1)
 107                 return (ret);
 108
 109         /*
 110          * Unfortunately, chroot spaces on Solaris are sometimes setup
 111          * with direct device node of the well-known /dev/urandom name
 112          * (perhaps to avoid dragging all of devfs into the space).
 113          *
 114          * This can fail if the process is inside a chroot or if file
 115          * descriptors are exhausted.
 116          */
 117         ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
 118         if (ret != -1)
 119                 return (ret);
 120
 121         /*
 122          * Entropy collection via /dev/urandom has failed.
 123          *
 124          * No other API exists for collecting entropy, and we have
 125          * no failsafe way to get it on Solaris that is not sensitive
 126          * to resource exhaustion.
 127          *
 128          * We have very few options:
 129          *     - Even syslog_r is unsafe to call at this low level, so
 130          *       there is no way to alert the user or program.
 131          *     - Cannot call abort() because some systems have unsafe
 132          *       corefiles.
 133          *     - Could raise(SIGKILL) resulting in silent program termination.
 134          *     - Return EIO, to hint that arc4random's stir function
 135          *       should raise(SIGKILL)
 136          *     - Do the best under the circumstances....
 137          *
 138          * This code path exists to bring light to the issue that Solaris
 139          * does not provide a failsafe API for entropy collection.
 140          *
 141          * We hope this demonstrates that Solaris should consider
 142          * providing a new failsafe API which works in a chroot or
 143          * when file descriptors are exhausted.
 144          */
 145 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
 146 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
 147         raise(SIGKILL);
 148 #endif
 149         ret = getentropy_fallback(buf, len);
 150         if (ret != -1)
 151                 return (ret);
 152
 153         errno = EIO;
 154         return (ret);
 155 }
 156
 157 static int
 158 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
 159 {
 160         struct stat st;
 161         size_t i;
 162         int fd, flags;
 163         int save_errno = errno;
 164
 165 start:
 166
 167         flags = O_RDONLY;
 168 #ifdef O_NOFOLLOW
 169         flags |= O_NOFOLLOW;
 170 #endif
 171 #ifdef O_CLOEXEC
 172         flags |= O_CLOEXEC;
 173 #endif
 174         fd = open(path, flags, 0);
 175         if (fd == -1) {
 176                 if (errno == EINTR)
 177                         goto start;
 178                 goto nodevrandom;
 179         }
 180 #ifndef O_CLOEXEC
 181         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 182 #endif
 183
 184         /* Lightly verify that the device node looks sane */
 185         if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode) ||
 186             (devfscheck && (strcmp(st.st_fstype, "devfs") != 0))) {
 187                 close(fd);
 188                 goto nodevrandom;
 189         }
 190         for (i = 0; i < len; ) {
 191                 size_t wanted = len - i;
 192                 ssize_t ret = read(fd, (char *)buf + i, wanted);
 193
 194                 if (ret == -1) {
 195                         if (errno == EAGAIN || errno == EINTR)
 196                                 continue;
 197                         close(fd);
 198                         goto nodevrandom;
 199                 }
 200                 i += ret;
 201         }
 202         close(fd);
 203         errno = save_errno;
 204         return (0);             /* satisfied */
 205 nodevrandom:
 206         errno = EIO;
 207         return (-1);
 208 }
 209
 210 static const int cl[] = {
 211         CLOCK_REALTIME,
 212 #ifdef CLOCK_MONOTONIC
 213         CLOCK_MONOTONIC,
 214 #endif
 215 #ifdef CLOCK_MONOTONIC_RAW
 216         CLOCK_MONOTONIC_RAW,
 217 #endif
 218 #ifdef CLOCK_TAI
 219         CLOCK_TAI,
 220 #endif
 221 #ifdef CLOCK_VIRTUAL
 222         CLOCK_VIRTUAL,
 223 #endif
 224 #ifdef CLOCK_UPTIME
 225         CLOCK_UPTIME,
 226 #endif
 227 #ifdef CLOCK_PROCESS_CPUTIME_ID
 228         CLOCK_PROCESS_CPUTIME_ID,
 229 #endif
 230 #ifdef CLOCK_THREAD_CPUTIME_ID
 231         CLOCK_THREAD_CPUTIME_ID,
 232 #endif
 233 };
 234
 235 static int
 236 getentropy_phdr(struct dl_phdr_info *info, size_t size, void *data)
 237 {
 238         SHA512_CTX *ctx = data;
 239
 240         SHA512_Update(ctx, &info->dlpi_addr, sizeof (info->dlpi_addr));
 241         return (0);
 242 }
 243
 244 static int
 245 getentropy_fallback(void *buf, size_t len)
 246 {
 247         uint8_t results[SHA512_DIGEST_LENGTH];
 248         int save_errno = errno, e, pgs = getpagesize(), faster = 0, repeat;
 249         static int cnt;
 250         struct timespec ts;
 251         struct timeval tv;
 252         double loadavg[3];
 253         struct rusage ru;
 254         sigset_t sigset;
 255         struct stat st;
 256         SHA512_CTX ctx;
 257         static pid_t lastpid;
 258         pid_t pid;
 259         size_t i, ii, m;
 260         char *p;
 261
 262         pid = getpid();
 263         if (lastpid == pid) {
 264                 faster = 1;
 265                 repeat = 2;
 266         } else {
 267                 faster = 0;
 268                 lastpid = pid;
 269                 repeat = REPEAT;
 270         }
 271         for (i = 0; i < len; ) {
 272                 int j;
 273                 SHA512_Init(&ctx);
 274                 for (j = 0; j < repeat; j++) {
 275                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 276                         if (e != -1) {
 277                                 cnt += (int)tv.tv_sec;
 278                                 cnt += (int)tv.tv_usec;
 279                         }
 280
 281                         dl_iterate_phdr(getentropy_phdr, &ctx);
 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                         HF(getentropy); /* an addr in this library */
 304                         HF(printf);             /* an addr in libc */
 305                         p = (char *)&p;
 306                         HD(p);          /* an addr on stack */
 307                         p = (char *)&errno;
 308                         HD(p);          /* the addr of errno */
 309
 310                         if (i == 0) {
 311                                 struct sockaddr_storage ss;
 312                                 struct statvfs stvfs;
 313                                 struct termios tios;
 314                                 socklen_t ssl;
 315                                 off_t off;
 316
 317                                 /*
 318                                  * Prime-sized mappings encourage fragmentation;
 319                                  * thus exposing some address entropy.
 320                                  */
 321                                 struct mm {
 322                                         size_t  npg;
 323                                         void    *p;
 324                                 } mm[] =         {
 325                                         { 17, MAP_FAILED }, { 3, MAP_FAILED },
 326                                         { 11, MAP_FAILED }, { 2, MAP_FAILED },
 327                                         { 5, MAP_FAILED }, { 3, MAP_FAILED },
 328                                         { 7, MAP_FAILED }, { 1, MAP_FAILED },
 329                                         { 57, MAP_FAILED }, { 3, MAP_FAILED },
 330                                         { 131, MAP_FAILED }, { 1, MAP_FAILED },
 331                                 };
 332
 333                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 334                                         HX(mm[m].p = mmap(NULL,
 335                                             mm[m].npg * pgs,
 336                                             PROT_READ|PROT_WRITE,
 337                                             MAP_PRIVATE|MAP_ANON, -1,
 338                                             (off_t)0), mm[m].p);
 339                                         if (mm[m].p != MAP_FAILED) {
 340                                                 size_t mo;
 341
 342                                                 /* Touch some memory... */
 343                                                 p = mm[m].p;
 344                                                 mo = cnt %
 345                                                     (mm[m].npg * pgs - 1);
 346                                                 p[mo] = 1;
 347                                                 cnt += (int)((long)(mm[m].p)
 348                                                     / pgs);
 349                                         }
 350
 351                                         /* Check cnts and times... */
 352                                         for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
 353                                             ii++) {
 354                                                 HX((e = clock_gettime(cl[ii],
 355                                                     &ts)) == -1, ts);
 356                                                 if (e != -1)
 357                                                         cnt += (int)ts.tv_nsec;
 358                                         }
 359
 360                                         HX((e = getrusage(RUSAGE_SELF,
 361                                             &ru)) == -1, ru);
 362                                         if (e != -1) {
 363                                                 cnt += (int)ru.ru_utime.tv_sec;
 364                                                 cnt += (int)ru.ru_utime.tv_usec;
 365                                         }
 366                                 }
 367
 368                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 369                                         if (mm[m].p != MAP_FAILED)
 370                                                 munmap(mm[m].p, mm[m].npg * pgs);
 371                                         mm[m].p = MAP_FAILED;
 372                                 }
 373
 374                                 HX(stat(".", &st) == -1, st);
 375                                 HX(statvfs(".", &stvfs) == -1, stvfs);
 376
 377                                 HX(stat("/", &st) == -1, st);
 378                                 HX(statvfs("/", &stvfs) == -1, stvfs);
 379
 380                                 HX((e = fstat(0, &st)) == -1, st);
 381                                 if (e == -1) {
 382                                         if (S_ISREG(st.st_mode) ||
 383                                             S_ISFIFO(st.st_mode) ||
 384                                             S_ISSOCK(st.st_mode)) {
 385                                                 HX(fstatvfs(0, &stvfs) == -1,
 386                                                     stvfs);
 387                                                 HX((off = lseek(0, (off_t)0,
 388                                                     SEEK_CUR)) < 0, off);
 389                                         }
 390                                         if (S_ISCHR(st.st_mode)) {
 391                                                 HX(tcgetattr(0, &tios) == -1,
 392                                                     tios);
 393                                         } else if (S_ISSOCK(st.st_mode)) {
 394                                                 memset(&ss, 0, sizeof ss);
 395                                                 ssl = sizeof(ss);
 396                                                 HX(getpeername(0,
 397                                                     (void *)&ss, &ssl) == -1,
 398                                                     ss);
 399                                         }
 400                                 }
 401
 402                                 HX((e = getrusage(RUSAGE_CHILDREN,
 403                                     &ru)) == -1, ru);
 404                                 if (e != -1) {
 405                                         cnt += (int)ru.ru_utime.tv_sec;
 406                                         cnt += (int)ru.ru_utime.tv_usec;
 407                                 }
 408                         } else {
 409                                 /* Subsequent hashes absorb previous result */
 410                                 HD(results);
 411                         }
 412
 413                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 414                         if (e != -1) {
 415                                 cnt += (int)tv.tv_sec;
 416                                 cnt += (int)tv.tv_usec;
 417                         }
 418
 419                         HD(cnt);
 420                 }
 421                 SHA512_Final(results, &ctx);
 422                 memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 423                 i += min(sizeof(results), len - i);
 424         }
 425         explicit_bzero(&ctx, sizeof ctx);
 426         explicit_bzero(results, sizeof results);
 427         errno = save_errno;
 428         return (0);             /* satisfied */
 429 }