lib/libcrypto/arc4random/getentropy_aix.c

   1 /*      $OpenBSD: getentropy_aix.c,v 1.5 2016/08/07 03:27:21 tb Exp $   */
   2
   3 /*
   4  * Copyright (c) 2015 Michael Felt <aixtools@gmail.com>
   5  * Copyright (c) 2014 Theo de Raadt <deraadt@openbsd.org>
   6  * Copyright (c) 2014 Bob Beck <beck@obtuse.com>
   7  *
   8  * Permission to use, copy, modify, and distribute this software for any
   9  * purpose with or without fee is hereby granted, provided that the above
  10  * copyright notice and this permission notice appear in all copies.
  11  *
  12  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  13  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  14  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  15  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  16  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  17  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  18  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  19  *
  20  * Emulation of getentropy(2) as documented at:
  21  * http://man.openbsd.org/getentropy.2
  22  */
  23 /*
  24  * -lperfstat is needed for the psuedo entropy data
  25  */
  26
  27 #include <sys/mman.h>
  28 #include <sys/procfs.h>
  29 #include <sys/protosw.h>
  30 #include <sys/resource.h>
  31 #include <sys/socket.h>
  32 #include <sys/stat.h>
  33 #include <sys/statvfs.h>
  34 #include <sys/timers.h>
  35 #include <errno.h>
  36 #include <fcntl.h>
  37 #include <signal.h>
  38 #include <stdio.h>
  39 #include <string.h>
  40 #include <termios.h>
  41
  42 #include <openssl/sha.h>
  43
  44 #include <libperfstat.h>
  45
  46 #define REPEAT 5
  47 #define min(a, b) (((a) < (b)) ? (a) : (b))
  48
  49 #define HX(a, b) \
  50         do { \
  51                 if ((a)) \
  52                         HD(errno); \
  53                 else \
  54                         HD(b); \
  55         } while (0)
  56
  57 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
  58 #define HD(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
  59 #define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
  60
  61 int     getentropy(void *buf, size_t len);
  62
  63 static int gotdata(char *buf, size_t len);
  64 static int getentropy_urandom(void *buf, size_t len, const char *path,
  65     int devfscheck);
  66 static int getentropy_fallback(void *buf, size_t len);
  67
  68 int
  69 getentropy(void *buf, size_t len)
  70 {
  71         int ret = -1;
  72
  73         if (len > 256) {
  74                 errno = EIO;
  75                 return (-1);
  76         }
  77
  78         /*
  79          * Try to get entropy with /dev/urandom
  80          */
  81         ret = getentropy_urandom(buf, len, "/dev/urandom", 0);
  82         if (ret != -1)
  83                 return (ret);
  84
  85         /*
  86          * Entropy collection via /dev/urandom has failed.
  87          *
  88          * No other API exists for collecting entropy, and we have
  89          * no failsafe way to get it on AIX that is not sensitive
  90          * to resource exhaustion.
  91          *
  92          * We have very few options:
  93          *     - Even syslog_r is unsafe to call at this low level, so
  94          *       there is no way to alert the user or program.
  95          *     - Cannot call abort() because some systems have unsafe
  96          *       corefiles.
  97          *     - Could raise(SIGKILL) resulting in silent program termination.
  98          *     - Return EIO, to hint that arc4random's stir function
  99          *       should raise(SIGKILL)
 100          *     - Do the best under the circumstances....
 101          *
 102          * This code path exists to bring light to the issue that AIX
 103          * does not provide a failsafe API for entropy collection.
 104          *
 105          * We hope this demonstrates that AIX should consider
 106          * providing a new failsafe API which works in a chroot or
 107          * when file descriptors are exhausted.
 108          */
 109 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
 110 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
 111         raise(SIGKILL);
 112 #endif
 113         ret = getentropy_fallback(buf, len);
 114         if (ret != -1)
 115                 return (ret);
 116
 117         errno = EIO;
 118         return (ret);
 119 }
 120
 121 /*
 122  * Basic sanity checking; wish we could do better.
 123  */
 124 static int
 125 gotdata(char *buf, size_t len)
 126 {
 127         char    any_set = 0;
 128         size_t  i;
 129
 130         for (i = 0; i < len; ++i)
 131                 any_set |= buf[i];
 132         if (any_set == 0)
 133                 return (-1);
 134         return (0);
 135 }
 136
 137 static int
 138 getentropy_urandom(void *buf, size_t len, const char *path, int devfscheck)
 139 {
 140         struct stat st;
 141         size_t i;
 142         int fd, flags;
 143         int save_errno = errno;
 144
 145 start:
 146
 147         flags = O_RDONLY;
 148 #ifdef O_NOFOLLOW
 149         flags |= O_NOFOLLOW;
 150 #endif
 151 #ifdef O_CLOEXEC
 152         flags |= O_CLOEXEC;
 153 #endif
 154         fd = open(path, flags, 0);
 155         if (fd == -1) {
 156                 if (errno == EINTR)
 157                         goto start;
 158                 goto nodevrandom;
 159         }
 160 #ifndef O_CLOEXEC
 161         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 162 #endif
 163
 164         /* Lightly verify that the device node looks sane */
 165         if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
 166                 close(fd);
 167                 goto nodevrandom;
 168         }
 169         for (i = 0; i < len; ) {
 170                 size_t wanted = len - i;
 171                 ssize_t ret = read(fd, (char *)buf + i, wanted);
 172
 173                 if (ret == -1) {
 174                         if (errno == EAGAIN || errno == EINTR)
 175                                 continue;
 176                         close(fd);
 177                         goto nodevrandom;
 178                 }
 179                 i += ret;
 180         }
 181         close(fd);
 182         if (gotdata(buf, len) == 0) {
 183                 errno = save_errno;
 184                 return (0);             /* satisfied */
 185         }
 186 nodevrandom:
 187         errno = EIO;
 188         return (-1);
 189 }
 190
 191 static const int cl[] = {
 192         CLOCK_REALTIME,
 193 #ifdef CLOCK_MONOTONIC
 194         CLOCK_MONOTONIC,
 195 #endif
 196 #ifdef CLOCK_MONOTONIC_RAW
 197         CLOCK_MONOTONIC_RAW,
 198 #endif
 199 #ifdef CLOCK_TAI
 200         CLOCK_TAI,
 201 #endif
 202 #ifdef CLOCK_VIRTUAL
 203         CLOCK_VIRTUAL,
 204 #endif
 205 #ifdef CLOCK_UPTIME
 206         CLOCK_UPTIME,
 207 #endif
 208 #ifdef CLOCK_PROCESS_CPUTIME_ID
 209         CLOCK_PROCESS_CPUTIME_ID,
 210 #endif
 211 #ifdef CLOCK_THREAD_CPUTIME_ID
 212         CLOCK_THREAD_CPUTIME_ID,
 213 #endif
 214 };
 215
 216 static int
 217 getentropy_fallback(void *buf, size_t len)
 218 {
 219         uint8_t results[SHA512_DIGEST_LENGTH];
 220         int save_errno = errno, e, pgs = sysconf(_SC_PAGESIZE), faster = 0, repeat;
 221         static int cnt;
 222         struct timespec ts;
 223         struct timeval tv;
 224         perfstat_cpu_total_t cpustats;
 225 #ifdef _AIX61
 226         perfstat_cpu_total_wpar_t cpustats_wpar;
 227 #endif
 228         perfstat_partition_total_t lparstats;
 229         perfstat_disk_total_t diskinfo;
 230         perfstat_netinterface_total_t netinfo;
 231         struct rusage ru;
 232         sigset_t sigset;
 233         struct stat st;
 234         SHA512_CTX ctx;
 235         static pid_t lastpid;
 236         pid_t pid;
 237         size_t i, ii, m;
 238         char *p;
 239
 240         pid = getpid();
 241         if (lastpid == pid) {
 242                 faster = 1;
 243                 repeat = 2;
 244         } else {
 245                 faster = 0;
 246                 lastpid = pid;
 247                 repeat = REPEAT;
 248         }
 249         for (i = 0; i < len; ) {
 250                 int j;
 251                 SHA512_Init(&ctx);
 252                 for (j = 0; j < repeat; j++) {
 253                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 254                         if (e != -1) {
 255                                 cnt += (int)tv.tv_sec;
 256                                 cnt += (int)tv.tv_usec;
 257                         }
 258
 259                         HX(perfstat_cpu_total(NULL, &cpustats,
 260                             sizeof(cpustats), 1) == -1, cpustats);
 261
 262 #ifdef _AIX61
 263                         HX(perfstat_cpu_total_wpar(NULL, &cpustats_wpar,
 264                             sizeof(cpustats_wpar), 1) == -1, cpustats_wpar);
 265 #endif
 266
 267                         HX(perfstat_partition_total(NULL, &lparstats,
 268                             sizeof(lparstats), 1) == -1, lparstats);
 269
 270                         HX(perfstat_disk_total(NULL, &diskinfo,
 271                             sizeof(diskinfo), 1) == -1, diskinfo);
 272
 273                         HX(perfstat_netinterface_total(NULL, &netinfo,
 274                             sizeof(netinfo), 1) == -1, netinfo);
 275
 276                         for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]); ii++)
 277                                 HX(clock_gettime(cl[ii], &ts) == -1, ts);
 278
 279                         HX((pid = getpid()) == -1, pid);
 280                         HX((pid = getsid(pid)) == -1, pid);
 281                         HX((pid = getppid()) == -1, pid);
 282                         HX((pid = getpgid(0)) == -1, pid);
 283                         HX((e = getpriority(0, 0)) == -1, e);
 284
 285                         if (!faster) {
 286                                 ts.tv_sec = 0;
 287                                 ts.tv_nsec = 1;
 288                                 (void) nanosleep(&ts, NULL);
 289                         }
 290
 291                         HX(sigpending(&sigset) == -1, sigset);
 292                         HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
 293                             sigset);
 294
 295                         HF(getentropy); /* an addr in this library */
 296                         HF(printf);             /* an addr in libc */
 297                         p = (char *)&p;
 298                         HD(p);          /* an addr on stack */
 299                         p = (char *)&errno;
 300                         HD(p);          /* the addr of errno */
 301
 302                         if (i == 0) {
 303                                 struct sockaddr_storage ss;
 304                                 struct statvfs stvfs;
 305                                 struct termios tios;
 306                                 socklen_t ssl;
 307                                 off_t off;
 308
 309                                 /*
 310                                  * Prime-sized mappings encourage fragmentation;
 311                                  * thus exposing some address entropy.
 312                                  */
 313                                 struct mm {
 314                                         size_t  npg;
 315                                         void    *p;
 316                                 } mm[] =         {
 317                                         { 17, MAP_FAILED }, { 3, MAP_FAILED },
 318                                         { 11, MAP_FAILED }, { 2, MAP_FAILED },
 319                                         { 5, MAP_FAILED }, { 3, MAP_FAILED },
 320                                         { 7, MAP_FAILED }, { 1, MAP_FAILED },
 321                                         { 57, MAP_FAILED }, { 3, MAP_FAILED },
 322                                         { 131, MAP_FAILED }, { 1, MAP_FAILED },
 323                                 };
 324
 325                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 326                                         HX(mm[m].p = mmap(NULL,
 327                                             mm[m].npg * pgs,
 328                                             PROT_READ|PROT_WRITE,
 329                                             MAP_PRIVATE|MAP_ANON, -1,
 330                                             (off_t)0), mm[m].p);
 331                                         if (mm[m].p != MAP_FAILED) {
 332                                                 size_t mo;
 333
 334                                                 /* Touch some memory... */
 335                                                 p = mm[m].p;
 336                                                 mo = cnt %
 337                                                     (mm[m].npg * pgs - 1);
 338                                                 p[mo] = 1;
 339                                                 cnt += (int)((long)(mm[m].p)
 340                                                     / pgs);
 341                                         }
 342
 343                                         /* Check cnts and times... */
 344                                         for (ii = 0; ii < sizeof(cl)/sizeof(cl[0]);
 345                                             ii++) {
 346                                                 HX((e = clock_gettime(cl[ii],
 347                                                     &ts)) == -1, ts);
 348                                                 if (e != -1)
 349                                                         cnt += (int)ts.tv_nsec;
 350                                         }
 351
 352                                         HX((e = getrusage(RUSAGE_SELF,
 353                                             &ru)) == -1, ru);
 354                                         if (e != -1) {
 355                                                 cnt += (int)ru.ru_utime.tv_sec;
 356                                                 cnt += (int)ru.ru_utime.tv_usec;
 357                                         }
 358                                 }
 359
 360                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 361                                         if (mm[m].p != MAP_FAILED)
 362                                                 munmap(mm[m].p, mm[m].npg * pgs);
 363                                         mm[m].p = MAP_FAILED;
 364                                 }
 365
 366                                 HX(stat(".", &st) == -1, st);
 367                                 HX(statvfs(".", &stvfs) == -1, stvfs);
 368
 369                                 HX(stat("/", &st) == -1, st);
 370                                 HX(statvfs("/", &stvfs) == -1, stvfs);
 371
 372                                 HX((e = fstat(0, &st)) == -1, st);
 373                                 if (e == -1) {
 374                                         if (S_ISREG(st.st_mode) ||
 375                                             S_ISFIFO(st.st_mode) ||
 376                                             S_ISSOCK(st.st_mode)) {
 377                                                 HX(fstatvfs(0, &stvfs) == -1,
 378                                                     stvfs);
 379                                                 HX((off = lseek(0, (off_t)0,
 380                                                     SEEK_CUR)) < 0, off);
 381                                         }
 382                                         if (S_ISCHR(st.st_mode)) {
 383                                                 HX(tcgetattr(0, &tios) == -1,
 384                                                     tios);
 385                                         } else if (S_ISSOCK(st.st_mode)) {
 386                                                 memset(&ss, 0, sizeof ss);
 387                                                 ssl = sizeof(ss);
 388                                                 HX(getpeername(0,
 389                                                     (void *)&ss, &ssl) == -1,
 390                                                     ss);
 391                                         }
 392                                 }
 393
 394                                 HX((e = getrusage(RUSAGE_CHILDREN,
 395                                     &ru)) == -1, ru);
 396                                 if (e != -1) {
 397                                         cnt += (int)ru.ru_utime.tv_sec;
 398                                         cnt += (int)ru.ru_utime.tv_usec;
 399                                 }
 400                         } else {
 401                                 /* Subsequent hashes absorb previous result */
 402                                 HD(results);
 403                         }
 404
 405                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 406                         if (e != -1) {
 407                                 cnt += (int)tv.tv_sec;
 408                                 cnt += (int)tv.tv_usec;
 409                         }
 410
 411                         HD(cnt);
 412                 }
 413                 SHA512_Final(results, &ctx);
 414                 memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 415                 i += min(sizeof(results), len - i);
 416         }
 417         explicit_bzero(&ctx, sizeof ctx);
 418         explicit_bzero(results, sizeof results);
 419         if (gotdata(buf, len) == 0) {
 420                 errno = save_errno;
 421                 return (0);             /* satisfied */
 422         }
 423         errno = EIO;
 424         return (-1);
 425 }