crypto/libressl/crypto/compat/getentropy_osx.c

   1 /*      $OpenBSD: getentropy_osx.c,v 1.8 2014/07/21 20:19:47 guenther 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://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/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/sysctl.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 #include <stdint.h>
  37 #include <stdio.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 <mach/mach_time.h>
  46 #include <mach/mach_host.h>
  47 #include <mach/host_info.h>
  48 #include <sys/socketvar.h>
  49 #include <sys/vmmeter.h>
  50 #include <netinet/in.h>
  51 #include <netinet/tcp.h>
  52 #include <netinet/udp.h>
  53 #include <netinet/ip_var.h>
  54 #include <netinet/tcp_var.h>
  55 #include <netinet/udp_var.h>
  56 #include <CommonCrypto/CommonDigest.h>
  57 #define SHA512_Update(a, b, c)  (CC_SHA512_Update((a), (b), (c)))
  58 #define SHA512_Init(xxx) (CC_SHA512_Init((xxx)))
  59 #define SHA512_Final(xxx, yyy) (CC_SHA512_Final((xxx), (yyy)))
  60 #define SHA512_CTX CC_SHA512_CTX
  61 #define SHA512_DIGEST_LENGTH CC_SHA512_DIGEST_LENGTH
  62
  63 #define REPEAT 5
  64 #define min(a, b) (((a) < (b)) ? (a) : (b))
  65
  66 #define HX(a, b) \
  67         do { \
  68                 if ((a)) \
  69                         HD(errno); \
  70                 else \
  71                         HD(b); \
  72         } while (0)
  73
  74 #define HR(x, l) (SHA512_Update(&ctx, (char *)(x), (l)))
  75 #define HD(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (x)))
  76 #define HF(x)    (SHA512_Update(&ctx, (char *)&(x), sizeof (void*)))
  77
  78 int     getentropy(void *buf, size_t len);
  79
  80 static int gotdata(char *buf, size_t len);
  81 static int getentropy_urandom(void *buf, size_t len);
  82 static int getentropy_fallback(void *buf, size_t len);
  83
  84 int
  85 getentropy(void *buf, size_t len)
  86 {
  87         int ret = -1;
  88
  89         if (len > 256) {
  90                 errno = EIO;
  91                 return (-1);
  92         }
  93
  94         /*
  95          * Try to get entropy with /dev/urandom
  96          *
  97          * This can fail if the process is inside a chroot or if file
  98          * descriptors are exhausted.
  99          */
 100         ret = getentropy_urandom(buf, len);
 101         if (ret != -1)
 102                 return (ret);
 103
 104         /*
 105          * Entropy collection via /dev/urandom and sysctl have failed.
 106          *
 107          * No other API exists for collecting entropy, and we have
 108          * no failsafe way to get it on OSX that is not sensitive
 109          * to resource exhaustion.
 110          *
 111          * We have very few options:
 112          *     - Even syslog_r is unsafe to call at this low level, so
 113          *       there is no way to alert the user or program.
 114          *     - Cannot call abort() because some systems have unsafe
 115          *       corefiles.
 116          *     - Could raise(SIGKILL) resulting in silent program termination.
 117          *     - Return EIO, to hint that arc4random's stir function
 118          *       should raise(SIGKILL)
 119          *     - Do the best under the circumstances....
 120          *
 121          * This code path exists to bring light to the issue that OSX
 122          * does not provide a failsafe API for entropy collection.
 123          *
 124          * We hope this demonstrates that OSX should consider
 125          * providing a new failsafe API which works in a chroot or
 126          * when file descriptors are exhausted.
 127          */
 128 #undef FAIL_INSTEAD_OF_TRYING_FALLBACK
 129 #ifdef FAIL_INSTEAD_OF_TRYING_FALLBACK
 130         raise(SIGKILL);
 131 #endif
 132         ret = getentropy_fallback(buf, len);
 133         if (ret != -1)
 134                 return (ret);
 135
 136         errno = EIO;
 137         return (ret);
 138 }
 139
 140 /*
 141  * Basic sanity checking; wish we could do better.
 142  */
 143 static int
 144 gotdata(char *buf, size_t len)
 145 {
 146         char    any_set = 0;
 147         size_t  i;
 148
 149         for (i = 0; i < len; ++i)
 150                 any_set |= buf[i];
 151         if (any_set == 0)
 152                 return (-1);
 153         return (0);
 154 }
 155
 156 static int
 157 getentropy_urandom(void *buf, size_t len)
 158 {
 159         struct stat st;
 160         size_t i;
 161         int fd, flags;
 162         int save_errno = errno;
 163
 164 start:
 165
 166         flags = O_RDONLY;
 167 #ifdef O_NOFOLLOW
 168         flags |= O_NOFOLLOW;
 169 #endif
 170 #ifdef O_CLOEXEC
 171         flags |= O_CLOEXEC;
 172 #endif
 173         fd = open("/dev/urandom", flags, 0);
 174         if (fd == -1) {
 175                 if (errno == EINTR)
 176                         goto start;
 177                 goto nodevrandom;
 178         }
 179 #ifndef O_CLOEXEC
 180         fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
 181 #endif
 182
 183         /* Lightly verify that the device node looks sane */
 184         if (fstat(fd, &st) == -1 || !S_ISCHR(st.st_mode)) {
 185                 close(fd);
 186                 goto nodevrandom;
 187         }
 188         for (i = 0; i < len; ) {
 189                 size_t wanted = len - i;
 190                 ssize_t ret = read(fd, (char *)buf + i, wanted);
 191
 192                 if (ret == -1) {
 193                         if (errno == EAGAIN || errno == EINTR)
 194                                 continue;
 195                         close(fd);
 196                         goto nodevrandom;
 197                 }
 198                 i += ret;
 199         }
 200         close(fd);
 201         if (gotdata(buf, len) == 0) {
 202                 errno = save_errno;
 203                 return (0);             /* satisfied */
 204         }
 205 nodevrandom:
 206         errno = EIO;
 207         return (-1);
 208 }
 209
 210 static int tcpmib[] = { CTL_NET, AF_INET, IPPROTO_TCP, TCPCTL_STATS };
 211 static int udpmib[] = { CTL_NET, AF_INET, IPPROTO_UDP, UDPCTL_STATS };
 212 static int ipmib[] = { CTL_NET, AF_INET, IPPROTO_IP, IPCTL_STATS };
 213 static int kmib[] = { CTL_KERN, KERN_USRSTACK };
 214 static int hwmib[] = { CTL_HW, HW_USERMEM };
 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 = getpagesize(), faster = 0, repeat;
 221         static int cnt;
 222         struct timespec ts;
 223         struct timeval tv;
 224         struct rusage ru;
 225         sigset_t sigset;
 226         struct stat st;
 227         SHA512_CTX ctx;
 228         static pid_t lastpid;
 229         pid_t pid;
 230         size_t i, ii, m;
 231         char *p;
 232         struct tcpstat tcpstat;
 233         struct udpstat udpstat;
 234         struct ipstat ipstat;
 235         u_int64_t mach_time;
 236         unsigned int idata;
 237         void *addr;
 238
 239         pid = getpid();
 240         if (lastpid == pid) {
 241                 faster = 1;
 242                 repeat = 2;
 243         } else {
 244                 faster = 0;
 245                 lastpid = pid;
 246                 repeat = REPEAT;
 247         }
 248         for (i = 0; i < len; ) {
 249                 int j;
 250                 SHA512_Init(&ctx);
 251                 for (j = 0; j < repeat; j++) {
 252                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 253                         if (e != -1) {
 254                                 cnt += (int)tv.tv_sec;
 255                                 cnt += (int)tv.tv_usec;
 256                         }
 257
 258                         mach_time = mach_absolute_time();
 259                         HD(mach_time);
 260
 261                         ii = sizeof(addr);
 262                         HX(sysctl(kmib, sizeof(kmib) / sizeof(kmib[0]),
 263                             &addr, &ii, NULL, 0) == -1, addr);
 264
 265                         ii = sizeof(idata);
 266                         HX(sysctl(hwmib, sizeof(hwmib) / sizeof(hwmib[0]),
 267                             &idata, &ii, NULL, 0) == -1, idata);
 268
 269                         ii = sizeof(tcpstat);
 270                         HX(sysctl(tcpmib, sizeof(tcpmib) / sizeof(tcpmib[0]),
 271                             &tcpstat, &ii, NULL, 0) == -1, tcpstat);
 272
 273                         ii = sizeof(udpstat);
 274                         HX(sysctl(udpmib, sizeof(udpmib) / sizeof(udpmib[0]),
 275                             &udpstat, &ii, NULL, 0) == -1, udpstat);
 276
 277                         ii = sizeof(ipstat);
 278                         HX(sysctl(ipmib, sizeof(ipmib) / sizeof(ipmib[0]),
 279                             &ipstat, &ii, NULL, 0) == -1, ipstat);
 280
 281                         HX((pid = getpid()) == -1, pid);
 282                         HX((pid = getsid(pid)) == -1, pid);
 283                         HX((pid = getppid()) == -1, pid);
 284                         HX((pid = getpgid(0)) == -1, pid);
 285                         HX((e = getpriority(0, 0)) == -1, e);
 286
 287                         if (!faster) {
 288                                 ts.tv_sec = 0;
 289                                 ts.tv_nsec = 1;
 290                                 (void) nanosleep(&ts, NULL);
 291                         }
 292
 293                         HX(sigpending(&sigset) == -1, sigset);
 294                         HX(sigprocmask(SIG_BLOCK, NULL, &sigset) == -1,
 295                             sigset);
 296
 297                         HF(getentropy); /* an addr in this library */
 298                         HF(printf);             /* an addr in libc */
 299                         p = (char *)&p;
 300                         HD(p);          /* an addr on stack */
 301                         p = (char *)&errno;
 302                         HD(p);          /* the addr of errno */
 303
 304                         if (i == 0) {
 305                                 struct sockaddr_storage ss;
 306                                 struct statvfs stvfs;
 307                                 struct termios tios;
 308                                 struct statfs stfs;
 309                                 socklen_t ssl;
 310                                 off_t off;
 311
 312                                 /*
 313                                  * Prime-sized mappings encourage fragmentation;
 314                                  * thus exposing some address entropy.
 315                                  */
 316                                 struct mm {
 317                                         size_t  npg;
 318                                         void    *p;
 319                                 } mm[] =         {
 320                                         { 17, MAP_FAILED }, { 3, MAP_FAILED },
 321                                         { 11, MAP_FAILED }, { 2, MAP_FAILED },
 322                                         { 5, MAP_FAILED }, { 3, MAP_FAILED },
 323                                         { 7, MAP_FAILED }, { 1, MAP_FAILED },
 324                                         { 57, MAP_FAILED }, { 3, MAP_FAILED },
 325                                         { 131, MAP_FAILED }, { 1, MAP_FAILED },
 326                                 };
 327
 328                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 329                                         HX(mm[m].p = mmap(NULL,
 330                                             mm[m].npg * pgs,
 331                                             PROT_READ|PROT_WRITE,
 332                                             MAP_PRIVATE|MAP_ANON, -1,
 333                                             (off_t)0), mm[m].p);
 334                                         if (mm[m].p != MAP_FAILED) {
 335                                                 size_t mo;
 336
 337                                                 /* Touch some memory... */
 338                                                 p = mm[m].p;
 339                                                 mo = cnt %
 340                                                     (mm[m].npg * pgs - 1);
 341                                                 p[mo] = 1;
 342                                                 cnt += (int)((long)(mm[m].p)
 343                                                     / pgs);
 344                                         }
 345
 346                                         /* Check cnts and times... */
 347                                         mach_time = mach_absolute_time();
 348                                         HD(mach_time);
 349                                         cnt += (int)mach_time;
 350
 351                                         HX((e = getrusage(RUSAGE_SELF,
 352                                             &ru)) == -1, ru);
 353                                         if (e != -1) {
 354                                                 cnt += (int)ru.ru_utime.tv_sec;
 355                                                 cnt += (int)ru.ru_utime.tv_usec;
 356                                         }
 357                                 }
 358
 359                                 for (m = 0; m < sizeof mm/sizeof(mm[0]); m++) {
 360                                         if (mm[m].p != MAP_FAILED)
 361                                                 munmap(mm[m].p, mm[m].npg * pgs);
 362                                         mm[m].p = MAP_FAILED;
 363                                 }
 364
 365                                 HX(stat(".", &st) == -1, st);
 366                                 HX(statvfs(".", &stvfs) == -1, stvfs);
 367                                 HX(statfs(".", &stfs) == -1, stfs);
 368
 369                                 HX(stat("/", &st) == -1, st);
 370                                 HX(statvfs("/", &stvfs) == -1, stvfs);
 371                                 HX(statfs("/", &stfs) == -1, stfs);
 372
 373                                 HX((e = fstat(0, &st)) == -1, st);
 374                                 if (e == -1) {
 375                                         if (S_ISREG(st.st_mode) ||
 376                                             S_ISFIFO(st.st_mode) ||
 377                                             S_ISSOCK(st.st_mode)) {
 378                                                 HX(fstatvfs(0, &stvfs) == -1,
 379                                                     stvfs);
 380                                                 HX(fstatfs(0, &stfs) == -1,
 381                                                     stfs);
 382                                                 HX((off = lseek(0, (off_t)0,
 383                                                     SEEK_CUR)) < 0, off);
 384                                         }
 385                                         if (S_ISCHR(st.st_mode)) {
 386                                                 HX(tcgetattr(0, &tios) == -1,
 387                                                     tios);
 388                                         } else if (S_ISSOCK(st.st_mode)) {
 389                                                 memset(&ss, 0, sizeof ss);
 390                                                 ssl = sizeof(ss);
 391                                                 HX(getpeername(0,
 392                                                     (void *)&ss, &ssl) == -1,
 393                                                     ss);
 394                                         }
 395                                 }
 396
 397                                 HX((e = getrusage(RUSAGE_CHILDREN,
 398                                     &ru)) == -1, ru);
 399                                 if (e != -1) {
 400                                         cnt += (int)ru.ru_utime.tv_sec;
 401                                         cnt += (int)ru.ru_utime.tv_usec;
 402                                 }
 403                         } else {
 404                                 /* Subsequent hashes absorb previous result */
 405                                 HD(results);
 406                         }
 407
 408                         HX((e = gettimeofday(&tv, NULL)) == -1, tv);
 409                         if (e != -1) {
 410                                 cnt += (int)tv.tv_sec;
 411                                 cnt += (int)tv.tv_usec;
 412                         }
 413
 414                         HD(cnt);
 415                 }
 416
 417                 SHA512_Final(results, &ctx);
 418                 memcpy((char *)buf + i, results, min(sizeof(results), len - i));
 419                 i += min(sizeof(results), len - i);
 420         }
 421         explicit_bzero(&ctx, sizeof ctx);
 422         explicit_bzero(results, sizeof results);
 423         if (gotdata(buf, len) == 0) {
 424                 errno = save_errno;
 425                 return (0);             /* satisfied */
 426         }
 427         errno = EIO;
 428         return (-1);
 429 }