crypto/rand/rand_unix.c

   1 /*
   2  * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #ifndef _GNU_SOURCE
  11 # define _GNU_SOURCE
  12 #endif
  13 #include "e_os.h"
  14 #include <stdio.h>
  15 #include "internal/cryptlib.h"
  16 #include <openssl/rand.h>
  17 #include "rand_lcl.h"
  18 #include "internal/rand_int.h"
  19 #include <stdio.h>
  20 #include "internal/dso.h"
  21 #if defined(__linux)
  22 # include <asm/unistd.h>
  23 #endif
  24 #if defined(__FreeBSD__) && !defined(OPENSSL_SYS_UEFI)
  25 # include <sys/types.h>
  26 # include <sys/sysctl.h>
  27 # include <sys/param.h>
  28 #endif
  29 #if defined(__OpenBSD__) || defined(__NetBSD__)
  30 # include <sys/param.h>
  31 #endif
  32
  33 #if (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS)) \
  34      || defined(__DJGPP__)
  35 # include <sys/types.h>
  36 # include <sys/stat.h>
  37 # include <fcntl.h>
  38 # include <unistd.h>
  39 # include <sys/time.h>
  40
  41 static uint64_t get_time_stamp(void);
  42 static uint64_t get_timer_bits(void);
  43
  44 /* Macro to convert two thirty two bit values into a sixty four bit one */
  45 # define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
  46
  47 /*
  48  * Check for the existence and support of POSIX timers.  The standard
  49  * says that the _POSIX_TIMERS macro will have a positive value if they
  50  * are available.
  51  *
  52  * However, we want an additional constraint: that the timer support does
  53  * not require an extra library dependency.  Early versions of glibc
  54  * require -lrt to be specified on the link line to access the timers,
  55  * so this needs to be checked for.
  56  *
  57  * It is worse because some libraries define __GLIBC__ but don't
  58  * support the version testing macro (e.g. uClibc).  This means
  59  * an extra check is needed.
  60  *
  61  * The final condition is:
  62  *      "have posix timers and either not glibc or glibc without -lrt"
  63  *
  64  * The nested #if sequences are required to avoid using a parameterised
  65  * macro that might be undefined.
  66  */
  67 # undef OSSL_POSIX_TIMER_OKAY
  68 # if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
  69 #  if defined(__GLIBC__)
  70 #   if defined(__GLIBC_PREREQ)
  71 #    if __GLIBC_PREREQ(2, 17)
  72 #     define OSSL_POSIX_TIMER_OKAY
  73 #    endif
  74 #   endif
  75 #  else
  76 #   define OSSL_POSIX_TIMER_OKAY
  77 #  endif
  78 # endif
  79 #endif /* defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__) */
  80
  81 #if defined(OPENSSL_RAND_SEED_NONE)
  82 /* none means none. this simplifies the following logic */
  83 # undef OPENSSL_RAND_SEED_OS
  84 # undef OPENSSL_RAND_SEED_GETRANDOM
  85 # undef OPENSSL_RAND_SEED_LIBRANDOM
  86 # undef OPENSSL_RAND_SEED_DEVRANDOM
  87 # undef OPENSSL_RAND_SEED_RDTSC
  88 # undef OPENSSL_RAND_SEED_RDCPU
  89 # undef OPENSSL_RAND_SEED_EGD
  90 #endif
  91
  92 #if defined(OPENSSL_SYS_UEFI) && !defined(OPENSSL_RAND_SEED_NONE)
  93 # error "UEFI only supports seeding NONE"
  94 #endif
  95
  96 #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
  97     || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
  98     || defined(OPENSSL_SYS_UEFI))
  99
 100 # if defined(OPENSSL_SYS_VOS)
 101
 102 #  ifndef OPENSSL_RAND_SEED_OS
 103 #   error "Unsupported seeding method configured; must be os"
 104 #  endif
 105
 106 #  if defined(OPENSSL_SYS_VOS_HPPA) && defined(OPENSSL_SYS_VOS_IA32)
 107 #   error "Unsupported HP-PA and IA32 at the same time."
 108 #  endif
 109 #  if !defined(OPENSSL_SYS_VOS_HPPA) && !defined(OPENSSL_SYS_VOS_IA32)
 110 #   error "Must have one of HP-PA or IA32"
 111 #  endif
 112
 113 /*
 114  * The following algorithm repeatedly samples the real-time clock (RTC) to
 115  * generate a sequence of unpredictable data.  The algorithm relies upon the
 116  * uneven execution speed of the code (due to factors such as cache misses,
 117  * interrupts, bus activity, and scheduling) and upon the rather large
 118  * relative difference between the speed of the clock and the rate at which
 119  * it can be read.  If it is ported to an environment where execution speed
 120  * is more constant or where the RTC ticks at a much slower rate, or the
 121  * clock can be read with fewer instructions, it is likely that the results
 122  * would be far more predictable.  This should only be used for legacy
 123  * platforms.
 124  *
 125  * As a precaution, we assume only 2 bits of entropy per byte.
 126  */
 127 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 128 {
 129     short int code;
 130     int i, k;
 131     size_t bytes_needed;
 132     struct timespec ts;
 133     unsigned char v;
 134 #  ifdef OPENSSL_SYS_VOS_HPPA
 135     long duration;
 136     extern void s$sleep(long *_duration, short int *_code);
 137 #  else
 138     long long duration;
 139     extern void s$sleep2(long long *_duration, short int *_code);
 140 #  endif
 141
 142     bytes_needed = rand_pool_bytes_needed(pool, 4 /*entropy_factor*/);
 143
 144     for (i = 0; i < bytes_needed; i++) {
 145         /*
 146          * burn some cpu; hope for interrupts, cache collisions, bus
 147          * interference, etc.
 148          */
 149         for (k = 0; k < 99; k++)
 150             ts.tv_nsec = random();
 151
 152 #  ifdef OPENSSL_SYS_VOS_HPPA
 153         /* sleep for 1/1024 of a second (976 us).  */
 154         duration = 1;
 155         s$sleep(&duration, &code);
 156 #  else
 157         /* sleep for 1/65536 of a second (15 us).  */
 158         duration = 1;
 159         s$sleep2(&duration, &code);
 160 #  endif
 161
 162         /* Get wall clock time, take 8 bits. */
 163         clock_gettime(CLOCK_REALTIME, &ts);
 164         v = (unsigned char)(ts.tv_nsec & 0xFF);
 165         rand_pool_add(pool, arg, &v, sizeof(v) , 2);
 166     }
 167     return rand_pool_entropy_available(pool);
 168 }
 169
 170 void rand_pool_cleanup(void)
 171 {
 172 }
 173
 174 void rand_pool_keep_random_devices_open(int keep)
 175 {
 176 }
 177
 178 # else
 179
 180 #  if defined(OPENSSL_RAND_SEED_EGD) && \
 181         (defined(OPENSSL_NO_EGD) || !defined(DEVRANDOM_EGD))
 182 #   error "Seeding uses EGD but EGD is turned off or no device given"
 183 #  endif
 184
 185 #  if defined(OPENSSL_RAND_SEED_DEVRANDOM) && !defined(DEVRANDOM)
 186 #   error "Seeding uses urandom but DEVRANDOM is not configured"
 187 #  endif
 188
 189 #  if defined(OPENSSL_RAND_SEED_OS)
 190 #   if !defined(DEVRANDOM)
 191 #    error "OS seeding requires DEVRANDOM to be configured"
 192 #   endif
 193 #   define OPENSSL_RAND_SEED_GETRANDOM
 194 #   define OPENSSL_RAND_SEED_DEVRANDOM
 195 #  endif
 196
 197 #  if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 198 #   error "librandom not (yet) supported"
 199 #  endif
 200
 201 #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 202 /*
 203  * sysctl_random(): Use sysctl() to read a random number from the kernel
 204  * Returns the number of bytes returned in buf on success, -1 on failure.
 205  */
 206 static ssize_t sysctl_random(char *buf, size_t buflen)
 207 {
 208     int mib[2];
 209     size_t done = 0;
 210     size_t len;
 211
 212     /*
 213      * Note: sign conversion between size_t and ssize_t is safe even
 214      * without a range check, see comment in syscall_random()
 215      */
 216
 217     /*
 218      * On FreeBSD old implementations returned longs, newer versions support
 219      * variable sizes up to 256 byte. The code below would not work properly
 220      * when the sysctl returns long and we want to request something not a
 221      * multiple of longs, which should never be the case.
 222      */
 223     if (!ossl_assert(buflen % sizeof(long) == 0)) {
 224         errno = EINVAL;
 225         return -1;
 226     }
 227
 228     /*
 229      * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
 230      * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
 231      * it returns a variable number of bytes with the current version supporting
 232      * up to 256 bytes.
 233      * Just return an error on older NetBSD versions.
 234      */
 235 #if   defined(__NetBSD__) && __NetBSD_Version__ < 400000000
 236     errno = ENOSYS;
 237     return -1;
 238 #endif
 239
 240     mib[0] = CTL_KERN;
 241     mib[1] = KERN_ARND;
 242
 243     do {
 244         len = buflen;
 245         if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
 246             return done > 0 ? done : -1;
 247         done += len;
 248         buf += len;
 249         buflen -= len;
 250     } while (buflen > 0);
 251
 252     return done;
 253 }
 254 #  endif
 255
 256 #  if defined(OPENSSL_RAND_SEED_GETRANDOM)
 257 /*
 258  * syscall_random(): Try to get random data using a system call
 259  * returns the number of bytes returned in buf, or < 0 on error.
 260  */
 261 static ssize_t syscall_random(void *buf, size_t buflen)
 262 {
 263     /*
 264      * Note: 'buflen' equals the size of the buffer which is used by the
 265      * get_entropy() callback of the RAND_DRBG. It is roughly bounded by
 266      *
 267      *   2 * RAND_POOL_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^14
 268      *
 269      * which is way below the OSSL_SSIZE_MAX limit. Therefore sign conversion
 270      * between size_t and ssize_t is safe even without a range check.
 271      */
 272
 273     /*
 274      * Do runtime detection to find getentropy().
 275      *
 276      * Known OSs that should support this:
 277      * - Darwin since 16 (OSX 10.12, IOS 10.0).
 278      * - Solaris since 11.3
 279      * - OpenBSD since 5.6
 280      * - Linux since 3.17 with glibc 2.25
 281      * - FreeBSD since 12.0 (1200061)
 282      */
 283 #  if defined(__GNUC__) && __GNUC__>=2 && defined(__ELF__) && !defined(__hpux)
 284     extern int getentropy(void *buffer, size_t length) __attribute__((weak));
 285
 286     if (getentropy != NULL)
 287         return getentropy(buf, buflen) == 0 ? (ssize_t)buflen : -1;
 288 #  elif !defined(FIPS_MODE)
 289     union {
 290         void *p;
 291         int (*f)(void *buffer, size_t length);
 292     } p_getentropy;
 293
 294     /*
 295      * We could cache the result of the lookup, but we normally don't
 296      * call this function often.
 297      */
 298     ERR_set_mark();
 299     p_getentropy.p = DSO_global_lookup("getentropy");
 300     ERR_pop_to_mark();
 301     if (p_getentropy.p != NULL)
 302         return p_getentropy.f(buf, buflen) == 0 ? (ssize_t)buflen : -1;
 303 #  endif
 304
 305     /* Linux supports this since version 3.17 */
 306 #  if defined(__linux) && defined(__NR_getrandom)
 307     return syscall(__NR_getrandom, buf, buflen, 0);
 308 #  elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
 309     return sysctl_random(buf, buflen);
 310 #  else
 311     errno = ENOSYS;
 312     return -1;
 313 #  endif
 314 }
 315 #  endif    /* defined(OPENSSL_RAND_SEED_GETRANDOM) */
 316
 317 #  if defined(OPENSSL_RAND_SEED_DEVRANDOM)
 318 static const char *random_device_paths[] = { DEVRANDOM };
 319 static struct random_device {
 320     int fd;
 321     dev_t dev;
 322     ino_t ino;
 323     mode_t mode;
 324     dev_t rdev;
 325 } random_devices[OSSL_NELEM(random_device_paths)];
 326 static int keep_random_devices_open = 1;
 327
 328 /*
 329  * Verify that the file descriptor associated with the random source is
 330  * still valid. The rationale for doing this is the fact that it is not
 331  * uncommon for daemons to close all open file handles when daemonizing.
 332  * So the handle might have been closed or even reused for opening
 333  * another file.
 334  */
 335 static int check_random_device(struct random_device * rd)
 336 {
 337     struct stat st;
 338
 339     return rd->fd != -1
 340            && fstat(rd->fd, &st) != -1
 341            && rd->dev == st.st_dev
 342            && rd->ino == st.st_ino
 343            && ((rd->mode ^ st.st_mode) & ~(S_IRWXU | S_IRWXG | S_IRWXO)) == 0
 344            && rd->rdev == st.st_rdev;
 345 }
 346
 347 /*
 348  * Open a random device if required and return its file descriptor or -1 on error
 349  */
 350 static int get_random_device(size_t n)
 351 {
 352     struct stat st;
 353     struct random_device * rd = &random_devices[n];
 354
 355     /* reuse existing file descriptor if it is (still) valid */
 356     if (check_random_device(rd))
 357         return rd->fd;
 358
 359     /* open the random device ... */
 360     if ((rd->fd = open(random_device_paths[n], O_RDONLY)) == -1)
 361         return rd->fd;
 362
 363     /* ... and cache its relevant stat(2) data */
 364     if (fstat(rd->fd, &st) != -1) {
 365         rd->dev = st.st_dev;
 366         rd->ino = st.st_ino;
 367         rd->mode = st.st_mode;
 368         rd->rdev = st.st_rdev;
 369     } else {
 370         close(rd->fd);
 371         rd->fd = -1;
 372     }
 373
 374     return rd->fd;
 375 }
 376
 377 /*
 378  * Close a random device making sure it is a random device
 379  */
 380 static void close_random_device(size_t n)
 381 {
 382     struct random_device * rd = &random_devices[n];
 383
 384     if (check_random_device(rd))
 385         close(rd->fd);
 386     rd->fd = -1;
 387 }
 388
 389 int rand_pool_init(void)
 390 {
 391     size_t i;
 392
 393     for (i = 0; i < OSSL_NELEM(random_devices); i++)
 394         random_devices[i].fd = -1;
 395
 396     return 1;
 397 }
 398
 399 void rand_pool_cleanup(void)
 400 {
 401     size_t i;
 402
 403     for (i = 0; i < OSSL_NELEM(random_devices); i++)
 404         close_random_device(i);
 405 }
 406
 407 void rand_pool_keep_random_devices_open(int keep)
 408 {
 409     if (!keep)
 410         rand_pool_cleanup();
 411
 412     keep_random_devices_open = keep;
 413 }
 414
 415 #  else     /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */
 416
 417 int rand_pool_init(void)
 418 {
 419     return 1;
 420 }
 421
 422 void rand_pool_cleanup(void)
 423 {
 424 }
 425
 426 void rand_pool_keep_random_devices_open(int keep)
 427 {
 428 }
 429
 430 #  endif    /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */
 431
 432 /*
 433  * Try the various seeding methods in turn, exit when successful.
 434  *
 435  * TODO(DRBG): If more than one entropy source is available, is it
 436  * preferable to stop as soon as enough entropy has been collected
 437  * (as favored by @rsalz) or should one rather be defensive and add
 438  * more entropy than requested and/or from different sources?
 439  *
 440  * Currently, the user can select multiple entropy sources in the
 441  * configure step, yet in practice only the first available source
 442  * will be used. A more flexible solution has been requested, but
 443  * currently it is not clear how this can be achieved without
 444  * overengineering the problem. There are many parameters which
 445  * could be taken into account when selecting the order and amount
 446  * of input from the different entropy sources (trust, quality,
 447  * possibility of blocking).
 448  */
 449 size_t rand_pool_acquire_entropy(RAND_POOL *pool)
 450 {
 451 #  if defined(OPENSSL_RAND_SEED_NONE)
 452     return rand_pool_entropy_available(pool);
 453 #  else
 454     size_t bytes_needed;
 455     size_t entropy_available = 0;
 456     unsigned char *buffer;
 457
 458 #   if defined(OPENSSL_RAND_SEED_GETRANDOM)
 459     {
 460         ssize_t bytes;
 461         /* Maximum allowed number of consecutive unsuccessful attempts */
 462         int attempts = 3;
 463
 464         bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 465         while (bytes_needed != 0 && attempts-- > 0) {
 466             buffer = rand_pool_add_begin(pool, bytes_needed);
 467             bytes = syscall_random(buffer, bytes_needed);
 468             if (bytes > 0) {
 469                 rand_pool_add_end(pool, bytes, 8 * bytes);
 470                 bytes_needed -= bytes;
 471                 attempts = 3; /* reset counter after successful attempt */
 472             } else if (bytes < 0 && errno != EINTR) {
 473                 break;
 474             }
 475         }
 476     }
 477     entropy_available = rand_pool_entropy_available(pool);
 478     if (entropy_available > 0)
 479         return entropy_available;
 480 #   endif
 481
 482 #   if defined(OPENSSL_RAND_SEED_LIBRANDOM)
 483     {
 484         /* Not yet implemented. */
 485     }
 486 #   endif
 487
 488 #   if defined(OPENSSL_RAND_SEED_DEVRANDOM)
 489     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 490     {
 491         size_t i;
 492
 493         for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths); i++) {
 494             ssize_t bytes = 0;
 495             /* Maximum allowed number of consecutive unsuccessful attempts */
 496             int attempts = 3;
 497             const int fd = get_random_device(i);
 498
 499             if (fd == -1)
 500                 continue;
 501
 502             while (bytes_needed != 0 && attempts-- > 0) {
 503                 buffer = rand_pool_add_begin(pool, bytes_needed);
 504                 bytes = read(fd, buffer, bytes_needed);
 505
 506                 if (bytes > 0) {
 507                     rand_pool_add_end(pool, bytes, 8 * bytes);
 508                     bytes_needed -= bytes;
 509                     attempts = 3; /* reset counter after successful attempt */
 510                 } else if (bytes < 0 && errno != EINTR) {
 511                     break;
 512                 }
 513             }
 514             if (bytes < 0 || !keep_random_devices_open)
 515                 close_random_device(i);
 516
 517             bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 518         }
 519         entropy_available = rand_pool_entropy_available(pool);
 520         if (entropy_available > 0)
 521             return entropy_available;
 522     }
 523 #   endif
 524
 525 #   if defined(OPENSSL_RAND_SEED_RDTSC)
 526     entropy_available = rand_acquire_entropy_from_tsc(pool);
 527     if (entropy_available > 0)
 528         return entropy_available;
 529 #   endif
 530
 531 #   if defined(OPENSSL_RAND_SEED_RDCPU)
 532     entropy_available = rand_acquire_entropy_from_cpu(pool);
 533     if (entropy_available > 0)
 534         return entropy_available;
 535 #   endif
 536
 537 #   if defined(OPENSSL_RAND_SEED_EGD)
 538     bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
 539     if (bytes_needed > 0) {
 540         static const char *paths[] = { DEVRANDOM_EGD, NULL };
 541         int i;
 542
 543         for (i = 0; paths[i] != NULL; i++) {
 544             buffer = rand_pool_add_begin(pool, bytes_needed);
 545             if (buffer != NULL) {
 546                 size_t bytes = 0;
 547                 int num = RAND_query_egd_bytes(paths[i],
 548                                                buffer, (int)bytes_needed);
 549                 if (num == (int)bytes_needed)
 550                     bytes = bytes_needed;
 551
 552                 rand_pool_add_end(pool, bytes, 8 * bytes);
 553                 entropy_available = rand_pool_entropy_available(pool);
 554             }
 555             if (entropy_available > 0)
 556                 return entropy_available;
 557         }
 558     }
 559 #   endif
 560
 561     return rand_pool_entropy_available(pool);
 562 #  endif
 563 }
 564 # endif
 565 #endif
 566
 567 #if (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS)) \
 568      || defined(__DJGPP__)
 569 int rand_pool_add_nonce_data(RAND_POOL *pool)
 570 {
 571     struct {
 572         pid_t pid;
 573         CRYPTO_THREAD_ID tid;
 574         uint64_t time;
 575     } data;
 576
 577     /* Erase the entire structure including any padding */
 578     memset(&data, 0, sizeof(data));
 579
 580     /*
 581      * Add process id, thread id, and a high resolution timestamp to
 582      * ensure that the nonce is unique with high probability for
 583      * different process instances.
 584      */
 585     data.pid = getpid();
 586     data.tid = CRYPTO_THREAD_get_current_id();
 587     data.time = get_time_stamp();
 588
 589     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 590 }
 591
 592 int rand_pool_add_additional_data(RAND_POOL *pool)
 593 {
 594     struct {
 595         CRYPTO_THREAD_ID tid;
 596         uint64_t time;
 597     } data;
 598
 599     /* Erase the entire structure including any padding */
 600     memset(&data, 0, sizeof(data));
 601
 602     /*
 603      * Add some noise from the thread id and a high resolution timer.
 604      * The thread id adds a little randomness if the drbg is accessed
 605      * concurrently (which is the case for the <master> drbg).
 606      */
 607     data.tid = CRYPTO_THREAD_get_current_id();
 608     data.time = get_timer_bits();
 609
 610     return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
 611 }
 612
 613
 614 /*
 615  * Get the current time with the highest possible resolution
 616  *
 617  * The time stamp is added to the nonce, so it is optimized for not repeating.
 618  * The current time is ideal for this purpose, provided the computer's clock
 619  * is synchronized.
 620  */
 621 static uint64_t get_time_stamp(void)
 622 {
 623 # if defined(OSSL_POSIX_TIMER_OKAY)
 624     {
 625         struct timespec ts;
 626
 627         if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
 628             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 629     }
 630 # endif
 631 # if defined(__unix__) \
 632      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 633     {
 634         struct timeval tv;
 635
 636         if (gettimeofday(&tv, NULL) == 0)
 637             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 638     }
 639 # endif
 640     return time(NULL);
 641 }
 642
 643 /*
 644  * Get an arbitrary timer value of the highest possible resolution
 645  *
 646  * The timer value is added as random noise to the additional data,
 647  * which is not considered a trusted entropy sourec, so any result
 648  * is acceptable.
 649  */
 650 static uint64_t get_timer_bits(void)
 651 {
 652     uint64_t res = OPENSSL_rdtsc();
 653
 654     if (res != 0)
 655         return res;
 656
 657 # if defined(__sun) || defined(__hpux)
 658     return gethrtime();
 659 # elif defined(_AIX)
 660     {
 661         timebasestruct_t t;
 662
 663         read_wall_time(&t, TIMEBASE_SZ);
 664         return TWO32TO64(t.tb_high, t.tb_low);
 665     }
 666 # elif defined(OSSL_POSIX_TIMER_OKAY)
 667     {
 668         struct timespec ts;
 669
 670 #  ifdef CLOCK_BOOTTIME
 671 #   define CLOCK_TYPE CLOCK_BOOTTIME
 672 #  elif defined(_POSIX_MONOTONIC_CLOCK)
 673 #   define CLOCK_TYPE CLOCK_MONOTONIC
 674 #  else
 675 #   define CLOCK_TYPE CLOCK_REALTIME
 676 #  endif
 677
 678         if (clock_gettime(CLOCK_TYPE, &ts) == 0)
 679             return TWO32TO64(ts.tv_sec, ts.tv_nsec);
 680     }
 681 # endif
 682 # if defined(__unix__) \
 683      || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 684     {
 685         struct timeval tv;
 686
 687         if (gettimeofday(&tv, NULL) == 0)
 688             return TWO32TO64(tv.tv_sec, tv.tv_usec);
 689     }
 690 # endif
 691     return time(NULL);
 692 }
 693 #endif /* defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__) */