text: /*
   * Copyright 1995-2020 The OpenSSL Project Authors. All Rights Reserved.
   *
   * Licensed under the OpenSSL license (the "License").  You may not use
   * this file except in compliance with the License.  You can obtain a copy
   * in the file LICENSE in the source distribution or at
   * https://www.openssl.org/source/license.html
   */
  
  #ifndef _GNU_SOURCE
  # define _GNU_SOURCE
  #endif
  #include "e_os.h"
  #include <stdio.h>
  #include "internal/cryptlib.h"
  #include <openssl/rand.h>
  #include <openssl/crypto.h>
  #include "rand_local.h"
  #include "crypto/rand.h"
  #include <stdio.h>
  #include "internal/dso.h"
  #ifdef __linux
  # include <sys/syscall.h>
  # ifdef DEVRANDOM_WAIT
  #  include <sys/shm.h>
  #  include <sys/utsname.h>
  # endif
  #endif
  #if defined(__FreeBSD__) && !defined(OPENSSL_SYS_UEFI)
  # include <sys/types.h>
  # include <sys/sysctl.h>
  # include <sys/param.h>
  #endif
  #if defined(__OpenBSD__) || defined(__NetBSD__)
  # include <sys/param.h>
  #endif
  
  #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
  # include <sys/types.h>
  # include <sys/stat.h>
  # include <fcntl.h>
  # include <unistd.h>
  # include <sys/time.h>
  
  static uint64_t get_time_stamp(void);
  static uint64_t get_timer_bits(void);
  
  /* Macro to convert two thirty two bit values into a sixty four bit one */
  # define TWO32TO64(a, b) ((((uint64_t)(a)) << 32) + (b))
  
  /*
   * Check for the existence and support of POSIX timers.  The standard
   * says that the _POSIX_TIMERS macro will have a positive value if they
   * are available.
   *
   * However, we want an additional constraint: that the timer support does
   * not require an extra library dependency.  Early versions of glibc
   * require -lrt to be specified on the link line to access the timers,
   * so this needs to be checked for.
   *
   * It is worse because some libraries define __GLIBC__ but don't
   * support the version testing macro (e.g. uClibc).  This means
   * an extra check is needed.
   *
   * The final condition is:
   *      "have posix timers and either not glibc or glibc without -lrt"
   *
   * The nested #if sequences are required to avoid using a parameterised
   * macro that might be undefined.
   */
  # undef OSSL_POSIX_TIMER_OKAY
  # if defined(_POSIX_TIMERS) && _POSIX_TIMERS > 0
  #  if defined(__GLIBC__)
  #   if defined(__GLIBC_PREREQ)
  #    if __GLIBC_PREREQ(2, 17)
  #     define OSSL_POSIX_TIMER_OKAY
  #    endif
  #   endif
  #  else
  #   define OSSL_POSIX_TIMER_OKAY
  #  endif
  # endif
  #endif /* (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS))
            || defined(__DJGPP__) */
  
  #if defined(OPENSSL_RAND_SEED_NONE)
  /* none means none. this simplifies the following logic */
  # undef OPENSSL_RAND_SEED_OS
  # undef OPENSSL_RAND_SEED_GETRANDOM
  # undef OPENSSL_RAND_SEED_LIBRANDOM
  # undef OPENSSL_RAND_SEED_DEVRANDOM
  # undef OPENSSL_RAND_SEED_RDTSC
  # undef OPENSSL_RAND_SEED_RDCPU
  # undef OPENSSL_RAND_SEED_EGD
  #endif
  
  #if (defined(OPENSSL_SYS_VXWORKS) || defined(OPENSSL_SYS_UEFI)) && \
          !defined(OPENSSL_RAND_SEED_NONE)
  # error "UEFI and VXWorks only support seeding NONE"
  #endif
  
  #if defined(OPENSSL_SYS_VXWORKS)
  /* empty implementation */
  int rand_pool_init(void)
  {
      return 1;
  }
  
  void rand_pool_cleanup(void)
  {
  }
  
  void rand_pool_keep_random_devices_open(int keep)
  {
  }
  
  size_t rand_pool_acquire_entropy(RAND_POOL *pool)
  {
      return rand_pool_entropy_available(pool);
  }
  #endif
  
  #if !(defined(OPENSSL_SYS_WINDOWS) || defined(OPENSSL_SYS_WIN32) \
      || defined(OPENSSL_SYS_VMS) || defined(OPENSSL_SYS_VXWORKS) \
      || defined(OPENSSL_SYS_UEFI))
  
  # if defined(OPENSSL_SYS_VOS)
  
  #  ifndef OPENSSL_RAND_SEED_OS
  #   error "Unsupported seeding method configured; must be os"
  #  endif
  
  #  if defined(OPENSSL_SYS_VOS_HPPA) && defined(OPENSSL_SYS_VOS_IA32)
  #   error "Unsupported HP-PA and IA32 at the same time."
  #  endif
  #  if !defined(OPENSSL_SYS_VOS_HPPA) && !defined(OPENSSL_SYS_VOS_IA32)
  #   error "Must have one of HP-PA or IA32"
  #  endif
  
  /*
   * The following algorithm repeatedly samples the real-time clock (RTC) to
   * generate a sequence of unpredictable data.  The algorithm relies upon the
   * uneven execution speed of the code (due to factors such as cache misses,
   * interrupts, bus activity, and scheduling) and upon the rather large
   * relative difference between the speed of the clock and the rate at which
   * it can be read.  If it is ported to an environment where execution speed
   * is more constant or where the RTC ticks at a much slower rate, or the
   * clock can be read with fewer instructions, it is likely that the results
   * would be far more predictable.  This should only be used for legacy
   * platforms.
   *
   * As a precaution, we assume only 2 bits of entropy per byte.
   */
  size_t rand_pool_acquire_entropy(RAND_POOL *pool)
  {
      short int code;
      int i, k;
      size_t bytes_needed;
      struct timespec ts;
      unsigned char v;
  #  ifdef OPENSSL_SYS_VOS_HPPA
      long duration;
      extern void s$sleep(long *_duration, short int *_code);
  #  else
      long long duration;
      extern void s$sleep2(long long *_duration, short int *_code);
  #  endif
  
      bytes_needed = rand_pool_bytes_needed(pool, 4 /*entropy_factor*/);
  
      for (i = 0; i < bytes_needed; i++) {
          /*
           * burn some cpu; hope for interrupts, cache collisions, bus
           * interference, etc.
           */
          for (k = 0; k < 99; k++)
              ts.tv_nsec = random();
  
  #  ifdef OPENSSL_SYS_VOS_HPPA
          /* sleep for 1/1024 of a second (976 us).  */
          duration = 1;
          s$sleep(&duration, &code);
  #  else
          /* sleep for 1/65536 of a second (15 us).  */
          duration = 1;
          s$sleep2(&duration, &code);
  #  endif
  
          /* Get wall clock time, take 8 bits. */
          clock_gettime(CLOCK_REALTIME, &ts);
          v = (unsigned char)(ts.tv_nsec & 0xFF);
          rand_pool_add(pool, arg, &v, sizeof(v) , 2);
      }
      return rand_pool_entropy_available(pool);
  }
  
  void rand_pool_cleanup(void)
  {
  }
  
  void rand_pool_keep_random_devices_open(int keep)
  {
  }
  
  # else
  
  #  if defined(OPENSSL_RAND_SEED_EGD) && \
          (defined(OPENSSL_NO_EGD) || !defined(DEVRANDOM_EGD))
  #   error "Seeding uses EGD but EGD is turned off or no device given"
  #  endif
  
  #  if defined(OPENSSL_RAND_SEED_DEVRANDOM) && !defined(DEVRANDOM)
  #   error "Seeding uses urandom but DEVRANDOM is not configured"
  #  endif
  
  #  if defined(OPENSSL_RAND_SEED_OS)
  #   if !defined(DEVRANDOM)
  #    error "OS seeding requires DEVRANDOM to be configured"
  #   endif
  #   define OPENSSL_RAND_SEED_GETRANDOM
  #   define OPENSSL_RAND_SEED_DEVRANDOM
  #  endif
  
  #  if defined(OPENSSL_RAND_SEED_LIBRANDOM)
  #   error "librandom not (yet) supported"
  #  endif
  
  #  if (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
  /*
   * sysctl_random(): Use sysctl() to read a random number from the kernel
   * Returns the number of bytes returned in buf on success, -1 on failure.
   */
  static ssize_t sysctl_random(char *buf, size_t buflen)
  {
      int mib[2];
      size_t done = 0;
      size_t len;
  
      /*
       * Note: sign conversion between size_t and ssize_t is safe even
       * without a range check, see comment in syscall_random()
       */
  
      /*
       * On FreeBSD old implementations returned longs, newer versions support
       * variable sizes up to 256 byte. The code below would not work properly
       * when the sysctl returns long and we want to request something not a
       * multiple of longs, which should never be the case.
       */
      if (!ossl_assert(buflen % sizeof(long) == 0)) {
          errno = EINVAL;
          return -1;
      }
  
      /*
       * On NetBSD before 4.0 KERN_ARND was an alias for KERN_URND, and only
       * filled in an int, leaving the rest uninitialized. Since NetBSD 4.0
       * it returns a variable number of bytes with the current version supporting
       * up to 256 bytes.
       * Just return an error on older NetBSD versions.
       */
  #if   defined(__NetBSD__) && __NetBSD_Version__ < 400000000
      errno = ENOSYS;
      return -1;
  #endif
  
      mib[0] = CTL_KERN;
      mib[1] = KERN_ARND;
  
      do {
          len = buflen;
          if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
              return done > 0 ? done : -1;
          done += len;
          buf += len;
          buflen -= len;
      } while (buflen > 0);
  
      return done;
  }
  #  endif
  
  #  if defined(OPENSSL_RAND_SEED_GETRANDOM)
  
  #   if defined(__linux) && !defined(__NR_getrandom)
  #    if defined(__arm__)
  #     define __NR_getrandom    (__NR_SYSCALL_BASE+384)
  #    elif defined(__i386__)
  #     define __NR_getrandom    355
  #    elif defined(__x86_64__)
  #     if defined(__ILP32__)
  #      define __NR_getrandom   (__X32_SYSCALL_BIT + 318)
  #     else
  #      define __NR_getrandom   318
  #     endif
  #    elif defined(__xtensa__)
  #     define __NR_getrandom    338
  #    elif defined(__s390__) || defined(__s390x__)
  #     define __NR_getrandom    349
  #    elif defined(__bfin__)
  #     define __NR_getrandom    389
  #    elif defined(__powerpc__)
  #     define __NR_getrandom    359
  #    elif defined(__mips__) || defined(__mips64)
  #     if _MIPS_SIM == _MIPS_SIM_ABI32
  #      define __NR_getrandom   (__NR_Linux + 353)
  #     elif _MIPS_SIM == _MIPS_SIM_ABI64
  #      define __NR_getrandom   (__NR_Linux + 313)
  #     elif _MIPS_SIM == _MIPS_SIM_NABI32
  #      define __NR_getrandom   (__NR_Linux + 317)
  #     endif
  #    elif defined(__hppa__)
  #     define __NR_getrandom    (__NR_Linux + 339)
  #    elif defined(__sparc__)
  #     define __NR_getrandom    347
  #    elif defined(__ia64__)
  #     define __NR_getrandom    1339
  #    elif defined(__alpha__)
  #     define __NR_getrandom    511
  #    elif defined(__sh__)
  #     if defined(__SH5__)
  #      define __NR_getrandom   373
  #     else
  #      define __NR_getrandom   384
  #     endif
  #    elif defined(__avr32__)
  #     define __NR_getrandom    317
  #    elif defined(__microblaze__)
  #     define __NR_getrandom    385
  #    elif defined(__m68k__)
  #     define __NR_getrandom    352
  #    elif defined(__cris__)
  #     define __NR_getrandom    356
  #    elif defined(__aarch64__)
  #     define __NR_getrandom    278
  #    else /* generic */
  #     define __NR_getrandom    278
  #    endif
  #   endif
  
  /*
   * syscall_random(): Try to get random data using a system call
   * returns the number of bytes returned in buf, or < 0 on error.
   */
  static ssize_t syscall_random(void *buf, size_t buflen)
  {
      /*
       * Note: 'buflen' equals the size of the buffer which is used by the
       * get_entropy() callback of the RAND_DRBG. It is roughly bounded by
       *
       *   2 * RAND_POOL_FACTOR * (RAND_DRBG_STRENGTH / 8) = 2^14
       *
       * which is way below the OSSL_SSIZE_MAX limit. Therefore sign conversion
       * between size_t and ssize_t is safe even without a range check.
       */
  
      /*
       * Do runtime detection to find getentropy().
       *
       * Known OSs that should support this:
       * - Darwin since 16 (OSX 10.12, IOS 10.0).
       * - Solaris since 11.3
       * - OpenBSD since 5.6
       * - Linux since 3.17 with glibc 2.25
       * - FreeBSD since 12.0 (1200061)
       */
  #  if defined(__GNUC__) && __GNUC__>=2 && defined(__ELF__)
      extern int getentropy(void *buffer, size_t length) __attribute__((weak));
  
      if (getentropy != NULL)
          return getentropy(buf, buflen) == 0 ? (ssize_t)buflen : -1;
  #  else
      union {
          void *p;
          int (*f)(void *buffer, size_t length);
      } p_getentropy;
  
      /*
       * We could cache the result of the lookup, but we normally don't
       * call this function often.
       */
      ERR_set_mark();
      p_getentropy.p = DSO_global_lookup("getentropy");
      ERR_pop_to_mark();
      if (p_getentropy.p != NULL)
          return p_getentropy.f(buf, buflen) == 0 ? (ssize_t)buflen : -1;
  #  endif
  
      /* Linux supports this since version 3.17 */
  #  if defined(__linux) && defined(__NR_getrandom)
      return syscall(__NR_getrandom, buf, buflen, 0);
  #  elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)
      return sysctl_random(buf, buflen);
  #  else
      errno = ENOSYS;
      return -1;
  #  endif
  }
  #  endif    /* defined(OPENSSL_RAND_SEED_GETRANDOM) */
  
  #  if defined(OPENSSL_RAND_SEED_DEVRANDOM)
  static const char *random_device_paths[] = { DEVRANDOM };
  static struct random_device {
      int fd;
      dev_t dev;
      ino_t ino;
      mode_t mode;
      dev_t rdev;
  } random_devices[OSSL_NELEM(random_device_paths)];
  static int keep_random_devices_open = 1;
  
  #   if defined(__linux) && defined(DEVRANDOM_WAIT) \
         && defined(OPENSSL_RAND_SEED_GETRANDOM)
  static void *shm_addr;
  
  static void cleanup_shm(void)
  {
      shmdt(shm_addr);
  }
  
  /*
   * Ensure that the system randomness source has been adequately seeded.
   * This is done by having the first start of libcrypto, wait until the device
   * /dev/random becomes able to supply a byte of entropy.  Subsequent starts
   * of the library and later reseedings do not need to do this.
   */
  static int wait_random_seeded(void)
  {
      static int seeded = OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID < 0;
      static const int kernel_version[] = { DEVRANDOM_SAFE_KERNEL };
      int kernel[2];
      int shm_id, fd, r;
      char c, *p;
      struct utsname un;
      fd_set fds;
  
      if (!seeded) {
          /* See if anything has created the global seeded indication */
          if ((shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1, 0)) == -1) {
              /*
               * Check the kernel's version and fail if it is too recent.
               *
               * Linux kernels from 4.8 onwards do not guarantee that
               * /dev/urandom is properly seeded when /dev/random becomes
               * readable.  However, such kernels support the getentropy(2)
               * system call and this should always succeed which renders
               * this alternative but essentially identical source moot.
               */
              if (uname(&un) == 0) {
                  kernel[0] = atoi(un.release);
                  p = strchr(un.release, '.');
                  kernel[1] = p == NULL ? 0 : atoi(p + 1);
                  if (kernel[0] > kernel_version[0]
                      || (kernel[0] == kernel_version[0]
                          && kernel[1] >= kernel_version[1])) {
                      return 0;
                  }
              }
              /* Open /dev/random and wait for it to be readable */
              if ((fd = open(DEVRANDOM_WAIT, O_RDONLY)) != -1) {
                  if (DEVRANDM_WAIT_USE_SELECT && fd < FD_SETSIZE) {
                      FD_ZERO(&fds);
                      FD_SET(fd, &fds);
                      while ((r = select(fd + 1, &fds, NULL, NULL, NULL)) < 0
                             && errno == EINTR);
                  } else {
                      while ((r = read(fd, &c, 1)) < 0 && errno == EINTR);
                  }
                  close(fd);
                  if (r == 1) {
                      seeded = 1;
                      /* Create the shared memory indicator */
                      shm_id = shmget(OPENSSL_RAND_SEED_DEVRANDOM_SHM_ID, 1,
                                      IPC_CREAT | S_IRUSR | S_IRGRP | S_IROTH);
                  }
              }
          }
          if (shm_id != -1) {
              seeded = 1;
              /*
               * Map the shared memory to prevent its premature destruction.
               * If this call fails, it isn't a big problem.
               */
              shm_addr = shmat(shm_id, NULL, SHM_RDONLY);
              if (shm_addr != (void *)-1)
                  OPENSSL_atexit(&cleanup_shm);
          }
      }
      return seeded;
  }
  #   else /* defined __linux && DEVRANDOM_WAIT && OPENSSL_RAND_SEED_GETRANDOM */
  static int wait_random_seeded(void)
  {
      return 1;
  }
  #   endif
  
  /*
   * Verify that the file descriptor associated with the random source is
   * still valid. The rationale for doing this is the fact that it is not
   * uncommon for daemons to close all open file handles when daemonizing.
   * So the handle might have been closed or even reused for opening
   * another file.
   */
  static int check_random_device(struct random_device * rd)
  {
      struct stat st;
  
      return rd->fd != -1
             && fstat(rd->fd, &st) != -1
             && rd->dev == st.st_dev
             && rd->ino == st.st_ino
             && ((rd->mode ^ st.st_mode) & ~(S_IRWXU | S_IRWXG | S_IRWXO)) == 0
             && rd->rdev == st.st_rdev;
  }
  
  /*
   * Open a random device if required and return its file descriptor or -1 on error
   */
  static int get_random_device(size_t n)
  {
      struct stat st;
      struct random_device * rd = &random_devices[n];
  
      /* reuse existing file descriptor if it is (still) valid */
      if (check_random_device(rd))
          return rd->fd;
  
      /* open the random device ... */
      if ((rd->fd = open(random_device_paths[n], O_RDONLY)) == -1)
          return rd->fd;
  
      /* ... and cache its relevant stat(2) data */
      if (fstat(rd->fd, &st) != -1) {
          rd->dev = st.st_dev;
          rd->ino = st.st_ino;
          rd->mode = st.st_mode;
          rd->rdev = st.st_rdev;
      } else {
          close(rd->fd);
          rd->fd = -1;
      }
  
      return rd->fd;
  }
  
  /*
   * Close a random device making sure it is a random device
   */
  static void close_random_device(size_t n)
  {
      struct random_device * rd = &random_devices[n];
  
      if (check_random_device(rd))
          close(rd->fd);
      rd->fd = -1;
  }
  
  int rand_pool_init(void)
  {
      size_t i;
  
      for (i = 0; i < OSSL_NELEM(random_devices); i++)
          random_devices[i].fd = -1;
  
      return 1;
  }
  
  void rand_pool_cleanup(void)
  {
      size_t i;
  
      for (i = 0; i < OSSL_NELEM(random_devices); i++)
          close_random_device(i);
  }
  
  void rand_pool_keep_random_devices_open(int keep)
  {
      if (!keep)
          rand_pool_cleanup();
  
      keep_random_devices_open = keep;
  }
  
  #  else     /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */
  
  int rand_pool_init(void)
  {
      return 1;
  }
  
  void rand_pool_cleanup(void)
  {
  }
  
  void rand_pool_keep_random_devices_open(int keep)
  {
  }
  
  #  endif    /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */
  
  /*
   * Try the various seeding methods in turn, exit when successful.
   *
   * TODO(DRBG): If more than one entropy source is available, is it
   * preferable to stop as soon as enough entropy has been collected
   * (as favored by @rsalz) or should one rather be defensive and add
   * more entropy than requested and/or from different sources?
   *
   * Currently, the user can select multiple entropy sources in the
   * configure step, yet in practice only the first available source
   * will be used. A more flexible solution has been requested, but
   * currently it is not clear how this can be achieved without
   * overengineering the problem. There are many parameters which
   * could be taken into account when selecting the order and amount
   * of input from the different entropy sources (trust, quality,
   * possibility of blocking).
   */
  size_t rand_pool_acquire_entropy(RAND_POOL *pool)
  {
  #  if defined(OPENSSL_RAND_SEED_NONE)
      return rand_pool_entropy_available(pool);
  #  else
      size_t entropy_available;
  
  #   if defined(OPENSSL_RAND_SEED_GETRANDOM)
      {
          size_t bytes_needed;
          unsigned char *buffer;
          ssize_t bytes;
          /* Maximum allowed number of consecutive unsuccessful attempts */
          int attempts = 3;
  
          bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
          while (bytes_needed != 0 && attempts-- > 0) {
              buffer = rand_pool_add_begin(pool, bytes_needed);
              bytes = syscall_random(buffer, bytes_needed);
              if (bytes > 0) {
                  rand_pool_add_end(pool, bytes, 8 * bytes);
                  bytes_needed -= bytes;
                  attempts = 3; /* reset counter after successful attempt */
              } else if (bytes < 0 && errno != EINTR) {
                  break;
              }
          }
      }
      entropy_available = rand_pool_entropy_available(pool);
      if (entropy_available > 0)
          return entropy_available;
  #   endif
  
  #   if defined(OPENSSL_RAND_SEED_LIBRANDOM)
      {
          /* Not yet implemented. */
      }
  #   endif
  
  #   if defined(OPENSSL_RAND_SEED_DEVRANDOM)
      if (wait_random_seeded()) {
          size_t bytes_needed;
          unsigned char *buffer;
          size_t i;
  
          bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
          for (i = 0; bytes_needed > 0 && i < OSSL_NELEM(random_device_paths);
               i++) {
              ssize_t bytes = 0;
              /* Maximum number of consecutive unsuccessful attempts */
              int attempts = 3;
              const int fd = get_random_device(i);
  
              if (fd == -1)
                  continue;
  
              while (bytes_needed != 0 && attempts-- > 0) {
                  buffer = rand_pool_add_begin(pool, bytes_needed);
                  bytes = read(fd, buffer, bytes_needed);
  
                  if (bytes > 0) {
                      rand_pool_add_end(pool, bytes, 8 * bytes);
                      bytes_needed -= bytes;
                      attempts = 3; /* reset counter on successful attempt */
                  } else if (bytes < 0 && errno != EINTR) {
                      break;
                  }
              }
              if (bytes < 0 || !keep_random_devices_open)
                  close_random_device(i);
  
              bytes_needed = rand_pool_bytes_needed(pool, 1);
          }
          entropy_available = rand_pool_entropy_available(pool);
          if (entropy_available > 0)
              return entropy_available;
      }
  #   endif
  
  #   if defined(OPENSSL_RAND_SEED_RDTSC)
      entropy_available = rand_acquire_entropy_from_tsc(pool);
      if (entropy_available > 0)
          return entropy_available;
  #   endif
  
  #   if defined(OPENSSL_RAND_SEED_RDCPU)
      entropy_available = rand_acquire_entropy_from_cpu(pool);
      if (entropy_available > 0)
          return entropy_available;
  #   endif
  
  #   if defined(OPENSSL_RAND_SEED_EGD)
      {
          static const char *paths[] = { DEVRANDOM_EGD, NULL };
          size_t bytes_needed;
          unsigned char *buffer;
          int i;
  
          bytes_needed = rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);
          for (i = 0; bytes_needed > 0 && paths[i] != NULL; i++) {
              size_t bytes = 0;
              int num;
  
              buffer = rand_pool_add_begin(pool, bytes_needed);
              num = RAND_query_egd_bytes(paths[i],
                                         buffer, (int)bytes_needed);
              if (num == (int)bytes_needed)
                  bytes = bytes_needed;
  
              rand_pool_add_end(pool, bytes, 8 * bytes);
              bytes_needed = rand_pool_bytes_needed(pool, 1);
          }
          entropy_available = rand_pool_entropy_available(pool);
          if (entropy_available > 0)
              return entropy_available;
      }
  #   endif
  
      return rand_pool_entropy_available(pool);
  #  endif
  }
  # endif
  #endif
  
  #if defined(OPENSSL_SYS_UNIX) || defined(__DJGPP__)
  int rand_pool_add_nonce_data(RAND_POOL *pool)
  {
      struct {
          pid_t pid;
          CRYPTO_THREAD_ID tid;
          uint64_t time;
      } data = { 0 };
  
      /*
       * Add process id, thread id, and a high resolution timestamp to
       * ensure that the nonce is unique with high probability for
       * different process instances.
       */
      data.pid = getpid();
      data.tid = CRYPTO_THREAD_get_current_id();
      data.time = get_time_stamp();
  
      return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
  }
  
  int rand_pool_add_additional_data(RAND_POOL *pool)
  {
      struct {
          int fork_id;
          CRYPTO_THREAD_ID tid;
          uint64_t time;
      } data = { 0 };
  
      /*
       * Add some noise from the thread id and a high resolution timer.
       * The fork_id adds some extra fork-safety.
       * The thread id adds a little randomness if the drbg is accessed
       * concurrently (which is the case for the <master> drbg).
       */
      data.fork_id = openssl_get_fork_id();
      data.tid = CRYPTO_THREAD_get_current_id();
      data.time = get_timer_bits();
  
      return rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0);
  }
  
  
  /*
   * Get the current time with the highest possible resolution
   *
   * The time stamp is added to the nonce, so it is optimized for not repeating.
   * The current time is ideal for this purpose, provided the computer's clock
   * is synchronized.
   */
  static uint64_t get_time_stamp(void)
  {
  # if defined(OSSL_POSIX_TIMER_OKAY)
      {
          struct timespec ts;
  
          if (clock_gettime(CLOCK_REALTIME, &ts) == 0)
              return TWO32TO64(ts.tv_sec, ts.tv_nsec);
      }
  # endif
  # if defined(__unix__) \
       || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
      {
          struct timeval tv;
  
          if (gettimeofday(&tv, NULL) == 0)
              return TWO32TO64(tv.tv_sec, tv.tv_usec);
      }
  # endif
      return time(NULL);
  }
  
  /*
   * Get an arbitrary timer value of the highest possible resolution
   *
   * The timer value is added as random noise to the additional data,
   * which is not considered a trusted entropy sourec, so any result
   * is acceptable.
   */
  static uint64_t get_timer_bits(void)
  {
      uint64_t res = OPENSSL_rdtsc();
  
      if (res != 0)
          return res;
  
  # if defined(__sun)
      return gethrtime();
  # elif defined(_AIX)
      {
          timebasestruct_t t;
  
          read_wall_time(&t, TIMEBASE_SZ);
          return TWO32TO64(t.tb_high, t.tb_low);
      }
  # elif defined(OSSL_POSIX_TIMER_OKAY)
      {
          struct timespec ts;
  
  #  ifdef CLOCK_BOOTTIME
  #   define CLOCK_TYPE CLOCK_BOOTTIME
  #  elif defined(_POSIX_MONOTONIC_CLOCK)
  #   define CLOCK_TYPE CLOCK_MONOTONIC
  #  else
  #   define CLOCK_TYPE CLOCK_REALTIME
  #  endif
  
          if (clock_gettime(CLOCK_TYPE, &ts) == 0)
              return TWO32TO64(ts.tv_sec, ts.tv_nsec);
      }
  # endif
  # if defined(__unix__) \
       || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
      {
          struct timeval tv;
  
          if (gettimeofday(&tv, NULL) == 0)
              return TWO32TO64(tv.tv_sec, tv.tv_usec);
      }
  # endif
      return time(NULL);
  }
  #endif /* (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS))
            || defined(__DJGPP__) */
  