/*

 * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (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 "internal/e_os.h"

#include <stdio.h>

#include "internal/cryptlib.h"

#include <openssl/rand.h>

#include <openssl/crypto.h>

#include "crypto/rand_pool.h"

#include "crypto/rand.h"

#include "internal/dso.h"

#include "internal/nelem.h"

#include "prov/seeding.h"

#ifndef OPENSSL_SYS_UEFI

#ifdef __linux

#include <sys/syscall.h>

#ifdef DEVRANDOM_WAIT

#include <sys/shm.h>

#include <sys/utsname.h>

#endif

#endif

#if defined(__FreeBSD__) || defined(__NetBSD__)

#include <sys/types.h>

#include <sys/sysctl.h>

#include <sys/param.h>

#endif

#if defined(__FreeBSD__) && __FreeBSD_version >= 1200061

#include <sys/random.h>

#endif

#if defined(__OpenBSD__)

#include <sys/param.h>

#endif

#if defined(__DragonFly__)

#include <sys/param.h>

#include <sys/random.h>

#endif

#endif

#if (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS)) \

    || 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);

/* 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

/* On some systems, _POSIX_TIMERS is defined but empty.

 * Subtracting by 0 when comparing avoids an error in this case. */

#if defined(_POSIX_TIMERS) && _POSIX_TIMERS - 0 > 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_DEVRANDOM

#undef OPENSSL_RAND_SEED_RDTSC

#undef OPENSSL_RAND_SEED_RDCPU

#undef OPENSSL_RAND_SEED_EGD

#endif

#if defined(OPENSSL_SYS_UEFI) && !defined(OPENSSL_RAND_SEED_NONE)

#error "UEFI only supports seeding NONE"

#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 ossl_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 = ossl_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);

        ossl_rand_pool_add(pool, arg, &v, sizeof(v), 2);

    }

    return ossl_rand_pool_entropy_available(pool);

}

void ossl_rand_pool_cleanup(void)

{

}

void ossl_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(__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 defined(__FreeBSD__)

    if (!ossl_assert(buflen % sizeof(long) == 0)) {

        errno = EINVAL;

        return -1;

    }

#endif

    /*

     * 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 > 256 ? 256 : 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

#else /* generic (f.e. aarch64, loongarch, loongarch64) */

#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

     *

     * Note: Sometimes getentropy() can be provided but not implemented

     * internally. So we need to check errno for ENOSYS

     */

#if !defined(__DragonFly__) && !defined(__NetBSD__) && !defined(__FreeBSD__)

#if defined(__GNUC__) && __GNUC__ >= 2 && defined(__ELF__) && !defined(__hpux)

    extern int getentropy(void *buffer, size_t length) __attribute__((weak));

    if (getentropy != NULL) {

        if (getentropy(buf, buflen) == 0)

            return (ssize_t)buflen;

        if (errno != ENOSYS)

            return -1;

    }

#elif defined(OPENSSL_APPLE_CRYPTO_RANDOM)

    if (CCRandomGenerateBytes(buf, buflen) == kCCSuccess)

        return (ssize_t)buflen;

    return -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

#endif /* !__DragonFly__ && !__NetBSD__ && !__FreeBSD__ */

    /* Linux supports this since version 3.17 */

#if defined(__linux) && defined(__NR_getrandom)

    return syscall(__NR_getrandom, buf, buflen, 0);

#elif (defined(__DragonFly__) && __DragonFly_version >= 500700) \

    || (defined(__NetBSD__) && __NetBSD_Version >= 1000000000)  \

    || (defined(__FreeBSD__) && __FreeBSD_version >= 1200061)

    return getrandom(buf, buflen, 0);

#elif (defined(__FreeBSD__) || defined(__NetBSD__)) && defined(KERN_ARND)

    return sysctl_random(buf, buflen);

#elif defined(__wasi__)

    if (getentropy(buf, buflen) == 0)

        return (ssize_t)buflen;

    return -1;

#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 ossl_rand_pool_init(void)

{

    size_t i;

    for (i = 0; i < OSSL_NELEM(random_devices); i++)

        random_devices[i].fd = -1;

    return 1;

}

void ossl_rand_pool_cleanup(void)

{

    size_t i;

    for (i = 0; i < OSSL_NELEM(random_devices); i++)

        close_random_device(i);

}

void ossl_rand_pool_keep_random_devices_open(int keep)

{

    if (!keep)

        ossl_rand_pool_cleanup();

    keep_random_devices_open = keep;

}

#else /* !defined(OPENSSL_RAND_SEED_DEVRANDOM) */

int ossl_rand_pool_init(void)

{

    return 1;

}

void ossl_rand_pool_cleanup(void)

{

}

void ossl_rand_pool_keep_random_devices_open(int keep)

{

}

#endif /* defined(OPENSSL_RAND_SEED_DEVRANDOM) */

/*

 * Try the various seeding methods in turn, exit when successful.

 *

 * 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 ossl_pool_acquire_entropy(RAND_POOL *pool)

{

#if defined(OPENSSL_RAND_SEED_NONE)

    return ossl_rand_pool_entropy_available(pool);

#else

    size_t entropy_available = 0;

    (void)entropy_available; /* avoid compiler warning */

#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 = ossl_rand_pool_bytes_needed(pool, 1 /*entropy_factor*/);

        while (bytes_needed != 0 && attempts-- > 0) {

            buffer = ossl_rand_pool_add_begin(pool, bytes_needed);

            bytes = syscall_random(buffer, bytes_needed);

            if (bytes > 0) {

                ossl_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 = ossl_rand_pool_entropy_available(pool);

    if (entropy_available > 0)

        return entropy_available;

#endif

#if defined(OPENSSL_RAND_SEED_DEVRANDOM)

    if (wait_random_seeded()) {

        size_t bytes_needed;

        unsigned char *buffer;

        size_t i;

        bytes_needed = ossl_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 = ossl_rand_pool_add_begin(pool, bytes_needed);

                bytes = read(fd, buffer, bytes_needed);

                if (bytes > 0) {

                    ossl_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 = ossl_rand_pool_bytes_needed(pool, 1);

        }

        entropy_available = ossl_rand_pool_entropy_available(pool);

        if (entropy_available > 0)

            return entropy_available;

    }

#endif

#if defined(OPENSSL_RAND_SEED_RDTSC)

    entropy_available = ossl_prov_acquire_entropy_from_tsc(pool);

    if (entropy_available > 0)

        return entropy_available;

#endif

#if defined(OPENSSL_RAND_SEED_RDCPU)

    entropy_available = ossl_prov_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 = ossl_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 = ossl_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;

            ossl_rand_pool_add_end(pool, bytes, 8 * bytes);

            bytes_needed = ossl_rand_pool_bytes_needed(pool, 1);

        }

        entropy_available = ossl_rand_pool_entropy_available(pool);

        if (entropy_available > 0)

            return entropy_available;

    }

#endif

    return ossl_rand_pool_entropy_available(pool);

#endif

}

#endif

#endif

#if (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS)) \

    || defined(__DJGPP__)

int ossl_pool_add_nonce_data(RAND_POOL *pool)

{

    struct {

        pid_t pid;

        CRYPTO_THREAD_ID tid;

        uint64_t time;

    } data;

    /* Erase the entire structure including any padding */

    memset(&data, 0, sizeof(data));

    /*

     * 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 ossl_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);

}

#endif /* (defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_SYS_VXWORKS)) \

          || defined(__DJGPP__) */