openssl/test/drbgtest.c

/*
 * Copyright 2011-2024 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
 */

/* We need to use some deprecated APIs */
#define OPENSSL_SUPPRESS_DEPRECATED

#include <string.h>
#include "internal/nelem.h"
#include <openssl/crypto.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <openssl/obj_mac.h>
#include <openssl/evp.h>
#include <openssl/aes.h>
#include "../crypto/rand/rand_local.h"
#include "../include/crypto/rand.h"
#include "../include/crypto/evp.h"
#include "../providers/implementations/rands/drbg_local.h"
#include "../crypto/evp/evp_local.h"

#if defined(_WIN32)
# include <windows.h>
#endif

#if defined(OPENSSL_SYS_UNIX)
# include <sys/types.h>
# include <sys/wait.h>
# include <unistd.h>
#endif

#include "testutil.h"

/*
 * DRBG generate wrappers
 */
static int gen_bytes(EVP_RAND_CTX *drbg, unsigned char *buf, int num)
{
#ifndef OPENSSL_NO_DEPRECATED_3_0
    const RAND_METHOD *meth = RAND_get_rand_method();

    if (meth != NULL && meth != RAND_OpenSSL()) {
        if (meth->bytes != NULL)
            return meth->bytes(buf, num);
        return -1;
    }
#endif

    if (drbg != NULL)
        return EVP_RAND_generate(drbg, buf, num, 0, 0, NULL, 0);
    return 0;
}

static int rand_bytes(unsigned char *buf, int num)
{
    return gen_bytes(RAND_get0_public(NULL), buf, num);
}

static int rand_priv_bytes(unsigned char *buf, int num)
{
    return gen_bytes(RAND_get0_private(NULL), buf, num);
}


/* size of random output generated in test_drbg_reseed() */
#define RANDOM_SIZE 16

/*
 * DRBG query functions
 */
static int state(EVP_RAND_CTX *drbg)
{
    return EVP_RAND_get_state(drbg);
}

static unsigned int query_rand_uint(EVP_RAND_CTX *drbg, const char *name)
{
    OSSL_PARAM params[2] = { OSSL_PARAM_END, OSSL_PARAM_END };
    unsigned int n;

    *params = OSSL_PARAM_construct_uint(name, &n);
    if (EVP_RAND_CTX_get_params(drbg, params))
        return n;
    return 0;
}

#define DRBG_UINT(name)                                 \
    static unsigned int name(EVP_RAND_CTX *drbg)        \
    {                                                   \
        return query_rand_uint(drbg, #name);            \
    }
DRBG_UINT(reseed_counter)

static PROV_DRBG *prov_rand(EVP_RAND_CTX *drbg)
{
    return (PROV_DRBG *)drbg->algctx;
}

static void set_reseed_counter(EVP_RAND_CTX *drbg, unsigned int n)
{
    PROV_DRBG *p = prov_rand(drbg);

    p->reseed_counter = n;
}

static void inc_reseed_counter(EVP_RAND_CTX *drbg)
{
    set_reseed_counter(drbg, reseed_counter(drbg) + 1);
}

static time_t reseed_time(EVP_RAND_CTX *drbg)
{
    OSSL_PARAM params[2] = { OSSL_PARAM_END, OSSL_PARAM_END };
    time_t t;

    *params = OSSL_PARAM_construct_time_t(OSSL_DRBG_PARAM_RESEED_TIME, &t);
    if (EVP_RAND_CTX_get_params(drbg, params))
        return t;
    return 0;
}

/*
 * When building the FIPS module, it isn't possible to disable the continuous
 * RNG tests.  Tests that require this are skipped and this means a detection
 * mechanism for the FIPS provider being in use.
 */
static int using_fips_rng(void)
{
    EVP_RAND_CTX *primary = RAND_get0_primary(NULL);
    const OSSL_PROVIDER *prov;
    const char *name;

    if (!TEST_ptr(primary))
        return 0;

    prov = EVP_RAND_get0_provider(EVP_RAND_CTX_get0_rand(primary));
    if (!TEST_ptr(prov))
        return 0;
    name = OSSL_PROVIDER_get0_name(prov);
    return strstr(name, "FIPS Provider") != NULL;
}

 /*
 * Disable CRNG testing if it is enabled.
 * This stub remains to indicate the calling locations where it is necessary.
 * Once the RNG infrastructure is able to disable these tests, it should be
 * reconstituted.
 */
static int disable_crngt(EVP_RAND_CTX *drbg)
{
    return 1;
}

/*
 * Generates random output using rand_bytes() and rand_priv_bytes()
 * and checks whether the three shared DRBGs were reseeded as
 * expected.
 *
 * |expect_success|: expected outcome (as reported by RAND_status())
 * |primary|, |public|, |private|: pointers to the three shared DRBGs
 * |public_random|, |private_random|: generated random output
 * |expect_xxx_reseed| =
 *       1:  it is expected that the specified DRBG is reseeded
 *       0:  it is expected that the specified DRBG is not reseeded
 *      -1:  don't check whether the specified DRBG was reseeded or not
 * |reseed_when|: if nonzero, used instead of time(NULL) to set the
 *                |before_reseed| time.
 */
static int test_drbg_reseed(int expect_success,
                            EVP_RAND_CTX *primary,
                            EVP_RAND_CTX *public,
                            EVP_RAND_CTX *private,
                            unsigned char *public_random,
                            unsigned char *private_random,
                            int expect_primary_reseed,
                            int expect_public_reseed,
                            int expect_private_reseed,
                            time_t reseed_when
                           )
{
    time_t before_reseed, after_reseed;
    int expected_state = (expect_success ? DRBG_READY : DRBG_ERROR);
    unsigned int primary_reseed, public_reseed, private_reseed;
    unsigned char dummy[RANDOM_SIZE];

    if (public_random == NULL)
        public_random = dummy;

    if (private_random == NULL)
        private_random = dummy;

    /*
     * step 1: check preconditions
     */

    /* Test whether seed propagation is enabled */
    if (!TEST_int_ne(primary_reseed = reseed_counter(primary), 0)
        || !TEST_int_ne(public_reseed = reseed_counter(public), 0)
        || !TEST_int_ne(private_reseed = reseed_counter(private), 0))
        return 0;

    /*
     * step 2: generate random output
     */

    if (reseed_when == 0)
        reseed_when = time(NULL);

    /* Generate random output from the public and private DRBG */
    before_reseed = expect_primary_reseed == 1 ? reseed_when : 0;
    if (!TEST_int_eq(rand_bytes((unsigned char*)public_random,
                                RANDOM_SIZE), expect_success)
        || !TEST_int_eq(rand_priv_bytes((unsigned char*) private_random,
                                        RANDOM_SIZE), expect_success))
        return 0;
    after_reseed = time(NULL);


    /*
     * step 3: check postconditions
     */

    /* Test whether reseeding succeeded as expected */
    if (!TEST_int_eq(state(primary), expected_state)
        || !TEST_int_eq(state(public), expected_state)
        || !TEST_int_eq(state(private), expected_state))
        return 0;

    if (expect_primary_reseed >= 0) {
        /* Test whether primary DRBG was reseeded as expected */
        if (!TEST_int_ge(reseed_counter(primary), primary_reseed))
            return 0;
    }

    if (expect_public_reseed >= 0) {
        /* Test whether public DRBG was reseeded as expected */
        if (!TEST_int_ge(reseed_counter(public), public_reseed)
                || !TEST_uint_ge(reseed_counter(public),
                                 reseed_counter(primary)))
            return 0;
    }

    if (expect_private_reseed >= 0) {
        /* Test whether public DRBG was reseeded as expected */
        if (!TEST_int_ge(reseed_counter(private), private_reseed)
                || !TEST_uint_ge(reseed_counter(private),
                                 reseed_counter(primary)))
            return 0;
    }

    if (expect_success == 1) {
        /* Test whether reseed time of primary DRBG is set correctly */
        if (!TEST_time_t_le(before_reseed, reseed_time(primary))
            || !TEST_time_t_le(reseed_time(primary), after_reseed))
            return 0;

        /* Test whether reseed times of child DRBGs are synchronized with primary */
        if (!TEST_time_t_ge(reseed_time(public), reseed_time(primary))
            || !TEST_time_t_ge(reseed_time(private), reseed_time(primary)))
            return 0;
    } else {
        ERR_clear_error();
    }

    return 1;
}


#if defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_RAND_SEED_EGD)
/* number of children to fork */
#define DRBG_FORK_COUNT 9
/* two results per child, two for the parent */
#define DRBG_FORK_RESULT_COUNT (2 * (DRBG_FORK_COUNT + 1))

typedef struct drbg_fork_result_st {

    unsigned char random[RANDOM_SIZE]; /* random output */

    int pindex;               /* process index (0: parent, 1,2,3...: children)*/
    pid_t pid;                /* process id */
    int private;              /* true if the private drbg was used */
    char name[10];            /* 'parent' resp. 'child 1', 'child 2', ... */
} drbg_fork_result;

/*
 * Sort the drbg_fork_result entries in lexicographical order
 *
 * This simplifies finding duplicate random output and makes
 * the printout in case of an error more readable.
 */
static int compare_drbg_fork_result(const void *left, const void *right)
{
    int result;
    const drbg_fork_result *l = left;
    const drbg_fork_result *r = right;

    /* separate public and private results */
    result = l->private - r->private;

    if (result == 0)
        result = memcmp(l->random, r->random, RANDOM_SIZE);

    if (result == 0)
        result = l->pindex - r->pindex;

    return result;
}

/*
 * Sort two-byte chunks of random data
 *
 * Used for finding collisions in two-byte chunks
 */
static int compare_rand_chunk(const void *left, const void *right)
{
    return memcmp(left, right, 2);
}

/*
 * Test whether primary, public and private DRBG are reseeded
 * in the child after forking the process. Collect the random
 * output of the public and private DRBG and send it back to
 * the parent process.
 */
static int test_drbg_reseed_in_child(EVP_RAND_CTX *primary,
                                     EVP_RAND_CTX *public,
                                     EVP_RAND_CTX *private,
                                     drbg_fork_result result[2])
{
    int rv = 0, status;
    int fd[2];
    pid_t pid;
    unsigned char random[2 * RANDOM_SIZE];

    if (!TEST_int_ge(pipe(fd), 0))
        return 0;

    if (!TEST_int_ge(pid = fork(), 0)) {
        close(fd[0]);
        close(fd[1]);
        return 0;
    } else if (pid > 0) {

        /* I'm the parent; close the write end */
        close(fd[1]);

        /* wait for children to terminate and collect their random output */
        if (TEST_int_eq(waitpid(pid, &status, 0), pid)
            && TEST_int_eq(status, 0)
            && TEST_true(read(fd[0], &random[0], sizeof(random))
                          == sizeof(random))) {

            /* random output of public drbg */
            result[0].pid = pid;
            result[0].private = 0;
            memcpy(result[0].random, &random[0], RANDOM_SIZE);

            /* random output of private drbg */
            result[1].pid = pid;
            result[1].private = 1;
            memcpy(result[1].random, &random[RANDOM_SIZE], RANDOM_SIZE);

            rv = 1;
        }

        /* close the read end */
        close(fd[0]);

        return rv;

    } else {

        /* I'm the child; close the read end */
        close(fd[0]);

        /* check whether all three DRBGs reseed and send output to parent */
        if (TEST_true(test_drbg_reseed(1, primary, public, private,
                                        &random[0], &random[RANDOM_SIZE],
                                       1, 1, 1, 0))
            && TEST_true(write(fd[1], random, sizeof(random))
                         == sizeof(random))) {

            rv = 1;
        }

        /* close the write end */
        close(fd[1]);

        /* convert boolean to exit code */
        exit(rv == 0);
    }
}

static int test_rand_reseed_on_fork(EVP_RAND_CTX *primary,
                                    EVP_RAND_CTX *public,
                                    EVP_RAND_CTX *private)
{
    unsigned int i;
    pid_t pid = getpid();
    int verbose = (getenv("V") != NULL);
    int success = 1;
    int duplicate[2] = {0, 0};
    unsigned char random[2 * RANDOM_SIZE];
    unsigned char sample[DRBG_FORK_RESULT_COUNT * RANDOM_SIZE];
    unsigned char *psample = &sample[0];
    drbg_fork_result result[DRBG_FORK_RESULT_COUNT];
    drbg_fork_result *presult = &result[2];

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

    for (i = 1 ; i <= DRBG_FORK_COUNT ; ++i) {

        presult[0].pindex = presult[1].pindex = i;

        BIO_snprintf(presult[0].name, sizeof(presult[0].name), "child %d", i);
        strcpy(presult[1].name, presult[0].name);

        /* collect the random output of the children */
        if (!TEST_true(test_drbg_reseed_in_child(primary,
                                                 public,
                                                 private,
                                                 presult)))
            return 0;

        presult += 2;
    }

    /* collect the random output of the parent */
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    &random[0], &random[RANDOM_SIZE],
                                    0, 0, 0, 0)))
        return 0;

    strcpy(result[0].name, "parent");
    strcpy(result[1].name, "parent");

    /* output of public drbg */
    result[0].pid = pid;
    result[0].private = 0;
    memcpy(result[0].random, &random[0], RANDOM_SIZE);

    /* output of private drbg */
    result[1].pid = pid;
    result[1].private = 1;
    memcpy(result[1].random, &random[RANDOM_SIZE], RANDOM_SIZE);

    /* collect all sampled random data in a single buffer */
    for (i = 0 ; i < DRBG_FORK_RESULT_COUNT ; ++i) {
        memcpy(psample, &result[i].random[0], RANDOM_SIZE);
        psample += RANDOM_SIZE;
    }

    /* sort the results... */
    qsort(result, DRBG_FORK_RESULT_COUNT, sizeof(drbg_fork_result),
          compare_drbg_fork_result);

    /* ...and count duplicate prefixes by looking at the first byte only */
    for (i = 1 ; i < DRBG_FORK_RESULT_COUNT ; ++i) {
        if (result[i].random[0] == result[i-1].random[0]) {
            /* count public and private duplicates separately */
            ++duplicate[result[i].private];
        }
    }

    if (duplicate[0] >= DRBG_FORK_COUNT - 1) {
        /* just too many duplicates to be a coincidence */
        TEST_note("ERROR: %d duplicate prefixes in public random output", duplicate[0]);
        success = 0;
    }

    if (duplicate[1] >= DRBG_FORK_COUNT - 1) {
        /* just too many duplicates to be a coincidence */
        TEST_note("ERROR: %d duplicate prefixes in private random output", duplicate[1]);
        success = 0;
    }

    duplicate[0] = 0;

    /* sort the two-byte chunks... */
    qsort(sample, sizeof(sample)/2, 2, compare_rand_chunk);

    /* ...and count duplicate chunks */
    for (i = 2, psample = sample + 2 ; i < sizeof(sample) ; i += 2, psample += 2) {
        if (compare_rand_chunk(psample - 2, psample) == 0)
            ++duplicate[0];
    }

    if (duplicate[0] >= DRBG_FORK_COUNT - 1) {
        /* just too many duplicates to be a coincidence */
        TEST_note("ERROR: %d duplicate chunks in random output", duplicate[0]);
        success = 0;
    }

    if (verbose || !success) {

        for (i = 0 ; i < DRBG_FORK_RESULT_COUNT ; ++i) {
            char *rand_hex = OPENSSL_buf2hexstr(result[i].random, RANDOM_SIZE);

            TEST_note("    random: %s, pid: %d (%s, %s)",
                      rand_hex,
                      result[i].pid,
                      result[i].name,
                      result[i].private ? "private" : "public"
                      );

            OPENSSL_free(rand_hex);
        }
    }

    return success;
}

static int test_rand_fork_safety(int i)
{
    int success = 1;
    unsigned char random[1];
    EVP_RAND_CTX *primary, *public, *private;

    /* All three DRBGs should be non-null */
    if (!TEST_ptr(primary = RAND_get0_primary(NULL))
        || !TEST_ptr(public = RAND_get0_public(NULL))
        || !TEST_ptr(private = RAND_get0_private(NULL)))
        return 0;

    /* run the actual test */
    if (!TEST_true(test_rand_reseed_on_fork(primary, public, private)))
        success = 0;

    /* request a single byte from each of the DRBGs before the next run */
    if (!TEST_int_gt(RAND_bytes(random, 1), 0) || !TEST_int_gt(RAND_priv_bytes(random, 1), 0))
        success = 0;

    return success;
}
#endif

/*
 * Test whether the default rand_method (RAND_OpenSSL()) is
 * setup correctly, in particular whether reseeding works
 * as designed.
 */
static int test_rand_reseed(void)
{
    EVP_RAND_CTX *primary, *public, *private;
    unsigned char rand_add_buf[256];
    int rv = 0;
    time_t before_reseed;

    if (using_fips_rng())
        return TEST_skip("CRNGT cannot be disabled");

#ifndef OPENSSL_NO_DEPRECATED_3_0
    /* Check whether RAND_OpenSSL() is the default method */
    if (!TEST_ptr_eq(RAND_get_rand_method(), RAND_OpenSSL()))
        return 0;
#endif

    /* All three DRBGs should be non-null */
    if (!TEST_ptr(primary = RAND_get0_primary(NULL))
        || !TEST_ptr(public = RAND_get0_public(NULL))
        || !TEST_ptr(private = RAND_get0_private(NULL)))
        return 0;

    /* There should be three distinct DRBGs, two of them chained to primary */
    if (!TEST_ptr_ne(public, private)
        || !TEST_ptr_ne(public, primary)
        || !TEST_ptr_ne(private, primary)
        || !TEST_ptr_eq(prov_rand(public)->parent, prov_rand(primary))
        || !TEST_ptr_eq(prov_rand(private)->parent, prov_rand(primary)))
        return 0;

    /* Disable CRNG testing for the primary DRBG */
    if (!TEST_true(disable_crngt(primary)))
        return 0;

    /* uninstantiate the three global DRBGs */
    EVP_RAND_uninstantiate(primary);
    EVP_RAND_uninstantiate(private);
    EVP_RAND_uninstantiate(public);

    /*
     * Test initial seeding of shared DRBGs
     */
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    1, 1, 1, 0)))
        goto error;

    /*
     * Test initial state of shared DRBGs
     */
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    0, 0, 0, 0)))
        goto error;

    /*
     * Test whether the public and private DRBG are both reseeded when their
     * reseed counters differ from the primary's reseed counter.
     */
    inc_reseed_counter(primary);
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    0, 1, 1, 0)))
        goto error;

    /*
     * Test whether the public DRBG is reseeded when its reseed counter differs
     * from the primary's reseed counter.
     */
    inc_reseed_counter(primary);
    inc_reseed_counter(private);
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    0, 1, 0, 0)))
        goto error;

    /*
     * Test whether the private DRBG is reseeded when its reseed counter differs
     * from the primary's reseed counter.
     */
    inc_reseed_counter(primary);
    inc_reseed_counter(public);
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    0, 0, 1, 0)))
        goto error;

    /* fill 'randomness' buffer with some arbitrary data */
    memset(rand_add_buf, 'r', sizeof(rand_add_buf));

    /*
     * Test whether all three DRBGs are reseeded by RAND_add().
     * The before_reseed time has to be measured here and passed into the
     * test_drbg_reseed() test, because the primary DRBG gets already reseeded
     * in RAND_add(), whence the check for the condition
     * before_reseed <= reseed_time(primary) will fail if the time value happens
     * to increase between the RAND_add() and the test_drbg_reseed() call.
     */
    before_reseed = time(NULL);
    RAND_add(rand_add_buf, sizeof(rand_add_buf), sizeof(rand_add_buf));
    if (!TEST_true(test_drbg_reseed(1,
                                    primary, public, private,
                                    NULL, NULL,
                                    1, 1, 1,
                                    before_reseed)))
        goto error;

    rv = 1;

error:
   return rv;
}

#if defined(OPENSSL_THREADS)
static int multi_thread_rand_bytes_succeeded = 1;
static int multi_thread_rand_priv_bytes_succeeded = 1;

static int set_reseed_time_interval(EVP_RAND_CTX *drbg, int t)
{
    OSSL_PARAM params[2];

    params[0] = OSSL_PARAM_construct_int(OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL,
                                         &t);
    params[1] = OSSL_PARAM_construct_end();
    return EVP_RAND_CTX_set_params(drbg, params);
}

static void run_multi_thread_test(void)
{
    unsigned char buf[256];
    time_t start = time(NULL);
    EVP_RAND_CTX *public = NULL, *private = NULL;

    if (!TEST_ptr(public = RAND_get0_public(NULL))
            || !TEST_ptr(private = RAND_get0_private(NULL))
            || !TEST_true(set_reseed_time_interval(private, 1))
            || !TEST_true(set_reseed_time_interval(public, 1))) {
        multi_thread_rand_bytes_succeeded = 0;
        return;
    }

    do {
        if (rand_bytes(buf, sizeof(buf)) <= 0)
            multi_thread_rand_bytes_succeeded = 0;
        if (rand_priv_bytes(buf, sizeof(buf)) <= 0)
            multi_thread_rand_priv_bytes_succeeded = 0;
    }
    while (time(NULL) - start < 5);
}

# if defined(OPENSSL_SYS_WINDOWS)

typedef HANDLE thread_t;

static DWORD WINAPI thread_run(LPVOID arg)
{
    run_multi_thread_test();
    /*
     * Because we're linking with a static library, we must stop each
     * thread explicitly, or so says OPENSSL_thread_stop(3)
     */
    OPENSSL_thread_stop();
    return 0;
}

static int run_thread(thread_t *t)
{
    *t = CreateThread(NULL, 0, thread_run, NULL, 0, NULL);
    return *t != NULL;
}

static int wait_for_thread(thread_t thread)
{
    return WaitForSingleObject(thread, INFINITE) == 0;
}

# else

typedef pthread_t thread_t;

static void *thread_run(void *arg)
{
    run_multi_thread_test();
    /*
     * Because we're linking with a static library, we must stop each
     * thread explicitly, or so says OPENSSL_thread_stop(3)
     */
    OPENSSL_thread_stop();
    return NULL;
}

static int run_thread(thread_t *t)
{
    return pthread_create(t, NULL, thread_run, NULL) == 0;
}

static int wait_for_thread(thread_t thread)
{
    return pthread_join(thread, NULL) == 0;
}

# endif

/*
 * The main thread will also run the test, so we'll have THREADS+1 parallel
 * tests running
 */
# define THREADS 3

static int test_multi_thread(void)
{
    thread_t t[THREADS];
    int i;

    for (i = 0; i < THREADS; i++)
        run_thread(&t[i]);
    run_multi_thread_test();
    for (i = 0; i < THREADS; i++)
        wait_for_thread(t[i]);

    if (!TEST_true(multi_thread_rand_bytes_succeeded))
        return 0;
    if (!TEST_true(multi_thread_rand_priv_bytes_succeeded))
        return 0;

    return 1;
}
#endif

static EVP_RAND_CTX *new_drbg(EVP_RAND_CTX *parent)
{
    OSSL_PARAM params[2];
    EVP_RAND *rand = NULL;
    EVP_RAND_CTX *drbg = NULL;

    params[0] = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
                                                 "AES-256-CTR", 0);
    params[1] = OSSL_PARAM_construct_end();

    if (!TEST_ptr(rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL))
            || !TEST_ptr(drbg = EVP_RAND_CTX_new(rand, parent))
            || !TEST_true(EVP_RAND_CTX_set_params(drbg, params))) {
        EVP_RAND_CTX_free(drbg);
        drbg = NULL;
    }
    EVP_RAND_free(rand);
    return drbg;
}

static int test_rand_prediction_resistance(void)
{
    EVP_RAND_CTX *x = NULL, *y = NULL, *z = NULL;
    unsigned char buf1[51], buf2[sizeof(buf1)];
    int ret = 0, xreseed, yreseed, zreseed;

    if (using_fips_rng())
        return TEST_skip("CRNGT cannot be disabled");

    /* Initialise a three long DRBG chain */
    if (!TEST_ptr(x = new_drbg(NULL))
        || !TEST_true(disable_crngt(x))
        || !TEST_true(EVP_RAND_instantiate(x, 0, 0, NULL, 0, NULL))
        || !TEST_ptr(y = new_drbg(x))
        || !TEST_true(EVP_RAND_instantiate(y, 0, 0, NULL, 0, NULL))
        || !TEST_ptr(z = new_drbg(y))
        || !TEST_true(EVP_RAND_instantiate(z, 0, 0, NULL, 0, NULL)))
        goto err;

    /*
     * During a normal reseed, only the last DRBG in the chain should
     * be reseeded.
     */
    inc_reseed_counter(y);
    xreseed = reseed_counter(x);
    yreseed = reseed_counter(y);
    zreseed = reseed_counter(z);
    if (!TEST_true(EVP_RAND_reseed(z, 0, NULL, 0, NULL, 0))
        || !TEST_int_eq(reseed_counter(x), xreseed)
        || !TEST_int_eq(reseed_counter(y), yreseed)
        || !TEST_int_gt(reseed_counter(z), zreseed))
        goto err;

    /*
     * When prediction resistance is requested, the request should be
     * propagated to the primary, so that the entire DRBG chain reseeds.
     */
    zreseed = reseed_counter(z);
    if (!TEST_true(EVP_RAND_reseed(z, 1, NULL, 0, NULL, 0))
        || !TEST_int_gt(reseed_counter(x), xreseed)
        || !TEST_int_gt(reseed_counter(y), yreseed)
        || !TEST_int_gt(reseed_counter(z), zreseed))
        goto err;

    /*
     * During a normal generate, only the last DRBG should be reseed */
    inc_reseed_counter(y);
    xreseed = reseed_counter(x);
    yreseed = reseed_counter(y);
    zreseed = reseed_counter(z);
    if (!TEST_true(EVP_RAND_generate(z, buf1, sizeof(buf1), 0, 0, NULL, 0))
        || !TEST_int_eq(reseed_counter(x), xreseed)
        || !TEST_int_eq(reseed_counter(y), yreseed)
        || !TEST_int_gt(reseed_counter(z), zreseed))
        goto err;

    /*
     * When a prediction resistant generate is requested, the request
     * should be propagated to the primary, reseeding the entire DRBG chain.
     */
    zreseed = reseed_counter(z);
    if (!TEST_true(EVP_RAND_generate(z, buf2, sizeof(buf2), 0, 1, NULL, 0))
        || !TEST_int_gt(reseed_counter(x), xreseed)
        || !TEST_int_gt(reseed_counter(y), yreseed)
        || !TEST_int_gt(reseed_counter(z), zreseed)
        || !TEST_mem_ne(buf1, sizeof(buf1), buf2, sizeof(buf2)))
        goto err;

    /* Verify that a normal reseed still only reseeds the last DRBG */
    inc_reseed_counter(y);
    xreseed = reseed_counter(x);
    yreseed = reseed_counter(y);
    zreseed = reseed_counter(z);
    if (!TEST_true(EVP_RAND_reseed(z, 0, NULL, 0, NULL, 0))
        || !TEST_int_eq(reseed_counter(x), xreseed)
        || !TEST_int_eq(reseed_counter(y), yreseed)
        || !TEST_int_gt(reseed_counter(z), zreseed))
        goto err;

    ret = 1;
err:
    EVP_RAND_CTX_free(z);
    EVP_RAND_CTX_free(y);
    EVP_RAND_CTX_free(x);
    return ret;
}

int setup_tests(void)
{
    ADD_TEST(test_rand_reseed);
#if defined(OPENSSL_SYS_UNIX) && !defined(OPENSSL_RAND_SEED_EGD)
    ADD_ALL_TESTS(test_rand_fork_safety, RANDOM_SIZE);
#endif
    ADD_TEST(test_rand_prediction_resistance);
#if defined(OPENSSL_THREADS)
    ADD_TEST(test_multi_thread);
#endif
    return 1;
}