wolfssl/wolfcrypt/src/random.c

/* random.c
 *
 * Copyright (C) 2006-2017 wolfSSL Inc.
 *
 * This file is part of wolfSSL.
 *
 * wolfSSL is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * wolfSSL is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
 */


#ifdef HAVE_CONFIG_H
    #include <config.h>
#endif

#include <wolfssl/wolfcrypt/settings.h>
#include <wolfssl/wolfcrypt/error-crypt.h>

/* on HPUX 11 you may need to install /dev/random see
   http://h20293.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=KRNG11I

*/

#if defined(HAVE_FIPS) && \
	defined(HAVE_FIPS_VERSION) && (HAVE_FIPS_VERSION >= 2)

    /* set NO_WRAPPERS before headers, use direct internal f()s not wrappers */
    #define FIPS_NO_WRAPPERS

    #ifdef USE_WINDOWS_API
        #pragma code_seg(".fipsA$c")
        #pragma const_seg(".fipsB$c")
    #endif
#endif


#include <wolfssl/wolfcrypt/random.h>
#include <wolfssl/wolfcrypt/cpuid.h>


/* If building for old FIPS. */
#if defined(HAVE_FIPS) && \
    (!defined(HAVE_FIPS_VERSION) || (HAVE_FIPS_VERSION < 2))

int wc_GenerateSeed(OS_Seed* os, byte* seed, word32 sz)
{
    return GenerateSeed(os, seed, sz);
}

int wc_InitRng_ex(WC_RNG* rng, void* heap, int devId)
{
    (void)heap;
    (void)devId;
    return InitRng_fips(rng);
}

int wc_InitRng(WC_RNG* rng)
{
    return InitRng_fips(rng);
}


int wc_RNG_GenerateBlock(WC_RNG* rng, byte* b, word32 sz)
{
    return RNG_GenerateBlock_fips(rng, b, sz);
}


int wc_RNG_GenerateByte(WC_RNG* rng, byte* b)
{
    return RNG_GenerateByte(rng, b);
}

#ifdef HAVE_HASHDRBG

    int wc_FreeRng(WC_RNG* rng)
    {
        return FreeRng_fips(rng);
    }

    int wc_RNG_HealthTest(int reseed,
                                        const byte* entropyA, word32 entropyASz,
                                        const byte* entropyB, word32 entropyBSz,
                                        byte* output, word32 outputSz)
    {
        return RNG_HealthTest_fips(reseed, entropyA, entropyASz,
                              entropyB, entropyBSz, output, outputSz);
   }
#endif /* HAVE_HASHDRBG */

#else /* else build without fips, or for new fips */

#ifndef WC_NO_RNG /* if not FIPS and RNG is disabled then do not compile */

#include <wolfssl/wolfcrypt/sha256.h>

#ifdef NO_INLINE
    #include <wolfssl/wolfcrypt/misc.h>
#else
    #define WOLFSSL_MISC_INCLUDED
    #include <wolfcrypt/src/misc.c>
#endif

#if defined(WOLFSSL_SGX)
    #include <sgx_trts.h>
#elif defined(USE_WINDOWS_API)
    #ifndef _WIN32_WINNT
        #define _WIN32_WINNT 0x0400
    #endif
    #include <windows.h>
    #include <wincrypt.h>
#elif defined(HAVE_WNR)
    #include <wnr.h>
    #include <wolfssl/wolfcrypt/logging.h>
    wolfSSL_Mutex wnr_mutex;    /* global netRandom mutex */
    int wnr_timeout     = 0;    /* entropy timeout, mililseconds */
    int wnr_mutex_init  = 0;    /* flag for mutex init */
    wnr_context*  wnr_ctx;      /* global netRandom context */
#elif defined(FREESCALE_KSDK_2_0_TRNG)
    #include "fsl_trng.h"
#elif defined(FREESCALE_KSDK_2_0_RNGA)
    #include "fsl_rnga.h"

#elif defined(NO_DEV_RANDOM)
#elif defined(CUSTOM_RAND_GENERATE)
#elif defined(CUSTOM_RAND_GENERATE_BLOCK)
#elif defined(CUSTOM_RAND_GENERATE_SEED)
#elif defined(WOLFSSL_GENSEED_FORTEST)
#elif defined(WOLFSSL_MDK_ARM)
#elif defined(WOLFSSL_IAR_ARM)
#elif defined(WOLFSSL_ROWLEY_ARM)
#elif defined(WOLFSSL_EMBOS)
#elif defined(MICRIUM)
#elif defined(WOLFSSL_NUCLEUS)
#elif defined(WOLFSSL_PB)
#else
    /* include headers that may be needed to get good seed */
    #include <fcntl.h>
    #ifndef EBSNET
        #include <unistd.h>
    #endif
#endif


#if defined(HAVE_INTEL_RDRAND) || defined(HAVE_INTEL_RDSEED)
    static word32 intel_flags = 0;
    static void wc_InitRng_IntelRD(void)
    {
        intel_flags = cpuid_get_flags();
    }
    #ifdef HAVE_INTEL_RDSEED
    static int wc_GenerateSeed_IntelRD(OS_Seed* os, byte* output, word32 sz);
    #endif
    #ifdef HAVE_INTEL_RDRAND
    static int wc_GenerateRand_IntelRD(OS_Seed* os, byte* output, word32 sz);
    #endif

#ifdef USE_WINDOWS_API
    #include <immintrin.h>
#endif /* USE_WINDOWS_API */
#endif

/* Start NIST DRBG code */
#ifdef HAVE_HASHDRBG

#define OUTPUT_BLOCK_LEN  (WC_SHA256_DIGEST_SIZE)
#define MAX_REQUEST_LEN   (0x10000)
#define RESEED_INTERVAL   WC_RESEED_INTERVAL
#define SECURITY_STRENGTH (2048)
#define ENTROPY_SZ        (SECURITY_STRENGTH/8)
#define MAX_ENTROPY_SZ    (ENTROPY_SZ + ENTROPY_SZ/2)

/* Internal return codes */
#define DRBG_SUCCESS      0
#define DRBG_FAILURE      1
#define DRBG_NEED_RESEED  2
#define DRBG_CONT_FAILURE 3

/* RNG health states */
#define DRBG_NOT_INIT     0
#define DRBG_OK           1
#define DRBG_FAILED       2
#define DRBG_CONT_FAILED  3

#define RNG_HEALTH_TEST_CHECK_SIZE (WC_SHA256_DIGEST_SIZE * 4)

/* Verify max gen block len */
#if RNG_MAX_BLOCK_LEN > MAX_REQUEST_LEN
    #error RNG_MAX_BLOCK_LEN is larger than NIST DBRG max request length
#endif

enum {
    drbgInitC     = 0,
    drbgReseed    = 1,
    drbgGenerateW = 2,
    drbgGenerateH = 3,
    drbgInitV
};


typedef struct DRBG {
    word32 reseedCtr;
    word32 lastBlock;
    byte V[DRBG_SEED_LEN];
    byte C[DRBG_SEED_LEN];
#ifdef WOLFSSL_ASYNC_CRYPT
    void* heap;
    int devId;
#endif
    byte   matchCount;
#ifdef WOLFSSL_SMALL_STACK_CACHE
    wc_Sha256 sha256;
#endif
} DRBG;


static int wc_RNG_HealthTestLocal(int reseed);

/* Hash Derivation Function */
/* Returns: DRBG_SUCCESS or DRBG_FAILURE */
static int Hash_df(DRBG* drbg, byte* out, word32 outSz, byte type,
                                                  const byte* inA, word32 inASz,
                                                  const byte* inB, word32 inBSz)
{
    int ret = DRBG_FAILURE;
    byte ctr;
    int i;
    int len;
    word32 bits = (outSz * 8); /* reverse byte order */
#ifdef WOLFSSL_SMALL_STACK_CACHE
    wc_Sha256* sha = &drbg->sha256;
#else
    wc_Sha256 sha[1];
#endif
    DECLARE_VAR(digest, byte, WC_SHA256_DIGEST_SIZE, drbg->heap);

    (void)drbg;
#ifdef WOLFSSL_ASYNC_CRYPT
    if (digest == NULL)
        return DRBG_FAILURE;
#endif

#ifdef LITTLE_ENDIAN_ORDER
    bits = ByteReverseWord32(bits);
#endif
    len = (outSz / OUTPUT_BLOCK_LEN)
        + ((outSz % OUTPUT_BLOCK_LEN) ? 1 : 0);

    for (i = 0, ctr = 1; i < len; i++, ctr++) {
#ifndef WOLFSSL_SMALL_STACK_CACHE
    #ifdef WOLFSSL_ASYNC_CRYPT
        ret = wc_InitSha256_ex(sha, drbg->heap, drbg->devId);
    #else
        ret = wc_InitSha256(sha);
    #endif
        if (ret != 0)
            break;

        if (ret == 0)
#endif
            ret = wc_Sha256Update(sha, &ctr, sizeof(ctr));
        if (ret == 0)
            ret = wc_Sha256Update(sha, (byte*)&bits, sizeof(bits));

        if (ret == 0) {
            /* churning V is the only string that doesn't have the type added */
            if (type != drbgInitV)
                ret = wc_Sha256Update(sha, &type, sizeof(type));
        }
        if (ret == 0)
            ret = wc_Sha256Update(sha, inA, inASz);
        if (ret == 0) {
            if (inB != NULL && inBSz > 0)
                ret = wc_Sha256Update(sha, inB, inBSz);
        }
        if (ret == 0)
            ret = wc_Sha256Final(sha, digest);

#ifndef WOLFSSL_SMALL_STACK_CACHE
        wc_Sha256Free(sha);
#endif
        if (ret == 0) {
            if (outSz > OUTPUT_BLOCK_LEN) {
                XMEMCPY(out, digest, OUTPUT_BLOCK_LEN);
                outSz -= OUTPUT_BLOCK_LEN;
                out += OUTPUT_BLOCK_LEN;
            }
            else {
                XMEMCPY(out, digest, outSz);
            }
        }
    }

    ForceZero(digest, WC_SHA256_DIGEST_SIZE);

    FREE_VAR(digest, drbg->heap);

    return (ret == 0) ? DRBG_SUCCESS : DRBG_FAILURE;
}

/* Returns: DRBG_SUCCESS or DRBG_FAILURE */
static int Hash_DRBG_Reseed(DRBG* drbg, const byte* entropy, word32 entropySz)
{
    byte seed[DRBG_SEED_LEN];

    if (Hash_df(drbg, seed, sizeof(seed), drbgReseed, drbg->V, sizeof(drbg->V),
                                          entropy, entropySz) != DRBG_SUCCESS) {
        return DRBG_FAILURE;
    }

    XMEMCPY(drbg->V, seed, sizeof(drbg->V));
    ForceZero(seed, sizeof(seed));

    if (Hash_df(drbg, drbg->C, sizeof(drbg->C), drbgInitC, drbg->V,
                                    sizeof(drbg->V), NULL, 0) != DRBG_SUCCESS) {
        return DRBG_FAILURE;
    }

    drbg->reseedCtr = 1;
    drbg->lastBlock = 0;
    drbg->matchCount = 0;
    return DRBG_SUCCESS;
}

/* Returns: DRBG_SUCCESS and DRBG_FAILURE or BAD_FUNC_ARG on fail */
int wc_RNG_DRBG_Reseed(WC_RNG* rng, const byte* entropy, word32 entropySz)
{
    if (rng == NULL || entropy == NULL) {
        return BAD_FUNC_ARG;
    }

    return Hash_DRBG_Reseed(rng->drbg, entropy, entropySz);
}

static WC_INLINE void array_add_one(byte* data, word32 dataSz)
{
    int i;

    for (i = dataSz - 1; i >= 0; i--)
    {
        data[i]++;
        if (data[i] != 0) break;
    }
}

/* Returns: DRBG_SUCCESS or DRBG_FAILURE */
static int Hash_gen(DRBG* drbg, byte* out, word32 outSz, const byte* V)
{
    int ret = DRBG_FAILURE;
    byte data[DRBG_SEED_LEN];
    int i;
    int len;
    word32 checkBlock;
#ifdef WOLFSSL_SMALL_STACK_CACHE
    wc_Sha256* sha = &drbg->sha256;
#else
    wc_Sha256 sha[1];
#endif
    DECLARE_VAR(digest, byte, WC_SHA256_DIGEST_SIZE, drbg->heap);

    /* Special case: outSz is 0 and out is NULL. wc_Generate a block to save for
     * the continuous test. */

    if (outSz == 0) outSz = 1;

    len = (outSz / OUTPUT_BLOCK_LEN) + ((outSz % OUTPUT_BLOCK_LEN) ? 1 : 0);

    XMEMCPY(data, V, sizeof(data));
    for (i = 0; i < len; i++) {
#ifndef WOLFSSL_SMALL_STACK_CACHE
    #ifdef WOLFSSL_ASYNC_CRYPT
        ret = wc_InitSha256_ex(sha, drbg->heap, drbg->devId);
    #else
        ret = wc_InitSha256(sha);
    #endif
        if (ret == 0)
#endif
            ret = wc_Sha256Update(sha, data, sizeof(data));
        if (ret == 0)
            ret = wc_Sha256Final(sha, digest);
#ifndef WOLFSSL_SMALL_STACK_CACHE
        wc_Sha256Free(sha);
#endif

        if (ret == 0) {
            XMEMCPY(&checkBlock, digest, sizeof(word32));
            if (drbg->reseedCtr > 1 && checkBlock == drbg->lastBlock) {
                if (drbg->matchCount == 1) {
                    return DRBG_CONT_FAILURE;
                }
                else {
                    if (i == len) {
                        len++;
                    }
                    drbg->matchCount = 1;
                }
            }
            else {
                drbg->matchCount = 0;
                drbg->lastBlock = checkBlock;
            }

            if (out != NULL && outSz != 0) {
                if (outSz >= OUTPUT_BLOCK_LEN) {
                    XMEMCPY(out, digest, OUTPUT_BLOCK_LEN);
                    outSz -= OUTPUT_BLOCK_LEN;
                    out += OUTPUT_BLOCK_LEN;
                    array_add_one(data, DRBG_SEED_LEN);
                }
                else {
                    XMEMCPY(out, digest, outSz);
                    outSz = 0;
                }
            }
        }
    }
    ForceZero(data, sizeof(data));

    FREE_VAR(digest, drbg->heap);

    return (ret == 0) ? DRBG_SUCCESS : DRBG_FAILURE;
}

static WC_INLINE void array_add(byte* d, word32 dLen, const byte* s, word32 sLen)
{
    word16 carry = 0;

    if (dLen > 0 && sLen > 0 && dLen >= sLen) {
        int sIdx, dIdx;

        for (sIdx = sLen - 1, dIdx = dLen - 1; sIdx >= 0; dIdx--, sIdx--)
        {
            carry += d[dIdx] + s[sIdx];
            d[dIdx] = (byte)carry;
            carry >>= 8;
        }

        for (; carry != 0 && dIdx >= 0; dIdx--) {
            carry += d[dIdx];
            d[dIdx] = (byte)carry;
            carry >>= 8;
        }
    }
}

/* Returns: DRBG_SUCCESS, DRBG_NEED_RESEED, or DRBG_FAILURE */
static int Hash_DRBG_Generate(DRBG* drbg, byte* out, word32 outSz)
{
    int ret;
#ifdef WOLFSSL_SMALL_STACK_CACHE
    wc_Sha256* sha = &drbg->sha256;
#else
    wc_Sha256 sha[1];
#endif
    byte type;
    word32 reseedCtr;

    if (drbg->reseedCtr == RESEED_INTERVAL) {
        return DRBG_NEED_RESEED;
    } else {
        DECLARE_VAR(digest, byte, WC_SHA256_DIGEST_SIZE, drbg->heap);
        type = drbgGenerateH;
        reseedCtr = drbg->reseedCtr;

        ret = Hash_gen(drbg, out, outSz, drbg->V);
        if (ret == DRBG_SUCCESS) {
#ifndef WOLFSSL_SMALL_STACK_CACHE
        #ifdef WOLFSSL_ASYNC_CRYPT
            ret = wc_InitSha256_ex(sha, drbg->heap, drbg->devId);
        #else
            ret = wc_InitSha256(sha);
        #endif
            if (ret == 0)
#endif
                ret = wc_Sha256Update(sha, &type, sizeof(type));
            if (ret == 0)
                ret = wc_Sha256Update(sha, drbg->V, sizeof(drbg->V));
            if (ret == 0)
                ret = wc_Sha256Final(sha, digest);

#ifndef WOLFSSL_SMALL_STACK_CACHE
            wc_Sha256Free(sha);
#endif

            if (ret == 0) {
                array_add(drbg->V, sizeof(drbg->V), digest, WC_SHA256_DIGEST_SIZE);
                array_add(drbg->V, sizeof(drbg->V), drbg->C, sizeof(drbg->C));
            #ifdef LITTLE_ENDIAN_ORDER
                reseedCtr = ByteReverseWord32(reseedCtr);
            #endif
                array_add(drbg->V, sizeof(drbg->V),
                                          (byte*)&reseedCtr, sizeof(reseedCtr));
                ret = DRBG_SUCCESS;
            }
            drbg->reseedCtr++;
        }
        ForceZero(digest, WC_SHA256_DIGEST_SIZE);
        FREE_VAR(digest, drbg->heap);
    }

    return (ret == 0) ? DRBG_SUCCESS : DRBG_FAILURE;
}

/* Returns: DRBG_SUCCESS or DRBG_FAILURE */
static int Hash_DRBG_Instantiate(DRBG* drbg, const byte* seed, word32 seedSz,
                                             const byte* nonce, word32 nonceSz,
                                             void* heap, int devId)
{
    int ret = DRBG_FAILURE;

    XMEMSET(drbg, 0, sizeof(DRBG));
#ifdef WOLFSSL_ASYNC_CRYPT
    drbg->heap = heap;
    drbg->devId = devId;
#else
    (void)heap;
    (void)devId;
#endif

#ifdef WOLFSSL_SMALL_STACK_CACHE
    #ifdef WOLFSSL_ASYNC_CRYPT
        ret = wc_InitSha256_ex(&drbg->sha256, drbg->heap, drbg->devId);
    #else
        ret = wc_InitSha256(&drbg->sha256);
    #endif
    if (ret != 0)
        return ret;
#endif

    if (Hash_df(drbg, drbg->V, sizeof(drbg->V), drbgInitV, seed, seedSz,
                                              nonce, nonceSz) == DRBG_SUCCESS &&
        Hash_df(drbg, drbg->C, sizeof(drbg->C), drbgInitC, drbg->V,
                                    sizeof(drbg->V), NULL, 0) == DRBG_SUCCESS) {

        drbg->reseedCtr = 1;
        drbg->lastBlock = 0;
        drbg->matchCount = 0;
        ret = DRBG_SUCCESS;
    }

    return ret;
}

/* Returns: DRBG_SUCCESS or DRBG_FAILURE */
static int Hash_DRBG_Uninstantiate(DRBG* drbg)
{
    word32 i;
    int    compareSum = 0;
    byte*  compareDrbg = (byte*)drbg;

#ifdef WOLFSSL_SMALL_STACK_CACHE
    wc_Sha256Free(&drbg->sha256);
#endif

    ForceZero(drbg, sizeof(DRBG));

    for (i = 0; i < sizeof(DRBG); i++)
        compareSum |= compareDrbg[i] ^ 0;

    return (compareSum == 0) ? DRBG_SUCCESS : DRBG_FAILURE;
}
#endif /* HAVE_HASHDRBG */
/* End NIST DRBG Code */


static int _InitRng(WC_RNG* rng, byte* nonce, word32 nonceSz,
                    void* heap, int devId)
{
    int ret = RNG_FAILURE_E;
#ifdef HAVE_HASHDRBG
    word32 entropySz = ENTROPY_SZ;
#endif

    (void)nonce;
    (void)nonceSz;

    if (rng == NULL)
        return BAD_FUNC_ARG;
    if (nonce == NULL && nonceSz != 0)
        return BAD_FUNC_ARG;

#ifdef WOLFSSL_HEAP_TEST
    rng->heap = (void*)WOLFSSL_HEAP_TEST;
    (void)heap;
#else
    rng->heap = heap;
#endif
#ifdef WOLFSSL_ASYNC_CRYPT
    rng->devId = devId;
#else
    (void)devId;
#endif

#ifdef HAVE_HASHDRBG
    /* init the DBRG to known values */
    rng->drbg = NULL;
    rng->status = DRBG_NOT_INIT;
#endif

#if defined(HAVE_INTEL_RDSEED) || defined(HAVE_INTEL_RDRAND)
    /* init the intel RD seed and/or rand */
    wc_InitRng_IntelRD();
#endif

    /* configure async RNG source if available */
#ifdef WOLFSSL_ASYNC_CRYPT
    ret = wolfAsync_DevCtxInit(&rng->asyncDev, WOLFSSL_ASYNC_MARKER_RNG,
                                                        rng->heap, rng->devId);
    if (ret != 0)
        return ret;
#endif

#ifdef HAVE_INTEL_RDRAND
    /* if CPU supports RDRAND, use it directly and by-pass DRBG init */
    if (IS_INTEL_RDRAND(intel_flags))
        return 0;
#endif

#ifdef CUSTOM_RAND_GENERATE_BLOCK
	ret = 0; /* success */
#else
#ifdef HAVE_HASHDRBG
    if (nonceSz == 0)
        entropySz = MAX_ENTROPY_SZ;

    if (wc_RNG_HealthTestLocal(0) == 0) {
        DECLARE_VAR(entropy, byte, MAX_ENTROPY_SZ, rng->heap);

        rng->drbg =
                (struct DRBG*)XMALLOC(sizeof(DRBG), rng->heap,
                                                          DYNAMIC_TYPE_RNG);
        if (rng->drbg == NULL) {
            ret = MEMORY_E;
        }
        else if (wc_GenerateSeed(&rng->seed, entropy, entropySz) == 0 &&
                 Hash_DRBG_Instantiate(rng->drbg, entropy, entropySz,
                            nonce, nonceSz, rng->heap, devId) == DRBG_SUCCESS) {
            ret = Hash_DRBG_Generate(rng->drbg, NULL, 0);
        }
        else
            ret = DRBG_FAILURE;

        ForceZero(entropy, entropySz);
        FREE_VAR(entropy, rng->heap);
    }
    else
        ret = DRBG_CONT_FAILURE;

    if (ret == DRBG_SUCCESS) {
        rng->status = DRBG_OK;
        ret = 0;
    }
    else if (ret == DRBG_CONT_FAILURE) {
        rng->status = DRBG_CONT_FAILED;
        ret = DRBG_CONT_FIPS_E;
    }
    else if (ret == DRBG_FAILURE) {
        rng->status = DRBG_FAILED;
        ret = RNG_FAILURE_E;
    }
    else {
        rng->status = DRBG_FAILED;
    }
#endif /* HAVE_HASHDRBG */
#endif /* CUSTOM_RAND_GENERATE_BLOCK */

    return ret;
}


int wc_InitRng(WC_RNG* rng)
{
    return _InitRng(rng, NULL, 0, NULL, INVALID_DEVID);
}


int wc_InitRng_ex(WC_RNG* rng, void* heap, int devId)
{
    return _InitRng(rng, NULL, 0, heap, devId);
}


int wc_InitRngNonce(WC_RNG* rng, byte* nonce, word32 nonceSz)
{
    return _InitRng(rng, nonce, nonceSz, NULL, INVALID_DEVID);
}


int wc_InitRngNonce_ex(WC_RNG* rng, byte* nonce, word32 nonceSz,
                       void* heap, int devId)
{
    return _InitRng(rng, nonce, nonceSz, heap, devId);
}


/* place a generated block in output */
int wc_RNG_GenerateBlock(WC_RNG* rng, byte* output, word32 sz)
{
    int ret;

    if (rng == NULL || output == NULL)
        return BAD_FUNC_ARG;

#ifdef HAVE_INTEL_RDRAND
    if (IS_INTEL_RDRAND(intel_flags))
        return wc_GenerateRand_IntelRD(NULL, output, sz);
#endif

#if defined(WOLFSSL_ASYNC_CRYPT)
    if (rng->asyncDev.marker == WOLFSSL_ASYNC_MARKER_RNG) {
        /* these are blocking */
    #ifdef HAVE_CAVIUM
        return NitroxRngGenerateBlock(rng, output, sz);
    #elif defined(HAVE_INTEL_QA)
        return IntelQaDrbg(&rng->asyncDev, output, sz);
    #else
        /* simulator not supported */
    #endif
    }
#endif

#ifdef CUSTOM_RAND_GENERATE_BLOCK
    XMEMSET(output, 0, sz);
    ret = CUSTOM_RAND_GENERATE_BLOCK(output, sz);
#else

#ifdef HAVE_HASHDRBG
    if (sz > RNG_MAX_BLOCK_LEN)
        return BAD_FUNC_ARG;

    if (rng->status != DRBG_OK)
        return RNG_FAILURE_E;

    ret = Hash_DRBG_Generate(rng->drbg, output, sz);
    if (ret == DRBG_NEED_RESEED) {
        if (wc_RNG_HealthTestLocal(1) == 0) {
            byte entropy[ENTROPY_SZ];

            if (wc_GenerateSeed(&rng->seed, entropy, ENTROPY_SZ) == 0 &&
                Hash_DRBG_Reseed(rng->drbg, entropy, ENTROPY_SZ)
                                                              == DRBG_SUCCESS) {

                ret = Hash_DRBG_Generate(rng->drbg, NULL, 0);
                if (ret == DRBG_SUCCESS)
                    ret = Hash_DRBG_Generate(rng->drbg, output, sz);
            }
            else
                ret = DRBG_FAILURE;

            ForceZero(entropy, ENTROPY_SZ);
        }
        else
            ret = DRBG_CONT_FAILURE;
    }

    if (ret == DRBG_SUCCESS) {
        ret = 0;
    }
    else if (ret == DRBG_CONT_FAILURE) {
        ret = DRBG_CONT_FIPS_E;
        rng->status = DRBG_CONT_FAILED;
    }
    else {
        ret = RNG_FAILURE_E;
        rng->status = DRBG_FAILED;
    }
#else

    /* if we get here then there is an RNG configuration error */
    ret = RNG_FAILURE_E;

#endif /* HAVE_HASHDRBG */
#endif /* CUSTOM_RAND_GENERATE_BLOCK */

    return ret;
}


int wc_RNG_GenerateByte(WC_RNG* rng, byte* b)
{
    return wc_RNG_GenerateBlock(rng, b, 1);
}


int wc_FreeRng(WC_RNG* rng)
{
    int ret = 0;

    if (rng == NULL)
        return BAD_FUNC_ARG;

#if defined(WOLFSSL_ASYNC_CRYPT)
    wolfAsync_DevCtxFree(&rng->asyncDev, WOLFSSL_ASYNC_MARKER_RNG);
#endif

#ifdef HAVE_HASHDRBG
    if (rng->drbg != NULL) {
        if (Hash_DRBG_Uninstantiate(rng->drbg) != DRBG_SUCCESS)
            ret = RNG_FAILURE_E;

        XFREE(rng->drbg, rng->heap, DYNAMIC_TYPE_RNG);
        rng->drbg = NULL;
    }

    rng->status = DRBG_NOT_INIT;
#endif /* HAVE_HASHDRBG */

    return ret;
}

#ifdef HAVE_HASHDRBG
int wc_RNG_HealthTest(int reseed, const byte* entropyA, word32 entropyASz,
                                  const byte* entropyB, word32 entropyBSz,
                                  byte* output, word32 outputSz)
{
    return wc_RNG_HealthTest_ex(reseed, NULL, 0,
                                entropyA, entropyASz,
                                entropyB, entropyBSz,
                                output, outputSz,
                                NULL, INVALID_DEVID);
}


int wc_RNG_HealthTest_ex(int reseed, const byte* nonce, word32 nonceSz,
                                  const byte* entropyA, word32 entropyASz,
                                  const byte* entropyB, word32 entropyBSz,
                                  byte* output, word32 outputSz,
                                  void* heap, int devId)
{
    int ret = -1;
    DRBG* drbg;
#ifndef WOLFSSL_SMALL_STACK
    DRBG  drbg_var;
#endif

    if (entropyA == NULL || output == NULL) {
        return BAD_FUNC_ARG;
    }

    if (reseed != 0 && entropyB == NULL) {
        return BAD_FUNC_ARG;
    }

    if (outputSz != RNG_HEALTH_TEST_CHECK_SIZE) {
        return ret;
    }

#ifdef WOLFSSL_SMALL_STACK
    drbg = (struct DRBG*)XMALLOC(sizeof(DRBG), NULL, DYNAMIC_TYPE_RNG);
    if (drbg == NULL) {
        return MEMORY_E;
    }
#else
    drbg = &drbg_var;
#endif

    if (Hash_DRBG_Instantiate(drbg, entropyA, entropyASz, nonce, nonceSz,
                              heap, devId) != 0) {
        goto exit_rng_ht;
    }

    if (reseed) {
        if (Hash_DRBG_Reseed(drbg, entropyB, entropyBSz) != 0) {
            goto exit_rng_ht;
        }
    }

    if (Hash_DRBG_Generate(drbg, output, outputSz) != 0) {
        goto exit_rng_ht;
    }

    if (Hash_DRBG_Generate(drbg, output, outputSz) != 0) {
        goto exit_rng_ht;
    }

    /* Mark success */
    ret = 0;

exit_rng_ht:

    /* This is safe to call even if Hash_DRBG_Instantiate fails */
    if (Hash_DRBG_Uninstantiate(drbg) != 0) {
        ret = -1;
    }

#ifdef WOLFSSL_SMALL_STACK
    XFREE(drbg, NULL, DYNAMIC_TYPE_RNG);
#endif

    return ret;
}


const byte entropyA[] = {
    0x63, 0x36, 0x33, 0x77, 0xe4, 0x1e, 0x86, 0x46, 0x8d, 0xeb, 0x0a, 0xb4,
    0xa8, 0xed, 0x68, 0x3f, 0x6a, 0x13, 0x4e, 0x47, 0xe0, 0x14, 0xc7, 0x00,
    0x45, 0x4e, 0x81, 0xe9, 0x53, 0x58, 0xa5, 0x69, 0x80, 0x8a, 0xa3, 0x8f,
    0x2a, 0x72, 0xa6, 0x23, 0x59, 0x91, 0x5a, 0x9f, 0x8a, 0x04, 0xca, 0x68
};

const byte reseedEntropyA[] = {
    0xe6, 0x2b, 0x8a, 0x8e, 0xe8, 0xf1, 0x41, 0xb6, 0x98, 0x05, 0x66, 0xe3,
    0xbf, 0xe3, 0xc0, 0x49, 0x03, 0xda, 0xd4, 0xac, 0x2c, 0xdf, 0x9f, 0x22,
    0x80, 0x01, 0x0a, 0x67, 0x39, 0xbc, 0x83, 0xd3
};

const byte outputA[] = {
    0x04, 0xee, 0xc6, 0x3b, 0xb2, 0x31, 0xdf, 0x2c, 0x63, 0x0a, 0x1a, 0xfb,
    0xe7, 0x24, 0x94, 0x9d, 0x00, 0x5a, 0x58, 0x78, 0x51, 0xe1, 0xaa, 0x79,
    0x5e, 0x47, 0x73, 0x47, 0xc8, 0xb0, 0x56, 0x62, 0x1c, 0x18, 0xbd, 0xdc,
    0xdd, 0x8d, 0x99, 0xfc, 0x5f, 0xc2, 0xb9, 0x20, 0x53, 0xd8, 0xcf, 0xac,
    0xfb, 0x0b, 0xb8, 0x83, 0x12, 0x05, 0xfa, 0xd1, 0xdd, 0xd6, 0xc0, 0x71,
    0x31, 0x8a, 0x60, 0x18, 0xf0, 0x3b, 0x73, 0xf5, 0xed, 0xe4, 0xd4, 0xd0,
    0x71, 0xf9, 0xde, 0x03, 0xfd, 0x7a, 0xea, 0x10, 0x5d, 0x92, 0x99, 0xb8,
    0xaf, 0x99, 0xaa, 0x07, 0x5b, 0xdb, 0x4d, 0xb9, 0xaa, 0x28, 0xc1, 0x8d,
    0x17, 0x4b, 0x56, 0xee, 0x2a, 0x01, 0x4d, 0x09, 0x88, 0x96, 0xff, 0x22,
    0x82, 0xc9, 0x55, 0xa8, 0x19, 0x69, 0xe0, 0x69, 0xfa, 0x8c, 0xe0, 0x07,
    0xa1, 0x80, 0x18, 0x3a, 0x07, 0xdf, 0xae, 0x17
};

const byte entropyB[] = {
    0xa6, 0x5a, 0xd0, 0xf3, 0x45, 0xdb, 0x4e, 0x0e, 0xff, 0xe8, 0x75, 0xc3,
    0xa2, 0xe7, 0x1f, 0x42, 0xc7, 0x12, 0x9d, 0x62, 0x0f, 0xf5, 0xc1, 0x19,
    0xa9, 0xef, 0x55, 0xf0, 0x51, 0x85, 0xe0, 0xfb, /* nonce next */
    0x85, 0x81, 0xf9, 0x31, 0x75, 0x17, 0x27, 0x6e, 0x06, 0xe9, 0x60, 0x7d,
    0xdb, 0xcb, 0xcc, 0x2e
};

const byte outputB[] = {
    0xd3, 0xe1, 0x60, 0xc3, 0x5b, 0x99, 0xf3, 0x40, 0xb2, 0x62, 0x82, 0x64,
    0xd1, 0x75, 0x10, 0x60, 0xe0, 0x04, 0x5d, 0xa3, 0x83, 0xff, 0x57, 0xa5,
    0x7d, 0x73, 0xa6, 0x73, 0xd2, 0xb8, 0xd8, 0x0d, 0xaa, 0xf6, 0xa6, 0xc3,
    0x5a, 0x91, 0xbb, 0x45, 0x79, 0xd7, 0x3f, 0xd0, 0xc8, 0xfe, 0xd1, 0x11,
    0xb0, 0x39, 0x13, 0x06, 0x82, 0x8a, 0xdf, 0xed, 0x52, 0x8f, 0x01, 0x81,
    0x21, 0xb3, 0xfe, 0xbd, 0xc3, 0x43, 0xe7, 0x97, 0xb8, 0x7d, 0xbb, 0x63,
    0xdb, 0x13, 0x33, 0xde, 0xd9, 0xd1, 0xec, 0xe1, 0x77, 0xcf, 0xa6, 0xb7,
    0x1f, 0xe8, 0xab, 0x1d, 0xa4, 0x66, 0x24, 0xed, 0x64, 0x15, 0xe5, 0x1c,
    0xcd, 0xe2, 0xc7, 0xca, 0x86, 0xe2, 0x83, 0x99, 0x0e, 0xea, 0xeb, 0x91,
    0x12, 0x04, 0x15, 0x52, 0x8b, 0x22, 0x95, 0x91, 0x02, 0x81, 0xb0, 0x2d,
    0xd4, 0x31, 0xf4, 0xc9, 0xf7, 0x04, 0x27, 0xdf
};


static int wc_RNG_HealthTestLocal(int reseed)
{
    int ret = 0;
#ifdef WOLFSSL_SMALL_STACK
    byte* check;
#else
    byte  check[RNG_HEALTH_TEST_CHECK_SIZE];
#endif

#ifdef WOLFSSL_SMALL_STACK
    check = (byte*)XMALLOC(RNG_HEALTH_TEST_CHECK_SIZE, NULL,
                           DYNAMIC_TYPE_TMP_BUFFER);
    if (check == NULL) {
        return MEMORY_E;
    }
#endif

    if (reseed) {
        ret = wc_RNG_HealthTest(1, entropyA, sizeof(entropyA),
                                reseedEntropyA, sizeof(reseedEntropyA),
                                check, RNG_HEALTH_TEST_CHECK_SIZE);
        if (ret == 0) {
            if (ConstantCompare(check, outputA,
                                RNG_HEALTH_TEST_CHECK_SIZE) != 0)
                ret = -1;
        }
    }
    else {
        ret = wc_RNG_HealthTest(0, entropyB, sizeof(entropyB),
                                NULL, 0,
                                check, RNG_HEALTH_TEST_CHECK_SIZE);
        if (ret == 0) {
            if (ConstantCompare(check, outputB,
                                RNG_HEALTH_TEST_CHECK_SIZE) != 0)
                ret = -1;
        }

        /* The previous test cases use a large seed instead of a seed and nonce.
         * entropyB is actually from a test case with a seed and nonce, and
         * just concatenates them. The pivot point between seed and nonce is
         * byte 32, feed them into the health test separately. */
        if (ret == 0) {
            ret = wc_RNG_HealthTest_ex(0,
                                    entropyB + 32, sizeof(entropyB) - 32,
                                    entropyB, 32,
                                    NULL, 0,
                                    check, RNG_HEALTH_TEST_CHECK_SIZE,
                                    NULL, INVALID_DEVID);
            if (ret == 0) {
                if (ConstantCompare(check, outputB, sizeof(outputB)) != 0)
                    ret = -1;
            }
        }
    }

#ifdef WOLFSSL_SMALL_STACK
    XFREE(check, NULL, DYNAMIC_TYPE_TMP_BUFFER);
#endif

    return ret;
}

#endif /* HAVE_HASHDRBG */


#ifdef HAVE_WNR

/*
 * Init global Whitewood netRandom context
 * Returns 0 on success, negative on error
 */
int wc_InitNetRandom(const char* configFile, wnr_hmac_key hmac_cb, int timeout)
{
    if (configFile == NULL || timeout < 0)
        return BAD_FUNC_ARG;

    if (wnr_mutex_init > 0) {
        WOLFSSL_MSG("netRandom context already created, skipping");
        return 0;
    }

    if (wc_InitMutex(&wnr_mutex) != 0) {
        WOLFSSL_MSG("Bad Init Mutex wnr_mutex");
        return BAD_MUTEX_E;
    }
    wnr_mutex_init = 1;

    if (wc_LockMutex(&wnr_mutex) != 0) {
        WOLFSSL_MSG("Bad Lock Mutex wnr_mutex");
        return BAD_MUTEX_E;
    }

    /* store entropy timeout */
    wnr_timeout = timeout;

    /* create global wnr_context struct */
    if (wnr_create(&wnr_ctx) != WNR_ERROR_NONE) {
        WOLFSSL_MSG("Error creating global netRandom context");
        return RNG_FAILURE_E;
    }

    /* load config file */
    if (wnr_config_loadf(wnr_ctx, (char*)configFile) != WNR_ERROR_NONE) {
        WOLFSSL_MSG("Error loading config file into netRandom context");
        wnr_destroy(wnr_ctx);
        wnr_ctx = NULL;
        return RNG_FAILURE_E;
    }

    /* create/init polling mechanism */
    if (wnr_poll_create() != WNR_ERROR_NONE) {
        printf("ERROR: wnr_poll_create() failed\n");
        WOLFSSL_MSG("Error initializing netRandom polling mechanism");
        wnr_destroy(wnr_ctx);
        wnr_ctx = NULL;
        return RNG_FAILURE_E;
    }

    /* validate config, set HMAC callback (optional) */
    if (wnr_setup(wnr_ctx, hmac_cb) != WNR_ERROR_NONE) {
        WOLFSSL_MSG("Error setting up netRandom context");
        wnr_destroy(wnr_ctx);
        wnr_ctx = NULL;
        wnr_poll_destroy();
        return RNG_FAILURE_E;
    }

    wc_UnLockMutex(&wnr_mutex);

    return 0;
}

/*
 * Free global Whitewood netRandom context
 * Returns 0 on success, negative on error
 */
int wc_FreeNetRandom(void)
{
    if (wnr_mutex_init > 0) {

        if (wc_LockMutex(&wnr_mutex) != 0) {
            WOLFSSL_MSG("Bad Lock Mutex wnr_mutex");
            return BAD_MUTEX_E;
        }

        if (wnr_ctx != NULL) {
            wnr_destroy(wnr_ctx);
            wnr_ctx = NULL;
        }
        wnr_poll_destroy();

        wc_UnLockMutex(&wnr_mutex);

        wc_FreeMutex(&wnr_mutex);
        wnr_mutex_init = 0;
    }

    return 0;
}

#endif /* HAVE_WNR */


#if defined(HAVE_INTEL_RDRAND) || defined(HAVE_INTEL_RDSEED)

#ifdef WOLFSSL_ASYNC_CRYPT
    /* need more retries if multiple cores */
    #define INTELRD_RETRY (32 * 8)
#else
    #define INTELRD_RETRY 32
#endif

#ifdef HAVE_INTEL_RDSEED

#ifndef USE_WINDOWS_API

    /* return 0 on success */
    static WC_INLINE int IntelRDseed64(word64* seed)
    {
        unsigned char ok;

        __asm__ volatile("rdseed %0; setc %1":"=r"(*seed), "=qm"(ok));
        return (ok) ? 0 : -1;
    }

#else /* USE_WINDOWS_API */
    /* The compiler Visual Studio uses does not allow inline assembly.
     * It does allow for Intel intrinsic functions. */

    /* return 0 on success */
    static WC_INLINE int IntelRDseed64(word64* seed)
    {
        int ok;

        ok = _rdseed64_step(seed);
        return (ok) ? 0 : -1;
    }

#endif /* USE_WINDOWS_API */

/* return 0 on success */
static WC_INLINE int IntelRDseed64_r(word64* rnd)
{
    int i;
    for (i = 0; i < INTELRD_RETRY; i++) {
        if (IntelRDseed64(rnd) == 0)
            return 0;
    }
    return -1;
}

/* return 0 on success */
static int wc_GenerateSeed_IntelRD(OS_Seed* os, byte* output, word32 sz)
{
    int ret;
    word64 rndTmp;

    (void)os;

    if (!IS_INTEL_RDSEED(intel_flags))
        return -1;

    for (; (sz / sizeof(word64)) > 0; sz -= sizeof(word64),
                                                    output += sizeof(word64)) {
        ret = IntelRDseed64_r((word64*)output);
        if (ret != 0)
            return ret;
    }
    if (sz == 0)
        return 0;

    /* handle unaligned remainder */
    ret = IntelRDseed64_r(&rndTmp);
    if (ret != 0)
        return ret;

    XMEMCPY(output, &rndTmp, sz);
    ForceZero(&rndTmp, sizeof(rndTmp));

    return 0;
}

#endif /* HAVE_INTEL_RDSEED */

#ifdef HAVE_INTEL_RDRAND

#ifndef USE_WINDOWS_API

/* return 0 on success */
static WC_INLINE int IntelRDrand64(word64 *rnd)
{
    unsigned char ok;

    __asm__ volatile("rdrand %0; setc %1":"=r"(*rnd), "=qm"(ok));

    return (ok) ? 0 : -1;
}

#else /* USE_WINDOWS_API */
    /* The compiler Visual Studio uses does not allow inline assembly.
     * It does allow for Intel intrinsic functions. */

/* return 0 on success */
static WC_INLINE int IntelRDrand64(word64 *rnd)
{
    int ok;

    ok = _rdrand64_step(rnd);

    return (ok) ? 0 : -1;
}

#endif /* USE_WINDOWS_API */

/* return 0 on success */
static WC_INLINE int IntelRDrand64_r(word64 *rnd)
{
    int i;
    for (i = 0; i < INTELRD_RETRY; i++) {
        if (IntelRDrand64(rnd) == 0)
            return 0;
    }
    return -1;
}

/* return 0 on success */
static int wc_GenerateRand_IntelRD(OS_Seed* os, byte* output, word32 sz)
{
    int ret;
    word64 rndTmp;

    (void)os;

    if (!IS_INTEL_RDRAND(intel_flags))
        return -1;

    for (; (sz / sizeof(word64)) > 0; sz -= sizeof(word64),
                                                    output += sizeof(word64)) {
        ret = IntelRDrand64_r((word64 *)output);
        if (ret != 0)
            return ret;
    }
    if (sz == 0)
        return 0;

    /* handle unaligned remainder */
    ret = IntelRDrand64_r(&rndTmp);
    if (ret != 0)
        return ret;

    XMEMCPY(output, &rndTmp, sz);

    return 0;
}

#endif /* HAVE_INTEL_RDRAND */
#endif /* HAVE_INTEL_RDRAND || HAVE_INTEL_RDSEED */


/* Begin wc_GenerateSeed Implementations */
#if defined(CUSTOM_RAND_GENERATE_SEED)

    /* Implement your own random generation function
     * Return 0 to indicate success
     * int rand_gen_seed(byte* output, word32 sz);
     * #define CUSTOM_RAND_GENERATE_SEED  rand_gen_seed */

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        (void)os; /* Suppress unused arg warning */
        return CUSTOM_RAND_GENERATE_SEED(output, sz);
    }

#elif defined(CUSTOM_RAND_GENERATE_SEED_OS)

    /* Implement your own random generation function,
     *  which includes OS_Seed.
     * Return 0 to indicate success
     * int rand_gen_seed(OS_Seed* os, byte* output, word32 sz);
     * #define CUSTOM_RAND_GENERATE_SEED_OS  rand_gen_seed */

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        return CUSTOM_RAND_GENERATE_SEED_OS(os, output, sz);
    }

#elif defined(CUSTOM_RAND_GENERATE)

   /* Implement your own random generation function
    * word32 rand_gen(void);
    * #define CUSTOM_RAND_GENERATE  rand_gen  */

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        word32 i = 0;

        (void)os;

        while (i < sz)
        {
            /* If not aligned or there is odd/remainder */
            if( (i + sizeof(CUSTOM_RAND_TYPE)) > sz ||
                ((wolfssl_word)&output[i] % sizeof(CUSTOM_RAND_TYPE)) != 0
            ) {
                /* Single byte at a time */
                output[i++] = (byte)CUSTOM_RAND_GENERATE();
            }
            else {
                /* Use native 8, 16, 32 or 64 copy instruction */
                *((CUSTOM_RAND_TYPE*)&output[i]) = CUSTOM_RAND_GENERATE();
                i += sizeof(CUSTOM_RAND_TYPE);
            }
        }

        return 0;
    }

#elif defined(WOLFSSL_SGX)

int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
{
	int ret = !SGX_SUCCESS;
	int i, read_max = 10;

	for (i = 0; i < read_max && ret != SGX_SUCCESS; i++) {
		ret = sgx_read_rand(output, sz);
	}

	(void)os;
	return (ret == SGX_SUCCESS) ? 0 : 1;
}

#elif defined(USE_WINDOWS_API)

int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
{
    if(!CryptAcquireContext(&os->handle, 0, 0, PROV_RSA_FULL,
                            CRYPT_VERIFYCONTEXT))
        return WINCRYPT_E;

    if (!CryptGenRandom(os->handle, sz, output))
        return CRYPTGEN_E;

    CryptReleaseContext(os->handle, 0);

    return 0;
}


#elif defined(HAVE_RTP_SYS) || defined(EBSNET)

#include "rtprand.h"   /* rtp_rand () */
#include "rtptime.h"   /* rtp_get_system_msec() */


int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
{
    int i;
    rtp_srand(rtp_get_system_msec());

    for (i = 0; i < sz; i++ ) {
        output[i] = rtp_rand() % 256;
        if ( (i % 8) == 7)
            rtp_srand(rtp_get_system_msec());
    }

    return 0;
}


#elif defined(MICROCHIP_PIC32)

    #ifdef MICROCHIP_MPLAB_HARMONY
        #define PIC32_SEED_COUNT _CP0_GET_COUNT
    #else
        #if !defined(WOLFSSL_MICROCHIP_PIC32MZ)
            #include <peripheral/timer.h>
        #endif
        extern word32 ReadCoreTimer(void);
        #define PIC32_SEED_COUNT ReadCoreTimer
    #endif

    #ifdef WOLFSSL_PIC32MZ_RNG
        #include "xc.h"
        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            int i;
            byte rnd[8];
            word32 *rnd32 = (word32 *)rnd;
            word32 size = sz;
            byte* op = output;

#if ((__PIC32_FEATURE_SET0 == 'E') && (__PIC32_FEATURE_SET1 == 'C'))
            RNGNUMGEN1 = _CP0_GET_COUNT();
            RNGPOLY1 = _CP0_GET_COUNT();
            RNGPOLY2 = _CP0_GET_COUNT();
            RNGNUMGEN2 = _CP0_GET_COUNT();
#else
            // All others can be seeded from the TRNG
            RNGCONbits.TRNGMODE = 1;
            RNGCONbits.TRNGEN = 1;
            while (RNGCNT < 64);
            RNGCONbits.LOAD = 1;
            while (RNGCONbits.LOAD == 1);
            while (RNGCNT < 64);
            RNGPOLY2 = RNGSEED2;
            RNGPOLY1 = RNGSEED1;
#endif

            RNGCONbits.PLEN = 0x40;
            RNGCONbits.PRNGEN = 1;
            for (i=0; i<5; i++) { /* wait for RNGNUMGEN ready */
                volatile int x;
                x = RNGNUMGEN1;
                x = RNGNUMGEN2;
                (void)x;
            }
            do {
                rnd32[0] = RNGNUMGEN1;
                rnd32[1] = RNGNUMGEN2;

                for(i=0; i<8; i++, op++) {
                    *op = rnd[i];
                    size --;
                    if(size==0)break;
                }
            } while(size);
            return 0;
        }
    #else  /* WOLFSSL_PIC32MZ_RNG */
        /* uses the core timer, in nanoseconds to seed srand */
        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            int i;
            srand(PIC32_SEED_COUNT() * 25);

            for (i = 0; i < sz; i++ ) {
                output[i] = rand() % 256;
                if ( (i % 8) == 7)
                    srand(PIC32_SEED_COUNT() * 25);
            }
            return 0;
        }
    #endif /* WOLFSSL_PIC32MZ_RNG */

#elif defined(FREESCALE_MQX) || defined(FREESCALE_KSDK_MQX) || \
      defined(FREESCALE_KSDK_BM) || defined(FREESCALE_FREE_RTOS)

    #if defined(FREESCALE_K70_RNGA) || defined(FREESCALE_RNGA)
        /*
         * wc_Generates a RNG seed using the Random Number Generator Accelerator
         * on the Kinetis K70. Documentation located in Chapter 37 of
         * K70 Sub-Family Reference Manual (see Note 3 in the README for link).
         */
        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            word32 i;

            /* turn on RNGA module */
            #if defined(SIM_SCGC3_RNGA_MASK)
                SIM_SCGC3 |= SIM_SCGC3_RNGA_MASK;
            #endif
            #if defined(SIM_SCGC6_RNGA_MASK)
                /* additionally needed for at least K64F */
                SIM_SCGC6 |= SIM_SCGC6_RNGA_MASK;
            #endif

            /* set SLP bit to 0 - "RNGA is not in sleep mode" */
            RNG_CR &= ~RNG_CR_SLP_MASK;

            /* set HA bit to 1 - "security violations masked" */
            RNG_CR |= RNG_CR_HA_MASK;

            /* set GO bit to 1 - "output register loaded with data" */
            RNG_CR |= RNG_CR_GO_MASK;

            for (i = 0; i < sz; i++) {

                /* wait for RNG FIFO to be full */
                while((RNG_SR & RNG_SR_OREG_LVL(0xF)) == 0) {}

                /* get value */
                output[i] = RNG_OR;
            }

            return 0;
        }

    #elif defined(FREESCALE_K53_RNGB) || defined(FREESCALE_RNGB)
        /*
         * wc_Generates a RNG seed using the Random Number Generator (RNGB)
         * on the Kinetis K53. Documentation located in Chapter 33 of
         * K53 Sub-Family Reference Manual (see note in the README for link).
         */
        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            int i;

            /* turn on RNGB module */
            SIM_SCGC3 |= SIM_SCGC3_RNGB_MASK;

            /* reset RNGB */
            RNG_CMD |= RNG_CMD_SR_MASK;

            /* FIFO generate interrupt, return all zeros on underflow,
             * set auto reseed */
            RNG_CR |= (RNG_CR_FUFMOD_MASK | RNG_CR_AR_MASK);

            /* gen seed, clear interrupts, clear errors */
            RNG_CMD |= (RNG_CMD_GS_MASK | RNG_CMD_CI_MASK | RNG_CMD_CE_MASK);

            /* wait for seeding to complete */
            while ((RNG_SR & RNG_SR_SDN_MASK) == 0) {}

            for (i = 0; i < sz; i++) {

                /* wait for a word to be available from FIFO */
                while((RNG_SR & RNG_SR_FIFO_LVL_MASK) == 0) {}

                /* get value */
                output[i] = RNG_OUT;
            }

            return 0;
        }

    #elif defined(FREESCALE_KSDK_2_0_TRNG)

        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            status_t status;
            status = TRNG_GetRandomData(TRNG0, output, sz);
            if (status == kStatus_Success)
            {
                return(0);
            }
            else
            {
                return RAN_BLOCK_E;
            }
        }

    #elif defined(FREESCALE_KSDK_2_0_RNGA)

        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            status_t status;
            status = RNGA_GetRandomData(RNG, output, sz);
            if (status == kStatus_Success)
            {
                return(0);
            }
            else
            {
                return RAN_BLOCK_E;
            }
        }


    #elif defined(FREESCALE_RNGA)

        int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
        {
            RNGA_DRV_GetRandomData(RNGA_INSTANCE, output, sz);
            return 0;
        }

    #else
        #define USE_TEST_GENSEED
    #endif /* FREESCALE_K70_RNGA */

#elif defined(STM32_RNG)
     /* Generate a RNG seed using the hardware random number generator
      * on the STM32F2/F4/F7. */

    #ifdef WOLFSSL_STM32_CUBEMX
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        RNG_HandleTypeDef hrng;
        int i;
        (void)os;

        /* enable RNG clock source */
        __HAL_RCC_RNG_CLK_ENABLE();

        /* enable RNG peripheral */
        hrng.Instance = RNG;
        HAL_RNG_Init(&hrng);

        for (i = 0; i < (int)sz; i++) {
            /* get value */
            output[i] = (byte)HAL_RNG_GetRandomNumber(&hrng);
        }

        return 0;
    }
    #elif defined(WOLFSSL_STM32F427_RNG)

    /* Generate a RNG seed using the hardware RNG on the STM32F427
     * directly, following steps outlined in STM32F4 Reference
     * Manual (Chapter 24) for STM32F4xx family. */
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int i;
        (void)os;

        /* enable RNG interrupt, set IE bit in RNG->CR register */
        RNG->CR |= RNG_CR_IE;

        /* enable RNG, set RNGEN bit in RNG->CR. Activates RNG,
         * RNG_LFSR, and error detector */
        RNG->CR |= RNG_CR_RNGEN;

        /* verify no errors, make sure SEIS and CEIS bits are 0
         * in RNG->SR register */
        if (RNG->SR & (RNG_SR_SECS | RNG_SR_CECS))
            return RNG_FAILURE_E;

        for (i = 0; i < (int)sz; i++) {
            /* wait until RNG number is ready */
            while ((RNG->SR & RNG_SR_DRDY) == 0) { }

            /* get value */
            output[i] = RNG->DR;
        }

        return 0;
    }

    #else

    /* Generate a RNG seed using the STM32 Standard Peripheral Library */
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int i;
        (void)os;

        /* enable RNG clock source */
        RCC_AHB2PeriphClockCmd(RCC_AHB2Periph_RNG, ENABLE);

        /* reset RNG */
        RNG_DeInit();

        /* enable RNG peripheral */
        RNG_Cmd(ENABLE);

        /* verify no errors with RNG_CLK or Seed */
        if (RNG_GetFlagStatus(RNG_FLAG_SECS | RNG_FLAG_CECS) != RESET)
        	return RNG_FAILURE_E;

        for (i = 0; i < (int)sz; i++) {
            /* wait until RNG number is ready */
            while (RNG_GetFlagStatus(RNG_FLAG_DRDY) == RESET) { }

            /* get value */
            output[i] = RNG_GetRandomNumber();
        }

        return 0;
    }
    #endif /* WOLFSSL_STM32_CUBEMX */

#elif defined(WOLFSSL_TIRTOS)

    #include <xdc/runtime/Timestamp.h>
    #include <stdlib.h>
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int i;
        srand(xdc_runtime_Timestamp_get32());

        for (i = 0; i < sz; i++ ) {
            output[i] = rand() % 256;
            if ((i % 8) == 7) {
                srand(xdc_runtime_Timestamp_get32());
            }
        }

        return 0;
    }

#elif defined(WOLFSSL_PB)

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        word32 i;
        for (i = 0; i < sz; i++)
            output[i] = UTL_Rand();

        (void)os;

        return 0;
    }

#elif defined(WOLFSSL_NUCLEUS)
#include "nucleus.h"
#include "kernel/plus_common.h"

#warning "potential for not enough entropy, currently being used for testing"
int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
{
    int i;
    srand(NU_Get_Time_Stamp());

    for (i = 0; i < sz; i++ ) {
        output[i] = rand() % 256;
        if ((i % 8) == 7) {
            srand(NU_Get_Time_Stamp());
        }
    }

    return 0;
}
#elif defined(WOLFSSL_VXWORKS)

    #include <randomNumGen.h>

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz) {
        STATUS        status;

        #ifdef VXWORKS_SIM
            /* cannot generate true entropy with VxWorks simulator */
            #warning "not enough entropy, simulator for testing only"
            int i = 0;

            for (i = 0; i < 1000; i++) {
                randomAddTimeStamp();
            }
        #endif

        status = randBytes (output, sz);
        if (status == ERROR) {
            return RNG_FAILURE_E;
        }

        return 0;
    }

#elif defined(WOLFSSL_NRF51)
    #include "app_error.h"
    #include "nrf_drv_rng.h"
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int remaining = sz, length, pos = 0;
        uint8_t available;
        uint32_t err_code;

        (void)os;

        /* Make sure RNG is running */
        err_code = nrf_drv_rng_init(NULL);
        if (err_code != NRF_SUCCESS && err_code != NRF_ERROR_INVALID_STATE) {
            return -1;
        }

        while (remaining > 0) {
            err_code = nrf_drv_rng_bytes_available(&available);
            if (err_code == NRF_SUCCESS) {
                length = (remaining < available) ? remaining : available;
                if (length > 0) {
                    err_code = nrf_drv_rng_rand(&output[pos], length);
                    remaining -= length;
                    pos += length;
                }
            }

            if (err_code != NRF_SUCCESS) {
                break;
            }
        }

        return (err_code == NRF_SUCCESS) ? 0 : -1;
    }

#elif defined(HAVE_WNR)

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        if (os == NULL || output == NULL || wnr_ctx == NULL ||
                wnr_timeout < 0) {
            return BAD_FUNC_ARG;
        }

        if (wnr_mutex_init == 0) {
            WOLFSSL_MSG("netRandom context must be created before use");
            return RNG_FAILURE_E;
        }

        if (wc_LockMutex(&wnr_mutex) != 0) {
            WOLFSSL_MSG("Bad Lock Mutex wnr_mutex\n");
            return BAD_MUTEX_E;
        }

        if (wnr_get_entropy(wnr_ctx, wnr_timeout, output, sz, sz) !=
                WNR_ERROR_NONE)
            return RNG_FAILURE_E;

        wc_UnLockMutex(&wnr_mutex);

        return 0;
    }

#elif defined(WOLFSSL_ATMEL)
    #include <wolfssl/wolfcrypt/port/atmel/atmel.h>

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
    	int ret = 0;

        (void)os;
    	if (output == NULL) {
    		return BUFFER_E;
    	}

    	ret = atmel_get_random_number(sz, output);

    	return ret;
    }

#elif defined(INTIME_RTOS)
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int ret = 0;

        (void)os;

        if (output == NULL) {
            return BUFFER_E;
        }

        /* Note: Investigate better solution */
        /* no return to check */
        arc4random_buf(output, sz);

        return ret;
    }

#elif defined(IDIRECT_DEV_RANDOM)

    extern int getRandom( int sz, unsigned char *output );

    int GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int num_bytes_returned = 0;

        num_bytes_returned = getRandom( (int) sz, (unsigned char *) output );

        return 0;
    }

#elif (defined(WOLFSSL_IMX6_CAAM) || defined(WOLFSSL_IMX6_CAAM_RNG))

    #include <wolfssl/wolfcrypt/port/caam/wolfcaam.h>
    #include <wolfssl/wolfcrypt/port/caam/caam_driver.h>

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        Buffer buf[1];
        int ret  = 0;
        int times = 1000, i;

        (void)os;

        if (output == NULL) {
            return BUFFER_E;
        }

        buf[0].BufferType = DataBuffer | LastBuffer;
        buf[0].TheAddress = (Address)output;
        buf[0].Length     = sz;

        /* Check Waiting to make sure entropy is ready */
        for (i = 0; i < times; i++) {
            ret = wc_caamAddAndWait(buf, NULL, CAAM_ENTROPY);
            if (ret == Success) {
                break;
            }

            /* driver could be waiting for entropy */
            if (ret != RAN_BLOCK_E) {
                return ret;
            }
            usleep(100);
        }

        if (i == times && ret != Success) {
             return RNG_FAILURE_E;
        }
        else { /* Success case */
            ret = 0;
        }

        return ret;
    }

#elif defined(WOLFSSL_APACHE_MYNEWT)

    #include <stdlib.h>
    #include "os/os_time.h"
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int i;
        srand(os_time_get());

        for (i = 0; i < sz; i++ ) {
            output[i] = rand() % 256;
            if ((i % 8) == 7) {
                srand(os_time_get());
            }
        }

        return 0;
    }

#elif defined(CUSTOM_RAND_GENERATE_BLOCK)
    /* #define CUSTOM_RAND_GENERATE_BLOCK myRngFunc
     * extern int myRngFunc(byte* output, word32 sz);
     */

#elif defined(WOLFSSL_SAFERTOS) || defined(WOLFSSL_LEANPSK) || \
      defined(WOLFSSL_IAR_ARM)  || defined(WOLFSSL_MDK_ARM) || \
      defined(WOLFSSL_uITRON4)  || defined(WOLFSSL_uTKERNEL2) || \
      defined(WOLFSSL_LPC43xx)  || defined(WOLFSSL_STM32F2xx) || \
      defined(MBED)             || defined(WOLFSSL_EMBOS) || \
      defined(WOLFSSL_GENSEED_FORTEST) || defined(WOLFSSL_CHIBIOS)

    /* these platforms do not have a default random seed and
       you'll need to implement your own wc_GenerateSeed or define via
       CUSTOM_RAND_GENERATE_BLOCK */

    #define USE_TEST_GENSEED

#elif defined(NO_DEV_RANDOM)

    #error "you need to write an os specific wc_GenerateSeed() here"

    /*
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        return 0;
    }
    */

#else

    /* may block */
    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        int ret = 0;

    #ifdef HAVE_INTEL_RDSEED
        if (IS_INTEL_RDSEED(intel_flags)) {
             ret = wc_GenerateSeed_IntelRD(NULL, output, sz);
             if (ret == 0) {
                 /* success, we're done */
                 return ret;
             }
        #ifdef FORCE_FAILURE_RDSEED
             /* don't fallback to /dev/urandom */
             return ret;
        #else
             /* reset error and fallback to using /dev/urandom */
             ret = 0;
        #endif
        }
    #endif /* HAVE_INTEL_RDSEED */

    #ifndef NO_DEV_URANDOM /* way to disable use of /dev/urandom */
        os->fd = open("/dev/urandom", O_RDONLY);
        if (os->fd == -1)
    #endif
        {
            /* may still have /dev/random */
            os->fd = open("/dev/random", O_RDONLY);
            if (os->fd == -1)
                return OPEN_RAN_E;
        }

        while (sz) {
            int len = (int)read(os->fd, output, sz);
            if (len == -1) {
                ret = READ_RAN_E;
                break;
            }

            sz     -= len;
            output += len;

            if (sz) {
    #if defined(BLOCKING) || defined(WC_RNG_BLOCKING)
                sleep(0);             /* context switch */
    #else
                ret = RAN_BLOCK_E;
                break;
    #endif
            }
        }
        close(os->fd);

        return ret;
    }

#endif

#ifdef USE_TEST_GENSEED
    #ifndef _MSC_VER
        #warning "write a real random seed!!!!, just for testing now"
    #else
        #pragma message("Warning: write a real random seed!!!!, just for testing now")
    #endif

    int wc_GenerateSeed(OS_Seed* os, byte* output, word32 sz)
    {
        word32 i;
        for (i = 0; i < sz; i++ )
            output[i] = i;

        (void)os;

        return 0;
    }
#endif

/* End wc_GenerateSeed */

#endif /* WC_NO_RNG */
#endif /* HAVE_FIPS */