/* kdf.c

 *

 * Copyright (C) 2006-2022 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/wc_port.h>

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

#include <wolfssl/wolfcrypt/logging.h>

#ifndef NO_KDF

#if defined(HAVE_FIPS) && \

    defined(HAVE_FIPS_VERSION) && (HAVE_FIPS_VERSION >= 5)

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

    #define FIPS_NO_WRAPPERS

    #ifdef USE_WINDOWS_API

        #pragma code_seg(".fipsA$m")

        #pragma const_seg(".fipsB$m")

    #endif

#endif

#ifdef NO_INLINE

    #include <wolfssl/wolfcrypt/misc.h>

#else

    #define WOLFSSL_MISC_INCLUDED

    #include <wolfcrypt/src/misc.c>

#endif

#include <wolfssl/wolfcrypt/hmac.h>

#include <wolfssl/wolfcrypt/kdf.h>

#ifdef WOLFSSL_HAVE_PRF

#ifdef WOLFSSL_SHA512

    #define P_HASH_MAX_SIZE WC_SHA512_DIGEST_SIZE

#elif defined(WOLFSSL_SHA384)

    #define P_HASH_MAX_SIZE WC_SHA384_DIGEST_SIZE

#else

    #define P_HASH_MAX_SIZE WC_SHA256_DIGEST_SIZE

#endif

/* Pseudo Random Function for MD5, SHA-1, SHA-256, SHA-384, or SHA-512 */

int wc_PRF(byte* result, word32 resLen, const byte* secret,

                  word32 secLen, const byte* seed, word32 seedLen, int hash,

                  void* heap, int devId)

{

    word32 len = P_HASH_MAX_SIZE;

    word32 times;

    word32 lastLen;

    word32 lastTime;

    word32 i;

    word32 idx = 0;

    int    ret = 0;

#ifdef WOLFSSL_SMALL_STACK

    byte*  previous;

    byte*  current;

    Hmac*  hmac;

#else

    byte   previous[P_HASH_MAX_SIZE];  /* max size */

    byte   current[P_HASH_MAX_SIZE];   /* max size */

    Hmac   hmac[1];

#endif

#ifdef WOLFSSL_SMALL_STACK

    previous = (byte*)XMALLOC(P_HASH_MAX_SIZE, heap, DYNAMIC_TYPE_DIGEST);

    current  = (byte*)XMALLOC(P_HASH_MAX_SIZE, heap, DYNAMIC_TYPE_DIGEST);

    hmac     = (Hmac*)XMALLOC(sizeof(Hmac),    heap, DYNAMIC_TYPE_HMAC);

    if (previous == NULL || current == NULL || hmac == NULL) {

        if (previous) XFREE(previous, heap, DYNAMIC_TYPE_DIGEST);

        if (current)  XFREE(current,  heap, DYNAMIC_TYPE_DIGEST);

        if (hmac)     XFREE(hmac,     heap, DYNAMIC_TYPE_HMAC);

        return MEMORY_E;

    }

#endif

#ifdef WOLFSSL_CHECK_MEM_ZERO

    wc_MemZero_Add("wc_PRF previous", previous, P_HASH_MAX_SIZE);

    wc_MemZero_Add("wc_PRF current", current, P_HASH_MAX_SIZE);

    wc_MemZero_Add("wc_PRF hmac", hmac, sizeof(Hmac));

#endif

    switch (hash) {

    #ifndef NO_MD5

        case md5_mac:

            hash = WC_MD5;

            len  = WC_MD5_DIGEST_SIZE;

        break;

    #endif

    #ifndef NO_SHA256

        case sha256_mac:

            hash = WC_SHA256;

            len  = WC_SHA256_DIGEST_SIZE;

        break;

    #endif

    #ifdef WOLFSSL_SHA384

        case sha384_mac:

            hash = WC_SHA384;

            len  = WC_SHA384_DIGEST_SIZE;

        break;

    #endif

    #ifdef WOLFSSL_SHA512

        case sha512_mac:

            hash = WC_SHA512;

            len  = WC_SHA512_DIGEST_SIZE;

        break;

    #endif

    #ifndef NO_SHA

        case sha_mac:

            hash = WC_SHA;

            len  = WC_SHA_DIGEST_SIZE;

        break;

    #endif

        default:

        #ifdef WOLFSSL_SMALL_STACK

            if (previous) XFREE(previous, heap, DYNAMIC_TYPE_DIGEST);

            if (current)  XFREE(current,  heap, DYNAMIC_TYPE_DIGEST);

            if (hmac)     XFREE(hmac,     heap, DYNAMIC_TYPE_HMAC);

        #endif

            return HASH_TYPE_E;

    }

    times   = resLen / len;

    lastLen = resLen % len;

    if (lastLen)

        times += 1;

    /* times == 0 iif resLen == 0, but times == 0 abides clang static analyzer

       while resLen == 0 doesn't */

    if (times == 0)

        return BAD_FUNC_ARG;

    lastTime = times - 1;

    ret = wc_HmacInit(hmac, heap, devId);

    if (ret == 0) {

        ret = wc_HmacSetKey(hmac, hash, secret, secLen);

        if (ret == 0)

            ret = wc_HmacUpdate(hmac, seed, seedLen); /* A0 = seed */

        if (ret == 0)

            ret = wc_HmacFinal(hmac, previous);       /* A1 */

        if (ret == 0) {

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

                ret = wc_HmacUpdate(hmac, previous, len);

                if (ret != 0)

                    break;

                ret = wc_HmacUpdate(hmac, seed, seedLen);

                if (ret != 0)

                    break;

                ret = wc_HmacFinal(hmac, current);

                if (ret != 0)

                    break;

                if ((i == lastTime) && lastLen)

                    XMEMCPY(&result[idx], current,

                                             min(lastLen, P_HASH_MAX_SIZE));

                else {

                    XMEMCPY(&result[idx], current, len);

                    idx += len;

                    ret = wc_HmacUpdate(hmac, previous, len);

                    if (ret != 0)

                        break;

                    ret = wc_HmacFinal(hmac, previous);

                    if (ret != 0)

                        break;

                }

            }

        }

        wc_HmacFree(hmac);

    }

    ForceZero(previous,  P_HASH_MAX_SIZE);

    ForceZero(current,   P_HASH_MAX_SIZE);

    ForceZero(hmac,      sizeof(Hmac));

#ifdef WOLFSSL_SMALL_STACK

    XFREE(previous, heap, DYNAMIC_TYPE_DIGEST);

    XFREE(current,  heap, DYNAMIC_TYPE_DIGEST);

    XFREE(hmac,     heap, DYNAMIC_TYPE_HMAC);

#elif defined(WOLFSSL_CHECK_MEM_ZERO)

    wc_MemZero_Check(previous, P_HASH_MAX_SIZE);

    wc_MemZero_Check(current,  P_HASH_MAX_SIZE);

    wc_MemZero_Check(hmac,     sizeof(Hmac));

#endif

    return ret;

}

#undef P_HASH_MAX_SIZE

/* compute PRF (pseudo random function) using SHA1 and MD5 for TLSv1 */

int wc_PRF_TLSv1(byte* digest, word32 digLen, const byte* secret,

           word32 secLen, const byte* label, word32 labLen,

           const byte* seed, word32 seedLen, void* heap, int devId)

{

    int         ret  = 0;

    word32      half = (secLen + 1) / 2;

    const byte* md5_half;

    const byte* sha_half;

    byte*      md5_result;

#ifdef WOLFSSL_SMALL_STACK

    byte*      sha_result;

#else

    byte       sha_result[MAX_PRF_DIG];    /* digLen is real size */

#endif

#if !defined(WOLFSSL_ASYNC_CRYPT) || defined(WC_ASYNC_NO_HASH)

    byte       labelSeed[MAX_PRF_LABSEED];

#else

    WC_DECLARE_VAR(labelSeed, byte, MAX_PRF_LABSEED, heap);

    if (labelSeed == NULL)

        return MEMORY_E;

#endif

    if (half > MAX_PRF_HALF ||

        labLen + seedLen > MAX_PRF_LABSEED ||

        digLen > MAX_PRF_DIG)

    {

    #if defined(WOLFSSL_ASYNC_CRYPT) && !defined(WC_ASYNC_NO_HASH)

        WC_FREE_VAR(labelSeed, heap);

    #endif

        return BUFFER_E;

    }

#ifdef WOLFSSL_SMALL_STACK

    sha_result = (byte*)XMALLOC(MAX_PRF_DIG, heap, DYNAMIC_TYPE_DIGEST);

    if (sha_result == NULL) {

    #if defined(WOLFSSL_ASYNC_CRYPT) && !defined(WC_ASYNC_NO_HASH)

        WC_FREE_VAR(labelSeed, heap);

    #endif

        return MEMORY_E;

    }

#endif

    md5_half = secret;

    sha_half = secret + half - secLen % 2;

    md5_result = digest;

    XMEMCPY(labelSeed, label, labLen);

    XMEMCPY(labelSeed + labLen, seed, seedLen);

    if ((ret = wc_PRF(md5_result, digLen, md5_half, half, labelSeed,

                                labLen + seedLen, md5_mac, heap, devId)) == 0) {

        if ((ret = wc_PRF(sha_result, digLen, sha_half, half, labelSeed,

                                labLen + seedLen, sha_mac, heap, devId)) == 0) {

        #ifdef WOLFSSL_CHECK_MEM_ZERO

            wc_MemZero_Add("wc_PRF_TLSv1 sha_result", sha_result, digLen);

        #endif

            /* calculate XOR for TLSv1 PRF */

            /* md5 result is placed directly in digest */

            xorbuf(digest, sha_result, digLen);

            ForceZero(sha_result, digLen);

        }

    }

#ifdef WOLFSSL_SMALL_STACK

    XFREE(sha_result, heap, DYNAMIC_TYPE_DIGEST);

#elif defined(WOLFSSL_CHECK_MEM_ZERO)

    wc_MemZero_Check(sha_result, MAX_PRF_DIG);

#endif

#if defined(WOLFSSL_ASYNC_CRYPT) && !defined(WC_ASYNC_NO_HASH)

    WC_FREE_VAR(labelSeed, heap);

#endif

    return ret;

}

/* Wrapper for TLS 1.2 and TLSv1 cases to calculate PRF */

/* In TLS 1.2 case call straight thru to wc_PRF */

int wc_PRF_TLS(byte* digest, word32 digLen, const byte* secret, word32 secLen,

            const byte* label, word32 labLen, const byte* seed, word32 seedLen,

            int useAtLeastSha256, int hash_type, void* heap, int devId)

{

    int ret = 0;

    if (useAtLeastSha256) {

    #if defined(WOLFSSL_ASYNC_CRYPT) && !defined(WC_ASYNC_NO_HASH)

        WC_DECLARE_VAR(labelSeed, byte, MAX_PRF_LABSEED, heap);

        if (labelSeed == NULL)

            return MEMORY_E;

    #else

        byte labelSeed[MAX_PRF_LABSEED];

    #endif

        if (labLen + seedLen > MAX_PRF_LABSEED)

            return BUFFER_E;

        XMEMCPY(labelSeed, label, labLen);

        XMEMCPY(labelSeed + labLen, seed, seedLen);

        /* If a cipher suite wants an algorithm better than sha256, it

         * should use better. */

        if (hash_type < sha256_mac || hash_type == blake2b_mac)

            hash_type = sha256_mac;

        /* compute PRF for MD5, SHA-1, SHA-256, or SHA-384 for TLSv1.2 PRF */

        ret = wc_PRF(digest, digLen, secret, secLen, labelSeed,

                     labLen + seedLen, hash_type, heap, devId);

    #if defined(WOLFSSL_ASYNC_CRYPT) && !defined(WC_ASYNC_NO_HASH)

        WC_FREE_VAR(labelSeed, heap);

    #endif

    }

    else {

#ifndef NO_OLD_TLS

        /* compute TLSv1 PRF (pseudo random function using HMAC) */

        ret = wc_PRF_TLSv1(digest, digLen, secret, secLen, label, labLen, seed,

                          seedLen, heap, devId);

#else

        ret = BAD_FUNC_ARG;

#endif

    }

    return ret;

}

#endif /* WOLFSSL_HAVE_PRF */

#if defined(HAVE_HKDF) && !defined(NO_HMAC)

    /* Extract data using HMAC, salt and input.

     * RFC 5869 - HMAC-based Extract-and-Expand Key Derivation Function (HKDF)

     *

     * prk      The generated pseudorandom key.

     * salt     The salt.

     * saltLen  The length of the salt.

     * ikm      The input keying material.

     * ikmLen   The length of the input keying material.

     * digest   The type of digest to use.

     * returns 0 on success, otherwise failure.

     */

    int wc_Tls13_HKDF_Extract(byte* prk, const byte* salt, int saltLen,

                                 byte* ikm, int ikmLen, int digest)

    {

        int ret;

        int len = 0;

        switch (digest) {

            #ifndef NO_SHA256

            case WC_SHA256:

                len = WC_SHA256_DIGEST_SIZE;

                break;

            #endif

            #ifdef WOLFSSL_SHA384

            case WC_SHA384:

                len = WC_SHA384_DIGEST_SIZE;

                break;

            #endif

            #ifdef WOLFSSL_TLS13_SHA512

            case WC_SHA512:

                len = WC_SHA512_DIGEST_SIZE;

                break;

            #endif

            default:

                return BAD_FUNC_ARG;

        }

        /* When length is 0 then use zeroed data of digest length. */

        if (ikmLen == 0) {

            ikmLen = len;

            XMEMSET(ikm, 0, len);

        }

#ifdef WOLFSSL_DEBUG_TLS

        WOLFSSL_MSG("  Salt");

        WOLFSSL_BUFFER(salt, saltLen);

        WOLFSSL_MSG("  IKM");

        WOLFSSL_BUFFER(ikm, ikmLen);

#endif

        ret = wc_HKDF_Extract(digest, salt, saltLen, ikm, ikmLen, prk);

#ifdef WOLFSSL_DEBUG_TLS

        WOLFSSL_MSG("  PRK");

        WOLFSSL_BUFFER(prk, len);

#endif

        return ret;

    }

    /* Expand data using HMAC, salt and label and info.

     * TLS v1.3 defines this function.

     *

     * okm          The generated pseudorandom key - output key material.

     * okmLen       The length of generated pseudorandom key -

     *              output key material.

     * prk          The salt - pseudo-random key.

     * prkLen       The length of the salt - pseudo-random key.

     * protocol     The TLS protocol label.

     * protocolLen  The length of the TLS protocol label.

     * info         The information to expand.

     * infoLen      The length of the information.

     * digest       The type of digest to use.

     * returns 0 on success, otherwise failure.

     */

    int wc_Tls13_HKDF_Expand_Label(byte* okm, word32 okmLen,

                                 const byte* prk, word32 prkLen,

                                 const byte* protocol, word32 protocolLen,

                                 const byte* label, word32 labelLen,

                                 const byte* info, word32 infoLen,

                                 int digest)

    {

        int    ret = 0;

        int    idx = 0;

        byte   data[MAX_TLS13_HKDF_LABEL_SZ];

        /* Output length. */

        data[idx++] = (byte)(okmLen >> 8);

        data[idx++] = (byte)okmLen;

        /* Length of protocol | label. */

        data[idx++] = (byte)(protocolLen + labelLen);

        /* Protocol */

        XMEMCPY(&data[idx], protocol, protocolLen);

        idx += protocolLen;

        /* Label */

        XMEMCPY(&data[idx], label, labelLen);

        idx += labelLen;

        /* Length of hash of messages */

        data[idx++] = (byte)infoLen;

        /* Hash of messages */

        XMEMCPY(&data[idx], info, infoLen);

        idx += infoLen;

    #ifdef WOLFSSL_CHECK_MEM_ZERO

        wc_MemZero_Add("wc_Tls13_HKDF_Expand_Label data", data, idx);

    #endif

#ifdef WOLFSSL_DEBUG_TLS

        WOLFSSL_MSG("  PRK");

        WOLFSSL_BUFFER(prk, prkLen);

        WOLFSSL_MSG("  Info");

        WOLFSSL_BUFFER(data, idx);

        WOLFSSL_MSG_EX("  Digest %d", digest);

#endif

        ret = wc_HKDF_Expand(digest, prk, prkLen, data, idx, okm, okmLen);

#ifdef WOLFSSL_DEBUG_TLS

        WOLFSSL_MSG("  OKM");

        WOLFSSL_BUFFER(okm, okmLen);

#endif

        ForceZero(data, idx);

    #ifdef WOLFSSL_CHECK_MEM_ZERO

        wc_MemZero_Check(data, MAX_TLS13_HKDF_LABEL_SZ);

    #endif

        return ret;

    }

#endif /* HAVE_HKDF && !NO_HMAC */

#ifdef WOLFSSL_WOLFSSH

/* hash union */

typedef union {

#ifndef NO_MD5

    wc_Md5 md5;

#endif

#ifndef NO_SHA

    wc_Sha sha;

#endif

#ifdef WOLFSSL_SHA224

    wc_Sha224 sha224;

#endif

#ifndef NO_SHA256

    wc_Sha256 sha256;

#endif

#ifdef WOLFSSL_SHA384

    wc_Sha384 sha384;

#endif

#ifdef WOLFSSL_SHA512

    wc_Sha512 sha512;

#endif

#ifdef WOLFSSL_SHA3

    wc_Sha3 sha3;

#endif

} _hash;

static

int _HashInit(byte hashId, _hash* hash)

{

    int ret = BAD_FUNC_ARG;

    switch (hashId) {

    #ifndef NO_SHA

        case WC_SHA:

            ret = wc_InitSha(&hash->sha);

            break;

    #endif /* !NO_SHA */

    #ifndef NO_SHA256

        case WC_SHA256:

            ret = wc_InitSha256(&hash->sha256);

            break;

    #endif /* !NO_SHA256 */

    #ifdef WOLFSSL_SHA384

        case WC_SHA384:

            ret = wc_InitSha384(&hash->sha384);

            break;

    #endif /* WOLFSSL_SHA384 */

    #ifdef WOLFSSL_SHA512

        case WC_SHA512:

            ret = wc_InitSha512(&hash->sha512);

            break;

    #endif /* WOLFSSL_SHA512 */

    }

    return ret;

}

static

int _HashUpdate(byte hashId, _hash* hash,

        const byte* data, word32 dataSz)

{

    int ret = BAD_FUNC_ARG;

    switch (hashId) {

    #ifndef NO_SHA

        case WC_SHA:

            ret = wc_ShaUpdate(&hash->sha, data, dataSz);

            break;

    #endif /* !NO_SHA */

    #ifndef NO_SHA256

        case WC_SHA256:

            ret = wc_Sha256Update(&hash->sha256, data, dataSz);

            break;

    #endif /* !NO_SHA256 */

    #ifdef WOLFSSL_SHA384

        case WC_SHA384:

            ret = wc_Sha384Update(&hash->sha384, data, dataSz);

            break;

    #endif /* WOLFSSL_SHA384 */

    #ifdef WOLFSSL_SHA512

        case WC_SHA512:

            ret = wc_Sha512Update(&hash->sha512, data, dataSz);

            break;

    #endif /* WOLFSSL_SHA512 */

    }

    return ret;

}

static

int _HashFinal(byte hashId, _hash* hash, byte* digest)

{

    int ret = BAD_FUNC_ARG;

    switch (hashId) {

    #ifndef NO_SHA

        case WC_SHA:

            ret = wc_ShaFinal(&hash->sha, digest);

            break;

    #endif /* !NO_SHA */

    #ifndef NO_SHA256

        case WC_SHA256:

            ret = wc_Sha256Final(&hash->sha256, digest);

            break;

    #endif /* !NO_SHA256 */

    #ifdef WOLFSSL_SHA384

        case WC_SHA384:

            ret = wc_Sha384Final(&hash->sha384, digest);

            break;

    #endif /* WOLFSSL_SHA384 */

    #ifdef WOLFSSL_SHA512

        case WC_SHA512:

            ret = wc_Sha512Final(&hash->sha512, digest);

            break;

    #endif /* WOLFSSL_SHA512 */

    }

    return ret;

}

static

void _HashFree(byte hashId, _hash* hash)

{

    switch (hashId) {

    #ifndef NO_SHA

        case WC_SHA:

            wc_ShaFree(&hash->sha);

            break;

    #endif /* !NO_SHA */

    #ifndef NO_SHA256

        case WC_SHA256:

            wc_Sha256Free(&hash->sha256);

            break;

    #endif /* !NO_SHA256 */

    #ifdef WOLFSSL_SHA384

        case WC_SHA384:

            wc_Sha384Free(&hash->sha384);

            break;

    #endif /* WOLFSSL_SHA384 */

    #ifdef WOLFSSL_SHA512

        case WC_SHA512:

            wc_Sha512Free(&hash->sha512);

            break;

    #endif /* WOLFSSL_SHA512 */

    }

}

#define LENGTH_SZ 4

int wc_SSH_KDF(byte hashId, byte keyId, byte* key, word32 keySz,

        const byte* k, word32 kSz, const byte* h, word32 hSz,

        const byte* sessionId, word32 sessionIdSz)

{

    word32 blocks, remainder;

    _hash hash;

    enum wc_HashType enmhashId = (enum wc_HashType)hashId;

    byte kPad = 0;

    byte pad = 0;

    byte kSzFlat[LENGTH_SZ];

    int digestSz;

    int ret;

    if (key == NULL || keySz == 0 ||

        k == NULL || kSz == 0 ||

        h == NULL || hSz == 0 ||

        sessionId == NULL || sessionIdSz == 0) {

        return BAD_FUNC_ARG;

    }

    digestSz = wc_HmacSizeByType(enmhashId);

    if (digestSz < 0) {

        return BAD_FUNC_ARG;

    }

    if (k[0] & 0x80) kPad = 1;

    c32toa(kSz + kPad, kSzFlat);

    blocks = keySz / digestSz;

    remainder = keySz % digestSz;

    ret = _HashInit(enmhashId, &hash);

    if (ret == 0)

        ret = _HashUpdate(enmhashId, &hash, kSzFlat, LENGTH_SZ);

    if (ret == 0 && kPad)

        ret = _HashUpdate(enmhashId, &hash, &pad, 1);

    if (ret == 0)

        ret = _HashUpdate(enmhashId, &hash, k, kSz);

    if (ret == 0)

        ret = _HashUpdate(enmhashId, &hash, h, hSz);

    if (ret == 0)

        ret = _HashUpdate(enmhashId, &hash, &keyId, sizeof(keyId));

    if (ret == 0)

        ret = _HashUpdate(enmhashId, &hash, sessionId, sessionIdSz);

    if (ret == 0) {

        if (blocks == 0) {

            if (remainder > 0) {

                byte lastBlock[WC_MAX_DIGEST_SIZE];

                ret = _HashFinal(enmhashId, &hash, lastBlock);

                if (ret == 0)

                    XMEMCPY(key, lastBlock, remainder);

            }

        }

        else {

            word32 runningKeySz, curBlock;

            runningKeySz = digestSz;

            ret = _HashFinal(enmhashId, &hash, key);

            for (curBlock = 1; curBlock < blocks; curBlock++) {

                ret = _HashInit(enmhashId, &hash);

                if (ret != 0) break;

                ret = _HashUpdate(enmhashId, &hash, kSzFlat, LENGTH_SZ);

                if (ret != 0) break;

                if (kPad)

                    ret = _HashUpdate(enmhashId, &hash, &pad, 1);

                if (ret != 0) break;

                ret = _HashUpdate(enmhashId, &hash, k, kSz);

                if (ret != 0) break;

                ret = _HashUpdate(enmhashId, &hash, h, hSz);

                if (ret != 0) break;

                ret = _HashUpdate(enmhashId, &hash, key, runningKeySz);

                if (ret != 0) break;

                ret = _HashFinal(enmhashId, &hash, key + runningKeySz);

                if (ret != 0) break;

                runningKeySz += digestSz;

            }

            if (remainder > 0) {

                byte lastBlock[WC_MAX_DIGEST_SIZE];

                if (ret == 0)

                    ret = _HashInit(enmhashId, &hash);

                if (ret == 0)

                    ret = _HashUpdate(enmhashId, &hash, kSzFlat, LENGTH_SZ);

                if (ret == 0 && kPad)

                    ret = _HashUpdate(enmhashId, &hash, &pad, 1);

                if (ret == 0)

                    ret = _HashUpdate(enmhashId, &hash, k, kSz);

                if (ret == 0)

                    ret = _HashUpdate(enmhashId, &hash, h, hSz);

                if (ret == 0)

                    ret = _HashUpdate(enmhashId, &hash, key, runningKeySz);

                if (ret == 0)

                    ret = _HashFinal(enmhashId, &hash, lastBlock);

                if (ret == 0)

                    XMEMCPY(key + runningKeySz, lastBlock, remainder);

            }

        }

    }

    _HashFree(enmhashId, &hash);

    return ret;

}

#endif /* WOLFSSL_WOLFSSH */

#endif /* NO_KDF */