/* chacha.c

 *

 * Copyright (C) 2006-2025 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 3 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

 */

/*

DESCRIPTION

This library contains implementation for the ChaCha20 stream cipher.

Based from chacha-ref.c version 20080118

D. J. Bernstein

Public domain.

*/

#include <wolfssl/wolfcrypt/libwolfssl_sources.h>

#ifdef HAVE_CHACHA

    #include <wolfssl/wolfcrypt/chacha.h>

    #ifdef NO_INLINE

        #include <wolfssl/wolfcrypt/misc.h>

    #else

        #define WOLFSSL_MISC_INCLUDED

        #include <wolfcrypt/src/misc.c>

    #endif

    #ifdef BIG_ENDIAN_ORDER

        #define LITTLE32(x) ByteReverseWord32(x)

    #else

        #define LITTLE32(x) (x)

    #endif

    /* Number of rounds */

    #define ROUNDS  20

    #define U32C(v) (v##U)

    #define U32V(v) ((word32)(v) & U32C(0xFFFFFFFF))

    #define U8TO32_LITTLE(p) LITTLE32(((word32*)(p))[0])

    #define ROTATE(v,c) rotlFixed(v, c)

    #define XOR(v,w)    ((v) ^ (w))

    #define PLUS(v,w)   (U32V((v) + (w)))

    #define PLUSONE(v)  (PLUS((v),1))

    #define QUARTERROUND(a,b,c,d) \

        x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]),16); \

        x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]),12); \

        x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]), 8); \

        x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]), 7);

#endif /* HAVE_CHACHA */

#if defined(WOLFSSL_ARMASM) && !defined(NO_CHACHA_ASM)

    /* implementation is located in wolfcrypt/src/port/arm/armv8-chacha.c */

#elif defined(WOLFSSL_RISCV_ASM) && !defined(NO_CHACHA_ASM)

    /* implementation located in wolfcrypt/src/port/riscv/riscv-64-chacha.c */

#else

/* BEGIN ChaCha C implementation */

#if defined(HAVE_CHACHA)

#include <wolfssl/wolfcrypt/cpuid.h>

#ifdef CHACHA_AEAD_TEST

    #include <stdio.h>

#endif

#ifdef USE_INTEL_CHACHA_SPEEDUP

    #include <emmintrin.h>

    #include <immintrin.h>

    #if defined(__GNUC__) && ((__GNUC__ < 4) || \

                              (__GNUC__ == 4 && __GNUC_MINOR__ <= 8))

        #undef  NO_AVX2_SUPPORT

        #define NO_AVX2_SUPPORT

    #endif

    #if defined(__clang__) && ((__clang_major__ < 3) || \

                               (__clang_major__ == 3 && __clang_minor__ <= 5))

        #undef  NO_AVX2_SUPPORT

        #define NO_AVX2_SUPPORT

    #elif defined(__clang__) && defined(NO_AVX2_SUPPORT)

        #undef NO_AVX2_SUPPORT

    #endif

    #if defined(_MSC_VER) && (_MSC_VER <= 1900)

        #undef  NO_AVX2_SUPPORT

        #define NO_AVX2_SUPPORT

    #endif

    #ifndef NO_AVX2_SUPPORT

        #define HAVE_INTEL_AVX2

    #endif

    static int cpuidFlagsSet = 0;

    static word32 cpuidFlags = 0;

#endif

/**

  * Set up iv(nonce). Earlier versions used 64 bits instead of 96, this version

  * uses the typical AEAD 96 bit nonce and can do record sizes of 256 GB.

  */

int wc_Chacha_SetIV(ChaCha* ctx, const byte* inIv, word32 counter)

{

    word32 temp[CHACHA_IV_WORDS];/* used for alignment of memory */

    if (ctx == NULL || inIv == NULL)

        return BAD_FUNC_ARG;

    XMEMCPY(temp, inIv, CHACHA_IV_BYTES);

    ctx->left = 0; /* resets state */

    ctx->X[CHACHA_MATRIX_CNT_IV+0] = counter;           /* block counter */

    ctx->X[CHACHA_MATRIX_CNT_IV+1] = LITTLE32(temp[0]); /* fixed variable from nonce */

    ctx->X[CHACHA_MATRIX_CNT_IV+2] = LITTLE32(temp[1]); /* counter from nonce */

    ctx->X[CHACHA_MATRIX_CNT_IV+3] = LITTLE32(temp[2]); /* counter from nonce */

    return 0;

}

/* "expand 32-byte k" as unsigned 32 byte */

static const word32 sigma[4] = {0x61707865, 0x3320646e, 0x79622d32, 0x6b206574};

/* "expand 16-byte k" as unsigned 16 byte */

static const word32 tau[4] = {0x61707865, 0x3120646e, 0x79622d36, 0x6b206574};

/**

  * Key setup. 8 word iv (nonce)

  */

int wc_Chacha_SetKey(ChaCha* ctx, const byte* key, word32 keySz)

{

    const word32* constants;

    const byte*   k;

#ifdef XSTREAM_ALIGN

    word32 alignKey[8];

#endif

    if (ctx == NULL || key == NULL)

        return BAD_FUNC_ARG;

    if (keySz != (CHACHA_MAX_KEY_SZ/2) && keySz != CHACHA_MAX_KEY_SZ)

        return BAD_FUNC_ARG;

#ifdef XSTREAM_ALIGN

    if ((wc_ptr_t)key % 4) {

        WOLFSSL_MSG("wc_ChachaSetKey unaligned key");

        XMEMCPY(alignKey, key, keySz);

        k = (byte*)alignKey;

    }

    else {

        k = key;

    }

#else

    k = key;

#endif /* XSTREAM_ALIGN */

#ifdef CHACHA_AEAD_TEST

    word32 i;

    printf("ChaCha key used :\n");

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

        printf("%02x", key[i]);

        if ((i + 1) % 8 == 0)

           printf("\n");

    }

    printf("\n\n");

#endif

    ctx->X[4] = U8TO32_LITTLE(k +  0);

    ctx->X[5] = U8TO32_LITTLE(k +  4);

    ctx->X[6] = U8TO32_LITTLE(k +  8);

    ctx->X[7] = U8TO32_LITTLE(k + 12);

    if (keySz == CHACHA_MAX_KEY_SZ) {

        k += 16;

        constants = sigma;

    }

    else {

        constants = tau;

    }

    ctx->X[ 8] = U8TO32_LITTLE(k +  0);

    ctx->X[ 9] = U8TO32_LITTLE(k +  4);

    ctx->X[10] = U8TO32_LITTLE(k +  8);

    ctx->X[11] = U8TO32_LITTLE(k + 12);

    ctx->X[ 0] = constants[0];

    ctx->X[ 1] = constants[1];

    ctx->X[ 2] = constants[2];

    ctx->X[ 3] = constants[3];

    ctx->left = 0; /* resets state */

    return 0;

}

#ifndef USE_INTEL_CHACHA_SPEEDUP

/**

  * Converts word into bytes with rotations having been done.

  */

static WC_INLINE void wc_Chacha_wordtobyte(word32 x[CHACHA_CHUNK_WORDS],

        word32 state[CHACHA_CHUNK_WORDS])

{

    word32 i;

    XMEMCPY(x, state, CHACHA_CHUNK_BYTES);

    for (i = (ROUNDS); i > 0; i -= 2) {

        QUARTERROUND(0, 4,  8, 12)

        QUARTERROUND(1, 5,  9, 13)

        QUARTERROUND(2, 6, 10, 14)

        QUARTERROUND(3, 7, 11, 15)

        QUARTERROUND(0, 5, 10, 15)

        QUARTERROUND(1, 6, 11, 12)

        QUARTERROUND(2, 7,  8, 13)

        QUARTERROUND(3, 4,  9, 14)

    }

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

        x[i] = PLUS(x[i], state[i]);

#ifdef BIG_ENDIAN_ORDER

        x[i] = LITTLE32(x[i]);

#endif

    }

}

#endif /* !USE_INTEL_CHACHA_SPEEDUP */

#ifdef __cplusplus

    extern "C" {

#endif

extern void chacha_encrypt_x64(ChaCha* ctx, const byte* m, byte* c,

                               word32 bytes);

extern void chacha_encrypt_avx1(ChaCha* ctx, const byte* m, byte* c,

                                word32 bytes);

extern void chacha_encrypt_avx2(ChaCha* ctx, const byte* m, byte* c,

                                word32 bytes);

#ifdef __cplusplus

    }  /* extern "C" */

#endif

#ifndef USE_INTEL_CHACHA_SPEEDUP

/**

  * Encrypt a stream of bytes

  */

static void wc_Chacha_encrypt_bytes(ChaCha* ctx, const byte* m, byte* c,

                                    word32 bytes)

{

    union {

        byte state[CHACHA_CHUNK_BYTES];

        word32 state32[CHACHA_CHUNK_WORDS];

        wolfssl_word align_word; /* align for xorbufout */

    } tmp;

    /* handle left overs */

    if (bytes > 0 && ctx->left > 0) {

        word32 processed = min(bytes, ctx->left);

        wc_Chacha_wordtobyte(tmp.state32, ctx->X); /* recreate the stream */

        xorbufout(c, m, tmp.state + CHACHA_CHUNK_BYTES - ctx->left, processed);

        ctx->left -= processed;

        /* Used up all of the stream that was left, increment the counter */

        if (ctx->left == 0) {

            ctx->X[CHACHA_MATRIX_CNT_IV] =

                                          PLUSONE(ctx->X[CHACHA_MATRIX_CNT_IV]);

        }

        bytes -= processed;

        c += processed;

        m += processed;

    }

    while (bytes >= CHACHA_CHUNK_BYTES) {

        wc_Chacha_wordtobyte(tmp.state32, ctx->X);

        ctx->X[CHACHA_MATRIX_CNT_IV] = PLUSONE(ctx->X[CHACHA_MATRIX_CNT_IV]);

        xorbufout(c, m, tmp.state, CHACHA_CHUNK_BYTES);

        bytes -= CHACHA_CHUNK_BYTES;

        c += CHACHA_CHUNK_BYTES;

        m += CHACHA_CHUNK_BYTES;

    }

    if (bytes) {

        /* in this case there will always be some left over since bytes is less

         * than CHACHA_CHUNK_BYTES, so do not increment counter after getting

         * stream in order for the stream to be recreated on next call */

        wc_Chacha_wordtobyte(tmp.state32, ctx->X);

        xorbufout(c, m, tmp.state, bytes);

        ctx->left = CHACHA_CHUNK_BYTES - bytes;

    }

}

#endif /* !USE_INTEL_CHACHA_SPEEDUP */

/**

  * API to encrypt/decrypt a message of any size.

  */

int wc_Chacha_Process(ChaCha* ctx, byte* output, const byte* input,

                      word32 msglen)

{

    if (ctx == NULL || input == NULL || output == NULL)

        return BAD_FUNC_ARG;

#ifdef USE_INTEL_CHACHA_SPEEDUP

    /* handle left overs */

    if (msglen > 0 && ctx->left > 0) {

        byte*  out;

        word32 processed = min(msglen, ctx->left);

        out = (byte*)ctx->over + CHACHA_CHUNK_BYTES - ctx->left;

        xorbufout(output, input, out, processed);

        ctx->left -= processed;

        msglen -= processed;

        output += processed;

        input += processed;

    }

    if (msglen == 0) {

        return 0;

    }

    if (!cpuidFlagsSet) {

        cpuidFlags = cpuid_get_flags();

        cpuidFlagsSet = 1;

    }

    #ifdef HAVE_INTEL_AVX2

    if (IS_INTEL_AVX2(cpuidFlags)) {

        SAVE_VECTOR_REGISTERS(return _svr_ret;);

        chacha_encrypt_avx2(ctx, input, output, msglen);

        RESTORE_VECTOR_REGISTERS();

        return 0;

    }

    #endif

    if (IS_INTEL_AVX1(cpuidFlags)) {

        SAVE_VECTOR_REGISTERS(return _svr_ret;);

        chacha_encrypt_avx1(ctx, input, output, msglen);

        RESTORE_VECTOR_REGISTERS();

        return 0;

    }

    else {

        chacha_encrypt_x64(ctx, input, output, msglen);

        return 0;

    }

#else

    wc_Chacha_encrypt_bytes(ctx, input, output, msglen);

    return 0;

#endif

}

#endif /* HAVE_CHACHA */

#endif /* END ChaCha C implementation */

#if defined(HAVE_CHACHA) && defined(HAVE_XCHACHA)

void wc_Chacha_purge_current_block(ChaCha* ctx)

{

    if (ctx->left > 0) {

        byte scratch[CHACHA_CHUNK_BYTES];

        XMEMSET(scratch, 0, sizeof(scratch));

        (void)wc_Chacha_Process(ctx, scratch, scratch, CHACHA_CHUNK_BYTES - ctx->left);

    }

}

/*

 * wc_HChacha_block - half a ChaCha block, for XChaCha

 *

 * see https://tools.ietf.org/html/draft-arciszewski-xchacha-03

 */

static WC_INLINE void wc_HChacha_block(ChaCha* ctx,

    word32 stream[CHACHA_CHUNK_WORDS/2], word32 nrounds)

{

    word32 x[CHACHA_CHUNK_WORDS];

    word32 i;

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

        x[i] = ctx->X[i];

    }

    for (i = nrounds; i > 0; i -= 2) {

        QUARTERROUND(0, 4,  8, 12)

        QUARTERROUND(1, 5,  9, 13)

        QUARTERROUND(2, 6, 10, 14)

        QUARTERROUND(3, 7, 11, 15)

        QUARTERROUND(0, 5, 10, 15)

        QUARTERROUND(1, 6, 11, 12)

        QUARTERROUND(2, 7,  8, 13)

        QUARTERROUND(3, 4,  9, 14)

    }

    for (i = 0; i < CHACHA_CHUNK_WORDS/4; ++i)

        stream[i] = x[i];

    for (i = CHACHA_CHUNK_WORDS/4; i < CHACHA_CHUNK_WORDS/2; ++i)

        stream[i] = x[i + CHACHA_CHUNK_WORDS/2];

}

/* XChaCha -- https://tools.ietf.org/html/draft-arciszewski-xchacha-03 */

int wc_XChacha_SetKey(ChaCha *ctx,

                      const byte *key, word32 keySz,

                      const byte *nonce, word32 nonceSz,

                      word32 counter)

{

    int ret;

    word32 k[CHACHA_MAX_KEY_SZ];

    byte   iv[CHACHA_IV_BYTES];

    if (nonceSz != XCHACHA_NONCE_BYTES)

        return BAD_FUNC_ARG;

    if ((ret = wc_Chacha_SetKey(ctx, key, keySz)) < 0)

        return ret;

    /* form a first chacha IV from the first 16 bytes of the nonce.

     * the first word is supplied in the "counter" arg, and

     * the result is a full 128 bit nonceful IV for the one-time block

     * crypto op that follows.

     */

    if ((ret = wc_Chacha_SetIV(ctx, nonce + 4, U8TO32_LITTLE(nonce))) < 0)

        return ret;

    wc_HChacha_block(ctx, k, 20); /* 20 rounds, but keeping half the output. */

    /* the HChacha output is used as a 256 bit key for the main cipher. */

    XMEMCPY(&ctx->X[4], k, 8 * sizeof(word32));

    /* use 8 bytes from the end of the 24 byte nonce, padded up to 12 bytes,

     * to form the IV for the main cipher.

     */

    XMEMSET(iv, 0, 4);

    XMEMCPY(iv + 4, nonce + 16, 8);

    if ((ret = wc_Chacha_SetIV(ctx, iv, counter)) < 0)

        return ret;

    ForceZero(k, sizeof k);

    ForceZero(iv, sizeof iv);

    return 0;

}

#endif /* HAVE_CHACHA && HAVE_XCHACHA */