// Copyright (c) 2020-2021 The Bitcoin Core developers

// Distributed under the MIT software license, see the accompanying

// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <crypto/chacha20.h>

#include <test/fuzz/FuzzedDataProvider.h>

#include <test/fuzz/fuzz.h>

#include <test/fuzz/util.h>

#include <cstdint>

#include <vector>

/*

From https://cr.yp.to/chacha.html

chacha-merged.c version 20080118

D. J. Bernstein

Public domain.

*/

typedef unsigned int u32;

typedef unsigned char u8;

#define U8C(v) (v##U)

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

#define U8V(v) ((u8)(v)&U8C(0xFF))

#define U32V(v) ((u32)(v)&U32C(0xFFFFFFFF))

#define ROTL32(v, n) (U32V((v) << (n)) | ((v) >> (32 - (n))))

#define U8TO32_LITTLE(p)                                              \

    (((u32)((p)[0])) | ((u32)((p)[1]) << 8) | ((u32)((p)[2]) << 16) | \

     ((u32)((p)[3]) << 24))

#define U32TO8_LITTLE(p, v)      \

    do {                         \

        (p)[0] = U8V((v));       \

        (p)[1] = U8V((v) >> 8);  \

        (p)[2] = U8V((v) >> 16); \

        (p)[3] = U8V((v) >> 24); \

    } while (0)

/* ------------------------------------------------------------------------- */

/* Data structures */

typedef struct

{

    u32 input[16];

} ECRYPT_ctx;

/* ------------------------------------------------------------------------- */

/* Mandatory functions */

void ECRYPT_keysetup(

    ECRYPT_ctx* ctx,

    const u8* key,

    u32 keysize, /* Key size in bits. */

    u32 ivsize); /* IV size in bits. */

void ECRYPT_ivsetup(

    ECRYPT_ctx* ctx,

    const u8* iv);

void ECRYPT_encrypt_bytes(

    ECRYPT_ctx* ctx,

    const u8* plaintext,

    u8* ciphertext,

    u32 msglen); /* Message length in bytes. */

/* ------------------------------------------------------------------------- */

/* Optional features */

void ECRYPT_keystream_bytes(

    ECRYPT_ctx* ctx,

    u8* keystream,

    u32 length); /* Length of keystream in bytes. */

/* ------------------------------------------------------------------------- */

#define ROTATE(v, c) (ROTL32(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) \

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

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

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

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

static const char sigma[] = "expand 32-byte k";

static const char tau[] = "expand 16-byte k";

void ECRYPT_keysetup(ECRYPT_ctx* x, const u8* k, u32 kbits, u32 ivbits)

{

    const char* constants;

    x->input[4] = U8TO32_LITTLE(k + 0);

    x->input[5] = U8TO32_LITTLE(k + 4);

    x->input[6] = U8TO32_LITTLE(k + 8);

    x->input[7] = U8TO32_LITTLE(k + 12);

    if (kbits == 256) { /* recommended */

        k += 16;

        constants = sigma;

    } else { /* kbits == 128 */

        constants = tau;

    }

    x->input[8] = U8TO32_LITTLE(k + 0);

    x->input[9] = U8TO32_LITTLE(k + 4);

    x->input[10] = U8TO32_LITTLE(k + 8);

    x->input[11] = U8TO32_LITTLE(k + 12);

    x->input[0] = U8TO32_LITTLE(constants + 0);

    x->input[1] = U8TO32_LITTLE(constants + 4);

    x->input[2] = U8TO32_LITTLE(constants + 8);

    x->input[3] = U8TO32_LITTLE(constants + 12);

}

void ECRYPT_ivsetup(ECRYPT_ctx* x, const u8* iv)

{

    x->input[12] = 0;

    x->input[13] = 0;

    x->input[14] = U8TO32_LITTLE(iv + 0);

    x->input[15] = U8TO32_LITTLE(iv + 4);

}

void ECRYPT_encrypt_bytes(ECRYPT_ctx* x, const u8* m, u8* c, u32 bytes)

{

    u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;

    u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;

    u8* ctarget = nullptr;

    u8 tmp[64];

    uint32_t i;

    if (!bytes) return;

    j0 = x->input[0];

    j1 = x->input[1];

    j2 = x->input[2];

    j3 = x->input[3];

    j4 = x->input[4];

    j5 = x->input[5];

    j6 = x->input[6];

    j7 = x->input[7];

    j8 = x->input[8];

    j9 = x->input[9];

    j10 = x->input[10];

    j11 = x->input[11];

    j12 = x->input[12];

    j13 = x->input[13];

    j14 = x->input[14];

    j15 = x->input[15];

    for (;;) {

        if (bytes < 64) {

            for (i = 0; i < bytes; ++i)

                tmp[i] = m[i];

            m = tmp;

            ctarget = c;

            c = tmp;

        }

        x0 = j0;

        x1 = j1;

        x2 = j2;

        x3 = j3;

        x4 = j4;

        x5 = j5;

        x6 = j6;

        x7 = j7;

        x8 = j8;

        x9 = j9;

        x10 = j10;

        x11 = j11;

        x12 = j12;

        x13 = j13;

        x14 = j14;

        x15 = j15;

        for (i = 20; i > 0; i -= 2) {

            QUARTERROUND(x0, x4, x8, x12)

            QUARTERROUND(x1, x5, x9, x13)

            QUARTERROUND(x2, x6, x10, x14)

            QUARTERROUND(x3, x7, x11, x15)

            QUARTERROUND(x0, x5, x10, x15)

            QUARTERROUND(x1, x6, x11, x12)

            QUARTERROUND(x2, x7, x8, x13)

            QUARTERROUND(x3, x4, x9, x14)

        }

        x0 = PLUS(x0, j0);

        x1 = PLUS(x1, j1);

        x2 = PLUS(x2, j2);

        x3 = PLUS(x3, j3);

        x4 = PLUS(x4, j4);

        x5 = PLUS(x5, j5);

        x6 = PLUS(x6, j6);

        x7 = PLUS(x7, j7);

        x8 = PLUS(x8, j8);

        x9 = PLUS(x9, j9);

        x10 = PLUS(x10, j10);

        x11 = PLUS(x11, j11);

        x12 = PLUS(x12, j12);

        x13 = PLUS(x13, j13);

        x14 = PLUS(x14, j14);

        x15 = PLUS(x15, j15);

        x0 = XOR(x0, U8TO32_LITTLE(m + 0));

        x1 = XOR(x1, U8TO32_LITTLE(m + 4));

        x2 = XOR(x2, U8TO32_LITTLE(m + 8));

        x3 = XOR(x3, U8TO32_LITTLE(m + 12));

        x4 = XOR(x4, U8TO32_LITTLE(m + 16));

        x5 = XOR(x5, U8TO32_LITTLE(m + 20));

        x6 = XOR(x6, U8TO32_LITTLE(m + 24));

        x7 = XOR(x7, U8TO32_LITTLE(m + 28));

        x8 = XOR(x8, U8TO32_LITTLE(m + 32));

        x9 = XOR(x9, U8TO32_LITTLE(m + 36));

        x10 = XOR(x10, U8TO32_LITTLE(m + 40));

        x11 = XOR(x11, U8TO32_LITTLE(m + 44));

        x12 = XOR(x12, U8TO32_LITTLE(m + 48));

        x13 = XOR(x13, U8TO32_LITTLE(m + 52));

        x14 = XOR(x14, U8TO32_LITTLE(m + 56));

        x15 = XOR(x15, U8TO32_LITTLE(m + 60));

        j12 = PLUSONE(j12);

        if (!j12) {

            j13 = PLUSONE(j13);

            /* stopping at 2^70 bytes per nonce is user's responsibility */

        }

        U32TO8_LITTLE(c + 0, x0);

        U32TO8_LITTLE(c + 4, x1);

        U32TO8_LITTLE(c + 8, x2);

        U32TO8_LITTLE(c + 12, x3);

        U32TO8_LITTLE(c + 16, x4);

        U32TO8_LITTLE(c + 20, x5);

        U32TO8_LITTLE(c + 24, x6);

        U32TO8_LITTLE(c + 28, x7);

        U32TO8_LITTLE(c + 32, x8);

        U32TO8_LITTLE(c + 36, x9);

        U32TO8_LITTLE(c + 40, x10);

        U32TO8_LITTLE(c + 44, x11);

        U32TO8_LITTLE(c + 48, x12);

        U32TO8_LITTLE(c + 52, x13);

        U32TO8_LITTLE(c + 56, x14);

        U32TO8_LITTLE(c + 60, x15);

        if (bytes <= 64) {

            if (bytes < 64) {

                for (i = 0; i < bytes; ++i)

                    ctarget[i] = c[i];

            }

            x->input[12] = j12;

            x->input[13] = j13;

            return;

        }

        bytes -= 64;

        c += 64;

        m += 64;

    }

}

void ECRYPT_keystream_bytes(ECRYPT_ctx* x, u8* stream, u32 bytes)

{

    u32 i;

    for (i = 0; i < bytes; ++i)

        stream[i] = 0;

    ECRYPT_encrypt_bytes(x, stream, stream, bytes);

}

FUZZ_TARGET(crypto_diff_fuzz_chacha20)

{

    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};

    ECRYPT_ctx ctx;

    const std::vector<unsigned char> key = ConsumeFixedLengthByteVector(fuzzed_data_provider, 32);

    ChaCha20 chacha20{MakeByteSpan(key)};

    ECRYPT_keysetup(&ctx, key.data(), key.size() * 8, 0);

    // ECRYPT_keysetup() doesn't set the counter and nonce to 0 while SetKey() does

    static const uint8_t iv[8] = {0, 0, 0, 0, 0, 0, 0, 0};

    ChaCha20::Nonce96 nonce{0, 0};

    uint32_t counter{0};

    ECRYPT_ivsetup(&ctx, iv);

    LIMITED_WHILE (fuzzed_data_provider.ConsumeBool(), 3000) {

        CallOneOf(

            fuzzed_data_provider,

            [&] {

                const std::vector<unsigned char> key = ConsumeFixedLengthByteVector(fuzzed_data_provider, 32);

                chacha20.SetKey(MakeByteSpan(key));

                nonce = {0, 0};

                counter = 0;

                ECRYPT_keysetup(&ctx, key.data(), key.size() * 8, 0);

                // ECRYPT_keysetup() doesn't set the counter and nonce to 0 while SetKey() does

                uint8_t iv[8] = {0, 0, 0, 0, 0, 0, 0, 0};

                ECRYPT_ivsetup(&ctx, iv);

            },

            [&] {

                uint32_t iv_prefix = fuzzed_data_provider.ConsumeIntegral<uint32_t>();

                uint64_t iv = fuzzed_data_provider.ConsumeIntegral<uint64_t>();

                nonce = {iv_prefix, iv};

                counter = fuzzed_data_provider.ConsumeIntegral<uint32_t>();

                chacha20.Seek(nonce, counter);

                ctx.input[12] = counter;

                ctx.input[13] = iv_prefix;

                ctx.input[14] = iv;

                ctx.input[15] = iv >> 32;

            },

            [&] {

                uint32_t integralInRange = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096);

                std::vector<uint8_t> output(integralInRange);

                chacha20.Keystream(MakeWritableByteSpan(output));

                std::vector<uint8_t> djb_output(integralInRange);

                ECRYPT_keystream_bytes(&ctx, djb_output.data(), djb_output.size());

                assert(output == djb_output);

                // DJB's version seeks forward to a multiple of 64 bytes after every operation. Correct for that.

                uint32_t old_counter = counter;

                counter += (integralInRange + 63) >> 6;

                if (counter < old_counter) ++nonce.first;

                if (integralInRange & 63) {

                    chacha20.Seek(nonce, counter);

                }

                assert(counter == ctx.input[12]);

            },

            [&] {

                uint32_t integralInRange = fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096);

                std::vector<uint8_t> output(integralInRange);

                const std::vector<uint8_t> input = ConsumeFixedLengthByteVector(fuzzed_data_provider, output.size());

                chacha20.Crypt(MakeByteSpan(input), MakeWritableByteSpan(output));

                std::vector<uint8_t> djb_output(integralInRange);

                ECRYPT_encrypt_bytes(&ctx, input.data(), djb_output.data(), input.size());

                assert(output == djb_output);

                // DJB's version seeks forward to a multiple of 64 bytes after every operation. Correct for that.

                uint32_t old_counter = counter;

                counter += (integralInRange + 63) >> 6;

                if (counter < old_counter) ++nonce.first;

                if (integralInRange & 63) {

                    chacha20.Seek(nonce, counter);

                }

                assert(counter == ctx.input[12]);

            });

    }

}