/*
 chacha-merged.c version 20080118
 D. J. Bernstein
 Public domain.
 */

#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include <sodium/core.h>
#include <sodium/crypto_stream_chacha20.h>
#include <sodium/private/common.h>
#include <sodium/utils.h>

#include "../stream_chacha20.h"
#include "chacha20_ref.h"

struct chacha_ctx
{
  uint32_t input[16];
};

typedef struct chacha_ctx chacha_ctx;

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

#define U32V(v) ((uint32_t)(v)&U32C(0xFFFFFFFF))

#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 void
chacha_keysetup(chacha_ctx *ctx, const uint8_t *k)
{
  ctx->input[0]  = U32C(0x61707865);
  ctx->input[1]  = U32C(0x3320646e);
  ctx->input[2]  = U32C(0x79622d32);
  ctx->input[3]  = U32C(0x6b206574);
  ctx->input[4]  = LOAD32_LE(k + 0);
  ctx->input[5]  = LOAD32_LE(k + 4);
  ctx->input[6]  = LOAD32_LE(k + 8);
  ctx->input[7]  = LOAD32_LE(k + 12);
  ctx->input[8]  = LOAD32_LE(k + 16);
  ctx->input[9]  = LOAD32_LE(k + 20);
  ctx->input[10] = LOAD32_LE(k + 24);
  ctx->input[11] = LOAD32_LE(k + 28);
}

static void
chacha_ivsetup(chacha_ctx *ctx, const uint8_t *iv, const uint8_t *counter)
{
  ctx->input[12] = counter == NULL ? 0 : LOAD32_LE(counter + 0);
  ctx->input[13] = counter == NULL ? 0 : LOAD32_LE(counter + 4);
  ctx->input[14] = LOAD32_LE(iv + 0);
  ctx->input[15] = LOAD32_LE(iv + 4);
}

static void
chacha_ietf_ivsetup(chacha_ctx *ctx, const uint8_t *iv, const uint8_t *counter)
{
  ctx->input[12] = counter == NULL ? 0 : LOAD32_LE(counter);
  ctx->input[13] = LOAD32_LE(iv + 0);
  ctx->input[14] = LOAD32_LE(iv + 4);
  ctx->input[15] = LOAD32_LE(iv + 8);
}

static void
chacha20_encrypt_bytes(chacha_ctx *ctx, const uint8_t *m, uint8_t *c,
                       unsigned long long bytes)
{
  uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
  uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
  uint8_t *ctarget = NULL;
  uint8_t tmp[64];
  unsigned int i;

  if(!bytes)
  {
    return; /* LCOV_EXCL_LINE */
  }
  if(bytes > crypto_stream_chacha20_MESSAGEBYTES_MAX)
  {
    sodium_misuse();
  }
  j0  = ctx->input[0];
  j1  = ctx->input[1];
  j2  = ctx->input[2];
  j3  = ctx->input[3];
  j4  = ctx->input[4];
  j5  = ctx->input[5];
  j6  = ctx->input[6];
  j7  = ctx->input[7];
  j8  = ctx->input[8];
  j9  = ctx->input[9];
  j10 = ctx->input[10];
  j11 = ctx->input[11];
  j12 = ctx->input[12];
  j13 = ctx->input[13];
  j14 = ctx->input[14];
  j15 = ctx->input[15];

  for(;;)
  {
    if(bytes < 64)
    {
      memset(tmp, 0, 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, LOAD32_LE(m + 0));
    x1  = XOR(x1, LOAD32_LE(m + 4));
    x2  = XOR(x2, LOAD32_LE(m + 8));
    x3  = XOR(x3, LOAD32_LE(m + 12));
    x4  = XOR(x4, LOAD32_LE(m + 16));
    x5  = XOR(x5, LOAD32_LE(m + 20));
    x6  = XOR(x6, LOAD32_LE(m + 24));
    x7  = XOR(x7, LOAD32_LE(m + 28));
    x8  = XOR(x8, LOAD32_LE(m + 32));
    x9  = XOR(x9, LOAD32_LE(m + 36));
    x10 = XOR(x10, LOAD32_LE(m + 40));
    x11 = XOR(x11, LOAD32_LE(m + 44));
    x12 = XOR(x12, LOAD32_LE(m + 48));
    x13 = XOR(x13, LOAD32_LE(m + 52));
    x14 = XOR(x14, LOAD32_LE(m + 56));
    x15 = XOR(x15, LOAD32_LE(m + 60));

    j12 = PLUSONE(j12);
    /* LCOV_EXCL_START */
    if(!j12)
    {
      j13 = PLUSONE(j13);
    }
    /* LCOV_EXCL_STOP */

    STORE32_LE(c + 0, x0);
    STORE32_LE(c + 4, x1);
    STORE32_LE(c + 8, x2);
    STORE32_LE(c + 12, x3);
    STORE32_LE(c + 16, x4);
    STORE32_LE(c + 20, x5);
    STORE32_LE(c + 24, x6);
    STORE32_LE(c + 28, x7);
    STORE32_LE(c + 32, x8);
    STORE32_LE(c + 36, x9);
    STORE32_LE(c + 40, x10);
    STORE32_LE(c + 44, x11);
    STORE32_LE(c + 48, x12);
    STORE32_LE(c + 52, x13);
    STORE32_LE(c + 56, x14);
    STORE32_LE(c + 60, x15);

    if(bytes <= 64)
    {
      if(bytes < 64)
      {
        for(i = 0; i < (unsigned int)bytes; ++i)
        {
          ctarget[i] = c[i]; /* ctarget cannot be NULL */
        }
      }
      ctx->input[12] = j12;
      ctx->input[13] = j13;

      return;
    }
    bytes -= 64;
    c += 64;
    m += 64;
  }
}

static int
stream_ref(unsigned char *c, unsigned long long clen, const unsigned char *n,
           const unsigned char *k)
{
  struct chacha_ctx ctx;

  if(!clen)
  {
    return 0;
  }
  COMPILER_ASSERT(crypto_stream_chacha20_KEYBYTES == 256 / 8);
  chacha_keysetup(&ctx, k);
  chacha_ivsetup(&ctx, n, NULL);
  memset(c, 0, clen);
  chacha20_encrypt_bytes(&ctx, c, c, clen);
  sodium_memzero(&ctx, sizeof ctx);

  return 0;
}

static int
stream_ietf_ref(unsigned char *c, unsigned long long clen,
                const unsigned char *n, const unsigned char *k)
{
  struct chacha_ctx ctx;

  if(!clen)
  {
    return 0;
  }
  COMPILER_ASSERT(crypto_stream_chacha20_KEYBYTES == 256 / 8);
  chacha_keysetup(&ctx, k);
  chacha_ietf_ivsetup(&ctx, n, NULL);
  memset(c, 0, clen);
  chacha20_encrypt_bytes(&ctx, c, c, clen);
  sodium_memzero(&ctx, sizeof ctx);

  return 0;
}

static int
stream_ref_xor_ic(unsigned char *c, const unsigned char *m,
                  unsigned long long mlen, const unsigned char *n, uint64_t ic,
                  const unsigned char *k)
{
  struct chacha_ctx ctx;
  uint8_t ic_bytes[8];
  uint32_t ic_high;
  uint32_t ic_low;

  if(!mlen)
  {
    return 0;
  }
  ic_high = U32V(ic >> 32);
  ic_low  = U32V(ic);
  STORE32_LE(&ic_bytes[0], ic_low);
  STORE32_LE(&ic_bytes[4], ic_high);
  chacha_keysetup(&ctx, k);
  chacha_ivsetup(&ctx, n, ic_bytes);
  chacha20_encrypt_bytes(&ctx, m, c, mlen);
  sodium_memzero(&ctx, sizeof ctx);

  return 0;
}

static int
stream_ietf_ref_xor_ic(unsigned char *c, const unsigned char *m,
                       unsigned long long mlen, const unsigned char *n,
                       uint32_t ic, const unsigned char *k)
{
  struct chacha_ctx ctx;
  uint8_t ic_bytes[4];

  if(!mlen)
  {
    return 0;
  }
  STORE32_LE(ic_bytes, ic);
  chacha_keysetup(&ctx, k);
  chacha_ietf_ivsetup(&ctx, n, ic_bytes);
  chacha20_encrypt_bytes(&ctx, m, c, mlen);
  sodium_memzero(&ctx, sizeof ctx);

  return 0;
}

struct crypto_stream_chacha20_implementation
    crypto_stream_chacha20_ref_implementation = {
        SODIUM_C99(.stream =) stream_ref,
        SODIUM_C99(.stream_ietf =) stream_ietf_ref,
        SODIUM_C99(.stream_xor_ic =) stream_ref_xor_ic,
        SODIUM_C99(.stream_ietf_xor_ic =) stream_ietf_ref_xor_ic};