/****************************************************************************
 * crypto/chacha_private.h
 * $OpenBSD: chacha_private.h,v 1.4 2020/07/22 13:54:30 tobhe Exp $
 *
 * chacha-merged.c version 20080118
 * D. J. Bernstein
 * Public domain.
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <sys/systm.h>

typedef struct
{
  uint32_t input[16]; /* could be compressed */
}
chacha_ctx;

#define U8C(v) (v##U)
#define U32C(v) (v##U)

#define U8V(v) ((uint8_t)(v) & U8C(0xFF))
#define U32V(v) ((uint32_t)(v) & U32C(0xFFFFFFFF))

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

#define U8TO32_LITTLE(p) \
    (((uint32_t)((p)[0])) | \
    ((uint32_t)((p)[1]) << 8) | \
    ((uint32_t)((p)[2]) << 16) | \
    ((uint32_t)((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)

#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)                 \
  do                                             \
    {                                            \
      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);  \
    }                                            \
  while (0)

static const char sigma[16] = "expand 32-byte k";
static const char tau[16] = "expand 16-byte k";

static inline void hchacha20(FAR uint32_t *derived_key,
                             FAR const uint8_t *nonce,
                             FAR const uint8_t *key)
{
  int i;
  uint32_t x[] =
  {
    U8TO32_LITTLE(sigma + 0),
    U8TO32_LITTLE(sigma + 4),
    U8TO32_LITTLE(sigma + 8),
    U8TO32_LITTLE(sigma + 12),
    U8TO32_LITTLE(key + 0),
    U8TO32_LITTLE(key + 4),
    U8TO32_LITTLE(key + 8),
    U8TO32_LITTLE(key + 12),
    U8TO32_LITTLE(key + 16),
    U8TO32_LITTLE(key + 20),
    U8TO32_LITTLE(key + 24),
    U8TO32_LITTLE(key + 28),
    U8TO32_LITTLE(nonce + 0),
    U8TO32_LITTLE(nonce + 4),
    U8TO32_LITTLE(nonce + 8),
    U8TO32_LITTLE(nonce + 12)
  };

  for (i = 20; i > 0; i -= 2)
    {
      QUARTERROUND(x[0], x[4], x[8], x[12]);
      QUARTERROUND(x[1], x[5], x[9], x[13]);
      QUARTERROUND(x[2], x[6], x[10], x[14]);
      QUARTERROUND(x[3], x[7], x[11], x[15]);
      QUARTERROUND(x[0], x[5], x[10], x[15]);
      QUARTERROUND(x[1], x[6], x[11], x[12]);
      QUARTERROUND(x[2], x[7], x[8], x[13]);
      QUARTERROUND(x[3], x[4], x[9], x[14]);
    }

  memcpy(derived_key + 0, x + 0, sizeof(uint32_t) * 4);
  memcpy(derived_key + 4, x + 12, sizeof(uint32_t) * 4);
}

static void chacha_keysetup(FAR chacha_ctx *x,
                            FAR const uint8_t *k,
                            FAR uint32_t kbits)
{
  FAR 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);
}

static void chacha_ivsetup(FAR chacha_ctx *x,
                           FAR const uint8_t *iv,
                           FAR const uint8_t *counter)
{
  x->input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
  x->input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
  x->input[14] = U8TO32_LITTLE(iv + 0);
  x->input[15] = U8TO32_LITTLE(iv + 4);
}

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

#ifndef KEYSTREAM_ONLY
      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));
#endif

      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;
#ifndef KEYSTREAM_ONLY
      m += 64;
#endif
    }
}