/*
Copyright (c) 1996, David Mazieres <dm@uun.org>
Copyright (c) 2008, Damien Miller <djm@openbsd.org>
Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>

Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
chacha-merged.c version 20080118
D. J. Bernstein
Public domain.
*/

/* $OpenBSD: chacha_private.h,v 1.2 2013/10/04 07:02:27 djm Exp $ */

#include <stdint.h>

typedef uint8_t u8;
typedef uint32_t u32;

typedef struct
{
  u32 input[16]; /* could be compressed */
} chacha_ctx;

#define U8V(v) ((u8)(v))
#define U32V(v) ((u32)(v))

#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)

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

static void
chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
{
  const char *constants;

  (void) ivbits;
  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(chacha_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);
}

static void
chacha_encrypt_bytes(chacha_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 = NULL;
  u8 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
  }
}