/** @file AES256.cpp
 *  @version 3.3
 *  @date April 12th, 2017
 *
 *  @copyright 2016-17 DJI. All rights reserved.
 *
 */

#include "dji_aes.hpp"
//////////////////////////////////////////////////////////////////////////
// BEGIN OF AES-256
//
/*
*   Byte-oriented AES-256 implementation.
*   All lookup tables replaced with 'on the fly' calculations.
*
*   Copyright (c) 2007-2009 Ilya O. Levin, http://www.literatecode.com
*   Other contributors: Hal Finney
*
*   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.
*/

#define F(x) (((x) << 1) ^ ((((x) >> 7) & 1) * 0x1b))
#define FD(x) (((x) >> 1) ^ (((x)&1) ? 0x8d : 0))

#define BACK_TO_TABLES
#ifdef BACK_TO_TABLES

const uint8_t sbox[256] = {
  0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe,
  0xd7, 0xab, 0x76, 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4,
  0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7,
  0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, 0x04, 0xc7, 0x23, 0xc3,
  0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, 0x09,
  0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3,
  0x2f, 0x84, 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe,
  0x39, 0x4a, 0x4c, 0x58, 0xcf, 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85,
  0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, 0x51, 0xa3, 0x40, 0x8f, 0x92,
  0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, 0xcd, 0x0c,
  0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19,
  0x73, 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14,
  0xde, 0x5e, 0x0b, 0xdb, 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2,
  0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5,
  0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, 0xba, 0x78, 0x25,
  0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86,
  0xc1, 0x1d, 0x9e, 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e,
  0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42,
  0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};
const uint8_t sboxinv[256] = {
  0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81,
  0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e,
  0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23,
  0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66,
  0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72,
  0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65,
  0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46,
  0x57, 0xa7, 0x8d, 0x9d, 0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a,
  0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c, 0x1e, 0x8f, 0xca,
  0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91,
  0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6,
  0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8,
  0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f,
  0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2,
  0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, 0x1f, 0xdd, 0xa8,
  0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93,
  0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb,
  0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6,
  0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d
};

#define rj_sbox(x) sbox[(x)]
#define rj_sbox_inv(x) sboxinv[(x)]

#else /* tableless subroutines */

/* -------------------------------------------------------------------------- */
uint8_t gf_alog(uint8_t x) // calculate anti-logarithm gen 3
{
  uint8_t atb = 1, z;

  while (x--)
  {
    z = atb;
    atb <<= 1;
    if (z & 0x80)
      atb ^= 0x1b;
    atb ^= z;
  }

  return atb;
} /* gf_alog */

/* -------------------------------------------------------------------------- */
uint8_t gf_log(uint8_t x) // calculate logarithm gen 3
{
  uint8_t atb = 1, i = 0, z;

  do
  {
    if (atb == x)
      break;
    z = atb;
    atb <<= 1;
    if (z & 0x80)
      atb ^= 0x1b;
    atb ^= z;
  } while (++i > 0);

  return i;
} /* gf_log */

/* -------------------------------------------------------------------------- */
uint8_t gf_mulinv(uint8_t x) // calculate multiplicative inverse
{
  return (x) ? gf_alog(255 - gf_log(x)) : 0;
} /* gf_mulinv */

/* -------------------------------------------------------------------------- */
uint8_t
rj_sbox(uint8_t x)
{
  uint8_t y, sb;

  sb = y = gf_mulinv(x);
  y      = (y << 1) | (y >> 7);
  sb ^= y;
  y = (y << 1) | (y >> 7);
  sb ^= y;
  y = (y << 1) | (y >> 7);
  sb ^= y;
  y = (y << 1) | (y >> 7);
  sb ^= y;

  return (sb ^ 0x63);
} /* rj_sbox */

/* -------------------------------------------------------------------------- */
uint8_t
rj_sbox_inv(uint8_t x)
{
  uint8_t y, sb;

  y  = x ^ 0x63;
  sb = y = (y << 1) | (y >> 7);
  y      = (y << 2) | (y >> 6);
  sb ^= y;
  y = (y << 3) | (y >> 5);
  sb ^= y;

  return gf_mulinv(sb);
} /* rj_sbox_inv */

#endif

/* -------------------------------------------------------------------------- */
uint8_t
rj_xtime(uint8_t x)
{
  return (x & 0x80) ? ((x << 1) ^ 0x1b) : (x << 1);
} /* rj_xtime */

/* -------------------------------------------------------------------------- */
void
aes_subBytes(uint8_t* buf)
{
  register uint8_t i = 16;

  while (i--)
    buf[i] = rj_sbox(buf[i]);
} /* aes_subBytes */

/* -------------------------------------------------------------------------- */
void
aes_subBytes_inv(uint8_t* buf)
{
  register uint8_t i = 16;

  while (i--)
    buf[i] = rj_sbox_inv(buf[i]);
} /* aes_subBytes_inv */

/* -------------------------------------------------------------------------- */
void
aes_addRoundKey(uint8_t* buf, uint8_t* key)
{
  register uint8_t i = 16;

  while (i--)
    buf[i] ^= key[i];
} /* aes_addRoundKey */

/* -------------------------------------------------------------------------- */
void
aes_addRoundKey_cpy(uint8_t* buf, uint8_t* key, uint8_t* cpk)
{
  register uint8_t i = 16;

  while (i--)
    buf[i] ^= (cpk[i] = key[i]), cpk[16 + i] = key[16 + i];
} /* aes_addRoundKey_cpy */

/* -------------------------------------------------------------------------- */
void
aes_shiftRows(uint8_t* buf)
{
  register uint8_t i, j; /* to make it potentially parallelable :) */

  i       = buf[1];
  buf[1]  = buf[5];
  buf[5]  = buf[9];
  buf[9]  = buf[13];
  buf[13] = i;
  i       = buf[10];
  buf[10] = buf[2];
  buf[2]  = i;
  j       = buf[3];
  buf[3]  = buf[15];
  buf[15] = buf[11];
  buf[11] = buf[7];
  buf[7]  = j;
  j       = buf[14];
  buf[14] = buf[6];
  buf[6]  = j;

} /* aes_shiftRows */

/* -------------------------------------------------------------------------- */
void
aes_shiftRows_inv(uint8_t* buf)
{
  register uint8_t i, j; /* same as above :) */

  i       = buf[1];
  buf[1]  = buf[13];
  buf[13] = buf[9];
  buf[9]  = buf[5];
  buf[5]  = i;
  i       = buf[2];
  buf[2]  = buf[10];
  buf[10] = i;
  j       = buf[3];
  buf[3]  = buf[7];
  buf[7]  = buf[11];
  buf[11] = buf[15];
  buf[15] = j;
  j       = buf[6];
  buf[6]  = buf[14];
  buf[14] = j;

} /* aes_shiftRows_inv */

/* -------------------------------------------------------------------------- */
void
aes_mixColumns(uint8_t* buf)
{
  register uint8_t i, a, b, c, d, e;

  for (i = 0; i < 16; i += 4)
  {
    a = buf[i];
    b = buf[i + 1];
    c = buf[i + 2];
    d = buf[i + 3];
    e = a ^ b ^ c ^ d;
    buf[i] ^= e ^ rj_xtime(a ^ b);
    buf[i + 1] ^= e ^ rj_xtime(b ^ c);
    buf[i + 2] ^= e ^ rj_xtime(c ^ d);
    buf[i + 3] ^= e ^ rj_xtime(d ^ a);
  }
} /* aes_mixColumns */

/* -------------------------------------------------------------------------- */
void
aes_mixColumns_inv(uint8_t* buf)
{
  register uint8_t i, a, b, c, d, e, x, y, z;

  for (i = 0; i < 16; i += 4)
  {
    a = buf[i];
    b = buf[i + 1];
    c = buf[i + 2];
    d = buf[i + 3];
    e = a ^ b ^ c ^ d;
    z = rj_xtime(e);
    x = e ^ rj_xtime(rj_xtime(z ^ a ^ c));
    y = e ^ rj_xtime(rj_xtime(z ^ b ^ d));
    buf[i] ^= x ^ rj_xtime(a ^ b);
    buf[i + 1] ^= y ^ rj_xtime(b ^ c);
    buf[i + 2] ^= x ^ rj_xtime(c ^ d);
    buf[i + 3] ^= y ^ rj_xtime(d ^ a);
  }
} /* aes_mixColumns_inv */

/* -------------------------------------------------------------------------- */
void
aes_expandEncKey(uint8_t* k, uint8_t* rc)
{
  register uint8_t i;

  k[0] ^= rj_sbox(k[29]) ^ (*rc);
  k[1] ^= rj_sbox(k[30]);
  k[2] ^= rj_sbox(k[31]);
  k[3] ^= rj_sbox(k[28]);
  *rc = F(*rc);

  for (i = 4; i < 16; i += 4)
    k[i] ^= k[i - 4], k[i + 1] ^= k[i - 3], k[i + 2] ^= k[i - 2],
      k[i + 3] ^= k[i - 1];
  k[16] ^= rj_sbox(k[12]);
  k[17] ^= rj_sbox(k[13]);
  k[18] ^= rj_sbox(k[14]);
  k[19] ^= rj_sbox(k[15]);

  for (i = 20; i < 32; i += 4)
    k[i] ^= k[i - 4], k[i + 1] ^= k[i - 3], k[i + 2] ^= k[i - 2],
      k[i + 3] ^= k[i - 1];

} /* aes_expandEncKey */

/* -------------------------------------------------------------------------- */
void
aes_expandDecKey(uint8_t* k, uint8_t* rc)
{
  uint8_t i;

  for (i = 28; i > 16; i -= 4)
    k[i + 0] ^= k[i - 4], k[i + 1] ^= k[i - 3], k[i + 2] ^= k[i - 2],
      k[i + 3] ^= k[i - 1];

  k[16] ^= rj_sbox(k[12]);
  k[17] ^= rj_sbox(k[13]);
  k[18] ^= rj_sbox(k[14]);
  k[19] ^= rj_sbox(k[15]);

  for (i = 12; i > 0; i -= 4)
    k[i + 0] ^= k[i - 4], k[i + 1] ^= k[i - 3], k[i + 2] ^= k[i - 2],
      k[i + 3] ^= k[i - 1];

  *rc = FD(*rc);
  k[0] ^= rj_sbox(k[29]) ^ (*rc);
  k[1] ^= rj_sbox(k[30]);
  k[2] ^= rj_sbox(k[31]);
  k[3] ^= rj_sbox(k[28]);
} /* aes_expandDecKey */

/* -------------------------------------------------------------------------- */
void
aes256_init(aes256_context* ctx, uint8_t* k)
{
  uint8_t          rcon = 1;
  register uint8_t i;

  for (i           = 0; i < sizeof(ctx->key); i++)
    ctx->enckey[i] = ctx->deckey[i] = k[i];
  for (i = 8; --i;)
    aes_expandEncKey(ctx->deckey, &rcon);
} /* aes256_init */

/* -------------------------------------------------------------------------- */
void
aes256_done(aes256_context* ctx)
{
  register uint8_t i;

  for (i        = 0; i < sizeof(ctx->key); i++)
    ctx->key[i] = ctx->enckey[i] = ctx->deckey[i] = 0;
} /* aes256_done */

/* -------------------------------------------------------------------------- */
void
aes256_encrypt_ecb(aes256_context* ctx, uint8_t* buf)
{
  uint8_t i, rcon;

  aes_addRoundKey_cpy(buf, ctx->enckey, ctx->key);
  for (i = 1, rcon = 1; i < 14; ++i)
  {
    aes_subBytes(buf);
    aes_shiftRows(buf);
    aes_mixColumns(buf);
    if (i & 1)
    {
      aes_addRoundKey(buf, &ctx->key[16]);
    }
    else
    {
      aes_expandEncKey(ctx->key, &rcon), aes_addRoundKey(buf, ctx->key);
    }
  }
  aes_subBytes(buf);
  aes_shiftRows(buf);
  aes_expandEncKey(ctx->key, &rcon);
  aes_addRoundKey(buf, ctx->key);
} /* aes256_encrypt */

/* -------------------------------------------------------------------------- */
void
aes256_decrypt_ecb(aes256_context* ctx, uint8_t* buf)
{
  uint8_t i, rcon;

  aes_addRoundKey_cpy(buf, ctx->deckey, ctx->key);
  aes_shiftRows_inv(buf);
  aes_subBytes_inv(buf);

  for (i = 14, rcon = 0x80; --i;) //! @note exit when --i == 0;
  {
    if ((i & 1))
    {
      aes_expandDecKey(ctx->key, &rcon);
      aes_addRoundKey(buf, &ctx->key[16]);
    }
    else
      aes_addRoundKey(buf, ctx->key);
    aes_mixColumns_inv(buf);
    aes_shiftRows_inv(buf);
    aes_subBytes_inv(buf);
  }
  aes_addRoundKey(buf, ctx->key);
} /* aes256_decrypt */

// END OF AES-256
