/*

 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>

 *

 * Permission is hereby granted, free of charge, to any person obtaining 

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be 

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS

 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN

 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

 * SOFTWARE.

 */

#include "inner.h"

#define S   br_aes_S

static void

add_round_key(unsigned *state, const uint32_t *skeys)

{

  int i;

  for (i = 0; i < 16; i += 4) {

    uint32_t k;

    k = *skeys ++;

    state[i + 0] ^= (unsigned)(k >> 24);

    state[i + 1] ^= (unsigned)(k >> 16) & 0xFF;

    state[i + 2] ^= (unsigned)(k >> 8) & 0xFF;

    state[i + 3] ^= (unsigned)k & 0xFF;

  }

}

static void

sub_bytes(unsigned *state)

{

  int i;

  for (i = 0; i < 16; i ++) {

    state[i] = S[state[i]];

  }

}

static void

shift_rows(unsigned *state)

{

  unsigned tmp;

  tmp = state[1];

  state[1] = state[5];

  state[5] = state[9];

  state[9] = state[13];

  state[13] = tmp;

  tmp = state[2];

  state[2] = state[10];

  state[10] = tmp;

  tmp = state[6];

  state[6] = state[14];

  state[14] = tmp;

  tmp = state[15];

  state[15] = state[11];

  state[11] = state[7];

  state[7] = state[3];

  state[3] = tmp;

}

static void

mix_columns(unsigned *state)

{

  int i;

  for (i = 0; i < 16; i += 4) {

    unsigned s0, s1, s2, s3;

    unsigned t0, t1, t2, t3;

    s0 = state[i + 0];

    s1 = state[i + 1];

    s2 = state[i + 2];

    s3 = state[i + 3];

    t0 = (s0 << 1) ^ s1 ^ (s1 << 1) ^ s2 ^ s3;

    t1 = s0 ^ (s1 << 1) ^ s2 ^ (s2 << 1) ^ s3;

    t2 = s0 ^ s1 ^ (s2 << 1) ^ s3 ^ (s3 << 1);

    t3 = s0 ^ (s0 << 1) ^ s1 ^ s2 ^ (s3 << 1);

    state[i + 0] = t0 ^ ((unsigned)(-(int)(t0 >> 8)) & 0x11B);

    state[i + 1] = t1 ^ ((unsigned)(-(int)(t1 >> 8)) & 0x11B);

    state[i + 2] = t2 ^ ((unsigned)(-(int)(t2 >> 8)) & 0x11B);

    state[i + 3] = t3 ^ ((unsigned)(-(int)(t3 >> 8)) & 0x11B);

  }

}

/* see inner.h */

void

br_aes_small_encrypt(unsigned num_rounds, const uint32_t *skey, void *data)

{

  unsigned char *buf;

  unsigned state[16];

  unsigned u;

  buf = data;

  for (u = 0; u < 16; u ++) {

    state[u] = buf[u];

  }

  add_round_key(state, skey);

  for (u = 1; u < num_rounds; u ++) {

    sub_bytes(state);

    shift_rows(state);

    mix_columns(state);

    add_round_key(state, skey + (u << 2));

  }

  sub_bytes(state);

  shift_rows(state);

  add_round_key(state, skey + (num_rounds << 2));

  for (u = 0; u < 16; u ++) {

    buf[u] = state[u];

  }

}