/*

 * 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"

/* see bearssl_block.h */

void

br_aes_ct_ctr_init(br_aes_ct_ctr_keys *ctx,

  const void *key, size_t len)

{

  ctx->vtable = &br_aes_ct_ctr_vtable;

  ctx->num_rounds = br_aes_ct_keysched(ctx->skey, key, len);

}

static void

xorbuf(void *dst, const void *src, size_t len)

{

  unsigned char *d;

  const unsigned char *s;

  d = dst;

  s = src;

  while (len -- > 0) {

    *d ++ ^= *s ++;

  }

}

/* see bearssl_block.h */

uint32_t

br_aes_ct_ctr_run(const br_aes_ct_ctr_keys *ctx,

  const void *iv, uint32_t cc, void *data, size_t len)

{

  unsigned char *buf;

  const unsigned char *ivbuf;

  uint32_t iv0, iv1, iv2;

  uint32_t sk_exp[120];

  br_aes_ct_skey_expand(sk_exp, ctx->num_rounds, ctx->skey);

  ivbuf = iv;

  iv0 = br_dec32le(ivbuf);

  iv1 = br_dec32le(ivbuf + 4);

  iv2 = br_dec32le(ivbuf + 8);

  buf = data;

  while (len > 0) {

    uint32_t q[8];

    unsigned char tmp[32];

    /*

     * TODO: see if we can save on the first br_aes_ct_ortho()

     * call, since iv0/iv1/iv2 are constant for the whole run.

     */

    q[0] = q[1] = iv0;

    q[2] = q[3] = iv1;

    q[4] = q[5] = iv2;

    q[6] = br_swap32(cc);

    q[7] = br_swap32(cc + 1);

    br_aes_ct_ortho(q);

    br_aes_ct_bitslice_encrypt(ctx->num_rounds, sk_exp, q);

    br_aes_ct_ortho(q);

    br_enc32le(tmp, q[0]);

    br_enc32le(tmp + 4, q[2]);

    br_enc32le(tmp + 8, q[4]);

    br_enc32le(tmp + 12, q[6]);

    br_enc32le(tmp + 16, q[1]);

    br_enc32le(tmp + 20, q[3]);

    br_enc32le(tmp + 24, q[5]);

    br_enc32le(tmp + 28, q[7]);

    if (len <= 32) {

      xorbuf(buf, tmp, len);

      cc ++;

      if (len > 16) {

        cc ++;

      }

      break;

    }

    xorbuf(buf, tmp, 32);

    buf += 32;

    len -= 32;

    cc += 2;

  }

  return cc;

}

/* see bearssl_block.h */

const br_block_ctr_class br_aes_ct_ctr_vtable = {

  sizeof(br_aes_ct_ctr_keys),

  16,

  4,

  (void (*)(const br_block_ctr_class **, const void *, size_t))

    &br_aes_ct_ctr_init,

  (uint32_t (*)(const br_block_ctr_class *const *,

    const void *, uint32_t, void *, size_t))

    &br_aes_ct_ctr_run

};