/* umac-set-key.c

   Copyright (C) 2013 Niels Möller

   This file is part of GNU Nettle.

   GNU Nettle is free software: you can redistribute it and/or

   modify it under the terms of either:

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at your

       option) any later version.

   or

     * the GNU General Public License as published by the Free

       Software Foundation; either version 2 of the License, or (at your

       option) any later version.

   or both in parallel, as here.

   GNU Nettle is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   General Public License for more details.

   You should have received copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see http://www.gnu.org/licenses/.

*/

#if HAVE_CONFIG_H

# include "config.h"

#endif

#include <string.h>

#include "umac.h"

#include "umac-internal.h"

#include "macros.h"

static void

umac_kdf (struct aes128_ctx *aes, unsigned index, unsigned length, uint8_t *dst)

{

  uint8_t block[AES_BLOCK_SIZE];

  uint64_t count;

  WRITE_UINT64 (block, (uint64_t) index);

  for (count = 1; length >= AES_BLOCK_SIZE;

       length -= AES_BLOCK_SIZE, dst += AES_BLOCK_SIZE, count++)

    {

      WRITE_UINT64 (block + 8, count);

      aes128_encrypt (aes, AES_BLOCK_SIZE, dst, block);

    }

  if (length > 0)

    {

      WRITE_UINT64 (block + 8, count);

      aes128_encrypt (aes, AES_BLOCK_SIZE, block, block);

      memcpy (dst, block, length);

    }

}

#if WORDS_BIGENDIAN

#define BE_SWAP32(x) x

#define BE_SWAP32_N(n, x)

#else

#define BE_SWAP32(x)        \

  ((ROTL32(8,  x) & 0x00FF00FFUL) |   \

   (ROTL32(24, x) & 0xFF00FF00UL))

#define BE_SWAP32_N(n, x) do {     \

  unsigned be_i;        \

  for (be_i = 0; be_i < n; be_i++)   \

    {           \

      uint32_t be_x = (x)[be_i];    \

      (x)[be_i] = BE_SWAP32 (be_x);    \

    }            \

  } while (0)

#endif

void

_nettle_umac_set_key (uint32_t *l1_key, uint32_t *l2_key,

          uint64_t *l3_key1, uint32_t *l3_key2,

          struct aes128_ctx *aes, const uint8_t *key, unsigned n)

{

  unsigned size;

  uint8_t buffer[UMAC_KEY_SIZE];

  aes128_set_encrypt_key (aes, key);

  size = UMAC_BLOCK_SIZE / 4 + 4*(n-1);

  umac_kdf (aes, 1, size * sizeof(uint32_t), (uint8_t *) l1_key);

  BE_SWAP32_N (size, l1_key);

  size = 6*n;

  umac_kdf (aes, 2, size * sizeof(uint32_t), (uint8_t *) l2_key);

  _nettle_umac_l2_init (size, l2_key);

  size = 8*n;

  umac_kdf (aes, 3, size * sizeof(uint64_t), (uint8_t *) l3_key1);

  _nettle_umac_l3_init (size, l3_key1);

  /* No need to byteswap these subkeys. */

  umac_kdf (aes, 4, n * sizeof(uint32_t), (uint8_t *) l3_key2);

  umac_kdf (aes, 0, UMAC_KEY_SIZE, buffer);

  aes128_set_encrypt_key (aes, buffer);

}