/* aes_encrypt.c - TinyCrypt implementation of AES encryption procedure */

/*
    Copyright (C) 2017 by Intel Corporation, All Rights Reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

      - Redistributions of source code must retain the above copyright notice,
       this list of conditions and the following disclaimer.

      - Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

      - Neither the name of Intel Corporation nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/

#include <tinycrypt/aes.h>
#include <tinycrypt/utils.h>
#include <tinycrypt/constants.h>

static 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
};

static inline unsigned int rotword(unsigned int a)
{
    return (((a) >> 24)|((a) << 8));
}

#define subbyte(a, o)(sbox[((a) >> (o))&0xff] << (o))
#define subword(a)(subbyte(a, 24)|subbyte(a, 16)|subbyte(a, 8)|subbyte(a, 0))

int tc_aes128_set_encrypt_key(TCAesKeySched_t s, const uint8_t* k)
{
    const unsigned int rconst[11] =
    {
        0x00000000, 0x01000000, 0x02000000, 0x04000000, 0x08000000, 0x10000000,
        0x20000000, 0x40000000, 0x80000000, 0x1b000000, 0x36000000
    };
    unsigned int i;
    unsigned int t;

    if (s == (TCAesKeySched_t) 0)
    {
        return TC_CRYPTO_FAIL;
    }
    else if (k == (const uint8_t*) 0)
    {
        return TC_CRYPTO_FAIL;
    }

    for (i = 0; i < Nk; ++i)
    {
        s->words[i] = (k[Nb*i]<<24) | (k[Nb*i+1]<<16) |
                      (k[Nb*i+2]<<8) | (k[Nb*i+3]);
    }

    for (; i < (Nb * (Nr + 1)); ++i)
    {
        t = s->words[i-1];

        if ((i % Nk) == 0)
        {
            t = subword(rotword(t)) ^ rconst[i/Nk];
        }

        s->words[i] = s->words[i-Nk] ^ t;
    }

    return TC_CRYPTO_SUCCESS;
}

static inline void add_round_key(uint8_t* s, const unsigned int* k)
{
    s[0] ^= (uint8_t)(k[0] >> 24);
    s[1] ^= (uint8_t)(k[0] >> 16);
    s[2] ^= (uint8_t)(k[0] >> 8);
    s[3] ^= (uint8_t)(k[0]);
    s[4] ^= (uint8_t)(k[1] >> 24);
    s[5] ^= (uint8_t)(k[1] >> 16);
    s[6] ^= (uint8_t)(k[1] >> 8);
    s[7] ^= (uint8_t)(k[1]);
    s[8] ^= (uint8_t)(k[2] >> 24);
    s[9] ^= (uint8_t)(k[2] >> 16);
    s[10] ^= (uint8_t)(k[2] >> 8);
    s[11] ^= (uint8_t)(k[2]);
    s[12] ^= (uint8_t)(k[3] >> 24);
    s[13] ^= (uint8_t)(k[3] >> 16);
    s[14] ^= (uint8_t)(k[3] >> 8);
    s[15] ^= (uint8_t)(k[3]);
}

static inline void sub_bytes(uint8_t* s)
{
    unsigned int i;

    for (i = 0; i < (Nb * Nk); ++i)
    {
        s[i] = sbox[s[i]];
    }
}

#define triple(a)(_double_byte(a)^(a))

static inline void mult_row_column(uint8_t* out, const uint8_t* in)
{
    out[0] = _double_byte(in[0]) ^ triple(in[1]) ^ in[2] ^ in[3];
    out[1] = in[0] ^ _double_byte(in[1]) ^ triple(in[2]) ^ in[3];
    out[2] = in[0] ^ in[1] ^ _double_byte(in[2]) ^ triple(in[3]);
    out[3] = triple(in[0]) ^ in[1] ^ in[2] ^ _double_byte(in[3]);
}

static inline void mix_columns(uint8_t* s)
{
    uint8_t t[Nb*Nk];
    mult_row_column(t, s);
    mult_row_column(&t[Nb], s+Nb);
    mult_row_column(&t[2 * Nb], s + (2 * Nb));
    mult_row_column(&t[3 * Nb], s + (3 * Nb));
    (void) _copy(s, sizeof(t), t, sizeof(t));
}

/*
    This shift_rows also implements the matrix flip required for mix_columns, but
    performs it here to reduce the number of memory operations.
*/
static inline void shift_rows(uint8_t* s)
{
    uint8_t t[Nb * Nk];
    t[0]  = s[0];
    t[1] = s[5];
    t[2] = s[10];
    t[3] = s[15];
    t[4]  = s[4];
    t[5] = s[9];
    t[6] = s[14];
    t[7] = s[3];
    t[8]  = s[8];
    t[9] = s[13];
    t[10] = s[2];
    t[11] = s[7];
    t[12] = s[12];
    t[13] = s[1];
    t[14] = s[6];
    t[15] = s[11];
    (void) _copy(s, sizeof(t), t, sizeof(t));
}

int tc_aes_encrypt(uint8_t* out, const uint8_t* in, const TCAesKeySched_t s)
{
    uint8_t state[Nk*Nb];
    unsigned int i;

    if (out == (uint8_t*) 0)
    {
        return TC_CRYPTO_FAIL;
    }
    else if (in == (const uint8_t*) 0)
    {
        return TC_CRYPTO_FAIL;
    }
    else if (s == (TCAesKeySched_t) 0)
    {
        return TC_CRYPTO_FAIL;
    }

    (void)_copy(state, sizeof(state), in, sizeof(state));
    add_round_key(state, s->words);

    for (i = 0; i < (Nr - 1); ++i)
    {
        sub_bytes(state);
        shift_rows(state);
        mix_columns(state);
        add_round_key(state, s->words + Nb*(i+1));
    }

    sub_bytes(state);
    shift_rows(state);
    add_round_key(state, s->words + Nb*(i+1));
    (void)_copy(out, sizeof(state), state, sizeof(state));
    /* zeroing out the state buffer */
    _set(state, TC_ZERO_BYTE, sizeof(state));
    return TC_CRYPTO_SUCCESS;
}
