/* 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 "mesh_util.h"
#include "mesh_aes_encrypt.h"

/* max number of calls until change the key (2^48).*/
const static uint64_t MAX_CALLS = ((uint64_t)1 << 48);

/*
 *  gf_wrap -- In our implementation, GF(2^128) is represented as a 16 byte
 *  array with byte 0 the most significant and byte 15 the least significant.
 *  High bit carry reduction is based on the primitive polynomial
 *
 *                     X^128 + X^7 + X^2 + X + 1,
 *
 *  which leads to the reduction formula X^128 = X^7 + X^2 + X + 1. Indeed,
 *  since 0 = (X^128 + X^7 + X^2 + 1) mod (X^128 + X^7 + X^2 + X + 1) and since
 *  addition of polynomials with coefficients in Z/Z(2) is just XOR, we can
 *  add X^128 to both sides to get
 *
 *       X^128 = (X^7 + X^2 + X + 1) mod (X^128 + X^7 + X^2 + X + 1)
 *
 *  and the coefficients of the polynomial on the right hand side form the
 *  string 1000 0111 = 0x87, which is the value of gf_wrap.
 *
 *  This gets used in the following way. Doubling in GF(2^128) is just a left
 *  shift by 1 bit, except when the most significant bit is 1. In the latter
 *  case, the relation X^128 = X^7 + X^2 + X + 1 says that the high order bit
 *  that overflows beyond 128 bits can be replaced by addition of
 *  X^7 + X^2 + X + 1 <--> 0x87 to the low order 128 bits. Since addition
 *  in GF(2^128) is represented by XOR, we therefore only have to XOR 0x87
 *  into the low order byte after a left shift when the starting high order
 *  bit is 1.
 */
const unsigned char gf_wrap = 0x87;

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] = {0};

    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] = {0};

    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] = {0};
    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;
}

int tc_cmac_setup(TCCmacState_t s, const uint8_t *key, TCAesKeySched_t sched)
{

    /* input sanity check: */
    if (s == (TCCmacState_t) 0 ||
            key == (const uint8_t *) 0) {
        return TC_CRYPTO_FAIL;
    }

    /* put s into a known state */
    _set(s, 0, sizeof(*s));
    s->sched = sched;

    /* configure the encryption key used by the underlying block cipher */
    tc_aes128_set_encrypt_key(s->sched, key);

    /* compute s->K1 and s->K2 from s->iv using s->keyid */
    _set(s->iv, 0, TC_AES_BLOCK_SIZE);
    tc_aes_encrypt(s->iv, s->iv, s->sched);
    gf_double (s->K1, s->iv);
    gf_double (s->K2, s->K1);

    /* reset s->iv to 0 in case someone wants to compute now */
    tc_cmac_init(s);

    return TC_CRYPTO_SUCCESS;
}

/*
 *  assumes: out != NULL and points to a GF(2^n) value to receive the
 *            doubled value;
 *           in != NULL and points to a 16 byte GF(2^n) value
 *            to double;
 *           the in and out buffers do not overlap.
 *  effects: doubles the GF(2^n) value pointed to by "in" and places
 *           the result in the GF(2^n) value pointed to by "out."
 */
void gf_double(uint8_t *out, uint8_t *in)
{

    /* start with low order byte */
    uint8_t *x = in + (TC_AES_BLOCK_SIZE - 1);

    /* if msb == 1, we need to add the gf_wrap value, otherwise add 0 */
    uint8_t carry = (in[0] >> 7) ? gf_wrap : 0;

    out += (TC_AES_BLOCK_SIZE - 1);
    for (;;) {
        *out-- = (*x << 1) ^ carry;
        if (x == in) {
            break;
        }
        carry = *x-- >> 7;
    }
}

int tc_cmac_init(TCCmacState_t s)
{
    /* input sanity check: */
    if (s == (TCCmacState_t) 0) {
        return TC_CRYPTO_FAIL;
    }

    /* CMAC starts with an all zero initialization vector */
    _set(s->iv, 0, TC_AES_BLOCK_SIZE);

    /* and the leftover buffer is empty */
    _set(s->leftover, 0, TC_AES_BLOCK_SIZE);
    s->leftover_offset = 0;

    /* Set countdown to max number of calls allowed before re-keying: */
    s->countdown = MAX_CALLS;

    return TC_CRYPTO_SUCCESS;
}

int tc_cmac_update(TCCmacState_t s, const uint8_t *data, size_t data_length)
{
    unsigned int i;

    /* input sanity check: */
    if (s == (TCCmacState_t) 0) {
        return TC_CRYPTO_FAIL;
    }
    if (data_length == 0) {
        return  TC_CRYPTO_SUCCESS;
    }
    if (data == (const uint8_t *) 0) {
        return TC_CRYPTO_FAIL;
    }

    if (s->countdown == 0) {
        return TC_CRYPTO_FAIL;
    }

    s->countdown--;

    if (s->leftover_offset > 0) {
        /* last data added to s didn't end on a TC_AES_BLOCK_SIZE byte boundary */
        size_t remaining_space = TC_AES_BLOCK_SIZE - s->leftover_offset;

        if (data_length < remaining_space) {
            /* still not enough data to encrypt this time either */
            _copy(&s->leftover[s->leftover_offset], data_length, data, data_length);
            s->leftover_offset += data_length;
            return TC_CRYPTO_SUCCESS;
        }
        /* leftover block is now full; encrypt it first */
        _copy(&s->leftover[s->leftover_offset],
              remaining_space,
              data,
              remaining_space);
        data_length -= remaining_space;
        data += remaining_space;
        s->leftover_offset = 0;

        for (i = 0; i < TC_AES_BLOCK_SIZE; ++i) {
            s->iv[i] ^= s->leftover[i];
        }
        tc_aes_encrypt(s->iv, s->iv, s->sched);
    }

    /* CBC encrypt each (except the last) of the data blocks */
    while (data_length > TC_AES_BLOCK_SIZE) {
        for (i = 0; i < TC_AES_BLOCK_SIZE; ++i) {
            s->iv[i] ^= data[i];
        }
        tc_aes_encrypt(s->iv, s->iv, s->sched);
        data += TC_AES_BLOCK_SIZE;
        data_length  -= TC_AES_BLOCK_SIZE;
    }

    if (data_length > 0) {
        /* save leftover data for next time */
        _copy(s->leftover, data_length, data, data_length);
        s->leftover_offset = data_length;
    }

    return TC_CRYPTO_SUCCESS;
}

int tc_cmac_final(uint8_t *tag, TCCmacState_t s)
{
    uint8_t *k = NULL;
    unsigned int i;

    /* input sanity check: */
    if (tag == (uint8_t *) 0 ||
            s == (TCCmacState_t) 0) {
        return TC_CRYPTO_FAIL;
    }

    if (s->leftover_offset == TC_AES_BLOCK_SIZE) {
        /* the last message block is a full-sized block */
        k = (uint8_t *) s->K1;
    } else {
        /* the final message block is not a full-sized  block */
        size_t remaining = TC_AES_BLOCK_SIZE - s->leftover_offset;

        _set(&s->leftover[s->leftover_offset], 0, remaining);
        s->leftover[s->leftover_offset] = TC_CMAC_PADDING;
        k = (uint8_t *) s->K2;
    }
    for (i = 0; i < TC_AES_BLOCK_SIZE; ++i) {
        s->iv[i] ^= s->leftover[i] ^ k[i];
    }

    tc_aes_encrypt(tag, s->iv, s->sched);

    /* erasing state: */
    tc_cmac_erase(s);

    return TC_CRYPTO_SUCCESS;
}

int tc_cmac_erase(TCCmacState_t s)
{
    if (s == (TCCmacState_t) 0) {
        return TC_CRYPTO_FAIL;
    }

    /* destroy the current state */
    _set(s, 0, sizeof(*s));

    return TC_CRYPTO_SUCCESS;
}