AESCommon.cpp

/*
 * Copyright (C) 2015 Southern Storm Software, Pty Ltd.
 *
 * 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 "AES.h"
#include "Crypto.h"
#include "utility/ProgMemUtil.h"

// AES S-box (http://en.wikipedia.org/wiki/Rijndael_S-box)
static uint8_t const sbox[256] PROGMEM = {
    0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5,     // 0x00
    0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
    0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0,     // 0x10
    0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
    0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC,     // 0x20
    0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
    0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A,     // 0x30
    0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
    0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0,     // 0x40
    0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
    0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B,     // 0x50
    0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
    0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85,     // 0x60
    0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
    0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5,     // 0x70
    0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
    0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17,     // 0x80
    0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
    0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88,     // 0x90
    0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
    0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C,     // 0xA0
    0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
    0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9,     // 0xB0
    0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
    0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6,     // 0xC0
    0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
    0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E,     // 0xD0
    0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
    0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94,     // 0xE0
    0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
    0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68,     // 0xF0
    0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16
};

// AES inverse S-box (http://en.wikipedia.org/wiki/Rijndael_S-box)
static uint8_t const sbox_inverse[256] PROGMEM = {
    0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38,     // 0x00
    0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,
    0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87,     // 0x10
    0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,
    0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D,     // 0x20
    0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
    0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2,     // 0x30
    0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,
    0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16,     // 0x40
    0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,
    0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA,     // 0x50
    0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
    0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A,     // 0x60
    0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,
    0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02,     // 0x70
    0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
    0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA,     // 0x80
    0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
    0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85,     // 0x90
    0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,
    0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89,     // 0xA0
    0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,
    0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20,     // 0xB0
    0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
    0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31,     // 0xC0
    0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,
    0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D,     // 0xD0
    0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,
    0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0,     // 0xE0
    0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
    0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26,     // 0xF0
    0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D
};

AESCommon::AESCommon()
    : rounds(0), schedule(0)
{
}

AESCommon::~AESCommon()
{
    clean(state1);
    clean(state2);
}

size_t AESCommon::blockSize() const
{
    return 16;
}

// Constants to correct Galois multiplication for the high bits
// that are shifted out when multiplying by powers of two.
static uint8_t const K[8] = {
    0x00,
    0x1B,
    (0x1B << 1),
    (0x1B << 1) ^ 0x1B,
    (0x1B << 2),
    (0x1B << 2) ^ 0x1B,
    (0x1B << 2) ^ (0x1B << 1),
    (0x1B << 2) ^ (0x1B << 1) ^ 0x1B
};

// Multiply x by 2 in the Galois field, to achieve the effect of the following:
//
//     if (x & 0x80)
//         return (x << 1) ^ 0x1B;
//     else
//         return (x << 1);
//
// However, we don't want to use runtime conditionals if we can help it
// to avoid leaking timing information from the implementation.
// In this case, multiplication is slightly faster than table lookup on AVR.
#define gmul2(x)    (t = ((uint16_t)(x)) << 1, \
                     ((uint8_t)t) ^ (uint8_t)(0x1B * ((uint8_t)(t >> 8))))

// Multiply x by 4 in the Galois field.
#define gmul4(x)    (t = ((uint16_t)(x)) << 2, ((uint8_t)t) ^ K[t >> 8])

// Multiply x by 8 in the Galois field.
#define gmul8(x)    (t = ((uint16_t)(x)) << 3, ((uint8_t)t) ^ K[t >> 8])

#define OUT(col, row)   output[(col) * 4 + (row)]
#define IN(col, row)    input[(col) * 4 + (row)]

static void subBytesAndShiftRows(uint8_t *output, const uint8_t *input)
{
    OUT(0, 0) = pgm_read_byte(sbox + IN(0, 0));
    OUT(0, 1) = pgm_read_byte(sbox + IN(1, 1));
    OUT(0, 2) = pgm_read_byte(sbox + IN(2, 2));
    OUT(0, 3) = pgm_read_byte(sbox + IN(3, 3));
    OUT(1, 0) = pgm_read_byte(sbox + IN(1, 0));
    OUT(1, 1) = pgm_read_byte(sbox + IN(2, 1));
    OUT(1, 2) = pgm_read_byte(sbox + IN(3, 2));
    OUT(1, 3) = pgm_read_byte(sbox + IN(0, 3));
    OUT(2, 0) = pgm_read_byte(sbox + IN(2, 0));
    OUT(2, 1) = pgm_read_byte(sbox + IN(3, 1));
    OUT(2, 2) = pgm_read_byte(sbox + IN(0, 2));
    OUT(2, 3) = pgm_read_byte(sbox + IN(1, 3));
    OUT(3, 0) = pgm_read_byte(sbox + IN(3, 0));
    OUT(3, 1) = pgm_read_byte(sbox + IN(0, 1));
    OUT(3, 2) = pgm_read_byte(sbox + IN(1, 2));
    OUT(3, 3) = pgm_read_byte(sbox + IN(2, 3));
}

static void inverseShiftRowsAndSubBytes(uint8_t *output, const uint8_t *input)
{
    OUT(0, 0) = pgm_read_byte(sbox_inverse + IN(0, 0));
    OUT(0, 1) = pgm_read_byte(sbox_inverse + IN(3, 1));
    OUT(0, 2) = pgm_read_byte(sbox_inverse + IN(2, 2));
    OUT(0, 3) = pgm_read_byte(sbox_inverse + IN(1, 3));
    OUT(1, 0) = pgm_read_byte(sbox_inverse + IN(1, 0));
    OUT(1, 1) = pgm_read_byte(sbox_inverse + IN(0, 1));
    OUT(1, 2) = pgm_read_byte(sbox_inverse + IN(3, 2));
    OUT(1, 3) = pgm_read_byte(sbox_inverse + IN(2, 3));
    OUT(2, 0) = pgm_read_byte(sbox_inverse + IN(2, 0));
    OUT(2, 1) = pgm_read_byte(sbox_inverse + IN(1, 1));
    OUT(2, 2) = pgm_read_byte(sbox_inverse + IN(0, 2));
    OUT(2, 3) = pgm_read_byte(sbox_inverse + IN(3, 3));
    OUT(3, 0) = pgm_read_byte(sbox_inverse + IN(3, 0));
    OUT(3, 1) = pgm_read_byte(sbox_inverse + IN(2, 1));
    OUT(3, 2) = pgm_read_byte(sbox_inverse + IN(1, 2));
    OUT(3, 3) = pgm_read_byte(sbox_inverse + IN(0, 3));
}

static void mixColumn(uint8_t *output, uint8_t *input)
{
    uint16_t t; // Needed by the gmul2 macro.
    uint8_t a = input[0];
    uint8_t b = input[1];
    uint8_t c = input[2];
    uint8_t d = input[3];
    uint8_t a2 = gmul2(a);
    uint8_t b2 = gmul2(b);
    uint8_t c2 = gmul2(c);
    uint8_t d2 = gmul2(d);
    output[0] = a2 ^ b2 ^ b ^ c ^ d;
    output[1] = a ^ b2 ^ c2 ^ c ^ d;
    output[2] = a ^ b ^ c2 ^ d2 ^ d;
    output[3] = a2 ^ a ^ b ^ c ^ d2;
}

static void inverseMixColumn(uint8_t *output, const uint8_t *input)
{
    uint16_t t; // Needed by the gmul2, gmul4, and gmul8 macros.
    uint8_t a = input[0];
    uint8_t b = input[1];
    uint8_t c = input[2];
    uint8_t d = input[3];
    uint8_t a2 = gmul2(a);
    uint8_t b2 = gmul2(b);
    uint8_t c2 = gmul2(c);
    uint8_t d2 = gmul2(d);
    uint8_t a4 = gmul4(a);
    uint8_t b4 = gmul4(b);
    uint8_t c4 = gmul4(c);
    uint8_t d4 = gmul4(d);
    uint8_t a8 = gmul8(a);
    uint8_t b8 = gmul8(b);
    uint8_t c8 = gmul8(c);
    uint8_t d8 = gmul8(d);
    output[0] = a8 ^ a4 ^ a2 ^ b8 ^ b2 ^ b ^ c8 ^ c4 ^ c ^ d8 ^ d;
    output[1] = a8 ^ a ^ b8 ^ b4 ^ b2 ^ c8 ^ c2 ^ c ^ d8 ^ d4 ^ d;
    output[2] = a8 ^ a4 ^ a ^ b8 ^ b ^ c8 ^ c4 ^ c2 ^ d8 ^ d2 ^ d;
    output[3] = a8 ^ a2 ^ a ^ b8 ^ b4 ^ b ^ c8 ^ c ^ d8 ^ d4 ^ d2;
}

void AESCommon::encryptBlock(uint8_t *output, const uint8_t *input)
{
    const uint8_t *roundKey = schedule;
    uint8_t posn;
    uint8_t round;

    // Copy the input into the state and XOR with the first round key.
    for (posn = 0; posn < 16; ++posn)
        state1[posn] = input[posn] ^ roundKey[posn];
    roundKey += 16;

    // Perform all rounds except the last.
    for (round = rounds; round > 1; --round) {
        subBytesAndShiftRows(state2, state1);
        mixColumn(state1,      state2);
        mixColumn(state1 + 4,  state2 + 4);
        mixColumn(state1 + 8,  state2 + 8);
        mixColumn(state1 + 12, state2 + 12);
        for (posn = 0; posn < 16; ++posn)
            state1[posn] ^= roundKey[posn];
        roundKey += 16;
    }

    // Perform the final round.
    subBytesAndShiftRows(state2, state1);
    for (posn = 0; posn < 16; ++posn)
        output[posn] = state2[posn] ^ roundKey[posn];
}

void AESCommon::decryptBlock(uint8_t *output, const uint8_t *input)
{
    const uint8_t *roundKey = schedule + rounds * 16;
    uint8_t round;
    uint8_t posn;

    // Copy the input into the state and reverse the final round.
    for (posn = 0; posn < 16; ++posn)
        state1[posn] = input[posn] ^ roundKey[posn];
    inverseShiftRowsAndSubBytes(state2, state1);

    // Perform all other rounds in reverse.
    for (round = rounds; round > 1; --round) {
        roundKey -= 16;
        for (posn = 0; posn < 16; ++posn)
            state2[posn] ^= roundKey[posn];
        inverseMixColumn(state1,      state2);
        inverseMixColumn(state1 + 4,  state2 + 4);
        inverseMixColumn(state1 + 8,  state2 + 8);
        inverseMixColumn(state1 + 12, state2 + 12);
        inverseShiftRowsAndSubBytes(state2, state1);
    }

    // Reverse the initial round and create the output words.
    roundKey -= 16;
    for (posn = 0; posn < 16; ++posn)
        output[posn] = state2[posn] ^ roundKey[posn];
}

void AESCommon::clear()
{
    clean(schedule, (rounds + 1) * 16);
    clean(state1);
    clean(state2);
}

void AESCommon::keyScheduleCore(uint8_t *output, const uint8_t *input, uint8_t iteration)
{
    // Rcon(i), 2^i in the Rijndael finite field, for i = 0..10.
    // http://en.wikipedia.org/wiki/Rijndael_key_schedule
    static uint8_t const rcon[11] PROGMEM = {
        0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40,     // 0x00
        0x80, 0x1B, 0x36
    };
    output[0] = pgm_read_byte(sbox + input[1]) ^ pgm_read_byte(rcon + iteration);
    output[1] = pgm_read_byte(sbox + input[2]);
    output[2] = pgm_read_byte(sbox + input[3]);
    output[3] = pgm_read_byte(sbox + input[0]);
}

void AESCommon::applySbox(uint8_t *output, const uint8_t *input)
{
    output[0] = pgm_read_byte(sbox + input[0]);
    output[1] = pgm_read_byte(sbox + input[1]);
    output[2] = pgm_read_byte(sbox + input[2]);
    output[3] = pgm_read_byte(sbox + input[3]);
}