kgg-dec/third-party/aes/aes.cpp

#include "aes.h"

#include <cstring>

#define Nb 4
#define Nk 4   // The number of 32 bit words in a key.
#define Nr 10  // The number of rounds in AES Cipher.

namespace AES {

/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
typedef uint8_t state_t[4][4];

// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM -
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t sbox[256] = {
    // 0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F
    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 const uint8_t rsbox[256] = {
    0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, 0x7c, 0xe3, 0x39,
    0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2,
    0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76,
    0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc,
    0x5d, 0x65, 0xb6, 0x92, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d,
    0x84, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, 0xd0, 0x2c,
    0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, 0x3a, 0x91, 0x11, 0x41, 0x4f,
    0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85,
    0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62,
    0x0e, 0xaa, 0x18, 0xbe, 0x1b, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd,
    0x5a, 0xf4, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, 0x60,
    0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, 0xa0, 0xe0, 0x3b, 0x4d,
    0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6,
    0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d};

// The round constant word array, Rcon[i], contains the values given by
// x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
static const uint8_t Rcon[11] = {0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};

/*
 * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES-C/pull/12),
 * that you can remove most of the elements in the Rcon array, because they are unused.
 *
 * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
 *
 * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed),
 *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
 */

inline uint8_t getSBoxValue(const uint8_t num) {
    return sbox[num];
}

// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key) {
    unsigned i, k;
    uint8_t temp_arr[4];  // Used for the column/row operations

    // The first round key is the key itself.
    for (i = 0; i < Nk; ++i) {
        RoundKey[i * 4 + 0] = Key[i * 4 + 0];
        RoundKey[i * 4 + 1] = Key[i * 4 + 1];
        RoundKey[i * 4 + 2] = Key[i * 4 + 2];
        RoundKey[i * 4 + 3] = Key[i * 4 + 3];
    }

    // All other "round keys" are found from the previous round keys.
    for (i = Nk; i < Nb * (Nr + 1); ++i) {
        {
            k = (i - 1) * 4;
            temp_arr[0] = RoundKey[k + 0];
            temp_arr[1] = RoundKey[k + 1];
            temp_arr[2] = RoundKey[k + 2];
            temp_arr[3] = RoundKey[k + 3];
        }

        if (i % Nk == 0) {
            // This function shifts the 4 bytes in a word to the left once.
            // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

            // Function RotWord()
            {
                const uint8_t u8tmp = temp_arr[0];
                temp_arr[0] = temp_arr[1];
                temp_arr[1] = temp_arr[2];
                temp_arr[2] = temp_arr[3];
                temp_arr[3] = u8tmp;
            }

            // SubWord() is a function that takes a four-byte input word and
            // applies the S-box to each of the four bytes to produce an output word.

            // Function SubWord()
            {
                temp_arr[0] = getSBoxValue(temp_arr[0]);
                temp_arr[1] = getSBoxValue(temp_arr[1]);
                temp_arr[2] = getSBoxValue(temp_arr[2]);
                temp_arr[3] = getSBoxValue(temp_arr[3]);
            }

            temp_arr[0] = temp_arr[0] ^ Rcon[i / Nk];
        }

        // AES256 code was here.

        const unsigned j = i * 4;
        k = (i - Nk) * 4;
        RoundKey[j + 0] = RoundKey[k + 0] ^ temp_arr[0];
        RoundKey[j + 1] = RoundKey[k + 1] ^ temp_arr[1];
        RoundKey[j + 2] = RoundKey[k + 2] ^ temp_arr[2];
        RoundKey[j + 3] = RoundKey[k + 3] ^ temp_arr[3];
    }
}

bool AES_init_ctx_iv(AES_ctx* ctx, const uint8_t* key, const uint8_t* iv) {
    KeyExpansion(ctx->RoundKey, key);
    memcpy(ctx->Iv, iv, kBlockLen);
    return true;
}

// This function adds the round key to state.
// The round key is added to the state by an XOR function.
void AddRoundKey(uint8_t round, state_t* state, const uint8_t* RoundKey) {
    for (uint8_t i = 0; i < 4; ++i) {
        for (uint8_t j = 0; j < 4; ++j) {
            (*state)[i][j] ^= RoundKey[round * Nb * 4 + i * Nb + j];
        }
    }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
void SubBytes(state_t* state) {
    for (uint8_t i = 0; i < 4; ++i) {
        for (uint8_t j = 0; j < 4; ++j) {
            (*state)[j][i] = getSBoxValue((*state)[j][i]);
        }
    }
}

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
void ShiftRows(state_t* state) {
    // Rotate first row 1 column to left
    uint8_t temp = (*state)[0][1];
    (*state)[0][1] = (*state)[1][1];
    (*state)[1][1] = (*state)[2][1];
    (*state)[2][1] = (*state)[3][1];
    (*state)[3][1] = temp;

    // Rotate second row 2 columns to left
    temp = (*state)[0][2];
    (*state)[0][2] = (*state)[2][2];
    (*state)[2][2] = temp;

    temp = (*state)[1][2];
    (*state)[1][2] = (*state)[3][2];
    (*state)[3][2] = temp;

    // Rotate third row 3 columns to left
    temp = (*state)[0][3];
    (*state)[0][3] = (*state)[3][3];
    (*state)[3][3] = (*state)[2][3];
    (*state)[2][3] = (*state)[1][3];
    (*state)[1][3] = temp;
}

inline uint8_t xtime(uint8_t x) {
    return x << 1 ^ (x >> 7 & 1) * 0x1b;
}

// MixColumns function mixes the columns of the state matrix
void MixColumns(state_t* state) {
    for (uint8_t i = 0; i < 4; ++i) {
        uint8_t t = (*state)[i][0];
        uint8_t Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
        uint8_t Tm = (*state)[i][0] ^ (*state)[i][1];
        Tm = xtime(Tm);
        (*state)[i][0] ^= Tm ^ Tmp;
        Tm = (*state)[i][1] ^ (*state)[i][2];
        Tm = xtime(Tm);
        (*state)[i][1] ^= Tm ^ Tmp;
        Tm = (*state)[i][2] ^ (*state)[i][3];
        Tm = xtime(Tm);
        (*state)[i][2] ^= Tm ^ Tmp;
        Tm = (*state)[i][3] ^ t;
        Tm = xtime(Tm);
        (*state)[i][3] ^= Tm ^ Tmp;
    }
}

// Multiply is used to multiply numbers in the field GF(2^8)
// Note: The last call to xtime() is unneeded, but often ends up generating a smaller binary
//       The compiler seems to be able to vectorize the operation better this way.
//       See https://github.com/kokke/tiny-AES-c/pull/34
#if MULTIPLY_AS_A_FUNCTION
static uint8_t Multiply(uint8_t x, uint8_t y) {
    return (((y & 1) * x) ^ ((y >> 1 & 1) * xtime(x)) ^ ((y >> 2 & 1) * xtime(xtime(x))) ^
            ((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^
            ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x)))))); /* this last call to xtime() can be omitted */
}
#else
#define Multiply(x, y)                                                              \
    (((y & 1) * x) ^ ((y >> 1 & 1) * xtime(x)) ^ ((y >> 2 & 1) * xtime(xtime(x))) ^ \
     ((y >> 3 & 1) * xtime(xtime(xtime(x)))) ^ ((y >> 4 & 1) * xtime(xtime(xtime(xtime(x))))))

#endif

inline uint8_t getSBoxInvert(uint8_t num) {
    return rsbox[num];
}

// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
void InvMixColumns(state_t* state) {
    for (int i = 0; i < 4; ++i) {
        uint8_t a = (*state)[i][0];
        uint8_t b = (*state)[i][1];
        uint8_t c = (*state)[i][2];
        uint8_t d = (*state)[i][3];

        (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
        (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
        (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
        (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
    }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
void InvSubBytes(state_t* state) {
    for (uint8_t i = 0; i < 4; ++i) {
        for (uint8_t j = 0; j < 4; ++j) {
            (*state)[j][i] = getSBoxInvert((*state)[j][i]);
        }
    }
}

void InvShiftRows(state_t* state) {
    // Rotate first row 1 column to right
    uint8_t temp = (*state)[3][1];
    (*state)[3][1] = (*state)[2][1];
    (*state)[2][1] = (*state)[1][1];
    (*state)[1][1] = (*state)[0][1];
    (*state)[0][1] = temp;

    // Rotate second row 2 columns to right
    temp = (*state)[0][2];
    (*state)[0][2] = (*state)[2][2];
    (*state)[2][2] = temp;

    temp = (*state)[1][2];
    (*state)[1][2] = (*state)[3][2];
    (*state)[3][2] = temp;

    // Rotate third row 3 columns to right
    temp = (*state)[0][3];
    (*state)[0][3] = (*state)[1][3];
    (*state)[1][3] = (*state)[2][3];
    (*state)[2][3] = (*state)[3][3];
    (*state)[3][3] = temp;
}

// Cipher is the main function that encrypts the PlainText.
void Cipher(state_t* state, const uint8_t* RoundKey) {
    uint8_t round = 0;

    // Add the First round key to the state before starting the rounds.
    AddRoundKey(0, state, RoundKey);

    // There will be Nr rounds.
    // The first Nr-1 rounds are identical.
    // These Nr rounds are executed in the loop below.
    // Last one without MixColumns()
    for (round = 1;; ++round) {
        SubBytes(state);
        ShiftRows(state);
        if (round == Nr) {
            break;
        }
        MixColumns(state);
        AddRoundKey(round, state, RoundKey);
    }
    // Add round key to last round
    AddRoundKey(Nr, state, RoundKey);
}

void InvCipher(state_t* state, const uint8_t* RoundKey) {
    uint8_t round = 0;

    // Add the First round key to the state before starting the rounds.
    AddRoundKey(Nr, state, RoundKey);

    // There will be Nr rounds.
    // The first Nr-1 rounds are identical.
    // These Nr rounds are executed in the loop below.
    // Last one without InvMixColumn()
    for (round = Nr - 1;; --round) {
        InvShiftRows(state);
        InvSubBytes(state);
        AddRoundKey(round, state, RoundKey);
        if (round == 0) {
            break;
        }
        InvMixColumns(state);
    }
}

inline void XorWithIv(uint8_t* buf, const uint8_t* Iv) {
    for (uint8_t i = 0; i < kBlockLen; ++i)  // The block in AES is always 128bit no matter the key size
    {
        buf[i] ^= Iv[i];
    }
}

size_t AES_CBC_encrypt_buffer(AES_ctx* ctx, uint8_t* buf, size_t length) {
    uint8_t* Iv = ctx->Iv;
    for (size_t i = 0; i < length; i += kBlockLen) {
        XorWithIv(buf, Iv);
        Cipher(reinterpret_cast<state_t*>(buf), ctx->RoundKey);
        Iv = buf;
        buf += kBlockLen;
    }
    /* store Iv in ctx for next call */
    memcpy(ctx->Iv, Iv, kBlockLen);
    return length;
}

size_t AES_CBC_decrypt_buffer(AES_ctx* ctx, uint8_t* buf, size_t length) {
    for (size_t i = 0; i < length; i += kBlockLen) {
        uint8_t storeNextIv[kBlockLen];
        memcpy(storeNextIv, buf, kBlockLen);
        InvCipher(reinterpret_cast<state_t*>(buf), ctx->RoundKey);
        XorWithIv(buf, ctx->Iv);
        memcpy(ctx->Iv, storeNextIv, kBlockLen);
        buf += kBlockLen;
    }
    return length;
}

}  // namespace AES