#include <string.h>
#include <stdint.h>
#include "AES.h"

//only works with 128 for now

//State is the current 4x4 block (or matrix) pointer
typedef uint8_t* State;
//Byte is a single unsigned byte that is not used as a character or an integer
typedef uint8_t Byte;

static void ExpandKey(const char* cipherKey, char Nk, char* expKey);
static void SubBytes(Byte* val, int len);
static void InvSubBytes(Byte* val, int len);
static void ShiftRows(State state);
static void InvShiftRows(State state);
static void MixColumns(State state);
static void InvMixColumns(State state);
static void AddRoundKey(State state, State roundKey);
static void RotBytes(Byte* val, int len);
static uint8_t GFMultBy2(uint8_t a);
static uint8_t GFMultBy09(uint8_t a);
static uint8_t GFMultBy11(uint8_t a);
static uint8_t GFMultBy13(uint8_t a);
static uint8_t GFMultBy14(uint8_t a);

static const uint8_t Nb = 4;
//Nk is interpreted based on size of key given unless specified
//Nr is Nk + 6 since Nb is always 4

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

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

static const uint8_t rcon[11] = { 0x00, 0x01,   0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36 };

//Hopefully done but todo
void AESEncrypt(const char* plaintext, const char* cipherKey, uint16_t keyLength, char* outCiphertext)
{
    //Expand key
    Byte expandedKey[16 * 11] = {0};
    ExpandKey(cipherKey, 4, expandedKey);

    //Copy plain text to cipher text
    size_t len = strlen(plaintext);
    memcpy(outCiphertext, plaintext, len);

    //Initial round key
    AddRoundKey(outCiphertext, expandedKey);

    //Go through first 10 rounds
    for (int i = 0; i < 10; i++)
    {
        for (State state = outCiphertext; state < outCiphertext + len; state += 16)
        {
            SubBytes(state, 16);
            ShiftRows(state);
            MixColumns(state);
            AddRoundKey(state, &expandedKey[i * 16]);
        }
    }

    //Go through last round
    for (State state = outCiphertext; state < outCiphertext + len; state += 16)
    {
        SubBytes(state, 16);
        ShiftRows(state);
        AddRoundKey(state, &expandedKey[10 * 16]);
    }
}

//BIG TODO
void AESDecrypt(const char* ciphertext, const char* cipherKey, uint16_t keyLength, char* outPlaintext)
{
    //Expand key
    Byte expandedKey[16 * 11] = { 0 };
    ExpandKey(cipherKey, 4, expandedKey);

    //Copy plain text to cipher text
    size_t len = strlen(ciphertext);
    memcpy(outPlaintext, ciphertext, len);

    //Initial round key
    AddRoundKey(outPlaintext, expandedKey);

    //Go through first 10 rounds
    for (int i = 0; i < 10; i++)
    {
        for (State state = outPlaintext; state < outPlaintext + len; state += 16)
        {
            AddRoundKey(state, &expandedKey[i * 16]);
            InvMixColumns(state);
            InvShiftRows(state);
            InvSubBytes(state, 16);
        }
    }

    //Go through last round
    for (State state = outPlaintext; state < outPlaintext + len; state += 16)
    {
        AddRoundKey(state, &expandedKey[10 * 16]);
        InvShiftRows(state);
        InvSubBytes(state, 16);
    }
}

//Expands key to be unique for each round
void ExpandKey(const char* cipherKey, char Nk, char* expKey)
{
    //Re useable temp
    uint32_t temp = 0;

    //Copy key over to first columns of expanded
    memcpy(expKey, cipherKey, Nk * 4);

    //Iterate through columns (Nr = Nk + 6 as long as Nb is 4)
    for (int i = Nk; i < Nb * (Nk + 7); i++)
    {
        //Get the last column
        memcpy(&temp, &expKey[((i - 1) * 4)], 4);

        //If edge column
        if (i % Nk == 0)
        {
            //Rotate, substitute, xor first byte with round constant
            RotBytes(&temp, 4);
            SubBytes(&temp, 4);
            temp = temp ^ rcon[i / Nk];
        }
        else if (Nk == 8 && i % Nk == 4) //If 256 bit key and in middle column
        {
            //Just sub bytes
            SubBytes(&temp, 4);
        }

        //Xor current column with last matrix's corresponding column
        ((uint32_t*)expKey)[i] = ((uint32_t*)expKey)[i - Nk] ^ temp;
    }
}

//Substitutes each byte with sBox[byte]
static void SubBytes(Byte* val, int len)
{
    for (int i = 0; i < len; i++)
        val[i] = sBox[val[i]];
}

//Reverses SubBytes
static void InvSubBytes(Byte* val, int len)
{
    for (int i = 0; i < len; i++)
        val[i] = invSBox[val[i]];
}

//Shift rows of a 4x4 column major byte matrix by r bytes to left
static void ShiftRows(State state)
{
    Byte temp;

    //Shift row 1
    temp = state[4 * 1 + 0];
    state[4 * 1 + 0] = state[4 * 1 + 1];
    state[4 * 1 + 1] = state[4 * 1 + 2];
    state[4 * 1 + 2] = state[4 * 1 + 3];
    state[4 * 1 + 3] = temp;

    //Shift row 2
    temp = state[4 * 2 + 0];
    state[4 * 2 + 0] = state[4 * 2 + 2];
    state[4 * 2 + 2] = temp;

    temp = state[4 * 2 + 1];
    state[4 * 2 + 1] = state[4 * 2 + 3];
    state[4 * 2 + 3] = temp;

    //Shift row 3
    temp = state[4 * 3 + 0];
    state[4 * 3 + 0] = state[4 * 3 + 3];
    state[4 * 3 + 2] = state[4 * 3 + 1];
    state[4 * 3 + 3] = state[4 * 3 + 2];
    state[4 * 3 + 1] = temp;
}

//Shift rows of a 4x4 column major byte matrix by r bytes to right
static void InvShiftRows(State state)
{
    Byte temp;

    //Shift row 1
    temp = state[4 * 1 + 3];
    state[4 * 1 + 1] = state[4 * 1 + 0];
    state[4 * 1 + 2] = state[4 * 1 + 1];
    state[4 * 1 + 3] = state[4 * 1 + 2];
    state[4 * 1 + 0] = temp;

    //Shift row 2
    temp = state[4 * 2 + 2];
    state[4 * 2 + 2] = state[4 * 2 + 0];
    state[4 * 2 + 0] = temp;

    temp = state[4 * 2 + 3];
    state[4 * 2 + 3] = state[4 * 2 + 1];
    state[4 * 2 + 1] = temp;

    //Shift row 3
    temp = state[4 * 1 + 0];
    state[4 * 1 + 0] = state[4 * 1 + 1];
    state[4 * 1 + 1] = state[4 * 1 + 2];
    state[4 * 1 + 2] = state[4 * 1 + 3];
    state[4 * 1 + 3] = temp;
}

//Multiply each column in block as a vector the by fixed AES matrix created from polynomial (0x03x^3 + 0x01x^2 + 0x01x + 0x02) in GF(2^8)
static void MixColumns(State state)
{
    uint8_t Tmp = 0x0;
    uint8_t Tm = 0x0;
    uint8_t* a = NULL;

    //Iterate columns
    for (int j = 0; j < 4; j++)
    {
        //Get current column
        a = &state[j * 4];

        //Multiply column as a vector by the fixed AES matrix in GF(2^8)
        //Found this from here, and modified the style a tad:
        //https://csrc.nist.gov/csrc/media/projects/cryptographic-standards-and-guidelines/documents/aes-development/rijndael-ammended.pdf
        Tmp = a[0] ^ a[1] ^ a[2] ^ a[3];

        Tm = a[0] ^ a[1];
        Tm = GFMultBy2(Tm);
        a[0] ^= Tm ^ Tmp;

        Tm = a[1] ^ a[2];
        Tm = GFMultBy2(Tm);
        a[1] ^= Tm ^ Tmp;

        Tm = a[2] ^ a[3];
        Tm = GFMultBy2(Tm);
        a[2] ^= Tm ^ Tmp;

        Tm = a[3] ^ a[0];
        Tm = GFMultBy2(Tm);
        a[3] ^= Tm ^ Tmp;
    }
}

//Multiply each column in block as a vector the by inverse fixed AES matrix created from polynomial (0x0Bx^3 + 0x0Dx^2 + 0x09x + 0x0E) in GF(2^8)
static void InvMixColumns(State state)
{
    uint8_t* a = NULL;

    //Iterate columns
    for (int j = 0; j < 4; j++)
    {
        //Get current column
        a = &state[j * 4];

        //Multiply column as a vector by the fixed AES inverse matrix in GF(2^8)
        a[0] = GFMultBy14(a[0]) ^ GFMultBy11(a[1]) ^ GFMultBy13(a[2]) ^ GFMultBy09(a[3]);
        a[1] = GFMultBy09(a[0]) ^ GFMultBy14(a[1]) ^ GFMultBy11(a[2]) ^ GFMultBy13(a[3]);
        a[2] = GFMultBy13(a[0]) ^ GFMultBy09(a[1]) ^ GFMultBy14(a[2]) ^ GFMultBy11(a[3]);
        a[3] = GFMultBy11(a[0]) ^ GFMultBy13(a[1]) ^ GFMultBy09(a[2]) ^ GFMultBy14(a[3]);
    }
}

//Xor 128 bit value with 128 bit exp key
static void AddRoundKey(State state, State roundKey)
{
    //Xor in as few commands as possible
    ((int64_t*)state)[0] ^= ((int64_t*)roundKey)[0];
    ((int64_t*)state)[1] ^= ((int64_t*)roundKey)[1];
}

//Rotates bytes 1 byte to the left, the first will be wrapped
static void RotBytes(Byte* val, int len)
{
    Byte c = val[0];
    memcpy(val + 1, val, len - 1);
    val[len - 1] = c;
}

//Multiplies polynomial by 0x02 in the field GF(2^8)
static uint8_t GFMultBy2(uint8_t a)
{
    //This is done by performing a left shift one bit,
    //if the msbit was 1, it will XOR 0x1B
    return (a << 1) ^ (((a >> 7) & 0x01) * 0x1B);
}

//The following operations found from:
//https://crypto.stackexchange.com/questions/2569/how-does-one-implement-the-inverse-of-aes-mixcolumns

//Multiplies polynomial by 0x09 in the field GF(2^8)
static uint8_t GFMultBy09(uint8_t a)
{
    return GFMultBy2(GFMultBy2(GFMultBy2(a))) ^ a;
}

//Multiplies polynomial by 0x0B in the field GF(2^8)
static uint8_t GFMultBy11(uint8_t a)
{
    return GFMultBy2(GFMultBy2(GFMultBy2(a)) ^ a) ^ a;
}

//Multiplies polynomial by 0x0D in the field GF(2^8)
static uint8_t GFMultBy13(uint8_t a)
{
    return GFMultBy2(GFMultBy2(GFMultBy2(a) ^ a)) ^ a;
}

//Multiplies polynomial by 0x0E in the field GF(2^8)
static uint8_t GFMultBy14(uint8_t a)
{
    return GFMultBy2(GFMultBy2(GFMultBy2(a) ^ a) ^ a);
}