/*
 * Copyright (C) 2022 - 2026, Stephan Mueller <smueller@chronox.de>
 *
 * License: see LICENSE file in root directory
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR 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 NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */
/*
 * This code is derived in parts from the code distribution provided with
 * https://github.com/kokke/tiny-AES-c
 *
 * This is free and unencumbered software released into the public domain.
 */
/*
 * AES C implementation using S-BOX
 *
 * This implementation is implements a side-channel-resistant key handling,
 * but does not prevent side-channels regarding the plaintext or ciphertext.
 * Furthermore it is decently fast compared to the full side-channel-resistant
 * implementation.
 */

#define AES_SBOX

#include "aes_internal.h"
#include "aes_scr_helper.h"
#include "alignment.h"
#include "bitshift.h"
#include "conv_be_le.h"
#include "ext_headers_internal.h"
#include "lc_aes.h"
#include "rotate.h"
#include "timecop.h"
#include "visibility.h"
#include "xor.h"

/*
 * When enabled, it uses the setkey implementation from aes_ct which is
 * side-channel free and works on big-endian systems
 */
#define AES_USE_CT_KEYEXPANSION

/*
 * When enabled, the code uses the SBox-free implementation of the key expansion
 * code. This code is significantly more inefficient, but reduces side channels.
 * Although it reduces side channels, it is not free of it. If you want to have
 * side-channel free ciphers, use others like Ascon or Ascon-Keccak.
 */
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
#define AES_SIDE_CHANNEL_RESISTANT_KEYEXPANSION
#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
#undef AES_SIDE_CHANNEL_RESISTANT_KEYEXPANSION /* Big-endian support missing */
#else
#error "Endianess not defined"
#endif

/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/

LC_FIPS_RODATA_SECTION
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
};

LC_FIPS_RODATA_SECTION
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
};

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

#ifdef AES_USE_CT_KEYEXPANSION

void aes_setkey_c(struct aes_block_ctx *ctx, const uint8_t *key)
{
	aes_setkey_ct(ctx, key);
}

#else /* AES_USE_CT_KEYEXPANSION */

#ifdef AES_SIDE_CHANNEL_RESISTANT_KEYEXPANSION

static void aes_setkey(struct aes_block_ctx *ctx, const uint8_t *key)
{
	unsigned int i;
	uint32_t x;
	uint32_t *w = (uint32_t *)ctx->round_key;
	uint32_t rcon = 1;

	if (aligned(key, sizeof(uint32_t) - 1)) {
		for (i = 0; i < ctx->nk; i++) {
			/*
			 * We can ignore the alignment warning as we checked
			 * for proper alignment.
			 */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
			w[i] = ((uint32_t *)key)[i];
#pragma GCC diagnostic pop
		}
	} else {
		for (i = 0; i < ctx->nk; i++)
			w[i] = ptr_to_le32(key + (i * sizeof(uint32_t)));
	}

	for (i = ctx->nk; i < (unsigned int)(Nb * (ctx->nr + 1)); i++) {
		x = w[i - 1];

		/* Shut up clang-scan */
		if (!ctx->nk)
			break;

		if ((i % ctx->nk) == 0) {
			x = ror32(x, 8);
			x = aes_sub_word(x) ^ rcon;
			rcon = gf_mul2(rcon);
		} else if ((ctx->nk > 6) && ((i % ctx->nk) == 4)) {
			x = aes_sub_word(x);
		}
		w[i] = w[i - ctx->nk] ^ x;
	}
}
void aes_setkey_c(struct aes_block_ctx *block_ctx, const uint8_t *Key)
{
	aes_setkey(block_ctx, Key);
}

#else /* AES_SIDE_CHANNEL_RESISTANT_KEYEXPANSION */

/*
 * 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)
 *
 * 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."
 */
LC_FIPS_RODATA_SECTION
static const uint8_t Rcon[11] = { 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10,
				  0x20, 0x40, 0x80, 0x1b, 0x36 };

/*
 * This function produces Nb(Nr+1) round keys. The round keys are used in each
 * round to decrypt the states.
 */
void aes_setkey_c(struct aes_block_ctx *block_ctx, const uint8_t *Key)
{
	uint8_t Nk = block_ctx->nk;
	uint8_t Nr = block_ctx->nr;
	uint8_t *RoundKey = (uint8_t *)block_ctx->round_key;
	unsigned int i, j, k;
	uint8_t tempa[4]; // Used for the column/row operations

	if (!Nk)
		return;

	// 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 + 1U); ++i) {
		{
			k = (i - 1) * 4;
			tempa[0] = RoundKey[k + 0];
			tempa[1] = RoundKey[k + 1];
			tempa[2] = RoundKey[k + 2];
			tempa[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 = tempa[0];
				tempa[0] = tempa[1];
				tempa[1] = tempa[2];
				tempa[2] = tempa[3];
				tempa[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()
			{
				tempa[0] = getSBoxValue(tempa[0]);
				tempa[1] = getSBoxValue(tempa[1]);
				tempa[2] = getSBoxValue(tempa[2]);
				tempa[3] = getSBoxValue(tempa[3]);
			}

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

		if (Nk == 8 && (i % Nk == 4)) {
			// Function Subword()
			{
				tempa[0] = getSBoxValue(tempa[0]);
				tempa[1] = getSBoxValue(tempa[1]);
				tempa[2] = getSBoxValue(tempa[2]);
				tempa[3] = getSBoxValue(tempa[3]);
			}
		}

		j = i * 4;
		k = (i - Nk) * 4;
		RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
		RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
		RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
		RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
	}
}
#endif /* AES_SIDE_CHANNEL_RESISTANT_KEYEXPANSION */

#endif /* AES_USE_CT_KEYEXPANSION */

/*
 * This function adds the round key to state.
 * The round key is added to the state by an XOR function.
 */
static void aes_add_round_key(uint8_t round, state_t *state,
			      const uint8_t *RoundKey)
{
	uint8_t i, j;

	for (i = 0; i < 4; ++i) {
		//xor_32((*state)[i], &RoundKey[(round * Nb * 4) + (i * Nb)], 4);
		for (j = 0; j < 4; ++j) {
			(*state)[i][j] ^=
				RoundKey[(round * Nb * 4) + (i * Nb) + j];
		}
	}

	/*
	 * Timecop: Once the round key is XORed with the state (originating
	 * from the plaintext or ciphertext and perhaps already partially
	 * processed by previous rounds), any lookup using this state data
	 * in the SBox is not considered to reveal a timing channel to
	 * resolve the key / round key. Thus, let us unmark this memory.
	 */
	unpoison(state, sizeof(state_t));
}

/*
 * The aes_sub_bytes Function Substitutes the values in the
 * state matrix with values in an S-box.
 */
static void aes_sub_bytes(state_t *state)
{
	uint8_t i, j;

	for (i = 0; i < 4; ++i) {
		for (j = 0; j < 4; ++j)
			(*state)[j][i] = getSBoxValue((*state)[j][i]);
	}
}

/*
 * The aes_shift_rows() 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.
 */
static void aes_shift_rows(state_t *state)
{
	uint8_t temp;

	// Rotate first row 1 columns to left
	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;
}

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

/* aes_mix_columns function mixes the columns of the state matrix */
static void aes_mix_columns(state_t *state)
{
	uint8_t i;
	uint8_t Tmp, Tm, t;

	for (i = 0; i < 4; ++i) {
		t = (*state)[i][0];
		Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^
		      (*state)[i][3];
		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
 */
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)))) ^
		/* this last call to xtime() can be omitted */
		((y >> 4 & 1) * xtime(xtime(xtime(xtime(x))))));
}

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

/*
 * aes_mix_columns 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.
 */
static void Invaes_mix_columns(state_t *state)
{
	int i;
	uint8_t a, b, c, d;

	for (i = 0; i < 4; ++i) {
		a = (*state)[i][0];
		b = (*state)[i][1];
		c = (*state)[i][2];
		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 aes_sub_bytes Function Substitutes the values in the
 * state matrix with values in an S-box.
 */
static void Invaes_sub_bytes(state_t *state)
{
	uint8_t i, j;

	for (i = 0; i < 4; ++i) {
		for (j = 0; j < 4; ++j)
			(*state)[j][i] = getSBoxInvert((*state)[j][i]);
	}
}

static void Invaes_shift_rows(state_t *state)
{
	uint8_t temp;

	// Rotate first row 1 columns to right
	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 aes_encrypt_c(state_t *state, const struct aes_block_ctx *block_ctx)
{
	const uint8_t *RoundKey = (uint8_t *)block_ctx->round_key;
	uint8_t Nr = block_ctx->nr;
	uint8_t round = 0;

	// Add the First round key to the state before starting the rounds.
	aes_add_round_key(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 aes_mix_columns()
	for (round = 1;; ++round) {
		aes_sub_bytes(state);
		aes_shift_rows(state);
		if (round == Nr)
			break;
		aes_mix_columns(state);
		aes_add_round_key(round, state, RoundKey);
	}
	// Add round key to last round
	aes_add_round_key(Nr, state, RoundKey);
}

void aes_decrypt_c(state_t *state, const struct aes_block_ctx *block_ctx)
{
	const uint8_t *RoundKey = (uint8_t *)block_ctx->round_key;
	uint8_t Nr = block_ctx->nr;
	uint8_t round = 0;

	// Add the First round key to the state before starting the rounds.
	aes_add_round_key(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) {
		Invaes_shift_rows(state);
		Invaes_sub_bytes(state);
		aes_add_round_key(round, state, RoundKey);
		if (round == 0)
			break;
		Invaes_mix_columns(state);
	}
}
