/* Rijndael Block Cipher - rijndael.c

 Written by Mike Scott 21st April 1999
 mike@compapp.dcu.ie

 Permission for free direct or derivative use is granted subject
 to compliance with any conditions that the originators of the
 algorithm place on its exploitation.

 */

#include <stdio.h>
#include <string.h>

/* GCC 11 false positives */
#if __GNUC__ > 11
#pragma GCC diagnostic ignored "-Wstringop-overflow"
#endif

#define u8 unsigned char	   /* 8 bits  */
#define u32 unsigned long	   /* 32 bits */
#define u64 unsigned long long

/* rotates x one bit to the left */

#define ROTL(x) (((x)>>7)|((x)<<1))

/* Rotates 32-bit word left by 1, 2 or 3 byte  */

#define ROTL8(x) (((x)<<8)|((x)>>24))
#define ROTL16(x) (((x)<<16)|((x)>>16))
#define ROTL24(x) (((x)<<24)|((x)>>8))

/* Fixed Data */

static u8 InCo[4] = { 0xB, 0xD, 0x9, 0xE }; /* Inverse Coefficients */

static u8 fbsub[256];
static u8 rbsub[256];
static u8 ptab[256], ltab[256];
static u32 ftable[256];
static u32 rtable[256];
static u32 rco[30];

/* Parameter-dependent data */

int Nk, Nb, Nr;
u8 fi[24], ri[24];
u32 fkey[120];
u32 rkey[120];

static inline u32 pack(u8 *b)
{ /* pack bytes into a 32-bit Word */
	return ((u32 ) b[3] << 24) | ((u32 ) b[2] << 16) | ((u32 ) b[1] << 8) | (u32 ) b[0];
}

static inline void unpack(u32 a, u8 *b)
{ /* unpack bytes from a word */
	b[0] = (u8 ) a;
	b[1] = (u8 ) (a >> 8);
	b[2] = (u8 ) (a >> 16);
	b[3] = (u8 ) (a >> 24);
}

static inline u8 xtime(u8 a)
{
	u8 b;
	if (a & 0x80)
		b = 0x1B;
	else b = 0;
	a <<= 1;
	a ^= b;
	return a;
}

static inline u8 bmul(u8 x, u8 y)
{ /* x.y= AntiLog(Log(x) + Log(y)) */
	if (x && y)
		return ptab[(ltab[x] + ltab[y]) % 255];
	else return 0;
}

static inline u32 SubByte(u32 a)
{
	u8 b[4];
	unpack(a, b);
	b[0] = fbsub[b[0]];
	b[1] = fbsub[b[1]];
	b[2] = fbsub[b[2]];
	b[3] = fbsub[b[3]];
	return pack(b);
}

static inline u8 product(u32 x, u32 y)
{ /* dot product of two 4-byte arrays */
	u8 xb[4], yb[4];
	unpack(x, xb);
	unpack(y, yb);
	return bmul(xb[0], yb[0]) ^ bmul(xb[1], yb[1]) ^ bmul(xb[2], yb[2]) ^ bmul(xb[3], yb[3]);
}

static inline u32 InvMixCol(u32 x)
{ /* matrix Multiplication */
	u32 y, m;
	u8 b[4];

	m = pack(InCo);
	b[3] = product(m, x);
	m = ROTL24( m );
	b[2] = product(m, x);
	m = ROTL24( m );
	b[1] = product(m, x);
	m = ROTL24( m );
	b[0] = product(m, x);
	y = pack(b);
	return y;
}

static inline u8 ByteSub(u8 x)
{
	u8 y = ptab[255 - ltab[x]]; /* multiplicative inverse */
	x = y;
	x = ROTL( x );
	y ^= x;
	x = ROTL( x );
	y ^= x;
	x = ROTL( x );
	y ^= x;
	x = ROTL( x );
	y ^= x;
	y ^= 0x63;
	return y;
}

static inline void gentables(void)
{ /* generate tables */
	int i;
	u8 y, b[4];

	/* use 3 as primitive root to generate power and log tables */

	ltab[0] = 0;
	ptab[0] = 1;
	ltab[1] = 0;
	ptab[1] = 3;
	ltab[3] = 1;
	for (i = 2; i < 256; i++)
	{
		ptab[i] = ptab[i - 1] ^ xtime(ptab[i - 1]);
		ltab[ptab[i]] = i;
	}

	/* affine transformation:- each bit is xored with itself shifted one bit */

	fbsub[0] = 0x63;
	rbsub[0x63] = 0;
	for (i = 1; i < 256; i++)
	{
		y = ByteSub((u8 ) i);
		fbsub[i] = y;
		rbsub[y] = i;
	}

	for (i = 0, y = 1; i < 30; i++)
	{
		rco[i] = y;
		y = xtime(y);
	}

	/* calculate forward and reverse tables */
	for (i = 0; i < 256; i++)
	{
		y = fbsub[i];
		b[3] = y ^ xtime(y);
		b[2] = y;
		b[1] = y;
		b[0] = xtime(y);
		ftable[i] = pack(b);

		y = rbsub[i];
		b[3] = bmul(InCo[0], y);
		b[2] = bmul(InCo[1], y);
		b[1] = bmul(InCo[2], y);
		b[0] = bmul(InCo[3], y);
		rtable[i] = pack(b);
	}
}

static inline void gkey(int nb, int nk, char *key)
{ /* blocksize=32*nb bits. Key=32*nk bits */
	/* currently nb,bk = 4, 6 or 8		  */
	/* key comes as 4*Nk bytes			  */
	/* Key Scheduler. Create expanded encryption key */
	int i, j, k, m, N;
	int C1, C2, C3;
	u32 CipherKey[8];

	Nb = nb;
	Nk = nk;

	/* Nr is number of rounds */
	if (Nb >= Nk)
		Nr = 6 + Nb;
	else Nr = 6 + Nk;

	C1 = 1;
	if (Nb < 8)
	{
		C2 = 2;
		C3 = 3;
	}
	else
	{
		C2 = 3;
		C3 = 4;
	}

	/* pre-calculate forward and reverse increments */
	for (m = j = 0; j < nb; j++, m += 3)
	{
		fi[m] = (j + C1) % nb;
		fi[m + 1] = (j + C2) % nb;
		fi[m + 2] = (j + C3) % nb;
		ri[m] = (nb + j - C1) % nb;
		ri[m + 1] = (nb + j - C2) % nb;
		ri[m + 2] = (nb + j - C3) % nb;
	}

	N = Nb * (Nr + 1);

	for (i = j = 0; i < Nk; i++, j += 4)
	{
		CipherKey[i] = pack((u8 *) &key[j]);
	}
	for (i = 0; i < Nk; i++)
		fkey[i] = CipherKey[i];
	for (j = Nk, k = 0; j < N; j += Nk, k++)
	{
		fkey[j] = fkey[j - Nk] ^ SubByte(ROTL24( fkey[j-1] )) ^ rco[k];
		if (Nk <= 6)
		{
			for (i = 1; i < Nk && (i + j) < N; i++)
				fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
		}
		else
		{
			for (i = 1; i < 4 && (i + j) < N; i++)
				fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
			if ((j + 4) < N) fkey[j + 4] = fkey[j + 4 - Nk] ^ SubByte(fkey[j + 3]);
			for (i = 5; i < Nk && (i + j) < N; i++)
				fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
		}

	}

	/* now for the expanded decrypt key in reverse order */

	for (j = 0; j < Nb; j++)
		rkey[j + N - Nb] = fkey[j];
	for (i = Nb; i < N - Nb; i += Nb)
	{
		k = N - Nb - i;
		for (j = 0; j < Nb; j++)
			rkey[k + j] = InvMixCol(fkey[i + j]);
	}
	for (j = N - Nb; j < N; j++)
		rkey[j - N + Nb] = fkey[j];
}

/* There is an obvious time/space trade-off possible here.	 *
 * Instead of just one ftable[], I could have 4, the other	 *
 * 3 pre-rotated to save the ROTL8, ROTL16 and ROTL24 overhead */

static inline void encrypt(char *buff)
{
	int i, j, k, m;
	u32 a[8], b[8], *x, *y, *t;

	for (i = j = 0; i < Nb; i++, j += 4)
	{
		a[i] = pack((u8 *) &buff[j]);
		a[i] ^= fkey[i];
	}
	k = Nb;
	x = a;
	y = b;

	/* State alternates between a and b */
	for (i = 1; i < Nr; i++)
	{ /* Nr is number of rounds. May be odd. */

		/* if Nb is fixed - unroll this next
		 loop and hard-code in the values of fi[]  */

		for (m = j = 0; j < Nb; j++, m += 3)
		{ /* deal with each 32-bit element of the State */
			/* This is the time-critical bit */
			y[j] = fkey[k++] ^ ftable[(u8 ) x[j]] ^ ROTL8( ftable[( u8 )( x[fi[m]] >> 8 )] )
					^ ROTL16( ftable[( u8 )( x[fi[m+1]] >> 16 )] ) ^ ROTL24( ftable[x[fi[m+2]] >> 24] );
		}
		t = x;
		x = y;
		y = t; /* swap pointers */
	}

	/* Last Round - unroll if possible */
	for (m = j = 0; j < Nb; j++, m += 3)
	{
		y[j] = fkey[k++] ^ (u32 ) fbsub[(u8 ) x[j]] ^ ROTL8( ( u32 )fbsub[( u8 )( x[fi[m]] >> 8 )] )
				^ ROTL16( ( u32 )fbsub[( u8 )( x[fi[m+1]] >> 16 )] ) ^ ROTL24( ( u32 )fbsub[x[fi[m+2]] >> 24] );
	}
	for (i = j = 0; i < Nb; i++, j += 4)
	{
		unpack(y[i], (u8 *) &buff[j]);
		x[i] = y[i] = 0; /* clean up stack */
	}
	return;
}

static inline void decrypt(char *buff)
{
	int i, j, k, m;
	u32 a[8], b[8], *x, *y, *t;

	for (i = j = 0; i < Nb; i++, j += 4)
	{
		a[i] = pack((u8 *) &buff[j]);
		a[i] ^= rkey[i];
	}
	k = Nb;
	x = a;
	y = b;

	/* State alternates between a and b */
	for (i = 1; i < Nr; i++)
	{ /* Nr is number of rounds. May be odd. */

		/* if Nb is fixed - unroll this next
		 loop and hard-code in the values of ri[]  */

		for (m = j = 0; j < Nb; j++, m += 3)
		{ /* This is the time-critical bit */
			y[j] = rkey[k++] ^ rtable[(u8 ) x[j]] ^ ROTL8( rtable[( u8 )( x[ri[m]] >> 8 )] )
					^ ROTL16( rtable[( u8 )( x[ri[m+1]] >> 16 )] ) ^ ROTL24( rtable[x[ri[m+2]] >> 24] );
		}
		t = x;
		x = y;
		y = t; /* swap pointers */
	}

	/* Last Round - unroll if possible */
	for (m = j = 0; j < Nb; j++, m += 3)
	{
		y[j] = rkey[k++] ^ (u32 ) rbsub[(u8 ) x[j]] ^ ROTL8( ( u32 )rbsub[( u8 )( x[ri[m]] >> 8 )] )
				^ ROTL16( ( u32 )rbsub[( u8 )( x[ri[m+1]] >> 16 )] ) ^ ROTL24( ( u32 )rbsub[x[ri[m+2]] >> 24] );
	}
	for (i = j = 0; i < Nb; i++, j += 4)
	{
		unpack(y[i], (u8 *) &buff[j]);
		x[i] = y[i] = 0; /* clean up stack */
	}
	return;
}

void aes_set_key(u8 *key)
{
	gentables();
	gkey(4, 4, (char*) key);
}

// CBC mode decryption
void aes_decrypt(u8 *iv, u8 *inbuf, u8 *outbuf, unsigned long long len)
{
	u8 block[16];
	unsigned int blockno = 0, i;

	//printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);

	for (blockno = 0; blockno <= (len / sizeof(block)); blockno++)
	{
		unsigned int fraction;
		if (blockno == (len / sizeof(block))) // last block
		{
			fraction = len % sizeof(block);
			if (fraction == 0) break;
			memset(block, 0, sizeof(block));
		}
		else fraction = 16;

		//	debug_printf("block %d: fraction = %d\n", blockno, fraction);
		memcpy(block, inbuf + blockno * sizeof(block), fraction);
		decrypt((char*) block);
		u8 *ctext_ptr;
		if (blockno == 0)
			ctext_ptr = iv;
		else ctext_ptr = inbuf + (blockno - 1) * sizeof(block);

		for (i = 0; i < fraction; i++)
			outbuf[blockno * sizeof(block) + i] = ctext_ptr[i] ^ block[i];
		//	debug_printf("Block %d output: ", blockno);
		//	hexdump(outbuf + blockno*sizeof(block), 16);
	}
}

// CBC mode encryption
void aes_encrypt(u8 *iv, u8 *inbuf, u8 *outbuf, unsigned long long len)
{
	u8 block[16];
	unsigned int blockno = 0, i;

	//  debug_printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);

	for (blockno = 0; blockno <= (len / sizeof(block)); blockno++)
	{
		unsigned int fraction;
		if (blockno == (len / sizeof(block))) // last block
		{
			fraction = len % sizeof(block);
			if (fraction == 0) break;
			memset(block, 0, sizeof(block));
		}
		else fraction = 16;

		//	debug_printf("block %d: fraction = %d\n", blockno, fraction);
		memcpy(block, inbuf + blockno * sizeof(block), fraction);

		for (i = 0; i < fraction; i++)
			block[i] = inbuf[blockno * sizeof(block) + i] ^ iv[i];

		encrypt((char*) block);
		memcpy(iv, block, sizeof(block));
		memcpy(outbuf + blockno * sizeof(block), block, sizeof(block));
		//	debug_printf("Block %d output: ", blockno);
		//	hexdump(outbuf + blockno*sizeof(block), 16);
	}
}