/******************************************************************************/
/* SlunkCrypt, by LoRd_MuldeR <MuldeR2@GMX.de>                                */
/* This work has been released under the CC0 1.0 Universal license!           */
/******************************************************************************/

/* Internal */
#include "keygen.h"
#include "compiler.h"

/* CRT */
#include <limits.h>

/* Type */
typedef struct
{
	uint64_t hi, lo;
}
uint128_t;

// ==========================================================================
// 128-Bit math support
// ==========================================================================

#if defined(__GNUC__) && defined(__SIZEOF_INT128__)
#  define HAVE_UINT128_SUPPORT 1
#  define PACK_U128(X) ((((__uint128_t)(X).hi) << 64) | (X).lo)
#else
#  pragma message("Compiler does not support 128-bit math -> using fallback!")
#endif

static INLINE void multiply_u128(uint128_t *const out, const uint128_t lhs, const uint128_t rhs)
{
#ifdef HAVE_UINT128_SUPPORT
	const __uint128_t product = PACK_U128(lhs) * PACK_U128(rhs);
	*out = (uint128_t) { product >> 64, product };
#else
	const uint64_t lolo = (lhs.lo & 0xFFFFFFFF) * (rhs.lo & 0xFFFFFFFF);
	const uint64_t hilo = (lhs.lo >> 32U) * (rhs.lo & 0xFFFFFFFF);
	const uint64_t lohi = (lhs.lo & 0xFFFFFFFF) * (rhs.lo >> 32U);
	const uint64_t hihi = (lhs.lo >> 32U) * (rhs.lo >> 32U);
	const uint64_t crss = (lolo >> 32U) + (hilo & 0xFFFFFFFF) + lohi;
	out->hi = (hilo >> 32U) + (crss >> 32) + hihi;
	out->lo = (crss << 32U) | (lolo & 0xFFFFFFFF);
	out->hi += (lhs.hi * rhs.lo) + (lhs.lo * rhs.hi); /* 128x128=128 */
#endif
}

// ==========================================================================
// Hash function
// ==========================================================================

static const uint128_t HASH_OFFSETBASE_128 = { 0x6C62272E07BB0142, 0x62B821756295C58D };
static const uint128_t HASH_MAGICPRIME_128 = { 0x0000000001000000, 0x000000000000013B };

static INLINE void hash_update_u64(uint128_t* const hash, uint64_t value)
{
	size_t i;
	for (i = 0U; i < sizeof(uint64_t); ++i, value >>= CHAR_BIT)
	{
		hash->lo ^= (uint8_t)(value & 0xFF);
		multiply_u128(hash, *hash, HASH_MAGICPRIME_128);
	}
}

static INLINE void hash_update_str(uint128_t *const hash, const uint8_t *const data, const size_t data_len)
{
	size_t i;
	for (i = 0U; i < data_len; ++i)
	{
		hash->lo ^= data[i];
		multiply_u128(hash, *hash, HASH_MAGICPRIME_128);
	}
}

static INLINE uint128_t hash_code(const uint128_t *const seed, const uint8_t *const data, const size_t data_len)
{
	uint128_t hash = HASH_OFFSETBASE_128;
	hash_update_u64(&hash, seed->lo);
	hash_update_u64(&hash, seed->hi);
	hash_update_str(&hash, data, data_len);
	return hash;
}

// ==========================================================================
// Key derivation
// ==========================================================================

static INLINE uint64_t keygen_loop(uint64_t seed, const uint64_t i, const uint8_t *const passwd, const size_t passwd_len, const size_t iterations)
{
	uint128_t hash = { seed, i };
	size_t u;
	for (u = 0U, seed = 0U; u < iterations; ++u)
	{
		hash = hash_code(&hash, passwd, passwd_len);
		seed ^= hash.hi ^ hash.lo;
	}
	return seed;
}

void slunkcrypt_keygen(keydata_t *const key, const uint64_t salt, const uint16_t pepper, const uint8_t *const passwd, const size_t passwd_len, const size_t iterations)
{
	key->a = keygen_loop(salt, 0x162603FA1CDA99D3 + (uint64_t)pepper, passwd, passwd_len, iterations);
	key->b = keygen_loop(salt, 0xBFDEC4A6C1A46E09 + (uint64_t)pepper, passwd, passwd_len, iterations);
	key->c = keygen_loop(salt, 0x6BA17D11624973EE + (uint64_t)pepper, passwd, passwd_len, iterations);
}