/*
 * DECT Standard Authentication Algorithm
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Copyright (c) 2009 Matthias Wenzel <dect at mazzoo dot de>
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <stdint.h>

#include <dect/auth.h>
#include <libdect.h>
#include <utils.h>

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

static void bitperm(uint8_t start, uint8_t step, uint8_t *key)
{
	uint8_t copy[8];
	unsigned int i;

	memcpy(copy, key, 8);
	memset(key, 0, 8);

	for (i = 0; i < 64; i++) {
		key[start/8] |= ((copy[i / 8] & (1 << (i % 8))) >>
				(i % 8)) << (start % 8);
		start += step;
		start %= 64;
	}
}

static const uint8_t mix_factor[3][8] = {
	{ 2, 2, 2, 2, 3, 3, 3, 3},
	{ 2, 2, 3, 3, 2, 2, 3, 3},
	{ 2, 3, 2, 3, 2, 3, 2, 3},
};

static const uint8_t mix_index[3][8] = {
	{ 4, 5, 6, 7, 0, 1, 2, 3},
	{ 2, 3, 0, 1, 6, 7, 4, 5},
	{ 1, 0, 3, 2, 5, 4, 7, 6},
};

static void mix(uint8_t start, uint8_t alg, uint8_t *key)
{
	uint8_t copy[8];
	unsigned int i;

	memcpy(copy, key, 8);
	for (i = 0; i < 8; i++)
		key[i] = copy[mix_index[alg][i]] + mix_factor[alg][i] * copy[i];
}

static void mix1(uint8_t *key)
{
	mix(4, 0, key);
}

static void mix2(uint8_t *key)
{
	mix(2, 1, key);
}

static void mix3(uint8_t *key)
{
	mix(1, 2, key);
}

static void sub(uint8_t *s, uint8_t *t)
{
	unsigned int i;

	for (i = 0; i < 8; i++)
		s[i] = sbox[s[i] ^ t[i]];
}

/* return in s */
static void cassable(uint8_t start, uint8_t step, uint8_t *t, uint8_t *s)
{
	unsigned int i;

	for (i = 0; i < 2; i++) {
		bitperm(start, step, t);
		sub(s, t);
		mix1(s);

		bitperm(start, step, t);
		sub(s, t);
		mix2(s);

		bitperm(start, step, t);
		sub(s, t);
		mix3(s);
	}
}

/* return in rand, modifies key */
static void step1(uint8_t *rand, uint8_t *key)
{
	uint8_t tmp[8];

	memcpy(tmp, rand, 8);

	cassable(46, 35, tmp, key);
	cassable(25, 47, key, rand);

	memcpy(key, rand, 8);
}

static void step2(uint8_t *rand, uint8_t *key)
{
	uint8_t tmp[8];

	memcpy(tmp, rand, 8);

	cassable(60, 27, tmp, key);
	cassable(55, 39, key, rand);

	memcpy(key, rand, 8);
}

static void rev(uint8_t *v, uint8_t n)
{
	unsigned int i;
	uint8_t tmp;

	for (i = 0; i < n / 2; i++) {
		tmp	     = v[i];
		v[i]	     = v[n - i - 1];
		v[n - i - 1] = tmp;
	}
}

static void dsaa_main(const uint8_t *k, const uint8_t *r, uint8_t *e)
{
	uint8_t key[16];
	uint8_t rand[8];
	uint8_t a[8];
	uint8_t b[8];

	memcpy(key, k, sizeof(key));
	rev(key, 16);

	memcpy(&rand, r, sizeof(rand));
	rev(rand, 8);

	step1(rand, key + 4);
	memcpy(a, key + 4, 8);

	memcpy(key + 4, key + 12, 4);
	memcpy(b, a, 8);
	step2(b, key);

	rev(a, 8);
	rev(key, 4);
	rev(key + 4, 4);

	memcpy(e, key + 4, 4);
	memcpy(e + 4, a, 8);
	memcpy(e + 12, key, 4);
}

const struct dect_aalg dect_dsaa_aalg = {
	.type		= DECT_AUTH_DSAA,
	.d1_len		= 16,
	.d2_len		= 8,
	.calc		= dsaa_main,
};