/*
 * Copyright (C) 2006-2010 Vincent Hanquez <vincent@snarc.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 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 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <string.h>
#include <stdio.h>
#include "bitfn.h"
#include "md2.h"

void md2_init(struct md2_ctx *ctx)
{
	memset(ctx, 0, sizeof(*ctx));
	ctx->sz = 0ULL;
}

static uint8_t S_table[]  = {
	0x29, 0x2E, 0x43, 0xC9, 0xA2, 0xD8, 0x7C, 0x01, 0x3D, 0x36, 0x54, 0xA1, 0xEC, 0xF0, 0x06, 0x13, 
	0x62, 0xA7, 0x05, 0xF3, 0xC0, 0xC7, 0x73, 0x8C, 0x98, 0x93, 0x2B, 0xD9, 0xBC, 0x4C, 0x82, 0xCA, 
	0x1E, 0x9B, 0x57, 0x3C, 0xFD, 0xD4, 0xE0, 0x16, 0x67, 0x42, 0x6F, 0x18, 0x8A, 0x17, 0xE5, 0x12, 
	0xBE, 0x4E, 0xC4, 0xD6, 0xDA, 0x9E, 0xDE, 0x49, 0xA0, 0xFB, 0xF5, 0x8E, 0xBB, 0x2F, 0xEE, 0x7A, 
	0xA9, 0x68, 0x79, 0x91, 0x15, 0xB2, 0x07, 0x3F, 0x94, 0xC2, 0x10, 0x89, 0x0B, 0x22, 0x5F, 0x21,
	0x80, 0x7F, 0x5D, 0x9A, 0x5A, 0x90, 0x32, 0x27, 0x35, 0x3E, 0xCC, 0xE7, 0xBF, 0xF7, 0x97, 0x03, 
	0xFF, 0x19, 0x30, 0xB3, 0x48, 0xA5, 0xB5, 0xD1, 0xD7, 0x5E, 0x92, 0x2A, 0xAC, 0x56, 0xAA, 0xC6, 
	0x4F, 0xB8, 0x38, 0xD2, 0x96, 0xA4, 0x7D, 0xB6, 0x76, 0xFC, 0x6B, 0xE2, 0x9C, 0x74, 0x04, 0xF1, 
	0x45, 0x9D, 0x70, 0x59, 0x64, 0x71, 0x87, 0x20, 0x86, 0x5B, 0xCF, 0x65, 0xE6, 0x2D, 0xA8, 0x02, 
	0x1B, 0x60, 0x25, 0xAD, 0xAE, 0xB0, 0xB9, 0xF6, 0x1C, 0x46, 0x61, 0x69, 0x34, 0x40, 0x7E, 0x0F, 
	0x55, 0x47, 0xA3, 0x23, 0xDD, 0x51, 0xAF, 0x3A, 0xC3, 0x5C, 0xF9, 0xCE, 0xBA, 0xC5, 0xEA, 0x26, 
	0x2C, 0x53, 0x0D, 0x6E, 0x85, 0x28, 0x84, 0x09, 0xD3, 0xDF, 0xCD, 0xF4, 0x41, 0x81, 0x4D, 0x52, 
	0x6A, 0xDC, 0x37, 0xC8, 0x6C, 0xC1, 0xAB, 0xFA, 0x24, 0xE1, 0x7B, 0x08, 0x0C, 0xBD, 0xB1, 0x4A, 
	0x78, 0x88, 0x95, 0x8B, 0xE3, 0x63, 0xE8, 0x6D, 0xE9, 0xCB, 0xD5, 0xFE, 0x3B, 0x00, 0x1D, 0x39, 
	0xF2, 0xEF, 0xB7, 0x0E, 0x66, 0x58, 0xD0, 0xE4, 0xA6, 0x77, 0x72, 0xF8, 0xEB, 0x75, 0x4B, 0x0A, 
	0x31, 0x44, 0x50, 0xB4, 0x8F, 0xED, 0x1F, 0x1A, 0xDB, 0x99, 0x8D, 0x33, 0x9F, 0x11, 0x83, 0x14
};

static uint8_t *padding_table[] = {
	"",
	"\x1",
	"\x2\x2",
	"\x3\x3\x3",
	"\x4\x4\x4\x4",
	"\x5\x5\x5\x5\x5",
	"\x6\x6\x6\x6\x6\x6",
	"\x7\x7\x7\x7\x7\x7\x7",
	"\x8\x8\x8\x8\x8\x8\x8\x8",
	"\x9\x9\x9\x9\x9\x9\x9\x9\x9",
	"\xa\xa\xa\xa\xa\xa\xa\xa\xa\xa",
	"\xb\xb\xb\xb\xb\xb\xb\xb\xb\xb\xb",
	"\xc\xc\xc\xc\xc\xc\xc\xc\xc\xc\xc\xc",
	"\xd\xd\xd\xd\xd\xd\xd\xd\xd\xd\xd\xd\xd",
	"\xe\xe\xe\xe\xe\xe\xe\xe\xe\xe\xe\xe\xe\xe",
	"\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf\xf",
	"\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10\x10"
};

static void md2_do_chunk(struct md2_ctx *ctx, uint8_t *buf)
{
	uint8_t i, j, t;
	uint8_t x[48];

	memcpy(x, ctx->h, 16);
	memcpy(x+16, buf, 16);

	for (i = 0; i < 16; i++)
		x[i+32] = ctx->h[i] ^ buf[i];

	for (t = i = 0; i < 18; i++) {
		for (j = 0; j < 48; j++)
			t = x[j] ^= S_table[t];
		t = (t + i) & 0xff;
	}

	memcpy(ctx->h, x, 16);

	t = ctx->cksum[15];
	for (i = 0; i < 16; i++)
		t = ctx->cksum[i] ^= S_table[buf[i] ^ t];
}

void md2_update(struct md2_ctx *ctx, uint8_t *data, uint32_t len)
{
	uint32_t index, to_fill;

	index = (uint32_t) (ctx->sz & 0xf);
	to_fill = 16 - index;

	ctx->sz += len;

	if (index && len >= to_fill) {
		memcpy(ctx->buf + index, data, to_fill);
		md2_do_chunk(ctx, ctx->buf);
		len -= to_fill;
		data += to_fill;
		index = 0;
	}

	/* process as much 16-block as possible */
	for (; len >= 16; len -= 16, data += 16)
		md2_do_chunk(ctx, data);

	/* append data into buf */
	if (len)
		memcpy(ctx->buf + index, data, len);
}

void md2_finalize(struct md2_ctx *ctx, uint8_t *out)
{
	uint32_t index, padlen;

	index = ctx->sz & 0xf;
	padlen = 16 - index;

	md2_update(ctx, padding_table[padlen], padlen);
	md2_update(ctx, ctx->cksum, 16);
	memcpy(out, ctx->h, 16);
}