/*
 * msnp11.c
 *
 * New-style challenge
 *
 * (c) 2002-2005 Thomas White <taw27@srcf.ucam.org>
 *  Part of TuxMessenger - GTK+-based MSN Messenger client
 *
 * This package is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 dated June, 1991. 
 *
 * This package is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details. 
 *
 * You should have received a copy of the GNU General Public License
 * along with this package; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA. 
 *
 *
 *		Special Notice for the MSNP11 Challenge Module
 *		----------------------------------------------
 *		The author(s) of this software performed no
 *		reverse-engineering of any Microsoft software
 *		in order to create this module.  Information
 *		on the MSNP11-style challenge can be freely
 *		found on the Web.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>
#include <stdint.h>
#include <openssl/md5.h>
#include <stdlib.h>
#include <stdio.h>
#include <glib.h>

#include "msnp11chl.h"

#undef MSNP11CHL_DEBUG

uint32_t msnp11chl_tolittle(uint32_t val) {
	return GINT32_TO_LE(val);
}

char *msnp11chl_response(const char *challenge) {

	char *flobbadob;
	unsigned char *md5;
	uint64_t words_1[4];
	uint64_t words_1_orig[4];
	uint32_t *words_2;
	int nw2;
	int i;
	uint64_t low = 0;
	uint64_t high = 0;
	uint64_t key;
	uint64_t hash1;
	uint64_t hash2;
	char *response;
	
	md5 = malloc(MD5_DIGEST_LENGTH);	/* =16 */
	flobbadob = malloc(strlen(challenge)+strlen(CLIENT_CODE)+1);
	strcpy(flobbadob, challenge);
	strcat(flobbadob, CLIENT_CODE);
	MD5(flobbadob, strlen(flobbadob), md5);
	free(flobbadob);
	
	/* Split into four-byte words. */
	words_1_orig[0] = msnp11chl_tolittle((uint32_t)*(uint32_t *)(md5));
	words_1_orig[1] = msnp11chl_tolittle((uint32_t)*(uint32_t *)(md5+4));
	words_1_orig[2] = msnp11chl_tolittle((uint32_t)*(uint32_t *)(md5+8));
	words_1_orig[3] = msnp11chl_tolittle((uint32_t)*(uint32_t *)(md5+12));
	free(md5);

	for (i=0; i<4; i++) {
		words_1[i] = words_1_orig[i] & 0x7FFFFFFF;
	}

#ifdef MSNP11CHL_DEBUG
	printf("words_1[0] = 0x%08lx\n", words_1[0]);
	printf("words_1[1] = 0x%08lx\n", words_1[1]);
	printf("words_1[2] = 0x%08lx\n", words_1[2]);
	printf("words_1[3] = 0x%08lx\n", words_1[3]);
#endif /* MSNP11CHL_DEBUG */
	
	flobbadob = malloc(strlen(challenge)+strlen(CLIENT_ID)+9);
	strcpy(flobbadob, challenge);
	strcat(flobbadob, CLIENT_ID);
	while ( strlen(flobbadob) % 8 != 0 ) {
		strcat(flobbadob, "0");
	}
	
	/* Split into four-byte words. */
	words_2 = malloc(strlen(flobbadob));
	memcpy(words_2, flobbadob, strlen(flobbadob));	/* Not including terminator. */
	nw2 = strlen(flobbadob)/4;	/* = number of members in words_2[] */
	free(flobbadob);
	for (i=0; i<nw2; i++) {
		words_2[i] = GINT32_TO_LE(words_2[i]);
#ifdef MSNP11CHL_DEBUG
		printf("words_2[%i] = 0x%08lx\n", i, words_2[i]);
#endif /* MSNP11CHL_DEBUG */
	}
	
	for (i = 0; i<nw2; i+=2) {

		uint64_t temp = words_2[i];
		temp = (0x0E79A9C1 * temp);
		temp = temp % 0x7FFFFFFF;
		temp += high;
		temp = words_1[0] * temp + words_1[1];
		temp = temp % 0x7FFFFFFF;

#ifdef MSNP11CHL_DEBUG
		printf("1: temp = 0x%08lx", temp);
		printf(" high = 0x%08lx", high);
		printf(" low = 0x%08lx\n", low);
#endif /* MSNP11CHL_DEBUG */

		high = words_2[i+1];
		high = (high + temp) % 0x7FFFFFFF;
		high = words_1[2] * high + words_1[3];
		high = high % 0x7FFFFFFF;

		low = low + high + temp;
		
#ifdef MSNP11CHL_DEBUG
		printf("2: temp = 0x%08lx", temp);
		printf(" high = 0x%08lx", high);
		printf(" low = 0x%08lx\n", low);
#endif /* MSNP11CHL_DEBUG */

	}

	free(words_2);

	high = (high + words_1[1]) % 0x7FFFFFFF;
	low = (low + words_1[3]) % 0x7FFFFFFF;
#ifdef MSNP11CHL_DEBUG
	printf("high = 0x%08lx", high);
	printf(" low = 0x%08lx\n", low);
#endif /* MSNP11CHL_DEBUG */
	
	/* "high" is a 32-bit integer in a 64-bit type, so swapping it automatically shifts it by 32 bits */
	key = (low<<32) + high;
#ifdef MSNP11CHL_DEBUG
	printf("key = %llx\n", key);
#endif /* MSNP11CHL_DEBUG */

	hash1 = words_1_orig[0] + (words_1_orig[1]<<32);
	hash2 = words_1_orig[2] + (words_1_orig[3]<<32);
#ifdef MSNP11CHL_DEBUG
	printf("hash1 = 0x%016llx, hash2 = 0x%016llx\n", hash1, hash2);
#endif /* MSNP11CHL_DEBUG */

	response = malloc(33);
	sprintf(response, "%.16llx%.16llx", GUINT64_SWAP_LE_BE(key^hash1), GUINT64_SWAP_LE_BE(key^hash2));

	for ( i=0; i<strlen(response); i++ ) {
		if ( response[i]==' ' ) {
			response[i]='0';
		}
	}

	return response;

}