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Luigi Auriemma

Application: Netrek
http://www.netrek.org
Versions: <= 2.12.0 (Vanilla server)
Platforms: *nix and Windows
Bug: format string
Exploitation: remote (in-game)
Date: 02 Mar 2007
Author: Luigi Auriemma
e-mail: aluigi (at) autistici (dot) org [email concealed]
web: aluigi.org

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

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

Netrek is a well known real-time strategy game inspired to Star Trek.

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2) Bug
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The Vanilla server is affected by a format string vulnerability caused
by the calling of the pmessage2() function without the needed format
argument.

The bug is located in new_warning() and can be exploitated through the
locking of a player (the same attacker too) who is using a malformed
nickname.

Note that the EVENTLOG switch must be enabled for exploiting this
vulnerability (default is disabled).

from ntserv/warning.c:

void new_warning(int index, const char *fmt, ...) {

char temp[150];

va_list args;
va_start(args, fmt);

vsprintf(temp, fmt, args);

...

if (eventlog) {

char from_str[9]="WRN->\0\0\0";

strcat(from_str, me->p_mapchars);
pmessage2(0, 0, from_str, me->p_no, temp);
}

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

http://aluigi.org/poc/netrekfs.zip

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4) Fix
======

Version 2.12.1

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

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