Limited format string in Netrek 2.12.0

[Luigi Auriemma <aluigi () autistici org>]

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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 () autistici org
              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
======


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