secuvera-SA-2018-03: Command Injection, Broken Access Control and Evil-Twin-Attack in Microsoft Wireless Display Adapter V2 - CVE-2018-8306

[Tobias Glemser <tglemser () secuvera de>]

secuvera-SA-2018-03: Command Injection, Broken Access Control and Evil-Twin-Attack in Microsoft Wireless Display 
Adapter V2 - CVE-2018-8306

Affected Products:
Microsoft Wireless Display Adapter V2:
        - Microsoft Wireless Display Adapter V2 Softwareversion 2.0.8350 to 2.0.8372 have been tested and are affected 
by the Command Injection Vulnerability
        - Microsoft Wireless Display Adapter V2 Softwareversion 2.0.8350 has been tested and is affected by the Broken 
Access Control Vulnerability
        - Microsoft Wireless Display Adapter V2 Softwareversion 2.0.8350 has been tested and is affected by the 
Evil-Twin-Attack Vulnerability
        Other releases have not been tested. 

        References
        - https://www.secuvera.de/advisories/secuvera-SA-2018-03.txt
        - https://portal.msrc.microsoft.com/en-us/security-guidance/advisory/CVE-2018-8306 (Command Injection)
        - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-8306 (Command Injection)
        
Summary:
        Microsoft Wireless Display Adapter (MsWDA ) is a hardware device to
        "Share what’s on your tablet, laptop, or smartphone. All 
        Miracast® enabled Windows 10 phones, tablets and laptops, 
        including the Surface line up. Stream movies, view personal 
        photos, or display a presentation on a big screen – all 
        wirelessly." [1]
        
        During our research we found a command-injection, broken 
        access control and an "evil-twin" attack.
        
Background:
        MsWDA uses Wifi-Direct for the Connection and Miracast for 
        transmitting Video- and Audiodata. The Wifi-Connection 
        between MsWDA and the Client is alwasy WPA2 encrypted. To 
        setup the connection, MsWDA provides a well-known mechanism: 
        Wi-Fi Protected Setup (WPS). MsWDA implements both push 
        button configuration (PBC) and PIN configuration. Despite the
        original design and name, MsWDA offers PBC with the button 
        virtually "pressed". A user simply connects. Regardless the 
        authentication method used (PBC or PIN), a client is assigned
        to a so called "persistent group". A client in a persistent 
        group does not have to re-authenticate on a new connection. 
        
        Effect:
        Command injection:
        The attacker has to be connected to the MsWDA.Using the 
        Webservice the Name of the MsWDA could be set in the 
        parameter "NewDeviceName". Appending characters 
        to escape command line scripts, the device gets into a 
        boot loop. Therefore the conclusion is legit, there is 
        a command injection. After several bricked MsWDAs we gave
        up. 
        
        Broken Access Control:
        a) PBC is implemented against Wifi Alliance Best Practices [2]
        No Button has to be pressed, therefore the attacker has 
        just to be in network range to authenticate. Physical access
        to the device is not required.
        
        b) If an attacker has formed a persistent group with Push 
        Button Configuration, he can authenticate with the persistent 
        group, even if the configuration method is changed to PIN 
        Configuration.
        
        c) A persistent group does not expire, so the access right 
        longs forever. The WPA2 key of the connection does not change 
        for a persistent group.
        
        Evil-Twin-Attack:
        To perform an Evil-Twin Attack, the Attacker has to be connected
        to the MsWDA attacked. He then offers an own Display Adapter Service
        with the same name like the MsWDA attacked. The user will only find 
        the attackers name in the available connections and connect to the 
        attackers Evil Twin. A replication service will stream the users data 
        from the attackers device to the MsWDA attacked. Therefore the user 
        will not be able to recognize the attack.
        Besides the ability to view streaming data, the attacker can use 
        the established connection to access other services on the victims
        device, e. g. files if shared to trusted networks by the user.

        Vulnerable Script for the command injection:
        /cgi-bin/msupload.sh, Parameter NewDeviceName
        
Example for command injection:
        http://IPaddress/cgi-bin/msupload.sh?Action=SetDeviceName&NewDeviceName=a=b
        #show a device name with leading adapter_name=
        http://IPaddress/cgi-bin/msupload.sh?Action=SetDeviceName&NewDeviceName=a%0D$(ls)%0D
        #bring Display Adapter into a bootloop
        
        Solution:
        Always use PIN method for authentication. This does not require 
        the attacker to have physical access, at least he nees the screen visible.
        According to the vendor, the command injection has been fixed in 
        the firmware update July 2018.  
        
        Disclosure Timeline:
        2018/03/21 vendor contacted
        2018/03/21 initial vendor response
        2018/04/06 vendor confirmation 
        2018/04/20 vendor informs about fixes planned
        2018/04/21 feedback to the vendor on the fixes
        2018/05/17 vendor provides timeline for the firmware fixes for July 10th
        2018/06/19 vendor provides assigend CVE number
        2018/07/10 vendor publishes Advisory and Firmware-Updates 
        2018/07/30 coordinated public disclosure
        
        
        
External References:
         [1] https://www.microsoft.com/accessories/en-us/products/adapters/wireless-display-adapter-2/p3q-00001
         [2] https://www.wi-fi.org/downloads-public/wsc_best_practices_v2_0_1.pdf/8188

           
Credits:
        Tobias Glemser
        tglemser () secuvera de
        secuvera GmbH
        https://www.secuvera.de
        
        Simon Winter
        simon.winter95 () web de
        Aalen University
        https://www.hs-aalen.de/en
        
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        to be able to attack or damage. Therefore secuvera shall
        not be liable for any direct or indirect damages that might be
        caused by using this information.