Advisory ID: SYSS-2017-026 Product: Microsoft Surface Hub Keyboard Manufacturer: Microsoft Affected Version(s): n/a Tested Version(s): n/a Vulnerability Type: Cryptographic Issues (CWE-310) Insufficient Protection against Replay Attacks Risk Level: Medium Solution Status: Open Manufacturer Notification: 2017-10-20 Solution Date: - Public Disclosure: 2018-01-29 CVE Reference: Not yet assigned Authors of Advisory: Matthias Deeg (SySS GmbH) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: The Microsoft Surface Hub Keyboard is a wireless keyboard that can be used in combination with the digital whiteboard/collaboration system Microsoft Surface Hub (see [1]). Due to an insecure implementation of the encrypted data communication, the Microsoft Surface Hub Keyboard is vulnerable to replay attacks with certain restrictions. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: The SySS GmbH found out that the Microsoft Surface Hub Keyboard Keyboard is prone to replay attacks with some limitations. An attacker can sniff the AES-encrypted data packets of the 2.4 GHz radio communication sent by the keyboard to the receiver (USB dongle) and replay the recorded communication data causing the same effect as the original data communication. According to test results of the SySS GmbH, the Microsoft Surface Hub Keyboard and its USB dongle have implemented a replay protection based on an incrementing packet counter. But the used window for valid packet counter values is large enough to perform a replay attack if there were not too many data packets caused by further keystrokes between the attacker's recording and the playback. The same behavior was found in the previously tested wireless keyboard Microsoft Wireless Desktop 2000 (see [2]). A replay attack against the keyboard can, for example, be used to gain unauthorized access to a computer system that is operated with a vulnerable keyboard. In this attack scenario, an attacker records the radio communication during a password-based user authentication of his or her victim, for instance during a login to the operating system or during unlocking a screen lock. At an opportune moment when the victim's computer system is unattended, the attacker approaches the victim's computer and replays the previously recorded AES-encrypted data communication for the password-based user authentication and by this gets unauthorized access to the victim's system. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Proof of Concept (PoC): SySS GmbH could successfully perform a replay attack as described in the previous section using the USB radio dongle Crazyradio PA (see [3]) and the proof-of-concept software tool simple_replay.py that is part of the SySS nRF24 Playset (see [4]). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: According to information from the manufacturer, the reported security issue does not meet the requirements for a security patch. For further information, please contact the manufacturer. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2017-10-20: Vulnerability reported to manufacturer 2017-10-20: Manufacturer acknowledges e-mail with SySS security advisory 2017-11-30: E-mail from manufacturer with open questions 2017-12-01: E-mail to manufacturer concerning open questions 2017-12-08: E-mail from manufacturer with open questions regarding attack scenarios and preconditions 2017-12-11: E-mail to manufacturer concerning open questions, attack scenarios, and preconditions 2017-12-11: E-mail from manufacturer that the reported security issue and its exploitability does not meet the bar for a security patch 2017-12-13: E-mail to manufacturer explaining - from a SySS point of view - the feasibility of actual replay attacks that exploit the reported security vulnerability 2018-01-29: Public release of security advisory ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product website for Microsoft Surface Hub https://www.microsoft.com/en-us/surface/devices/surface-hub/overview [2] SySS Security Advisory SYSS-2016-043 https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2016-043.txt [3] Product website for Crazyradio PA https://www.bitcraze.io/crazyradio-pa/ [4] SySS nRF24 Playset https://github.com/SySS-Research/nrf24-playset [5] SySS Security Advisory SYSS-2017-026 https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2017-026.txt [6] SySS Responsible Disclosure Policy https://www.syss.de/en/responsible-disclosure-policy/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Credits: This security vulnerability was found by Matthias Deeg of SySS GmbH. E-Mail: matthias.deeg (at) syss.de Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Matthias_Deeg.asc Key fingerprint = D1F0 A035 F06C E675 CDB9 0514 D9A4 BF6A 34AD 4DAB ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclaimer: The information provided in this security advisory is provided "as is" and without warranty of any kind. Details of this security advisory may be updated in order to provide as accurate information as possible. The latest version of this security advisory is available on the SySS Web site. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Copyright: Creative Commons - Attribution (by) - Version 3.0 URL: https://creativecommons.org/licenses/by/3.0/deed.en