-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Advisory ID: SYSS-2019-034 Product: Surface Keyboard Manufacturer: Microsoft Affected Version(s): WS2-00005 Tested Version(s): WS2-00005 Vulnerability Type: Insufficient Protection of Code (Firmware) and Data (Cryptographic Key) Risk Level: Medium Solution Status: Open Manufacturer Notification: 2019-07-31 Solution Date: - Public Disclosure: 2019-10-10 CVE Reference: Not assigned yet Author of Advisory: Matthias Deeg (SySS GmbH) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: Microsoft Surface Keyboard is a Bluetooth Low Energy (LE) keyboard. The manufacturer describes the product as follows (see [1]): "Meticulously crafted, just like your Surface Enjoy the solid feel of the keyboard under your fingers as you work. And it pairs seamlessly with your Surface with Wireless Bluetooth - at a range of up to 50 feet - and battery power to last a full year." Due to the insufficient protection of the flash memory of the keyboard, an attacker with physical access has read and write access to the firmware and the used cryptographic key. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: SySS GmbH found out that the embedded flash memory of the Bluetooth LE Microsoft Surface Keyboard can be read and written via the SWD (Serial Wire Debug) interface of the used nRF51822 Bluetooth SoC [2] as the flash memory is not protected by the offered readback protection feature. Thus, an attacker with physical access to the keyboard can simply read and write the nRF51822 flash memory contents and either extract the cryptographic key (Bluetooth LE Long Term Key), for instance, to perform further attacks against the wireless communication, or modify the firmware. However, even if the readback protection of the nRF51822 was enabled, an attacker would be able to read and write the flash memory contents by bypassing the security feature as described in [3] and [4] with slightly more effort. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Proof of Concept (PoC): SySS GmbH could successfully read the nRF51822 flash memory contents of the Microsoft Surface Keyboard via the SWD interface using a SEGGER J-Link PRO [5] debug probe in combination with SEGGER J-Link Commander and extract the currently used cryptographic key (Long Term Key). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: According to Microsoft, the reported security issue does not meet the bar for servicing via a security update [6]. The described security issue may be fixed in future versions of the product. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2019-07-31: Vulnerability reported to manufacturer 2019-08-01: Microsoft confirms receipt of security advisory 2019-08-06: Microsoft responds that the reported issue does not meet the bar for servicing via a security update 2019-10-10: Public release of SySS security advisory ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product website for Microsoft Surface Keyboard https://www.microsoft.com/en-us/p/surface-keyboard/8r3rqvvflp4k [2] nRF51822 Product Specification v3.1 https://infocenter.nordicsemi.com/pdf/nRF51822_PS_v3.1.pdf [3] Kris Brosch, Include Security, Firmware dumping technique for an ARM Cortex-M0 SoC, 2015 https://blog.includesecurity.com/2015/11/NordicSemi-ARM-SoC-Firmware-dumping-technique.html [4] Andrew Tierney, Pen Test Partners, NRF51822 code readout protection bypass - a how-to, 2018 https://www.pentestpartners.com/security-blog/nrf51822-code-readout-protection-bypass-a-how-to/ [5] Product website for Segger J-Link PRO https://www.segger.com/products/debug-probes/j-link/models/j-link-pro/ [6] Microsoft Vulnerability Severity Classification for Windows https://aka.ms/windowsbugbar [7] SySS Security Advisory SYSS-2019-034 https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2019-034.txt [8] SySS GmbH, SySS Responsible Disclosure Policy https://www.syss.de/en/news/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/Materialien/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: http://creativecommons.org/licenses/by/3.0/deed.en -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE0fCgNfBs5nXNuQUU2aS/ajStTasFAl2dwHkACgkQ2aS/ajSt TauyRQ/8D9w9CfoM/yhoMzUqn//Rnbh5MfiTyUuZnl/UmBcAMz3sATOqFuB7/ZOb CVr7JoWS8QoZ2LxsdTt8jSIfg9uBtrSLCUu4x8oHyvs7vysTULB3ITXxVMBAKh2z 1cntRe0RzS1Fbx6SNyFNwY5Jwma50v2Mpc/V+B8L8kjmB9Ijc5ztV/bMhrA/WCWO hf8Rn0guhLoNMbIjMSPnVuwGrh7NxvDOlEfpAlpn4NsO/RWAIGcjzy0f0T1SztjP KIFEQThrmCLS3SeRbVg3u1JcTWGiimL9JNRaiCOfcnf3TSsegjWLxoc4lNgrwMC6 dKZNYBEREycvYpGZiDXANFHhPimIkZcYLSQ14QqMpkCeRIUH7c2nrjDVHi141eOk EO//qOn5WL0jahP7g3DY7rB4OkGWP2+4hJo056XXGYqgqqYzWrA4gMsVupTrvVz8 lR4T4AUSg6WKb0NoK8d2p/aBZF62XSXic9OCfYHnjI6xDCjL97r2kUrBHp4HNXIQ tvHTAodGo/Tggk6req4W7+ABEKaG7xS4RV5OxQV+vk3QVW/DSCHgZK174cfXJFRT jGP6rroeIv7Va6HZpJHTyiemGDw9qvskSPgqQ+17QYXLiGG3xynUuysaXpzXzHNU vwuwM8QR7szT9f+YvG03NssFKOUA1NfOTSyrKoUL9QyYpMdNSUo= =w7Vq -----END PGP SIGNATURE-----