Secure Boot-neutering PKfail debacle is more prevalent than anyone knew

A supply chain failure that compromises Secure Boot protections on computing devices from across the device-making industry extends to a much larger number of models than previously known, including those used in ATMs, point-of-sale terminals, and voting machines.

The debacle was the result of non-production test platform keys used in hundreds of device models for more than a decade. These cryptographic keys form the root-of-trust anchor between the hardware device and the firmware that runs on it. The test production keys—stamped with phrases such as “DO NOT TRUST” in the certificates—were never intended to be used in production systems. A who’s-who list of device makers—including Acer, Dell, Gigabyte, Intel, Supermicro, Aopen, Foremelife, Fujitsu, HP, and Lenovo—used them anyway.

Medical devices, gaming consoles, ATMs, POS terminals

Platform keys provide the root-of-trust anchor in the form of a cryptographic key embedded into the system firmware. They establish the trust between the platform hardware and the firmware that runs on it. This, in turn, provides the foundation for Secure Boot, an industry standard for cryptographically enforcing security in the pre-boot environment of a device. Built into the UEFI (Unified Extensible Firmware Interface), Secure Boot uses public-key cryptography to block the loading of any code that isn’t signed with a pre-approved digital signature.

Use of the test platform keys compromises the entire security chain established by Secure Boot because the private portion underpinning their security is an open secret that’s known to hundreds or possibly thousands of different people. Making matters worse, the private portion of one of the test keys was published in a 2022 post on GitHub. This secret information is a necessary element in a highly sophisticated class of attacks that plant so-called rootkits that infect the UEFI of devices protected by Secure Boot.

Since disclosing the findings in July, researchers at security firm Binarly have learned that the number of device models using the test keys is much larger than previously known. Whereas previously they knew of roughly 513 models using a test key, they are now aware of 972. Additionally, they previously knew that roughly 215 of the affected models used the key compromised on GitHub; they now know of about 490. Finally, they discovered four new test keys they hadn’t identified before, bringing the total number to about 20. The researchers have dubbed the industry-wide failure PKfail, because it involves PKs (platform keys).