Frequently Asked Questions about LinuxBoot

Why replace UEFI with LinuxBoot?

While Intel's edk2 tree that is the base of UEFI firmware is open source, the firmware that vendors install on their machines is proprietary and closed source. Updates for bugs fixes or security vulnerabilities are at the vendor's convienence; user specific enhancements are likely not possible; and the code is not auditable.

UEFI is much more complex than the BIOS that it replaced. It consists of millions of lines of code and is an entire operating system, with network device drivers, graphics, USB, TCP, https, etc, etc, etc. All of these features represents increased "surface area" for attacks, as well as unnecessary complexity in the boot process.

LinuxBoot replaces both UEFI as well as grub, which is has its own OS worth of drivers, with the fairly well tested and trusted Linux kernel. Self-help is possible if custom features are required or if security vulnerabilities need to be patched, and the flexibility of the initrd runtime allows users to tailor their "firmware" to their needs.

Why keep the vendor blobs?

LinuxBoot retains the vendor's PEI section of their UEFI firmware, which is necessary for doing things like chipset initialization, memory controller setup, CPU interconect. These functions are not documented by the CPU vendors, so it is necessary to reuse the proprietary pieces -- even coreboot uses the Intel provided FSP for these functions on modern laptops.

Additionally the Bootguard ACM, on systems that support it, must be signed by Intel and as a result we are not able to replace that part of the early startup code.

Where can I learn more about LinuxBoot?

What's wrong with UEFI Secure Boot?

Can't audit it, signing keys are controlled by vendors, doesn't handle hand off in all cases, depends on possible leaked keys.

Why use Linux instead of vboot2?

vboot2 is part of the coreboot tree and is used by Google in the Chromebook system to provide boot time security by verifying the hashes on the coreboot payload. This works well for the specialized Chrome OS on the Chromebook, but is not as flexible as a measured boot solution.

What about Trusted GRUB?

The mainline grub doesn't have support for TPM and signed kernels, but there is a Trusted grub fork that does. Due to philosophical differences the code might not be merged into the mainline. And due to problems with secure boot (which Trusted Grub builds on), many distributions have signed insecure kernels that bypass all of the protections secure boot promised.

Additionally, grub is closer to UEFI in that it must have device drivers for all the different boot devices, as well as filesystems. This duplicates the code that exists in the Linux kernel and has its own attack surface.

Using Linux as a boot loader allows us to restrict the signature validation to keys that we control. We also have one code base for the device drivers in the Linux-as-a-boot-loader as well as Linux in the operating system.

What is the concern with the Intel Management Engine?

"Rootkit in your chipset", "x86 considered harmful", etc. The ME cleaner can be used to reduce the size of the ME firmware, although we can't turn it off entirely.

How about the other embedded devices in the system?

#goodbios, funtenna, etc.

Should we be concerned about the binary blobs?

Maybe. x230 has very few (MRC) since it has native vga init.

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