Lanzaboote: Secure Boot for NixOS

🚧🚧🚧 This is not ready for non-developer usage. 🚧🚧🚧

This repository contains experimental tooling for Secure Boot on NixOS.

🪛 To Do 🪛

There is a bunch of work to do. Please coordinate in the Matrix room, if you want to take something up:

• Overview documentation about the approach
• Document a experimental setup for developers on how to use this repository
• Coordinate with bootspec RFC stakeholders to communicate a experience report on the bootspec usage
• Cleaning up flakes.nix for AArch64
• Upstream nixpkgs work
  • Lanzatool
  • Lanzaboote (needs unstable Rust!)
  • NixOS boot loader installation etc.
• Unit testing for Lanzatool
• Investigating how this can fit into systemd-boot theory about sysexts for initrds while keeping NixOS semantics
• Threat modelling explanations: "bring your own PKI", "share your PKI with MSFT CA", "bring rhboot shim with MOK", etc.
• Ensuring 99 % of the paths are "happy paths" : protecting user against bricking their machines, identifying sources of risk, communicating intent and detecting risks
• Experimenting with fwupd / Green Checkmark in GNOME Device Security
  • https://github.com/fwupd/fwupd/issues/5284
• Experimenting with TPM2 measurements
• Studying the initrd secrets feature in NixOS wrt SecureBoot & TPM2
• ...

High-Level Boot Flow

flowchart LR
	systemd[systemd-boot]
	lanzaboote[lanzaboote]
	kernel[Linux Kernel]

	systemd --> lanzaboote
	lanzaboote --> kernel

lanzatool

lanzatool is a Linux command line application that takes a bootspec document and installs the boot files into the UEFI ESP.

To make systemd-boot recognize a new boot target, lanzatool builds a UKI image. To avoid having to embed kernel and initrd, we use a custom stub lanzaboote (see below) that loads kernel and initrd from the ESP.

Remaining items to implement are:

• Migrations from non-SecureBoot machine (old generation files) ;
• Alternative Nix stores paths ;
• Key rotation support ;
• Bootspec (abuse) cleanups ;
• Automatic synchronization policies for changing PKI (rotating keys, re-enrolling them, etc.) ;
• NixOS specialisations support ;
• Automatic removal of unused files relative to the configurationLimit option ;
• os-release patch so systemd-boot shows pretty names with generation number

lanzaboote

lanzaboote is the stub that lanzatool uses to form an UKI. It loads a Linux kernel and initrd without breaking the Secure Boot chain of trust. Instead of rolling our own crypto, lanzaboote re-uses the signature verification that is built-in to UEFI.

Remaining items to implement are:

• TPM measurements like systemd-stub does
• Better error management

Relevant Nixpkgs Work

This project depends on upstream nixpkgs work:

• https://github.com/NixOS/nixpkgs/pull/191665
• https://github.com/DeterminateSystems/bootspec-secureboot/
• https://github.com/DeterminateSystems/bootspec

You can find everything integrated as PoC here.