Look ma, no secrets! - bootstrapping cryptographic trust in my homelab using Nix, UKIs, TPMs and SPIFFE (asg2025)

Chaos Computer Club - recent audio-only feed

All the big cloud providers provide your machines with a unique cryptographic identity that can be used to talk to their cloud services securely without having to manage or rotate any cryptographic secrets yourself. For example GCP has Service accounts and AWS has IAM roles. This ubiquity of cloud identity and the seamless integration with all the the services of these cloud providers is one of the reasons why they are so successful. SPIFFE (Secure Production Identity Framework For Everyone) tries to unify these concepts of workload identity in a vendor neutral framework. But how do we bootstrap our cryptographic identity securely when we are running things on our own hardware as opposed to on cloud? What is our bottom turtle? In this talk, I will show how I use Nix in combination with the swiss-army knife of tools provided by systemd (ukify, systemd-measure, systemd-repart, systemd-veritysetup-generator) to create reproducible images for which we can predict TPM measurements. Paired with a custom attestation plugin for SPIRE (the reference CA server for SPIFFE) that uses TPM remote attestation I can give each of my servers a unique identity encoded in a TLS certificate if and only if they were booted up with the software that I intended them to boot up with. This then allows me to have workloads talk to each other with mutual TLS without having to manage any keys or certificates myself. Licensed to the public under https://creativecommons.org/licenses/by/4.0/de/ about this event: https://cfp.all-systems-go.io/all-systems-go-2025/talk/X3ZSXV/