So why can't Linux just do whatever the Windows update does?

So my framework 16 that has never seen Windows running FedoraKDE with FDE (but not auto-unlock, typed pass every boot) enabled is going to explode?

Half kidding, but like, should I disable secure boot or something? Run fwupd?

That's what I do. I never enabled it based on the assumption that because it's a Microsoft thing, it would eventually fuck me over in some way. That attitude has served me well for may years lol.

You can but then you don’t have secure boot.

From https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/8/html/managing_monitoring_and_updating_the_kernel/signing-a-kernel-and-modules-for-secure-boot_managing-monitoring-and-updating-the-kernel: "In addition, the signed first-stage boot loader and the signed kernel include embedded Red Hat public keys. These signed executable binaries and embedded keys enable RHEL 8 to install, boot, and run with the Microsoft UEFI Secure Boot Certification Authority keys. These keys are provided by the UEFI firmware on systems that support UEFI Secure Boot."

Basically the Microsoft keys are ones that the firmware vendor (motherboard or chip manufacturer) recognizes as secure by default (via CA validation). You can override them. It's not a Linux issue but a hardware-vendor-defaulting-to-Microsoft issue.

Microsoft has spent the time and money to get their key added to the silicone of the BIOS chips on PC hardware. Everyone else needs to get their key signed by Microsoft, including Red Hat and Canonical.

Every manufacturer includes the Microsoft secure boot key in their firmware. I'm not sure if any manufacturer includes a Linux-specific key. So Microsoft signed a bootloader with their key, enabling secure boot to work with Linux without having to load another key onto every device.

AFAIK it's not necessarily about Linux using Microsoft keys, it's more about Microsoft shoe-horning their bullshit into everything they possibly can, including at the hardware/firmware level.

Yep!

Secure boot will fail validation. You can still boot it anyway by disabling secure boot. You just lose a layer of security. You can manually sign boot files yourself and add the relevant certificate to the motherboard firmware database. Assuming it lets you.

Then it can't be booted with new media. Microsoft has been very, very slow with the automatic rollout of their own key updates, and made just about no progress over the past two years. It's been manual updates + newly produced systems only.

The trick here is that they have a key-exchange-key that can be used to update the other keys. That doesn't expire (or rather, not in a meaningful way). But, a Windows image is still only going to boot on a system that trusts the key that was used for it. If you make a Windows image on a 2011 system now, it's going to be signed with the 2011 key, and it won't boot on a system that distrusts that key. The same is true in reverse.

Their key update documentation is all available and some enterprises have been on the new key for a while, but it's a lot of manual work and a lot of problems have popped up, most documented in there. How they're going to roll this out automatically to normal users isn't obvious to me. There's technically nothing stopping a system from trusting both the 2011 and 2023 keys, and I wouldn't be entirely surprised if they end up never pushing the 2011 revocation.

The keys they use for their own OS don't truly expire until late 2026, and I expect they'll do their best to delay it until then, but the next time they have to update their boot manager is going to be painful and introduce all kinds of new problems.