On Wed, May 10, 2023 at 12:00:36PM -0400, Neal Gompa wrote: > On Wed, May 10, 2023 at 11:12 AM Simo Sorce <simo@xxxxxxxxxx> wrote: > > > > On Tue, 2023-05-09 at 12:37 -0400, Neal Gompa wrote: > > > On Tue, May 9, 2023 at 12:31 PM Lennart Poettering <mzerqung@xxxxxxxxxxx> wrote: > > > > > > > > On Di, 09.05.23 08:22, Neal Gompa (ngompa13@xxxxxxxxx) wrote: > > > > > > > > > I've been asked to consider converting /boot to a Btrfs subvolume so > > > > > that it no longer has a fixed space allocation to deal with the ever > > > > > increasing amount of firmware required for NVIDIA GPUs[1]. This is > > > > > currently incompatible with how systemd views the world, because the > > > > > "discoverable partition spec" is wired to partitions, and there is no > > > > > equivalent spec for subvolumes of a volume. And I imagine that > > > > > XBOOTLDR (whatever that is) also would have a problem with this. > > > > > > > > This makese no sense. If you want /boot to just be a subvolume of the > > > > rootfs btrfs, then this would imply it's also covered by the same > > > > security choices, i.e. encryption. We want to bind that sooner or > > > > later to things like TPM2, FIDO2, PKCS11. And that's simply not > > > > feasible from a boot loader environment. > > > > > > > > Hence, the place the kernel is loaded from (regardless if you call it > > > > /efi or /boot or /boot/efi, and regardless what fs it is) must be > > > > accessible from the boot loader easily, without requiring > > > > implementation of TPM2/FIDO2/PKCS11 hookup in the boot loader. > > > > > > > > Hence: btrfs subvols won't work for this > > > > > > If we're not using LUKS for encryption, then this is not a problem. > > > We're generally looking toward encrypting subvolumes individually > > > using the upcoming Btrfs native encryption capability rather than > > > using LUKS. That allows us to > > > > > > 1. Pick which subvolumes are encrypted > > > 2. Pick the security binding method per subvolume > > > > > > For example, the root and home subvolumes would use TPM or some other > > > non-interactive binding. The user subvolume in home would decrypt with > > > user login. > > > > Neal, > > I think you are barking up the wrong tree here. > > > > The design of the boot loader *nedds* to be simple. > > > > Simple means, VFAT and *no trust* in the filesystem, individual files > > are signed and verified. > > Only the bare minimum *necessary* is in the boot partition, which means > > kernel images and the bare minimum init image needed to unlock and > > mount the root partition. > > > > There is no point in building a more complex system than that and load > > tons of garbage drivers in the EFI. > > > > Booting is a staged system, and should be kept as simple as possible to > > avoid duplication (which means subtle bugs and a ton of maintenance > > overhead). > > > > This proposal isn't better. Neither Windows nor macOS put critical > operating system code in the ESP, and we shouldn't either. But you > want to put kernels in the ESP? That's the wrong approach too. > > As soon as you throw UKIs in the mix, you've completely broken that > because now the absolutely most valuable code for your system is in a > "hostile" environment. At least we can make /boot authenticated and > tamper resistant as a Btrfs subvolume. The firmware will start by booting a binary found in the ESP, and thus given the ESP is untrusted (hostile) we need a means to validate that binary's integrity no matter what, most likely using SecureBoot & TPM PCR measurements. Using this mechanism for validating the UKI makes sense since it has to exist no matter what. There's no need for the filesystem to be authenticated / tamper resistant if the binaries themselves are authenticated and tamper resistant. > I would rather have a multi-stage boot process, where the first stage > does just enough to unlock and load the OS volume to load the real > boot environment. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
