I am trying to understand Secure Boot and what it is doing on my system. I am using systemd-boot as my bootloader, not shim or GRUB, and Secure Boot is reported as enabled: running mokutil --sb-state outputs SecureBoot enabled. However, as far as I can tell, the EFI binary that's being used to boot my system is not signed at all. So why is Secure Boot allowing it to execute?
I am running Proxmox with two mirrored SSDs using ZFS RAID-1. Each SSD has its own EFI System Partition. Here is an excerpt from lsblk -f -o +PARTUUID:
NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINTS PARTUUID nvme1n1 ├─nvme1n1p1 4588a2cf-ad9e-4f34-a7aa-f14e4af37bb9 ├─nvme1n1p2 vfat FAT32 63B6-C9B7 865.8M 15% /mnt/nvme1n1p2 a208fcf8-78d8-4439-add8-30fb25e23af0 └─nvme1n1p3 zfs_member 5000 rpool 12777350608230387080 d5aeebcb-401d-4440-8e78-39668cbc5559 nvme2n1 ├─nvme2n1p1 bdc25142-22c5-4661-8fdb-e23c516293af ├─nvme2n1p2 vfat FAT32 63B7-1142 865.8M 15% /mnt/nvme2n1p2 dec9db8c-35f0-4e30-81ba-b25e763e125d └─nvme2n1p3 zfs_member 5000 rpool 12777350608230387080 d6c55518-f2a3-4793-bc4a-27ad2bd87058 Note that I manually mounted the ESPs to /mnt/nvme1n1p2 and /mnt/nvme2n1p2 respectively.
Here is the output of bootctl --esp-path /mnt/nvme2n1p2 status:
System: Firmware: UEFI 2.90 (American Megatrends 5.35) Firmware Arch: x64 Secure Boot: enabled (user) TPM2 Support: yes Measured UKI: no Boot into FW: supported Current Boot Loader: Product: systemd-boot 257.7-1 Features: ✓ Boot counting ✓ Menu timeout control ✓ One-shot menu timeout control ✓ Default entry control ✓ One-shot entry control ✓ Support for XBOOTLDR partition ✓ Support for passing random seed to OS ✓ Load drop-in drivers ✓ Support Type #1 sort-key field ✓ Support @saved pseudo-entry ✓ Support Type #1 devicetree field ✓ Enroll SecureBoot keys ✓ Retain SHIM protocols ✓ Menu can be disabled ✓ Multi-Profile UKIs are supported ✓ Boot loader set partition information Partition: /dev/disk/by-partuuid/dec9db8c-35f0-4e30-81ba-b25e763e125d Loader: └─/EFI/BOOT/BOOTX64.EFI Current Entry: proxmox-6.14.11-4-pve.conf Random Seed: System Token: not set Exists: yes Available Boot Loaders on ESP: ESP: /mnt/nvme2n1p2 (/dev/disk/by-partuuid/dec9db8c-35f0-4e30-81ba-b25e763e125d) File: ├─/EFI/systemd/systemd-bootx64.efi (systemd-boot 257.7-1) └─/EFI/BOOT/BOOTX64.EFI (systemd-boot 257.7-1) Boot Loaders Listed in EFI Variables: Title: UEFI OS ID: 0x0006 Status: active, boot-order Partition: /dev/disk/by-partuuid/dec9db8c-35f0-4e30-81ba-b25e763e125d File: └─/EFI/BOOT/BOOTX64.EFI Title: UEFI OS ID: 0x0005 Status: active, boot-order Partition: /dev/disk/by-partuuid/a208fcf8-78d8-4439-add8-30fb25e23af0 File: └─/EFI/BOOT/BOOTX64.EFI Title: Linux Boot Manager ID: 0x0001 Status: active, boot-order Partition: /dev/disk/by-partuuid/a208fcf8-78d8-4439-add8-30fb25e23af0 File: └─/EFI/systemd/systemd-bootx64.efi Title: Linux Boot Manager ID: 0x0002 Status: active, boot-order Partition: /dev/disk/by-partuuid/dec9db8c-35f0-4e30-81ba-b25e763e125d File: └─/EFI/systemd/systemd-bootx64.efi Boot Loader Entries: $BOOT: /mnt/nvme2n1p2 (/dev/disk/by-partuuid/dec9db8c-35f0-4e30-81ba-b25e763e125d) token: debian Default Boot Loader Entry: type: Boot Loader Specification Type #1 (.conf) title: Proxmox Virtual Environment (6.14.11-4-pve) id: proxmox-6.14.11-4-pve.conf source: /mnt/nvme2n1p2//loader/entries/proxmox-6.14.11-4-pve.conf (on the EFI System Partition) version: 6.14.11-4-pve linux: /mnt/nvme2n1p2//EFI/proxmox/6.14.11-4-pve/vmlinuz-6.14.11-4-pve initrd: /mnt/nvme2n1p2//EFI/proxmox/6.14.11-4-pve/initrd.img-6.14.11-4-pve options: root=ZFS=rpool/ROOT/pve-1 boot=zfs iommu=pt As far as I can tell, my system is booting from /EFI/BOOT/BOOTX64.EFI from the ESP on /dev/nvme2n1p2. However, this binary seems to not be signed at all. Here are some commands I tried to run and their outputs that led me to this conclusion:
sbverify --list /mnt/nvme2n1p2/EFI/BOOT/BOOTX64.EFI
No signature table present pesign --show-signature --in /mnt/nvme2n1p2/EFI/BOOT/BOOTX64.EFI
No signatures found. pesigcheck --in /mnt/nvme2n1p2/EFI/BOOT/BOOTX64.EFI
Searching dbx dbx-d719b2cb-3d3a-4596-a3bc-dad00e67656f Searching db db-d719b2cb-3d3a-4596-a3bc-dad00e67656f pesigcheck: "/mnt/nvme2n1p2/EFI/BOOT/BOOTX64.EFI" is invalid. As a sanity check, I followed some of the same steps taken here to verify the signature of shimx64.efi in a different system running Fedora:
sudo mokutil --export --db openssl x509 -inform der -outform pem -in DB-0001.der -out DB-0001.der.pem sudo sbverify --cert DB-0001.der.pem /boot/efi/EFI/fedora/shimx64.efi which output Signature verification OK as expected.
Am I missing something obvious here? It seems like Secure Boot is not doing its job if my EFI binary really is not signed at all.
