secureboot: add check to validate signature db certificates before updating

[Rolv-Apneseth]

Closes #1099

The main concern this resolves is that, with the Microsoft UEFI CA 2011 Certificate having expired, any further updates to the shim will not be dual-signed, and will only be signed by the 2023 key. This means that any system with Secure Boot enabled will be broken if bootupd updates the shim and the system does not have the certificate available in their firmware's signature database. So we should make sure bootupd is aware of this requirement so we don't break user's Secure Boot systems.

As stated in the issue, we wanted a way to incorporate some of the sbchooser logic to achieve this goal. However, I found this crate which suits our use-case perfectly. I discussed briefly with the creator and he agreed it was a good fit.

I've implemented this in such a way that any update will be blocked if Secure Boot is enabled and the 2023 cert is not in the system's signature DB. So updating is allowed as long as any one of the following is true:

1. System is not EFI-booted
2. System does not have Secure Boot enabled
3. System has the 2023 cert in the signature database

Something that might be nice but would add some complexity is only blocking updates if the shim is actually being updated, as that's the only one that matters here. Any thoughts on this? I think it's gonna be a brief enough window where this is actually helpful that keeping it as simple as possible will benefit us more in the long run. Plus Secure Boot systems with outdated certificates should indeed have their firmware updated as soon as possible. I'd be happy to try implement the module comparison logic if we think it's important to only block on shim updates though.

Also for testing, I have a positive case test, and tested the negative case manually. I can't think of a good way to test the negative case with kola. Maybe including a feature in kola to enable using the db with an older certificate (binary blob?), but I'm not sure that's worth it.

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src/cli/bootupctl.rs (1)

96-97: 🎯 Functional Correctness

No Args change is required.

For named structs, clap 4.6's #[derive(Parser)] also generates clap::Args. UpdateOpts therefore satisfies both the Update subcommand payload and the flattened field contract.

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📝 Walkthrough

Walkthrough

The update commands now validate the Microsoft UEFI CA 2023 certificate on EFI systems before bootloader updates. A gated skip option is available. The change adds EFI dependencies, Secure Boot validation, CLI wiring, and a positive kola test.

Changes

Secure Boot validation

Layer / File(s)	Summary
EFI certificate validation Cargo.toml, src/main.rs, src/secureboot.rs	EFI targets use virtfw-libefi. The new module skips non-EFI or disabled Secure Boot systems and rejects missing, unreadable, or invalid Microsoft UEFI CA 2023 certificates.
Update preparation integration src/cli/bootupctl.rs, tests/kola/test-secureboot	update and adopt-and-update accept UpdateOpts and validate Secure Boot unless the EFI-only skip flag is set. The kola test exercises the enabled positive case.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 847a9

The update commands add the intended Secure Boot certificate validation, with no substantiated merge-blocking issue remaining.

Suggested reviewers: johan-liebert1

Sequence Diagram(s)

sequenceDiagram
  participant Operator
  participant bootupctl
  participant secureboot
  participant EFI_variables
  participant bootupd
  Operator->>bootupctl: run update
  bootupctl->>secureboot: validate_secureboot_for_update()
  secureboot->>EFI_variables: read SecureBoot and db
  EFI_variables-->>secureboot: return variable data
  secureboot-->>bootupctl: return validation result
  bootupctl->>bootupd: perform update when validation succeeds

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🚥 Pre-merge checks | ✅ 6

✅ Passed checks (6 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes address issue [#1099] by checking EFI Secure Boot state and blocking updates when the Microsoft UEFI CA 2023 certificate is absent from the firmware signature database.
Out of Scope Changes check	✅ Passed	The dependency, Secure Boot validation module, CLI integration, and positive-case kola test all support the linked issue objectives. No unrelated code changes are identified.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 4 files.
Commit Message Convention	✅ Passed	The PR range contains one non-merge commit: secureboot: add check to validate signature db certificates before updating. secureboot is a component name, the description starts with lowercase imper…
Title check	✅ Passed	The title uses the required subsystem: lowercase description format, uses imperative wording, and accurately describes the Secure Boot certificate validation change.
Description check	✅ Passed	The description directly explains the Secure Boot certificate transition, update-blocking behavior, implementation approach, and test coverage.

Full details: Commit Message Convention

Explanation

The PR range contains one non-merge commit: secureboot: add check to validate signature db certificates before updating. secureboot is a component name, the description starts with lowercase imperative add, and it has no trailing period. No other non-merge commit requires review.

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Actionable comments posted: 1

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Inline comments:
In `@src/secureboot.rs`:
- Around line 20-28: Update is_secureboot_enabled to return an error when
sysfs::varstore_read cannot read SECURE_BOOT or var.data() is empty, and return
success with disabled status only when the readable first byte is zero. Update
validate_secureboot_for_update to propagate these errors while skipping the
signature database check only for a confirmed zero value, and add regression
coverage for both unknown-state failures and the readable-disabled path.

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• Cargo.toml
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[Rolv-Apneseth]

Bot suggestion to bail when unable to read Secure Boot variables was incorrect as proven by the CI failure. UEFI can be enabled while the Secure Boot variables don't even exist.

[yasminvalim]

I think the error message is good, but could be improved. Instead of focus on fwupd it could be a little more generic and give the user other options to be more clear, something like:

""Please update your system firmware using your firmware setup menu, fwupd, or similar tools."

WDYT?

[Rolv-Apneseth]

The fwupd maintainer did tell me that 99% of updates are done through some kind of UI not fwupdmgr... I was tailoring this more towards FCOS itself but maybe that's reasonable if we want bootupd to be distro-agnostic.

[yasminvalim]

Thanks for working on this, overall looks pretty good. I just made a suggestion about improving the message error, but is not a blocker. Approved. :)