chore(disk): align iso bootc switch with 00-image-info transport

[mrbobbytables]

Switch the bootc switch invocation in the ISO installer kickstart from plain --transport registry to ostree-image-signed:docker://.

This ensures cosign signature verification against Fulcio/Rekor at ISO install time, matching the repo's keyless signing and trust model.

Closes #330

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[hanthor]

Making iso.toml consistent with build/00-image-info.sh:41 is worth doing. But as it stands this changes the transport name without adding the verification the name implies, and the title ("use signed transport") will be read as a security improvement that isn't yet real.

ostree-image-signed: delegates to the container signature policy. I traced which policy would apply.

1. finpilot ships none. Searching the repo for policy.json / cosign / sigstore / containers returns nothing.

2. The common layer does ship one — but finpilot never installs it. build/10-build.sh:22 is the only rsync:

rsync -rvK /ctx/oci/brew/ /

There's no rsync of /ctx/oci/common/ and no COPY of it into the final image. Grepping oci/common across build/ and custom/ returns only the Containerfile ctx-stage line.

3. Even if it were installed, it wouldn't help. Its docker transport scopes are registry.access.redhat.com, registry.redhat.io, quay.io/toolbx-images, ghcr.io/ublue-os, plus the catch-all:

"": [ { "type": "insecureAcceptAnything" } ]

There's no ghcr.io/projectbluefin entry, so scope matching falls through to "" and accepts anything. The switch is exactly as unverified as --transport registry was.

4. registries.d/ublue-os.yaml sets use-sigstore-attachments: true only for ghcr.io/ublue-os. Without an equivalent for ghcr.io/projectbluefin, sigstore attachments aren't even fetched.

5. This repo signs keyless (README:276 — "keyless OIDC signing via Cosign … no cosign.key or cosign.pub files are required"). Every entry in that policy.json is keyPath/keyPaths, i.e. key-pair based. Keyless needs sigstoreSigned with fulcio/rekor configuration, which doesn't exist anywhere in this org's policy.

Failure wouldn't abort either

The block is a bare %post with no --erroronfail, so a non-zero bootc switch is logged and the install completes — leaving the machine booted on the unswitched Fedora Silverblue base rather than finpilot, silently.

What would make the title true

• ship /etc/containers/policy.json with a sigstoreSigned + fulcio/rekor entry scoped to ghcr.io/projectbluefin (or install common's and add that scope);
• add a registries.d entry enabling sigstore attachments for that scope;
• add %post --erroronfail so a rejected signature fails the install instead of silently producing a non-finpilot system.

If you'd rather land the consistency change now, I'd retitle to something like chore(disk): align iso bootc switch with 00-image-info transport and open a follow-up for the policy, so nobody reads this as verification being in place.

Cross-PR: this breaks #368

Git merges cleanly, but #368's drift gate hardcodes the string this PR removes:

ref="$(sed -n 's|^bootc switch .*--transport registry \(ghcr.io/[^ ]*\).*|\1|p' ...)"
[ -n "${ref}" ]

Merging both:

not ok 7 iso/iso.toml kickstart ref matches the canonical vendor and name
#   `[ -n "${ref}" ]' failed

Whichever lands second breaks main. #368's sed needs to accept both spellings — I've noted it there too.

Verified: bats tests/unit/ — 185 ok / 1 not ok on base dd3b1fd and unchanged here. The single failure (build: does not add a build secret when GITHUB_TOKEN is unset) is pre-existing on base.

One limit on the above: I couldn't pull container images, so I couldn't read the policy.json that Fedora Silverblue 44 actually ships. My conclusion rests on repo evidence. If the base image happened to ship a policy with a ghcr.io/projectbluefin sigstore entry that would change things — but given this repo signs keyless and no fulcio config exists anywhere in the org, I think that's very unlikely.

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[mrbobbytables]

Thanks @hanthor! Addressed the feedback:

1. Retitled for transport alignment: Updated PR title to chore(disk): align iso bootc switch with 00-image-info transport to accurately convey that this is consistency alignment rather than an assertion of end-to-end signature policy verification (which will be tracked in follow-up work for container policy/sigstore attachments).
2. %post --erroronfail: Added --erroronfail to the %post scriptlet in iso/iso.toml so that a non-zero exit from bootc switch fails the installation loudly rather than completing silently on the unmodified Silverblue base image.

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[kubestellar-hive]

Read the diff against the current tree; this looks correct to me.

• The transport change is consistent with the repo's existing trust model: build/00-image-info.sh:41 already sets IMAGE_REF="ostree-image-signed:docker://ghcr.io/${IMAGE_VENDOR}/${IMAGE_NAME}", so after this change the ISO install path verifies the same signed ref that in-place upgrades use, instead of the unsigned --transport registry path.
• %post --erroronfail is the right companion change: with signed transport, bootc switch can now legitimately fail (signature rejection), and without --erroronfail kickstart swallows that failure and the install completes on the unswitched base image. This makes verification failures visible at install time.
• The FORK NOTE update keeps the fork instructions consistent with the new command form.

Note for the maintainer: #357 makes the same core transport change for the same issue #330 but without --erroronfail and with a stale FORK NOTE; I've commented there recommending it be closed in favour of this PR.

Approval is a maintainer's call, but I found no defects.

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[kubestellar-hive]

Reviewed at head 8c6bf26.

High — this change likely makes every ISO install fail. iso/iso.toml:14 switches to bootc switch --mutate-in-place ostree-image-signed:docker://ghcr.io/projectbluefin/finpilot:stable, and iso/iso.toml:9 adds %post --erroronfail. The ostree-image-signed: transport delegates verification to /etc/containers/policy.json and refuses to pull when the matching policy is insecureAcceptAnything. Neither this PR nor the repo ships any policy.json / registries.d sigstore configuration for ghcr.io/projectbluefin/finpilot (nothing in Containerfile or build/), and the Fedora base image's default policy is insecureAcceptAnything — so the signed pull is rejected, and with --erroronfail the kickstart %post now aborts the installation instead of silently leaving the base image.

PR body vs. diff: the body claims this "ensures cosign signature verification against Fulcio/Rekor at ISO install time." The diff (iso/iso.toml:14) only changes the transport string; keyless Fulcio/Rekor verification would additionally require a sigstoreSigned policy entry (with fulcio/rekor config) plus registries.d use-sigstore-attachments in the image. Without those, this is not verification — it's a hard failure.

Nit: the FORK NOTE at iso/iso.toml:11 now tells forkers the ref "must match the package that build-image.yml publishes," but the ref shown now embeds the transport prefix, which is not part of the published package name.

Suggested fix: ship a policy.json/registries.d sigstore configuration in the image (then this transport works as intended), or keep the unsigned transport until that lands.

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