# Mirror bundle signing runbook (CI)

## Prerequisites
- Ed25519 private key (PEM). Keep in CI secrets only.
- Base64-encode the PEM: `base64 -w0 mirror-ci-ed25519.pem > mirror-ci-ed25519.pem.b64`.
- Create CI secret `MIRROR_SIGN_KEY_B64` with that value.

## Pipeline step (Gitea example)
```
- name: Build/sign mirror thin bundle
  env:
    MIRROR_SIGN_KEY_B64: ${{ secrets.MIRROR_SIGN_KEY_B64 }}
    REQUIRE_PROD_SIGNING: 1
    OCI: 1
    TENANT_SCOPE: tenant-demo
    ENV_SCOPE: lab
  run: |
    scripts/mirror/check_signing_prereqs.sh
    scripts/mirror/ci-sign.sh
```
Outputs are placed under `out/mirror/thin/` and `out/mirror/thin/oci/`; archive these as artifacts.

### How to add the secret in Gitea (one-time)
1. Repository → Settings → Secrets.
2. New secret: name `MIRROR_SIGN_KEY_B64`, value = base64-encoded Ed25519 PEM (no newlines, no header/footer).
3. Scope: repository (or environment-specific if needed).
4. Save. The pipeline step will skip if the secret is empty; keep it present in release branches only.

## Local dry-run with test key
```
MIRROR_SIGN_KEY_B64=$(base64 -w0 out/mirror/thin/tuf/keys/mirror-ed25519-test-1.pem) \
OCI=1 scripts/mirror/ci-sign.sh
```

## Temporary dev key (to unblock CI until production key is issued)
Use this throwaway Ed25519 key only for non-production runs. Generated 2025-11-24 to replace the previous placeholder; rotate TUF metadata immediately after swapping in the production key.

```
MIRROR_SIGN_KEY_B64=LS0tLS1CRUdJTiBQUklWQVRFIEtFWS0tLS0tCk1DNENBUUF3QlFZREsyVndCQ0lFSUxGdFMwbjBpMVVueE1maGt0cDNlY1N4WHVxYmcrVFJuaENhS05jaGtTbFIKLS0tLS1FTkQgUFJJVkFURSBLRVktLS0tLQo=
```

**Do not ship with this key.** Set `REQUIRE_PROD_SIGNING=1` for release/tag builds so they fail without the real key. Add the production key as a Gitea secret (`MIRROR_SIGN_KEY_B64`) and rerun the workflow; remove this temporary key block once rotated.

## Verification
The CI step already runs `scripts/mirror/verify_thin_bundle.py --bundle-meta mirror-thin-v1.bundle.json --tenant $TENANT_SCOPE --environment $ENV_SCOPE --pubkey out/mirror/thin/tuf/keys/ci-ed25519.pub` so offline-kit policies (OK1–OK10), Rekor policy (RK1–RK10), and mirror-format policy (MS1–MS10) are validated alongside the tarball. For OCI, ensure `out/mirror/thin/oci/index.json` references the manifest digest.

`milestone.json` now carries manifest/tar/bundle/bundle-dsse hashes plus policy layer hashes to allow air-gapped import verification.

## Fallback (if secret absent)
- CI can fall back to an embedded test Ed25519 key when `MIRROR_SIGN_KEY_B64` is unset **only when `REQUIRE_PROD_SIGNING` is not set**. This is for dev smoke runs; release/tag jobs must set `REQUIRE_PROD_SIGNING=1` to forbid fallback.
- For release branches, always set `REQUIRE_PROD_SIGNING=1` and provide `MIRROR_SIGN_KEY_B64`; otherwise the step will fail early.