Two interlocking pieces shipped together:
1. Strict Ed25519 signature verification on URL-fetched apps artifacts.
Every URL the apps cascade resolves must publish a corresponding
<url>.sig (raw 64-byte Ed25519 signature). The fetcher rejects on
any failure (sig 404, transport error, wrong key, tampered body)
and the resolver falls back to the embedded copy.
The trusted public key is OPERATOR-CONFIGURED via --apps-pubkey /
ZDDC_APPS_PUBKEY (PEM file path). No baked-in default — same posture
as TLS certificates. Operators using zddc.varasys.io's canonical
channels download pubkey.pem from there and configure the local
path. Operators with their own signing infrastructure pass their
own public key.
Build pipeline (./build) gains sign_release_artifacts: walks
dist/release-output/ after promote and produces an Ed25519 .sig
alongside every real file. ZDDC_SIGNING_KEY=~/.config/zddc-signing/
key.pem (mode 0600). Symlinks skip — the .sig at the symlink
target is what counts.
Test coverage: parse-PEM round-trip, malformed/wrong-type PEM
rejection, valid-signature accept, tampered-body reject, wrong-key
reject, malformed-signature reject, end-to-end fetch+sign+verify,
fetch-rejects-tampered, fetch-rejects-missing-sig, fetch-rejects-
wrong-key. Existing fetch tests updated to use signed-fixture
helpers.
2. Dev Helm chart mounts production data READ-ONLY and layers an
OverlayFS writable scratch on top. Prod data is the lowerdir;
dev's writes (form submissions, archive index state, .zddc edits)
land in upperdir; main container sees the merged read-write view
at $ZDDC_ROOT. Setup runs in a privileged init container; main
container runs unprivileged. Solves the dev-replica-on-shared-
dataset problem at the filesystem layer with no zddc-server code
change.
Docs: env-var tables in zddc/README.md and AGENTS.md gain a
ZDDC_APPS_PUBKEY row. The Federal-readiness gap analysis "Code-signed
apps: URL fetches" subsection is rewritten as "what's currently in
place" instead of "what would need to be added," with a forward
pointer to per-entry signed_by: (multi-key) and Sigstore as the
federally-acceptable evolution.
The website "Verify your downloads" section + the embedded pubkey
gone — but the website needs separate updates landing in zddc-website
to publish pubkey.pem and add the verify section. Pending in that
repo's commit.
Production binary unchanged at 13.1 MB. All 11 Go test packages green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
