Demo 6 — Plugin OCI artefact loader

Module brief: §Module 6

UVP

Distribute plugins like containers — .tar.gz with manifest + wasm + signature. The proxy ingests them directly; no extraction step.

Use cases

Plugin marketplaces. A registry serves <name>-<version>.tar.gz artefacts; operators curl | tar -tzf to inspect, drop in plugin dir, the proxy validates.
Reproducible builds. Manifest’s wasm_sha256 lets CI verify the same bytes shipped to every environment.
Signed releases. The plugin.sig inside the artefact uses the same Ed25519 trust root as Demo 5.

What this demo shows

# 1. Build the plugin (one-time, cached)
cd ../../../../HDB-HeliosDB-Proxy-Plugins
cargo build -p helios-plugin-cost-governor \
  --target wasm32-unknown-unknown --release

# 2. Pack it
helios-plugin pack \
  --wasm target/wasm32-unknown-unknown/release/helios_plugin_cost_governor.wasm \
  --name helios-plugin-cost-governor \
  --version 0.1.0 \
  --hooks pre_query,post_query \
  --out cost-governor-0.1.0.tar.gz

# 3. Inspect — proves the manifest survived the round-trip
helios-plugin inspect cost-governor-0.1.0.tar.gz
#   {
#     "schema_version": "1.0",
#     "name": "helios-plugin-cost-governor",
#     "version": "0.1.0",
#     "hooks": ["pre_query", "post_query"],
#     "wasm_sha256": "09889579082ab18f72955a8754b63143afd694e97cf7684061ba7f53d6f13e4c",
#     "packed_at": "2026-04-26T..."
#   }

# 4. Drop in plugin dir — proxy loads directly
cp cost-governor-0.1.0.tar.gz demos/v0.4.0/06-plugin-oci/plugins/
cd demos/v0.4.0/06-plugin-oci
./demo.sh

The proxy log shows the artefact loading:

INFO loaded plugin helios-plugin-cost-governor v0.1.0 from cost-governor-0.1.0.tar.gz
INFO   wasm_sha256 verified: 09889579082ab18f72955a8754b63143afd694e97cf7684061ba7f53d6f13e4c

Tamper proof — change one byte in the tarball and the loader refuses:

# Flip a byte in the middle of the tarball
printf '\xff' | dd of=plugins/cost-governor-0.1.0.tar.gz bs=1 count=1 \
  conv=notrunc seek=5000
docker compose restart proxy
# → "wasm sha256 mismatch: manifest claims X, actual Y"

Implementation pointer

src/plugins/loader.rs::load_tar_gz — detects .gz extension, unpacks via tar + flate2, validates SHA-256, optionally verifies signature via the same SignatureVerifier from Demo 5. CLI side at HDB-HeliosDB-Proxy-Plugins/cli/src/artefact.rs.

HeliosDB compatibility

Backend-agnostic — artefact handling is pure proxy-side.