git.stella-ops.org/docs/dev/BUILDX_PLUGIN_QUICKSTART.md

BuildX Generator Quickstart

This quickstart explains how to run the StellaOps BuildX SBOM generator offline, verify the CAS handshake, and emit OCI descriptors that downstream services can attest.

1. Prerequisites

• Docker 25+ with BuildKit enabled (docker buildx available).
• .NET 10 (preview) SDK matching the repository global.json.
• Optional: network access to a StellaOps Attestor endpoint (the quickstart uses a mock service).

2. Publish the plug-in binaries

The BuildX generator publishes as a .NET self-contained executable with its manifest under plugins/scanner/buildx/.

# From the repository root
DOTNET_CLI_HOME="${PWD}/.dotnet" \
dotnet publish src/Scanner/StellaOps.Scanner.Sbomer.BuildXPlugin/StellaOps.Scanner.Sbomer.BuildXPlugin.csproj \
  -c Release \
  -o out/buildx

• out/buildx/ now contains StellaOps.Scanner.Sbomer.BuildXPlugin.dll and the manifest stellaops.sbom-indexer.manifest.json.
• plugins/scanner/buildx/StellaOps.Scanner.Sbomer.BuildXPlugin/ receives the same artefacts for release packaging.
• The CI pipeline also tars and signs (SHA-256 manifest) the OS analyzer plug-ins located under plugins/scanner/analyzers/os/ so they ship alongside the BuildX generator artefacts.

3. Verify the CAS handshake

dotnet out/buildx/StellaOps.Scanner.Sbomer.BuildXPlugin.dll handshake \
  --manifest out/buildx \
  --cas out/cas

The command performs a deterministic probe write (sha256) into the provided CAS directory and prints the resolved path.

4. Emit a descriptor + provenance placeholder

1. Build or identify the image you want to describe and capture its digest:

   docker buildx build --load -t stellaops/buildx-demo:ci samples/ci/buildx-demo
   DIGEST=$(docker image inspect stellaops/buildx-demo:ci --format '{{index .RepoDigests 0}}')
   

2. Generate a CycloneDX SBOM for the built image (any tool works; here we use docker sbom):

   docker sbom stellaops/buildx-demo:ci --format cyclonedx-json > out/buildx-sbom.cdx.json
   

3. Invoke the descriptor command, pointing at the SBOM file and optional metadata:

   dotnet out/buildx/StellaOps.Scanner.Sbomer.BuildXPlugin.dll descriptor \
     --manifest out/buildx \
     --image "$DIGEST" \
     --sbom out/buildx-sbom.cdx.json \
     --sbom-name buildx-sbom.cdx.json \
     --artifact-type application/vnd.stellaops.sbom.layer+json \
     --sbom-format cyclonedx-json \
     --sbom-kind inventory \
     --repository git.stella-ops.org/stellaops/buildx-demo \
     --build-ref $(git rev-parse HEAD) \
     > out/buildx-descriptor.json
   

The output JSON captures:

• OCI artifact descriptor including size, digest, and annotations (org.stellaops.*).
• Provenance placeholder (expectedDsseSha256, nonce, attestorUri when provided). nonce is derived deterministically from the image + SBOM metadata so repeated runs produce identical placeholders for identical inputs.
• Generator metadata and deterministic timestamps.

4.1 Persist Surface manifests & payloads (optional)

Pass the new --surface-* switches to the descriptor command whenever you have Surface artefacts (layer fragments, EntryTrace graph/NDJSON) that should be cached during build-time scans. The plug-in stores the payloads under the configured CAS root (defaults to --cas) and emits a manifest pointer that Scanner/WebService can consume later.

dotnet out/buildx/StellaOps.Scanner.Sbomer.BuildXPlugin.dll descriptor \
  --manifest out/buildx \
  --image "$DIGEST" \
  --sbom out/buildx-sbom.cdx.json \
  --surface-layer-fragments out/layer-fragments.json \
  --surface-entrytrace-graph out/entrytrace-graph.json \
  --surface-entrytrace-ndjson out/entrytrace.ndjson \
  --surface-cache-root out/cas \
  --surface-tenant demo-tenant \
  --surface-manifest-output out/surface-manifest.json \
  > out/buildx-descriptor.json

Environment variables mirror the CLI flags when you need deterministic defaults:

Variable	Purpose
STELLAOPS_SURFACE_CACHE_ROOT	CAS/cache directory used for Surface artefacts (defaults to --cas).
STELLAOPS_SURFACE_BUCKET	Bucket name embedded in cas:// URIs (default scanner-artifacts).
STELLAOPS_SURFACE_TENANT	Tenant recorded in the manifest (default if omitted).
STELLAOPS_SURFACE_LAYER_FRAGMENTS / ...ENTRYTRACE_GRAPH / ...ENTRYTRACE_NDJSON	File paths for the respective artefacts.
STELLAOPS_SURFACE_MANIFEST_OUTPUT	Optional path where the manifest JSON should be duplicated for CI artefacts.

Manifests and payloads use the same deterministic layout as Scanner.Worker (scanner/surface/...) so WebService and Offline Kit tooling can consume them without rescanning the image.

5. (Optional) Send the placeholder to an Attestor

The plug-in can POST the descriptor metadata to an Attestor endpoint, returning once it receives an HTTP 202.

python3 - <<'PY' &
from http.server import BaseHTTPRequestHandler, HTTPServer
class Handler(BaseHTTPRequestHandler):
    def do_POST(self):
        _ = self.rfile.read(int(self.headers.get('Content-Length', 0)))
        self.send_response(202); self.end_headers(); self.wfile.write(b'accepted')
    def log_message(self, fmt, *args):
        return
server = HTTPServer(('127.0.0.1', 8085), Handler)
try:
    server.serve_forever()
except KeyboardInterrupt:
    pass
finally:
    server.server_close()
PY
MOCK_PID=$!

dotnet out/buildx/StellaOps.Scanner.Sbomer.BuildXPlugin.dll descriptor \
  --manifest out/buildx \
  --image "$DIGEST" \
  --sbom out/buildx-sbom.cdx.json \
  --attestor http://127.0.0.1:8085/provenance \
  --attestor-token "$STELLAOPS_ATTESTOR_TOKEN" \
  > out/buildx-descriptor.json

kill $MOCK_PID

Set STELLAOPS_ATTESTOR_TOKEN (or pass --attestor-token) when the Attestor requires bearer authentication. Use --attestor-insecure for lab environments with self-signed certificates.

6. CI workflow example

A reusable GitHub Actions workflow is provided under samples/ci/buildx-demo/github-actions-buildx-demo.yml. It publishes the plug-in, runs the handshake, builds the demo image, emits a descriptor, and uploads both the descriptor and the mock-Attestor request as artefacts.

Add the workflow to your repository (or call it via workflow_call) and adjust the SBOM path + Attestor URL as needed. The workflow also re-runs the descriptor command and diffs the results (ignoring the generatedAt timestamp) so you catch regressions that would break deterministic CI use.

---

For deeper integration guidance (custom SBOM builders, exporting DSSE bundles), track ADRs in docs/modules/scanner/architecture.md §7 and follow upcoming Attestor API releases.