Every release tarball, the Docker image, the binary completions archive, and the SBOM that ships alongside them are signed via Sigstore keyless signing. There are no public keys to track — the signing identity is the GitHub Actions workload identity running in FerrLabs/FerrFlow, anchored in the public Rekor transparency log.

Available since v5.2.

What ships per release

Artifact	Sidecars
ferrflow-linux-x64.tar.gz	.sig, .crt
ferrflow-linux-arm64.tar.gz	.sig, .crt
ferrflow-darwin-x64.tar.gz	.sig, .crt
ferrflow-darwin-arm64.tar.gz	.sig, .crt
ferrflow-windows-x64.zip	.sig, .crt
ferrflow-completions.tar.gz	.sig, .crt
sbom.cdx.json	.sig, .crt
ghcr.io/ferrlabs/ferrflow:vX.Y.Z	Cosign signature in GHCR + Rekor

All sidecars are downloadable from the GitHub Release page next to the binary.

Verifying a tarball

# install cosign (one-time)
curl -L https://github.com/sigstore/cosign/releases/latest/download/cosign-linux-amd64 \
  -o /usr/local/bin/cosign && chmod +x /usr/local/bin/cosign

# download the artifact + sidecars from the release page
TAG=v5.2.3
gh release download "$TAG" --repo FerrLabs/FerrFlow \
  -p 'ferrflow-linux-x64.tar.gz*'

# verify
cosign verify-blob \
  --certificate ferrflow-linux-x64.tar.gz.crt \
  --signature   ferrflow-linux-x64.tar.gz.sig \
  --certificate-identity-regexp "https://github.com/FerrLabs/FerrFlow/.*" \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  ferrflow-linux-x64.tar.gz
# → Verified OK

A passing verification means:

• The tarball bytes haven't been tampered with since the release workflow signed them.
• The signing identity was a workflow running in FerrLabs/FerrFlow triggered by GitHub Actions' OIDC issuer.
• The signature is recorded in the public Rekor log — search search.sigstore.dev for the .sig value.

Verifying the Docker image

cosign verify ghcr.io/ferrlabs/ferrflow:v5.2.3 \
  --certificate-identity-regexp "https://github.com/FerrLabs/FerrFlow/.*" \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

Verifying the SBOM

The SBOM (sbom.cdx.json) is a CycloneDX document listing every transitive dependency of the published binary. It's signed the same way as the tarballs:

cosign verify-blob \
  --certificate sbom.cdx.json.crt \
  --signature   sbom.cdx.json.sig \
  --certificate-identity-regexp "https://github.com/FerrLabs/FerrFlow/.*" \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com \
  sbom.cdx.json

Feed the verified SBOM into your scanner of choice — Grype, Trivy, Snyk, JFrog Xray, Anchore, anything CycloneDX-aware.

SLSA build provenance

In addition to Sigstore signatures, every release also ships a SLSA build provenance attestation generated via actions/attest-build-provenance. It records the workflow run, the source commit SHA, and the build inputs.

gh attestation verify ferrflow-linux-x64.tar.gz --repo FerrLabs/FerrFlow

What's not signed

Source tarballs from git archive (the auto-generated "Source code (zip)" and "Source code (tar.gz)" assets on the GitHub Release page) come from GitHub, not from the release workflow, and have no .sig/.crt sidecars. If you need an attestation for source, use gh attestation verify against the build provenance bundle instead.

Why this matters

• Supply-chain attacks. An attacker who compromises a CDN, a mirror, or pushes a typosquat package can't forge the signature — the signing identity is anchored to the GitHub Actions OIDC flow.
• Compliance. SOC 2 / ISO 27001 customers can attest that the binary they pulled is what their auditor approved.
• No key management. Nobody at FerrLabs has a private signing key to lose or rotate. The workflow proves its identity at the moment of signing.