SLSA and Artifact Signing with Sigstore

Implementing build provenance and cosign signatures for container images and release binaries.

SLSA and Artifact Signing with Sigstore

SLSA levels (simplified)

Level	Requirement
L1	Build scripted / automated
L2	Signed provenance, hosted build
L3	Hardened build platform, non-falsifiable provenance

Cosign signing flow


# Sign image after build
cosign sign --key awskms://alias/cosign myregistry/app:v1.2.3
 
# Verify at deploy time (admission webhook or deploy script)
cosign verify --key awskms://alias/cosign myregistry/app:v1.2.3

Provenance attestation

GitHub Actions can emit SLSA provenance linking:

Git commit SHA
Workflow file
Builder identity
Artifact digest

Store attestations alongside image in OCI registry.

Policy

Production deploy pipeline rejects images without:

Valid cosign signature from trusted key
Provenance matching allowed repository and branch
Passing vulnerability scan on same digest