These are copy-paste reference workflows for producing SLSA provenance with the Packer provenance post-processor. They are not wired into this repository's own CI — copy them into your project's .github/workflows/ directory and adapt the template and artifact paths.

SLSA levels and Packer

SLSA Build levels are mostly properties of the build platform, not the build tool. Packer is a tool, so its reach is:

SLSA Build level	Requirement	Packer's role	What Packer provides
L1	Provenance exists and is distributed	Fully in Packer	Provenance generation
L2	Provenance signed by a hosted platform	Packer signs via CI OIDC identity	Keyless signing in CI
L3	Hardened platform; build steps cannot reach the signing key	Platform property; Packer is compatible	Delegated-signing pattern
L4	—	Not defined in SLSA v1.0	—

Packer generates SLSA Provenance v1 and reaches Build L1, and L2 when run on a hosted CI with keyless signing. L3 is a property of the build platform: it requires the signing key to be unreachable by the build steps. Packer does not confer L3 on its own, but the delegated-signing pattern below is compatible with an L3 platform.

Workflows

github-actions-l2-keyless.yml — L2: Packer signs provenance keyless using the workflow's OIDC identity, uploads to Rekor, and verifies the signed attestation with packer verify-attestation.
github-actions-l3-delegated.yml — L3-compatible: the build job only builds and publishes a digest; provenance generation and signing are delegated to an isolated reusable workflow so the build steps cannot reach the signing material.