verifier

install/verifier

Installs slsa-verifier into the runner and adds it to the PATH, verifying the release before trusting it.

- uses: slsa-framework/actions/install/verifier@<sha>
  with:
    version: v0.1.0        # optional; defaults to the release the action pins
- run: slsa-verifier build --require-signatures provenance.intoto.jsonl app.tgz

How the release is verified

The action does not trust a download because it came from GitHub. Before installing, the AMPEL policy engine — bootstrapped by its own checksum-pinned installer — evaluates the release's published attestations.intoto.jsonl against a pinned policy, requiring that

• the binary is a subject of the provenance,
• the provenance names the repository's release.yaml workflow as the builder, and
• it was signed by that workflow running at the requested tag (Sigstore identity from GitHub's OIDC issuer).

Only then is the binary installed. A new release is adopted by bumping DEFAULT_VERSION in download.sh and the default version of the actions.

Inputs

Input	Default	Meaning
version	the release the action pins	Release tag to install
install-dir	$HOME/.slsa	Install directory; the binary lands in its bin/
repo	slsa-framework/verifier	Repository publishing the releases
verify	true	Verify the release against its provenance before installing

Outputs

Output	Meaning
path	Absolute path of the installed binary
bin-dir	Directory added to the PATH
version	Release that was installed

The verify/* actions run this script themselves, so a workflow that uses them does not need this action.