Trust

A signed result is reused only if your policy trusts the signer. The result cannot vouch for itself.

flowchart LR
  ci[CI job] --> r[signed result]
  dev[developer key] --> r
  r --> sig{valid<br>signature?}
  sig -- no --> fail([verification-failed<br>exit 5]):::err
  sig -- yes --> who{signer in<br>the policy?}
  who -- no --> fail
  who -- yes --> lvl{level high<br>enough?}
  lvl -- no --> miss([miss<br>exit 4]):::muted
  lvl -- yes --> ok([verified<br>reuse]):::ok

Signers

A signer is who signed a result. There are two kinds:

• A CI job (keyless). The job signs with a short-lived certificate from Sigstore, tied to its OIDC identity, such as one GitHub Actions workflow on main.
• A key. A developer signs with a local key file.

Trust levels

Your policy gives each signer a trust level:

Level	Name	Use it for
1	developer	skip a test you already ran on your own machine
2	runner	reuse in CI: a CI job with a verifiable identity
3	isolated	reuse even when the runner host is not trusted

The predicate inside a result also claims a level. Aval ignores that claim: the level always comes from your policy.

The policy

A policy is a YAML file you keep in your repository. This one trusts the main branch workflow for CI reuse, and Alice's key at developer level:

apiVersion: aval.trianalab.io/v1
kind: Policy
minTrustLevel: runner
identities:
  - issuer: https://token.actions.githubusercontent.com
    subjectRegexp: https://github\.com/acme/orders/\.github/workflows/ci\.yaml@refs/heads/main
    trustLevel: runner
  - publicKey: keys/alice.pub
    trustLevel: developer

With minTrustLevel: runner, a result Alice signed is a miss: the test runs. Without --policy, nothing is trusted and every test runs.

What a signature proves

• Proves: who signed the result, and that nobody changed it since.
• Does not prove: that the test ran honestly, or that inputs outside the contract were the same.

So only grant a level to signers you would trust to run the test yourself.

The full spec

The trust model covers keyless verification, the policy fields and the threats Aval defends against.