Signing and Verification Workflows

These workflows form the trust enforcement spine of the attested-delivery architecture. The attestation seam turns gate evidence into enforceable claims; the verification workflows fail closed if claims do not verify before deployment.

Signing identity model (SLSA Build L3): Under SLSA L3 the Fulcio SAN is the signer workflow, not the source repo. --owner or --repo alone is insufficient for seam-signed predicates. Always pin --signer-workflow in any gh attestation verify call, one signer per command.

Calling convention: reference every workflow by the .github repo’s full 40-char commit SHA:

uses: attested-delivery/.github/.github/workflows/<name>.yml@<sha> # vX.Y.Z

---

reusable-attest-scan.yml

The attestation seam. Turns any quality gate’s evidence file — a SARIF, a JSON report, an OpenVEX document — into a signed, digest-bound in-toto attestation via GitHub keyless signing (actions/attest, custom predicate). A clean code-scanning result is evidence; this attestation is the enforceable, verifiable claim bound to a subject by digest and signed by this central workflow’s OIDC identity.

Signer identity (Fulcio SAN): https://github.com/attested-delivery/.github/.github/workflows/reusable-attest-scan.yml@<ref>

Predicate type: caller-specified. Use any URI from the custom predicate namespace or a standard predicate URI.

Inputs

Name	Type	Required	Description
subject-name	string	yes	Logical subject name (image repo, package name, or artifact label)
subject-digest	string	yes	Subject digest the predicate is bound to (sha256:...)
predicate-type	string	yes	URI identifying the predicate type (e.g. https://attested-delivery.github.io/attestations/sast/v1)
predicate-artifact	string	yes	Name of the uploaded artifact containing the evidence file
predicate-filename	string	yes	Evidence filename within the artifact (e.g. results.sarif)

Required caller permissions

permissions:
  id-token: write        # keyless Sigstore signing
  attestations: write    # persist the GitHub artifact attestation
  contents: read

Allow-list entries required

GitHub-created actions/download-artifact and actions/attest only.

Verification

gh attestation verify <subject> \
  --owner attested-delivery \
  --predicate-type https://attested-delivery.github.io/attestations/sast/v1 \
  --signer-workflow attested-delivery/.github/.github/workflows/reusable-attest-scan.yml

Replace the predicate type with the gate’s predicate URI. Each predicate type requires a separate gh attestation verify command.

Minimal caller snippet

jobs:
  attest-sast:
    needs: [build, sast]
    permissions:
      id-token: write
      attestations: write
      contents: read
    uses: attested-delivery/.github/.github/workflows/reusable-attest-scan.yml@<sha>
    with:
      subject-name: my-app
      subject-digest: ${{ needs.build.outputs.digest }}
      predicate-type: https://attested-delivery.github.io/attestations/sast/v1
      predicate-artifact: ${{ needs.sast.outputs.sarif-artifact }}
      predicate-filename: ${{ needs.sast.outputs.sarif-filename }}

---

reusable-verify-gates.yml

Fail-closed verification of gate attestations. Runs gh attestation verify for each required predicate type against a subject and exits non-zero on any failure. Place in a deploy job’s needs: to halt an unverified artifact before it ships.

One signer per invocation. Different predicates are signed by different workflows — the seam (reusable-attest-scan.yml) signs the SARIF gates, reusable-vex.yml signs OpenVEX, reusable-k6.yml signs performance. Mixing predicates from different signers in a single call will fail closed on a valid artifact. Call this workflow once per signer group.

An empty predicate-types input fails closed immediately — the workflow refuses to “verify” with no required predicate.

Inputs

Name	Type	Required	Description
subject-ref	string	yes	Subject to verify (oci://...@sha256 or a file path)
owner	string	yes	Repository owner that produced the attestations
signer-workflow	string	yes	The single signer workflow for all predicate types in this call (e.g. attested-delivery/.github/.github/workflows/reusable-attest-scan.yml for seam-signed gates)
predicate-types	string	yes	Newline- or whitespace-separated predicate type URIs; at least one required

Required caller permissions

permissions:
  contents: read
  attestations: read
  packages: read

Allow-list entries required

None — uses the inline gh CLI.

Minimal caller snippet

jobs:
  verify-seam:
    permissions:
      contents: read
      attestations: read
      packages: read
    uses: attested-delivery/.github/.github/workflows/reusable-verify-gates.yml@<sha>
    with:
      subject-ref: oci://ghcr.io/attested-delivery/app@sha256:...
      owner: attested-delivery
      signer-workflow: attested-delivery/.github/.github/workflows/reusable-attest-scan.yml
      predicate-types: |-
        https://attested-delivery.github.io/attestations/sast/v1
        https://attested-delivery.github.io/attestations/sca/v1

  verify-vex:
    permissions:
      contents: read
      attestations: read
      packages: read
    uses: attested-delivery/.github/.github/workflows/reusable-verify-gates.yml@<sha>
    with:
      subject-ref: oci://ghcr.io/attested-delivery/app@sha256:...
      owner: attested-delivery
      signer-workflow: attested-delivery/.github/.github/workflows/reusable-vex.yml
      predicate-types: https://openvex.dev/ns/v0.2.0

  deploy:
    needs: [verify-seam, verify-vex]
    # ...

---

sign-and-attest.yml

Sign and attest a built container image by digest. This workflow is the SLSA Build L3 isolation boundary: callers invoke it via uses: and cannot modify the signing steps, so the provenance signer identity is this central workflow’s job_workflow_ref, not the caller’s. Image-only — not for static artifacts.

Performs: SLSA build provenance (actions/attest-build-provenance), keyless cosign signature, CycloneDX SBOM (optional), and a Grype vulnerability scan (optional). Self-verifies SLSA provenance before completing.

Predicates produced (self-signed):

• https://slsa.dev/provenance/v1 (via actions/attest-build-provenance, pushed as OCI referrer)
• CycloneDX SBOM (via inline cosign attest --type cyclonedx)
• https://in-toto.io/attestation/vulns/v0.1 (via inline cosign attest)

Signer identity (Fulcio SAN for cosign): ^https://github.com/attested-delivery/\.github/\.github/workflows/sign-and-attest\.yml@.*$

Inputs

Name	Type	Required	Default	Description
image-name	string	yes	—	Image repository without tag or digest (e.g. ghcr.io/attested-delivery/app)
image-digest	string	yes	—	Immutable image digest from the caller’s build (sha256:...)
sbom	boolean	no	true	Generate and attest a CycloneDX SBOM
vuln-scan	boolean	no	true	Generate and attest a Grype vulnerability report
cosign-version	string	no	v3.0.6	cosign release to install

Outputs

Name	Description
provenance-verified	true when the in-run gh attestation verify of SLSA provenance passed

Required caller permissions

Top-level permissions: {} in the caller. The internal job attest requires:

permissions:
  id-token: write       # OIDC token for Sigstore keyless signing
  attestations: write   # persist GitHub artifact attestation
  packages: write       # push referrers to GHCR
  contents: read

Allow-list entries required

sigstore/cosign-installer, docker/login-action, anchore/sbom-action, anchore/scan-action. GitHub-created actions/attest-build-provenance.

Verification (post-build)

# SLSA provenance
gh attestation verify "oci://${IMAGE_REF}" \
  --repo <caller-repo> \
  --signer-workflow attested-delivery/.github/.github/workflows/sign-and-attest.yml \
  --predicate-type https://slsa.dev/provenance/v1

# cosign signature
cosign verify "${IMAGE_REF}" \
  --certificate-identity-regexp '^https://github\.com/attested-delivery/\.github/\.github/workflows/sign-and-attest\.yml@.*$' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

Minimal caller snippet

jobs:
  sign:
    permissions: {}
    uses: attested-delivery/.github/.github/workflows/sign-and-attest.yml@<sha>
    with:
      image-name: ghcr.io/attested-delivery/app
      image-digest: ${{ needs.build.outputs.digest }}

---

verify-attestation.yml

Fail-closed verification of a container image’s signature and attestations between registry hops or before deploy. Pins the expected signing identity to sign-and-attest.yml. Image-only; reused by promotion pipelines and callable before any deploy.

Verifies: cosign keyless signature, SLSA provenance (gh attestation verify), and optionally the CycloneDX SBOM attestation.

Inputs

Name	Type	Required	Default	Description
image-ref	string	yes	—	Fully-qualified image ref by digest (registry/repo@sha256:...)
attestation-repo	string	yes	—	owner/repo that produced the attestation (for gh attestation verify)
certificate-identity-regexp	string	no	^https://github.com/attested-delivery/\.github/\.github/workflows/sign-and-attest\.yml@.*$	Expected Fulcio cert identity
certificate-oidc-issuer	string	no	https://token.actions.githubusercontent.com	OIDC issuer
signer-workflow	string	no	attested-delivery/.github/.github/workflows/sign-and-attest.yml	Signer workflow for gh attestation verify
require-sbom	boolean	no	true	Verify the CycloneDX SBOM attestation
aws-role-arn	string	no	''	If set, assume this role and log into ECR before verifying
aws-region	string	no	us-east-1	AWS region (used when aws-role-arn is set)

Required caller permissions

Top-level permissions: {} in the caller. The internal job verify requires:

permissions:
  id-token: write
  contents: read
  packages: read
  attestations: read

Allow-list entries required

sigstore/cosign-installer, docker/login-action. When aws-role-arn is set: aws-actions/configure-aws-credentials, aws-actions/amazon-ecr-login.

Minimal caller snippet

jobs:
  verify:
    permissions: {}
    uses: attested-delivery/.github/.github/workflows/verify-attestation.yml@<sha>
    with:
      image-ref: ghcr.io/attested-delivery/app@sha256:...
      attestation-repo: attested-delivery/my-repo

---

reusable-cosign-sign.yml

Keyless blob signing for plain files (e.g. a marketplace.json catalog) that are not registry packages. Signs with Sigstore cosign keyless signing (short-lived Fulcio certificate bound to this workflow’s OIDC identity, witnessed in Rekor), then verifies the bundle back in-run (fail-closed). Consumers re-verify with cosign verify-blob.

Signer identity (Fulcio SAN): ^https://github\.com/attested-delivery/\.github/\.github/workflows/reusable-cosign-sign\.yml@

Inputs

Name	Type	Required	Default	Description
blob-path	string	yes	—	Path to the file (blob) to sign
cosign-version	string	no	v3.1.1	Pinned cosign release to install

Outputs

Name	Description
bundle-artifact	Artifact name holding the cosign bundle (cosign-bundle)
bundle-filename	cosign bundle filename within the artifact (e.g. marketplace.json.cosign.bundle)
certificate-identity	Regex matching the keyless signer identity for use in cosign verify-blob by consumers

Required caller permissions

permissions:
  id-token: write    # keyless Sigstore signing
  contents: read

Allow-list entries required

sigstore/cosign-installer.

Consumer verification

cosign verify-blob <blob-path> \
  --bundle <bundle-file> \
  --certificate-identity-regexp '^https://github\.com/attested-delivery/\.github/\.github/workflows/reusable-cosign-sign\.yml@' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

Minimal caller snippet

jobs:
  sign-catalog:
    permissions:
      id-token: write
      contents: read
    uses: attested-delivery/.github/.github/workflows/reusable-cosign-sign.yml@<sha>
    with:
      blob-path: .claude-plugin/marketplace.json

---

See also

• Quality Gate Workflows — the SARIF gates that feed the seam
• CI and Pinning Workflows — pin-check, actionlint, catalog-check
• How-to: Verify a release
• How-to: Onboard a repo
• Concept: Attestations that survive promotion
• Concept: Enforce at admission, not by convention
• Concept: SLSA L3 is nearly free