From 72b4157b244fa3dfe67bfd4607e175ba8da9cf34 Mon Sep 17 00:00:00 2001
From: Imran Siddique <imran.siddique@opaque.co>
Date: Sun, 5 Jul 2026 15:00:09 -0700
Subject: [PATCH] ci: sign published images (keyless cosign) and attest SLSA
 build provenance

Images pushed to ghcr.io were unsigned with no provenance. Add keyless cosign
signing of the pushed image by digest (OIDC, no keys) and an
actions/attest-build-provenance SLSA provenance attestation pushed to the registry.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .github/workflows/docker.yml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index 21c84b8..152b278 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -14,6 +14,8 @@ jobs:
     permissions:
       contents: read
       packages: write
+      id-token: write       # keyless cosign signing + provenance attestation (OIDC)
+      attestations: write   # actions/attest-build-provenance
 
     steps:
       - name: Checkout
@@ -31,6 +33,7 @@ jobs:
         run: echo "tag=${GITHUB_REF#refs/tags/}" >> "$GITHUB_OUTPUT"
 
       - name: Build and push
+        id: build
         uses: docker/build-push-action@v7
         with:
           context: .
@@ -38,3 +41,18 @@ jobs:
           tags: |
             ghcr.io/agentrust-io/ca2a-runtime:${{ steps.tag.outputs.tag }}
             ghcr.io/agentrust-io/ca2a-runtime:latest
+
+      - name: Install cosign
+        uses: sigstore/cosign-installer@v3
+
+      - name: Sign the image (keyless, by digest)
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+        run: cosign sign --yes ghcr.io/agentrust-io/ca2a-runtime@${DIGEST}
+
+      - name: Attest build provenance (SLSA)
+        uses: actions/attest-build-provenance@v2
+        with:
+          subject-name: ghcr.io/agentrust-io/ca2a-runtime
+          subject-digest: ${{ steps.build.outputs.digest }}
+          push-to-registry: true