Add cosign of image (experimental)

.github/workflows/docker.yml

@@ -14,6 +14,8 @@ on:
 permissions:
   contents: read
   packages: write
+  # This is required for requesting the JWT (need for cosign)
+  id-token: write
 
 jobs:
   # This job builds the binaries and uploads it as github artifacts.
@@ -117,6 +119,9 @@ jobs:
       - run: |
           ls -al release*/
 
+      - name: Install cosign
+        uses: sigstore/cosign-installer@c3667d99424e7e6047999fb6246c0da843953c65 # v3.0.1
+
       - name: Build and push
         id: build-and-push
         # TODO: Remove pull_request before merging
@@ -133,6 +138,10 @@ jobs:
           cache-from: type=local,src=/tmp/.buildx-cache
           cache-to: type=local,dest=/tmp/.buildx-cache-new,mode=max
 
+      - name: Sign the published Docker image
+        # if: ${{ github.event_name != 'pull_request' }}
+        run: echo "${{ steps.meta.outputs.tags }}" | xargs -I {} cosign sign --yes {}@${{ steps.build-and-push.outputs.digest }}
+
       # Temp fix
       # https://github.com/docker/build-push-action/issues/252
       # https://github.com/moby/buildkit/issues/1896