From 9c7b6efdcf14cd4213fc8ca0d0370bcd90d755c6 Mon Sep 17 00:00:00 2001
From: Andrew Nesbitt <andrewnez@gmail.com>
Date: Tue, 4 Aug 2026 09:01:19 +0100
Subject: [PATCH] Sign published container images

---
 .github/workflows/publish.yml | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index c08cfa6..7696d81 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -18,12 +18,15 @@ jobs:
     permissions:
       packages: write
       contents: read
+      id-token: write
     steps:
       - name: Check out the repo
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
         with:
           persist-credentials: false
 
+      - uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
+
       - name: Log in to the Container registry
         uses: docker/login-action@06fb636fac595d6fb4b28a5dfcb21a6f5091859c
         with:
@@ -37,10 +40,36 @@ jobs:
         with:
           images: ghcr.io/${{ github.repository }}
 
+      - uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
+
       - name: Build and push Docker image
+        id: build
         uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a
         with:
           context: .
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          provenance: mode=max
+          sbom: true
+
+      - name: Sign image by digest
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+          IMAGE: ghcr.io/${{ github.repository }}
+        run: |
+          set -euo pipefail
+          [[ "$DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]
+          cosign sign --yes "${IMAGE}@${DIGEST}"
+
+      - name: Verify remote provenance and SBOM attestations
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+          IMAGE: ghcr.io/${{ github.repository }}
+        run: |
+          set -euo pipefail
+          reference="${IMAGE}@${DIGEST}"
+          docker buildx imagetools inspect "$reference" --format '{{ json .Provenance }}' \
+            | jq -e 'type == "object" and length > 0' >/dev/null
+          docker buildx imagetools inspect "$reference" --format '{{ json .SBOM }}' \
+            | jq -e 'type == "object" and length > 0' >/dev/null