.github/workflows/docker-publish.yml

@@ -4,9 +4,14 @@ on:
   release:
     types: [published]
   push:
+    branches: [ "main" ]
+    # Publish semver tags as releases.
     tags: [ 'v*.*.*' ]
+  pull_request:
+    branches: [ "main" ]
 
 env:
+  # Use github.repository as <account>/<repo>
   IMAGE_NAME: ${{ github.repository }}
   REGISTRY: ghcr.io
 
@@ -16,14 +21,28 @@ jobs:
     permissions:
       contents: read
       packages: write
+      # This is used to complete the identity challenge
+      # with sigstore/fulcio when running outside of PRs.
+      id-token: write
 
     steps:
       - name: Checkout repository
         uses: actions/checkout@v4
 
+      # Install the cosign tool except on PR
+      # https://github.com/sigstore/cosign-installer
+      - name: Install cosign
+        if: github.event_name != 'pull_request'
+        uses: sigstore/cosign-installer@v3.3.0
+        with:
+          cosign-release: 'v2.1.1'
+
+      # Set up BuildKit Docker container builder to enable modern features
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
+      # Login against a Docker registry
+      # https://github.com/docker/login-action
       - name: Log into registry ${{ env.REGISTRY }}
         if: github.event_name != 'pull_request'
         uses: docker/login-action@v3
@@ -32,6 +51,8 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      # Extract metadata (tags, labels) for Docker
+      # https://github.com/docker/metadata-action
       - name: Extract Docker metadata
         id: meta
         uses: docker/metadata-action@v5
@@ -44,6 +65,8 @@ jobs:
             type=semver,pattern={{major}}.{{minor}}
             type=raw,value=latest,enable={{is_default_branch}}
 
+      # Build and push Docker image with Buildx
+      # https://github.com/docker/build-push-action
       - name: Build and push Docker image
         id: build-and-push
         uses: docker/build-push-action@v5
@@ -54,3 +77,16 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
+
+      # Sign the resulting Docker image digest except on PRs.
+      # This will only write to the public Rekor transparency log when the Docker
+      # repository is public to avoid leaking data.  If you would like to publish
+      # transparency data even for private images, pass --force to cosign below.
+      # https://github.com/sigstore/cosign
+      - name: Sign the published Docker image
+        if: github.event_name != 'pull_request'
+        env:
+          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
+          TAGS: ${{ steps.meta.outputs.tags }}
+          DIGEST: ${{ steps.build-and-push.outputs.digest }}
+        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}

README.md

@@ -19,7 +19,7 @@ services:
     image: ghcr.io/vleeuwenmenno/auto-upnp:latest
     network_mode: host
     environment:
-      PORTS: [{"port": 80, "protocol": "tcp"}, {"port": 443, "protocol": "tcp"}]
+      - PORTS=[{"port": 80, "protocol": "tcp"}, {"port": 443, "protocol": "tcp"}]
 ```
 
 ### Environment Variables

docker-compose.yml

@@ -1,17 +1,14 @@
 name: auto-upnp
 services:
   upnp:
-    image: ghcr.io/vleeuwenmenno/auto-upnp:latest
-    # build:
-    #   context: .
-    #   dockerfile: Dockerfile
+    # image: ghcr.io/vleeuwenmenno/auto-upnp:latest
+    build:
+      context: .
+      dockerfile: Dockerfile
     restart: unless-stopped
     network_mode: host
     environment:
       UPNP_DURATION: 86400  # 24 hours in seconds
-      # One-liner
-      # PORTS: [{"port": 80, "protocol": "tcp"}, {"port": 443, "protocol": "tcp"}]
-      # Or multi-line
       PORTS: | 
         [
           {"port": 7777, "protocol": "udp"},