ci: cache the Trivy database (#12)

.github/workflows/deploy-to-ghcr.yml

@@ -45,3 +45,6 @@ jobs:
         with:
           image-ref: ${{ env.TAG }}
           trivy-config: trivy.yml
+        env:
+          TRIVY_SKIP_DB_UPDATE: true
+          TRIVY_SKIP_JAVA_DB_UPDATE: true

.github/workflows/update-trivy-cache.yml

@@ -0,0 +1,38 @@
+# from https://github.com/aquasecurity/trivy-action?tab=readme-ov-file#updating-caches-in-the-default-branch
+name: Update Trivy Cache
+
+on:
+  schedule:
+    - cron: '0 0 * * *'  # Run daily at midnight UTC
+  workflow_dispatch:  # Allow manual triggering
+
+jobs:
+  update-trivy-db:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup oras
+        uses: oras-project/setup-oras@v1
+
+      - name: Get current date
+        id: date
+        run: echo "date=$(date +'%Y-%m-%d')" >> $GITHUB_OUTPUT
+
+      - name: Download and extract the vulnerability DB
+        run: |
+          mkdir -p $GITHUB_WORKSPACE/.cache/trivy/db
+          oras pull ghcr.io/aquasecurity/trivy-db:2
+          tar -xzf db.tar.gz -C $GITHUB_WORKSPACE/.cache/trivy/db
+          rm db.tar.gz
+
+      - name: Download and extract the Java DB
+        run: |
+          mkdir -p $GITHUB_WORKSPACE/.cache/trivy/java-db
+          oras pull ghcr.io/aquasecurity/trivy-java-db:1
+          tar -xzf javadb.tar.gz -C $GITHUB_WORKSPACE/.cache/trivy/java-db
+          rm javadb.tar.gz
+
+      - name: Cache DBs
+        uses: actions/cache/save@v4
+        with:
+          path: ${{ github.workspace }}/.cache/trivy
+          key: cache-trivy-${{ steps.date.outputs.date }}