From f5e3e5e35622f7f410872962f8107220ac2b35f5 Mon Sep 17 00:00:00 2001
From: Alvar Penning <alvar.penning@icinga.com>
Date: Tue, 3 Nov 2026 16:07:40 +0100
Subject: [PATCH] sbom: Initial GitHub Actions For SBOM Generation

Create a CycloneDX SBOM via syft from all available information in the
repository and attach it as a build artifact.

If the workflow action is run on a Pull Request, do the same for the
base branch, compare the results, and add a PR warning if something
changed. Time will tell if this is useful or just annoying.

While on it, enable SBOM generation for docker/build-push-action.

These are all first steps to find out what might make sense.
---
 .github/workflows/container-image.yml |  1 +
 .github/workflows/sbom.yml            | 53 +++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 .github/workflows/sbom.yml

diff --git a/.github/workflows/container-image.yml b/.github/workflows/container-image.yml
index 2d5a89e..de44421 100644
--- a/.github/workflows/container-image.yml
+++ b/.github/workflows/container-image.yml
@@ -172,6 +172,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
           platforms: linux/amd64,linux/arm64
           push: ${{ github.event_name != 'pull_request' }}
+          sbom: true
           # The tags generated in the metadata step include tags for both Docker Hub and GHCR image names,
           # allowing the build and push action to build and push images to both registries.
           tags: ${{ steps.meta.outputs.tags }}
diff --git a/.github/workflows/sbom.yml b/.github/workflows/sbom.yml
new file mode 100644
index 0000000..494d967
--- /dev/null
+++ b/.github/workflows/sbom.yml
@@ -0,0 +1,53 @@
+on:
+  workflow_call:
+
+permissions:
+  contents: read
+
+jobs:
+  sbom:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          path: head
+          persist-credentials: false
+
+      - name: Generate SBOM
+        uses: anchore/sbom-action@66cbf4bc1f1c0d2edc94016e65bc221b6bb0ad6c # v0.24.3
+        with:
+          path: head
+          format: cyclonedx-json
+          output-file: sbom.cdx.json
+          artifact-name: sbom.cdx.json
+          upload-release-assets: false
+
+      - name: Checkout base
+        if: github.event_name == 'pull_request'
+        uses: actions/checkout@v7
+        with:
+          ref: ${{ github.event.pull_request.base.sha }}
+          path: base
+          persist-credentials: false
+
+      - name: Generate base SBOM
+        if: github.event_name == 'pull_request'
+        uses: anchore/sbom-action@66cbf4bc1f1c0d2edc94016e65bc221b6bb0ad6c # v0.24.3
+        with:
+          path: base
+          format: cyclonedx-json
+          output-file: sbom-base.cdx.json
+          upload-artifact: false
+          upload-release-assets: false
+
+      - name: Compare SBOMs
+        if: github.event_name == 'pull_request'
+        shell: bash
+        run: |
+          purls() { jq -r '.components[]?.purl // empty' "$1" | sort -u; }
+          purls sbom-base.cdx.json > "$RUNNER_TEMP/base.txt"
+          purls sbom.cdx.json > "$RUNNER_TEMP/head.txt"
+          comm -3 "$RUNNER_TEMP/base.txt" "$RUNNER_TEMP/head.txt" | sed \
+            -e 's/^\t/::warning title=SBOM changed::Added /;t' \
+            -e 's/^/::warning title=SBOM changed::Removed /'