feat(build): attested sbom (#199)

asher · web-flow · commit c16f95bc1aff · 2026-06-23T10:54:53.000-07:00
* feat(build): attested sbom

* feat(build): pinned python for sbom build
diff --git a/.github/workflows/matrix.yml b/.github/workflows/matrix.yml
@@ -150,6 +150,8 @@ jobs:
       KERNEL_VERSION: "${{ matrix.merges.version }}"
       KERNEL_FLAVOR: "${{ matrix.merges.flavor }}"
       KERNEL_PRODUCES: "${{ join(matrix.merges.produces, ',') }}"
+      KERNEL_SRC_URL: "${{ matrix.merges.source }}"
+      FIRMWARE_URL: "${{ matrix.merges.firmware_url }}"
       DIGESTS_DIR: digests
     steps:
       - name: Harden the runner (Audit all outbound calls)
@@ -158,6 +160,12 @@ jobs:
           egress-policy: audit
       - name: checkout repository
         uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v4
+      - name: set up Python
+        uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        with:
+          python-version: '3.13'
+      - name: install python deps
+        run: pip3 install -r requirements.txt
       - name: install cosign
         uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
       - name: docker setup buildx
@@ -188,3 +196,23 @@ jobs:
           compression-level: 0
       - name: run merge script
         run: sh -x merge.sh
+      - name: generate and attest CycloneDX SBOM
+        env:
+          COSIGN_EXPERIMENTAL: "true"
+        run: |
+          set -euo pipefail
+          python3 hack/build/generate-sbom.py
+          jq -e '.bomFormat == "CycloneDX" and ((.components // []) | length > 0)' \
+            sbom.cdx.json >/dev/null \
+            || { echo "::error::kernel SBOM is empty or invalid"; exit 1; }
+          # Attest the SBOM to each published manifest (kernel + SDK)
+          attested=""
+          IFS=',' read -ra refs <<< "${KERNEL_PRODUCES}"
+          for ref in "${refs[@]}"; do
+            [ -n "${ref}" ] || continue
+            image="${ref%:*}"
+            case " ${attested} " in *" ${image} "*) continue ;; esac
+            attested="${attested} ${image}"
+            echo "attesting SBOM to ${ref}"
+            cosign attest --yes --type cyclonedx --predicate sbom.cdx.json "${ref}"
+          done
diff --git a/hack/build/generate-sbom.py b/hack/build/generate-sbom.py
@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+"""Generate a curated CycloneDX SBOM for a published kernel manifest.
+
+The kernel / kernel-SDK images are `FROM scratch` containing only compiled
+artifacts, so scanning them yields nothing, and scanning the debian build
+container yields hundreds of toolchain/base-OS packages that have no bearing on
+the kernel that ships. Instead we describe what actually defines the kernel:
+
+  - the upstream linux source version it was built from,
+  - the patches applied to that source (the authoritative, arch-union list from
+    patchlist.py), and
+  - for GPU flavors, the firmware / nvidia module versions baked in.
+
+All of this is architecture-independent -- the same source, patches, and module
+versions apply to every arch in the manifest -- so a single SBOM correctly
+describes the whole multi-arch image and stays correct as new arches (e.g.
+arm64) are added. There are deliberately NO per-arch / package filter rules.
+
+Reads from the environment (set by the merge job):
+  KERNEL_VERSION   e.g. "6.18.35" or "6.18.35+nvidia-610.43.02"
+  KERNEL_FLAVOR    e.g. "zone", "host", "zone-amdgpu", "zone-nvidiagpu"
+  KERNEL_SRC_URL   upstream linux source tarball URL
+  FIRMWARE_URL     linux-firmware tarball URL (only used for zone-amdgpu)
+
+Writes sbom.cdx.json (CycloneDX 1.6) in the current directory.
+
+This was created with Claude.
+"""
+import json
+import os
+import re
+import subprocess
+import sys
+
+
+def applied_patches(version, flavor):
+    """The patch files applied to this (version, flavor).
+
+    Delegates to patchlist.py so the SBOM lists exactly the patches the build
+    applies. patchlist.py matches constraints WITHOUT an arch argument, so this
+    is the union across architectures -- correct for a manifest-level SBOM and
+    forward-compatible with future arch-specific patches.
+    """
+    out = subprocess.run(
+        [sys.executable, "hack/build/patchlist.py", version, flavor],
+        check=True,
+        stdout=subprocess.PIPE,
+        text=True,
+    ).stdout
+    return [line.strip() for line in out.splitlines() if line.strip()]
+
+
+def firmware_version_from_url(url):
+    # .../linux-firmware-<ver>.tar.xz
+    match = re.search(r"linux-firmware-(.+?)\.tar\.", url or "")
+    return match.group(1) if match else None
+
+
+def main():
+    version = os.environ["KERNEL_VERSION"]
+    flavor = os.environ["KERNEL_FLAVOR"]
+    src_url = os.environ.get("KERNEL_SRC_URL", "")
+    firmware_url = os.environ.get("FIRMWARE_URL", "")
+
+    # Strip any "+nvidia-<ver>" local suffix to get the upstream kernel version.
+    kernel_version = version.split("+")[0]
+
+    kernel_ref = "pkg:generic/linux@%s" % kernel_version
+    linux_component = {
+        "bom-ref": kernel_ref,
+        "type": "operating-system",
+        "name": "linux",
+        "version": kernel_version,
+        "purl": kernel_ref,
+    }
+    if src_url:
+        linux_component["externalReferences"] = [
+            {"type": "distribution", "url": src_url}
+        ]
+
+    patches = applied_patches(version, flavor)
+    if patches:
+        linux_component["pedigree"] = {
+            "patches": [
+                {"type": "unofficial", "diff": {"url": patch}} for patch in patches
+            ]
+        }
+
+    components = [linux_component]
+    depends_on = [kernel_ref]
+
+    # GPU flavors bake in extra, separately-versioned artifacts.
+    if flavor == "zone-amdgpu":
+        fw_version = firmware_version_from_url(firmware_url)
+        if fw_version:
+            fw_ref = "pkg:generic/linux-firmware@%s" % fw_version
+            fw_component = {
+                "bom-ref": fw_ref,
+                "type": "firmware",
+                "name": "linux-firmware",
+                "version": fw_version,
+                "purl": fw_ref,
+            }
+            if firmware_url:
+                fw_component["externalReferences"] = [
+                    {"type": "distribution", "url": firmware_url}
+                ]
+            components.append(fw_component)
+            depends_on.append(fw_ref)
+
+    if flavor == "zone-nvidiagpu" and "+nvidia-" in version:
+        nv_version = version.split("+nvidia-", 1)[1]
+        nv_url = (
+            "https://github.com/NVIDIA/open-gpu-kernel-modules/archive/refs/tags/%s.tar.gz"
+            % nv_version
+        )
+        nv_ref = "pkg:github/NVIDIA/open-gpu-kernel-modules@%s" % nv_version
+        components.append(
+            {
+                "bom-ref": nv_ref,
+                "type": "library",
+                "name": "nvidia-open-gpu-kernel-modules",
+                "version": nv_version,
+                "purl": nv_ref,
+                "externalReferences": [{"type": "distribution", "url": nv_url}],
+            }
+        )
+        depends_on.append(nv_ref)
+
+    image_ref = "%s-kernel@%s" % (flavor, version)
+    document = {
+        "bomFormat": "CycloneDX",
+        "specVersion": "1.6",
+        "version": 1,
+        "metadata": {
+            "component": {
+                "bom-ref": image_ref,
+                "type": "container",
+                "name": "%s-kernel" % flavor,
+                "version": version,
+            },
+            "properties": [
+                {"name": "dev.edera.kernel.flavor", "value": flavor},
+            ],
+        },
+        "components": components,
+        "dependencies": [{"ref": image_ref, "dependsOn": depends_on}],
+    }
+
+    with open("sbom.cdx.json", "w") as out:
+        json.dump(document, out, indent=2)
+        out.write("\n")
+
+    # Human-readable summary for the build log.
+    print(
+        json.dumps(
+            {
+                "flavor": flavor,
+                "version": version,
+                "kernel": kernel_version,
+                "patches": len(patches),
+                "components": len(components),
+            },
+            indent=2,
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()
diff --git a/hack/build/matrix.py b/hack/build/matrix.py
@@ -487,6 +487,10 @@ def generate_merges(builds: list[dict[str, any]]) -> list[dict[str, any]]:
                 "tags": list(build["tags"]),
                 "produces": list(build["produces"]),
                 "archs": [build["arch"]],
+                # Carried for SBOM generation in the merge job; identical across
+                # archs for a given (version, flavor).
+                "source": build["source"],
+                "firmware_url": build["firmware_url"],
             }
         else:
             if build["arch"] not in merges[key]["archs"]:
