feat(ci): attest SBOM and VEX to each platform manifest

.github/actions/cosign-sign-sbom/action.yml

@@ -43,6 +43,16 @@ runs:
   steps:
     - name: Install cosign
       uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
+      with:
+        # Pinned, not left to the installer's default. The verify side pins the
+        # same version and passes --new-bundle-format explicitly, so a Renovate
+        # bump of the installer SHA to a release defaulting to a different
+        # cosign major would leave signing and verification disagreeing about
+        # the on-registry layout, and the chart job would fail at its final
+        # verify with the artifact already pushed. Keep this equal to
+        # cosign-attest-multiplatform's cosign-version default; a release-policy
+        # test asserts it.
+        cosign-release: "v3.0.6"
 
     - name: Install Syft
       id: syft
@@ -95,7 +105,7 @@ runs:
         SUBJECT_DIGEST: ${{ inputs.subject-digest }}
       run: |
         set -euo pipefail
-        cosign sign --yes "${SUBJECT_NAME}@${SUBJECT_DIGEST}"
+        timeout --foreground 120s cosign sign --yes --new-bundle-format=true "${SUBJECT_NAME}@${SUBJECT_DIGEST}"
 
     - name: Attach CycloneDX SBOM attestation
       shell: bash
@@ -105,4 +115,4 @@ runs:
         SBOM_FILE: ${{ steps.sbom.outputs.sbom-file }}
       run: |
         set -euo pipefail
-        cosign attest --yes --predicate "${SBOM_FILE}" --type cyclonedx "${SUBJECT_NAME}@${SUBJECT_DIGEST}"
+        timeout --foreground 120s cosign attest --yes --new-bundle-format=true --predicate "${SBOM_FILE}" --type cyclonedx "${SUBJECT_NAME}@${SUBJECT_DIGEST}"

.github/actions/cosign-verify-release/action.yml

@@ -14,16 +14,55 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# WHY THE SUBJECTS ARE ASYMMETRIC
+#
+# For a multi-platform image this action verifies two different subjects in one
+# run, which reads like a mistake until you know what each piece of evidence
+# claims:
+#
+#   Signature        index digest     "this artifact is ours"
+#   SLSA provenance  index digest     "this artifact came out of that build"
+#   CycloneDX SBOM   platform digest  "this root filesystem contains these packages"
+#   OpenVEX          platform digest  "those packages are/are not exploitable here"
+#
+# A signature and a provenance statement are about the artifact as a whole, and
+# the index is what a user pulls, so they belong on the index. An SBOM and a VEX
+# document each describe exactly one root filesystem, and linux/amd64 and
+# linux/arm64 do not share one, so an SBOM on the index would describe neither
+# child truthfully. cosign-attest-multiplatform therefore publishes SBOM and VEX
+# against the platform manifests, and verification has to follow them there.
+#
+# The Helm chart takes the other path. It is a single OCI artifact with no
+# platform children, so amd64-digest and arm64-digest are left empty and every
+# check runs against the one subject, which is also what this action did before
+# the split. Nothing to split means nothing to follow.
+
 name: Cosign verify release subject
-description: Verify release signature, CycloneDX SBOM attestation, and SLSA v1 provenance.
+description: Verify release signature, CycloneDX SBOM and OpenVEX attestations, and SLSA v1 provenance.
 
 inputs:
   subject-name:
     description: OCI repository without tag or digest.
     required: true
   subject-digest:
-    description: OCI digest in sha256:<hex> form.
+    description: >-
+      OCI digest in sha256:<hex> form. For a multi-platform image this is the
+      index digest, which carries the signature and the SLSA provenance.
     required: true
+  amd64-digest:
+    description: >-
+      linux/amd64 platform manifest digest carrying the SBOM and VEX
+      attestations. Leave empty for a single-platform subject such as the Helm
+      chart, which keeps all evidence on subject-digest.
+    required: false
+    default: ""
+  arm64-digest:
+    description: >-
+      linux/arm64 platform manifest digest carrying the SBOM and VEX
+      attestations. Leave empty for a single-platform subject such as the Helm
+      chart, which keeps all evidence on subject-digest.
+    required: false
+    default: ""
   certificate-identity-regexp:
     description: Expected Fulcio certificate identity regexp.
     required: true
@@ -37,12 +76,21 @@ runs:
   steps:
     - name: Install cosign
       uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
+      with:
+        # Kept equal to the cosign-version default in
+        # .github/actions/cosign-attest-multiplatform. The signing side pins the
+        # binary so --new-bundle-format means what it says; verification reads
+        # the layout signing produced, so it has to be pinned to the same
+        # release rather than to whatever the installer currently defaults to.
+        cosign-release: "v3.0.6"
 
     - name: Verify release subject
       shell: bash
       env:
         SUBJECT_NAME: ${{ inputs.subject-name }}
         SUBJECT_DIGEST: ${{ inputs.subject-digest }}
+        AMD64_DIGEST: ${{ inputs.amd64-digest }}
+        ARM64_DIGEST: ${{ inputs.arm64-digest }}
         CERTIFICATE_IDENTITY_REGEXP: ${{ inputs.certificate-identity-regexp }}
         CERTIFICATE_OIDC_ISSUER: ${{ inputs.certificate-oidc-issuer }}
       run: |
@@ -57,18 +105,64 @@ runs:
           exit 1
         fi
 
+        # Half a pair is the dangerous case, not an obvious one. One empty
+        # digest would silently drop that architecture's SBOM and VEX checks
+        # while the job still reports success.
+        if [ -n "${AMD64_DIGEST}" ] && [ -z "${ARM64_DIGEST}" ]; then
+          echo "::error::amd64-digest was given without arm64-digest; pass both or neither"
+          exit 1
+        fi
+        if [ -z "${AMD64_DIGEST}" ] && [ -n "${ARM64_DIGEST}" ]; then
+          echo "::error::arm64-digest was given without amd64-digest; pass both or neither"
+          exit 1
+        fi
+
+        platform_digests=()
+        if [ -n "${AMD64_DIGEST}" ]; then
+          for digest in "${AMD64_DIGEST}" "${ARM64_DIGEST}"; do
+            if ! [[ "${digest}" =~ ^sha256:[a-f0-9]{64}$ ]]; then
+              echo "::error::platform digest must be in sha256:<64 hex> form, got '${digest}'"
+              exit 1
+            fi
+            platform_digests+=("${digest}")
+          done
+        fi
+
+        # --new-bundle-format is explicit on every verify-attestation because
+        # the signing side passes it explicitly too. Its default has moved
+        # between cosign releases, and a default flip on either side would look
+        # like a missing attestation rather than a format mismatch.
+        # Every cosign call is bounded, matching the attest action. These reach
+        # both the registry and Sigstore's TUF root, so a hung call would hold
+        # the release job open until the workflow's own timeout rather than
+        # failing it. Verification runs last, after the artifacts are already
+        # pushed, which is the worst point at which to hang.
+        verify_attestation() {
+          predicate_type="$1"
+          target="$2"
+          timeout --foreground 120s cosign verify-attestation \
+            --certificate-identity-regexp "${CERTIFICATE_IDENTITY_REGEXP}" \
+            --certificate-oidc-issuer "${CERTIFICATE_OIDC_ISSUER}" \
+            --new-bundle-format=true \
+            --type "${predicate_type}" \
+            "${target}"
+        }
+
         subject="${SUBJECT_NAME}@${SUBJECT_DIGEST}"
-        cosign verify \
-          --certificate-identity-regexp "${CERTIFICATE_IDENTITY_REGEXP}" \
-          --certificate-oidc-issuer "${CERTIFICATE_OIDC_ISSUER}" \
-          "${subject}"
-        cosign verify-attestation \
-          --certificate-identity-regexp "${CERTIFICATE_IDENTITY_REGEXP}" \
-          --certificate-oidc-issuer "${CERTIFICATE_OIDC_ISSUER}" \
-          --type cyclonedx \
-          "${subject}"
-        cosign verify-attestation \
+
+        timeout --foreground 120s cosign verify \
           --certificate-identity-regexp "${CERTIFICATE_IDENTITY_REGEXP}" \
           --certificate-oidc-issuer "${CERTIFICATE_OIDC_ISSUER}" \
-          --type https://slsa.dev/provenance/v1 \
+          --new-bundle-format=true \
           "${subject}"
+
+        if [ "${#platform_digests[@]}" -eq 0 ]; then
+          verify_attestation cyclonedx "${subject}"
+        else
+          for digest in "${platform_digests[@]}"; do
+            verify_attestation cyclonedx "${SUBJECT_NAME}@${digest}"
+            verify_attestation openvex "${SUBJECT_NAME}@${digest}"
+          done
+        fi
+
+        verify_attestation https://slsa.dev/provenance/v1 "${subject}"

.github/actions/setup-crane/action.yml

@@ -0,0 +1,63 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Setup crane
+description: Install the crane CLI as a checksum-pinned binary.
+
+runs:
+  using: composite
+  steps:
+    - name: Install crane
+      shell: bash
+      env:
+        # NVIDIA's enterprise restricts which GitHub Actions can be used, so
+        # crane is installed as a binary rather than through a third-party setup
+        # action. The SHA256 pins protect against tarball replacement on the
+        # upstream release, matching how setup-oras installs oras and how
+        # lint-ci installs actionlint and lychee.
+        #
+        # crane ships inside the google/go-containerregistry release tarball,
+        # so the version and the asset names are that project's, not crane's.
+        CRANE_VERSION: "0.22.1"
+        CRANE_SHA256_AMD64: 0ab7a1d6932a213aed964ce97666c3077fe691c8606413674a8b3e0b9ec4cda0
+        CRANE_SHA256_ARM64: 898c0cff975f898a33e8c4580bdafb0e7c02c7faa33374e946762f97c4ab7110
+      run: |
+        set -euo pipefail
+
+        # go-containerregistry names its amd64 asset Linux_x86_64, not
+        # Linux_amd64 the way oras does, so the uname value passes through
+        # unmapped on that arch.
+        case "$(uname -m)" in
+          x86_64) arch=x86_64; sha="${CRANE_SHA256_AMD64}" ;;
+          aarch64 | arm64) arch=arm64; sha="${CRANE_SHA256_ARM64}" ;;
+          *) echo "::error::unsupported architecture $(uname -m)"; exit 1 ;;
+        esac
+
+        tarball="${RUNNER_TEMP}/crane.tar.gz"
+        bindir="${RUNNER_TEMP}/crane-bin"
+
+        curl -sSfL --retry 3 --retry-delay 5 --retry-all-errors "https://github.com/google/go-containerregistry/releases/download/v${CRANE_VERSION}/go-containerregistry_Linux_${arch}.tar.gz" -o "${tarball}"
+        echo "${sha}  ${tarball}" | sha256sum -c -
+
+        # Onto PATH rather than into /usr/local/bin so the install needs no root.
+        # GITHUB_PATH applies to later steps, so this step calls it by full path.
+        # The tarball also carries gcrane, krane, a LICENSE and a README; naming
+        # the member keeps everything but crane out of the bindir.
+        mkdir -p "${bindir}"
+        tar -xzf "${tarball}" -C "${bindir}" crane
+        chmod +x "${bindir}/crane"
+        echo "${bindir}" >> "${GITHUB_PATH}"
+        "${bindir}/crane" version

.github/workflows/agent-ci.yaml

@@ -285,11 +285,12 @@ jobs:
           tag: ${{ needs.compute-metadata.outputs.git-sha }}
 
       - name: Sign GHCR agent image and attach SBOM
+        id: attest
         if: env.PUSH_TO_REGISTRY == 'true' && startsWith(github.ref, 'refs/tags/agent/')
-        uses: ./.github/actions/cosign-sign-sbom
+        uses: ./.github/actions/cosign-attest-multiplatform
         with:
           subject-name: ${{ steps.manifest.outputs.subject-name }}
-          subject-digest: ${{ steps.digest.outputs.digest }}
+          index-digest: ${{ steps.digest.outputs.digest }}
 
       - name: Attest GHCR agent provenance
         if: env.PUSH_TO_REGISTRY == 'true' && startsWith(github.ref, 'refs/tags/agent/')
@@ -305,6 +306,8 @@ jobs:
         with:
           subject-name: ${{ steps.manifest.outputs.subject-name }}
           subject-digest: ${{ steps.digest.outputs.digest }}
+          amd64-digest: ${{ steps.attest.outputs.amd64-digest }}
+          arm64-digest: ${{ steps.attest.outputs.arm64-digest }}
           certificate-identity-regexp: ^https://github.com/${{ github.repository }}/\.github/workflows/agent-ci\.yaml@refs/tags/agent/.*$
 
   operator-agent-tests:

.github/workflows/operator-ci.yaml

@@ -501,11 +501,12 @@ jobs:
           tag: ${{ needs.compute-metadata.outputs.git-sha }}
 
       - name: Sign GHCR operator image and attach SBOM
+        id: attest
         if: env.PUSH_TO_REGISTRY == 'true' && startsWith(github.ref, 'refs/tags/operator/')
-        uses: ./.github/actions/cosign-sign-sbom
+        uses: ./.github/actions/cosign-attest-multiplatform
         with:
           subject-name: ${{ steps.manifest.outputs.subject-name }}
-          subject-digest: ${{ steps.digest.outputs.digest }}
+          index-digest: ${{ steps.digest.outputs.digest }}
 
       - name: Attest GHCR operator provenance
         if: env.PUSH_TO_REGISTRY == 'true' && startsWith(github.ref, 'refs/tags/operator/')
@@ -521,6 +522,8 @@ jobs:
         with:
           subject-name: ${{ steps.manifest.outputs.subject-name }}
           subject-digest: ${{ steps.digest.outputs.digest }}
+          amd64-digest: ${{ steps.attest.outputs.amd64-digest }}
+          arm64-digest: ${{ steps.attest.outputs.arm64-digest }}
           certificate-identity-regexp: ^https://github.com/${{ github.repository }}/\.github/workflows/operator-ci\.yaml@refs/tags/operator/.*$
 
   # Single required check for branch protection. operator-ci, agent-ci,