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Merged
andrew merged 2 commits into from
Aug 10, 2026
+43 −0
Merged

Sign published container images #227

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Sign published container images
andrew Aug 4, 2026
7edec36
Attest per-platform SPDX SBOMs with cosign
andrew Aug 10, 2026
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43 changes: 43 additions & 0 deletions .github/workflows/publish.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ jobs:
permissions:
packages: write
contents: read
id-token: write
steps:
- name: Check out the repo
uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
Expand Down Expand Up @@ -45,11 +46,53 @@ jobs:
with:
images: ghcr.io/${{ github.repository }}

- uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2

- name: Build and push Docker image
id: build
uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a
with:
context: .
platforms: linux/amd64,linux/arm64
push: true
tags: ${{ steps.meta.outputs.tags }}
labels: ${{ steps.meta.outputs.labels }}
provenance: mode=max
sbom: true

- name: Sign image by digest
env:
DIGEST: ${{ steps.build.outputs.digest }}
IMAGE: ghcr.io/${{ github.repository }}
run: |
set -euo pipefail
[[ "$DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]
cosign sign --yes "${IMAGE}@${DIGEST}"

- name: Verify BuildKit attestations and extract SPDX predicates
env:
DIGEST: ${{ steps.build.outputs.digest }}
IMAGE: ghcr.io/${{ github.repository }}
run: |
set -euo pipefail
reference="${IMAGE}@${DIGEST}"
docker buildx imagetools inspect "$reference" --format '{{ json .Provenance }}' > provenance.json
docker buildx imagetools inspect "$reference" --format '{{ json .SBOM }}' > sbom.json
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andrew marked this conversation as resolved.

for platform in linux/amd64 linux/arm64; do
jq -e --arg p "$platform" '.[$p].SLSA | type == "object" and length > 0' \
provenance.json >/dev/null
jq -e --arg p "$platform" '.[$p].SPDX' sbom.json > "sbom-${platform//\//-}.spdx.json"
done

- name: Attest platform SBOMs by digest
env:
DIGEST: ${{ steps.build.outputs.digest }}
IMAGE: ghcr.io/${{ github.repository }}
run: |
set -euo pipefail
[[ "$DIGEST" =~ ^sha256:[0-9a-f]{64}$ ]]
reference="${IMAGE}@${DIGEST}"
for predicate in sbom-linux-amd64.spdx.json sbom-linux-arm64.spdx.json; do
cosign attest --yes --type spdxjson --predicate "$predicate" "$reference"
done