148 lines
4.9 KiB
Markdown
148 lines
4.9 KiB
Markdown
---
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title: Verify Signed Kubernetes Artifacts
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content_type: task
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min-kubernetes-server-version: v1.26
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weight: 420
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---
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<!-- overview -->
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{{< feature-state state="beta" for_k8s_version="v1.26" >}}
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## {{% heading "prerequisites" %}}
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You will need to have the following tools installed:
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- `cosign` ([install guide](https://docs.sigstore.dev/cosign/installation/))
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- `curl` (often provided by your operating system)
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- `jq` ([download jq](https://jqlang.github.io/jq/download/))
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## Verifying binary signatures
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The Kubernetes release process signs all binary artifacts (tarballs, SPDX files,
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standalone binaries) by using cosign's keyless signing. To verify a particular
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binary, retrieve it together with its signature and certificate:
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```bash
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URL=https://dl.k8s.io/release/v{{< skew currentPatchVersion >}}/bin/linux/amd64
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BINARY=kubectl
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FILES=(
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"$BINARY"
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"$BINARY.sig"
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"$BINARY.cert"
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)
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for FILE in "${FILES[@]}"; do
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curl -sSfL --retry 3 --retry-delay 3 "$URL/$FILE" -o "$FILE"
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done
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```
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Then verify the blob by using `cosign verify-blob`:
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```shell
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cosign verify-blob "$BINARY" \
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--signature "$BINARY".sig \
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--certificate "$BINARY".cert \
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--certificate-identity krel-staging@k8s-releng-prod.iam.gserviceaccount.com \
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--certificate-oidc-issuer https://accounts.google.com
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```
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{{< note >}}
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Cosign 2.0 requires the `--certificate-identity` and `--certificate-oidc-issuer` options.
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To learn more about keyless signing, please refer to [Keyless Signatures](https://docs.sigstore.dev/cosign/keyless).
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Previous versions of Cosign required that you set `COSIGN_EXPERIMENTAL=1`.
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For additional information, plase refer to the [sigstore Blog](https://blog.sigstore.dev/cosign-2-0-released/)
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{{< /note >}}
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## Verifying image signatures
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For a complete list of images that are signed please refer
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to [Releases](/releases/download/).
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Pick one image from this list and verify its signature using
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the `cosign verify` command:
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```shell
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cosign verify registry.k8s.io/kube-apiserver-amd64:v{{< skew currentPatchVersion >}} \
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--certificate-identity krel-trust@k8s-releng-prod.iam.gserviceaccount.com \
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--certificate-oidc-issuer https://accounts.google.com \
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| jq .
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```
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### Verifying images for all control plane components
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To verify all signed control plane images for the latest stable version
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(v{{< skew currentPatchVersion >}}), please run the following commands:
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```shell
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curl -Ls "https://sbom.k8s.io/$(curl -Ls https://dl.k8s.io/release/stable.txt)/release" \
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| grep "SPDXID: SPDXRef-Package-registry.k8s.io" \
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| grep -v sha256 | cut -d- -f3- | sed 's/-/\//' | sed 's/-v1/:v1/' \
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| sort > images.txt
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input=images.txt
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while IFS= read -r image
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do
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cosign verify "$image" \
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--certificate-identity krel-trust@k8s-releng-prod.iam.gserviceaccount.com \
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--certificate-oidc-issuer https://accounts.google.com \
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| jq .
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done < "$input"
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```
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Once you have verified an image, you can specify the image by its digest in your Pod
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manifests as per this example:
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```console
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registry-url/image-name@sha256:45b23dee08af5e43a7fea6c4cf9c25ccf269ee113168c19722f87876677c5cb2
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```
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For more information, please refer
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to the [Image Pull Policy](/docs/concepts/containers/images/#image-pull-policy)
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section.
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## Verifying Image Signatures with Admission Controller
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For non-control plane images (for example
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[conformance image](https://github.com/kubernetes/kubernetes/blob/master/test/conformance/image/README.md)),
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signatures can also be verified at deploy time using
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[sigstore policy-controller](https://docs.sigstore.dev/policy-controller/overview)
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admission controller.
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Here are some helpful resources to get started with `policy-controller`:
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- [Installation](https://github.com/sigstore/helm-charts/tree/main/charts/policy-controller)
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- [Configuration Options](https://github.com/sigstore/policy-controller/tree/main/config)
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## Verify the Software Bill Of Materials
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You can verify the Kubernetes Software Bill of Materials (SBOM) by using the
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sigstore certificate and signature, or the corresponding SHA files:
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```shell
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# Retrieve the latest available Kubernetes release version
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VERSION=$(curl -Ls https://dl.k8s.io/release/stable.txt)
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# Verify the SHA512 sum
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curl -Ls "https://sbom.k8s.io/$VERSION/release" -o "$VERSION.spdx"
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echo "$(curl -Ls "https://sbom.k8s.io/$VERSION/release.sha512") $VERSION.spdx" | sha512sum --check
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# Verify the SHA256 sum
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echo "$(curl -Ls "https://sbom.k8s.io/$VERSION/release.sha256") $VERSION.spdx" | sha256sum --check
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# Retrieve sigstore signature and certificate
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curl -Ls "https://sbom.k8s.io/$VERSION/release.sig" -o "$VERSION.spdx.sig"
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curl -Ls "https://sbom.k8s.io/$VERSION/release.cert" -o "$VERSION.spdx.cert"
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# Verify the sigstore signature
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cosign verify-blob \
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--certificate "$VERSION.spdx.cert" \
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--signature "$VERSION.spdx.sig" \
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--certificate-identity krel-staging@k8s-releng-prod.iam.gserviceaccount.com \
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--certificate-oidc-issuer https://accounts.google.com \
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"$VERSION.spdx"
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```
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