cosign VS OPA (Open Policy Agent)

Cosign: In this context, Cosign from the Sigstore project offers a compelling solution. Its simplicity, registry compatibility, and effective link between images and their signatures provide a user-friendly and versatile approach. The integration of Fulcio for certificate management and Rekor for secure logging enhances Cosign's appeal, making it particularly suitable for modern development environments that prioritize security and agility.

sigstore is another suite of tools that focuses on attestation and provenance. Within the suite are two tools I heard mentioned a few times at KubeCon: Cosign and Rekor.

Since we can distribute Spin applications using popular registry services, we can also take advantage of ecosystem tools such as Sigstore and Cosign, which address the software supply chain issue by signing and verifying applications using Sigstore's new keyless signatures (using OIDC identity tokens from providers such as GitHub).

Use distroless images (which contain only application and its runtime dependencies, and don't include package managers/shells or any other programs you would expect to find in a standard Linux distribution). All distroless images are signed by cosign.

$ COSIGN_EXPERIMENTAL=1 cosign verify-blob --cert https://github.com/sigstore/cosign/releases/download/v1.13.1/cosign-linux-amd64-keyless.pem --signature https://github.com/sigstore/cosign/releases/download/v1.13.1/cosign-linux-amd64-keyless.sig https://github.com/sigstore/cosign/releases/download/v1.13.1/cosign-linux-amd64

Another thing to look for is, whether the image is signed using something like cosign (https://github.com/sigstore/cosign). This lets the publisher digitally sign the image, so you at least know that what's on the registry is what they intended to put there. Handy to avoid the risks of attackers squatting similar names and catching typos.

i’m late but surprised no one has mentioned cosign

name: Docker # This workflow uses actions that are not certified by GitHub. # They are provided by a third-party and are governed by # separate terms of service, privacy policy, and support # documentation. on: push: branches: [ "main" ] # Publish semver tags as releases. tags: [ 'v*.*.*' ] pull_request: branches: [ "main" ] paths: - src/MamisSolidarias.WebAPI.Campaigns/Dockerfile - .github/workflows/docker-publish.yml workflow_dispatch: env: # Use docker.io for Docker Hub if empty REGISTRY: ghcr.io IMAGE_NAME: mamis-solidarias/campaigns jobs: build: runs-on: ubuntu-latest permissions: contents: read packages: write # This is used to complete the identity challenge # with sigstore/fulcio when running outside of PRs. id-token: write steps: - name: Checkout repository uses: actions/checkout@v3 # Install the cosign tool except on PR # https://github.com/sigstore/cosign-installer - name: Install cosign if: github.event_name != 'pull_request' uses: sigstore/cosign-installer@main with: cosign-release: 'v1.13.1' - name: Set up QEMU uses: docker/setup-qemu-action@v2 with: platforms: 'arm64' # Workaround: https://github.com/docker/build-push-action/issues/461 - name: Setup Docker buildx uses: docker/setup-buildx-action@v2 # Login against a Docker registry except on PR # https://github.com/docker/login-action - name: Log into registry ${{ env.REGISTRY }} if: github.event_name != 'pull_request' uses: docker/login-action@v2 with: registry: ${{ env.REGISTRY }} username: ${{ github.actor }} password: ${{ secrets.GITHUB_TOKEN }} # Extract metadata (tags, labels) for Docker # https://github.com/docker/metadata-action - name: Extract Docker metadata id: meta uses: docker/metadata-action@v4 with: images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }} tags: | type=schedule type=ref,event=branch type=ref,event=pr type=semver,pattern={{version}} type=semver,pattern={{major}}.{{minor}} type=semver,pattern={{major}} type=sha # Build and push Docker image with Buildx (don't push on PR) # https://github.com/docker/build-push-action - name: Build and push Docker image id: build-and-push uses: docker/build-push-action@v3 with: context: . platforms: linux/amd64, linux/arm64 file: src/MamisSolidarias.WebAPI.Campaigns/Dockerfile push: ${{ github.event_name != 'pull_request' }} tags: ${{ steps.meta.outputs.tags }} labels: ${{ steps.meta.outputs.labels }} # Sign the resulting Docker image digest except on PRs. # This will only write to the public Rekor transparency log when the Docker # repository is public to avoid leaking data. If you would like to publish # transparency data even for private images, pass --force to cosign below. # https://github.com/sigstore/cosign - name: Sign the published Docker image if: ${{ github.event_name != 'pull_request' }} env: COSIGN_EXPERIMENTAL: "true" # This step uses the identity token to provision an ephemeral certificate # against the sigstore community Fulcio instance. run: echo "${{ steps.meta.outputs.tags }}" | xargs -I {} cosign sign {}@${{ steps.build-and-push.outputs.digest }}

After inspecting the layers i think you should start thinking about signing your images: https://github.com/sigstore/cosign/

cosign

How can we handle this? Are there any mechanisms to prevent or at least to some extent safeguard this kind of issues without falling back to a manual workflow? There is. One huge advantage of sticking to (de-facto) standards like Terraform is that first we are probably not the first ones to come up with this question and second there is a huge ecosystem around Terraform that might help us with such challenges. And for this specific scenario the solution is the Open Policy Agent. Let us take a closer look how the solution could look like.

A popular Policy-as-Code tool for Terraform is OPA, everyone's favorite versatile open-source policy engine that enforces security and compliance policies across your cloud-native stack, making it easier to manage and maintain consistent policy enforcement in complex, multi-service environments.

Harness Policy As Code uses Open Policy Agent (OPA) as the central service to store and enforce policies for the different entities and processes across the Harness platform. In this section, you will define a policy that will deny a pipeline execution if there is no approval step defined in a deployment stage.

OPA: While OPA is an open-source, general-purpose policy engine capable of enforcing unified and context-aware policies throughout the stack, it can also accept and output data in formats such as JSON, effectively functioning as a tool for generating or modifying configurations. Although it does not provide out-of-the-box schema definition support, it allows the integration of JsonSchema definitions.

In essence, container image signing involves adding a digital stamp to an image, affirming its authenticity. This digital assurance guarantees that the image is unchanged from creation to deployment. In this blog, I'll explain how to sign container images for Kubernetes using Cosign and the Open Policy Agent. I will also share a tutorial that demonstrates these concepts.

In this post we will explores two powerful solutions for addressing this issue: the Open Policy Language (OPA) and Google’s Zanzibar.

Rego is a declarative query language from the makers of the Open Policy Agent (OPA) framework. The Cloud Native Computing Foundation (CNCF) accepted OPA as an incubation-level hosted project in April 2019, and OPA graduated from incubating status in 2021.

Now there are more subdivided practice: * Policy as Code: Sentinel, OPA * Database as Code: bytebase * AppConfiguration as Code: KusionStack, Acorn * ...... (Welcome to add more)