attestor

Scorecard Attestor

What is scorecard-attestor?

scorecard-attestor is a tool that runs scorecard on a software source repo, and based on certain policies about those results, produces a Google Cloud binary authorization attestation.

scorecard-attestor helps users secure their software deployment systems by ensuring the code that they deploy passes certain criteria.

Building and using scorecard-attestor

scorecard-attestor can be built as a standalone binary from source using make build-attestor, or with Docker, using make build-attestor-docker. scorecard-attestor is intended to be used as part of a Google Cloud Build pipeline, and inherits environment variables based on build substitutions.

Unless there's an internal error, scorecard-attestor will always return a successful status code, but will only produce a binary authorization attestation if the policy check passes.

Configuring policies for scorecard-attestor

Policies for scorecard attestor can be passed through the CLI using the --policy flag. Examples of policies can be seen in attestor/policy/testdata.

Policies

• PreventBinaryArtifacts: Ensure that a repository is free from binary artifacts, which can link against the final repo artifact but isn't reviewable.
  • AllowedBinaryArtifacts: A list of binary artifacts, by repo path, to ignore. If not specified, no binary artifacts will be allowed
• PreventKnownVulnerabilities: Ensure that the project is free from security vulnerabilities/advisories, as registered in osv.dev.
• PreventUnpinnedDependencies: Ensure that a project's dependencies are pinned by hash. Dependency pinning makes builds more predictable, and prevents the consumption of malicious package versions from a compromised upstream.
  • AllowedUnpinnedDependencies: Ignore some dependencies, either by the filepath of the dependency management file (filepath, e.g. requirements.txt or package.json) or the dependency name (packagename, the specific package being ignored). If multiple filepaths/names, or a combination of filepaths and names are specified, all of them will be used. If not specified, no unpinned dependencies will be allowed.
• RequireCodeReviewed: Require that If CodeReviewRequirements is not specified, at least one reviewer will be required on all changesets. Scorecard-attestor inherits scorecard's default commit window (i.e. will only look at the last 30 commits to determine if they are reviewed or not).
  • CodeReviewRequirements.MinReviewers: The minimum number of distinct approvals required.
  • CodeReviewRequirements.RequiredApprovers: A set of approvers, any of whom must be found to have approved all changes. If a change is found without any approvals from this list, the check fails.

Policy schema

Policies follow the following schema:

---
type: "//rec"
optional:
    preventBinaryArtifacts: "//bool"
    allowedBinaryArtifacts:
        type: "//arr"
        contents: "//str" # Accepts glob-based filepaths as strings here
    ensureNoVulnerabilities: "//bool"
    ensureDependenciesPinned: "//bool"
    allowedUnpinnedDependencies:
        type: "//arr"
        contents:
            type: "//rec"
            optional:
                packagename: "//str"
                filepath: "//str"
                version: "//str"
    ensureCodeReviewed: "//bool"
    codeReviewRequirements:
        type: "//rec"
        optional:
            requiredApprovers:
                type: "//arr"
                contents: "//str"
            minReviewers: "//int"

Sample

Examples of how to use scorecard-attestor with binary authorization in your project can be found in these two repos:

• scorecard-binauthz-test-good
• scorecard-binauthz-test-bad

Sample code comes with:

• cloudbuild.yaml to build the application and run scorecard-attestor
• Terraform files to set up the binary authorization environment, including KMS and IAM.