Exploring Policy as Code Tooling

Policy as code turns governance into something you can test, review, and ship like any other part of the delivery workflow. Instead of relying on documents and manual checks, teams encode guardrails (security, compliance, cost, reliability) and enforce them automatically — during pull requests, at deploy time, and even at runtime.

In practice, it helps to think in layers. Some tools evaluate policies as decisions (often at runtime or during workflow “gates”), while others scan IaC for misconfigurations before anything is applied. The right choice depends on where you need enforcement: Kubernetes admission, Terraform/IaC pipelines, cloud org guardrails, or fine-grained app authorization.

In the full guide, we cover:

• Open Policy Agent (OPA) — An open-source, general-purpose policy engine (using Rego) that decouples policy decisions from services so you can enforce rules consistently across Kubernetes, APIs, CI/CD, and more.
• Gatekeeper (for Kubernetes) — A Kubernetes-native controller built on OPA that enforces admission policies via CRDs and Rego to prevent (and audit) non-compliant resources in clusters.
• Kyverno — A Kubernetes-native policy engine that defines policies in YAML and can validate, mutate, and generate resources to enforce security and best practices without learning a new language.
• Kubernetes ValidatingAdmissionPolicy (CEL) — A built-in Kubernetes admission feature that uses CEL expressions to do lightweight, in-API-server validation without external controllers.
• HashiCorp Sentinel (HCP Terraform) — A policy-as-code framework embedded in HashiCorp’s Terraform products that evaluates rules during plan/apply to enforce governance before changes land.
• Spacelift — An IaC automation platform with OPA/Rego-based policies applied at key workflow decision points to enforce governance across tools like Terraform/OpenTofu/Pulumi/CloudFormation/Kubernetes.
• Checkov — An open-source IaC static analysis scanner that detects misconfigurations early and supports custom policies (Python/YAML) across multiple IaC formats.
• Terrascan — An open-source IaC code analyzer that enforces policy packs (and custom rules) to find security/compliance issues across Terraform, Kubernetes, Helm, and more.
• Azure Policy (as-code workflows) — Microsoft’s native governance service where JSON policies can be versioned and deployed via CI/CD/GitOps to enforce and remediate compliance across Azure resources.
• AWS Service Control Policies (SCPs) — AWS Organizations guardrails expressed as JSON that set maximum permission boundaries across accounts/OUs, enabling centralized governance managed like code.
• Google Cloud Organization Policy — GCP’s org/folder/project constraint system for enforcing security/compliance/cost guardrails across resources, with Kubernetes Policy Controller extending it to clusters.
• AWS Cedar (via Amazon Verified Permissions) — A purpose-built AWS policy language for fine-grained, context-aware application authorization, designed to externalize and manage auth rules as code.

Read the full article for more details about the tools: https://spacelift.io/blog/policy-as-code-tools