Policy as Code

Policies are written to define the desired state of a system, not the step-by-step procedure to achieve it. The PaC engine handles the logic of how to enforce the rule.

• Focus on the 'what' (e.g., 'all storage buckets must be private'), not the 'how'.
• The engine continuously evaluates the current state against the declared policy.
• This model is the foundation of reconciliation loops in Kubernetes and other declarative systems.

Storing policies in a Git repository treats them with the same rigor as application code. This enables collaboration, audit trails, and rollbacks.

• Every policy change is a pull request, subject to peer review and automated testing.
• The Git history provides an immutable audit log of who changed a rule, when, and why.
• This practice is a core tenet of GitOps, where the repository is the single source of truth.

PaC enables unit and integration testing for compliance rules before they affect production systems. This shifts security left in the development lifecycle.

• Write tests to confirm a policy correctly blocks a non-compliant resource and allows a compliant one.
• Integrate policy checks into CI/CD pipelines to prevent misconfigurations from being deployed.
• Tools like Open Policy Agent (OPA) provide frameworks for writing and executing these policy tests.

A PaC engine decouples policy decisions from application logic, providing a single, centralized service for authorization and compliance across a heterogeneous stack.

• Applications query the engine via API at decision time (e.g., 'Can this user create a resource in this region?').
• This architecture eliminates siloed, hard-coded authorization logic in each microservice.
• The engine can enforce rules across diverse layers: Kubernetes admission control, API gateways, and Infrastructure as Code (IaC) provisioning.

Policies are expressed in domain-specific, machine-readable languages designed for readability and expressiveness, not general-purpose programming.

• Rego, the language for Open Policy Agent, uses a declarative, logic-based syntax inspired by Datalog.
• Sentinel, by HashiCorp, uses a policy-as-code framework with a familiar imperative-style syntax.
• These languages abstract away the complexity of the underlying enforcement mechanisms, making policies accessible to compliance and security teams.

PaC is not a one-time check; it continuously monitors the live environment for configuration drift and can automatically remediate violations.

• The engine constantly evaluates the actual state of infrastructure against the declared policy in the Git repository.
• If a manual change creates a violation, the system can trigger an alert or automatically revert the change.
• This closed-loop automation ensures that the system remains in a known, compliant state, a key concept in self-healing networks and drift remediation.

A continuous control mechanism that compares the observed state against the desired state and automatically takes action to eliminate any difference. In Policy as Code, this loop is critical for drift remediation. If a policy mandates that all storage buckets must be private, the reconciliation loop continuously monitors for violations and can automatically revert a bucket made public by an unauthorized change, ensuring continuous compliance rather than point-in-time auditing.