A policy engine is a software component that lets an organization define, evaluate and audit access rules across its systems. It provides a central point of control for policy, so rules are managed once rather than in every application.
Policy engines evaluate each incoming request against a set of predefined policies, which may be written as code, stored in configuration files or held in an external database, and return an allow or deny decision. In a standard access control architecture, a policy engines takes on the roles of the policy decision point (PDP) and policy administration point (PAP), and in come products the policy information point (PIP) as well. The components below map those roles.
What are the components of a policy engine?
A typical policy engine had three components:
Centralized policy management: Rules are defined and maintained in one place rather than in every application, which simplifies managing them across large, distributed systems.
Flexibility: Policies can be updated as requirements change without modifying the applications that depend on them.
Consistency and auditability: Every request is evaluated against the same set of rules, which reduces the risk gaps from inconsistent or outdated policies, and every decision is logged, giving security teams a record to investigate them.
Implementing a policy engine takes three steps:
1. Define the policies. Base them on the organization's business rules and security requirements, and document them clearly so they're applied consistently.
2. Choose the engine. Weigh the complexity of your policies, the size of the system and the performance you need. Open Policy Agent (OPA) is a widely used general-purpose option.
3. Integrate it. Load the policies, connect the engine to the enforcements points that will call it, and test in audit-only mode before enforcing.
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