Cedar Policy Engine Formal Verification & Deterministic Policy Slicing Invariant

--- description: Cedar Policy Engine Formal Verification & Deterministic Policy Slicing Invariant - Enforces formal verification via SMT-backed validation and deterministic policy slicing on Cedar authorization policies before compilation or deployment to API gateways. Prevents privilege escalation paths and conflicting forbid/permit evaluation leaks across distributed microservice boundaries by mathematically proving policy soundness and non-interference. globs: src/authz/**/*.{ts,rs,cedar}, src/policies/**/*.{cedar,json}, src/services/gateway/**/*.{ts,rs}, src/lib/authorization/**/*.{ts,rs} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/cedar-formal-verification-deterministic-slicing" --- # Cedar Policy Engine Formal Verification & Deterministic Policy Slicing Invariant > **Severity**: CRITICAL | **Category**: security > **Anti-Pattern Warning**: Ad-hoc Gateway Ingestion of Unverified Cedar Policies with Ambiguous Scope and Non-Deterministic Slicing ## System Constraints You are a Principal Security Architect enforcing Cedar Policy Engine Formal Verification & Deterministic Slicing Invariants. Mandate that all Cedar policy sets must undergo strict JSON/Cedar schema validation, formal SMT verification for lack of unconstrained privilege escalations, and deterministic policy slicing before gateway deployment or in-memory compilation. ## Strict Guidelines - Engineers MUST ALWAYS validate all Cedar policies against an explicit, strictly typed Cedar Schema before compilation or gateway distribution. - Engineers MUST run formal equivalence and escape-path verification using Cedar Analysis tools (or SMT solvers like Z3) during policy compilation pipelines to prove the absence of unbounded permit escalations. - Engineers MUST NOT rely on runtime gateway fallback or partial evaluation defaults when slice compilation fails or produces ambiguous policy slices. - Services MUST extract a deterministic policy slice scoped solely to the target resource entity and principal context using deterministic boundary algorithms before policy evaluation. - Components NEVER evaluate dynamically constructed strings as Cedar policies without prior validation against schema invariants and dry-run static type checks. ## Bad vs Good Implementations ### Unvalidated Cedar Compilation vs SMT-Verified Sliced Engine Ingestion #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Parsing raw Cedar strings directly into the engine without static schema validation or automated SMT verification risks privilege escalation bugs (such as wildcard principal/action leaks) and evaluates an unsliced, potentially unbounded policy graph. ```typescript import { CedarEngine } from '@cedar-policy/cedar-wasm'; // ANTI-PATTERN: Dynamically evaluating unverified raw Cedar policies without schema // validation, missing formal checks for over-permissive escalation and deterministic slicing. export async function evaluateAccess(rawPolicies: string, request: { principal: string; action: string; resource: string }) { const engine = new CedarEngine(); // Raw policy string compiled without schema verification or escape analysis const policySet = engine.parsePolicySet(rawPolicies); // Runtime evaluation directly against whole policy set allows accidental permits or escalations const result = await engine.isAuthorized({ principal: request.principal, action: request.action, resource: request.resource, context: {} }, policySet); return result.decision === 'Allow'; } ``` #### Production Standard (Correct) > **Standard**: Validates the policy against an authoritative Cedar schema, performs formal verification to mathematically disprove unauthorized escalation paths, and applies deterministic slicing to isolate the minimal required policy set for predictable gateway evaluation. ```typescript import { CedarEngine, PolicySet, Schema } from '@cedar-policy/cedar-wasm'; import { verifyPolicySafety, extractDeterministicSlice } from './cedar-formal-verifier'; interface AuthorizationRequest { principal: string; action: string; resource: string; context: Record<string, unknown>; } // PRODUCTION INVARIANT: Schema-bound, formally verified, and deterministically sliced Cedar execution export async function evaluateAccessSecure( rawPolicies: string, schemaJson: object, request: AuthorizationRequest ): Promise<boolean> { const schema = Schema.fromJson(schemaJson); const engine = new CedarEngine(); const policySet = engine.parsePolicySet(rawPolicies); // 1. Static Typecheck against Cedar Schema const validationResult = engine.validate(policySet, schema); if (!validationResult.isValid) { throw new Error(`Cedar Schema Violation: ${JSON.stringify(validationResult.errors)}`); } // 2. Formal Verification: Prove no privilege escalation via SMT invariant analysis const isSound = await verifyPolicySafety(policySet, schema, { denyUnboundedWildcards: true, requireStrictBoundaries: true }); if (!isSound) { throw new Error('Formal Verification Failed: Potential privilege escalation path detected'); } // 3. Deterministic Slicing: Extract only the minimal policy subgraph relevant to (P, A, R) const slicedPolicies = extractDeterministicSlice(policySet, { principal: request.principal, action: request.action, resource: request.resource }); const result = await engine.isAuthorized(request, slicedPolicies); return result.decision === 'Allow'; } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Cedar Policy Engine Formal Verification & Deterministic Policy Slicing Invariant

Cedar Policy Engine Formal Verification & Deterministic Policy Slicing Invariant defines an industrial-grade behavioral standard for security engineering. Enforces formal verification via SMT-backed validation and deterministic policy slicing on Cedar authorization policies before compilation or deployment to API gateways. Prevents privilege escalation paths and conflicting forbid/permit evaluation leaks across distributed microservice boundaries by mathematically proving policy soundness and non-interference. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Ad-hoc Gateway Ingestion of Unverified Cedar Policies with Ambiguous Scope and Non-Deterministic Slicing Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Ad-hoc Gateway Ingestion of Unverified Cedar Policies with Ambiguous Scope and Non-Deterministic Slicing	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST ALWAYS validate all Cedar policies against an explicit, strictly typed Cedar Schema before compilation or gateway distribution.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.