Envoy Gateway HTTP/3 0-RTT Anti-Replay Defense for Mutation Endpoints

QUIC 0-RTT connection resumption permits clients to send early application data before the cryptographic handshake concludes, rendering requests vulnerable to network replay across distributed ingress zones. Envoy Gateway configurations and upstream services MUST enforce strict rejection or conditional deferral of non-idempotent HTTP methods (POST, PUT, PATCH, DELETE) arriving via 0-RTT Early-Data headers. Infrastructure and application layers must collaborate using RFC 8470 protocol semantics to guarantee that state-mutating transactions are never executed speculatively without forward secrecy.

--- description: Envoy Gateway HTTP/3 0-RTT Anti-Replay Defense for Mutation Endpoints - QUIC 0-RTT connection resumption permits clients to send early application data before the cryptographic handshake concludes, rendering requests vulnerable to network replay across distributed ingress zones. Envoy Gateway configurations and upstream services MUST enforce strict rejection or conditional deferral of non-idempotent HTTP methods (POST, PUT, PATCH, DELETE) arriving via 0-RTT Early-Data headers. Infrastructure and application layers must collaborate using RFC 8470 protocol semantics to guarantee that state-mutating transactions are never executed speculatively without forward secrecy. globs: infra/**/*.yaml, k8s/**/*.yaml, src/middleware/**/*.{ts,js,go}, src/ingress/**/*.{ts,js,go} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/envoy-gateway-http3-early-data-anti-replay" --- # Envoy Gateway HTTP/3 0-RTT Anti-Replay Defense for Mutation Endpoints > **Severity**: CRITICAL | **Category**: devops > **Anti-Pattern Warning**: Executing Non-Idempotent HTTP Mutations over Unvalidated QUIC 0-RTT Early Data ## System Constraints You are a Principal Infrastructure & Security Architect enforcing Envoy Gateway HTTP/3 0-RTT anti-replay safety invariants. Non-idempotent HTTP methods (POST, PUT, PATCH, DELETE) conveyed over QUIC 0-RTT early data packets expose distributed systems to replay attacks across multi-region clusters. You must mandate that Envoy Gateway EnvoyFilters/HTTPRoute configurations drop, reject, or force 425 (Too Early) retries on non-safe requests received prior to handshake completion, and ensure upstream microservices explicitly inspect the 'Early-Data' header. ## Strict Guidelines - Envoy Gateway MUST be configured to enforce `early_data_policy` or upstream EnvoyFilter transforms rejecting unsafe HTTP methods when early data is detected. - Upstream HTTP services MUST inspect the RFC 8470 `Early-Data` request header (`Early-Data: 1`) on all state-mutating requests and return HTTP status `425 Too Early` if processing non-idempotent logic. - Engineers MUST NOT permit client-side SDKs to pipeline mutating mutations (e.g., checkout, funds transfer, entity creation) in initial QUIC 0-RTT payloads. - Clients receiving an HTTP `425 Too Early` response MUST resend the identical HTTP request over the established connection only after the 1-RTT handshake has completed. - Distributed ingress topologies MUST enforce TLS Session Ticket encryption key rotation across all edge clusters within a tight window to prevent prolonged replay attack surfaces. ## Bad vs Good Implementations ### RFC 8470 Early-Data Guard Middleware in Ingress API Service #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The middleware executes state-mutating operations without validating whether the request arrived via 0-RTT early data (RFC 8470). Adversaries can capture and replay the early QUIC packet across distributed ingress instances, triggering duplicate mutations without cryptographic freshness. ```typescript import { Request, Response, NextFunction } from 'express'; export function processTransactionMiddleware(req: Request, res: Response, next: NextFunction): void { // Anti-Pattern: Blindly executing mutations without checking for QUIC 0-RTT early data // An eavesdropper can replay this packet across multiple edge regions, // causing duplicate financial transfers or state corruptions. if (req.method === 'POST') { executeTransfer(req.body) .then(() => res.status(200).json({ status: 'success' })) .catch((err) => next(err)); return; } next(); } async function executeTransfer(_payload: unknown): Promise<void> { /* processing logic */ } ``` #### Production Standard (Correct) > **Standard**: Adheres to RFC 8470: detects the `Early-Data` header populated by Envoy Gateway and immediately halts non-safe HTTP methods by returning HTTP 425 (Too Early). The client can safely retransmit the payload once forward secrecy is guaranteed by the finalized TLS/QUIC handshake. ```typescript import { Request, Response, NextFunction } from 'express'; const SAFE_METHODS = new Set(['GET', 'HEAD', 'OPTIONS']); export function earlyDataAntiReplayGuard(req: Request, res: Response, next: NextFunction): void { const isEarlyData = req.headers['early-data'] === '1'; // Production Invariant: Reject non-idempotent methods delivered in 0-RTT early data if (isEarlyData && !SAFE_METHODS.has(req.method)) { // Respond with 425 Too Early to demand 1-RTT handshake completion res.setHeader('Retry-After', '0'); res.status(425).json({ error: 'Too Early', message: 'State mutations cannot be processed in QUIC 0-RTT data. Re-send post-handshake.' }); return; } next(); } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Envoy Gateway HTTP/3 0-RTT Anti-Replay Defense for Mutation Endpoints

Envoy Gateway HTTP/3 0-RTT Anti-Replay Defense for Mutation Endpoints defines an industrial-grade behavioral standard for devops engineering. QUIC 0-RTT connection resumption permits clients to send early application data before the cryptographic handshake concludes, rendering requests vulnerable to network replay across distributed ingress zones. Envoy Gateway configurations and upstream services MUST enforce strict rejection or conditional deferral of non-idempotent HTTP methods (POST, PUT, PATCH, DELETE) arriving via 0-RTT Early-Data headers. Infrastructure and application layers must collaborate using RFC 8470 protocol semantics to guarantee that state-mutating transactions are never executed speculatively without forward secrecy. 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: Executing Non-Idempotent HTTP Mutations over Unvalidated QUIC 0-RTT Early Data 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	Executing Non-Idempotent HTTP Mutations over Unvalidated QUIC 0-RTT Early Data	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:

Envoy Gateway MUST be configured to enforce `early_data_policy` or upstream EnvoyFilter transforms rejecting unsafe HTTP methods when early data is detected.

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.