QUIC HTTP/3 0-RTT Early Data Anti-Replay Verification in Go Chi

--- description: QUIC HTTP/3 0-RTT Early Data Anti-Replay Verification in Go Chi - Defends non-idempotent mutation routes in Go Chi HTTP/3 applications against network-level replay attacks via TLS 1.3 / QUIC 0-RTT early data. Enforces mandatory HTTP 425 (Too Early) rejections on unsafe methods or strict atomic distributed sliding-window replay caches keyed by TLS early data exporters and idempotency signatures. globs: **/*.go, cmd/**/*.go, internal/**/*.go, pkg/**/*.go alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/go-chi-http3-0rtt-anti-replay-guardrail" --- # QUIC HTTP/3 0-RTT Early Data Anti-Replay Verification in Go Chi > **Severity**: CRITICAL | **Category**: backend > **Anti-Pattern Warning**: Executing Non-Idempotent Mutations on Unchecked QUIC 0-RTT Early Data Handshakes ## System Constraints You are a Principal Security Architect specializing in transport-layer security and high-performance Go networking. Enforce strict anti-replay guardrails for Go Chi services serving HTTP/3 (QUIC) traffic. Mandate absolute rejection or distributed sliding-window replay tracking for TLS 1.3/QUIC 0-RTT Early Data on non-idempotent endpoints to prevent financial, transactional, and state-corrupting replay vulnerabilities. ## Strict Guidelines - Engineers MUST ALWAYS inspect HTTP/3 QUIC connection state or the RFC 8470 'Early-Data' header in Chi middleware before executing any mutation logic. - Engineers MUST NEVER permit unsafe HTTP methods (POST, PUT, PATCH, DELETE) to proceed on 0-RTT early data without an active sliding-window replay verification layer; return HTTP 425 StatusTooEarly immediately. - When 0-RTT processing is explicitly permitted on semi-idempotent endpoints, services MUST atomically claim the request token using a distributed cache (e.g., Redis SET NX EX) with a sliding window matching the server's maximum early data validity window. - Chi middleware MUST inject a 'Retry-After' header and set 'Cache-Control: no-cache' when returning HTTP 425 StatusTooEarly to signal conformant QUIC clients to replay immediately over the verified 1-RTT connection. - Components NEVER rely solely on application-level nonces without validating the TLS connection exporter material, as attackers can clone full transport packets identically in flight. ## Bad vs Good Implementations ### Vulnerable: Processing Chi Mutations Directly Over 0-RTT Early Data #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: When using HTTP/3 over QUIC, clients can send early application data (0-RTT) before the TLS handshake completes. If an attacker records the QUIC Initial UDP packet containing a POST request, they can replay it repeatedly. The Chi router executes the mutation every time without knowing the transport state was unauthenticated against replay. ```go package transport import ( "net/http" "github.com/go-chi/chi/v5" ) func RegisterRoutes(r chi.Router) { // VULNERABLE: Direct registration of state mutation without validating // whether the request arrived via QUIC 0-RTT Early Data. Attackers capturing // the 0-RTT Initial packet can replay this mutation multiple times. r.Post("/api/v1/orders/charge", func(w http.ResponseWriter, r *http.Request) { // Nonce checks here fail against raw transport-layer packet replay // if the application nonce handler does not bind to TLS connection epoch w.WriteHeader(http.StatusCreated) w.Write([]byte(`{"status":"charged"}`)) }) } ``` #### Production Standard (Correct) > **Standard**: The middleware intercepts RFC 8470 Early-Data markers. It immediately responds with HTTP 425 StatusTooEarly for unsafe methods lacking an idempotency key, forcing standard 1-RTT handshake completion. For keyed mutations, it leverages an atomic sliding-window lock in Redis, reliably quarantining replayed QUIC handshake attempts. ```go package transport import ( "context" "fmt" "net/http" "time" "github.com/go-chi/chi/v5" "github.com/redis/go-redis/v9" ) // AntiReplayMiddleware enforces RFC 8470 0-RTT early data protection. func AntiReplayMiddleware(rdb *redis.Client, window time.Duration) func(http.Handler) http.Handler { return func(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { isEarlyData := r.Header.Get("Early-Data") == "1" if !isEarlyData { next.ServeHTTP(w, r) return } // 1. Safe methods (GET, HEAD, OPTIONS) are permissible in early data switch r.Method { case http.MethodGet, http.MethodHead, http.MethodOptions: next.ServeHTTP(w, r) return } // 2. Fast-reject mutations unless explicit replay-protected idempotency key exists idempotencyKey := r.Header.Get("Idempotency-Key") if idempotencyKey == "" { w.Header().Set("Retry-After", "0") http.Error(w, "Too Early: 0-RTT replay unsafe on non-idempotent route", http.StatusTooEarly) return } // 3. Distributed Sliding-Window Replay Cache (Redis SET NX) ctx := r.Context() cacheKey := fmt.Sprintf("replay:0rtt:%s", idempotencyKey) success, err := rdb.SetNX(ctx, cacheKey, "claimed", window).Result() if err != nil || !success { // Key already seen in 0-RTT window or cache error -> Force 1-RTT retry w.Header().Set("Retry-After", "0") http.Error(w, "Too Early: Potential 0-RTT replay detected", http.StatusTooEarly) return } next.ServeHTTP(w, r) }) } } func RegisterRoutes(r chi.Router, rdb *redis.Client) { r.Use(AntiReplayMiddleware(rdb, 10*time.Second)) r.Post("/api/v1/orders/charge", func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(http.StatusCreated) w.Write([]byte(`{"status":"charged"}`)) }) } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: QUIC HTTP/3 0-RTT Early Data Anti-Replay Verification in Go Chi

QUIC HTTP/3 0-RTT Early Data Anti-Replay Verification in Go Chi defines an industrial-grade behavioral standard for backend engineering. Defends non-idempotent mutation routes in Go Chi HTTP/3 applications against network-level replay attacks via TLS 1.3 / QUIC 0-RTT early data. Enforces mandatory HTTP 425 (Too Early) rejections on unsafe methods or strict atomic distributed sliding-window replay caches keyed by TLS early data exporters and idempotency signatures. 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 Mutations on Unchecked QUIC 0-RTT Early Data Handshakes 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 Mutations on Unchecked QUIC 0-RTT Early Data Handshakes	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 inspect HTTP/3 QUIC connection state or the RFC 8470 'Early-Data' header in Chi middleware before executing any mutation logic.

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.