Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard

--- description: Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard - Enforces strict isolation of QUIC and TLS 1.3 0-RTT early data frames to idempotent read operations across Hyper HTTP/3 edge pipelines. Neutralizes replay vulnerabilities during connection migrations and 0-RTT handshakes by mandating HTTP 425 (Too Early) rejections or handshake deferral on all state-mutating requests. globs: src/**/*.{rs,ts,go} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/hyper-http3-0rtt-anti-replay-mitigation-standard" --- # Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard > **Severity**: CRITICAL | **Category**: backend > **Anti-Pattern Warning**: Executing state-mutating or non-idempotent operations across 0-RTT early data without 1-RTT cryptographic completion ## System Constraints You are a Principal Backend and Systems Security Architect enforcing the Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard. You must ensure that 0-RTT early data in QUIC and TLS 1.3 handshakes is strictly quarantined to safe, idempotent request pipelines. You must require early data rejection with HTTP 425 (Too Early) or forced 1-RTT deferral whenever state mutations, credential evaluations, or unsafe methods are detected. ## Strict Guidelines - Engineers MUST ALWAYS reject or delay state-mutating requests (POST, PUT, DELETE, PATCH) received via 0-RTT early data by returning HTTP status code 425 (Too Early) or awaiting the 1-RTT handshake completion. - Engineers MUST NOT permit execution of database writes, financial transactions, or authentication credential evaluations within 0-RTT early data frames. - Code SHOULD inspect the QUIC connection state and transport extensions at the Hyper transport layer to tag requests processed from early data before delegating to application routers. - Services MUST ensure that even read operations (GET, HEAD, OPTIONS) permitted over 0-RTT early data are strictly side-effect free and cannot be leveraged for replay amplification. - Components NEVER assume network uniqueness or forward secrecy for payloads transmitted prior to full TLS 1.3/QUIC handshake validation. ## Bad vs Good Implementations ### Hyper HTTP/3 0-RTT Early Data Pipeline Mitigation (Rust) #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The handler processes a state-mutating POST request directly from 0-RTT early data without checking if the TLS 1.3 handshake has completed, allowing network replays to execute duplicate transactions. ```rust use hyper::{Body, Request, Response, StatusCode, Method}; pub async fn handle_request(req: Request<Body>, is_early_data: bool) -> Result<Response<Body>, hyper::Error> { // VULNERABLE: Directly executing state-mutating logic on 0-RTT early data. // An adversary can capture and replay this QUIC 0-RTT frame to duplicate payments. if req.method() == Method::POST && req.uri().path() == "/api/v1/payments" { execute_payment_transaction(&req).await; return Ok(Response::builder() .status(StatusCode::OK) .body(Body::from("Payment Processed")) .unwrap()); } Ok(Response::new(Body::from("OK"))) } async fn execute_payment_transaction(_req: &Request<Body>) {} ``` #### Production Standard (Correct) > **Standard**: The middleware intercepts early data frames, validates method idempotency per RFC 8470, and immediately terminates non-idempotent requests with HTTP 425 (Too Early), preventing replay attacks before state-mutating business logic can execute. ```rust use hyper::{Body, Request, Response, StatusCode, Method, header::HeaderValue}; const STATUS_TOO_EARLY: StatusCode = StatusCode::from_u16(425).unwrap(); pub async fn handle_request(req: Request<Body>, is_early_data: bool) -> Result<Response<Body>, hyper::Error> { // SECURE: Enforce RFC 8470 anti-replay boundary on 0-RTT streams. if is_early_data { let is_idempotent = matches!(*req.method(), Method::GET | Method::HEAD | Method::OPTIONS); if !is_idempotent { // Reject mutating request; client must resend over confirmed 1-RTT connection return Ok(Response::builder() .status(STATUS_TOO_EARLY) .header("Early-Data", HeaderValue::from_static("1")) .header("Retry-After", HeaderValue::from_static("0")) .body(Body::from("Mutating actions prohibited in 0-RTT early data")) .unwrap()); } } if req.method() == Method::POST && req.uri().path() == "/api/v1/payments" { execute_payment_transaction(&req).await; return Ok(Response::builder() .status(StatusCode::OK) .body(Body::from("Payment Processed")) .unwrap()); } Ok(Response::new(Body::from("OK"))) } async fn execute_payment_transaction(_req: &Request<Body>) {} ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard

Hyper HTTP/3 0-RTT Anti-Replay Mitigation Standard defines an industrial-grade behavioral standard for backend engineering. Enforces strict isolation of QUIC and TLS 1.3 0-RTT early data frames to idempotent read operations across Hyper HTTP/3 edge pipelines. Neutralizes replay vulnerabilities during connection migrations and 0-RTT handshakes by mandating HTTP 425 (Too Early) rejections or handshake deferral on all state-mutating requests. 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 state-mutating or non-idempotent operations across 0-RTT early data without 1-RTT cryptographic completion 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 state-mutating or non-idempotent operations across 0-RTT early data without 1-RTT cryptographic completion	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 reject or delay state-mutating requests (POST, PUT, DELETE, PATCH) received via 0-RTT early data by returning HTTP status code 425 (Too Early) or awaiting the 1-RTT handshake completion.

Engineers MUST ALWAYS reject or delay state-mutating requests (POST, PUT, DELETE, PATCH) received via 0-RTT early data by returning HTTP status code 425 (Too Early) or awaiting the 1-RTT handshake completion.

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.