The previous scheme built ChaCha20-Poly1305 nonces from an internal
recv_seq counter that incremented once per decrypt() call. Under
in-order delivery recv_seq stayed in sync with the sender's send_seq,
but any out-of-order or lost packet caused them to diverge permanently —
every subsequent packet then used the wrong nonce and AEAD decryption
failed for the rest of the session.
Fix: parse the MediaHeader at the top of both encrypt() and decrypt()
and use header.seq as the nonce input. Both sides now derive the nonce
from the same wire field, surviving reordering by construction.
send_seq / recv_seq are kept as pure packet counters for the rekey
interval trigger; they no longer affect nonce derivation.
All tests updated to pass valid v2 MediaHeader bytes instead of raw
byte literals (the new code requires a parseable header for nonce
derivation). New test decrypt_survives_out_of_order_delivery encrypts
5 packets and delivers them out of order (indices 0,2,1,4,3); this
test would have failed under the old counter-based scheme.
Fixes audit finding C1 from AUDIT-2026-05-25.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Lets a client ask its registered relay "what IP:port do you see for
me?" over the existing TLS-authenticated signal channel, returning
the client's server-reflexive address as a SocketAddr. Replaces the
need for a classic STUN deployment and becomes the bootstrap step
for future P2P hole-punching: once both peers know their own reflex
addrs, they can advertise them in DirectCallOffer and attempt a
direct QUIC handshake to each other.
Wire protocol (wzp-proto):
- SignalMessage::Reflect — unit variant, client -> relay
- SignalMessage::ReflectResponse { observed_addr: String } — relay -> client
- JSON-serde, appended at end of enum: zero ordinal concerns,
backward compat with pre-Phase-1 relays by construction (older
relays log "unexpected message" and drop; newer clients time out
cleanly within 1s).
Relay handler (wzp-relay/src/main.rs, signal loop):
- New match arm next to Ping reuses the already-bound `addr` from
connection.remote_address() and replies with observed_addr as a
string. debug!-level log on success, warn!-level on send failure.
Client side (desktop/src-tauri/src/lib.rs):
- SignalState gains pending_reflect: Option<oneshot::Sender<SocketAddr>>.
- get_reflected_address Tauri command installs the oneshot before
sending Reflect and awaits it with a 1s timeout; cleans up on
every exit path (send failure, timeout, parse error).
- recv loop's new ReflectResponse arm fires the pending sender or
emits a debug log for unsolicited responses — never crashes the
loop on malformed input.
- Integrated into invoke_handler! alongside the other signal
commands.
UI (desktop/index.html + src/main.ts):
- New "Network" section in settings panel with a "Detect" button
that displays the reflected address or a categorized warning
("register first" / "relay does not support reflection" / error).
Tests (crates/wzp-relay/tests/reflect.rs — 3 new, all passing):
- reflect_happy_path: client on loopback gets back 127.0.0.1:<its own port>
- reflect_two_clients_distinct_ports: two concurrent clients see
their own distinct ports, proving per-connection remote_address
- reflect_old_relay_times_out: mock relay that ignores Reflect —
client times out between 1000-1200ms and does not hang
Also pre-existing test bit-rot unrelated to this PR — fixed so the
full workspace `cargo test` goes green:
- handshake_integration tests in wzp-client, wzp-relay and
featherchat_compat in wzp-crypto all missed the `alias` field
addition to CallOffer and the 3-arg form of perform_handshake
plus 4-tuple return of accept_handshake. Updated to the current
API surface.
Results:
cargo test --workspace --exclude wzp-android: 386 passed
cargo check --workspace: clean
cargo clippy: no new warnings in touched files
Verification excludes wzp-android because it's dead code on this
branch (Tauri mobile uses wzp-native instead) and can't link -llog
on macOS host — unchanged status quo.
PRD: .taskmaster/docs/prd_reflect_over_quic.txt
Tasks: 39-46 all completed
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
