Add encrypted UDP voice (OCB2-AES128) with TCP fallback

- Port of Mumble's CryptStateOCB2 (XEX* counter-measures, late/lost/replay
  handling, nonce resync), verified against Mumble's OCB2 test vectors
- UDP channel per connection in the main process, to the address the TLS
  connection reached; used only while the server answers UDP pings, falls back
  to the TCP tunnel automatically; "voice over TCP only" setting
- Voice statistics show the live transport
- Information dialog no longer infers the transport from ping counters
- Message box: no padding, input fills the bar; Edit HTML only in descriptions

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

electron/udp-voice.ts

@@ -0,0 +1,145 @@
+import dgram from 'node:dgram';
+import net from 'node:net';
+import { CryptState } from './ocb2.ts';
+import { writeVarint, readVarint } from '../src/core/voice-packet.ts';
+import { MumbleUDP } from '../src/core/mumble-udp-pb.js';
+import type { UdpChannel } from '../src/core/transport.ts';
+
+// Encrypted UDP voice channel to a Mumble server. Voice uses UDP only while the server
+// answers our UDP pings; until then (and if it stops) the client keeps using the TCP tunnel.
+
+export interface UdpCallbacks {
+  onVoice(plain: Uint8Array): void;
+  onState(ok: boolean, rtt: number): void;
+  onResync(): void;          // too many decrypt failures: ask the server for a fresh nonce
+}
+
+const PING_MS = 2000;
+const DEAD_MS = 8000;
+
+export class UdpVoice {
+  readonly crypt = new CryptState();
+  ok = false;
+  rtt = 0;
+  private sock: dgram.Socket;
+  private protobuf = true;
+  private pingTimer: ReturnType<typeof setInterval> | null = null;
+  private lastPong = 0;
+  private failures = 0;
+  private lastResync = 0;
+  private closed = false;
+  private host: string;
+  private port: number;
+  private cb: UdpCallbacks;
+
+  constructor(host: string, port: number, cb: UdpCallbacks) {
+    this.host = host;
+    this.port = port;
+    this.cb = cb;
+    this.sock = dgram.createSocket(net.isIPv6(host) ? 'udp6' : 'udp4');
+    this.sock.on('message', msg => this.receive(msg));
+    this.sock.on('error', () => this.setOk(false));
+  }
+
+  setup(key: Uint8Array, clientNonce: Uint8Array, serverNonce: Uint8Array, protobuf: boolean): void {
+    this.crypt.setKey(key, clientNonce, serverNonce);
+    this.protobuf = protobuf;
+    if (!this.pingTimer) {
+      this.ping();
+      this.pingTimer = setInterval(() => this.ping(), PING_MS);
+    }
+  }
+
+  setServerNonce(nonce: Uint8Array): void {
+    this.crypt.setDecryptIv(nonce);
+    this.failures = 0;
+  }
+
+  send(plain: Uint8Array): void {
+    if (this.closed || !this.crypt.valid) return;
+    const packet = this.crypt.encrypt(plain);
+    this.sock.send(packet, this.port, this.host);
+  }
+
+  private ping(): void {
+    if (this.lastPong && Date.now() - this.lastPong > DEAD_MS) this.setOk(false);
+    const ts = Date.now();
+    if (this.protobuf) {
+      const body: Uint8Array = MumbleUDP.Ping.encode(MumbleUDP.Ping.fromObject({ timestamp: ts })).finish();
+      const out = new Uint8Array(body.length + 1);
+      out[0] = 1;
+      out.set(body, 1);
+      this.send(out);
+    } else {
+      const out: number[] = [1 << 5];
+      writeVarint(out, ts);
+      this.send(new Uint8Array(out));
+    }
+  }
+
+  private receive(msg: Buffer): void {
+    const plain = this.crypt.decrypt(msg);
+    if (!plain) {
+      // Repeated failures mean the nonces drifted apart; ask for a resync now and then
+      if (++this.failures > 8 && Date.now() - this.lastResync > 5000) {
+        this.lastResync = Date.now();
+        this.failures = 0;
+        this.cb.onResync();
+      }
+      return;
+    }
+    this.failures = 0;
+    const pingTs = this.pingTimestamp(plain);
+    if (pingTs != null) {
+      this.lastPong = Date.now();
+      this.rtt = Math.max(0, Date.now() - pingTs);
+      this.setOk(true);
+      return;
+    }
+    this.cb.onVoice(new Uint8Array(plain));
+  }
+
+  private pingTimestamp(p: Buffer): number | null {
+    try {
+      if (p[0] === 1 && this.protobuf) return Number(MumbleUDP.Ping.toObject(MumbleUDP.Ping.decode(p.subarray(1)), { longs: Number }).timestamp);
+      if (p[0] >> 5 === 1 && !this.protobuf) return readVarint(p, 1)[0];
+    } catch { /* not a ping */ }
+    return null;
+  }
+
+  private setOk(ok: boolean): void {
+    if (ok === this.ok) {
+      if (ok) this.cb.onState(true, this.rtt);
+      return;
+    }
+    this.ok = ok;
+    this.cb.onState(ok, this.rtt);
+  }
+
+  close(): void {
+    this.closed = true;
+    if (this.pingTimer) clearInterval(this.pingTimer);
+    try { this.sock.close(); } catch { /* closed */ }
+  }
+}
+
+// UdpVoice behind the client's UdpChannel interface (used directly in Node, bridged over IPC in the app)
+export function udpChannel(host: string, port: number): UdpChannel & { close(): void; voice: UdpVoice } {
+  const ch: UdpChannel & { close(): void; voice: UdpVoice } = {
+    onVoice: null, onState: null, onResync: null,
+    setup: (k, c, s, p) => voice.setup(k, c, s, p),
+    setServerNonce: n => voice.setServerNonce(n),
+    clientNonce: () => Promise.resolve(voice.crypt.valid ? new Uint8Array(voice.crypt.encryptIv) : null),
+    send: p => voice.send(p),
+    close: () => voice.close(),
+    voice: null as unknown as UdpVoice
+  };
+  const voice = new UdpVoice(host, port, {
+    onVoice: p => ch.onVoice?.(p),
+    onState: (ok, rtt) => ch.onState?.(ok, rtt),
+    onResync: () => ch.onResync?.()
+  });
+  ch.voice = voice;
+  return ch;
+}
+