feat(host): §8a — require native pairing by default (serve --open to disable)

An open punktfunk/1 host any LAN device can trust-on-first-use and stream from is
insecure. The unified host now gates native sessions on pairing by DEFAULT: a client
must complete the SPAKE2 PIN ceremony (armed from the web console) before it's
admitted; paired devices persist. `serve --open` keeps the old TOFU behavior for
trusted single-user setups.

native_serve_opts now takes a NativeServe { port, require_pairing }; parse_serve
builds it with require_pairing = !--open. GameStream pairing (separate) is unchanged.
The require_pairing gate + ceremony are already covered by m3::pairing_ceremony_and_gate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/gamestream/mod.rs

@@ -145,17 +145,17 @@ impl AppState {
 }
 
 /// Run the host (blocks): mDNS, the nvhttp servers, and the management REST API.
-/// `native_port = Some(p)` makes this the **unified** host — it also runs the native punktfunk/1
-/// QUIC server on `p` in the same process, sharing one [`crate::native_pairing`] handle with the
-/// management API so the web console can arm pairing and show the PIN. `None` = GameStream only
+/// `native = Some(cfg)` makes this the **unified** host — it also runs the native punktfunk/1
+/// QUIC server on `cfg.port` in the same process, sharing one [`crate::native_pairing`] handle with
+/// the management API so the web console can arm pairing and show the PIN. `None` = GameStream only
 /// (the mgmt API's native endpoints report `enabled: false`).
-pub fn serve(mgmt: crate::mgmt::Options, native_port: Option<u16>) -> Result<()> {
+pub fn serve(mgmt: crate::mgmt::Options, native: Option<crate::m3::NativeServe>) -> Result<()> {
     let host = Host::detect()?;
     let identity = cert::ServerIdentity::load_or_create().context("host certificate")?;
     let state = Arc::new(AppState::new(host, identity));
     // The shared native-pairing handle exists only when we run the native host; it links the QUIC
     // ceremony and the management API.
-    let native = match native_port {
+    let np = match &native {
         Some(_) => Some(Arc::new(
             crate::native_pairing::NativePairing::load_with(None, None, false)
                 .context("native pairing store")?,
@@ -166,7 +166,8 @@ pub fn serve(mgmt: crate::mgmt::Options, native_port: Option<u16>) -> Result<()>
         hostname = %state.host.hostname,
         uniqueid = %state.host.uniqueid,
         ip = %state.host.local_ip,
-        native = native_port.is_some(),
+        native = native.is_some(),
+        require_pairing = native.as_ref().map(|n| n.require_pairing),
         "punktfunk host (GameStream P1.1: serverinfo + pairing + mDNS)"
     );
     let rt = tokio::runtime::Runtime::new().context("build tokio runtime")?;
@@ -176,13 +177,17 @@ pub fn serve(mgmt: crate::mgmt::Options, native_port: Option<u16>) -> Result<()>
         let _advert = mdns::advertise(&state.host).context("mDNS advertise")?;
         rtsp::spawn(state.clone()).context("start RTSP server")?;
         control::spawn(state.clone()).context("start ENet control server")?;
-        match (native_port, native) {
-            (Some(port), Some(np)) => {
-                tracing::info!(port, "unified host: also serving native punktfunk/1 (QUIC)");
+        match (native, np) {
+            (Some(cfg), Some(np)) => {
+                tracing::info!(
+                    port = cfg.port,
+                    require_pairing = cfg.require_pairing,
+                    "unified host: also serving native punktfunk/1 (QUIC)"
+                );
                 tokio::try_join!(
                     nvhttp::run(state.clone()),
                     crate::mgmt::run(state.clone(), mgmt, Some(np.clone())),
-                    crate::m3::serve(crate::m3::native_serve_opts(port), np),
+                    crate::m3::serve(crate::m3::native_serve_opts(&cfg), np),
                 )?;
             }
             _ => {

crates/punktfunk-host/src/m3.rs

@@ -115,17 +115,26 @@ fn fingerprint_hex(fp: &[u8; 32]) -> String {
 /// served one at a time (the virtual output + NVENC are single-tenant); a client that
 /// connects mid-session waits in the accept queue. A failed session logs and the loop
 /// keeps serving — only endpoint-level failures are fatal.
-/// Default options for the native host when the unified `serve --native` runs it in-process:
-/// real virtual capture, persistent (no session/duration cut), pairing armed on demand via the
-/// management API (the shared [`NativePairing`] starts disarmed).
-pub(crate) fn native_serve_opts(port: u16) -> M3Options {
+/// Config for the native (punktfunk/1) host when the unified `serve` runs it in-process.
+pub(crate) struct NativeServe {
+    pub port: u16,
+    /// Gate sessions on pairing. **Default on** — an open host any LAN device can stream from is
+    /// insecure; `serve --open` turns it off (trusted single-user setups). Pairing is armed on
+    /// demand from the web console (arm → PIN); paired devices persist.
+    pub require_pairing: bool,
+}
+
+/// Options for the native host when the unified `serve --native` runs it: real virtual capture,
+/// persistent (no session/duration cut), pairing armed on demand via the management API (the
+/// shared [`NativePairing`] starts disarmed).
+pub(crate) fn native_serve_opts(cfg: &NativeServe) -> M3Options {
     M3Options {
-        port,
+        port: cfg.port,
         source: M3Source::Virtual,
         seconds: 7 * 24 * 3600, // per-session cap; large enough not to cut a live stream
         frames: 0,
         max_sessions: 0,
-        require_pairing: false,
+        require_pairing: cfg.require_pairing,
         allow_pairing: false,
         pairing_pin: None,
         paired_store: None,

crates/punktfunk-host/src/main.rs

@@ -59,8 +59,8 @@ fn real_main() -> Result<()> {
         // GameStream host control plane (P1.1: mDNS + serverinfo) + management API, and (with
         // --native) the native punktfunk/1 host in the same process — the unified host.
         Some("serve") => {
-            let (mgmt_opts, native_port) = parse_serve(&args[1..])?;
-            gamestream::serve(mgmt_opts, native_port)
+            let (mgmt_opts, native) = parse_serve(&args[1..])?;
+            gamestream::serve(mgmt_opts, native)
         }
         // Print the management API's OpenAPI document (for client codegen).
         Some("openapi") => {
@@ -226,10 +226,12 @@ fn input_test() -> Result<()> {
 
 /// `serve` options: the management API (GameStream ports are protocol-fixed) + whether to also run
 /// the native punktfunk/1 host in-process (`--native`, the unified host). Returns the mgmt options
-/// and the native QUIC port (`None` = GameStream only).
-fn parse_serve(args: &[String]) -> Result<(mgmt::Options, Option<u16>)> {
+/// and the native host config (`None` = GameStream only). Native pairing is **required by default**
+/// (an open host any LAN device can stream from is insecure); `--open` turns it off.
+fn parse_serve(args: &[String]) -> Result<(mgmt::Options, Option<m3::NativeServe>)> {
     let mut opts = mgmt::Options::default();
     let mut native_port: Option<u16> = None;
+    let mut open = false;
     let mut i = 0;
     while i < args.len() {
         let arg = args[i].as_str();
@@ -265,6 +267,9 @@ fn parse_serve(args: &[String]) -> Result<(mgmt::Options, Option<u16>)> {
                         .map_err(|_| anyhow::anyhow!("bad --native-port (want a port number)"))?,
                 )
             }
+            // Disable mandatory native pairing — any device can connect (trusted single-user
+            // setups only). The default REQUIRES pairing.
+            "--open" => open = true,
             "-h" | "--help" => {
                 print_usage();
                 std::process::exit(0);
@@ -279,7 +284,11 @@ fn parse_serve(args: &[String]) -> Result<(mgmt::Options, Option<u16>)> {
             .ok()
             .filter(|t| !t.is_empty());
     }
-    Ok((opts, native_port))
+    let native = native_port.map(|port| m3::NativeServe {
+        port,
+        require_pairing: !open,
+    });
+    Ok((opts, native))
 }
 
 fn parse_m0(args: &[String]) -> Result<Options> {
@@ -398,6 +407,8 @@ SERVE OPTIONS:
     --native                     also run the native punktfunk/1 (QUIC) host in this process —
                                  the unified host; pairing is armed from the management API/console
     --native-port <PORT>         native QUIC port (default 9777; implies --native)
+    --open                       disable mandatory native pairing (default: pairing REQUIRED —
+                                 an open host any LAN device can stream from is insecure)
 
 M3-HOST OPTIONS:
     --port <N>                   QUIC listen port (default: 9777)