Add Host API and fix kiosk performance

files/hostapi/README.md

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+# fleet-hostapi — workstation host-info agent
+
+A tiny **read-only, loopback-only** Go HTTP service that runs on the diskless
+workstation and reports facts about the machine the kiosk renders on. It is the
+OS-side implementation of the contract in [`../../HOST-API.md`](../../HOST-API.md)
+(authored alongside the kiosk-app SPA that consumes it).
+
+```
+GET http://localhost:9099/v1/host  ->  application/json   (os, hardware, net, kiosk, agent)
+GET http://localhost:9099/healthz  ->  200 ok
+```
+
+## Properties (and why)
+
+- **Loopback only.** Binds `127.0.0.1`; refuses to start on any routable address.
+  Host facts must never reach the boot LAN.
+- **Read only.** No endpoint mutates anything; it reads `/proc`, `/sys`,
+  `/etc/os-release`, and the build-time facts file.
+- **No per-host state baked in** (invariant #1). Host-specific fields (kernel,
+  hostname, IP, MAC, board, uptime) are read at **runtime**. The only baked facts
+  are image-generic — image version + weston/chromium versions — written to
+  `/etc/fleet-hostinfo.json` by the build provisioner.
+- **Stdlib only → reproducible build** (the verity hash is a security property).
+  Built `CGO_ENABLED=0 -trimpath -buildvcs=false -ldflags=-buildid=`; identical
+  bytes across builds with the same Go toolchain.
+- **CORS + Private Network Access.** The SPA is cross-origin and the fetch is a
+  Chromium private-network request, so responses carry
+  `Access-Control-Allow-Private-Network: true`. The matching browser-side
+  allowance is in `files/kiosk/chromium-kiosk-policy.json`
+  (`InsecurePrivateNetworkRequestsAllowedForUrls`, scoped to the kiosk origin).
+
+## Build / install
+
+Done by the `2b-hostapi` provisioner in `diskless.pkr.hcl`: installs the Go
+toolchain, builds the static binary to `/usr/local/bin/fleet-hostapi`, writes the
+facts file, installs + enables `fleet-hostapi.service`, and adds the binary to
+fapolicyd trust (2c-STIG-postfix). The toolchain is removed in 2d hygiene — only
+the static binary ships.
+
+Local build:
+
+```bash
+CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -trimpath -buildvcs=false \
+  -ldflags '-s -w -buildid=' -o fleet-hostapi .
+```
+
+## Config (env, set in the unit)
+
+| Var | Default | Notes |
+|---|---|---|
+| `FLEET_HOSTAPI_ADDR` | `127.0.0.1:9099` | must be loopback |
+| `FLEET_HOSTAPI_ALLOW_ORIGIN` | `*` | tighten to the kiosk origin in prod |
+| `FLEET_HOSTAPI_FACTS` | `/etc/fleet-hostinfo.json` | build-time facts |

files/hostapi/fleet-hostapi.service

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+[Unit]
+Description=Fleet workstation host-info API (loopback, read-only)
+Documentation=https://git.bitasylum.org/audiobuzz/diskless-workstation/HOST-API.md
+# Needs networking up only to read the primary IP/MAC; the listener is loopback.
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=exec
+ExecStart=/usr/local/bin/fleet-hostapi
+Environment=FLEET_HOSTAPI_ADDR=127.0.0.1:9099
+# Lab default: any origin may read (it's a loopback, read-only facts service on a
+# single-purpose kiosk). Tighten to the exact kiosk origin in production, e.g.
+#   Environment=FLEET_HOSTAPI_ALLOW_ORIGIN=http://boot.fleet.lab
+Environment=FLEET_HOSTAPI_ALLOW_ORIGIN=*
+Environment=FLEET_HOSTAPI_FACTS=/etc/fleet-hostinfo.json
+Restart=on-failure
+RestartSec=2
+
+# --- sandboxing (STIG-friendly; the agent only READS /proc, /sys, /etc) -------
+# Runs as a transient unprivileged user with no capabilities; everything it
+# reads is world-readable, so it needs no privilege at all.
+DynamicUser=yes
+CapabilityBoundingSet=
+AmbientCapabilities=
+NoNewPrivileges=yes
+ProtectSystem=strict
+ProtectHome=yes
+PrivateTmp=yes
+ProtectKernelTunables=yes
+ProtectKernelModules=yes
+ProtectKernelLogs=yes
+ProtectControlGroups=yes
+ProtectClock=yes
+ProtectHostname=yes
+ProtectProc=default
+RestrictNamespaces=yes
+RestrictRealtime=yes
+RestrictSUIDSGID=yes
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+SystemCallArchitectures=native
+SystemCallFilter=@system-service
+SystemCallFilter=~@privileged @resources
+RestrictAddressFamilies=AF_INET AF_INET6
+# Kernel-enforced loopback-only egress/ingress (belt + suspenders to the bind).
+IPAddressAllow=localhost
+IPAddressDeny=any
+UMask=0077
+
+[Install]
+WantedBy=multi-user.target

files/hostapi/go.mod

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+// fleet-hostapi: the workstation host-info agent (HOST-API.md contract).
+// Stdlib only — no external modules — so the build needs no network and is
+// trivially reproducible (a hard requirement: the rootfs/verity hash must be a
+// pure function of the inputs). Keep it dependency-free.
+module fleet-hostapi
+
+go 1.21

files/hostapi/main.go

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+// fleet-hostapi — read-only workstation host-info agent for the kiosk.
+//
+// Implements the contract in HOST-API.md: a tiny HTTP service on the diskless
+// workstation that reports facts about the machine the kiosk renders on. The
+// kiosk SPA (served from the boot server, a different origin) fetches
+//
+//	GET http://localhost:9099/v1/host  ->  application/json
+//
+// Design constraints (see CLAUDE.md invariants):
+//   - LOOPBACK ONLY. Never bind a routable address — this leaks host facts and
+//     must never reach the boot LAN.
+//   - READ ONLY. No endpoint mutates anything; the agent only reads /proc, /sys,
+//     /etc/os-release, and a build-time facts file.
+//   - NO PER-HOST STATE baked into the image. Everything host-specific (kernel,
+//     hostname, IP, MAC, board, uptime) is read at RUNTIME. The only baked facts
+//     are image-generic (image version + weston/chromium versions), written to a
+//     facts file by the build provisioner — same for every host of a release.
+//   - Stdlib only -> reproducible build (the verity hash is a security property).
+//
+// CORS + Private Network Access: the SPA is cross-origin AND the fetch is a
+// Chromium "private network" request, so every response (incl. the OPTIONS
+// preflight) carries Access-Control-Allow-Private-Network: true.
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"flag"
+	"log"
+	"math"
+	"net"
+	"net/http"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"syscall"
+	"time"
+)
+
+// agentVersion is overridable at build time via -ldflags "-X main.agentVersion=…".
+var agentVersion = "1.0.0"
+
+// ---- response shape (HOST-API.md) — all fields optional, omit what's unknown --
+
+type osInfo struct {
+	Name    string `json:"name,omitempty"`
+	Version string `json:"version,omitempty"`
+	Kernel  string `json:"kernel,omitempty"`
+	Image   string `json:"image,omitempty"`
+}
+
+type hwInfo struct {
+	CPU   string `json:"cpu,omitempty"`
+	Cores int    `json:"cores,omitempty"`
+	MemGB int    `json:"memGB,omitempty"`
+	GPU   string `json:"gpu,omitempty"`
+	Board string `json:"board,omitempty"`
+}
+
+type netInfo struct {
+	Hostname string `json:"hostname,omitempty"`
+	IP       string `json:"ip,omitempty"`
+	MAC      string `json:"mac,omitempty"`
+}
+
+type kioskInfo struct {
+	Uptime   string `json:"uptime,omitempty"`
+	Weston   string `json:"weston,omitempty"`
+	Chromium string `json:"chromium,omitempty"`
+}
+
+type agentInfo struct {
+	Version string `json:"version,omitempty"`
+}
+
+type hostResponse struct {
+	OS       osInfo    `json:"os"`
+	Hardware hwInfo    `json:"hardware"`
+	Net      netInfo   `json:"net"`
+	Kiosk    kioskInfo `json:"kiosk"`
+	Agent    agentInfo `json:"agent"`
+}
+
+// buildFacts is the image-generic, build-time facts file (written by the Packer
+// provisioner). Distinct from anything per-host.
+type buildFacts struct {
+	Image    string `json:"image"`
+	Weston   string `json:"weston"`
+	Chromium string `json:"chromium"`
+}
+
+func main() {
+	addr := flag.String("addr", env("FLEET_HOSTAPI_ADDR", "127.0.0.1:9099"), "listen address (MUST be loopback)")
+	origin := flag.String("allow-origin", env("FLEET_HOSTAPI_ALLOW_ORIGIN", "*"), "Access-Control-Allow-Origin value")
+	factsPath := flag.String("facts", env("FLEET_HOSTAPI_FACTS", "/etc/fleet-hostinfo.json"), "build-time facts file")
+	flag.Parse()
+
+	// Refuse to bind anything that isn't loopback — a hard guardrail against a
+	// misconfiguration exposing host facts on the boot LAN.
+	if host, _, err := net.SplitHostPort(*addr); err != nil || !isLoopback(host) {
+		log.Fatalf("refusing to listen on %q: bind address must be loopback (127.0.0.1/::1)", *addr)
+	}
+
+	facts := loadFacts(*factsPath)
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/v1/host", func(w http.ResponseWriter, r *http.Request) {
+		cors(w, *origin)
+		if r.Method == http.MethodOptions {
+			w.WriteHeader(http.StatusNoContent)
+			return
+		}
+		if r.Method != http.MethodGet {
+			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Header().Set("Cache-Control", "no-store")
+		enc := json.NewEncoder(w)
+		enc.SetIndent("", "  ")
+		_ = enc.Encode(collect(facts))
+	})
+	// Liveness for the unit / debugging (no host facts).
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/plain")
+		_, _ = w.Write([]byte("ok\n"))
+	})
+
+	srv := &http.Server{
+		Addr:              *addr,
+		Handler:           mux,
+		ReadHeaderTimeout: 5 * time.Second,
+		ReadTimeout:       10 * time.Second,
+		WriteTimeout:      10 * time.Second,
+		IdleTimeout:       60 * time.Second,
+	}
+	log.Printf("fleet-hostapi %s listening on %s (loopback, read-only)", agentVersion, *addr)
+	log.Fatal(srv.ListenAndServe())
+}
+
+func cors(w http.ResponseWriter, origin string) {
+	// Private Network Access: the kiosk page (boot-server origin, an insecure/
+	// public context) fetching localhost is a "private network" request — the
+	// preflight needs this header or Chromium blocks it. See HOST-API.md.
+	w.Header().Set("Access-Control-Allow-Origin", origin)
+	w.Header().Set("Access-Control-Allow-Private-Network", "true")
+	w.Header().Set("Access-Control-Allow-Methods", "GET, OPTIONS")
+	w.Header().Set("Vary", "Origin")
+}
+
+// collect gathers all host facts. Each source is best-effort: a failed read
+// leaves its field empty (the SPA renders "—" for missing fields).
+func collect(f buildFacts) hostResponse {
+	var resp hostResponse
+
+	// os
+	rel := parseKV("/etc/os-release")
+	resp.OS.Name = firstNonEmpty(rel["NAME"], rel["ID"])
+	resp.OS.Version = firstNonEmpty(rel["VERSION_ID"], rel["VERSION"])
+	resp.OS.Kernel = kernelRelease()
+	resp.OS.Image = f.Image
+
+	// hardware
+	resp.Hardware.CPU = cpuModel()
+	resp.Hardware.Cores = runtime.NumCPU()
+	resp.Hardware.MemGB = memGB()
+	resp.Hardware.GPU = gpuModel()
+	resp.Hardware.Board = boardModel()
+
+	// net
+	resp.Net.Hostname, _ = os.Hostname()
+	resp.Net.IP, resp.Net.MAC = primaryIfaceAddr()
+
+	// kiosk
+	resp.Kiosk.Uptime = uptimeHuman()
+	resp.Kiosk.Weston = f.Weston
+	resp.Kiosk.Chromium = f.Chromium
+
+	resp.Agent.Version = agentVersion
+	return resp
+}
+
+// ---- collectors -----------------------------------------------------------
+
+func kernelRelease() string {
+	var u syscall.Utsname
+	if err := syscall.Uname(&u); err != nil {
+		return ""
+	}
+	return charsToString(u.Release[:])
+}
+
+func cpuModel() string {
+	f, err := os.Open("/proc/cpuinfo")
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := sc.Text()
+		// x86: "model name". arm64: "Hardware"/"Processor" if present.
+		for _, key := range []string{"model name", "Hardware", "Processor"} {
+			if strings.HasPrefix(line, key) {
+				if _, v, ok := strings.Cut(line, ":"); ok {
+					return strings.TrimSpace(v)
+				}
+			}
+		}
+	}
+	_ = sc.Err() // best-effort read; empty result on any error
+	return ""
+}
+
+func memGB() int {
+	for _, line := range readLines("/proc/meminfo") {
+		if strings.HasPrefix(line, "MemTotal:") {
+			fields := strings.Fields(line) // MemTotal: <kB> kB
+			if len(fields) >= 2 {
+				if kb, err := strconv.ParseFloat(fields[1], 64); err == nil {
+					return int(math.Round(kb / 1024.0 / 1024.0))
+				}
+			}
+		}
+	}
+	return 0
+}
+
+// boardModel: vendor + product from DMI (world-readable sysfs — NOT product_serial,
+// which is root-only and per-host; we never read it).
+func boardModel() string {
+	vendor := strings.TrimSpace(readFile("/sys/class/dmi/id/sys_vendor"))
+	product := strings.TrimSpace(readFile("/sys/class/dmi/id/product_name"))
+	if vendor == "" && product == "" {
+		vendor = strings.TrimSpace(readFile("/sys/class/dmi/id/board_vendor"))
+		product = strings.TrimSpace(readFile("/sys/class/dmi/id/board_name"))
+	}
+	return strings.TrimSpace(strings.TrimSpace(vendor + " " + product))
+}
+
+// gpuModel: best-effort from the first DRM card's PCI ids. No PCI-ID database —
+// we map the few known vendors and otherwise emit the raw ids. Often empty on a
+// headless/virtio build VM; that's fine (optional field).
+func gpuModel() string {
+	for _, card := range []string{"card0", "card1"} {
+		base := "/sys/class/drm/" + card + "/device/"
+		vid := strings.TrimSpace(readFile(base + "vendor"))
+		did := strings.TrimSpace(readFile(base + "device"))
+		if vid == "" {
+			continue
+		}
+		name := map[string]string{
+			"0x8086": "Intel",
+			"0x1002": "AMD",
+			"0x10de": "NVIDIA",
+			"0x1af4": "Red Hat (virtio-gpu)",
+			"0x1234": "QEMU",
+			"0x1a03": "ASPEED",
+		}[strings.ToLower(vid)]
+		ids := strings.TrimPrefix(strings.ToLower(vid), "0x")
+		if did != "" {
+			ids += ":" + strings.TrimPrefix(strings.ToLower(did), "0x")
+		}
+		if name != "" {
+			return name + " [" + ids + "]"
+		}
+		return "[" + ids + "]"
+	}
+	return ""
+}
+
+// primaryIfaceAddr returns the preferred outbound IPv4 + the MAC of the
+// interface that owns it. Uses a UDP "connect" (no packet is sent) to let the
+// kernel pick the route's source address.
+func primaryIfaceAddr() (ip string, mac string) {
+	c, err := net.Dial("udp", "192.0.2.1:9") // TEST-NET-1, never reachable; no traffic on UDP connect
+	if err != nil {
+		return "", ""
+	}
+	defer c.Close()
+	la, ok := c.LocalAddr().(*net.UDPAddr)
+	if !ok || la.IP == nil {
+		return "", ""
+	}
+	ip = la.IP.String()
+	// find the interface carrying this IP -> its MAC
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return ip, ""
+	}
+	for _, ifc := range ifaces {
+		addrs, _ := ifc.Addrs()
+		for _, a := range addrs {
+			if n, ok := a.(*net.IPNet); ok && n.IP.Equal(la.IP) {
+				return ip, ifc.HardwareAddr.String()
+			}
+		}
+	}
+	return ip, ""
+}
+
+// uptimeHuman formats system uptime as "3h 12m". On a kiosk appliance the system
+// boots straight into the kiosk, so system uptime ≈ kiosk-session uptime —
+// reported here to avoid coupling to (and exec'ing) systemd for the unit time.
+func uptimeHuman() string {
+	var si syscall.Sysinfo_t
+	if err := syscall.Sysinfo(&si); err != nil {
+		return ""
+	}
+	d := time.Duration(si.Uptime) * time.Second
+	days := int(d.Hours()) / 24
+	hours := int(d.Hours()) % 24
+	mins := int(d.Minutes()) % 60
+	switch {
+	case days > 0:
+		return strconv.Itoa(days) + "d " + strconv.Itoa(hours) + "h " + strconv.Itoa(mins) + "m"
+	case hours > 0:
+		return strconv.Itoa(hours) + "h " + strconv.Itoa(mins) + "m"
+	default:
+		return strconv.Itoa(mins) + "m"
+	}
+}
+
+// ---- helpers --------------------------------------------------------------
+
+func loadFacts(path string) buildFacts {
+	var f buildFacts
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return f // file absent at runtime -> image/weston/chromium just omitted
+	}
+	_ = json.Unmarshal(b, &f)
+	return f
+}
+
+func env(k, def string) string {
+	if v := os.Getenv(k); v != "" {
+		return v
+	}
+	return def
+}
+
+func isLoopback(host string) bool {
+	if host == "localhost" {
+		return true
+	}
+	ip := net.ParseIP(host)
+	return ip != nil && ip.IsLoopback()
+}
+
+func parseKV(path string) map[string]string {
+	m := map[string]string{}
+	for _, line := range readLines(path) {
+		k, v, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+		m[strings.TrimSpace(k)] = strings.Trim(strings.TrimSpace(v), `"`)
+	}
+	return m
+}
+
+func readLines(path string) []string {
+	b := readFile(path)
+	if b == "" {
+		return nil
+	}
+	return strings.Split(strings.TrimRight(b, "\n"), "\n")
+}
+
+func readFile(path string) string {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return ""
+	}
+	return string(b)
+}
+
+func firstNonEmpty(vals ...string) string {
+	for _, v := range vals {
+		if v != "" {
+			return v
+		}
+	}
+	return ""
+}
+
+// charsToString converts a NUL-terminated Utsname field (int8 or uint8 across
+// arches) to a Go string.
+func charsToString(ca []int8) string {
+	b := make([]byte, 0, len(ca))
+	for _, c := range ca {
+		if c == 0 {
+			break
+		}
+		b = append(b, byte(c))
+	}
+	return string(b)
+}