Prototype commit

server/main.go

@@ -0,0 +1,213 @@
+package main
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/json"
+	"flag"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+type server struct {
+	staticDir    string
+	password     string
+	qrKey        string
+	secret       []byte
+	secure       bool
+	loginLimiter *rateLimiter
+}
+
+func main() {
+	addr := flag.String("addr", ":8181", "listen address")
+	staticDir := flag.String("static", "../web/build", "static asset directory")
+	insecure := flag.Bool("insecure", false, "drop Secure flag from cookie (dev only)")
+	strict := flag.Bool("strict", false, "production mode: refuse to start without DOCENT_COOKIE_SECRET and DOCENT_QR_KEY")
+	flag.Parse()
+
+	password := os.Getenv("DOCENT_PASSWORD")
+	if password == "" {
+		log.Fatal("DOCENT_PASSWORD must be set")
+	}
+	qrKey := os.Getenv("DOCENT_QR_KEY")
+	if qrKey == "" {
+		if *strict {
+			log.Fatal("DOCENT_QR_KEY must be set in -strict mode")
+		}
+		log.Println("warning: DOCENT_QR_KEY not set; QR-code auto-login disabled")
+	}
+
+	cookieSecret := os.Getenv("DOCENT_COOKIE_SECRET")
+	if *strict && cookieSecret == "" {
+		log.Fatal("DOCENT_COOKIE_SECRET must be set in -strict mode")
+	}
+	secret, err := loadOrGenSecret(cookieSecret)
+	if err != nil {
+		log.Fatalf("DOCENT_COOKIE_SECRET: %v", err)
+	}
+
+	abs, err := filepath.Abs(*staticDir)
+	if err != nil {
+		log.Fatalf("static dir: %v", err)
+	}
+	if _, err := os.Stat(abs); err != nil {
+		log.Printf("warning: static dir %s not found yet (build the SvelteKit app first)", abs)
+	}
+
+	s := &server{
+		staticDir:    abs,
+		password:     password,
+		qrKey:        qrKey,
+		secret:       secret,
+		secure:       !*insecure,
+		loginLimiter: newRateLimiter(8, time.Minute),
+	}
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("POST /api/login", s.handleLogin)
+	mux.HandleFunc("POST /api/key", s.handleKey)
+	mux.HandleFunc("POST /api/logout", s.handleLogout)
+	mux.HandleFunc("GET /api/me", s.handleMe)
+	mux.Handle("GET /audio/", s.requireAuth(http.HandlerFunc(s.serveStatic)))
+	mux.Handle("GET /images/", s.requireAuth(http.HandlerFunc(s.serveStatic)))
+	mux.HandleFunc("GET /", s.serveSPA)
+
+	log.Printf("docent listening on %s, serving %s", *addr, abs)
+	if err := http.ListenAndServe(*addr, mux); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func loadOrGenSecret(env string) ([]byte, error) {
+	if env != "" {
+		b, err := base64.StdEncoding.DecodeString(env)
+		if err != nil {
+			return nil, err
+		}
+		if len(b) < 32 {
+			return nil, errShortSecret
+		}
+		return b, nil
+	}
+	log.Println("warning: DOCENT_COOKIE_SECRET not set, generating ephemeral secret (sessions reset on restart)")
+	b := make([]byte, 32)
+	if _, err := rand.Read(b); err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
+var errShortSecret = &cookieError{"DOCENT_COOKIE_SECRET must decode to at least 32 bytes"}
+
+type cookieError struct{ msg string }
+
+func (e *cookieError) Error() string { return e.msg }
+
+func (s *server) handleLogin(w http.ResponseWriter, r *http.Request) {
+	if !s.loginLimiter.allow(clientIP(r)) {
+		w.Header().Set("Retry-After", "60")
+		http.Error(w, "too many attempts", http.StatusTooManyRequests)
+		return
+	}
+	var body struct {
+		Password string `json:"password"`
+	}
+	err := json.NewDecoder(r.Body).Decode(&body)
+	if err != nil || !constantTimeEqualString(body.Password, s.password) {
+		time.Sleep(250 * time.Millisecond)
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	s.setSessionCookie(w)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (s *server) handleKey(w http.ResponseWriter, r *http.Request) {
+	if !s.loginLimiter.allow(clientIP(r)) {
+		w.Header().Set("Retry-After", "60")
+		http.Error(w, "too many attempts", http.StatusTooManyRequests)
+		return
+	}
+	var body struct {
+		Key string `json:"key"`
+	}
+	err := json.NewDecoder(r.Body).Decode(&body)
+	// An empty qrKey means the QR auto-login is disabled — never accept any value.
+	if err != nil || s.qrKey == "" || !constantTimeEqualString(body.Key, s.qrKey) {
+		time.Sleep(250 * time.Millisecond)
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	s.setSessionCookie(w)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (s *server) handleLogout(w http.ResponseWriter, r *http.Request) {
+	s.clearSessionCookie(w)
+	w.WriteHeader(http.StatusNoContent)
+}
+
+func (s *server) handleMe(w http.ResponseWriter, r *http.Request) {
+	if !s.isAuthed(r) {
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+		return
+	}
+	w.Header().Set("Content-Type", "application/json")
+	w.Write([]byte(`{"ok":true}`))
+}
+
+func (s *server) requireAuth(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !s.isAuthed(r) {
+			http.Error(w, "unauthorized", http.StatusUnauthorized)
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
+// serveStatic serves files relative to staticDir, refusing path traversal.
+func (s *server) serveStatic(w http.ResponseWriter, r *http.Request) {
+	clean := filepath.Clean(r.URL.Path)
+	if strings.Contains(clean, "..") {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+	full := filepath.Join(s.staticDir, clean)
+	if !strings.HasPrefix(full, s.staticDir) {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+	info, err := os.Stat(full)
+	if err != nil || info.IsDir() {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+	http.ServeFile(w, r, full)
+}
+
+// serveSPA serves files from staticDir, falling back to index.html for client routes.
+func (s *server) serveSPA(w http.ResponseWriter, r *http.Request) {
+	clean := filepath.Clean(r.URL.Path)
+	if clean == "/" {
+		clean = "/index.html"
+	}
+	full := filepath.Join(s.staticDir, clean)
+	if !strings.HasPrefix(full, s.staticDir) {
+		http.Error(w, "not found", http.StatusNotFound)
+		return
+	}
+
+	if info, err := os.Stat(full); err == nil && !info.IsDir() {
+		http.ServeFile(w, r, full)
+		return
+	}
+
+	// Unknown path → SPA fallback.
+	w.Header().Set("Cache-Control", "no-cache")
+	http.ServeFile(w, r, filepath.Join(s.staticDir, "index.html"))
+}