feat: harden HTTP server with rate limiting, request timeouts, and sanitized error messages

src/serve/auth.go

@@ -144,13 +144,13 @@ func (h *authHandler) callback(w http.ResponseWriter, r *http.Request) {
 		oauth2.SetAuthURLParam("code_verifier", pending.verifier),
 	)
 	if err != nil {
-		http.Error(w, "token exchange failed: "+err.Error(), http.StatusBadRequest)
+		http.Error(w, "token exchange failed", http.StatusBadRequest)
 		return
 	}
 
 	username, err := h.extractUsername(r.Context(), token)
 	if err != nil {
-		http.Error(w, "failed to identify user: "+err.Error(), http.StatusInternalServerError)
+		http.Error(w, "failed to identify user", http.StatusInternalServerError)
 		return
 	}
 
@@ -177,7 +177,7 @@ func (h *authHandler) deviceStart(w http.ResponseWriter, r *http.Request) {
 		oauth2.SetAuthURLParam("client_secret", h.cfg.ClientSecret),
 	)
 	if err != nil {
-		writeError(w, http.StatusBadGateway, "device authorization request failed: "+err.Error())
+		writeError(w, http.StatusBadGateway, "device authorization request failed")
 		return
 	}
 
@@ -196,7 +196,7 @@ func (h *authHandler) deviceStart(w http.ResponseWriter, r *http.Request) {
 		if err != nil {
 			h.mu.Lock()
 			if p := h.pendingDevice[loginID]; p != nil {
-				p.err = err.Error()
+				p.err = "device token exchange failed"
 			}
 			h.mu.Unlock()
 			return
@@ -206,7 +206,7 @@ func (h *authHandler) deviceStart(w http.ResponseWriter, r *http.Request) {
 		if err != nil {
 			h.mu.Lock()
 			if p := h.pendingDevice[loginID]; p != nil {
-				p.err = "failed to identify user: " + err.Error()
+				p.err = "failed to identify user"
 			}
 			h.mu.Unlock()
 			return

src/serve/ratelimit.go

@@ -0,0 +1,86 @@
+package serve
+
+import (
+	"net/http"
+	"sync"
+	"time"
+)
+
+type visitor struct {
+	tokens   float64
+	lastSeen time.Time
+}
+
+type rateLimiter struct {
+	mu       sync.Mutex
+	visitors map[string]*visitor
+	rate     float64 // tokens per second
+	burst    float64 // max tokens
+}
+
+func newRateLimiter(rate float64, burst int) *rateLimiter {
+	rl := &rateLimiter{
+		visitors: make(map[string]*visitor),
+		rate:     rate,
+		burst:    float64(burst),
+	}
+	go rl.cleanup()
+	return rl
+}
+
+func (rl *rateLimiter) allow(ip string) bool {
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
+	v, exists := rl.visitors[ip]
+	now := time.Now()
+	if !exists {
+		rl.visitors[ip] = &visitor{tokens: rl.burst - 1, lastSeen: now}
+		return true
+	}
+
+	elapsed := now.Sub(v.lastSeen).Seconds()
+	v.lastSeen = now
+	v.tokens += elapsed * rl.rate
+	if v.tokens > rl.burst {
+		v.tokens = rl.burst
+	}
+
+	if v.tokens < 1 {
+		return false
+	}
+	v.tokens--
+	return true
+}
+
+func (rl *rateLimiter) cleanup() {
+	for range time.Tick(time.Minute) {
+		rl.mu.Lock()
+		for ip, v := range rl.visitors {
+			if time.Since(v.lastSeen) > 5*time.Minute {
+				delete(rl.visitors, ip)
+			}
+		}
+		rl.mu.Unlock()
+	}
+}
+
+func clientIP(r *http.Request) string {
+	if ip := r.Header.Get("X-Forwarded-For"); ip != "" {
+		return ip
+	}
+	if ip := r.Header.Get("X-Real-IP"); ip != "" {
+		return ip
+	}
+	return r.RemoteAddr
+}
+
+func withRateLimit(rl *rateLimiter, next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !rl.allow(clientIP(r)) {
+			writeError(w, http.StatusTooManyRequests, "rate limit exceeded")
+			return
+		}
+		next.ServeHTTP(w, r)
+	})
+}

src/serve/server.go

@@ -24,6 +24,8 @@ func New(newSvc func(user string) (service.NodeService, error), oidcCfg *store.O
 	mux.HandleFunc("DELETE /nodes/{id}", s.deleteNode)
 	mux.HandleFunc("GET /users", s.listUsers)
 	mux.HandleFunc("POST /users", s.addUser)
+	rl := newRateLimiter(10, 30) // 10 req/s sustained, burst of 30
+
 	if oidcCfg != nil {
 		ah, err := newAuthHandler(*oidcCfg)
 		if err != nil {
@@ -33,9 +35,9 @@ func New(newSvc func(user string) (service.NodeService, error), oidcCfg *store.O
 		mux.HandleFunc("POST /auth/device/start", ah.deviceStart)
 		mux.HandleFunc("GET /auth/callback", ah.callback)
 		mux.HandleFunc("GET /auth/poll", ah.poll)
-		return withSessionAuth(ah, mux), nil
+		return withRateLimit(rl, withSessionAuth(ah, mux)), nil
 	}
-	return mux, nil
+	return withRateLimit(rl, mux), nil
 }
 
 type server struct {
@@ -53,7 +55,7 @@ func (s *server) svc(w http.ResponseWriter, r *http.Request) (service.NodeServic
 	}
 	svc, err := s.newSvc(user)
 	if err != nil {
-		writeError(w, http.StatusInternalServerError, err.Error())
+		writeError(w, http.StatusInternalServerError, "internal error")
 		return nil, false
 	}
 	return svc, true
@@ -96,7 +98,7 @@ func (s *server) listNodes(w http.ResponseWriter, r *http.Request) {
 	}
 	nodes, err := svc.List(filter)
 	if err != nil {
-		writeError(w, http.StatusInternalServerError, err.Error())
+		writeError(w, http.StatusInternalServerError, "internal error")
 		return
 	}
 	writeJSON(w, nodes)
@@ -171,7 +173,7 @@ func (s *server) listUsers(w http.ResponseWriter, r *http.Request) {
 	}
 	users, err := svc.ListUsers()
 	if err != nil {
-		writeError(w, http.StatusInternalServerError, err.Error())
+		writeError(w, http.StatusInternalServerError, "internal error")
 		return
 	}
 	writeJSON(w, users)