feat: optional 4-digit PIN asked in every new tab (not on reload), on-screen keypad for phones; set, change or remove it in the account; five misses sign out

internal/server/pin.go

@@ -0,0 +1,108 @@
+package server
+
+import (
+	"encoding/json"
+	"net/http"
+	"regexp"
+	"sync"
+)
+
+// The PIN: four digits an admin can set, asked for by the page in every new
+// browser tab (a reload of the same tab does not ask again). The server
+// checks it; five wrong ones in a row end the session.
+
+var pinRe = regexp.MustCompile(`^[0-9]{4}$`)
+
+// pinMisses counts wrong PINs per session.
+type pinMisses struct {
+	mu sync.Mutex
+	m  map[string]int
+}
+
+func (p *pinMisses) miss(sid string) int {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.m == nil {
+		p.m = map[string]int{}
+	}
+	p.m[sid]++
+	return p.m[sid]
+}
+
+func (p *pinMisses) clear(sid string) {
+	p.mu.Lock()
+	delete(p.m, sid)
+	p.mu.Unlock()
+}
+
+// GET /api/panel/pin - whether the admin has a PIN to ask for.
+func (s *Server) handlePinState(w http.ResponseWriter, r *http.Request) {
+	a := s.currentAdmin(r)
+	w.Header().Set("Cache-Control", "no-store")
+	writeJSON(w, map[string]any{"pin": s.db.AdminPin(a.ID) != ""})
+}
+
+// POST /api/panel/pin/check {"pin"} - the PIN typed in a new tab.
+func (s *Server) handlePinCheck(w http.ResponseWriter, r *http.Request) {
+	a := s.currentAdmin(r)
+	var in struct {
+		Pin string `json:"pin"`
+	}
+	_ = json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<10)).Decode(&in)
+	h := s.db.AdminPin(a.ID)
+	c, _ := r.Cookie(sessionCookie)
+	if h == "" || (pinRe.MatchString(in.Pin) && checkPassword(h, in.Pin)) {
+		s.pinMisses.clear(c.Value)
+		writeJSON(w, map[string]any{"ok": true})
+		return
+	}
+	if n := s.pinMisses.miss(c.Value); n >= 5 {
+		s.pinMisses.clear(c.Value)
+		s.clearSession(w, r)
+		s.db.Audit(a.ID, "", "pin_lockout")
+		writeJSON(w, map[string]any{"ok": false, "out": true, "error": "слишком много неверных попыток"})
+		return
+	} else {
+		writeJSON(w, map[string]any{"ok": false, "left": 5 - n, "error": "неверный PIN"})
+	}
+}
+
+// POST /api/panel/account/pin {"pin", "current"} - set or change the PIN;
+// with pin empty, remove it. A PIN in place is needed to change or drop it.
+func (s *Server) handlePinSet(w http.ResponseWriter, r *http.Request) {
+	a := s.currentAdmin(r)
+	var in struct {
+		Pin     string `json:"pin"`
+		Current string `json:"current"`
+	}
+	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 1<<10)).Decode(&in); err != nil {
+		writeJSON(w, map[string]any{"ok": false, "error": "плохой запрос"})
+		return
+	}
+	if h := s.db.AdminPin(a.ID); h != "" && !checkPassword(h, in.Current) {
+		writeJSON(w, map[string]any{"ok": false, "error": "текущий PIN не тот"})
+		return
+	}
+	hash := ""
+	if in.Pin != "" {
+		if !pinRe.MatchString(in.Pin) {
+			writeJSON(w, map[string]any{"ok": false, "error": "PIN - ровно 4 цифры"})
+			return
+		}
+		var err error
+		if hash, err = hashPassword(in.Pin); err != nil {
+			writeJSON(w, map[string]any{"ok": false, "error": err.Error()})
+			return
+		}
+	}
+	if err := s.db.SetAdminPin(a.ID, hash); err != nil {
+		writeJSON(w, map[string]any{"ok": false, "error": err.Error()})
+		return
+	}
+	action := "pin_set"
+	if hash == "" {
+		action = "pin_remove"
+	}
+	s.db.Audit(a.ID, "", action)
+	writeJSON(w, map[string]any{"ok": true})
+}