fixa aumento no serial do soa

cmd/pdns-admin/main.go

@@ -1,9 +1,11 @@
 package main
 
 import (
+	"context"
 	"log"
 	"net/http"
 	"os"
+	"time"
 
 	"pdns_admin/internal/auth"
 	"pdns_admin/internal/config"
@@ -20,6 +22,12 @@ func main() {
 	}
 
 	pdnsClient := pdns.NewClient(cfg.PDNSAPIURL, cfg.PDNSAPIKey, cfg.PDNSServerID, http.DefaultClient)
+	metadataCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+	if err := pdnsClient.EnsureAllZonesSOAEditAPI(metadataCtx); err != nil {
+		logger.Fatalf("failed to ensure SOA-EDIT-API setting: %v", err)
+	}
+
 	var authenticator server.Authenticator
 	if !cfg.Auth.Disabled {
 		authenticator, err = auth.NewLDAPAuthenticator(auth.LDAPConfig{

internal/pdns/client.go

@@ -13,6 +13,8 @@ import (
 	"time"
 )
 
+const soaEditAPIIncrease = "INCREASE"
+
 type HTTPClient interface {
 	Do(*http.Request) (*http.Response, error)
 }
@@ -26,25 +28,20 @@ type Client struct {
 
 type Server struct {
 	ID         string `json:"id"`
-	Type       string `json:"type"`
 	DaemonType string `json:"daemon_type"`
 	Version    string `json:"version"`
-	URL        string `json:"url"`
-	ConfigURL  string `json:"config_url"`
-	ZonesURL   string `json:"zones_url"`
 }
 
 type Zone struct {
-	ID           string   `json:"id,omitempty"`
+	ID          string   `json:"id,omitempty"`
-	Name         string   `json:"name"`
+	Name        string   `json:"name,omitempty"`
-	Type         string   `json:"type,omitempty"`
+	Type        string   `json:"type,omitempty"`
-	Kind         string   `json:"kind,omitempty"`
+	Kind        string   `json:"kind,omitempty"`
-	Serial       uint64   `json:"serial,omitempty"`
+	Serial      uint64   `json:"serial,omitempty"`
-	EditedSerial uint64   `json:"edited_serial,omitempty"`
+	SOAEditAPI  string   `json:"soa_edit_api,omitempty"`
-	SOAEditAPI   string   `json:"soa_edit_api,omitempty"`
+	Nameservers []string `json:"nameservers,omitempty"`
-	Nameservers  []string `json:"nameservers,omitempty"`
+	Masters     []string `json:"masters,omitempty"`
-	Masters      []string `json:"masters,omitempty"`
+	RRSets      []RRSet  `json:"rrsets,omitempty"`
-	RRSets       []RRSet  `json:"rrsets,omitempty"`
 }
 
 type RRSet struct {
@@ -100,9 +97,50 @@ func (c *Client) ListZones(ctx context.Context) ([]Zone, error) {
 }
 
 func (c *Client) CreateZone(ctx context.Context, zone Zone) (Zone, error) {
+	zone.SOAEditAPI = soaEditAPIIncrease
 	var created Zone
-	err := c.do(ctx, http.MethodPost, c.path("/zones"), zone, &created)
+	if err := c.do(ctx, http.MethodPost, c.path("/zones"), zone, &created); err != nil {
-	return created, err
+		return Zone{}, err
+	}
+
+	zoneID := created.ID
+	if zoneID == "" {
+		zoneID = created.Name
+	}
+	if zoneID == "" {
+		zoneID = zone.Name
+	}
+	if err := c.SetZoneSOAEditAPI(ctx, zoneID); err != nil {
+		return Zone{}, fmt.Errorf("set SOA-EDIT-API for new zone %s: %w", zoneID, err)
+	}
+
+	return created, nil
+}
+
+func (c *Client) EnsureAllZonesSOAEditAPI(ctx context.Context) error {
+	zones, err := c.ListZones(ctx)
+	if err != nil {
+		return err
+	}
+
+	for _, zone := range zones {
+		zoneID := zone.ID
+		if zoneID == "" {
+			zoneID = zone.Name
+		}
+		if zoneID == "" {
+			return fmt.Errorf("zone without id or name cannot be updated")
+		}
+		if err := c.SetZoneSOAEditAPI(ctx, zoneID); err != nil {
+			return fmt.Errorf("set SOA-EDIT-API for %s: %w", zoneID, err)
+		}
+	}
+	return nil
+}
+
+func (c *Client) SetZoneSOAEditAPI(ctx context.Context, zoneID string) error {
+	body := Zone{SOAEditAPI: soaEditAPIIncrease}
+	return c.do(ctx, http.MethodPut, c.path("/zones/"+url.PathEscape(zoneID)), body, nil)
 }
 
 func (c *Client) DeleteZone(ctx context.Context, zoneID string) error {
@@ -116,19 +154,17 @@ func (c *Client) GetZone(ctx context.Context, zoneID string) (Zone, error) {
 }
 
 func (c *Client) CreateRRSet(ctx context.Context, zoneID string, rrset RRSet) error {
-	var before *Zone
 	if allowsMultipleRecords(rrset.Type) {
 		zone, err := c.GetZone(ctx, zoneID)
 		if err != nil {
 			return fmt.Errorf("read zone before merging records: %w", err)
 		}
-		before = &zone
 		if existing, ok := findRRSet(zone, rrset.Name, rrset.Type); ok {
 			rrset.Records = mergeRecords(existing.Records, rrset.Records)
 		}
 	}
 
-	return c.patchZoneWithSerialBump(ctx, zoneID, before, []changeRRSet{{
+	return c.patchZone(ctx, zoneID, []changeRRSet{{
 		Name:       rrset.Name,
 		Type:       rrset.Type,
 		TTL:        rrset.TTL,
@@ -175,7 +211,7 @@ func recordKey(record Record) string {
 }
 
 func (c *Client) DeleteRRSet(ctx context.Context, zoneID, name, recordType string) error {
-	return c.patchZoneWithSerialBump(ctx, zoneID, nil, []changeRRSet{{
+	return c.patchZone(ctx, zoneID, []changeRRSet{{
 		Name:       name,
 		Type:       recordType,
 		ChangeType: "DELETE",
@@ -189,40 +225,6 @@ func (c *Client) patchZone(ctx context.Context, zoneID string, rrsets []changeRR
 	return c.do(ctx, http.MethodPatch, c.path("/zones/"+url.PathEscape(zoneID)), body, nil)
 }
 
-func (c *Client) patchZoneWithSerialBump(ctx context.Context, zoneID string, before *Zone, rrsets []changeRRSet) error {
-	if before == nil {
-		zone, err := c.GetZone(ctx, zoneID)
-		if err != nil {
-			return fmt.Errorf("read zone before change: %w", err)
-		}
-		before = &zone
-	}
-
-	if err := c.patchZone(ctx, zoneID, rrsets); err != nil {
-		return err
-	}
-
-	after, err := c.GetZone(ctx, zoneID)
-	if err != nil {
-		return fmt.Errorf("read zone after change: %w", err)
-	}
-	if serialIncreased(*before, after) {
-		return nil
-	}
-
-	soa, err := bumpedSOA(after, before.Serial+1)
-	if err != nil {
-		return fmt.Errorf("bump SOA serial: %w", err)
-	}
-	return c.patchZone(ctx, zoneID, []changeRRSet{{
-		Name:       soa.Name,
-		Type:       soa.Type,
-		TTL:        soa.TTL,
-		ChangeType: "REPLACE",
-		Records:    soa.Records,
-	}})
-}
-
 func (c *Client) path(suffix string) string {
 	return "/api/v1/servers/" + url.PathEscape(c.serverID) + suffix
 }
@@ -275,53 +277,3 @@ func (c *Client) do(ctx context.Context, method, apiPath string, in any, out any
 
 	return nil
 }
-
-func serialIncreased(before, after Zone) bool {
-	if after.Serial > before.Serial {
-		return true
-	}
-	if (before.EditedSerial != 0 || after.EditedSerial != 0) && after.EditedSerial > before.EditedSerial {
-		return true
-	}
-	return false
-}
-
-func bumpedSOA(zone Zone, minimum uint64) (RRSet, error) {
-	for _, rrset := range zone.RRSets {
-		if !strings.EqualFold(rrset.Type, "SOA") {
-			continue
-		}
-		if len(rrset.Records) != 1 {
-			return RRSet{}, fmt.Errorf("expected exactly one SOA record, got %d", len(rrset.Records))
-		}
-
-		record := rrset.Records[0]
-		fields := strings.Fields(record.Content)
-		if len(fields) != 7 {
-			return RRSet{}, fmt.Errorf("SOA record must have 7 fields")
-		}
-
-		current, err := strconv.ParseUint(fields[2], 10, 32)
-		if err != nil {
-			return RRSet{}, fmt.Errorf("parse SOA serial: %w", err)
-		}
-		if current == 1<<32-1 {
-			return RRSet{}, fmt.Errorf("SOA serial is already at maximum uint32 value")
-		}
-
-		next := current + 1
-		if next < minimum {
-			next = minimum
-		}
-		if next > 1<<32-1 {
-			return RRSet{}, fmt.Errorf("next SOA serial exceeds maximum uint32 value")
-		}
-
-		fields[2] = strconv.FormatUint(next, 10)
-		record.Content = strings.Join(fields, " ")
-		rrset.Records[0] = record
-		return rrset, nil
-	}
-
-	return RRSet{}, fmt.Errorf("SOA record not found")
-}

internal/pdns/client_test.go

@@ -34,7 +34,6 @@ func TestListZonesSendsAPIKey(t *testing.T) {
 
 func TestCreateRRSetPatchesZone(t *testing.T) {
 	var patchCount int
-	var getCount int
 
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if !strings.HasPrefix(r.URL.Path, "/api/v1/servers/localhost/zones/example.org.") {
@@ -43,12 +42,7 @@ func TestCreateRRSetPatchesZone(t *testing.T) {
 
 		switch r.Method {
 		case http.MethodGet:
-			getCount++
+			writeZoneWithRRSets(t, w, 10, nil)
-			serial := uint64(10)
-			if getCount == 2 {
-				serial = 11
-			}
-			writeZone(t, w, serial)
 		case http.MethodPatch:
 			patchCount++
 			var payload struct {
@@ -80,62 +74,7 @@ func TestCreateRRSetPatchesZone(t *testing.T) {
 		t.Fatalf("CreateRRSet returned error: %v", err)
 	}
 	if patchCount != 1 {
-		t.Fatalf("expected one patch when serial increases, got %d", patchCount)
+		t.Fatalf("expected one patch, got %d", patchCount)
-	}
-}
-
-func TestCreateRRSetBumpsSOAWhenSerialDoesNotIncrease(t *testing.T) {
-	var patchCount int
-
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if !strings.HasPrefix(r.URL.Path, "/api/v1/servers/localhost/zones/example.org.") {
-			t.Fatalf("unexpected path: %s", r.URL.Path)
-		}
-
-		switch r.Method {
-		case http.MethodGet:
-			writeZone(t, w, 10)
-		case http.MethodPatch:
-			patchCount++
-			var payload struct {
-				RRSets []changeRRSet `json:"rrsets"`
-			}
-			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
-				t.Fatalf("decode request: %v", err)
-			}
-			if len(payload.RRSets) != 1 {
-				t.Fatalf("unexpected payload: %#v", payload)
-			}
-			if patchCount == 2 {
-				rrset := payload.RRSets[0]
-				if rrset.Type != "SOA" {
-					t.Fatalf("expected SOA fallback patch, got %#v", rrset)
-				}
-				if got := rrset.Records[0].Content; !strings.Contains(got, " 11 ") {
-					t.Fatalf("expected bumped SOA serial, got %q", got)
-				}
-			}
-			w.WriteHeader(http.StatusNoContent)
-		default:
-			t.Fatalf("unexpected method: %s", r.Method)
-		}
-	}))
-	defer server.Close()
-
-	client := NewClient(server.URL, "secret", "localhost", server.Client())
-	err := client.CreateRRSet(context.Background(), "example.org.", RRSet{
-		Name: "www.example.org.",
-		Type: "A",
-		TTL:  300,
-		Records: []Record{{
-			Content: "192.0.2.10",
-		}},
-	})
-	if err != nil {
-		t.Fatalf("CreateRRSet returned error: %v", err)
-	}
-	if patchCount != 2 {
-		t.Fatalf("expected requested patch plus SOA fallback patch, got %d", patchCount)
 	}
 }
 
@@ -281,23 +220,45 @@ func TestGetServerUsesConfiguredServerID(t *testing.T) {
 }
 
 func TestCreateZonePostsZone(t *testing.T) {
+	var posted bool
+	var put bool
+
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.Method != http.MethodPost {
+		switch r.Method {
+		case http.MethodPost:
+			posted = true
+			if r.URL.Path != "/api/v1/servers/localhost/zones" {
+				t.Fatalf("unexpected path: %s", r.URL.Path)
+			}
+
+			var payload Zone
+			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+				t.Fatalf("decode request: %v", err)
+			}
+			if payload.Name != "example.org." || payload.Kind != "Native" {
+				t.Fatalf("unexpected payload: %#v", payload)
+			}
+			if payload.SOAEditAPI != soaEditAPIIncrease {
+				t.Fatalf("unexpected soa_edit_api: %q", payload.SOAEditAPI)
+			}
+			w.WriteHeader(http.StatusCreated)
+			_ = json.NewEncoder(w).Encode(payload)
+		case http.MethodPut:
+			put = true
+			if r.URL.Path != "/api/v1/servers/localhost/zones/example.org." {
+				t.Fatalf("unexpected path: %s", r.URL.Path)
+			}
+			var payload Zone
+			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+				t.Fatalf("decode request: %v", err)
+			}
+			if payload.SOAEditAPI != soaEditAPIIncrease {
+				t.Fatalf("unexpected soa_edit_api: %q", payload.SOAEditAPI)
+			}
+			w.WriteHeader(http.StatusNoContent)
+		default:
 			t.Fatalf("unexpected method: %s", r.Method)
 		}
-		if r.URL.Path != "/api/v1/servers/localhost/zones" {
-			t.Fatalf("unexpected path: %s", r.URL.Path)
-		}
-
-		var payload Zone
-		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
-			t.Fatalf("decode request: %v", err)
-		}
-		if payload.Name != "example.org." || payload.Kind != "Native" {
-			t.Fatalf("unexpected payload: %#v", payload)
-		}
-		w.WriteHeader(http.StatusCreated)
-		_ = json.NewEncoder(w).Encode(payload)
 	}))
 	defer server.Close()
 
@@ -309,6 +270,78 @@ func TestCreateZonePostsZone(t *testing.T) {
 	if created.Name != "example.org." {
 		t.Fatalf("unexpected zone: %#v", created)
 	}
+	if !posted || !put {
+		t.Fatalf("expected POST and follow-up PUT, posted=%v put=%v", posted, put)
+	}
+}
+
+func TestEnsureAllZonesSOAEditAPIUpdatesAllZones(t *testing.T) {
+	var updated []string
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		switch r.Method {
+		case http.MethodGet:
+			if r.URL.Path != "/api/v1/servers/localhost/zones" {
+				t.Fatalf("unexpected path: %s", r.URL.Path)
+			}
+			_ = json.NewEncoder(w).Encode([]Zone{
+				{ID: "already.example.org.", Name: "already.example.org.", SOAEditAPI: soaEditAPIIncrease},
+				{ID: "missing.example.org.", Name: "missing.example.org."},
+				{ID: "", Name: "fallback.example.org.", SOAEditAPI: "DEFAULT"},
+			})
+		case http.MethodPut:
+			var payload Zone
+			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+				t.Fatalf("decode request: %v", err)
+			}
+			if payload.SOAEditAPI != soaEditAPIIncrease {
+				t.Fatalf("unexpected soa_edit_api: %q", payload.SOAEditAPI)
+			}
+			updated = append(updated, strings.TrimPrefix(r.URL.Path, "/api/v1/servers/localhost/zones/"))
+			w.WriteHeader(http.StatusNoContent)
+		default:
+			t.Fatalf("unexpected method: %s", r.Method)
+		}
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "secret", "localhost", server.Client())
+	if err := client.EnsureAllZonesSOAEditAPI(context.Background()); err != nil {
+		t.Fatalf("EnsureAllZonesSOAEditAPI returned error: %v", err)
+	}
+
+	if len(updated) != 3 {
+		t.Fatalf("expected three updates, got %#v", updated)
+	}
+	if updated[0] != "already.example.org." || updated[1] != "missing.example.org." || updated[2] != "fallback.example.org." {
+		t.Fatalf("unexpected updated zones: %#v", updated)
+	}
+}
+
+func TestSetZoneSOAEditAPIUsesPUT(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPut {
+			t.Fatalf("unexpected method: %s", r.Method)
+		}
+		if r.URL.Path != "/api/v1/servers/localhost/zones/example.org." {
+			t.Fatalf("unexpected path: %s", r.URL.Path)
+		}
+
+		var payload Zone
+		if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
+			t.Fatalf("decode request: %v", err)
+		}
+		if payload.SOAEditAPI != soaEditAPIIncrease {
+			t.Fatalf("unexpected soa_edit_api: %q", payload.SOAEditAPI)
+		}
+		w.WriteHeader(http.StatusNoContent)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "secret", "localhost", server.Client())
+	if err := client.SetZoneSOAEditAPI(context.Background(), "example.org."); err != nil {
+		t.Fatalf("SetZoneSOAEditAPI returned error: %v", err)
+	}
 }
 
 func TestDeleteZoneDeletesZone(t *testing.T) {
@@ -329,12 +362,6 @@ func TestDeleteZoneDeletesZone(t *testing.T) {
 	}
 }
 
-func writeZone(t *testing.T, w http.ResponseWriter, serial uint64) {
-	t.Helper()
-
-	writeZoneWithRRSets(t, w, serial, nil)
-}
-
 func writeZoneWithRRSets(t *testing.T, w http.ResponseWriter, serial uint64, rrsets []RRSet) {
 	t.Helper()
 

internal/server/server.go

@@ -3,6 +3,7 @@ package server
 import (
 	"context"
 	"crypto/rand"
+	"crypto/subtle"
 	"embed"
 	"encoding/base64"
 	"fmt"
@@ -23,7 +24,8 @@ import (
 var assets embed.FS
 
 const (
-	sessionCookieName = "pdns_admin_session"
+	csrfFieldName     = "csrf_token"
+	sessionCookieName = "__Host-pdns_admin_session"
 	sessionTTL        = 12 * time.Hour
 )
 
@@ -62,6 +64,7 @@ type pageData struct {
 	Error       string
 	AuthEnabled bool
 	CurrentUser string
+	CSRFToken   string
 	Next        string
 	Server      pdns.Server
 	ZoneID      string
@@ -72,21 +75,19 @@ type pageData struct {
 }
 
 type session struct {
-	Username string
+	Username  string
-	Expires  time.Time
+	CSRFToken string
+	Expires   time.Time
 }
 
 type recordForm struct {
-	Name         string
+	Name        string
-	Type         string
+	Type        string
-	TTL          uint32
+	TTL         uint32
-	Records      string
+	Records     string
-	OriginalName string
+	IsEdit      bool
-	OriginalType string
+	Title       string
-	IsEdit       bool
+	SubmitLabel string
-	IsSOA        bool
-	Title        string
-	SubmitLabel  string
 }
 
 func New(cfg Config, client PDNSClient, logger *log.Logger) (*Server, error) {
@@ -106,9 +107,8 @@ func New(cfg Config, client PDNSClient, logger *log.Logger) (*Server, error) {
 
 	templates := make(map[string]*template.Template)
 	funcs := template.FuncMap{
-		"isSOA":        isSOA,
+		"isSOA":    isSOA,
-		"recordValues": recordValues,
+		"urlQuery": url.QueryEscape,
-		"urlQuery":     url.QueryEscape,
 	}
 	for _, page := range []string{"dashboard.html", "login.html", "zones.html", "zone.html", "record_form.html"} {
 		tmpl, err := template.New("base.html").Funcs(funcs).ParseFS(assets, "templates/base.html", "templates/"+page)
@@ -139,7 +139,7 @@ func (s *Server) routes() http.Handler {
 	mux.HandleFunc("GET /healthz", s.healthz)
 	mux.HandleFunc("GET /login", s.login)
 	mux.HandleFunc("POST /login", s.loginPost)
-	mux.HandleFunc("GET /logout", s.logout)
+	mux.HandleFunc("POST /logout", s.logout)
 	mux.HandleFunc("GET /", s.dashboard)
 	mux.HandleFunc("GET /zones", s.listZones)
 	mux.HandleFunc("POST /zones", s.createZone)
@@ -150,7 +150,7 @@ func (s *Server) routes() http.Handler {
 	mux.HandleFunc("POST /zones/{zoneID}/rrsets", s.saveRRSet)
 	mux.HandleFunc("POST /zones/{zoneID}/rrsets/edit", s.saveEditedRRSet)
 	mux.HandleFunc("POST /zones/{zoneID}/rrsets/delete", s.deleteRRSet)
-	return s.withLogging(s.withSessionAuth(mux))
+	return s.withLogging(s.withSecurityHeaders(s.withSessionAuth(mux)))
 }
 
 func (s *Server) healthz(w http.ResponseWriter, _ *http.Request) {
@@ -226,8 +226,10 @@ func (s *Server) loginPost(w http.ResponseWriter, r *http.Request) {
 		Value:    token,
 		Path:     "/",
 		Expires:  time.Now().Add(sessionTTL),
+		MaxAge:   int(sessionTTL.Seconds()),
 		HttpOnly: true,
-		SameSite: http.SameSiteLaxMode,
+		Secure:   true,
+		SameSite: http.SameSiteStrictMode,
 	})
 
 	http.Redirect(w, r, safeRedirectPath(r.FormValue("next")), http.StatusSeeOther)
@@ -244,7 +246,8 @@ func (s *Server) logout(w http.ResponseWriter, r *http.Request) {
 		Expires:  time.Unix(0, 0),
 		MaxAge:   -1,
 		HttpOnly: true,
-		SameSite: http.SameSiteLaxMode,
+		Secure:   true,
+		SameSite: http.SameSiteStrictMode,
 	})
 	http.Redirect(w, r, "/login", http.StatusSeeOther)
 }
@@ -363,7 +366,6 @@ func (s *Server) editRRSet(w http.ResponseWriter, r *http.Request) {
 		TTL:         rrset.TTL,
 		Records:     recordValues(rrset),
 		IsEdit:      true,
-		IsSOA:       isSOA(rrset.Type),
 		Title:       "Edit record",
 		SubmitLabel: "Save record",
 	}
@@ -445,7 +447,7 @@ func (s *Server) deleteRRSet(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	name := ensureTrailingDot(r.FormValue("name"))
+	name := dnsrecord.EnsureTrailingDot(r.FormValue("name"))
 	recordType := strings.ToUpper(strings.TrimSpace(r.FormValue("type")))
 	if name == "." || recordType == "" {
 		s.redirectZoneError(w, r, zoneID, "record name and type are required")
@@ -466,8 +468,9 @@ func (s *Server) deleteRRSet(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) render(w http.ResponseWriter, r *http.Request, name string, data pageData) {
 	data.AuthEnabled = s.auth != nil
-	if user, ok := s.currentUser(r); ok {
+	if sess, ok := s.currentSession(r); ok {
-		data.CurrentUser = user
+		data.CurrentUser = sess.Username
+		data.CSRFToken = sess.CSRFToken
 	}
 	w.Header().Set("Content-Type", "text/html; charset=utf-8")
 	tmpl, ok := s.templates[name]
@@ -498,46 +501,64 @@ func (s *Server) withSessionAuth(next http.Handler) http.Handler {
 			next.ServeHTTP(w, r)
 			return
 		}
-		if _, ok := s.currentUser(r); !ok {
+		sess, ok := s.currentSession(r)
+		if !ok {
 			http.Redirect(w, r, "/login?next="+url.QueryEscape(r.URL.RequestURI()), http.StatusSeeOther)
 			return
 		}
+		if isUnsafeMethod(r.Method) && !validCSRFToken(r, sess.CSRFToken) {
+			http.Error(w, "invalid CSRF token", http.StatusForbidden)
+			return
+		}
 		next.ServeHTTP(w, r)
 	})
 }
 
 func (s *Server) currentUser(r *http.Request) (string, bool) {
-	cookie, err := r.Cookie(sessionCookieName)
+	sess, ok := s.currentSession(r)
-	if err != nil || cookie.Value == "" {
+	if !ok {
 		return "", false
 	}
+	return sess.Username, true
+}
+
+func (s *Server) currentSession(r *http.Request) (session, bool) {
+	cookie, err := r.Cookie(sessionCookieName)
+	if err != nil || cookie.Value == "" || len(cookie.Value) > 128 {
+		return session{}, false
+	}
 
 	s.sessionsM.Lock()
 	defer s.sessionsM.Unlock()
 
 	sess, ok := s.sessions[cookie.Value]
 	if !ok {
-		return "", false
+		return session{}, false
 	}
 	if time.Now().After(sess.Expires) {
 		delete(s.sessions, cookie.Value)
-		return "", false
+		return session{}, false
 	}
-	return sess.Username, true
+	return sess, true
 }
 
 func (s *Server) createSession(username string) (string, error) {
-	tokenBytes := make([]byte, 32)
+	token, err := randomToken()
-	if _, err := rand.Read(tokenBytes); err != nil {
+	if err != nil {
+		return "", err
+	}
+	csrfToken, err := randomToken()
+	if err != nil {
 		return "", err
 	}
-	token := base64.RawURLEncoding.EncodeToString(tokenBytes)
 
 	s.sessionsM.Lock()
 	defer s.sessionsM.Unlock()
+	s.pruneExpiredSessionsLocked(time.Now())
 	s.sessions[token] = session{
-		Username: username,
+		Username:  username,
-		Expires:  time.Now().Add(sessionTTL),
+		CSRFToken: csrfToken,
+		Expires:   time.Now().Add(sessionTTL),
 	}
 	return token, nil
 }
@@ -548,8 +569,16 @@ func (s *Server) deleteSession(token string) {
 	delete(s.sessions, token)
 }
 
+func (s *Server) pruneExpiredSessionsLocked(now time.Time) {
+	for token, sess := range s.sessions {
+		if now.After(sess.Expires) {
+			delete(s.sessions, token)
+		}
+	}
+}
+
 func isPublicPath(path string) bool {
-	return path == "/login" || path == "/logout" || path == "/healthz" || strings.HasPrefix(path, "/static/")
+	return path == "/login" || path == "/healthz" || strings.HasPrefix(path, "/static/")
 }
 
 func safeRedirectPath(value string) string {
@@ -563,6 +592,52 @@ func safeRedirectPath(value string) string {
 	return parsed.RequestURI()
 }
 
+func isUnsafeMethod(method string) bool {
+	switch method {
+	case http.MethodGet, http.MethodHead, http.MethodOptions, http.MethodTrace:
+		return false
+	default:
+		return true
+	}
+}
+
+func validCSRFToken(r *http.Request, expected string) bool {
+	if expected == "" {
+		return false
+	}
+	if err := r.ParseForm(); err != nil {
+		return false
+	}
+	token := r.FormValue(csrfFieldName)
+	if token == "" {
+		token = r.Header.Get("X-CSRF-Token")
+	}
+	return subtle.ConstantTimeCompare([]byte(token), []byte(expected)) == 1
+}
+
+func randomToken() (string, error) {
+	tokenBytes := make([]byte, 32)
+	if _, err := rand.Read(tokenBytes); err != nil {
+		return "", err
+	}
+	return base64.RawURLEncoding.EncodeToString(tokenBytes), nil
+}
+
+func (s *Server) withSecurityHeaders(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Security-Policy", "default-src 'self'; script-src 'self'; style-src 'self'; img-src 'self' data:; font-src 'self' data:; base-uri 'self'; form-action 'self'; frame-ancestors 'none'")
+		w.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=()")
+		w.Header().Set("Referrer-Policy", "same-origin")
+		w.Header().Set("Strict-Transport-Security", "max-age=31536000; includeSubDomains")
+		w.Header().Set("X-Content-Type-Options", "nosniff")
+		w.Header().Set("X-Frame-Options", "DENY")
+		if !strings.HasPrefix(r.URL.Path, "/static/") {
+			w.Header().Set("Cache-Control", "no-store")
+		}
+		next.ServeHTTP(w, r)
+	})
+}
+
 func (s *Server) withLogging(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		start := time.Now()
@@ -584,10 +659,6 @@ func parseLines(raw string) []string {
 	return values
 }
 
-func ensureTrailingDot(value string) string {
-	return dnsrecord.EnsureTrailingDot(value)
-}
-
 func parseFQDNLines(raw, label string) ([]string, error) {
 	values := parseLines(raw)
 	for i, value := range values {

internal/server/server_test.go

@@ -154,6 +154,15 @@ func TestLoginCreatesSession(t *testing.T) {
 	if len(cookies) == 0 || cookies[0].Name != sessionCookieName {
 		t.Fatalf("expected session cookie, got %#v", cookies)
 	}
+	if !cookies[0].HttpOnly {
+		t.Fatal("session cookie must be HttpOnly")
+	}
+	if !cookies[0].Secure {
+		t.Fatal("session cookie must be Secure")
+	}
+	if cookies[0].SameSite != http.SameSiteStrictMode {
+		t.Fatalf("unexpected SameSite policy: %v", cookies[0].SameSite)
+	}
 
 	req = httptest.NewRequest(http.MethodGet, "/zones", nil)
 	req.AddCookie(cookies[0])
@@ -196,9 +205,12 @@ func TestLogoutClearsSession(t *testing.T) {
 	if err != nil {
 		t.Fatalf("createSession returned error: %v", err)
 	}
+	csrfToken := srv.sessions[token].CSRFToken
 
-	req := httptest.NewRequest(http.MethodGet, "/logout", nil)
+	body := strings.NewReader("csrf_token=" + csrfToken)
+	req := httptest.NewRequest(http.MethodPost, "/logout", body)
 	req.AddCookie(&http.Cookie{Name: sessionCookieName, Value: token})
+	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
 	rec := httptest.NewRecorder()
 
 	srv.routes().ServeHTTP(rec, req)
@@ -211,6 +223,51 @@ func TestLogoutClearsSession(t *testing.T) {
 	}
 }
 
+func TestLogoutRequiresCSRF(t *testing.T) {
+	srv, err := New(Config{Authenticator: &fakeAuth{allowed: true}}, &fakeClient{}, nil)
+	if err != nil {
+		t.Fatalf("New returned error: %v", err)
+	}
+	token, err := srv.createSession("alice")
+	if err != nil {
+		t.Fatalf("createSession returned error: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodPost, "/logout", nil)
+	req.AddCookie(&http.Cookie{Name: sessionCookieName, Value: token})
+	rec := httptest.NewRecorder()
+
+	srv.routes().ServeHTTP(rec, req)
+
+	if rec.Code != http.StatusForbidden {
+		t.Fatalf("unexpected status: %d", rec.Code)
+	}
+}
+
+func TestSecurityHeadersAreSet(t *testing.T) {
+	srv, err := New(Config{}, &fakeClient{}, nil)
+	if err != nil {
+		t.Fatalf("New returned error: %v", err)
+	}
+
+	req := httptest.NewRequest(http.MethodGet, "/healthz", nil)
+	rec := httptest.NewRecorder()
+
+	srv.routes().ServeHTTP(rec, req)
+
+	for _, header := range []string{
+		"Content-Security-Policy",
+		"Referrer-Policy",
+		"Strict-Transport-Security",
+		"X-Content-Type-Options",
+		"X-Frame-Options",
+	} {
+		if rec.Header().Get(header) == "" {
+			t.Fatalf("expected %s header", header)
+		}
+	}
+}
+
 func TestParseLinesSkipsBlankLines(t *testing.T) {
 	values := parseLines("192.0.2.1\n\n192.0.2.2\n")
 	if len(values) != 2 {

internal/server/templates/base.html

@@ -31,9 +31,12 @@
             {{ if .CurrentUser }}
               <div class="navbar-nav ms-auto">
                 <span class="nav-link text-secondary">{{ .CurrentUser }}</span>
-                <a class="nav-link" href="/logout">
+                <form method="post" action="/logout" class="nav-item">
-                  <span class="nav-link-title">Logout</span>
+                  <input type="hidden" name="csrf_token" value="{{ .CSRFToken }}">
-                </a>
+                  <button class="nav-link btn btn-link px-0" type="submit">
+                    <span class="nav-link-title">Logout</span>
+                  </button>
+                </form>
               </div>
             {{ end }}
           {{ end }}

internal/server/templates/record_form.html

@@ -29,6 +29,7 @@
         {{ end }}
 
         <form method="post" action="{{ if .RecordForm.IsEdit }}/zones/{{ .ZoneID }}/rrsets/edit?name={{ urlQuery .RecordForm.Name }}&type={{ urlQuery .RecordForm.Type }}{{ else }}/zones/{{ .ZoneID }}/rrsets{{ end }}">
+          <input type="hidden" name="csrf_token" value="{{ .CSRFToken }}">
           {{ if not .RecordForm.IsEdit }}
             <div class="mb-3">
               <label class="form-label">Name</label>

internal/server/templates/zone.html

@@ -49,6 +49,7 @@
                 <a class="btn btn-outline-primary btn-sm" href="/zones/{{ $.ZoneID }}/rrsets/edit?name={{ urlQuery .Name }}&type={{ urlQuery .Type }}">Edit</a>
                 {{ if not (isSOA .Type) }}
                 <form method="post" action="/zones/{{ $.ZoneID }}/rrsets/delete">
+                  <input type="hidden" name="csrf_token" value="{{ $.CSRFToken }}">
                   <input type="hidden" name="name" value="{{ .Name }}">
                   <input type="hidden" name="type" value="{{ .Type }}">
                   <button class="btn btn-outline-danger btn-sm" type="submit">Delete</button>

internal/server/templates/zones.html

@@ -34,6 +34,7 @@
               <td>{{ .Serial }}</td>
               <td>
                 <form method="post" action="/zones/{{ .ID }}/delete">
+                  <input type="hidden" name="csrf_token" value="{{ $.CSRFToken }}">
                   <button class="btn btn-outline-danger btn-sm" type="submit">Delete</button>
                 </form>
               </td>
@@ -55,6 +56,7 @@
       </div>
       <div class="card-body">
         <form method="post" action="/zones">
+          <input type="hidden" name="csrf_token" value="{{ .CSRFToken }}">
           <div class="mb-3">
             <label class="form-label">Zone name</label>
             <input class="form-control" name="name" placeholder="example.org." required>