coredns-rfc2136/update_test.go

package rfc2136

import (
	"net"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/miekg/dns"
)

// captureWriter implements dns.ResponseWriter and stashes the message
// passed to WriteMsg so tests can inspect it after handleUpdate returns.
type captureWriter struct {
	msg *dns.Msg
}

func (cw *captureWriter) WriteMsg(m *dns.Msg) error             { cw.msg = m; return nil }
func (cw *captureWriter) Write([]byte) (int, error)             { return 0, nil }
func (cw *captureWriter) Close() error                          { return nil }
func (cw *captureWriter) TsigStatus() error                     { return nil }
func (cw *captureWriter) TsigTimersOnly(bool)                   {}
func (cw *captureWriter) Hijack()                               {}
func (cw *captureWriter) LocalAddr() net.Addr                   { return &net.IPAddr{IP: net.IPv4(127, 0, 0, 1)} }
func (cw *captureWriter) RemoteAddr() net.Addr                  { return &net.IPAddr{IP: net.IPv4(127, 0, 0, 1)} }
func (cw *captureWriter) Network() string                       { return "udp" }

// newTestPluginWithZone builds an RFC2136 backed by a temp zones-dir.
// AutoCommit is disabled by default (tests don't need git side-effects).
func newTestPluginWithZone(t *testing.T, zone string) *RFC2136 {
	t.Helper()
	dir := withTempZonesDir(t, zone)
	zone = dns.Fqdn(zone)

	p := &RFC2136{
		Zones:    []string{zone},
		TTL:      60,
		ZonesDir: dir,
		zones: map[string]*zoneFile{
			zone: openZoneFile(filepath.Join(dir, strings.TrimSuffix(zone, ".")+".zone"), zone),
		},
	}
	p.zones[zone].AutoCommit = false
	return p
}

// newUpdate builds an UPDATE message for `zone` with zero prereqs and
// the given update RRs. Matches what caddy-dns/rfc2136 sends.
func newUpdate(zone string, updates ...dns.RR) *dns.Msg {
	m := new(dns.Msg)
	m.SetUpdate(dns.Fqdn(zone))
	m.Ns = append(m.Ns, updates...)
	return m
}

// runUpdate sends msg through the handler with TSIG auth bypassed
// (calling handleUpdate directly with verified=true instead of
// ServeDNS). Tests that exercise post-auth logic use this; tests that
// assert auth-failure behavior should call handleUpdate(w, msg, false)
// directly.
func runUpdate(t *testing.T, p *RFC2136, msg *dns.Msg) (rcode int) {
	t.Helper()
	w := &captureWriter{}
	rcode, _ = p.handleUpdate(w, msg, true)
	return rcode
}

// readZoneRecords loads the zone file and returns the RRs for inspection.
func readZoneRecords(t *testing.T, p *RFC2136, zone string) []dns.RR {
	t.Helper()
	zf := p.zones[dns.Fqdn(zone)]
	rrs, _, err := zf.loadRRs()
	if err != nil {
		t.Fatalf("loadRRs: %v", err)
	}
	return rrs
}

func TestUpdate_AddSingleTXT_PersistsToFile(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	upd := newUpdate("auth.example.com",
		mustRR(t, `token-1.auth.example.com. 60 IN TXT "validation-1"`),
	)
	if rcode := runUpdate(t, p, upd); rcode != dns.RcodeSuccess {
		t.Fatalf("rcode = %d, want NOERROR", rcode)
	}

	// Verify by re-reading the file.
	rrs := readZoneRecords(t, p, "auth.example.com")
	for _, rr := range rrs {
		if txt, ok := rr.(*dns.TXT); ok && txt.Hdr.Name == "token-1.auth.example.com." {
			if txt.Txt[0] == "validation-1" {
				return // success
			}
		}
	}
	t.Errorf("added TXT not found in re-read zone file")
}

func TestUpdate_AddBumpsSerial(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	before := readZoneRecords(t, p, "auth.example.com")
	var beforeSerial uint32
	for _, rr := range before {
		if soa, ok := rr.(*dns.SOA); ok {
			beforeSerial = soa.Serial
			break
		}
	}

	upd := newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "x"`),
	)
	runUpdate(t, p, upd)

	after := readZoneRecords(t, p, "auth.example.com")
	var afterSerial uint32
	for _, rr := range after {
		if soa, ok := rr.(*dns.SOA); ok {
			afterSerial = soa.Serial
			break
		}
	}
	if afterSerial <= beforeSerial {
		t.Errorf("Serial did not advance: before=%d after=%d", beforeSerial, afterSerial)
	}
}

func TestUpdate_DeleteRRset_RemovesAllOfType(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	// First add two TXTs at the same name.
	runUpdate(t, p, newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "a"`),
		mustRR(t, `foo.auth.example.com. 60 IN TXT "b"`),
	))

	// Now delete the whole TXT RRset.
	del := &dns.ANY{Hdr: dns.RR_Header{
		Name:   "foo.auth.example.com.",
		Rrtype: dns.TypeTXT,
		Class:  dns.ClassANY,
	}}
	if rcode := runUpdate(t, p, newUpdate("auth.example.com", del)); rcode != dns.RcodeSuccess {
		t.Fatalf("delete rcode = %d", rcode)
	}

	for _, rr := range readZoneRecords(t, p, "auth.example.com") {
		if rr.Header().Rrtype == dns.TypeTXT && rr.Header().Name == "foo.auth.example.com." {
			t.Errorf("TXT %s should be gone, still present: %s", rr.Header().Name, rr.String())
		}
	}
}

// TestUpdate_UnverifiedCaller_Refused proves the C2 defense-in-depth
// contract: handleUpdate refuses any call that doesn't assert TSIG
// verification, even if the rest of the message is well-formed and the
// zone is authoritative. This guards against a future internal caller
// that bypasses the wire-level TSIG check in ServeDNS.
func TestUpdate_UnverifiedCaller_Refused(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")
	upd := newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "should-not-apply"`),
	)
	w := &captureWriter{}
	rcode, _ := p.handleUpdate(w, upd, false) // <- the security boundary
	if rcode != dns.RcodeRefused {
		t.Errorf("rcode = %d, want REFUSED for unverified caller", rcode)
	}
	// Zone file must NOT have been modified.
	for _, rr := range readZoneRecords(t, p, "auth.example.com") {
		if txt, ok := rr.(*dns.TXT); ok && txt.Hdr.Name == "foo.auth.example.com." {
			t.Errorf("unverified UPDATE applied state mutation: %s", rr.String())
		}
	}
}

func TestUpdate_OutOfZone_Refused(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	upd := newUpdate("auth.example.com",
		mustRR(t, `evil.other.tld. 60 IN TXT "nope"`),
	)
	if rcode := runUpdate(t, p, upd); rcode != dns.RcodeNotZone {
		t.Errorf("rcode = %d, want NOTZONE (%d)", rcode, dns.RcodeNotZone)
	}
}

func TestUpdate_UnknownZone_NOTAUTH(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	// Build UPDATE for a zone we don't manage.
	m := new(dns.Msg)
	m.SetUpdate("other.zone.")
	m.Ns = []dns.RR{mustRR(t, `x.other.zone. 60 IN TXT "y"`)}

	if rcode := runUpdate(t, p, m); rcode != dns.RcodeNotAuth {
		t.Errorf("rcode = %d, want NOTAUTH (%d)", rcode, dns.RcodeNotAuth)
	}
}

func TestUpdate_ApexSOADeletion_Refused(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	// CLASS=ANY type=SOA at apex → would wipe the SOA.
	del := &dns.ANY{Hdr: dns.RR_Header{
		Name:   "auth.example.com.",
		Rrtype: dns.TypeSOA,
		Class:  dns.ClassANY,
	}}
	if rcode := runUpdate(t, p, newUpdate("auth.example.com", del)); rcode != dns.RcodeRefused {
		t.Errorf("rcode = %d, want REFUSED", rcode)
	}

	// SOA must still be in the file.
	hasSOA := false
	for _, rr := range readZoneRecords(t, p, "auth.example.com") {
		if _, ok := rr.(*dns.SOA); ok {
			hasSOA = true
			break
		}
	}
	if !hasSOA {
		t.Errorf("SOA was deleted despite REFUSED rcode")
	}
}

func TestUpdate_ApexWipe_Refused(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	del := &dns.ANY{Hdr: dns.RR_Header{
		Name:   "auth.example.com.",
		Rrtype: dns.TypeANY,
		Class:  dns.ClassANY,
	}}
	if rcode := runUpdate(t, p, newUpdate("auth.example.com", del)); rcode != dns.RcodeRefused {
		t.Errorf("rcode = %d, want REFUSED", rcode)
	}
}

func TestUpdate_PrereqRRsetMustNotExist_YXRRSET(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	// Seed a TXT then send an UPDATE whose prereq says "no TXT here".
	runUpdate(t, p, newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "present"`),
	))

	prereq := &dns.ANY{Hdr: dns.RR_Header{
		Name:   "foo.auth.example.com.",
		Rrtype: dns.TypeTXT,
		Class:  dns.ClassNONE,
	}}
	m := new(dns.Msg)
	m.SetUpdate("auth.example.com.")
	m.Answer = []dns.RR{prereq}
	m.Ns = []dns.RR{mustRR(t, `foo.auth.example.com. 60 IN TXT "should-not-be-added"`)}

	if rcode := runUpdate(t, p, m); rcode != dns.RcodeYXRrset {
		t.Errorf("rcode = %d, want YXRRSET", rcode)
	}
}

func TestUpdate_NoOpAdd_DoesntRewriteFile(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	// Add a record once.
	runUpdate(t, p, newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "x"`),
	))

	path := p.zones["auth.example.com."].Path
	beforeStat, _ := os.Stat(path)

	// Same UPDATE again — should be a no-op (dedupe).
	runUpdate(t, p, newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "x"`),
	))

	afterStat, _ := os.Stat(path)
	if afterStat.ModTime().After(beforeStat.ModTime()) {
		t.Errorf("file was rewritten despite no-op update (mtime advanced)")
	}
}

// TestUpdate_SignedRequest_ResponseGetsTSIG verifies the RFC 8945 §5.4.2
// requirement that a server's response to a TSIG-signed request must
// itself carry TSIG so the client can authenticate the answer. Before
// this fix, BIND nsupdate complained "expected a TSIG or SIG(0)" because
// the response went back without any TSIG record attached.
func TestUpdate_SignedRequest_ResponseGetsTSIG(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	upd := newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "x"`),
	)
	// Attach a TSIG to the request — the values mimic what nsupdate
	// or caddy-dns/rfc2136 emit. handleUpdate runs WITHOUT MAC
	// verification in this test (that's ServeDNS's job and is
	// covered separately), so the TSIG record's MAC contents don't
	// matter — only the presence/algorithm/name do.
	upd.SetTsig("acme-update-key.", dns.HmacSHA256, 300, 0)

	w := &captureWriter{}
	if _, err := p.handleUpdate(w, upd, true); err != nil {
		t.Fatalf("handleUpdate: %v", err)
	}
	if w.msg == nil {
		t.Fatal("response was not written")
	}
	got := w.msg.IsTsig()
	if got == nil {
		t.Fatal("response missing TSIG — nsupdate would reject as 'expected a TSIG or SIG(0)'")
	}
	if !strings.EqualFold(got.Hdr.Name, "acme-update-key.") {
		t.Errorf("response TSIG key = %q, want acme-update-key.", got.Hdr.Name)
	}
	if !strings.EqualFold(got.Algorithm, dns.HmacSHA256) {
		t.Errorf("response TSIG alg = %q, want %s", got.Algorithm, dns.HmacSHA256)
	}
}

// TestUpdate_UnsignedRequest_ResponseStaysUnsigned guards the no-op
// branch — if the client didn't sign, we don't synthesize a TSIG on
// the response (we couldn't pick a key anyway).
func TestUpdate_UnsignedRequest_ResponseStaysUnsigned(t *testing.T) {
	p := newTestPluginWithZone(t, "auth.example.com")

	upd := newUpdate("auth.example.com",
		mustRR(t, `foo.auth.example.com. 60 IN TXT "x"`),
	)
	// No SetTsig — request is plain.

	w := &captureWriter{}
	if _, err := p.handleUpdate(w, upd, true); err != nil {
		t.Fatalf("handleUpdate: %v", err)
	}
	if w.msg.IsTsig() != nil {
		t.Error("response carries TSIG despite unsigned request")
	}
}

func TestFindZone_LongestSuffixWins(t *testing.T) {
	p := &RFC2136{Zones: []string{"example.com.", "auth.example.com."}}
	if got := p.findZone("foo.auth.example.com."); got != "auth.example.com." {
		t.Errorf("findZone returned %q, expected longest match", got)
	}
}

func TestFindZone_OutsideAllZones(t *testing.T) {
	p := &RFC2136{Zones: []string{"auth.example.com."}}
	if got := p.findZone("other.tld."); got != "" {
		t.Errorf("findZone returned %q, want empty", got)
	}
}

func TestFindZone_CaseInsensitive(t *testing.T) {
	p := &RFC2136{Zones: []string{"auth.example.com."}}
	if got := p.findZone("Foo.AUTH.example.COM."); got != "auth.example.com." {
		t.Errorf("case-insensitive findZone returned %q", got)
	}
}