Separate the window sentence from the wrapped error so a bad certificate file is not reported as a key mismatch.

Co-authored-by: Cursor <cursoragent@cursor.com>

CONTEXT.md

@@ -29,8 +29,24 @@ The uppercase amateur call sign that names this station on the reflector.
 _Avoid_: a lowercase spelling, username, node id
 
 **Auth key**:
-The secret the network issues for this station’s callsign, used to prove identity to the reflector.
+The shared secret the network issues for this station’s callsign. It proves the station on protocol 2.0, and on protocol 3.0 when the reflector has not signed a certificate yet.
-_Avoid_: certificate, a password sent in the clear
+_Avoid_: a password sent in the clear, the certificate
+
+**Certificate**:
+An X.509 certificate whose common name is this station’s callsign. It proves the station on protocol 3.0.
+_Avoid_: auth key, a PEM pasted into the config file
+
+**Certificate directory**:
+The directory the station config names. It holds the CA bundle and this station’s key and certificate.
+_Avoid_: PEM text inside the config file
+
+**CA bundle**:
+The reflector’s certificate authority, kept in the certificate directory. Protocol 3.0 uses it to check the reflector.
+_Avoid_: the station certificate
+
+**Protocol**:
+The reflector session this station is speaking: 2.0 or 3.0.
+_Avoid_: TYPE, a config field the operator sets
 
 **Push-to-talk**:
 The operator holding the control that makes this station the talker. Releasing it returns the station to listening.

docs/adr/0004-ca-bundle-trust-on-first-use.md

@@ -0,0 +1,3 @@
+# Trust the first CA bundle
+
+Protocol 3.0 checks the reflector with the CA bundle in the certificate directory. When that file is missing, the station stores the bundle after the signature check with the certificate inside the same message. A later digest that differs from the stored file leaves the file in place. Replacing a stored bundle automatically was rejected because the reflector could swap the trust anchor.

docs/adr/0005-protocol-3-with-explicit-2-fallback.md

@@ -0,0 +1,3 @@
+# Announce protocol 3.0, fall back only on an explicit 2.x maximum
+
+Every TCP connection announces protocol 3.0. The station opens one 2.0 session only when the reflector sends a downgrade, or an unsupported-version error, whose maximum is at least 2.0 and below 3.0. The connection after that 2.0 session ends announces 3.0 again. A maximum whose major is below 2 stops the station with the reflector’s message. A reflector `MsgError` stops the station until the operator quits. A bad CA signature, a TLS or hostname failure, a heartbeat timeout, and a dropped connection retry on 3.0, and the window keeps the reason between attempts. The Protocol line shows 2.0 or 3.0 while the session is up, so a plaintext session is visible. Staying on 3.0 after every failure was rejected because a reflector that still expects 2.0 would never accept the station. Falling back on any handshake failure was rejected because a TLS or CA problem would then send plaintext audio.

frontend/dist/app.css

@@ -14,6 +14,11 @@ main {
   font-size: 14px;
 }
 
+#protocol {
+  min-height: 1.4em;
+  margin: 0;
+}
+
 #detail {
   min-height: 1.4em;
   font-size: 20px;

frontend/dist/app.js

@@ -21,6 +21,8 @@ function render(state) {
   document.getElementById("connection").textContent = state.connection;
   document.getElementById("callsign").textContent = state.callsign;
   document.getElementById("talkgroup").textContent = String(state.talkGroup);
+  const protocol = document.getElementById("protocol");
+  protocol.textContent = state.protocol ? "Protocol " + state.protocol : "";
   document.getElementById("detail").textContent = line(state);
   button.classList.toggle("down", !!state.transmitting);
 }

frontend/dist/index.html

@@ -10,6 +10,7 @@
     <p id="connection">Disconnected</p>
     <p>Callsign <span id="callsign"></span></p>
     <p>Talk group <span id="talkgroup"></span></p>
+    <p id="protocol"></p>
     <p id="detail">Idle</p>
     <button id="ptt" type="button">Push to talk</button>
   </main>

internal/gcm64/gcm.go

@@ -0,0 +1,63 @@
+// Package gcm64 seals and opens AES-GCM with the 8-byte tag this protocol uses.
+package gcm64
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/subtle"
+	"encoding/binary"
+	"errors"
+)
+
+// IV is the 12-byte nonce: a 6-byte prefix, the client id, and the counter.
+func IV(prefix []byte, clientID uint16, counter uint32) []byte {
+	iv := make([]byte, 12)
+	copy(iv, prefix)
+	binary.BigEndian.PutUint16(iv[6:8], clientID)
+	binary.BigEndian.PutUint32(iv[8:12], counter)
+	return iv
+}
+
+// Seal returns an 8-byte tag and the ciphertext. The tag is the leading 8
+// bytes of the ordinary 16-byte GCM tag, because crypto/cipher only builds
+// tags of 12 to 16 bytes.
+func Seal(key, nonce, plain, aad []byte) (tag, ct []byte, err error) {
+	g, err := full(key)
+	if err != nil {
+		return nil, nil, err
+	}
+	out := g.Seal(nil, nonce, plain, aad)
+	ct = append([]byte(nil), out[:len(plain)]...)
+	tag = append([]byte(nil), out[len(plain):len(plain)+8]...)
+	return tag, ct, nil
+}
+
+// Open checks the 8-byte tag and returns the plaintext.
+func Open(key, nonce, tag, ct, aad []byte) ([]byte, error) {
+	if len(tag) != 8 {
+		return nil, errors.New("tag")
+	}
+	g, err := full(key)
+	if err != nil {
+		return nil, err
+	}
+	stream := g.Seal(nil, nonce, make([]byte, len(ct)), aad)
+	plain := make([]byte, len(ct))
+	subtle.XORBytes(plain, ct, stream[:len(ct)])
+	check := g.Seal(nil, nonce, plain, aad)
+	var got, want [8]byte
+	copy(got[:], tag)
+	copy(want[:], check[len(plain):len(plain)+8])
+	if subtle.ConstantTimeCompare(got[:], want[:]) != 1 {
+		return nil, errors.New("tag")
+	}
+	return plain, nil
+}
+
+func full(key []byte) (cipher.AEAD, error) {
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewGCM(block)
+}

internal/opus/opus.go

@@ -5,6 +5,10 @@ package opus
 #cgo pkg-config: opus
 #include <opus.h>
 
+static void reset_decoder(OpusDecoder *dec) {
+	opus_decoder_ctl(dec, OPUS_RESET_STATE);
+}
+
 static int configure_encoder(OpusEncoder *enc) {
 	int err;
 	err = opus_encoder_ctl(enc, OPUS_SET_BITRATE(20000));
@@ -114,6 +118,14 @@ func (d *Decoder) Decode(packet []byte) ([]int16, error) {
 	return pcm, nil
 }
 
+// Reset clears decoder state after a gap in the received audio.
+func (d *Decoder) Reset() {
+	if d == nil || d.dec == nil {
+		return
+	}
+	C.reset_decoder(d.dec)
+}
+
 // Close releases the decoder.
 func (d *Decoder) Close() {
 	if d == nil || d.dec == nil {

main.go

@@ -25,7 +25,7 @@ func main() {
 	err = wails.Run(&options.App{
 		Title:            "funknetz",
 		Width:            420,
-		Height:           280,
+		Height:           320,
 		BackgroundColour: &options.RGBA{R: 16, G: 20, B: 24, A: 255},
 		AssetServer:      &assetserver.Options{Assets: assets},
 		OnStartup:        app.startup,

station/behavior_test.go

@@ -43,19 +43,18 @@ func loginLog(t *testing.T, callsign, key string, tg int, id uint16, codecs []st
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	t.Cleanup(cancel)
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 	refl.accept(t)
-
+	declineTo2(t, refl)
-	typ, body := refl.readFrame(t)
-	if typ != 5 || len(body) != 4 || body[1] != 2 {
-		t.Fatalf("protocol frame type %d body %v", typ, body)
-	}
 	challenge := make([]byte, 20)
 	for i := range challenge {
 		challenge[i] = byte(i + 1)
 	}
 	refl.writeFrame(t, 10, appendBytes(nil, challenge))
-	typ, body = refl.readFrame(t)
+	typ, body := refl.readFrame(t)
 	if typ != 11 {
 		t.Fatalf("auth type %d", typ)
 	}
@@ -88,12 +87,41 @@ func loginLog(t *testing.T, callsign, key string, tg int, id uint16, codecs []st
 	if utyp != 1 || gotID != id || seq != 0 || len(ubody) != 0 {
 		t.Fatalf("udp heartbeat type %d id %d seq %d len %d", utyp, gotID, seq, len(ubody))
 	}
-	if _, err := st.Wait(ctx, func(s station.State) bool { return s.Connection == "Connected" }); err != nil {
+	got, err := st.Wait(ctx, func(s station.State) bool { return s.Connection == "Connected" })
+	if err != nil {
 		t.Fatal(err)
 	}
+	if got.Protocol != "2.0" {
+		t.Fatalf("Protocol = %q, want 2.0", got.Protocol)
+	}
 	return loggedIn{st: st, clock: clock, refl: refl, cancel: cancel, id: id}
 }
 
+func declineTo2(t *testing.T, refl *reflector) {
+	t.Helper()
+	typ, body := refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 3, 0) {
+		t.Fatalf("first version type %d body %v, want 3.0", typ, body)
+	}
+	refl.writeFrame(t, 6, versionWire(2, 0))
+	refl.accept(t)
+	typ, body = refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 2, 0) {
+		t.Fatalf("fallback version type %d body %v, want 2.0", typ, body)
+	}
+}
+
+func versionWire(major, minor uint16) []byte {
+	return appendU16(appendU16(nil, major), minor)
+}
+
+func versionIs(body []byte, major, minor uint16) bool {
+	if len(body) != 4 {
+		return false
+	}
+	return binary.BigEndian.Uint16(body[0:2]) == major && binary.BigEndian.Uint16(body[2:4]) == minor
+}
+
 func TestQuietSessionSendsHeartbeats(t *testing.T) {
 	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
 
@@ -127,12 +155,15 @@ func TestDropRetriesUntilQuit(t *testing.T) {
 	}); err != nil {
 		t.Fatal(err)
 	}
+	if got := in.st.State(); got.Protocol != "" {
+		t.Fatalf("Protocol = %q, want blank while disconnected", got.Protocol)
+	}
 	in.clock.BlockUntilWaiting(t)
 	in.clock.Advance(2 * time.Second)
 	in.refl.accept(t)
 	typ, body := in.refl.readFrame(t)
-	if typ != 5 || body[1] != 2 {
+	if typ != 5 || !versionIs(body, 3, 0) {
-		t.Fatalf("retry protocol type %d body %v", typ, body)
+		t.Fatalf("retry protocol type %d body %v, want 3.0", typ, body)
 	}
 	in.cancel()
 	in.clock.Advance(2 * time.Second)
@@ -159,7 +190,10 @@ func TestRefusedConnectionRetriesUntilQuit(t *testing.T) {
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 
 	if _, err := st.Wait(ctx, func(s station.State) bool { return s.Connection == "Disconnected" }); err != nil {
 		t.Fatal(err)
@@ -204,7 +238,10 @@ func TestReflectorErrorStopsRetries(t *testing.T) {
 			}
 			ctx, cancel := context.WithCancel(t.Context())
 			defer cancel()
-			go func() { _ = st.Run(ctx) }()
+			go func() {
+				// Run's error is observed through State, which is the station seam.
+				_ = st.Run(ctx)
+			}()
 			refl.accept(t)
 			refl.readFrame(t)
 			refl.writeFrame(t, 13, appendStr(nil, msg))
@@ -238,9 +275,12 @@ func TestMissingOpusStopsRetries(t *testing.T) {
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 	refl.accept(t)
-	refl.readFrame(t)
+	declineTo2(t, refl)
 	challenge := make([]byte, 20)
 	refl.writeFrame(t, 10, appendBytes(nil, challenge))
 	refl.readFrame(t)
@@ -508,14 +548,15 @@ func expectAudio(t *testing.T, refl *reflector, dec *opus.Decoder, id, seq uint1
 }
 
 func tryFrame(r *reflector) (uint16, []byte, bool) {
-	_ = r.tcp.SetReadDeadline(time.Now().Add(30 * time.Millisecond))
+	conn := r.conn()
+	_ = conn.SetReadDeadline(time.Now().Add(30 * time.Millisecond))
 	var hdr [4]byte
-	if _, err := io.ReadFull(r.tcp, hdr[:]); err != nil {
+	if _, err := io.ReadFull(conn, hdr[:]); err != nil {
 		return 0, nil, false
 	}
 	n := binary.BigEndian.Uint32(hdr[:])
 	buf := make([]byte, n)
-	if _, err := io.ReadFull(r.tcp, buf); err != nil {
+	if _, err := io.ReadFull(conn, buf); err != nil {
 		return 0, nil, false
 	}
 	if len(buf) < 2 {

station/cert.go

@@ -0,0 +1,316 @@
+package station
+
+import (
+	"crypto"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/asn1"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+const (
+	caFileName   = "ca.pem"
+	keyFileName  = "key.pem"
+	csrFileName  = "csr.pem"
+	certFileName = "cert.pem"
+)
+
+var (
+	oidBasicConstraints = asn1.ObjectIdentifier{2, 5, 29, 19}
+	oidKeyUsage         = asn1.ObjectIdentifier{2, 5, 29, 15}
+	oidExtKeyUsage      = asn1.ObjectIdentifier{2, 5, 29, 37}
+	oidClientAuth       = asn1.ObjectIdentifier{1, 3, 6, 1, 5, 5, 7, 3, 2}
+)
+
+func ensureCertDir(path string) error {
+	err := os.Mkdir(path, 0o700)
+	if err != nil {
+		if !errors.Is(err, fs.ErrExist) {
+			return err
+		}
+		info, statErr := os.Stat(path)
+		if statErr != nil {
+			return statErr
+		}
+		if !info.IsDir() {
+			return err
+		}
+		return nil
+	}
+	return os.Chmod(path, 0o700)
+}
+
+func caDigest(dir string) (sum [32]byte, ok bool, err error) {
+	body, err := os.ReadFile(filepath.Join(dir, caFileName))
+	if errors.Is(err, fs.ErrNotExist) {
+		return sum, false, nil
+	}
+	if err != nil {
+		return sum, false, err
+	}
+	return sha256.Sum256(body), true, nil
+}
+
+func verifyCABundle(caPEM string, sig []byte, certPEM string) error {
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil {
+		return errors.New("signing certificate")
+	}
+	cert, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		return err
+	}
+	pub, ok := cert.PublicKey.(*rsa.PublicKey)
+	if !ok {
+		return errors.New("signing certificate")
+	}
+	sum := sha256.Sum256([]byte(caPEM))
+	return rsa.VerifyPKCS1v15(pub, crypto.SHA256, sum[:], sig)
+}
+
+func writeCABundle(dir, caPEM string) error {
+	return writeMode(filepath.Join(dir, caFileName), []byte(caPEM), 0o644)
+}
+
+func writeClientCert(dir, certPEM string) error {
+	return writeMode(filepath.Join(dir, certFileName), []byte(certPEM), 0o644)
+}
+
+func csrNewerThanCert(dir string) (bool, error) {
+	csrPath := filepath.Join(dir, csrFileName)
+	certPath := filepath.Join(dir, certFileName)
+	csr, err := os.Stat(csrPath)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return false, fmt.Errorf("stat %s: %w", csrPath, err)
+	}
+	if err != nil {
+		return false, nil
+	}
+	cert, err := os.Stat(certPath)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return false, fmt.Errorf("stat %s: %w", certPath, err)
+	}
+	if err != nil {
+		return false, nil
+	}
+	return csr.ModTime().After(cert.ModTime()), nil
+}
+
+func readCSR(dir string) (string, error) {
+	body, err := os.ReadFile(filepath.Join(dir, csrFileName))
+	if err != nil {
+		return "", err
+	}
+	return string(body), nil
+}
+
+// prepareIdentity checks a saved certificate or creates the key and signing
+// request. fatal is a window message when the station must stop.
+func prepareIdentity(dir, callsign string) (tls.Certificate, bool, string, error) {
+	certPath := filepath.Join(dir, certFileName)
+	keyPath := filepath.Join(dir, keyFileName)
+	_, certErr := os.Stat(certPath)
+	_, keyErr := os.Stat(keyPath)
+	certExists := certErr == nil
+	keyExists := keyErr == nil
+	if certErr != nil && !errors.Is(certErr, fs.ErrNotExist) {
+		return tls.Certificate{}, false, "Cannot create " + certPath, fmt.Errorf("stat certificate: %w", certErr)
+	}
+	if keyErr != nil && !errors.Is(keyErr, fs.ErrNotExist) {
+		return tls.Certificate{}, false, "Cannot create " + keyPath, fmt.Errorf("stat key: %w", keyErr)
+	}
+	if certExists && !keyExists {
+		return tls.Certificate{}, false, "Certificate key is missing", nil
+	}
+	if certExists && keyExists {
+		pair, msg, err := loadPair(certPath, keyPath, callsign)
+		if msg != "" {
+			return tls.Certificate{}, false, msg, err
+		}
+		if msg, err := ensureCSR(dir, callsign); msg != "" {
+			return tls.Certificate{}, false, msg, err
+		}
+		return pair, true, "", nil
+	}
+	if msg, err := ensureKeyAndCSR(dir, callsign, !keyExists); msg != "" {
+		return tls.Certificate{}, false, msg, err
+	}
+	return tls.Certificate{}, false, "", nil
+}
+
+func loadPair(certPath, keyPath, callsign string) (tls.Certificate, string, error) {
+	cert, err := loadCert(certPath)
+	if err != nil {
+		return tls.Certificate{}, "Cannot create " + certPath, fmt.Errorf("read certificate: %w", err)
+	}
+	key, err := loadKey(keyPath)
+	if err != nil {
+		return tls.Certificate{}, "Cannot create " + keyPath, fmt.Errorf("read key: %w", err)
+	}
+	pub, ok := cert.PublicKey.(*rsa.PublicKey)
+	if !ok || !pub.Equal(&key.PublicKey) {
+		return tls.Certificate{}, "Certificate does not match the key", nil
+	}
+	if cert.Subject.CommonName != callsign {
+		return tls.Certificate{}, "Certificate callsign does not match", nil
+	}
+	return tls.Certificate{
+		Certificate: [][]byte{cert.Raw},
+		PrivateKey:  key,
+		Leaf:        cert,
+	}, "", nil
+}
+
+func ensureCSR(dir, callsign string) (string, error) {
+	csrPath := filepath.Join(dir, csrFileName)
+	_, err := os.Stat(csrPath)
+	if err == nil {
+		return "", nil
+	}
+	if !errors.Is(err, fs.ErrNotExist) {
+		return "Cannot create " + csrPath, fmt.Errorf("stat signing request: %w", err)
+	}
+	key, err := loadKey(filepath.Join(dir, keyFileName))
+	if err != nil {
+		return "Cannot create " + csrPath, fmt.Errorf("read key: %w", err)
+	}
+	if err := writeCSR(csrPath, key, callsign); err != nil {
+		return "Cannot create " + csrPath, err
+	}
+	return "", nil
+}
+
+func ensureKeyAndCSR(dir, callsign string, created bool) (string, error) {
+	keyPath := filepath.Join(dir, keyFileName)
+	var key *rsa.PrivateKey
+	var err error
+	if created {
+		key, err = rsa.GenerateKey(rand.Reader, 2048)
+		if err != nil {
+			return "Cannot create " + keyPath, fmt.Errorf("generate key: %w", err)
+		}
+		der := x509.MarshalPKCS1PrivateKey(key)
+		body := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: der})
+		if err := writeNew(keyPath, body, 0o600); err != nil {
+			return "Cannot create " + keyPath, err
+		}
+	} else {
+		key, err = loadKey(keyPath)
+		if err != nil {
+			return "Cannot create " + keyPath, fmt.Errorf("read key: %w", err)
+		}
+	}
+	csrPath := filepath.Join(dir, csrFileName)
+	_, csrErr := os.Stat(csrPath)
+	if csrErr != nil && !errors.Is(csrErr, fs.ErrNotExist) {
+		return "Cannot create " + csrPath, fmt.Errorf("stat signing request: %w", csrErr)
+	}
+	if created || errors.Is(csrErr, fs.ErrNotExist) {
+		if err := writeCSR(csrPath, key, callsign); err != nil {
+			return "Cannot create " + csrPath, err
+		}
+	}
+	return "", nil
+}
+
+func writeCSR(path string, key *rsa.PrivateKey, callsign string) error {
+	bc, err := asn1.Marshal(struct {
+		CA bool
+	}{CA: false})
+	if err != nil {
+		return err
+	}
+	// digitalSignature, keyEncipherment, keyAgreement: bits 0, 2, and 4.
+	ku, err := asn1.Marshal(asn1.BitString{Bytes: []byte{0xA8}, BitLength: 5})
+	if err != nil {
+		return err
+	}
+	eku, err := asn1.Marshal([]asn1.ObjectIdentifier{oidClientAuth})
+	if err != nil {
+		return err
+	}
+	der, err := x509.CreateCertificateRequest(rand.Reader, &x509.CertificateRequest{
+		Subject: pkix.Name{CommonName: callsign},
+		ExtraExtensions: []pkix.Extension{
+			{Id: oidBasicConstraints, Critical: true, Value: bc},
+			{Id: oidKeyUsage, Critical: true, Value: ku},
+			{Id: oidExtKeyUsage, Critical: false, Value: eku},
+		},
+	}, key)
+	if err != nil {
+		return err
+	}
+	body := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE REQUEST", Bytes: der})
+	return writeMode(path, body, 0o644)
+}
+
+func loadCert(path string) (*x509.Certificate, error) {
+	body, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	block, _ := pem.Decode(body)
+	if block == nil {
+		return nil, errors.New("certificate")
+	}
+	return x509.ParseCertificate(block.Bytes)
+}
+
+func loadKey(path string) (*rsa.PrivateKey, error) {
+	body, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	block, _ := pem.Decode(body)
+	if block == nil {
+		return nil, errors.New("key")
+	}
+	switch block.Type {
+	case "RSA PRIVATE KEY":
+		return x509.ParsePKCS1PrivateKey(block.Bytes)
+	case "PRIVATE KEY":
+		k, err := x509.ParsePKCS8PrivateKey(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		rk, ok := k.(*rsa.PrivateKey)
+		if !ok {
+			return nil, errors.New("key")
+		}
+		return rk, nil
+	default:
+		return nil, errors.New("key")
+	}
+}
+
+func writeNew(path string, body []byte, mode os.FileMode) error {
+	f, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, mode)
+	if err != nil {
+		return err
+	}
+	_, werr := f.Write(body)
+	cerr := f.Close()
+	if werr != nil {
+		return werr
+	}
+	if cerr != nil {
+		return cerr
+	}
+	return os.Chmod(path, mode)
+}
+
+func writeMode(path string, body []byte, mode os.FileMode) error {
+	if err := os.WriteFile(path, body, mode); err != nil {
+		return err
+	}
+	return os.Chmod(path, mode)
+}

station/cipher.go

@@ -0,0 +1,33 @@
+package station
+
+import (
+	"encoding/binary"
+
+	"gitea.neitzel.de/konrad/funknetz/internal/gcm64"
+)
+
+func counterAAD(counter uint32) []byte {
+	var b [4]byte
+	binary.BigEndian.PutUint32(b[:], counter)
+	return b[:]
+}
+
+func registrationAAD(clientID uint16) []byte {
+	b := counterAAD(0)
+	return appendU16(b, clientID)
+}
+
+func sealDatagram(key, prefix []byte, clientID uint16, counter uint32, aad, plain []byte) ([]byte, error) {
+	tag, ct, err := gcm64.Seal(key, gcm64.IV(prefix, clientID, counter), plain, aad)
+	if err != nil {
+		return nil, err
+	}
+	wire := make([]byte, 0, len(aad)+len(tag)+len(ct))
+	wire = append(wire, aad...)
+	wire = append(wire, tag...)
+	return append(wire, ct...), nil
+}
+
+func openDatagram(key, prefix []byte, clientID uint16, counter uint32, aad, tag, ct []byte) ([]byte, error) {
+	return gcm64.Open(key, gcm64.IV(prefix, clientID, counter), tag, ct, aad)
+}

station/config.go

@@ -15,34 +15,38 @@ import (
 )
 
 type loaded struct {
-	host          string
+	host           string
-	port          int
+	port           int
-	callsign      string
+	callsign       string
-	authKey       string
+	authKey        string
-	talkGroup     int
+	talkGroup      int
-	enableLogging bool
+	certificateDir string
-	logPath       string
+	certFatal      string
-	logNotice     string
+	enableLogging  bool
+	logPath        string
+	logNotice      string
 }
 
 type fileShape struct {
-	Host          jsontext.Value `json:"host"`
+	Host           jsontext.Value `json:"host"`
-	Port          jsontext.Value `json:"port"`
+	Port           jsontext.Value `json:"port"`
-	Callsign      jsontext.Value `json:"callsign"`
+	Callsign       jsontext.Value `json:"callsign"`
-	AuthKey       jsontext.Value `json:"authKey"`
+	AuthKey        jsontext.Value `json:"authKey"`
-	TalkGroup     jsontext.Value `json:"talkGroup"`
+	TalkGroup      jsontext.Value `json:"talkGroup"`
-	EnableLogging jsontext.Value `json:"enableLogging"`
+	CertificateDir jsontext.Value `json:"certificateDir"`
-	LogFile       jsontext.Value `json:"logFile"`
+	EnableLogging  jsontext.Value `json:"enableLogging"`
+	LogFile        jsontext.Value `json:"logFile"`
 }
 
 type templateFile struct {
-	Host          string `json:"host"`
+	Host           string `json:"host"`
-	Port          int    `json:"port"`
+	Port           int    `json:"port"`
-	Callsign      string `json:"callsign"`
+	Callsign       string `json:"callsign"`
-	AuthKey       string `json:"authKey"`
+	AuthKey        string `json:"authKey"`
-	TalkGroup     int    `json:"talkGroup"`
+	TalkGroup      int    `json:"talkGroup"`
-	EnableLogging bool   `json:"enableLogging"`
+	CertificateDir string `json:"certificateDir"`
-	LogFile       string `json:"logFile"`
+	EnableLogging  bool   `json:"enableLogging"`
+	LogFile        string `json:"logFile"`
 }
 
 var callsignPattern = regexp.MustCompile(`^[A-Z0-9][A-Z]{0,2}\d[A-Z0-9]{0,3}[A-Z](?:-[A-Z0-9]{1,3})?$`)
@@ -66,7 +70,7 @@ func writeTemplate(path string) error {
 	if err != nil {
 		return err
 	}
-	body, err := jsonv2.Marshal(templateFile{LogFile: logFile})
+	body, err := jsonv2.Marshal(templateFile{CertificateDir: "./funknetz", LogFile: logFile})
 	if err != nil {
 		return err
 	}
@@ -91,15 +95,19 @@ func parseConfig(path string, body []byte) (loaded, error) {
 	if err := jsonv2.Unmarshal(body, &shape); err != nil {
 		return loaded{}, fmt.Errorf("the file could not be read: %w", err)
 	}
-	if block, notice := blockedLog(shape); block {
+	certBad := present(shape.CertificateDir) && shape.CertificateDir.Kind() != jsontext.KindString
+	if block, notice := blockedLog(shape); block || certBad {
 		cfg, err := parseOperational(shape)
 		if err != nil {
 			return loaded{}, err
 		}
 		cfg.logNotice = notice
-		return cfg, nil
+		if !block {
+			cfg = applyLog(cfg, shape)
+		}
+		return applyCertificate(cfg, shape, path), nil
 	}
-	if missingLog(shape) {
+	if missingCertificate(shape) || missingLog(shape) {
 		if !operationalKindsOK(shape) {
 			return parseOperational(shape)
 		}
@@ -116,7 +124,7 @@ func parseConfig(path string, body []byte) (loaded, error) {
 	if err != nil {
 		return loaded{}, err
 	}
-	return applyLog(cfg, shape), nil
+	return applyLog(applyCertificate(cfg, shape, path), shape), nil
 }
 
 func parseOperational(shape fileShape) (loaded, error) {
@@ -217,6 +225,10 @@ func missingLog(shape fileShape) bool {
 	return !present(shape.EnableLogging) || !present(shape.LogFile)
 }
 
+func missingCertificate(shape fileShape) bool {
+	return !present(shape.CertificateDir)
+}
+
 func operationalKindsOK(shape fileShape) bool {
 	if present(shape.Host) && shape.Host.Kind() != jsontext.KindString {
 		return false
@@ -259,6 +271,7 @@ func withLogDefaults(shape fileShape) (fileShape, error) {
 	shape.Callsign = rawOr(shape.Callsign, `""`)
 	shape.AuthKey = rawOr(shape.AuthKey, `""`)
 	shape.TalkGroup = rawOr(shape.TalkGroup, "0")
+	shape.CertificateDir = rawOr(shape.CertificateDir, `"./funknetz"`)
 	shape.EnableLogging = rawOr(shape.EnableLogging, "false")
 	if !present(shape.LogFile) {
 		logFile, err := defaultLogPath()
@@ -316,6 +329,32 @@ func rewriteConfig(path string, shape fileShape) error {
 	return nil
 }
 
+func applyCertificate(cfg loaded, shape fileShape, configPath string) loaded {
+	if !present(shape.CertificateDir) {
+		cfg.certificateDir = resolveCertDir(configPath, "./funknetz")
+		return cfg
+	}
+	dir, err := stringField("certificateDir", shape.CertificateDir)
+	if err != nil {
+		cfg.certFatal = err.Error()
+		return cfg
+	}
+	if strings.TrimSpace(dir) == "" {
+		cfg.certFatal = "certificateDir is empty"
+		return cfg
+	}
+	cfg.certificateDir = resolveCertDir(configPath, dir)
+	return cfg
+}
+
+func resolveCertDir(configPath, dir string) string {
+	dir = strings.TrimSpace(dir)
+	if filepath.IsAbs(dir) {
+		return filepath.Clean(dir)
+	}
+	return filepath.Clean(filepath.Join(filepath.Dir(configPath), dir))
+}
+
 func applyLog(cfg loaded, shape fileShape) loaded {
 	if shape.EnableLogging.Kind() != jsontext.KindTrue {
 		return cfg

station/config_test.go

@@ -1,10 +1,14 @@
 package station_test
 
 import (
+	"context"
+	"fmt"
+	"net"
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
+	"time"
 
 	jsonv2 "encoding/json/v2"
 
@@ -54,11 +58,15 @@ func TestMissingConfigIsCreatedAndRejected(t *testing.T) {
 	if got["logFile"] != filepath.Join(home, "funknetz.log") {
 		t.Fatalf("logFile = %#v, want funknetz.log in the home directory", got["logFile"])
 	}
+	if got["certificateDir"] != "./funknetz" {
+		t.Fatalf("certificateDir = %#v, want ./funknetz", got["certificateDir"])
+	}
+	assertKeyOrder(t, body)
 }
 
 func TestExistingConfigIsNotRewritten(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "funknetz.json")
-	original := []byte("{\"host\":\"127.0.0.1\",\"port\":5308,\"callsign\":\"DL1ABC\",\"authKey\":\"a b\",\"talkGroup\":20,\"enableLogging\":false,\"logFile\":\"/tmp/funknetz.log\"}\n")
+	original := []byte("{\"host\":\"127.0.0.1\",\"port\":5308,\"callsign\":\"DL1ABC\",\"authKey\":\"a b\",\"talkGroup\":20,\"certificateDir\":\"/var/funknetz\",\"enableLogging\":false,\"logFile\":\"/tmp/funknetz.log\"}\n")
 	if err := os.WriteFile(path, original, 0o640); err != nil {
 		t.Fatal(err)
 	}
@@ -240,6 +248,10 @@ func TestMissingLogKeysAreRewritten(t *testing.T) {
 	if got["logFile"] != filepath.Join(home, "funknetz.log") {
 		t.Fatalf("logFile = %#v", got["logFile"])
 	}
+	if got["certificateDir"] != "./funknetz" {
+		t.Fatalf("certificateDir = %#v, want ./funknetz", got["certificateDir"])
+	}
+	assertKeyOrder(t, body)
 	if st.State().Detail != "Idle" {
 		t.Fatalf("Detail = %q, want Idle", st.State().Detail)
 	}
@@ -314,9 +326,9 @@ func TestLogSettingsDoNotStopTheStation(t *testing.T) {
 		detail string
 		same   bool
 	}{
-		{name: "relative", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":true,"logFile":"funknetz.log"}`, detail: "Cannot write funknetz.log", same: true},
+		{name: "relative", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"certificateDir":"./funknetz","enableLogging":true,"logFile":"funknetz.log"}`, detail: "Cannot write funknetz.log", same: true},
-		{name: "empty", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":true,"logFile":"  "}`, detail: "Cannot write logFile", same: true},
+		{name: "empty", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"certificateDir":"./funknetz","enableLogging":true,"logFile":"  "}`, detail: "Cannot write logFile", same: true},
-		{name: "tilde", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":true,"logFile":"~/funknetz.log"}`, detail: "Cannot write ~/funknetz.log", same: true},
+		{name: "tilde", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"certificateDir":"./funknetz","enableLogging":true,"logFile":"~/funknetz.log"}`, detail: "Cannot write ~/funknetz.log", same: true},
 		{name: "enable type", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":"yes","logFile":"/tmp/funknetz.log"}`, detail: "enableLogging has the wrong type", same: true},
 		{name: "file type", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":true,"logFile":1}`, detail: "logFile has the wrong type", same: true},
 		{name: "both types", body: `{"host":"127.0.0.1","port":5308,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"enableLogging":"yes","logFile":1}`, detail: "enableLogging has the wrong type", same: true},
@@ -368,6 +380,106 @@ func TestLogSettingsDoNotStopTheStation(t *testing.T) {
 	})
 }
 
+func assertKeyOrder(t *testing.T, body []byte) {
+	t.Helper()
+	keys := []string{`"host"`, `"port"`, `"callsign"`, `"authKey"`, `"talkGroup"`, `"certificateDir"`, `"enableLogging"`, `"logFile"`}
+	last := -1
+	for _, key := range keys {
+		i := strings.Index(string(body), key)
+		if i < 0 || i < last {
+			t.Fatalf("key %s out of order in %s", key, body)
+		}
+		last = i
+	}
+}
+
+func TestMissingCertificateDirIsWrittenAfterTalkGroup(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "funknetz.json")
+	original := []byte("{\"host\":\"127.0.0.1\",\"port\":5308,\"callsign\":\"DL1ABC\",\"authKey\":\"a b\",\"talkGroup\":20,\"enableLogging\":false,\"logFile\":\"/tmp/funknetz.log\"}\n")
+	if err := os.WriteFile(path, original, 0o640); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := station.New(station.Options{ConfigPath: path}); err != nil {
+		t.Fatal(err)
+	}
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := info.Mode().Perm(), os.FileMode(0o640); got != want {
+		t.Fatalf("mode = %o, want %o", got, want)
+	}
+	body, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var got map[string]any
+	if err := jsonv2.Unmarshal(body, &got); err != nil {
+		t.Fatal(err)
+	}
+	if got["authKey"] != "a b" || got["callsign"] != "DL1ABC" || got["certificateDir"] != "./funknetz" {
+		t.Fatalf("fields = %#v", got)
+	}
+	if strings.Contains(string(body), t.TempDir()) {
+		t.Fatalf("file = %s, want the stored directory to stay relative", body)
+	}
+	assertKeyOrder(t, body)
+}
+
+func TestCertificateDirStopsBeforeASocket(t *testing.T) {
+	tests := []struct {
+		name string
+		dir  string
+		want string
+	}{
+		{name: "wrong type", dir: "1", want: "certificateDir has the wrong type"},
+		{name: "empty", dir: `""`, want: "certificateDir is empty"},
+		{name: "whitespace", dir: `"  "`, want: "certificateDir is empty"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ln, err := net.Listen("tcp", "127.0.0.1:0")
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer ln.Close()
+			port := ln.Addr().(*net.TCPAddr).Port
+			body := fmt.Sprintf(`{"host":"127.0.0.1","port":%d,"callsign":"DL1ABC","authKey":"key","talkGroup":20,"certificateDir":%s,"enableLogging":false,"logFile":"/tmp/funknetz.log"}`, port, tt.dir)
+			path := filepath.Join(t.TempDir(), "funknetz.json")
+			if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
+				t.Fatal(err)
+			}
+			st, err := station.New(station.Options{ConfigPath: path})
+			if err != nil {
+				t.Fatal(err)
+			}
+			t.Cleanup(st.Close)
+			got := st.State()
+			if got.Detail != tt.want || got.Connection != "Disconnected" || got.Callsign != "DL1ABC" {
+				t.Fatalf("State = %+v, want detail %q", got, tt.want)
+			}
+			after, err := os.ReadFile(path)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if string(after) != body {
+				t.Fatalf("file = %s, want it left untouched", after)
+			}
+			ctx, cancel := context.WithCancel(t.Context())
+			defer cancel()
+			go func() {
+				// Run's error is observed through State, which is the station seam.
+				_ = st.Run(ctx)
+			}()
+			ln.(*net.TCPListener).SetDeadline(time.Now().Add(200 * time.Millisecond))
+			if conn, err := ln.Accept(); err == nil {
+				conn.Close()
+				t.Fatal("opened a socket")
+			}
+		})
+	}
+}
+
 func configJSON(t testing.TB, host string, port int, callsign, authKey string, talkGroup int) string {
 	t.Helper()
 	body, err := jsonv2.Marshal(map[string]any{

station/lab_reflector_test.go

@@ -2,9 +2,11 @@ package station_test
 
 import (
 	"context"
+	"errors"
 	"net"
 	"os"
 	"strconv"
+	"syscall"
 	"testing"
 	"time"
 
@@ -30,6 +32,9 @@ func TestConnectsToLabReflector(t *testing.T) {
 		t.Skipf("lab reflector not listening on %s: %v", addr, err)
 	}
 	conn.Close()
+	if !labUDPReachable() {
+		t.Skipf("lab UDP port %s is not reachable", addr)
+	}
 
 	path := writeConfigFile(t, configJSON(t, labHost, labPort, labCallsign, labAuthKey, labTalkGroup))
 	st, err := station.New(station.Options{ConfigPath: path})
@@ -39,7 +44,10 @@ func TestConnectsToLabReflector(t *testing.T) {
 
 	ctx, cancel := context.WithTimeout(t.Context(), 15*time.Second)
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 
 	state, err := st.Wait(ctx, func(s station.State) bool {
 		return s.Connection == "Connected"
@@ -54,3 +62,20 @@ func TestConnectsToLabReflector(t *testing.T) {
 		t.Fatalf("talkGroup = %d, want %d", state.TalkGroup, labTalkGroup)
 	}
 }
+
+func labUDPReachable() bool {
+	peer := &net.UDPAddr{IP: net.ParseIP(labHost), Port: labPort}
+	conn, err := net.DialUDP("udp", nil, peer)
+	if err != nil {
+		return false
+	}
+	defer conn.Close()
+	_, _ = conn.Write([]byte{0})
+	_ = conn.SetReadDeadline(time.Now().Add(200 * time.Millisecond))
+	_, err = conn.Read(make([]byte, 1))
+	if err == nil {
+		return true
+	}
+	var op *net.OpError
+	return !errors.As(err, &op) || !errors.Is(op.Err, syscall.ECONNREFUSED)
+}

station/log.go

@@ -93,6 +93,10 @@ func (s *Station) noteDownLocked(now time.Time, dial bool) {
 }
 
 func (s *Station) endFatal(msg string, log bool) {
+	s.endFatalCause(msg, nil, log)
+}
+
+func (s *Station) endFatalCause(msg string, cause error, log bool) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	if s.fatal != "" {
@@ -107,7 +111,11 @@ func (s *Station) endFatal(msg string, log bool) {
 	if log {
 		s.up = false
 		s.outage = true
-		s.writeLog(now, oneLine(msg))
+		line := oneLine(msg)
+		if cause != nil {
+			line += ": " + oneLine(cause.Error())
+		}
+		s.writeLog(now, line)
 	}
 	s.publish()
 }

station/log_test.go

@@ -131,7 +131,10 @@ func TestFirstDialFailureIsLoggedOnce(t *testing.T) {
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 
 	want := "2026-10-03T12:00:00Z disconnected\n"
 	deadline := time.Now().Add(2 * time.Second)
@@ -160,7 +163,10 @@ func TestReflectorErrorsAreOneLogLine(t *testing.T) {
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 	refl.accept(t)
 	refl.readFrame(t)
 	refl.writeFrame(t, 13, appendStr(nil, "bad\nline"))

station/protocol.go

@@ -4,26 +4,47 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"regexp"
+	"strconv"
 )
 
 const (
 	tcpHeartbeat     = 1
 	tcpProtoVer      = 5
+	tcpProtoDown     = 6
 	tcpAuthChallenge = 10
 	tcpAuthResponse  = 11
 	tcpAuthOK        = 12
 	tcpError         = 13
+	tcpStartEncReq   = 14
+	tcpStartEnc      = 15
+	tcpCsrReq        = 16
+	tcpCsr           = 17
+	tcpClientCert    = 18
+	tcpCAInfo        = 19
+	tcpCABundleReq   = 20
+	tcpCABundle      = 21
 	tcpServerInfo    = 100
+	tcpNodeList      = 101
+	tcpNodeJoined    = 102
+	tcpNodeLeft      = 103
 	tcpTalkerStart   = 104
 	tcpTalkerStop    = 105
 	tcpSelectTG      = 106
+	tcpRequestQSY    = 109
+	tcpStateEvent    = 110
 	tcpNodeInfo      = 111
+	tcpSignal        = 112
+	tcpTxStatus      = 113
+	tcpStartUDPEnc   = 114
 
-	udpHeartbeat = 1
+	udpHeartbeat  = 1
-	udpAudio     = 101
+	udpAudio      = 101
-	udpFlush     = 102
+	udpFlush      = 102
+	udpAllFlushed = 103
 
-	maxFrame = 32768
+	maxFrame     = 32768
+	maxPreauth20 = 64
 )
 
 type frame struct {
@@ -45,12 +66,16 @@ func writeFrame(w io.Writer, typ uint16, body []byte) error {
 }
 
 func readFrame(r io.Reader) (frame, error) {
+	return readFrameMax(r, maxFrame)
+}
+
+func readFrameMax(r io.Reader, max uint32) (frame, error) {
 	var hdr [4]byte
 	if _, err := io.ReadFull(r, hdr[:]); err != nil {
 		return frame{}, err
 	}
 	n := binary.BigEndian.Uint32(hdr[:])
-	if n < 2 || n > maxFrame {
+	if n < 2 || n > max {
 		return frame{}, fmt.Errorf("frame length %d", n)
 	}
 	buf := make([]byte, n)
@@ -149,6 +174,48 @@ func parseServerInfo(b []byte) (uint16, []string, error) {
 	return id, codecs, nil
 }
 
+func versionWire(major, minor uint16) []byte {
+	return appendU16(appendU16(nil, major), minor)
+}
+
+func parseVersion(b []byte) (uint16, uint16, error) {
+	major, rest, err := parseU16(b)
+	if err != nil {
+		return 0, 0, err
+	}
+	minor, rest, err := parseU16(rest)
+	if err != nil {
+		return 0, 0, err
+	}
+	if len(rest) != 0 {
+		return 0, 0, io.ErrUnexpectedEOF
+	}
+	return major, minor, nil
+}
+
+var atMostVersion = regexp.MustCompile(`^Unsupported protocol version \d+\.\d+\. May be at most (\d+)\.(\d+)\.$`)
+
+// fallback20 reports that the reflector's maximum is at least 2.0 and below 3.0.
+func fallback20(msg string) bool {
+	m := atMostVersion.FindStringSubmatch(msg)
+	if m == nil {
+		return false
+	}
+	major, err1 := strconv.Atoi(m[1])
+	minor, err2 := strconv.Atoi(m[2])
+	if err1 != nil || err2 != nil {
+		return false
+	}
+	return !versionBelow(major, minor, 2, 0) && versionBelow(major, minor, 3, 0)
+}
+
+func versionBelow(major, minor, maj, min int) bool {
+	if major != maj {
+		return major < maj
+	}
+	return minor < min
+}
+
 func hasOPUS(codecs []string) bool {
 	for _, c := range codecs {
 		if c == "OPUS" {

station/protocol2_test.go

@@ -0,0 +1,244 @@
+package station_test
+
+import (
+	"context"
+	"encoding/binary"
+	"testing"
+	"time"
+
+	"gitea.neitzel.de/konrad/funknetz/internal/opus"
+	"gitea.neitzel.de/konrad/funknetz/station"
+)
+
+func TestProtocol2DropsASequenceTooFarBehind(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	enc, err := opus.NewEncoder()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer enc.Close()
+	pkt, err := enc.Encode(make([]int16, opus.FrameSamples))
+	if err != nil {
+		t.Fatal(err)
+	}
+	in.refl.writeUDP(t, 101, 7, 32768, appendBytes(nil, pkt))
+	in.refl.writeUDP(t, 101, 7, 4, appendBytes(nil, pkt))
+	if _, err := in.st.WaitPlayback(t.Context(), opus.FrameSamples); err != nil {
+		t.Fatal(err)
+	}
+	if extra := in.st.TakePlayback(); len(extra) != 0 {
+		t.Fatalf("played %d extra samples from the old sequence", len(extra))
+	}
+}
+
+func TestProtocol2FlushCompletesOnce(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	in.st.HoldButton()
+	in.st.ReleaseButton()
+	typ, id, _, body := in.refl.readUDP(t)
+	if typ != 102 || id != 7 || len(body) != 0 {
+		t.Fatalf("flush type %d id %d len %d", typ, id, len(body))
+	}
+	in.refl.writeUDP(t, 103, 7, 0, nil)
+	in.clock.BlockUntilWaiting(t)
+	in.clock.Advance(3 * time.Second)
+	if pkt, _, ok := tryUDP(in.refl); ok {
+		t.Fatalf("sent %d bytes after flush-complete", len(pkt))
+	}
+	if got := in.st.State(); got.Connection != "Connected" || got.Protocol != "2.0" {
+		t.Fatalf("State = %+v", got)
+	}
+}
+
+func TestProtocol2FlushTimesOutWithoutASecondFlush(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	in.st.HoldButton()
+	in.st.ReleaseButton()
+	typ, _, _, _ := in.refl.readUDP(t)
+	if typ != 102 {
+		t.Fatalf("type %d, want flush", typ)
+	}
+	in.clock.BlockUntilWaiting(t)
+	in.clock.Advance(3 * time.Second)
+	if pkt, _, ok := tryUDP(in.refl); ok {
+		t.Fatalf("sent %d bytes when flush-complete did not arrive", len(pkt))
+	}
+}
+
+func TestSilenceFreesPushToTalkAndKeepsTheTalker(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	enc, err := opus.NewEncoder()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer enc.Close()
+	pkt, err := enc.Encode(make([]int16, opus.FrameSamples))
+	if err != nil {
+		t.Fatal(err)
+	}
+	in.refl.writeUDP(t, 101, 7, 0, appendBytes(nil, pkt))
+	if _, err := in.st.WaitPlayback(t.Context(), opus.FrameSamples); err != nil {
+		t.Fatal(err)
+	}
+	in.refl.writeFrame(t, 104, appendStr(appendU32(nil, 20), "DB0XYZ"))
+	if _, err := in.st.Wait(t.Context(), func(s station.State) bool { return s.Talker == "DB0XYZ" }); err != nil {
+		t.Fatal(err)
+	}
+	in.clock.BlockUntilWaiting(t)
+	in.clock.Advance(3 * time.Second)
+	in.st.HoldButton()
+	in.st.WriteMicrophone(make([]int16, opus.FrameSamples))
+	if _, _, ok := tryUDP(in.refl); ok {
+		t.Fatal("push-to-talk sent audio at exactly 3 seconds")
+	}
+	in.st.ReleaseButton()
+	in.clock.BlockUntilWaiting(t)
+	gen := in.clock.Generation()
+	in.clock.Advance(time.Second)
+	waitClock(t, in.clock, gen)
+	if got := in.st.State(); got.Talker != "DB0XYZ" || got.Transmitting {
+		t.Fatalf("State = %+v, want the talker kept and the button free", got)
+	}
+	in.st.HoldButton()
+	if !in.st.State().Transmitting {
+		t.Fatal("push-to-talk stayed blocked after the gap")
+	}
+	in.st.WriteMicrophone(make([]int16, opus.FrameSamples))
+	utyp, id, _, _ := in.refl.readUDP(t)
+	if utyp != 101 || id != 7 {
+		t.Fatalf("audio type %d id %d", utyp, id)
+	}
+}
+
+func TestUDPLimitRunsBeforeAnyDatagram(t *testing.T) {
+	refl := newReflector(t)
+	path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+	clock := newFakeClock()
+	st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithCancel(t.Context())
+	defer cancel()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
+	refl.accept(t)
+	declineTo2(t, refl)
+	for step := 0; step < 6; step++ {
+		clock.BlockUntilWaiting(t)
+		clock.Advance(10 * time.Second)
+		if st.State().Connection == "Disconnected" && step < 5 {
+			t.Fatalf("dropped on step %d", step)
+		}
+		replyTCP(t, refl)
+	}
+	if _, err := st.Wait(t.Context(), func(s station.State) bool { return s.Connection == "Disconnected" }); err != nil {
+		t.Fatal(err)
+	}
+	if got := st.State().Detail; got != "udp receive timeout" {
+		t.Fatalf("Detail = %q, want udp receive timeout", got)
+	}
+	clock.BlockUntilWaiting(t)
+	clock.Advance(2 * time.Second)
+	refl.accept(t)
+	typ, body := refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 3, 0) {
+		t.Fatalf("retry type %d body %v, want 3.0", typ, body)
+	}
+}
+
+func TestOversizedFrameBeforeAuthRetries(t *testing.T) {
+	refl := newReflector(t)
+	path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+	clock := newFakeClock()
+	st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithCancel(t.Context())
+	defer cancel()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
+	refl.accept(t)
+	declineTo2(t, refl)
+	payload := make([]byte, 65)
+	var hdr [4]byte
+	binary.BigEndian.PutUint32(hdr[:], 65)
+	if _, err := refl.tcp.Write(append(hdr[:], payload...)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := st.Wait(ctx, func(s station.State) bool { return s.Connection == "Disconnected" }); err != nil {
+		t.Fatal(err)
+	}
+	clock.BlockUntilWaiting(t)
+	clock.Advance(2 * time.Second)
+	refl.accept(t)
+	typ, body := refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 3, 0) {
+		t.Fatalf("retry type %d body %v, want 3.0", typ, body)
+	}
+}
+
+func TestApplicationMessageBeforeLoginRetries(t *testing.T) {
+	refl := newReflector(t)
+	path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+	clock := newFakeClock()
+	st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithCancel(t.Context())
+	defer cancel()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
+	refl.accept(t)
+	declineTo2(t, refl)
+	refl.writeFrame(t, 100, serverInfo(1, nil, []string{"OPUS"}))
+	got, err := st.Wait(t.Context(), func(s station.State) bool { return s.Detail == "Protocol error" })
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Connection != "Disconnected" || got.Protocol != "" {
+		t.Fatalf("State = %+v", got)
+	}
+	clock.BlockUntilWaiting(t)
+	clock.Advance(2 * time.Second)
+	refl.accept(t)
+	typ, body := refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 3, 0) {
+		t.Fatalf("retry type %d body %v", typ, body)
+	}
+	if st.State().Detail != "Protocol error" {
+		t.Fatalf("Detail = %q, want the reason kept", st.State().Detail)
+	}
+}
+
+func TestIgnoredNoticesDoNotChangeTheStation(t *testing.T) {
+	in := login(t, "DL1ABC", "key", 20, 7, []string{"OPUS"})
+	in.refl.writeFrame(t, 101, appendStr(appendU16(nil, 1), "DB0XYZ"))
+	in.refl.writeFrame(t, 102, appendStr(nil, "DB0XYZ"))
+	in.refl.writeFrame(t, 103, appendStr(nil, "DB0XYZ"))
+	in.refl.writeFrame(t, 109, appendU32(nil, 99))
+	body := appendStr(nil, "src")
+	body = appendStr(body, "name")
+	body = appendStr(body, "msg")
+	in.refl.writeFrame(t, 110, body)
+	in.refl.writeFrame(t, 112, append(appendU16(nil, 1), []byte{1, 40, 1}...))
+	in.refl.writeFrame(t, 113, append(appendU16(nil, 1), []byte{1, 1}...))
+	in.clock.BlockUntilWaiting(t)
+	in.clock.Advance(10 * time.Second)
+	typ, _ := in.refl.readFrame(t)
+	if typ != 1 {
+		t.Fatalf("TCP type %d, want a heartbeat", typ)
+	}
+	got := in.st.State()
+	if got.Connection != "Connected" || got.Protocol != "2.0" || got.TalkGroup != 20 || got.Talker != "" {
+		t.Fatalf("State = %+v", got)
+	}
+}

station/protocol_select_test.go

@@ -0,0 +1,152 @@
+package station_test
+
+import (
+	"context"
+	"net"
+	"os"
+	"testing"
+	"time"
+
+	"gitea.neitzel.de/konrad/funknetz/station"
+)
+
+func TestVersionErrorFallsBackWhenTheMaximumIs2(t *testing.T) {
+	for _, msg := range []string{
+		"Unsupported protocol version 3.0. May be at most 2.0.",
+		"Unsupported protocol version 3.0. May be at most 2.5.",
+	} {
+		t.Run(msg, func(t *testing.T) {
+			refl := newReflector(t)
+			path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+			clock := newFakeClock()
+			st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithCancel(t.Context())
+			defer cancel()
+			go func() {
+				// Run's error is observed through State, which is the station seam.
+				_ = st.Run(ctx)
+			}()
+			refl.accept(t)
+			typ, body := refl.readFrame(t)
+			if typ != 5 || !versionIs(body, 3, 0) {
+				t.Fatalf("type %d body %v", typ, body)
+			}
+			refl.writeFrame(t, 13, appendStr(nil, msg))
+			refl.accept(t)
+			typ, body = refl.readFrame(t)
+			if typ != 5 || !versionIs(body, 2, 0) {
+				t.Fatalf("fallback type %d body %v", typ, body)
+			}
+		})
+	}
+}
+
+func TestVersionErrorBelow2Stops(t *testing.T) {
+	for _, msg := range []string{
+		"Unsupported protocol version 3.0. May be at most 1.9.",
+		"Unsupported protocol version 3.0. May be at most 0.6.",
+	} {
+		t.Run(msg, func(t *testing.T) {
+			refl := newReflector(t)
+			path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+			clock := newFakeClock()
+			st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithCancel(t.Context())
+			defer cancel()
+			go func() {
+				// Run's error is observed through State, which is the station seam.
+				_ = st.Run(ctx)
+			}()
+			refl.accept(t)
+			refl.readFrame(t)
+			refl.writeFrame(t, 13, appendStr(nil, msg))
+			got, err := st.Wait(ctx, func(s station.State) bool { return s.Detail == msg })
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got.Connection != "Disconnected" || got.Protocol != "" {
+				t.Fatalf("State = %+v", got)
+			}
+			clock.Advance(2 * time.Second)
+			refl.ln.(*net.TCPListener).SetDeadline(time.Now().Add(150 * time.Millisecond))
+			if conn, err := refl.ln.Accept(); err == nil {
+				conn.Close()
+				t.Fatal("retried")
+			}
+		})
+	}
+}
+
+func TestDowngradeOtherThan2Stops(t *testing.T) {
+	for _, tc := range []struct {
+		major, minor uint16
+		want         string
+	}{
+		{1, 0, "Unsupported protocol version 1.0"},
+		{4, 2, "Unsupported protocol version 4.2"},
+	} {
+		t.Run(tc.want, func(t *testing.T) {
+			refl := newReflector(t)
+			path := writeConfigFile(t, configJSON(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20))
+			clock := newFakeClock()
+			st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+			if err != nil {
+				t.Fatal(err)
+			}
+			ctx, cancel := context.WithCancel(t.Context())
+			defer cancel()
+			go func() {
+				// Run's error is observed through State, which is the station seam.
+				_ = st.Run(ctx)
+			}()
+			refl.accept(t)
+			refl.readFrame(t)
+			refl.writeFrame(t, 6, versionWire(tc.major, tc.minor))
+			got, err := st.Wait(ctx, func(s station.State) bool { return s.Detail == tc.want })
+			if err != nil {
+				t.Fatal(err)
+			}
+			if got.Protocol != "" || got.Connection != "Disconnected" {
+				t.Fatalf("State = %+v", got)
+			}
+			clock.Advance(2 * time.Second)
+			refl.ln.(*net.TCPListener).SetDeadline(time.Now().Add(150 * time.Millisecond))
+			if conn, err := refl.ln.Accept(); err == nil {
+				conn.Close()
+				t.Fatal("retried")
+			}
+		})
+	}
+}
+
+func TestDowngradeDoesNotCreateTheCertificateDirectory(t *testing.T) {
+	refl := newReflector(t)
+	dir := t.TempDir()
+	path := dir + "/funknetz.json"
+	body := configWithDir(t, "127.0.0.1", refl.port, "DL1ABC", "key", 20, "./funknetz", "")
+	if err := os.WriteFile(path, []byte(body), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	clock := newFakeClock()
+	st, err := station.New(station.Options{ConfigPath: path, Clock: clock})
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithCancel(t.Context())
+	defer cancel()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
+	refl.accept(t)
+	declineTo2(t, refl)
+	if _, err := os.Stat(dir + "/funknetz"); err == nil {
+		t.Fatal("created the certificate directory on a 2.0 fallback")
+	}
+}

station/reflector_test.go

@@ -1,6 +1,7 @@
 package station_test
 
 import (
+	"crypto/tls"
 	"encoding/binary"
 	"encoding/json"
 	"io"
@@ -133,21 +134,39 @@ type reflector struct {
 	ln   net.Listener
 	udp  *net.UDPConn
 	tcp  net.Conn
+	tls  *tls.Conn
 	peer *net.UDPAddr
 	port int
 }
 
+func (r *reflector) conn() net.Conn {
+	if r.tls != nil {
+		return r.tls
+	}
+	return r.tcp
+}
+
 func newReflector(t *testing.T) *reflector {
 	t.Helper()
-	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	var ln net.Listener
-	if err != nil {
+	var udp *net.UDPConn
-		t.Fatal(err)
+	var port int
-	}
+	for range 8 {
-	port := ln.Addr().(*net.TCPAddr).Port
+		var err error
-	udp, err := net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: port})
+		ln, err = net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
+		if err != nil {
+			t.Fatal(err)
+		}
+		port = ln.Addr().(*net.TCPAddr).Port
+		udp, err = net.ListenUDP("udp", &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: port})
+		if err == nil {
+			break
+		}
 		ln.Close()
-		t.Fatal(err)
+		ln = nil
+	}
+	if udp == nil {
+		t.Fatal("udp port stayed in use")
 	}
 	t.Cleanup(func() {
 		if ln != nil {
@@ -166,16 +185,18 @@ func (r *reflector) accept(t *testing.T) {
 		t.Fatal(err)
 	}
 	r.tcp = conn
+	r.tls = nil
 	t.Cleanup(func() { conn.Close() })
 }
 
 func (r *reflector) readFrame(t *testing.T) (uint16, []byte) {
 	t.Helper()
-	if err := r.tcp.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
+	conn := r.conn()
+	if err := conn.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
 		t.Fatal(err)
 	}
 	var hdr [4]byte
-	if _, err := io.ReadFull(r.tcp, hdr[:]); err != nil {
+	if _, err := io.ReadFull(conn, hdr[:]); err != nil {
 		t.Fatal(err)
 	}
 	n := binary.BigEndian.Uint32(hdr[:])
@@ -183,7 +204,7 @@ func (r *reflector) readFrame(t *testing.T) (uint16, []byte) {
 		t.Fatalf("frame length %d", n)
 	}
 	buf := make([]byte, n)
-	if _, err := io.ReadFull(r.tcp, buf); err != nil {
+	if _, err := io.ReadFull(conn, buf); err != nil {
 		t.Fatal(err)
 	}
 	if len(buf) < 2 {
@@ -199,14 +220,30 @@ func (r *reflector) writeFrame(t *testing.T, typ uint16, body []byte) {
 	copy(payload[2:], body)
 	var hdr [4]byte
 	binary.BigEndian.PutUint32(hdr[:], uint32(len(payload)))
-	if err := r.tcp.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
+	conn := r.conn()
+	if err := conn.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
 		t.Fatal(err)
 	}
-	if _, err := r.tcp.Write(append(hdr[:], payload...)); err != nil {
+	if _, err := conn.Write(append(hdr[:], payload...)); err != nil {
 		t.Fatal(err)
 	}
 }
 
+func (r *reflector) handshake(t *testing.T, cfg *tls.Config) error {
+	t.Helper()
+	r.tls = tls.Server(r.tcp, cfg)
+	if err := r.tls.SetDeadline(time.Now().Add(2 * time.Second)); err != nil {
+		return err
+	}
+	err := r.tls.Handshake()
+	// Clearing the deadline is best-effort; the handshake error is the result.
+	_ = r.tls.SetDeadline(time.Time{})
+	if err != nil {
+		r.tls = nil
+	}
+	return err
+}
+
 func (r *reflector) readUDP(t *testing.T) (typ, id, seq uint16, body []byte) {
 	t.Helper()
 	if err := r.udp.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
@@ -228,6 +265,33 @@ func (r *reflector) readUDP(t *testing.T) (typ, id, seq uint16, body []byte) {
 	return typ, id, seq, body
 }
 
+func (r *reflector) readRawUDP(t *testing.T) []byte {
+	t.Helper()
+	if err := r.udp.SetReadDeadline(time.Now().Add(2 * time.Second)); err != nil {
+		t.Fatal(err)
+	}
+	buf := make([]byte, 2048)
+	n, addr, err := r.udp.ReadFromUDP(buf)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r.peer = addr
+	return append([]byte(nil), buf[:n]...)
+}
+
+func (r *reflector) writeRawUDP(t *testing.T, pkt []byte) {
+	t.Helper()
+	if r.peer == nil {
+		t.Fatal("no udp peer")
+	}
+	if err := r.udp.SetWriteDeadline(time.Now().Add(2 * time.Second)); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := r.udp.WriteToUDP(pkt, r.peer); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func (r *reflector) writeUDP(t *testing.T, typ, id, seq uint16, body []byte) {
 	t.Helper()
 	if r.peer == nil {
@@ -294,8 +358,11 @@ func requireSoftwareIdentity(t *testing.T, body []byte) {
 	if err := json.Unmarshal([]byte(raw), &got); err != nil {
 		t.Fatalf("software identity %q: %v", raw, err)
 	}
-	if len(got) != 2 || got["sw"] != station.SoftwareName || got["swVer"] != station.SoftwareVersion {
+	if len(got) != 3 || got["sw"] != station.SoftwareName || got["swVer"] != station.SoftwareVersion || got["projVer"] != station.SoftwareVersion {
-		t.Fatalf("software identity = %#v, want sw %q and swVer %q only", got, station.SoftwareName, station.SoftwareVersion)
+		t.Fatalf("software identity = %#v, want sw, swVer, and projVer %q", got, station.SoftwareName)
+	}
+	if _, ok := got["machineArch"]; ok {
+		t.Fatal("protocol 2.0 node information includes machineArch")
 	}
 }
 

station/session.go

@@ -4,11 +4,16 @@ import (
 	"context"
 	"crypto/hmac"
 	"crypto/sha1"
+	"crypto/tls"
 	"encoding/binary"
 	"errors"
+	"fmt"
+	"io"
 	"net"
 	"strconv"
+	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"gitea.neitzel.de/konrad/funknetz/internal/opus"
@@ -16,11 +21,16 @@ import (
 
 const noOpus = "The reflector did not offer OPUS."
 
-var errStopped = errors.New("session stopped")
+var (
+	errStopped   = errors.New("session stopped")
+	errFallback  = errors.New("fallback")
+	errReconnect = errors.New("reconnect")
+)
 
 // Run keeps the reflector session until ctx is canceled.
 func (s *Station) Run(ctx context.Context) error {
 	defer s.Close()
+	major := uint16(3)
 	for {
 		if ctx.Err() != nil {
 			return nil
@@ -41,6 +51,7 @@ func (s *Station) Run(ctx context.Context) error {
 			if ctx.Err() != nil {
 				return nil
 			}
+			major = 3
 			s.mu.Lock()
 			s.noteDownLocked(s.clock.Now(), true)
 			s.mu.Unlock()
@@ -50,12 +61,30 @@ func (s *Station) Run(ctx context.Context) error {
 			continue
 		}
 
-		err = s.session(ctx, conn)
+		err = s.session(ctx, conn, major)
 		conn.Close()
+		fallback := errors.Is(err, errFallback)
+		reconnect := errors.Is(err, errReconnect)
 		s.mu.Lock()
 		s.closeUDP()
 		s.mic = nil
 		s.play = nil
+		s.audioHeard = false
+		s.flushWaiting = false
+		if fallback || reconnect {
+			s.roomBusy = false
+			s.remoteTalker = ""
+			s.mu.Unlock()
+			if ctx.Err() != nil {
+				return nil
+			}
+			if fallback {
+				major = 2
+			} else {
+				major = 3
+			}
+			continue
+		}
 		if s.fatal == "" {
 			s.noteDownLocked(s.clock.Now(), false)
 		} else {
@@ -63,14 +92,11 @@ func (s *Station) Run(ctx context.Context) error {
 		}
 		fatal := s.fatal != ""
 		s.mu.Unlock()
+		major = 3
 		if ctx.Err() != nil {
 			return nil
 		}
-		if fatal {
+		if fatal || errors.Is(err, errStopped) {
-			<-ctx.Done()
-			return nil
-		}
-		if err != nil && errors.Is(err, errStopped) {
 			<-ctx.Done()
 			return nil
 		}
@@ -97,7 +123,147 @@ func (s *Station) wait(ctx context.Context, d time.Duration) bool {
 	}
 }
 
-func (s *Station) session(ctx context.Context, conn net.Conn) error {
+type framed struct {
+	conn      net.Conn
+	mu        sync.Mutex
+	w         io.Writer
+	frames    chan frame
+	errs      chan error
+	upgrade   chan *tls.Config
+	handshake chan error
+	max       atomic.Uint32
+}
+
+// exchange is the state one TCP session's frame handlers share.
+type exchange struct {
+	ph       phase
+	authed   bool
+	client   tls.Certificate
+	haveCert bool
+	done     chan struct{}
+	udpCh    chan []byte
+	udpErr   chan error
+	udpReady bool
+	lastTCP  time.Time
+	limit    time.Time
+}
+
+func newFramed(conn net.Conn, max uint32) *framed {
+	f := &framed{
+		conn:      conn,
+		w:         conn,
+		frames:    make(chan frame, 8),
+		errs:      make(chan error, 1),
+		upgrade:   make(chan *tls.Config, 1),
+		handshake: make(chan error, 1),
+	}
+	f.max.Store(max)
+	return f
+}
+
+func (f *framed) Write(p []byte) (int, error) {
+	f.mu.Lock()
+	w := f.w
+	f.mu.Unlock()
+	return w.Write(p)
+}
+
+func (f *framed) setMax(n uint32) { f.max.Store(n) }
+
+var errTLSTimeout = errors.New("tls timeout")
+
+func (s *Station) startTLS(ctx context.Context, f *framed, cfg *tls.Config, until time.Time) error {
+	select {
+	case f.upgrade <- cfg:
+	case <-ctx.Done():
+		return ctx.Err()
+	}
+	if err := f.conn.SetReadDeadline(time.Now()); err != nil {
+		return err
+	}
+	wait := until.Sub(s.clock.Now())
+	if wait < 0 {
+		wait = 0
+	}
+	timer := s.clock.NewTimer(wait)
+	defer timer.Stop()
+	select {
+	case err := <-f.handshake:
+		return err
+	case <-ctx.Done():
+		if err := f.conn.SetDeadline(time.Now()); err != nil {
+			return err
+		}
+		return ctx.Err()
+	case <-timer.C():
+		if err := f.conn.SetDeadline(time.Now()); err != nil {
+			return err
+		}
+		select {
+		case <-f.handshake:
+		case <-ctx.Done():
+		}
+		return errTLSTimeout
+	}
+}
+
+func (f *framed) read(done <-chan struct{}) {
+	src := io.Reader(f.conn)
+	for {
+		fr, err := readFrameMax(src, f.max.Load())
+		if err != nil {
+			if ne, ok := errors.AsType[net.Error](err); ok && ne.Timeout() {
+				select {
+				case cfg := <-f.upgrade:
+					if derr := f.conn.SetReadDeadline(time.Time{}); derr != nil {
+						f.handshake <- derr
+						return
+					}
+					tc := tls.Client(f.conn, cfg)
+					herr := tc.Handshake()
+					if herr != nil {
+						f.handshake <- herr
+						return
+					}
+					f.mu.Lock()
+					f.w = tc
+					f.mu.Unlock()
+					src = tc
+					f.handshake <- nil
+					continue
+				case <-done:
+					return
+				}
+			}
+			select {
+			case f.errs <- err:
+			case <-done:
+			}
+			return
+		}
+		select {
+		case f.frames <- fr:
+		case <-done:
+			return
+		}
+	}
+}
+
+type phase int
+
+const (
+	phCA phase = iota
+	phBundle
+	phStart
+	phIdent
+	phServer
+	phUDP
+	phBeat
+	phRun
+	phChallenge
+)
+
+func (s *Station) session(ctx context.Context, conn net.Conn, major uint16) error {
 	done := make(chan struct{})
 	var closeOnce sync.Once
 	closeConn := func() { closeOnce.Do(func() { conn.Close() }) }
@@ -110,38 +276,56 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 		}
 	}()
 
-	tcpCh := make(chan frame, 8)
+	frameMax := uint32(maxFrame)
-	tcpErr := make(chan error, 1)
+	ex := &exchange{ph: phCA, done: done, lastTCP: s.clock.Now()}
-	go readTCP(conn, tcpCh, tcpErr, done)
+	label := "3.0"
+	if major < 3 {
+		frameMax = maxPreauth20
+		ex.ph = phChallenge
+		label = "2.0"
+	}
+	wire := newFramed(conn, frameMax)
+	go wire.read(done)
+	s.mu.Lock()
+	s.protocol = label
+	s.rxSeq = 0
+	s.rxCounter = 0
+	s.txCounter = 1
+	s.secure = false
+	s.udpWait = false
+	s.seq = 0
+	s.ivPrefix = nil
+	s.udpKey = nil
+	s.mu.Unlock()
 
-	if err := writeFrame(conn, tcpProtoVer, []byte{0, 2, 0, 0}); err != nil {
+	if err := writeFrame(wire, tcpProtoVer, versionWire(major, 0)); err != nil {
 		return err
 	}
-	lastTCP := s.clock.Now()
+	now := ex.lastTCP
-	tcpRx := lastTCP.Add(15 * time.Second)
+	tcpRx := now.Add(15 * time.Second)
-
+	udpRx := now.Add(60 * time.Second)
-	var udpCh chan []byte
-	var udpErr chan error
-	udpReady := false
-	var udpRx time.Time
 
 	for {
 		s.mu.Lock()
 		lastUDP := s.lastUDPSend
+		silence, silenceOK := s.nextSilence()
 		s.mu.Unlock()
 
-		next := lastTCP.Add(10 * time.Second)
+		next := ex.lastTCP.Add(10 * time.Second)
-		if tcpRx.Before(next) {
+		if t := tcpRx; t.Before(next) {
-			next = tcpRx
+			next = t
 		}
-		if udpReady {
+		if t := udpRx; t.Before(next) {
-			if u := lastUDP.Add(15 * time.Second); u.Before(next) {
+			next = t
-				next = u
+		}
-			}
+		if ex.udpReady {
-			if udpRx.Before(next) {
+			if t := lastUDP.Add(15 * time.Second); t.Before(next) {
-				next = udpRx
+				next = t
 			}
 		}
+		if silenceOK && silence.Before(next) {
+			next = silence
+		}
 		wait := next.Sub(s.clock.Now())
 		if wait < 0 {
 			wait = 0
@@ -150,9 +334,9 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 
 		var udpRecv <-chan []byte
 		var udpFail <-chan error
-		if udpCh != nil {
+		if ex.udpCh != nil {
-			udpRecv = udpCh
+			udpRecv = ex.udpCh
-			udpFail = udpErr
+			udpFail = ex.udpErr
 		}
 
 		var reason string
@@ -162,13 +346,13 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 		case <-ctx.Done():
 			timer.Stop()
 			return ctx.Err()
-		case err := <-tcpErr:
+		case err := <-wire.errs:
 			timer.Stop()
 			return err
 		case err := <-udpFail:
 			timer.Stop()
 			return err
-		case tcpf = <-tcpCh:
+		case tcpf = <-wire.frames:
 			timer.Stop()
 			reason = "tcp"
 		case udpp = <-udpRecv:
@@ -176,7 +360,7 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 			reason = "udp"
 		case <-timer.C():
 			select {
-			case tcpf = <-tcpCh:
+			case tcpf = <-wire.frames:
 				reason = "tcp"
 			default:
 				select {
@@ -188,36 +372,47 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 			}
 		}
 
-		now := s.clock.Now()
+		now = s.clock.Now()
 		switch reason {
 		case "tcp":
 			tcpRx = now.Add(15 * time.Second)
-			if err := s.onTCP(conn, tcpf, done, &udpCh, &udpErr, &udpReady, &udpRx, &lastTCP); err != nil {
+			ex.limit = tcpRx
+			if udpRx.Before(ex.limit) {
+				ex.limit = udpRx
+			}
+			err := s.onFrame(ctx, wire, major, tcpf, ex)
+			if err != nil {
 				return err
 			}
 		case "udp":
-			s.mu.Lock()
+			if err := s.onUDP(wire, udpp, ex, &udpRx, now); err != nil {
-			if clientIDOf(udpp) == s.clientID {
+				return err
-				udpRx = now.Add(60 * time.Second)
-				s.onDatagram(udpp)
 			}
-			s.mu.Unlock()
 		default:
+			s.mu.Lock()
+			s.onClock(now)
+			s.mu.Unlock()
 			if !now.Before(tcpRx) {
-				return errors.New("tcp receive timeout")
+				return s.retry("tcp receive timeout", nil)
 			}
-			if udpReady && !now.Before(udpRx) {
+			if !now.Before(udpRx) {
-				return errors.New("udp receive timeout")
+				return s.retry("udp receive timeout", nil)
 			}
-			if !now.Before(lastTCP.Add(10 * time.Second)) {
+			if !now.Before(ex.lastTCP.Add(10 * time.Second)) {
-				if err := writeFrame(conn, tcpHeartbeat, nil); err != nil {
+				if err := writeFrame(wire, tcpHeartbeat, nil); err != nil {
 					return err
 				}
-				lastTCP = s.clock.Now()
+				ex.lastTCP = s.clock.Now()
 			}
 			s.mu.Lock()
-			if udpReady && s.udp != nil && !s.clock.Now().Before(s.lastUDPSend.Add(15*time.Second)) {
+			if ex.udpReady && s.udp != nil && !s.clock.Now().Before(s.lastUDPSend.Add(15*time.Second)) {
-				if err := s.sendUDP(udpHeartbeat, nil); err != nil {
+				var err error
+				if s.udpWait {
+					err = s.sendRegistration()
+				} else {
+					err = s.sendUDP(udpHeartbeat, nil)
+				}
+				if err != nil {
 					s.mu.Unlock()
 					return err
 				}
@@ -227,127 +422,172 @@ func (s *Station) session(ctx context.Context, conn net.Conn) error {
 	}
 }
 
-func readTCP(conn net.Conn, out chan<- frame, errc chan<- error, done <-chan struct{}) {
+func (s *Station) retry(detail string, cause error) error {
-	for {
+	s.mu.Lock()
-		f, err := readFrame(conn)
+	s.retryReason = detail
-		if err != nil {
+	s.mu.Unlock()
-			select {
+	text := strings.ToLower(detail)
-			case errc <- err:
+	if cause == nil {
-			case <-done:
+		return errors.New(text)
-			}
+	}
-			return
+	return fmt.Errorf("%s: %w", text, cause)
+}
+
+func (s *Station) nextSilence() (time.Time, bool) {
+	var next time.Time
+	ok := false
+	if s.audioHeard {
+		next = s.lastAudio.Add(3*time.Second + time.Nanosecond)
+		ok = true
+	}
+	if s.flushWaiting {
+		at := s.flushAt.Add(3 * time.Second)
+		if !ok || at.Before(next) {
+			next = at
+			ok = true
 		}
-		select {
+	}
-		case out <- f:
+	return next, ok
-		case <-done:
+}
-			return
+
+func (s *Station) onClock(now time.Time) {
+	if s.flushWaiting && !now.Before(s.flushAt.Add(3*time.Second)) {
+		s.flushWaiting = false
+	}
+	if s.audioHeard && now.After(s.lastAudio.Add(3*time.Second)) {
+		if s.dec != nil {
+			s.dec.Reset()
 		}
+		s.audioHeard = false
+		s.roomBusy = false
+		s.publish()
 	}
 }
 
-func readUDP(conn *net.UDPConn, out chan<- []byte, errc chan<- error, done <-chan struct{}) {
+func (s *Station) onFrame(ctx context.Context, wire *framed, major uint16, f frame, ex *exchange) error {
-	buf := make([]byte, 2048)
-	for {
-		n, err := conn.Read(buf)
-		if err != nil {
-			select {
-			case errc <- err:
-			case <-done:
-			}
-			return
-		}
-		pkt := append([]byte(nil), buf[:n]...)
-		select {
-		case out <- pkt:
-		case <-done:
-			return
-		}
-	}
-}
-
-func (s *Station) onTCP(conn net.Conn, f frame, done <-chan struct{}, udpCh *chan []byte, udpErr *chan error, udpReady *bool, udpRx *time.Time, lastTCP *time.Time) error {
 	switch f.typ {
-	case tcpHeartbeat, tcpAuthOK:
+	case tcpHeartbeat:
-		return nil
-	case tcpAuthChallenge:
-		chal, _, err := parseBlob(f.body)
-		if err != nil || len(chal) != 20 {
-			return errors.New("bad challenge")
-		}
-		mac := hmac.New(sha1.New, []byte(s.cfg.authKey))
-		mac.Write(chal)
-		body := appendString(nil, s.cfg.callsign)
-		body = appendBlob(body, mac.Sum(nil))
-		if err := writeFrame(conn, tcpAuthResponse, body); err != nil {
-			return err
-		}
-		*lastTCP = s.clock.Now()
 		return nil
 	case tcpError:
-		msg, _, err := parseString(f.body)
+		return s.onReflectorError(f.body, major)
-		if err != nil {
+	case tcpProtoDown:
-			msg = "could not be read"
+		return s.onDowngrade(f.body, major)
-		}
+	}
-		s.endFatal(msg, true)
+	if !ex.authed && f.typ >= 100 {
-		return errStopped
+		return s.retry("Protocol error", nil)
+	}
+	if major < 3 {
+		return s.onV2(wire, f, ex)
+	}
+	return s.onV3(ctx, wire, f, ex)
+}
+
+func (s *Station) onReflectorError(body []byte, major uint16) error {
+	msg, _, err := parseString(body)
+	if err != nil {
+		s.endFatalCause("could not be read", err, true)
+		return fmt.Errorf("could not be read: %w", err)
+	}
+	if major >= 3 && fallback20(msg) {
+		return errFallback
+	}
+	s.endFatal(msg, true)
+	return errStopped
+}
+
+func (s *Station) onDowngrade(body []byte, major uint16) error {
+	gotMajor, gotMinor, err := parseVersion(body)
+	if err != nil {
+		return err
+	}
+	if major >= 3 && gotMajor == 2 {
+		return errFallback
+	}
+	s.endFatal("Unsupported protocol version "+strconvU(gotMajor)+"."+strconvU(gotMinor), true)
+	return errStopped
+}
+
+func strconvU(v uint16) string {
+	return strconv.FormatUint(uint64(v), 10)
+}
+
+func (s *Station) onV2(wire *framed, f frame, ex *exchange) error {
+	switch f.typ {
+	case tcpAuthOK:
+		ex.authed = true
+		ex.ph = phServer
+		wire.setMax(maxFrame)
+		return nil
+	case tcpAuthChallenge:
+		return s.answerChallenge(wire, f.body, ex)
 	case tcpServerInfo:
-		return s.onServerInfo(conn, f.body, done, udpCh, udpErr, udpReady, udpRx, lastTCP)
+		if ex.ph != phServer {
+			return s.retry("Protocol error", nil)
+		}
+		return s.finishV2(wire, f.body, ex)
 	case tcpTalkerStart:
 		s.onTalker(f.body, true)
 		return nil
 	case tcpTalkerStop:
 		s.onTalker(f.body, false)
 		return nil
+	case tcpNodeList, tcpNodeJoined, tcpNodeLeft, tcpRequestQSY, tcpStateEvent, tcpSignal, tcpTxStatus:
+		if err := unpackIgnored(f); err != nil {
+			return s.retry("Protocol error", err)
+		}
+		return nil
 	default:
 		return nil
 	}
 }
 
-func (s *Station) onServerInfo(conn net.Conn, body []byte, done <-chan struct{}, udpCh *chan []byte, udpErr *chan error, udpReady *bool, udpRx *time.Time, lastTCP *time.Time) error {
+func (s *Station) answerChallenge(w io.Writer, body []byte, ex *exchange) error {
-	id, codecs, err := parseServerInfo(body)
+	chal, _, err := parseBlob(body)
+	if err != nil {
+		return fmt.Errorf("bad challenge: %w", err)
+	}
+	if len(chal) != 20 {
+		return errors.New("bad challenge")
+	}
+	mac := hmac.New(sha1.New, []byte(s.cfg.authKey))
+	mac.Write(chal)
+	out := appendString(nil, s.cfg.callsign)
+	out = appendBlob(out, mac.Sum(nil))
+	if err := writeFrame(w, tcpAuthResponse, out); err != nil {
+		return err
+	}
+	ex.lastTCP = s.clock.Now()
+	return nil
+}
+
+func (s *Station) finishV2(wire *framed, body []byte, ex *exchange) error {
+	id, enc, dec, err := s.acceptServer(body)
 	if err != nil {
 		return err
 	}
-	if !hasOPUS(codecs) {
+	if enc == nil {
-		s.endFatal(noOpus, true)
 		return errStopped
 	}
-	enc, err := opus.NewEncoder()
-	if err != nil {
-		return err
-	}
-	dec, err := opus.NewDecoder()
-	if err != nil {
-		enc.Close()
-		return err
-	}
 	info, err := softwareIdentityBody()
 	if err != nil {
 		enc.Close()
 		dec.Close()
 		return err
 	}
-	if err := writeFrame(conn, tcpNodeInfo, info); err != nil {
+	if err := writeFrame(wire, tcpNodeInfo, info); err != nil {
 		enc.Close()
 		dec.Close()
 		return err
 	}
 	var tg [4]byte
 	binary.BigEndian.PutUint32(tg[:], uint32(s.cfg.talkGroup))
-	if err := writeFrame(conn, tcpSelectTG, tg[:]); err != nil {
+	if err := writeFrame(wire, tcpSelectTG, tg[:]); err != nil {
 		enc.Close()
 		dec.Close()
 		return err
 	}
-	*lastTCP = s.clock.Now()
+	ex.lastTCP = s.clock.Now()
-
+	udpConn, peer, err := dialAudio(wire.conn)
-	remote, ok := conn.RemoteAddr().(*net.TCPAddr)
-	if !ok {
-		enc.Close()
-		dec.Close()
-		return errors.New("tcp peer has no address")
-	}
-	udpConn, err := net.DialUDP("udp", nil, &net.UDPAddr{IP: remote.IP, Port: remote.Port})
 	if err != nil {
 		enc.Close()
 		dec.Close()
@@ -355,14 +595,16 @@ func (s *Station) onServerInfo(conn net.Conn, body []byte, done <-chan struct{},
 	}
 	ch := make(chan []byte, 32)
 	errc := make(chan error, 1)
-	go readUDP(udpConn, ch, errc, done)
+	go readUDP(udpConn, peer, ch, errc, ex.done)
-
 	s.mu.Lock()
 	s.clientID = id
+	s.udpPeer = peer
 	s.seq = 0
+	s.rxSeq = 0
 	s.udp = udpConn
 	s.enc = enc
 	s.dec = dec
+	s.secure = false
 	err = s.sendUDP(udpHeartbeat, nil)
 	if err != nil {
 		s.mu.Unlock()
@@ -378,14 +620,33 @@ func (s *Station) onServerInfo(conn net.Conn, body []byte, done <-chan struct{},
 	s.writeLog(s.clock.Now(), "connected")
 	s.publish()
 	s.mu.Unlock()
-
+	ex.udpCh = ch
-	*udpCh = ch
+	ex.udpErr = errc
-	*udpErr = errc
+	ex.udpReady = true
-	*udpReady = true
-	*udpRx = s.clock.Now().Add(60 * time.Second)
 	return nil
 }
 
+func (s *Station) acceptServer(body []byte) (uint16, *opus.Encoder, *opus.Decoder, error) {
+	id, codecs, err := parseServerInfo(body)
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	if !hasOPUS(codecs) {
+		s.endFatal(noOpus, true)
+		return 0, nil, nil, errStopped
+	}
+	enc, err := opus.NewEncoder()
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	dec, err := opus.NewDecoder()
+	if err != nil {
+		enc.Close()
+		return 0, nil, nil, err
+	}
+	return id, enc, dec, nil
+}
+
 func (s *Station) stop(msg string) { s.endFatal(msg, false) }
 
 // Fail stops retries and shows message until the operator quits.
@@ -425,69 +686,21 @@ func (s *Station) onTalker(body []byte, start bool) {
 	s.publish()
 }
 
-func (s *Station) onDatagram(pkt []byte) {
-	if len(pkt) < 6 {
-		return
-	}
-	typ := binary.BigEndian.Uint16(pkt[:2])
-	if typ != udpAudio || s.dec == nil {
-		return
-	}
-	if s.transmitting() {
-		return
-	}
-	packet, _, err := parseBlob(pkt[6:])
-	if err != nil {
-		return
-	}
-	pcm, err := s.dec.Decode(packet)
-	if err != nil {
-		return
-	}
-	s.play = append(s.play, pcm...)
-	s.roomBusy = true
-	s.publish()
-}
-
-func clientIDOf(pkt []byte) uint16 {
-	if len(pkt) < 6 {
-		return ^uint16(0)
-	}
-	return binary.BigEndian.Uint16(pkt[2:4])
-}
-
-func (s *Station) sendUDP(typ uint16, body []byte) error {
-	if s.udp == nil {
-		return errors.New("udp is down")
-	}
-	buf := make([]byte, 6+len(body))
-	binary.BigEndian.PutUint16(buf[0:2], typ)
-	binary.BigEndian.PutUint16(buf[2:4], s.clientID)
-	binary.BigEndian.PutUint16(buf[4:6], s.seq)
-	s.seq++
-	copy(buf[6:], body)
-	if _, err := s.udp.Write(buf); err != nil {
-		return err
-	}
-	s.lastUDPSend = s.clock.Now()
-	return nil
-}
-
 func (s *Station) endTransmit() {
 	if s.enc != nil && s.udp != nil && len(s.mic) > 0 {
 		frame := make([]int16, opus.FrameSamples)
 		copy(frame, s.mic)
 		s.mic = nil
 		if pkt, err := s.enc.Encode(frame); err == nil {
-			// A lost datagram ends the session when the receive timer expires.
 			_ = s.sendUDP(udpAudio, appendBlob(nil, pkt))
 		}
 	} else {
 		s.mic = nil
 	}
 	if s.udp != nil {
-		// A lost datagram ends the session when the receive timer expires.
 		_ = s.sendUDP(udpFlush, nil)
+		s.flushWaiting = true
+		s.flushAt = s.clock.Now()
 	}
 }
 
@@ -496,6 +709,7 @@ func (s *Station) closeUDP() {
 		s.udp.Close()
 		s.udp = nil
 	}
+	s.udpPeer = nil
 	if s.enc != nil {
 		s.enc.Close()
 		s.enc = nil
@@ -522,8 +736,8 @@ func (s *Station) publish() {
 		s.state.Detail = s.fatal
 		s.state.Talker = ""
 		s.state.Transmitting = false
+		s.state.Protocol = ""
 	} else {
-		s.state.Detail = "Idle"
 		tx := s.transmitting()
 		s.state.Transmitting = tx
 		if tx {
@@ -532,8 +746,22 @@ func (s *Station) publish() {
 		} else {
 			s.state.Talker = s.remoteTalker
 		}
-		if s.state.Talker == "" && s.logNotice != "" {
+		if s.state.Connection == "Connected" {
-			s.state.Detail = s.logNotice
+			s.state.Protocol = s.protocol
+			s.retryReason = ""
+			s.state.Detail = "Idle"
+			if s.state.Talker == "" && s.logNotice != "" {
+				s.state.Detail = s.logNotice
+			}
+		} else {
+			s.state.Protocol = ""
+			if s.retryReason != "" {
+				s.state.Detail = s.retryReason
+			} else if s.state.Talker == "" && s.logNotice != "" {
+				s.state.Detail = s.logNotice
+			} else {
+				s.state.Detail = "Idle"
+			}
 		}
 	}
 	select {
@@ -541,3 +769,45 @@ func (s *Station) publish() {
 	default:
 	}
 }
+
+func unpackIgnored(f frame) error {
+	switch f.typ {
+	case tcpNodeList:
+		_, _, err := parseStringList(f.body)
+		return err
+	case tcpNodeJoined, tcpNodeLeft:
+		_, _, err := parseString(f.body)
+		return err
+	case tcpRequestQSY:
+		_, _, err := parseU32(f.body)
+		return err
+	case tcpStateEvent:
+		_, rest, err := parseString(f.body)
+		if err != nil {
+			return err
+		}
+		_, rest, err = parseString(rest)
+		if err != nil {
+			return err
+		}
+		_, _, err = parseString(rest)
+		return err
+	case tcpSignal:
+		return unpackRecords(f.body, 3)
+	case tcpTxStatus:
+		return unpackRecords(f.body, 2)
+	default:
+		return nil
+	}
+}
+
+func unpackRecords(b []byte, size int) error {
+	n, rest, err := parseU16(b)
+	if err != nil {
+		return err
+	}
+	if len(rest) != int(n)*size {
+		return io.ErrUnexpectedEOF
+	}
+	return nil
+}

station/session_test.go

@@ -21,20 +21,29 @@ func TestLoginAnnouncesProtocolAndJoinsTheTalkGroup(t *testing.T) {
 	}
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
-	go func() { _ = st.Run(ctx) }()
+	go func() {
+		// Run's error is observed through State, which is the station seam.
+		_ = st.Run(ctx)
+	}()
 
 	got, err := st.Wait(ctx, func(s station.State) bool { return s.Connection == "Connecting" })
 	if err != nil {
 		t.Fatal(err)
 	}
-	if got.Callsign != "DL1ABC" || got.TalkGroup != 20 || got.Detail != "Idle" {
+	if got.Callsign != "DL1ABC" || got.TalkGroup != 20 || got.Detail != "Idle" || got.Protocol != "" {
-		t.Fatalf("State = %+v, want DL1ABC talk group 20 Idle", got)
+		t.Fatalf("State = %+v, want DL1ABC talk group 20 Idle and a blank protocol", got)
 	}
 
 	refl.accept(t)
 	typ, body := refl.readFrame(t)
-	if typ != 5 || len(body) != 4 || body[0] != 0 || body[1] != 2 || body[2] != 0 || body[3] != 0 {
+	if typ != 5 || !versionIs(body, 3, 0) {
-		t.Fatalf("first frame type %d body %v, want protocol 2.0", typ, body)
+		t.Fatalf("first frame type %d body %v, want protocol 3.0", typ, body)
+	}
+	refl.writeFrame(t, 6, versionWire(2, 0))
+	refl.accept(t)
+	typ, body = refl.readFrame(t)
+	if typ != 5 || !versionIs(body, 2, 0) {
+		t.Fatalf("fallback frame type %d body %v, want protocol 2.0", typ, body)
 	}
 
 	challenge := make([]byte, 20)
@@ -91,8 +100,8 @@ func TestLoginAnnouncesProtocolAndJoinsTheTalkGroup(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if got.Detail != "Idle" || got.Talker != "" {
+	if got.Detail != "Idle" || got.Talker != "" || got.Protocol != "2.0" {
-		t.Fatalf("State = %+v, want Connected Idle", got)
+		t.Fatalf("State = %+v, want Connected Idle protocol 2.0", got)
 	}
 
 	// No other talk group: the next TCP message is a heartbeat, not a monitor set.

station/session_udp.go

@@ -0,0 +1,246 @@
+package station
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+	"net"
+	"time"
+)
+
+func (s *Station) finishV3UDP(conn net.Conn, ex *exchange) error {
+	udpConn, peer, err := dialAudio(conn)
+	if err != nil {
+		s.dropAudio()
+		return err
+	}
+	ch := make(chan []byte, 32)
+	errc := make(chan error, 1)
+	go readUDP(udpConn, peer, ch, errc, ex.done)
+	s.mu.Lock()
+	s.udp = udpConn
+	s.udpPeer = peer
+	s.udpWait = true
+	s.txCounter = 1
+	s.rxCounter = 0
+	err = s.sendRegistration()
+	s.mu.Unlock()
+	if err != nil {
+		s.dropAudio()
+		udpConn.Close()
+		return err
+	}
+	ex.udpCh = ch
+	ex.udpErr = errc
+	ex.udpReady = true
+	ex.ph = phBeat
+	return nil
+}
+
+func dialAudio(conn net.Conn) (*net.UDPConn, *net.UDPAddr, error) {
+	remote, ok := conn.RemoteAddr().(*net.TCPAddr)
+	if !ok {
+		return nil, nil, errors.New("tcp peer has no address")
+	}
+	local := &net.UDPAddr{Port: 0}
+	if tcpLocal, ok := conn.LocalAddr().(*net.TCPAddr); ok && tcpLocal.IP != nil {
+		local.IP = tcpLocal.IP
+	}
+	udpConn, err := net.ListenUDP("udp", local)
+	if err != nil {
+		return nil, nil, err
+	}
+	return udpConn, &net.UDPAddr{IP: append(net.IP(nil), remote.IP...), Port: remote.Port}, nil
+}
+
+func (s *Station) dropAudio() {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.enc != nil {
+		s.enc.Close()
+		s.enc = nil
+	}
+	if s.dec != nil {
+		s.dec.Close()
+		s.dec = nil
+	}
+}
+
+func readUDP(conn *net.UDPConn, peer *net.UDPAddr, out chan<- []byte, errc chan<- error, done <-chan struct{}) {
+	buf := make([]byte, 2048)
+	for {
+		n, addr, err := conn.ReadFromUDP(buf)
+		if err != nil {
+			select {
+			case errc <- err:
+			case <-done:
+			}
+			return
+		}
+		if addr == nil || peer == nil || !addr.IP.Equal(peer.IP) || addr.Port != peer.Port {
+			continue
+		}
+		pkt := append([]byte(nil), buf[:n]...)
+		select {
+		case out <- pkt:
+		case <-done:
+			return
+		}
+	}
+}
+
+func (s *Station) onUDP(w io.Writer, pkt []byte, ex *exchange, udpRx *time.Time, now time.Time) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.secure {
+		plain, ok := s.openSecure(pkt)
+		if !ok {
+			return nil
+		}
+		*udpRx = now.Add(60 * time.Second)
+		if len(plain) < 2 {
+			return nil
+		}
+		typ := binary.BigEndian.Uint16(plain[:2])
+		body := plain[2:]
+		if s.udpWait {
+			if typ != udpHeartbeat {
+				return nil
+			}
+			s.udpWait = false
+			s.mu.Unlock()
+			var tg [4]byte
+			binary.BigEndian.PutUint32(tg[:], uint32(s.cfg.talkGroup))
+			err := writeFrame(w, tcpSelectTG, tg[:])
+			s.mu.Lock()
+			if err != nil {
+				return err
+			}
+			ex.lastTCP = s.clock.Now()
+			s.state.Connection = "Connected"
+			s.up = true
+			s.outage = false
+			s.noteTransmitLocked()
+			s.writeLog(s.clock.Now(), "connected")
+			s.publish()
+			ex.ph = phRun
+			return nil
+		}
+		s.onPlain(typ, body, now)
+		return nil
+	}
+	if !s.acceptV2(pkt) {
+		return nil
+	}
+	*udpRx = now.Add(60 * time.Second)
+	typ := binary.BigEndian.Uint16(pkt[:2])
+	s.onPlain(typ, pkt[6:], now)
+	return nil
+}
+
+func (s *Station) openSecure(pkt []byte) ([]byte, bool) {
+	if len(pkt) < 12 || s.udpKey == nil {
+		return nil, false
+	}
+	counter := binary.BigEndian.Uint32(pkt[:4])
+	if counter < s.rxCounter {
+		return nil, false
+	}
+	tag := pkt[4:12]
+	ct := pkt[12:]
+	plain, err := openDatagram(s.udpKey, s.ivPrefix, 0, counter, pkt[:4], tag, ct)
+	if err != nil {
+		return nil, false
+	}
+	s.rxCounter = counter + 1
+	return plain, true
+}
+
+func (s *Station) acceptV2(pkt []byte) bool {
+	if len(pkt) < 6 {
+		return false
+	}
+	if binary.BigEndian.Uint16(pkt[2:4]) != s.clientID {
+		return false
+	}
+	seq := binary.BigEndian.Uint16(pkt[4:6])
+	diff := seq - s.rxSeq
+	if diff > 32767 {
+		return false
+	}
+	s.rxSeq = seq + 1
+	return true
+}
+
+func (s *Station) onPlain(typ uint16, body []byte, now time.Time) {
+	switch typ {
+	case udpAllFlushed:
+		s.flushWaiting = false
+	case udpAudio:
+		if s.dec == nil || s.transmitting() {
+			return
+		}
+		packet, _, err := parseBlob(body)
+		if err != nil {
+			return
+		}
+		pcm, err := s.dec.Decode(packet)
+		if err != nil {
+			return
+		}
+		s.play = append(s.play, pcm...)
+		s.roomBusy = true
+		s.audioHeard = true
+		s.lastAudio = now
+		s.publish()
+	}
+}
+
+func (s *Station) sendRegistration() error {
+	return s.sendSecure(udpHeartbeat, nil, 0, true)
+}
+
+func (s *Station) sendUDP(typ uint16, body []byte) error {
+	if s.udp == nil {
+		return errors.New("udp is down")
+	}
+	if s.secure {
+		return s.sendSecure(typ, body, s.txCounter, false)
+	}
+	buf := make([]byte, 6+len(body))
+	binary.BigEndian.PutUint16(buf[0:2], typ)
+	binary.BigEndian.PutUint16(buf[2:4], s.clientID)
+	binary.BigEndian.PutUint16(buf[4:6], s.seq)
+	s.seq++
+	copy(buf[6:], body)
+	if _, err := s.udp.WriteToUDP(buf, s.udpPeer); err != nil {
+		return err
+	}
+	s.lastUDPSend = s.clock.Now()
+	return nil
+}
+
+func (s *Station) sendSecure(typ uint16, body []byte, counter uint32, reg bool) error {
+	plain := appendU16(nil, typ)
+	plain = append(plain, body...)
+	var aad []byte
+	id := s.clientID
+	if reg {
+		aad = registrationAAD(s.clientID)
+		counter = 0
+	} else {
+		aad = counterAAD(counter)
+	}
+	wire, err := sealDatagram(s.udpKey, s.ivPrefix, id, counter, aad, plain)
+	if err != nil {
+		return err
+	}
+	if _, err := s.udp.WriteToUDP(wire, s.udpPeer); err != nil {
+		return err
+	}
+	s.lastUDPSend = s.clock.Now()
+	if !reg {
+		s.txCounter = counter + 1
+	}
+	return nil
+}

station/session_v3.go

@@ -0,0 +1,259 @@
+package station
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+func (s *Station) onV3(ctx context.Context, wire *framed, f frame, ex *exchange) error {
+	switch f.typ {
+	case tcpCAInfo:
+		if ex.ph != phCA {
+			return nil
+		}
+		return s.onCAInfo(wire, f.body, ex)
+	case tcpCABundle:
+		if ex.ph != phBundle {
+			return nil
+		}
+		return s.onCABundle(wire, f.body, ex)
+	case tcpStartEnc:
+		if ex.ph != phStart {
+			return nil
+		}
+		return s.onStartEncryption(ctx, wire, ex)
+	case tcpCsrReq:
+		return s.sendCSR(wire, ex)
+	case tcpAuthChallenge:
+		return s.answerChallenge(wire, f.body, ex)
+	case tcpAuthOK:
+		ex.authed = true
+		ex.ph = phServer
+		newer, err := csrNewerThanCert(s.cfg.certificateDir)
+		if err != nil {
+			s.endFatalCause("Cannot create "+s.cfg.certificateDir, err, true)
+			return errStopped
+		}
+		if newer {
+			if err := s.sendCSR(wire, ex); err != nil {
+				return err
+			}
+		}
+		return nil
+	case tcpClientCert:
+		return s.saveCert(f.body)
+	case tcpServerInfo:
+		if !ex.authed {
+			return s.retry("Protocol error", nil)
+		}
+		return s.finishV3Server(wire, f.body, ex)
+	case tcpStartUDPEnc:
+		if ex.ph != phUDP {
+			return nil
+		}
+		return s.finishV3UDP(wire.conn, ex)
+	case tcpTalkerStart:
+		s.onTalker(f.body, true)
+		return nil
+	case tcpTalkerStop:
+		s.onTalker(f.body, false)
+		return nil
+	case tcpNodeList, tcpNodeJoined, tcpNodeLeft, tcpRequestQSY, tcpStateEvent, tcpSignal, tcpTxStatus:
+		if err := unpackIgnored(f); err != nil {
+			return s.retry("Protocol error", err)
+		}
+		return nil
+	default:
+		return nil
+	}
+}
+
+func (s *Station) onCAInfo(w io.Writer, body []byte, ex *exchange) error {
+	_, digest, err := parseCAInfo(body)
+	if err != nil {
+		return s.retry("Protocol error", err)
+	}
+	if err := ensureCertDir(s.cfg.certificateDir); err != nil {
+		s.endFatalCause("Cannot create "+s.cfg.certificateDir, err, true)
+		return errStopped
+	}
+	sum, ok, err := caDigest(s.cfg.certificateDir)
+	if err != nil {
+		s.endFatalCause("Cannot create "+s.cfg.certificateDir, err, true)
+		return errStopped
+	}
+	if ok {
+		if !bytes.Equal(sum[:], digest) {
+			s.mu.Lock()
+			s.writeLog(s.clock.Now(), "CA digest differs")
+			s.mu.Unlock()
+		}
+		if err := writeFrame(w, tcpStartEncReq, nil); err != nil {
+			return err
+		}
+		ex.lastTCP = s.clock.Now()
+		ex.ph = phStart
+		return nil
+	}
+	if err := writeFrame(w, tcpCABundleReq, nil); err != nil {
+		return err
+	}
+	ex.lastTCP = s.clock.Now()
+	ex.ph = phBundle
+	return nil
+}
+
+func parseCAInfo(b []byte) (uint16, []byte, error) {
+	size, rest, err := parseU16(b)
+	if err != nil {
+		return 0, nil, err
+	}
+	digest, rest, err := parseBlob(rest)
+	if err != nil {
+		return 0, nil, err
+	}
+	if len(digest) != sha256Len || len(rest) != 0 {
+		return 0, nil, io.ErrUnexpectedEOF
+	}
+	return size, digest, nil
+}
+
+const sha256Len = 32
+
+func (s *Station) onCABundle(w io.Writer, body []byte, ex *exchange) error {
+	caPEM, rest, err := parseString(body)
+	if err != nil {
+		return s.retry("CA signature rejected", err)
+	}
+	sig, rest, err := parseBlob(rest)
+	if err != nil {
+		return s.retry("CA signature rejected", err)
+	}
+	certPEM, rest, err := parseString(rest)
+	if err != nil {
+		return s.retry("CA signature rejected", err)
+	}
+	if len(rest) != 0 {
+		return s.retry("CA signature rejected", nil)
+	}
+	if err := verifyCABundle(caPEM, sig, certPEM); err != nil {
+		return s.retry("CA signature rejected", err)
+	}
+	if err := writeCABundle(s.cfg.certificateDir, caPEM); err != nil {
+		s.endFatalCause("Cannot create "+s.cfg.certificateDir, err, true)
+		return errStopped
+	}
+	if err := writeFrame(w, tcpStartEncReq, nil); err != nil {
+		return err
+	}
+	ex.lastTCP = s.clock.Now()
+	ex.ph = phStart
+	return nil
+}
+
+func (s *Station) onStartEncryption(ctx context.Context, wire *framed, ex *exchange) error {
+	pair, present, fatal, cause := prepareIdentity(s.cfg.certificateDir, s.cfg.callsign)
+	if fatal != "" {
+		s.endFatalCause(fatal, cause, true)
+		return errStopped
+	}
+	ex.client = pair
+	ex.haveCert = present
+	caPath := filepath.Join(s.cfg.certificateDir, caFileName)
+	caPEM, err := os.ReadFile(caPath)
+	if err != nil {
+		s.endFatalCause("Cannot create "+caPath, err, true)
+		return errStopped
+	}
+	cfg, err := tlsConfig(s.cfg.host, caPEM, pair, present)
+	if err != nil {
+		return s.retry("TLS handshake failed", err)
+	}
+	if err := s.startTLS(ctx, wire, cfg, ex.limit); err != nil {
+		if errors.Is(err, errHostMismatch) {
+			return s.retry("Reflector certificate does not match the host", err)
+		}
+		if ctx.Err() != nil {
+			return ctx.Err()
+		}
+		return s.retry("TLS handshake failed", err)
+	}
+	ex.ph = phIdent
+	return nil
+}
+
+func (s *Station) sendCSR(w io.Writer, ex *exchange) error {
+	csrPath := filepath.Join(s.cfg.certificateDir, csrFileName)
+	pem, err := readCSR(s.cfg.certificateDir)
+	if err != nil {
+		s.endFatalCause("Cannot create "+csrPath, err, true)
+		return errStopped
+	}
+	if err := writeFrame(w, tcpCsr, appendString(nil, pem)); err != nil {
+		return err
+	}
+	ex.lastTCP = s.clock.Now()
+	return nil
+}
+
+func (s *Station) saveCert(body []byte) error {
+	pem, _, err := parseString(body)
+	if err != nil || pem == "" {
+		return s.retry("Protocol error", err)
+	}
+	certPath := filepath.Join(s.cfg.certificateDir, certFileName)
+	if err := writeClientCert(s.cfg.certificateDir, pem); err != nil {
+		s.endFatalCause("Cannot create "+certPath, err, true)
+		return errStopped
+	}
+	return errReconnect
+}
+func (s *Station) finishV3Server(wire *framed, body []byte, ex *exchange) error {
+	id, enc, dec, err := s.acceptServer(body)
+	if err != nil {
+		return err
+	}
+	if enc == nil {
+		return errStopped
+	}
+	iv := make([]byte, 6)
+	key := make([]byte, 16)
+	if _, err := rand.Read(iv); err != nil {
+		enc.Close()
+		dec.Close()
+		return fmt.Errorf("udp key: %w", err)
+	}
+	if _, err := rand.Read(key); err != nil {
+		enc.Close()
+		dec.Close()
+		return fmt.Errorf("udp key: %w", err)
+	}
+	info, err := identityV3(iv, key)
+	if err != nil {
+		enc.Close()
+		dec.Close()
+		return err
+	}
+	if err := writeFrame(wire, tcpNodeInfo, info); err != nil {
+		enc.Close()
+		dec.Close()
+		return err
+	}
+	ex.lastTCP = s.clock.Now()
+	s.mu.Lock()
+	s.clientID = id
+	s.enc = enc
+	s.dec = dec
+	s.ivPrefix = iv
+	s.udpKey = key
+	s.secure = true
+	s.mu.Unlock()
+	ex.ph = phUDP
+	return nil
+}

station/software.go

@@ -1,6 +1,11 @@
 package station
 
-import jsonv2 "encoding/json/v2"
+import (
+	"bytes"
+	jsonv2 "encoding/json/v2"
+
+	"golang.org/x/sys/unix"
+)
 
 // SoftwareName and SoftwareVersion are the identity sent to the reflector
 // after login. Edit them here.
@@ -9,16 +14,57 @@ const (
 	SoftwareVersion = "1.0.0"
 )
 
+type softwareIdentity struct {
+	SW          string `json:"sw"`
+	SWVer       string `json:"swVer"`
+	ProjVer     string `json:"projVer"`
+	MachineArch string `json:"machineArch,omitzero"`
+}
+
 func softwareIdentityBody() ([]byte, error) {
-	raw, err := jsonv2.Marshal(struct {
+	raw, err := marshalIdentity(false)
-		SW    string `json:"sw"`
-		SWVer string `json:"swVer"`
-	}{
-		SW:    SoftwareName,
-		SWVer: SoftwareVersion,
-	})
 	if err != nil {
 		return nil, err
 	}
 	return appendString(nil, string(raw)), nil
 }
+
+func identityV3(iv, key []byte) ([]byte, error) {
+	raw, err := marshalIdentity(true)
+	if err != nil {
+		return nil, err
+	}
+	body := appendBlob(nil, iv)
+	body = appendBlob(body, key)
+	return appendString(body, string(raw)), nil
+}
+
+func marshalIdentity(arch bool) ([]byte, error) {
+	info := softwareIdentity{
+		SW:      SoftwareName,
+		SWVer:   SoftwareVersion,
+		ProjVer: SoftwareVersion,
+	}
+	if arch {
+		if name, ok := MachineArch(); ok {
+			info.MachineArch = name
+		}
+	}
+	return jsonv2.Marshal(info)
+}
+
+// MachineArch is the hardware name from uname, when it can be read.
+func MachineArch() (string, bool) {
+	var u unix.Utsname
+	if err := unix.Uname(&u); err != nil {
+		return "", false
+	}
+	b := u.Machine[:]
+	if i := bytes.IndexByte(b, 0); i >= 0 {
+		b = b[:i]
+	}
+	if len(b) == 0 {
+		return "", false
+	}
+	return string(b), true
+}

station/station.go

@@ -24,6 +24,7 @@ type State struct {
 	Detail       string `json:"detail"`
 	Callsign     string `json:"callsign"`
 	TalkGroup    int    `json:"talkGroup"`
+	Protocol     string `json:"protocol"`
 	Talker       string `json:"talker"`
 	Transmitting bool   `json:"transmitting"`
 }
@@ -39,13 +40,27 @@ type Station struct {
 	buttonHeld   bool
 	spaceHeld    bool
 	fatal        string
+	retryReason  string
+	protocol     string
 	remoteTalker string
 	roomBusy     bool
+	audioHeard   bool
+	lastAudio    time.Time
+	flushWaiting bool
+	flushAt      time.Time
+	rxSeq        uint16
+	secure       bool
+	udpWait      bool
+	ivPrefix     []byte
+	udpKey       []byte
+	rxCounter    uint32
+	txCounter    uint32
 	mic          []int16
 	play         []int16
 	clientID     uint16
 	seq          uint16
 	udp          *net.UDPConn
+	udpPeer      *net.UDPAddr
 	lastUDPSend  time.Time
 	enc          *opus.Encoder
 	dec          *opus.Decoder
@@ -73,7 +88,9 @@ func New(opt Options) (*Station, error) {
 		clock = wallClock{}
 	}
 	detail := "Idle"
-	if cfg.logNotice != "" {
+	if cfg.certFatal != "" {
+		detail = cfg.certFatal
+	} else if cfg.logNotice != "" {
 		detail = cfg.logNotice
 	}
 	s := &Station{
@@ -82,6 +99,7 @@ func New(opt Options) (*Station, error) {
 		wake:      make(chan struct{}, 1),
 		logPath:   cfg.logPath,
 		logNotice: cfg.logNotice,
+		fatal:     cfg.certFatal,
 		state: State{
 			Connection: "Disconnected",
 			Detail:     detail,

station/tls.go

@@ -0,0 +1,60 @@
+package station
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"errors"
+	"net"
+	"strings"
+)
+
+var errHostMismatch = errors.New("host mismatch")
+
+func tlsConfig(host string, caPEM []byte, client tls.Certificate, present bool) (*tls.Config, error) {
+	pool := x509.NewCertPool()
+	if !pool.AppendCertsFromPEM(caPEM) {
+		return nil, errors.New("ca bundle")
+	}
+	cfg := &tls.Config{
+		MinVersion:         tls.VersionTLS12,
+		RootCAs:            pool,
+		InsecureSkipVerify: true,
+		VerifyConnection: func(cs tls.ConnectionState) error {
+			return verifyPeer(host, pool, cs)
+		},
+	}
+	if present {
+		cfg.Certificates = []tls.Certificate{client}
+	}
+	return cfg, nil
+}
+
+func verifyPeer(host string, pool *x509.CertPool, cs tls.ConnectionState) error {
+	if len(cs.PeerCertificates) == 0 {
+		return errors.New("no peer certificate")
+	}
+	leaf := cs.PeerCertificates[0]
+	opts := x509.VerifyOptions{Roots: pool, KeyUsages: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth}}
+	if len(cs.PeerCertificates) > 1 {
+		opts.Intermediates = x509.NewCertPool()
+		for _, cert := range cs.PeerCertificates[1:] {
+			opts.Intermediates.AddCert(cert)
+		}
+	}
+	if _, err := leaf.Verify(opts); err != nil {
+		return err
+	}
+	host = strings.TrimSuffix(host, ".")
+	if ip := net.ParseIP(host); ip != nil {
+		for _, cand := range leaf.IPAddresses {
+			if cand.Equal(ip) {
+				return nil
+			}
+		}
+		return errHostMismatch
+	}
+	if err := leaf.VerifyHostname(host); err != nil {
+		return errHostMismatch
+	}
+	return nil
+}