fix(listen): allow nil body packets

gold/link/crypto.go

@@ -4,10 +4,15 @@ import (
 	"crypto/cipher"
 	"crypto/rand"
 	"encoding/binary"
+	"errors"
 	"math/bits"
 	mrand "math/rand"
 )
 
+var (
+	ErrCipherTextTooShort = errors.New("ciphertext too short")
+)
+
 func (l *Link) randkeyidx() uint8 {
 	if l.keys[1] == nil {
 		return 0
@@ -63,7 +68,7 @@ func (l *Link) Encode(teatype uint8, additional uint16, b []byte) (eb []byte) {
 }
 
 // Decode 使用 xchacha20poly1305 和密钥序列解密
-func (l *Link) Decode(teatype uint8, additional uint16, b []byte) (db []byte) {
+func (l *Link) Decode(teatype uint8, additional uint16, b []byte) (db []byte, err error) {
 	if b == nil || teatype >= 32 {
 		return
 	}
@@ -75,8 +80,7 @@ func (l *Link) Decode(teatype uint8, additional uint16, b []byte) (db []byte) {
 	if aead == nil {
 		return
 	}
-	db = decode(aead, additional, b)
+	return decode(aead, additional, b)
-	return
 }
 
 // encode 使用 xchacha20poly1305 加密
@@ -96,18 +100,17 @@ func encode(aead cipher.AEAD, additional uint16, b []byte) (eb []byte) {
 }
 
 // decode 使用 xchacha20poly1305 解密
-func decode(aead cipher.AEAD, additional uint16, b []byte) (db []byte) {
+func decode(aead cipher.AEAD, additional uint16, b []byte) ([]byte, error) {
 	nsz := aead.NonceSize()
-	if len(b) < nsz { // ciphertext too short
+	if len(b) < nsz {
-		return
+		return nil, ErrCipherTextTooShort
 	}
 	// Split nonce and ciphertext.
 	nonce, ciphertext := b[:nsz], b[nsz:]
 	// Decrypt the message and check it wasn't tampered with.
 	var buf [2]byte
 	binary.LittleEndian.PutUint16(buf[:], additional)
-	db, _ = aead.Open(nil, nonce, ciphertext, buf[:])
+	return aead.Open(nil, nonce, ciphertext, buf[:])
-	return
 }
 
 // xorenc 按 8 字节, 以初始 m.mask 循环异或编码 data

gold/link/crypto_test.go

@@ -45,7 +45,11 @@ func TestXChacha20(t *testing.T) {
 	}
 	data := []byte("12345678")
 	for i := uint64(0); i < 100000; i++ {
-		if !bytes.Equal(decode(aead, uint16(i), encode(aead, uint16(i), data)), data) {
+		db, err := decode(aead, uint16(i), encode(aead, uint16(i), data))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !bytes.Equal(db, data) {
 			t.Fatal("unexpected preshared at", i, "addt", uint16(i))
 		}
 	}

gold/link/listen.go

@@ -61,6 +61,7 @@ func (m *Me) listenudp() (conn *net.UDPConn, err error) {
 					logrus.Errorln("[listen] reconnect udp err:", err)
 					return
 				}
+				logrus.Debugln("[listen] unlock index", i)
 				hasntfinished[i].Unlock()
 				i--
 				continue
@@ -75,6 +76,7 @@ func (m *Me) listenudp() (conn *net.UDPConn, err error) {
 			}
 			packet := m.wait(lbf[:n])
 			if packet == nil {
+				logrus.Debugln("[listen] unlock index", i)
 				hasntfinished[i].Unlock()
 				i--
 				continue
@@ -87,6 +89,7 @@ func (m *Me) listenudp() (conn *net.UDPConn, err error) {
 
 func (m *Me) listenthread(packet *head.Packet, addr *net.UDPAddr, index int, finish func()) {
 	defer finish()
+	defer logrus.Debugln("[listen] unlock index", index)
 	sz := packet.TeaTypeDataSZ & 0x0000ffff
 	r := int(sz) - len(packet.Data)
 	if r > 0 {
@@ -108,9 +111,10 @@ func (m *Me) listenthread(packet *head.Packet, addr *net.UDPAddr, index int, fin
 	switch {
 	case p.IsToMe(packet.Dst):
 		addt := packet.AdditionalData()
-		packet.Data = p.Decode(uint8(packet.TeaTypeDataSZ>>27), addt, packet.Data)
+		var err error
-		if packet.Data == nil {
+		packet.Data, err = p.Decode(uint8(packet.TeaTypeDataSZ>>27), addt, packet.Data)
-			logrus.Debugln("[listen] @", index, "drop invalid packet, addt:", addt)
+		if err != nil {
+			logrus.Debugln("[listen] @", index, "drop invalid packet, addt:", addt, "err:", err)
 			packet.Put()
 			return
 		}