Add optional aes128xor layer

https://github.com/XTLS/Xray-core/pull/4952#issuecomment-3172703168

proxy/vless/encryption/client.go

@@ -28,6 +28,7 @@ func init() {
 type ClientInstance struct {
 	sync.RWMutex
 	eKeyNfs *mlkem.EncapsulationKey768
+	xor     uint32
 	minutes time.Duration
 	expire  time.Time
 	baseKey []byte
@@ -47,8 +48,9 @@ type ClientConn struct {
 	peerCache []byte
 }
 
-func (i *ClientInstance) Init(eKeyNfsData []byte, minutes time.Duration) (err error) {
+func (i *ClientInstance) Init(eKeyNfsData []byte, xor uint32, minutes time.Duration) (err error) {
 	i.eKeyNfs, err = mlkem.NewEncapsulationKey768(eKeyNfsData)
+	i.xor = xor
 	i.minutes = minutes
 	return
 }
@@ -57,6 +59,9 @@ func (i *ClientInstance) Handshake(conn net.Conn) (net.Conn, error) {
 	if i.eKeyNfs == nil {
 		return nil, errors.New("uninitialized")
 	}
+	if i.xor == 1 {
+		conn = NewXorConn(conn, i.eKeyNfs.Bytes())
+	}
 	c := &ClientConn{Conn: conn}
 
 	if i.minutes > 0 {

proxy/vless/encryption/server.go

@@ -26,6 +26,7 @@ type ServerSession struct {
 type ServerInstance struct {
 	sync.RWMutex
 	dKeyNfs  *mlkem.DecapsulationKey768
+	xor      uint32
 	minutes  time.Duration
 	sessions map[[21]byte]*ServerSession
 }
@@ -43,8 +44,9 @@ type ServerConn struct {
 	nonce      []byte
 }
 
-func (i *ServerInstance) Init(dKeyNfsData []byte, minutes time.Duration) (err error) {
+func (i *ServerInstance) Init(dKeyNfsData []byte, xor uint32, minutes time.Duration) (err error) {
 	i.dKeyNfs, err = mlkem.NewDecapsulationKey768(dKeyNfsData)
+	i.xor = xor
 	if minutes > 0 {
 		i.minutes = minutes
 		i.sessions = make(map[[21]byte]*ServerSession)
@@ -69,6 +71,9 @@ func (i *ServerInstance) Handshake(conn net.Conn) (net.Conn, error) {
 	if i.dKeyNfs == nil {
 		return nil, errors.New("uninitialized")
 	}
+	if i.xor == 1 {
+		conn = NewXorConn(conn, i.dKeyNfs.EncapsulationKey().Bytes())
+	}
 	c := &ServerConn{Conn: conn}
 
 	peerTicketHello := make([]byte, 21+32)

proxy/vless/encryption/xor.go

@@ -0,0 +1,63 @@
+package encryption
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"io"
+	"net"
+)
+
+type XorConn struct {
+	net.Conn
+	key     []byte
+	ctr     cipher.Stream
+	peerCtr cipher.Stream
+}
+
+func NewXorConn(conn net.Conn, key []byte) *XorConn {
+	return &XorConn{Conn: conn, key: key[:16]}
+}
+
+func (c *XorConn) Write(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, nil
+	}
+	var iv []byte
+	if c.ctr == nil {
+		block, _ := aes.NewCipher(c.key)
+		iv = make([]byte, 16)
+		rand.Read(iv)
+		c.ctr = cipher.NewCTR(block, iv)
+	}
+	c.ctr.XORKeyStream(b, b) // caller MUST discard b
+	if iv != nil {
+		b = append(iv, b...)
+	}
+	if _, err := c.Conn.Write(b); err != nil {
+		return 0, err
+	}
+	if iv != nil {
+		b = b[16:]
+	}
+	return len(b), nil
+}
+
+func (c *XorConn) Read(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, nil
+	}
+	if c.peerCtr == nil {
+		peerIv := make([]byte, 16)
+		if _, err := io.ReadFull(c.Conn, peerIv); err != nil {
+			return 0, err
+		}
+		block, _ := aes.NewCipher(c.key)
+		c.peerCtr = cipher.NewCTR(block, peerIv)
+	}
+	n, err := c.Conn.Read(b)
+	if n > 0 {
+		c.peerCtr.XORKeyStream(b[:n], b[:n])
+	}
+	return n, err
+}