fmt

common/singbridge/destination.go

@@ -1,53 +0,0 @@
-package singbridge
-
-import (
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
-	"github.com/xtls/xray-core/common/errors"
-	"github.com/xtls/xray-core/common/net"
-)
-
-func ToNetwork(network string) net.Network {
-	switch N.NetworkName(network) {
-	case N.NetworkTCP:
-		return net.Network_TCP
-	case N.NetworkUDP:
-		return net.Network_UDP
-	default:
-		return net.Network_Unknown
-	}
-}
-
-func ToDestination(socksaddr M.Socksaddr, network net.Network) (net.Destination, error) {
-	// IsFqdn() implicitly checks if the domain name is valid
-	if socksaddr.IsFqdn() {
-		return net.Destination{
-			Network: network,
-			Address: net.DomainAddress(socksaddr.Fqdn),
-			Port:    net.Port(socksaddr.Port),
-		}, nil
-	}
-
-	// IsIP() implicitly checks if the IP address is valid
-	if socksaddr.IsIP() {
-		return net.Destination{
-			Network: network,
-			Address: net.IPAddress(socksaddr.Addr.AsSlice()),
-			Port:    net.Port(socksaddr.Port),
-		}, nil
-	}
-
-	return net.Destination{}, errors.New("invalid socks address: ", socksaddr)
-}
-
-func ToSocksaddr(destination net.Destination) M.Socksaddr {
-	var addr M.Socksaddr
-	switch destination.Address.Family() {
-	case net.AddressFamilyDomain:
-		addr.Fqdn = destination.Address.Domain()
-	default:
-		addr.Addr = M.AddrFromIP(destination.Address.IP())
-	}
-	addr.Port = uint16(destination.Port)
-	return addr
-}

common/singbridge/dialer.go

@@ -1,72 +0,0 @@
-package singbridge
-
-import (
-	"context"
-	"os"
-
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
-	"github.com/xtls/xray-core/common/net"
-	"github.com/xtls/xray-core/common/net/cnc"
-	"github.com/xtls/xray-core/common/session"
-	"github.com/xtls/xray-core/proxy"
-	"github.com/xtls/xray-core/transport"
-	"github.com/xtls/xray-core/transport/internet"
-	"github.com/xtls/xray-core/transport/pipe"
-)
-
-var _ N.Dialer = (*XrayDialer)(nil)
-
-type XrayDialer struct {
-	internet.Dialer
-}
-
-func NewDialer(dialer internet.Dialer) *XrayDialer {
-	return &XrayDialer{dialer}
-}
-
-func (d *XrayDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
-	dest, err := ToDestination(destination, ToNetwork(network))
-	if err != nil {
-		return nil, err
-	}
-	return d.Dialer.Dial(ctx, dest)
-}
-
-func (d *XrayDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
-	return nil, os.ErrInvalid
-}
-
-type XrayOutboundDialer struct {
-	outbound proxy.Outbound
-	dialer   internet.Dialer
-}
-
-func NewOutboundDialer(outbound proxy.Outbound, dialer internet.Dialer) *XrayOutboundDialer {
-	return &XrayOutboundDialer{outbound, dialer}
-}
-
-func (d *XrayOutboundDialer) DialContext(ctx context.Context, network string, destination M.Socksaddr) (net.Conn, error) {
-	dest, err := ToDestination(destination, ToNetwork(network))
-	if err != nil {
-		return nil, err
-	}
-	outbounds := session.OutboundsFromContext(ctx)
-	if len(outbounds) == 0 {
-		outbounds = []*session.Outbound{{}}
-		ctx = session.ContextWithOutbounds(ctx, outbounds)
-	}
-	ob := outbounds[len(outbounds)-1]
-	ob.Target = dest
-
-	opts := []pipe.Option{pipe.WithSizeLimit(64 * 1024)}
-	uplinkReader, uplinkWriter := pipe.New(opts...)
-	downlinkReader, downlinkWriter := pipe.New(opts...)
-	conn := cnc.NewConnection(cnc.ConnectionInputMulti(downlinkWriter), cnc.ConnectionOutputMulti(uplinkReader))
-	go d.outbound.Process(ctx, &transport.Link{Reader: downlinkReader, Writer: uplinkWriter}, d.dialer)
-	return conn, nil
-}
-
-func (d *XrayOutboundDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
-	return nil, os.ErrInvalid
-}

common/singbridge/error.go

@@ -1,10 +0,0 @@
-package singbridge
-
-import E "github.com/sagernet/sing/common/exceptions"
-
-func ReturnError(err error) error {
-	if E.IsClosedOrCanceled(err) {
-		return nil
-	}
-	return err
-}

common/singbridge/handler.go

@@ -1,58 +0,0 @@
-package singbridge
-
-import (
-	"context"
-	"io"
-
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
-	"github.com/xtls/xray-core/common/buf"
-	"github.com/xtls/xray-core/common/errors"
-	"github.com/xtls/xray-core/common/net"
-	"github.com/xtls/xray-core/features/routing"
-	"github.com/xtls/xray-core/transport"
-)
-
-var (
-	_ N.TCPConnectionHandler = (*Dispatcher)(nil)
-	_ N.UDPConnectionHandler = (*Dispatcher)(nil)
-)
-
-type Dispatcher struct {
-	upstream     routing.Dispatcher
-	newErrorFunc func(values ...any) *errors.Error
-}
-
-func NewDispatcher(dispatcher routing.Dispatcher, newErrorFunc func(values ...any) *errors.Error) *Dispatcher {
-	return &Dispatcher{
-		upstream:     dispatcher,
-		newErrorFunc: newErrorFunc,
-	}
-}
-
-func (d *Dispatcher) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
-	dest, err := ToDestination(metadata.Destination, net.Network_TCP)
-	if err != nil {
-		return err
-	}
-	xConn := NewConn(conn)
-	return d.upstream.DispatchLink(ctx, dest, &transport.Link{
-		Reader: xConn,
-		Writer: xConn,
-	})
-}
-
-func (d *Dispatcher) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata M.Metadata) error {
-	dest, err := ToDestination(metadata.Destination, net.Network_UDP)
-	if err != nil {
-		return err
-	}
-	return d.upstream.DispatchLink(ctx, dest, &transport.Link{
-		Reader: buf.NewPacketReader(conn.(io.Reader)),
-		Writer: buf.NewWriter(conn.(io.Writer)),
-	})
-}
-
-func (d *Dispatcher) NewError(ctx context.Context, err error) {
-	errors.LogInfo(ctx, err.Error())
-}

common/singbridge/logger.go

@@ -1,70 +0,0 @@
-package singbridge
-
-import (
-	"context"
-
-	"github.com/sagernet/sing/common/logger"
-	"github.com/xtls/xray-core/common/errors"
-)
-
-var _ logger.ContextLogger = (*XrayLogger)(nil)
-
-type XrayLogger struct {
-	newError func(values ...any) *errors.Error
-}
-
-func NewLogger(newErrorFunc func(values ...any) *errors.Error) *XrayLogger {
-	return &XrayLogger{
-		newErrorFunc,
-	}
-}
-
-func (l *XrayLogger) Trace(args ...any) {
-}
-
-func (l *XrayLogger) Debug(args ...any) {
-	errors.LogDebug(context.Background(), args...)
-}
-
-func (l *XrayLogger) Info(args ...any) {
-	errors.LogInfo(context.Background(), args...)
-}
-
-func (l *XrayLogger) Warn(args ...any) {
-	errors.LogWarning(context.Background(), args...)
-}
-
-func (l *XrayLogger) Error(args ...any) {
-	errors.LogError(context.Background(), args...)
-}
-
-func (l *XrayLogger) Fatal(args ...any) {
-}
-
-func (l *XrayLogger) Panic(args ...any) {
-}
-
-func (l *XrayLogger) TraceContext(ctx context.Context, args ...any) {
-}
-
-func (l *XrayLogger) DebugContext(ctx context.Context, args ...any) {
-	errors.LogDebug(ctx, args...)
-}
-
-func (l *XrayLogger) InfoContext(ctx context.Context, args ...any) {
-	errors.LogInfo(ctx, args...)
-}
-
-func (l *XrayLogger) WarnContext(ctx context.Context, args ...any) {
-	errors.LogWarning(ctx, args...)
-}
-
-func (l *XrayLogger) ErrorContext(ctx context.Context, args ...any) {
-	errors.LogError(ctx, args...)
-}
-
-func (l *XrayLogger) FatalContext(ctx context.Context, args ...any) {
-}
-
-func (l *XrayLogger) PanicContext(ctx context.Context, args ...any) {
-}

common/singbridge/packet.go

@@ -1,107 +0,0 @@
-package singbridge
-
-import (
-	"context"
-	"time"
-
-	B "github.com/sagernet/sing/common/buf"
-	"github.com/sagernet/sing/common/bufio"
-	M "github.com/sagernet/sing/common/metadata"
-	"github.com/xtls/xray-core/common"
-	"github.com/xtls/xray-core/common/buf"
-	"github.com/xtls/xray-core/common/net"
-	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/transport"
-)
-
-func CopyPacketConn(ctx context.Context, inboundConn net.Conn, link *transport.Link, destination net.Destination, serverConn net.PacketConn) error {
-	cancel := func() {
-		common.Interrupt(link.Reader)
-		common.Interrupt(serverConn)
-	}
-	conn := &PacketConnWrapper{
-		Reader: link.Reader,
-		Writer: link.Writer,
-		Dest:   destination,
-		Conn:   inboundConn,
-		T:      signal.CancelAfterInactivity(ctx, cancel, 300*time.Second),
-	}
-	return ReturnError(bufio.CopyPacketConn(ctx, conn, bufio.NewPacketConn(serverConn)))
-}
-
-type PacketConnWrapper struct {
-	buf.Reader
-	buf.Writer
-	net.Conn
-	Dest   net.Destination
-	cached buf.MultiBuffer
-
-	// A simple patch to avoid goroutine leak since sing infra cannot awake read block by write err
-	T *signal.ActivityTimer
-}
-
-func (w *PacketConnWrapper) ReadPacket(buffer *B.Buffer) (addr M.Socksaddr, err error) {
-	w.T.Update()
-	defer func() {
-		if err != nil {
-			// uplinkonly
-			w.T.SetTimeout(2 * time.Second)
-		}
-	}()
-	if w.cached != nil {
-		mb, bb := buf.SplitFirst(w.cached)
-		if bb == nil {
-			w.cached = nil
-		} else {
-			buffer.Write(bb.Bytes())
-			w.cached = mb
-			var destination net.Destination
-			if bb.UDP != nil {
-				destination = *bb.UDP
-			} else {
-				destination = w.Dest
-			}
-			bb.Release()
-			return ToSocksaddr(destination), nil
-		}
-	}
-	mb, err := w.ReadMultiBuffer()
-	nb, bb := buf.SplitFirst(mb)
-	if bb == nil {
-		return M.Socksaddr{}, nil
-	} else {
-		buffer.Write(bb.Bytes())
-		w.cached = nb
-		var destination net.Destination
-		if bb.UDP != nil {
-			destination = *bb.UDP
-		} else {
-			destination = w.Dest
-		}
-		bb.Release()
-		return ToSocksaddr(destination), nil
-	}
-}
-
-func (w *PacketConnWrapper) WritePacket(buffer *B.Buffer, destination M.Socksaddr) (err error) {
-	w.T.Update()
-	defer func() {
-		if err != nil {
-			// downlinkonly
-			w.T.SetTimeout(5 * time.Second)
-		}
-	}()
-	endpoint, err := ToDestination(destination, net.Network_UDP)
-	if err != nil {
-		return err
-	}
-	vBuf := buf.New()
-	vBuf.Write(buffer.Bytes())
-	vBuf.UDP = &endpoint
-	return w.WriteMultiBuffer(buf.MultiBuffer{vBuf})
-}
-
-func (w *PacketConnWrapper) Close() error {
-	buf.ReleaseMulti(w.cached)
-	return nil
-}

common/singbridge/pipe.go

@@ -1,81 +0,0 @@
-package singbridge
-
-import (
-	"context"
-	"io"
-	"net"
-	"time"
-
-	"github.com/sagernet/sing/common/bufio"
-	"github.com/xtls/xray-core/common"
-	"github.com/xtls/xray-core/common/buf"
-	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/transport"
-)
-
-func CopyConn(ctx context.Context, inboundConn net.Conn, link *transport.Link, serverConn net.Conn) error {
-	conn := &PipeConnWrapper{
-		W:    link.Writer,
-		Conn: inboundConn,
-	}
-	if ir, ok := link.Reader.(io.Reader); ok {
-		conn.R = ir
-	} else {
-		conn.R = &buf.BufferedReader{Reader: link.Reader}
-	}
-	cancel := func() {
-		common.Interrupt(link.Reader)
-		common.Interrupt(serverConn)
-	}
-	conn.T = signal.CancelAfterInactivity(ctx, cancel, 300*time.Second)
-	return ReturnError(bufio.CopyConn(ctx, conn, serverConn))
-}
-
-type PipeConnWrapper struct {
-	R io.Reader
-	W buf.Writer
-	net.Conn
-
-	// A simple patch to avoid goroutine leak since sing infra cannot awake read block by write err
-	T *signal.ActivityTimer
-}
-
-func (w *PipeConnWrapper) Close() error {
-	return nil
-}
-
-func (w *PipeConnWrapper) Read(b []byte) (n int, err error) {
-	w.T.Update()
-	n, err = w.R.Read(b)
-	if err != nil {
-		// uplinkonly
-		w.T.SetTimeout(2 * time.Second)
-	}
-	return
-}
-
-func (w *PipeConnWrapper) Write(p []byte) (n int, err error) {
-	w.T.Update()
-	n = len(p)
-	var mb buf.MultiBuffer
-	pLen := len(p)
-	for pLen > 0 {
-		buffer := buf.New()
-		if pLen > buf.Size {
-			_, err = buffer.Write(p[:buf.Size])
-			p = p[buf.Size:]
-		} else {
-			buffer.Write(p)
-		}
-		pLen -= int(buffer.Len())
-		mb = append(mb, buffer)
-	}
-	err = w.W.WriteMultiBuffer(mb)
-	if err != nil {
-		n = 0
-		buf.ReleaseMulti(mb)
-		// downlinkonly
-		w.T.SetTimeout(5 * time.Second)
-	}
-	return
-}

common/singbridge/reader.go

@@ -1,66 +0,0 @@
-package singbridge
-
-import (
-	"time"
-
-	"github.com/sagernet/sing/common"
-	"github.com/sagernet/sing/common/bufio"
-	N "github.com/sagernet/sing/common/network"
-	"github.com/xtls/xray-core/common/buf"
-	"github.com/xtls/xray-core/common/net"
-)
-
-var (
-	_ buf.Reader        = (*Conn)(nil)
-	_ buf.TimeoutReader = (*Conn)(nil)
-	_ buf.Writer        = (*Conn)(nil)
-)
-
-type Conn struct {
-	net.Conn
-	writer N.VectorisedWriter
-}
-
-func NewConn(conn net.Conn) *Conn {
-	writer, _ := bufio.CreateVectorisedWriter(conn)
-	return &Conn{
-		Conn:   conn,
-		writer: writer,
-	}
-}
-
-func (c *Conn) ReadMultiBuffer() (buf.MultiBuffer, error) {
-	buffer, err := buf.ReadBuffer(c.Conn)
-	if err != nil {
-		return nil, err
-	}
-	return buf.MultiBuffer{buffer}, nil
-}
-
-func (c *Conn) ReadMultiBufferTimeout(duration time.Duration) (buf.MultiBuffer, error) {
-	err := c.SetReadDeadline(time.Now().Add(duration))
-	if err != nil {
-		return nil, err
-	}
-	defer c.SetReadDeadline(time.Time{})
-	return c.ReadMultiBuffer()
-}
-
-func (c *Conn) WriteMultiBuffer(bufferList buf.MultiBuffer) error {
-	defer buf.ReleaseMulti(bufferList)
-	if c.writer != nil {
-		bytesList := make([][]byte, len(bufferList))
-		for i, buffer := range bufferList {
-			bytesList[i] = buffer.Bytes()
-		}
-		return common.Error(bufio.WriteVectorised(c.writer, bytesList))
-	}
-	// Since this conn is only used by tun, we don't force buffer writes to merge.
-	for _, buffer := range bufferList {
-		_, err := c.Conn.Write(buffer.Bytes())
-		if err != nil {
-			return err
-		}
-	}
-	return nil
-}

go.mod

@@ -18,8 +18,6 @@ require (
 	github.com/pires/go-proxyproto v0.15.0
 	github.com/refraction-networking/utls v1.8.3-0.20260301010127-aa6edf4b11af
 	github.com/robfig/cron/v3 v3.0.1
-	github.com/sagernet/sing v0.5.1
-	github.com/sagernet/sing-shadowsocks v0.2.7
 	github.com/stretchr/testify v1.12.1
 	github.com/vishvananda/netlink v1.3.1
 	github.com/xtls/reality v0.0.0-20260908062103-8cdf7bf9c7f0

go.sum

@@ -76,10 +76,6 @@ github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
 github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
 github.com/rogpeppe/go-internal v1.16.0 h1:O9DK+vNMDVGLr2BeZqmpLeMjiMNkuXfcqntWbZV6S5g=
 github.com/rogpeppe/go-internal v1.16.0/go.mod h1:DrUVZyrJU+txYW5/1kwtXQSMFio52ZOxX7yM1VHvnxs=
-github.com/sagernet/sing v0.5.1 h1:mhL/MZVq0TjuvHcpYcFtmSD1BFOxZ/+8ofbNZcg1k1Y=
-github.com/sagernet/sing v0.5.1/go.mod h1:ARkL0gM13/Iv5VCZmci/NuoOlePoIsW0m7BWfln/Hak=
-github.com/sagernet/sing-shadowsocks v0.2.7 h1:zaopR1tbHEw5Nk6FAkM05wCslV6ahVegEZaKMv9ipx8=
-github.com/sagernet/sing-shadowsocks v0.2.7/go.mod h1:0rIKJZBR65Qi0zwdKezt4s57y/Tl1ofkaq6NlkzVuyE=
 github.com/stretchr/testify v1.12.1 h1:EuwCh5fleGS7H32xRwO3wRGT7DxrDhLAT6FF8MpWDWE=
 github.com/stretchr/testify v1.12.1/go.mod h1:MDEgiDPPsNp5cuIrHPPCyornHKgEVbtFUmoNlxoYthg=
 github.com/vishvananda/netlink v1.3.1 h1:3AEMt62VKqz90r0tmNhog0r/PpWKmrEShJU0wJW6bV0=

infra/conf/shadowsocks.go

@@ -3,8 +3,6 @@ package conf
 import (
 	"strings"
 
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
-	C "github.com/sagernet/sing/common"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/protocol"
 	"github.com/xtls/xray-core/common/serial"
@@ -55,7 +53,7 @@ func (v *ShadowsocksServerConfig) Build() (proto.Message, error) {
 		v.Users = v.Clients
 	}
 
-	if C.Contains(shadowaead_2022.List, v.Cipher) {
+	if shadowsocks_2022.IsSupportedMethod(v.Cipher) {
 		return buildShadowsocks2022(v)
 	}
 
@@ -216,7 +214,7 @@ func (v *ShadowsocksClientConfig) Build() (proto.Message, error) {
 
 	if len(v.Servers) == 1 {
 		server := v.Servers[0]
-		if C.Contains(shadowaead_2022.List, server.Cipher) {
+		if shadowsocks_2022.IsSupportedMethod(server.Cipher) {
 			if server.Address == nil {
 				return nil, errors.New("Shadowsocks server address is not set.")
 			}
@@ -238,7 +236,7 @@ func (v *ShadowsocksClientConfig) Build() (proto.Message, error) {
 
 	config := new(shadowsocks.ClientConfig)
 	for _, server := range v.Servers {
-		if C.Contains(shadowaead_2022.List, server.Cipher) {
+		if shadowsocks_2022.IsSupportedMethod(server.Cipher) {
 			return nil, errors.New("Shadowsocks 2022 accept no multi servers")
 		}
 		if server.Address == nil {

proxy/shadowsocks_2022/cipher.go

@@ -0,0 +1,59 @@
+package shadowsocks_2022
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"errors"
+
+	"golang.org/x/crypto/chacha20poly1305"
+)
+
+type CipherMethod struct {
+	Name          string
+	KeySaltLength int
+	IsChaCha      bool
+}
+
+var (
+	cipherAES128GCM        = &CipherMethod{Name: MethodAES128GCM, KeySaltLength: 16, IsChaCha: false}
+	cipherAES256GCM        = &CipherMethod{Name: MethodAES256GCM, KeySaltLength: 32, IsChaCha: false}
+	cipherChaCha20Poly1305 = &CipherMethod{Name: MethodChaCha20Poly1305, KeySaltLength: 32, IsChaCha: true}
+)
+
+func GetCipherMethod(name string) (*CipherMethod, error) {
+	switch name {
+	case MethodAES128GCM:
+		return cipherAES128GCM, nil
+	case MethodAES256GCM:
+		return cipherAES256GCM, nil
+	case MethodChaCha20Poly1305:
+		return cipherChaCha20Poly1305, nil
+	default:
+		return nil, errors.New("unknown shadowsocks 2022 method")
+	}
+}
+
+// NewAEAD creates standard stream AEAD cipher instance (AES-GCM or ChaCha20-Poly1305)
+func (m *CipherMethod) NewAEAD(key []byte) (cipher.AEAD, error) {
+	if m.IsChaCha {
+		return chacha20poly1305.New(key)
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return cipher.NewGCM(block)
+}
+
+// NewBlock creates standard 16-byte block cipher for AES header encryption/decryption
+func (m *CipherMethod) NewBlock(key []byte) (cipher.Block, error) {
+	return aes.NewCipher(key)
+}
+
+// NewUDPCipher creates AEAD cipher for UDP packets (XChaCha20-Poly1305 with 24-byte nonce)
+func (m *CipherMethod) NewUDPCipher(key []byte) (cipher.AEAD, error) {
+	if m.IsChaCha {
+		return chacha20poly1305.NewX(key)
+	}
+	return nil, errors.New("shadowsocks-2022: udp separate AEAD cipher only available for chacha20 method")
+}

proxy/shadowsocks_2022/config.go

@@ -1,6 +1,9 @@
 package shadowsocks_2022
 
 import (
+	"bytes"
+	"encoding/base64"
+
 	"google.golang.org/protobuf/proto"
 
 	"github.com/xtls/xray-core/common/protocol"
@@ -8,26 +11,31 @@ import (
 
 // MemoryAccount is an account type converted from Account.
 type MemoryAccount struct {
-	Key string
+	Key []byte
 }
 
 // AsAccount implements protocol.AsAccount.
 func (u *Account) AsAccount() (protocol.Account, error) {
+	keyStr := u.GetKey()
+	raw, err := base64.StdEncoding.DecodeString(keyStr)
+	if err != nil {
+		raw = []byte(keyStr)
+	}
 	return &MemoryAccount{
-		Key: u.GetKey(),
+		Key: raw,
 	}, nil
 }
 
 // Equals implements protocol.Account.Equals().
 func (a *MemoryAccount) Equals(another protocol.Account) bool {
 	if account, ok := another.(*MemoryAccount); ok {
-		return a.Key == account.Key
+		return bytes.Equal(a.Key, account.Key)
 	}
 	return false
 }
 
 func (a *MemoryAccount) ToProto() proto.Message {
 	return &Account{
-		Key: a.Key,
+		Key: base64.StdEncoding.EncodeToString(a.Key),
 	}
 }

proxy/shadowsocks_2022/inbound.go

@@ -2,17 +2,11 @@ package shadowsocks_2022
 
 import (
 	"context"
+	"io"
 	"time"
 
-	shadowsocks "github.com/sagernet/sing-shadowsocks"
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
-	C "github.com/sagernet/sing/common"
-	B "github.com/sagernet/sing/common/buf"
-	"github.com/sagernet/sing/common/bufio"
-	E "github.com/sagernet/sing/common/exceptions"
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
 	"github.com/xtls/xray-core/common"
+	"github.com/xtls/xray-core/common/antireplay"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/log"
@@ -20,7 +14,10 @@ import (
 	"github.com/xtls/xray-core/common/protocol"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/common/singbridge"
+	"github.com/xtls/xray-core/common/task"
+	"github.com/xtls/xray-core/common/utils"
+	"github.com/xtls/xray-core/core"
+	"github.com/xtls/xray-core/features/policy"
 	"github.com/xtls/xray-core/features/routing"
 	"github.com/xtls/xray-core/transport/internet/stat"
 )
@@ -32,10 +29,13 @@ func init() {
 }
 
 type Inbound struct {
-	networks []net.Network
-	service  shadowsocks.Service
-	email    string
-	level    int
+	networks      []net.Network
+	method        *CipherMethod
+	psk           []byte
+	user          *protocol.MemoryUser
+	saltFilter    *antireplay.ReplayFilter[[32]byte]
+	udpCodec      *UDPServerCodec
+	policyManager policy.Manager
 }
 
 func NewServer(ctx context.Context, config *ServerConfig) (*Inbound, error) {
@@ -46,20 +46,35 @@ func NewServer(ctx context.Context, config *ServerConfig) (*Inbound, error) {
 			net.Network_UDP,
 		}
 	}
-	inbound := &Inbound{
-		networks: networks,
-		email:    config.Email,
-		level:    int(config.Level),
-	}
-	if !C.Contains(shadowaead_2022.List, config.Method) {
-		return nil, errors.New("unsupported method ", config.Method)
-	}
-	service, err := shadowaead_2022.NewServiceWithPassword(config.Method, config.Key, 500, inbound, nil)
+
+	method, err := GetCipherMethod(config.Method)
 	if err != nil {
-		return nil, errors.New("create service").Base(err)
+		return nil, errors.New("unsupported method: ", config.Method).Base(err)
 	}
-	inbound.service = service
-	return inbound, nil
+
+	psk, err := ParseKey(config.Key, method.KeySaltLength)
+	if err != nil {
+		return nil, err
+	}
+
+	udpCodec, err := NewUDPServerCodec(method, psk, 500*time.Second)
+	if err != nil {
+		return nil, err
+	}
+
+	v := core.MustFromContext(ctx)
+	return &Inbound{
+		networks:   networks,
+		method:     method,
+		psk:        psk,
+		saltFilter: antireplay.NewMapFilter[[32]byte](60),
+		user: &protocol.MemoryUser{
+			Email: config.Email,
+			Level: uint32(config.Level),
+		},
+		udpCodec:      udpCodec,
+		policyManager: v.GetFeature(policy.ManagerType()).(policy.Manager),
+	}, nil
 }
 
 func (i *Inbound) Network() []net.Network {
@@ -70,114 +85,181 @@ func (i *Inbound) Process(ctx context.Context, network net.Network, connection s
 	inbound := session.InboundFromContext(ctx)
 	inbound.Name = "shadowsocks-2022"
 	inbound.CanSpliceCopy = 3
-
-	var metadata M.Metadata
-	if inbound.Source.IsValid() {
-		metadata.Source = M.ParseSocksaddr(inbound.Source.NetAddr())
-	}
-
-	ctx = session.ContextWithDispatcher(ctx, dispatcher)
+	inbound.User = i.user
 
 	if network == net.Network_TCP {
-		return singbridge.ReturnError(i.service.NewConnection(ctx, connection, metadata))
-	} else {
-		reader := buf.NewReader(connection)
-		pc := &natPacketConn{connection}
-		for {
-			mb, err := reader.ReadMultiBuffer()
+		return i.processTCP(ctx, connection, dispatcher)
+	}
+	return i.processUDP(ctx, connection, dispatcher)
+}
+
+func (i *Inbound) processTCP(ctx context.Context, conn net.Conn, dispatcher routing.Dispatcher) error {
+	defer conn.Close()
+
+	sessionPolicy := i.policyManager.ForLevel(0)
+	if err := conn.SetReadDeadline(time.Now().Add(sessionPolicy.Timeouts.Handshake)); err != nil {
+		return errors.New("unable to set read deadline").Base(err).AtWarning()
+	}
+
+	var salt [32]byte
+	saltSlice := salt[:i.method.KeySaltLength]
+	if _, err := io.ReadFull(conn, saltSlice); err != nil {
+		return err
+	}
+
+	if !i.saltFilter.Check(salt) {
+		return ErrSaltNotUnique
+	}
+
+	sessionKey := DeriveSessionSubKey(i.psk, saltSlice, i.method.KeySaltLength)
+	aead, err := i.method.NewAEAD(sessionKey)
+	if err != nil {
+		return err
+	}
+
+	reader := NewStreamReader(conn, aead)
+
+	reqHeader, err := ReadClientRequestHeader(conn, reader)
+	if err != nil {
+		return err
+	}
+	_ = conn.SetReadDeadline(time.Time{})
+	dest := reqHeader.Destination
+
+	writer, err := WriteTCPResponse(conn, i.method, i.psk, saltSlice, nil)
+	if err != nil {
+		return err
+	}
+
+	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
+		From:   conn.RemoteAddr(),
+		To:     dest,
+		Status: log.AccessAccepted,
+		Email:  i.user.Email,
+	})
+
+	errors.LogInfo(ctx, "tunneling request to ", dest)
+
+	link, err := dispatcher.Dispatch(ctx, dest)
+	if err != nil {
+		return err
+	}
+
+	if len(reqHeader.EarlyData) > 0 {
+		earlyBuf := buf.New()
+		earlyBuf.Write(reqHeader.EarlyData)
+		if err := link.Writer.WriteMultiBuffer(buf.MultiBuffer{earlyBuf}); err != nil {
+			return err
+		}
+	}
+
+	sessionPolicy = i.policyManager.ForLevel(uint32(i.user.Level))
+	ctx, cancel := context.WithCancel(ctx)
+	timer := signal.CancelAfterInactivity(ctx, cancel, sessionPolicy.Timeouts.ConnectionIdle)
+	ctx = policy.ContextWithBufferPolicy(ctx, sessionPolicy.Buffer)
+
+	requestDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.DownlinkOnly)
+		return buf.Copy(reader, link.Writer, buf.UpdateActivity(timer))
+	}
+
+	responseDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.UplinkOnly)
+		return buf.Copy(link.Reader, writer, buf.UpdateActivity(timer))
+	}
+
+	responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+	return task.Run(ctx, requestDone, responseDoneAndCloseWriter)
+}
+
+func (i *Inbound) processUDP(ctx context.Context, conn stat.Connection, dispatcher routing.Dispatcher) error {
+	udpConns := utils.NewTypedSyncMap[uint64, *udpConnEntry]()
+	defer func() {
+		udpConns.Range(func(key uint64, entry *udpConnEntry) bool {
+			entry.timer.SetTimeout(0)
+			return true
+		})
+	}()
+
+	reader := buf.NewReader(conn)
+	for {
+		mb, err := reader.ReadMultiBuffer()
+		if err != nil {
+			buf.ReleaseMulti(mb)
+			return err
+		}
+
+		for _, b := range mb {
+			decoded, err := i.udpCodec.DecodePacket(b.Bytes())
 			if err != nil {
-				buf.ReleaseMulti(mb)
-				return singbridge.ReturnError(err)
+				b.Release()
+				continue
 			}
-			for _, buffer := range mb {
-				packet := B.As(buffer.Bytes()).ToOwned()
-				buffer.Release()
-				err = i.service.NewPacket(ctx, pc, packet, metadata)
+
+			entry, ok := udpConns.Load(decoded.SessionID)
+			if !ok {
+				sessCtx, cancel := context.WithCancel(ctx)
+				sessCtx = log.ContextWithAccessMessage(sessCtx, &log.AccessMessage{
+					From:   conn.RemoteAddr(),
+					To:     decoded.Destination,
+					Status: log.AccessAccepted,
+					Email:  i.user.Email,
+				})
+
+				link, err := dispatcher.Dispatch(sessCtx, decoded.Destination)
 				if err != nil {
-					packet.Release()
-					buf.ReleaseMulti(mb)
-					return err
+					cancel()
+					b.Release()
+					continue
+				}
+
+				newEntry := &udpConnEntry{
+					link:   link,
+					cancel: cancel,
+				}
+				sessionPolicy := i.policyManager.ForLevel(uint32(i.user.Level))
+				newEntry.timer = signal.CancelAfterInactivity(sessCtx, func() {
+					udpConns.Delete(decoded.SessionID)
+					common.Interrupt(link.Reader)
+					common.Interrupt(link.Writer)
+					cancel()
+				}, sessionPolicy.Timeouts.ConnectionIdle)
+
+				actual, loaded := udpConns.LoadOrStore(decoded.SessionID, newEntry)
+				if loaded {
+					// Another goroutine/packet beat us to storing, terminate our redundant link
+					newEntry.timer.SetTimeout(0)
+					entry = actual
+				} else {
+					entry = newEntry
+					go func(sessID uint64, dest net.Destination, cEntry *udpConnEntry) {
+						defer func() {
+							cEntry.timer.SetTimeout(0)
+						}()
+						for {
+							resMb, err := cEntry.link.Reader.ReadMultiBuffer()
+							if err != nil {
+								return
+							}
+							cEntry.timer.Update()
+							for _, rb := range resMb {
+								encPacket, err := i.udpCodec.EncodePacket(sessID, dest, rb.Bytes())
+								rb.Release()
+								if err != nil {
+									continue
+								}
+								_, _ = conn.Write(encPacket)
+							}
+						}
+					}(decoded.SessionID, decoded.Destination, entry)
 				}
 			}
+
+			entry.timer.Update()
+			payloadBuf := buf.New()
+			payloadBuf.Write(decoded.Payload)
+			b.Release()
+			_ = entry.link.Writer.WriteMultiBuffer(buf.MultiBuffer{payloadBuf})
 		}
 	}
 }
-
-func (i *Inbound) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	inbound.User = &protocol.MemoryUser{
-		Email: i.email,
-		Level: uint32(i.level),
-	}
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  i.email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to tcp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_TCP)
-	if err != nil {
-		return err
-	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	return singbridge.CopyConn(ctx, nil, link, conn)
-}
-
-func (i *Inbound) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	inbound.User = &protocol.MemoryUser{
-		Email: i.email,
-		Level: uint32(i.level),
-	}
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  i.email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to udp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_UDP)
-	if err != nil {
-		return err
-	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	outConn := &singbridge.PacketConnWrapper{
-		Reader: link.Reader,
-		Writer: link.Writer,
-		Dest:   destination,
-		T: signal.CancelAfterInactivity(ctx, func() {
-			common.Interrupt(link.Reader)
-		}, 300*time.Second),
-	}
-	return bufio.CopyPacketConn(ctx, conn, outConn)
-}
-
-func (i *Inbound) NewError(ctx context.Context, err error) {
-	if E.IsClosed(err) {
-		return
-	}
-	errors.LogWarning(ctx, err.Error())
-}
-
-type natPacketConn struct {
-	net.Conn
-}
-
-func (c *natPacketConn) ReadPacket(buffer *B.Buffer) (addr M.Socksaddr, err error) {
-	_, err = buffer.ReadFrom(c)
-	return
-}
-
-func (c *natPacketConn) WritePacket(buffer *B.Buffer, addr M.Socksaddr) error {
-	_, err := buffer.WriteTo(c)
-	return err
-}

proxy/shadowsocks_2022/inbound_multi.go

@@ -2,21 +2,17 @@ package shadowsocks_2022
 
 import (
 	"context"
-	"encoding/base64"
+	"crypto/cipher"
+	"encoding/binary"
+	"io"
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
-	C "github.com/sagernet/sing/common"
-	A "github.com/sagernet/sing/common/auth"
-	B "github.com/sagernet/sing/common/buf"
-	"github.com/sagernet/sing/common/bufio"
-	E "github.com/sagernet/sing/common/exceptions"
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
 	"github.com/xtls/xray-core/common"
+	"github.com/xtls/xray-core/common/antireplay"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/log"
@@ -24,8 +20,11 @@ import (
 	"github.com/xtls/xray-core/common/protocol"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/common/singbridge"
+	"github.com/xtls/xray-core/common/task"
+	"github.com/xtls/xray-core/common/utils"
 	"github.com/xtls/xray-core/common/uuid"
+	"github.com/xtls/xray-core/core"
+	"github.com/xtls/xray-core/features/policy"
 	"github.com/xtls/xray-core/features/routing"
 	"github.com/xtls/xray-core/transport/internet/stat"
 )
@@ -38,9 +37,16 @@ func init() {
 
 type MultiUserInbound struct {
 	sync.Mutex
-	networks []net.Network
-	users    []*protocol.MemoryUser
-	service  *shadowaead_2022.MultiService[int]
+	networks        []net.Network
+	method          *CipherMethod
+	masterPSK       []byte
+	usersByHash     *utils.TypedSyncMap[[AESBlockSize]byte, *protocol.MemoryUser]
+	usersByEmail    *utils.TypedSyncMap[string, *protocol.MemoryUser]
+	userCount       atomic.Int64
+	saltFilter      *antireplay.ReplayFilter[[32]byte]
+	udpSessions     *UDPSessionManager
+	udpMasterCipher cipher.Block
+	policyManager   policy.Manager
 }
 
 func NewMultiServer(ctx context.Context, config *MultiUserServerConfig) (*MultiUserInbound, error) {
@@ -51,138 +57,131 @@ func NewMultiServer(ctx context.Context, config *MultiUserServerConfig) (*MultiU
 			net.Network_UDP,
 		}
 	}
-	memUsers := []*protocol.MemoryUser{}
-	for i, user := range config.Users {
+
+	method, err := GetCipherMethod(config.Method)
+	if err != nil {
+		return nil, err
+	}
+	if method.IsChaCha {
+		return nil, errors.New("shadowsocks 2022 multi-user: only aes methods are supported")
+	}
+
+	masterPSK, err := ParseKey(config.Key, method.KeySaltLength)
+	if err != nil {
+		return nil, err
+	}
+
+	masterBlock, err := method.NewBlock(masterPSK)
+	if err != nil {
+		return nil, err
+	}
+
+	v := core.MustFromContext(ctx)
+	i := &MultiUserInbound{
+		networks:        networks,
+		method:          method,
+		masterPSK:       masterPSK,
+		usersByHash:     utils.NewTypedSyncMap[[AESBlockSize]byte, *protocol.MemoryUser](),
+		usersByEmail:    utils.NewTypedSyncMap[string, *protocol.MemoryUser](),
+		saltFilter:      antireplay.NewMapFilter[[32]byte](60),
+		udpSessions:     NewUDPSessionManager(500 * time.Second),
+		udpMasterCipher: masterBlock,
+		policyManager:   v.GetFeature(policy.ManagerType()).(policy.Manager),
+	}
+
+	for idx, user := range config.Users {
 		if user.Email == "" {
 			u := uuid.New()
-			user.Email = "unnamed-user-" + strconv.Itoa(i) + "-" + u.String()
+			user.Email = "unnamed-user-" + strconv.Itoa(idx) + "-" + u.String()
 		}
-		u, err := user.ToMemoryUser()
+		memUser, err := user.ToMemoryUser()
 		if err != nil {
-			return nil, errors.New("failed to get shadowsocks user").Base(err).AtError()
+			return nil, errors.New("failed to parse shadowsocks user").Base(err)
+		}
+		if err := i.AddUser(ctx, memUser); err != nil {
+			return nil, err
 		}
-		memUsers = append(memUsers, u)
 	}
 
-	inbound := &MultiUserInbound{
-		networks: networks,
-		users:    memUsers,
-	}
-	if config.Key == "" {
-		return nil, errors.New("missing key")
-	}
-	psk, err := base64.StdEncoding.DecodeString(config.Key)
-	if err != nil {
-		return nil, errors.New("parse config").Base(err)
-	}
-	service, err := shadowaead_2022.NewMultiService[int](config.Method, psk, 500, inbound, nil)
-	if err != nil {
-		return nil, errors.New("create service").Base(err)
-	}
-	err = service.UpdateUsersWithPasswords(
-		C.MapIndexed(memUsers, func(index int, it *protocol.MemoryUser) int { return index }),
-		C.Map(memUsers, func(it *protocol.MemoryUser) string { return it.Account.(*MemoryAccount).Key }),
-	)
-	if err != nil {
-		return nil, errors.New("create service").Base(err)
-	}
-
-	inbound.service = service
-	return inbound, nil
+	return i, nil
 }
 
-// AddUser implements proxy.UserManager.AddUser().
+// AddUser implements proxy.UserManager.AddUser()
 func (i *MultiUserInbound) AddUser(ctx context.Context, u *protocol.MemoryUser) error {
 	i.Lock()
 	defer i.Unlock()
 
+	var emailKey string
 	if u.Email != "" {
-		for idx := range i.users {
-			if i.users[idx].Email == u.Email {
-				return errors.New("User ", u.Email, " already exists.")
-			}
+		emailKey = strings.ToLower(u.Email)
+		if _, exists := i.usersByEmail.Load(emailKey); exists {
+			return errors.New("user ", u.Email, " already exists")
 		}
 	}
-	i.users = append(i.users, u)
 
-	// sync to multi service
-	// Considering implements shadowsocks2022 in xray-core may have better performance.
-	i.service.UpdateUsersWithPasswords(
-		C.MapIndexed(i.users, func(index int, it *protocol.MemoryUser) int { return index }),
-		C.Map(i.users, func(it *protocol.MemoryUser) string { return it.Account.(*MemoryAccount).Key }),
-	)
+	memAcc, ok := u.Account.(*MemoryAccount)
+	if !ok {
+		return errors.New("missing or invalid user account")
+	}
+
+	if len(memAcc.Key) != i.method.KeySaltLength {
+		return ErrBadKey
+	}
+
+	pskHash := DeriveUserPSKHash(memAcc.Key)
+	i.usersByHash.Store(pskHash, u)
+	if emailKey != "" {
+		i.usersByEmail.Store(emailKey, u)
+	}
+	i.userCount.Add(1)
 
 	return nil
 }
 
-// RemoveUser implements proxy.UserManager.RemoveUser().
+// RemoveUser implements proxy.UserManager.RemoveUser()
 func (i *MultiUserInbound) RemoveUser(ctx context.Context, email string) error {
 	if email == "" {
-		return errors.New("Email must not be empty.")
+		return errors.New("email must not be empty")
 	}
 
 	i.Lock()
 	defer i.Unlock()
 
-	idx := -1
-	for ii, u := range i.users {
-		if strings.EqualFold(u.Email, email) {
-			idx = ii
-			break
-		}
+	emailKey := strings.ToLower(email)
+	u, loaded := i.usersByEmail.LoadAndDelete(emailKey)
+	if !loaded {
+		return errors.New("user ", email, " not found")
 	}
 
-	if idx == -1 {
-		return errors.New("User ", email, " not found.")
-	}
-
-	ulen := len(i.users)
-
-	i.users[idx] = i.users[ulen-1]
-	i.users[ulen-1] = nil
-	i.users = i.users[:ulen-1]
-
-	// sync to multi service
-	// Considering implements shadowsocks2022 in xray-core may have better performance.
-	i.service.UpdateUsersWithPasswords(
-		C.MapIndexed(i.users, func(index int, it *protocol.MemoryUser) int { return index }),
-		C.Map(i.users, func(it *protocol.MemoryUser) string { return it.Account.(*MemoryAccount).Key }),
-	)
+	pskHash := DeriveUserPSKHash(u.Account.(*MemoryAccount).Key)
+	i.usersByHash.Delete(pskHash)
+	i.userCount.Add(-1)
 
 	return nil
 }
 
-// GetUser implements proxy.UserManager.GetUser().
+// GetUser implements proxy.UserManager.GetUser()
 func (i *MultiUserInbound) GetUser(ctx context.Context, email string) *protocol.MemoryUser {
 	if email == "" {
 		return nil
 	}
-
-	i.Lock()
-	defer i.Unlock()
-
-	for _, u := range i.users {
-		if strings.EqualFold(u.Email, email) {
-			return u
-		}
-	}
-	return nil
+	u, _ := i.usersByEmail.Load(strings.ToLower(email))
+	return u
 }
 
-// GetUsers implements proxy.UserManager.GetUsers().
+// GetUsers implements proxy.UserManager.GetUsers()
 func (i *MultiUserInbound) GetUsers(ctx context.Context) []*protocol.MemoryUser {
-	i.Lock()
-	defer i.Unlock()
-	dst := make([]*protocol.MemoryUser, len(i.users))
-	copy(dst, i.users)
-	return dst
+	var users []*protocol.MemoryUser
+	i.usersByEmail.Range(func(_ string, user *protocol.MemoryUser) bool {
+		users = append(users, user)
+		return true
+	})
+	return users
 }
 
-// GetUsersCount implements proxy.UserManager.GetUsersCount().
+// GetUsersCount implements proxy.UserManager.GetUsersCount()
 func (i *MultiUserInbound) GetUsersCount(context.Context) int64 {
-	i.Lock()
-	defer i.Unlock()
-	return int64(len(i.users))
+	return i.userCount.Load()
 }
 
 func (i *MultiUserInbound) Network() []net.Network {
@@ -194,97 +193,319 @@ func (i *MultiUserInbound) Process(ctx context.Context, network net.Network, con
 	inbound.Name = "shadowsocks-2022-multi"
 	inbound.CanSpliceCopy = 3
 
-	var metadata M.Metadata
-	if inbound.Source.IsValid() {
-		metadata.Source = M.ParseSocksaddr(inbound.Source.NetAddr())
+	if network == net.Network_TCP {
+		return i.processTCP(ctx, connection, dispatcher)
+	}
+	return i.processUDP(ctx, connection, dispatcher)
+}
+
+func (i *MultiUserInbound) processTCP(ctx context.Context, conn net.Conn, dispatcher routing.Dispatcher) error {
+	defer conn.Close()
+
+	sessionPolicy := i.policyManager.ForLevel(0)
+	if err := conn.SetReadDeadline(time.Now().Add(sessionPolicy.Timeouts.Handshake)); err != nil {
+		return errors.New("unable to set read deadline").Base(err).AtWarning()
 	}
 
-	ctx = session.ContextWithDispatcher(ctx, dispatcher)
+	// 1. Read Request Salt (16 or 32 bytes)
+	var salt [32]byte
+	saltSlice := salt[:i.method.KeySaltLength]
+	if _, err := io.ReadFull(conn, saltSlice); err != nil {
+		return err
+	}
 
-	if network == net.Network_TCP {
-		return singbridge.ReturnError(i.service.NewConnection(ctx, connection, metadata))
-	} else {
-		reader := buf.NewReader(connection)
-		pc := &natPacketConn{connection}
-		for {
-			mb, err := reader.ReadMultiBuffer()
-			if err != nil {
-				buf.ReleaseMulti(mb)
-				return singbridge.ReturnError(err)
+	if !i.saltFilter.Check(salt) {
+		return ErrSaltNotUnique
+	}
+
+	// 2. Read Extended Identity Header (16 bytes)
+	var eih [AESBlockSize]byte
+	if _, err := io.ReadFull(conn, eih[:]); err != nil {
+		return err
+	}
+
+	// Decrypt EIH with IdentitySubKey derived from masterPSK and salt
+	identitySubkey := DeriveIdentitySubKey(i.masterPSK, saltSlice, i.method.KeySaltLength)
+	block, err := i.method.NewBlock(identitySubkey)
+	if err != nil {
+		return err
+	}
+
+	var decryptedHash [AESBlockSize]byte
+	block.Decrypt(decryptedHash[:], eih[:])
+
+	// Lookup user
+	user, ok := i.usersByHash.Load(decryptedHash)
+	if !ok || user == nil {
+		return ErrInvalidRequest
+	}
+	userPSK := user.Account.(*MemoryAccount).Key
+
+	// 3. Derive Session Subkey using matched user's PSK
+	sessionKey := DeriveSessionSubKey(userPSK, saltSlice, i.method.KeySaltLength)
+	aead, err := i.method.NewAEAD(sessionKey)
+	if err != nil {
+		return err
+	}
+
+	reader := NewStreamReader(conn, aead)
+
+	// 4 & 5. Read Client Request Header
+	reqHeader, err := ReadClientRequestHeader(conn, reader)
+	if err != nil {
+		return err
+	}
+	_ = conn.SetReadDeadline(time.Time{})
+	dest := reqHeader.Destination
+
+	// 6. Send Server Response Handshake
+	writer, err := WriteTCPResponse(conn, i.method, userPSK, saltSlice, nil)
+	if err != nil {
+		return err
+	}
+
+	// 7. Dispatch Connection to Xray routing with matched User
+	inbound := session.InboundFromContext(ctx)
+	inbound.User = user
+
+	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
+		From:   conn.RemoteAddr(),
+		To:     dest,
+		Status: log.AccessAccepted,
+		Email:  user.Email,
+	})
+
+	errors.LogInfo(ctx, "tunneling request to ", dest, " for user ", user.Email)
+
+	link, err := dispatcher.Dispatch(ctx, dest)
+	if err != nil {
+		return err
+	}
+
+	if len(reqHeader.EarlyData) > 0 {
+		earlyBuf := buf.New()
+		earlyBuf.Write(reqHeader.EarlyData)
+		if err := link.Writer.WriteMultiBuffer(buf.MultiBuffer{earlyBuf}); err != nil {
+			return err
+		}
+	}
+
+	sessionPolicy = i.policyManager.ForLevel(user.Level)
+	ctx, cancel := context.WithCancel(ctx)
+	timer := signal.CancelAfterInactivity(ctx, cancel, sessionPolicy.Timeouts.ConnectionIdle)
+	ctx = policy.ContextWithBufferPolicy(ctx, sessionPolicy.Buffer)
+
+	requestDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.DownlinkOnly)
+		return buf.Copy(reader, link.Writer, buf.UpdateActivity(timer))
+	}
+
+	responseDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.UplinkOnly)
+		return buf.Copy(link.Reader, writer, buf.UpdateActivity(timer))
+	}
+
+	responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+	return task.Run(ctx, requestDone, responseDoneAndCloseWriter)
+}
+
+func (i *MultiUserInbound) processUDP(ctx context.Context, conn stat.Connection, dispatcher routing.Dispatcher) error {
+	udpConns := utils.NewTypedSyncMap[uint64, *udpConnEntry]()
+	defer func() {
+		udpConns.Range(func(key uint64, entry *udpConnEntry) bool {
+			entry.timer.SetTimeout(0)
+			return true
+		})
+	}()
+
+	reader := buf.NewReader(conn)
+	for {
+		mb, err := reader.ReadMultiBuffer()
+		if err != nil {
+			buf.ReleaseMulti(mb)
+			return err
+		}
+
+		for _, b := range mb {
+			// In multi-user UDP:
+			// Packet header is 16 bytes: Encrypted(SessionID + PacketID)
+			// Followed by 16 bytes EIH
+			packetBytes := b.Bytes()
+			if len(packetBytes) < 32+1+8+2 {
+				b.Release()
+				continue
 			}
-			for _, buffer := range mb {
-				packet := B.As(buffer.Bytes()).ToOwned()
-				buffer.Release()
-				err = i.service.NewPacket(ctx, pc, packet, metadata)
+
+			var rawHeader [16]byte
+			i.udpMasterCipher.Decrypt(rawHeader[:], packetBytes[:16])
+
+			sessionID := binary.BigEndian.Uint64(rawHeader[:8])
+			packetID := binary.BigEndian.Uint64(rawHeader[8:16])
+
+			// Replay protection & session lookup
+			sessionItem, _ := i.udpSessions.GetOrCreate(sessionID)
+
+			sessionItem.Lock()
+			if !sessionItem.Window.Check(packetID) {
+				sessionItem.Unlock()
+				b.Release()
+				continue
+			}
+
+			var userPSK []byte
+			var currentUser *protocol.MemoryUser
+			if sessionItem.User != nil {
+				currentUser = sessionItem.User
+				userPSK = sessionItem.UserPSK
+				sessionItem.Unlock()
+			} else {
+				sessionItem.Unlock()
+				// Decrypt EIH
+				identitySubkey := DeriveIdentitySubKey(i.masterPSK, rawHeader[:8], i.method.KeySaltLength)
+				idBlock, err := i.method.NewBlock(identitySubkey)
 				if err != nil {
-					packet.Release()
-					buf.ReleaseMulti(mb)
-					return err
+					b.Release()
+					continue
+				}
+
+				var decryptedHash [16]byte
+				idBlock.Decrypt(decryptedHash[:], packetBytes[16:32])
+
+				user, ok := i.usersByHash.Load(decryptedHash)
+				if !ok || user == nil {
+					b.Release()
+					continue
+				}
+				currentUser = user
+				userPSK = user.Account.(*MemoryAccount).Key
+
+				sessionItem.Lock()
+				sessionItem.User = user
+				sessionItem.UserPSK = userPSK
+				sessionItem.Unlock()
+			}
+
+			// Decrypt Body (with AEAD caching per session)
+			bodyAead := sessionItem.GetRemoteCipher()
+			if bodyAead == nil {
+				bodyKey := DeriveSessionSubKey(userPSK, rawHeader[:8], i.method.KeySaltLength)
+				var err error
+				bodyAead, err = i.method.NewAEAD(bodyKey)
+				if err != nil {
+					b.Release()
+					continue
+				}
+				sessionItem.SetRemoteCipher(bodyAead)
+			}
+
+			bodyNonce := rawHeader[4:16]
+			bodyCipher := packetBytes[32:]
+			bodyPlain, err := bodyAead.Open(nil, bodyNonce, bodyCipher, nil)
+			b.Release()
+			if err != nil || len(bodyPlain) < 1+8+2 {
+				continue
+			}
+
+			sessionItem.Lock()
+			sessionItem.Window.Add(packetID)
+			sessionItem.Unlock()
+
+			if bodyPlain[0] != HeaderTypeClient {
+				continue
+			}
+			epoch := binary.BigEndian.Uint64(bodyPlain[1:9])
+			diff := time.Now().Unix() - int64(epoch)
+			if diff < -30 || diff > 30 {
+				continue
+			}
+
+			paddingLen := int(binary.BigEndian.Uint16(bodyPlain[9:11]))
+			offset := 11 + paddingLen
+			if len(bodyPlain) < offset {
+				continue
+			}
+
+			dest, addrLen, err := parseAddressPort(bodyPlain[offset:])
+			if err != nil {
+				continue
+			}
+
+			payload := bodyPlain[offset+addrLen:]
+			payloadCopy := make([]byte, len(payload))
+			copy(payloadCopy, payload)
+
+			entry, ok := udpConns.Load(sessionID)
+			if !ok {
+				sessCtx, cancel := context.WithCancel(ctx)
+				inbound := session.InboundFromContext(sessCtx)
+				inbound.User = currentUser
+
+				sessCtx = log.ContextWithAccessMessage(sessCtx, &log.AccessMessage{
+					From:   conn.RemoteAddr(),
+					To:     dest,
+					Status: log.AccessAccepted,
+					Email:  currentUser.Email,
+				})
+
+				link, err := dispatcher.Dispatch(sessCtx, dest)
+				if err != nil {
+					cancel()
+					continue
+				}
+
+				newEntry := &udpConnEntry{
+					link:   link,
+					cancel: cancel,
+				}
+				sessionPolicy := i.policyManager.ForLevel(currentUser.Level)
+				newEntry.timer = signal.CancelAfterInactivity(sessCtx, func() {
+					udpConns.Delete(sessionID)
+					common.Interrupt(link.Reader)
+					common.Interrupt(link.Writer)
+					cancel()
+				}, sessionPolicy.Timeouts.ConnectionIdle)
+
+				actual, loaded := udpConns.LoadOrStore(sessionID, newEntry)
+				if loaded {
+					newEntry.timer.SetTimeout(0)
+					entry = actual
+				} else {
+					entry = newEntry
+					go func(sessID uint64, uPSK []byte, d net.Destination, cEntry *udpConnEntry) {
+						defer func() {
+							cEntry.timer.SetTimeout(0)
+						}()
+						for {
+							resMb, err := cEntry.link.Reader.ReadMultiBuffer()
+							if err != nil {
+								return
+							}
+							cEntry.timer.Update()
+							for _, rb := range resMb {
+								encPacket, err := i.encodeServerUDPPacket(sessID, uPSK, d, rb.Bytes())
+								rb.Release()
+								if err != nil {
+									continue
+								}
+								_, _ = conn.Write(encPacket)
+							}
+						}
+					}(sessionID, userPSK, dest, entry)
 				}
 			}
+
+			entry.timer.Update()
+			pBuf := buf.New()
+			pBuf.Write(payloadCopy)
+			_ = entry.link.Writer.WriteMultiBuffer(buf.MultiBuffer{pBuf})
 		}
 	}
 }
 
-func (i *MultiUserInbound) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	userInt, _ := A.UserFromContext[int](ctx)
-	user := i.users[userInt]
-	inbound.User = user
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  user.Email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to tcp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_TCP)
-	if err != nil {
-		return err
+func (i *MultiUserInbound) encodeServerUDPPacket(clientSessionID uint64, userPSK []byte, dest net.Destination, payload []byte) ([]byte, error) {
+	sessionItem, _ := i.udpSessions.GetOrCreate(clientSessionID)
+	if err := sessionItem.EnsureServerState(i.method, i.udpMasterCipher, nil, userPSK); err != nil {
+		return nil, err
 	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	return singbridge.CopyConn(ctx, conn, link, conn)
-}
-
-func (i *MultiUserInbound) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	userInt, _ := A.UserFromContext[int](ctx)
-	user := i.users[userInt]
-	inbound.User = user
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  user.Email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to udp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_UDP)
-	if err != nil {
-		return err
-	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	outConn := &singbridge.PacketConnWrapper{
-		Reader: link.Reader,
-		Writer: link.Writer,
-		Dest:   destination,
-		T: signal.CancelAfterInactivity(ctx, func() {
-			common.Interrupt(link.Reader)
-		}, 300*time.Second),
-	}
-	return bufio.CopyPacketConn(ctx, conn, outConn)
-}
-
-func (i *MultiUserInbound) NewError(ctx context.Context, err error) {
-	if E.IsClosed(err) {
-		return
-	}
-	errors.LogWarning(ctx, err.Error())
+	return sessionItem.EncodeServerPacket(i.method, clientSessionID, dest, payload)
 }

proxy/shadowsocks_2022/inbound_relay.go

@@ -2,18 +2,12 @@ package shadowsocks_2022
 
 import (
 	"context"
+	"crypto/cipher"
+	"encoding/binary"
+	"io"
 	"strconv"
-	"strings"
 	"time"
 
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
-	C "github.com/sagernet/sing/common"
-	A "github.com/sagernet/sing/common/auth"
-	B "github.com/sagernet/sing/common/buf"
-	"github.com/sagernet/sing/common/bufio"
-	E "github.com/sagernet/sing/common/exceptions"
-	M "github.com/sagernet/sing/common/metadata"
-	N "github.com/sagernet/sing/common/network"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
@@ -22,8 +16,11 @@ import (
 	"github.com/xtls/xray-core/common/protocol"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/common/singbridge"
+	"github.com/xtls/xray-core/common/task"
+	"github.com/xtls/xray-core/common/utils"
 	"github.com/xtls/xray-core/common/uuid"
+	"github.com/xtls/xray-core/core"
+	"github.com/xtls/xray-core/features/policy"
 	"github.com/xtls/xray-core/features/routing"
 	"github.com/xtls/xray-core/transport/internet/stat"
 )
@@ -34,10 +31,22 @@ func init() {
 	}))
 }
 
+type relayDest struct {
+	destination net.Destination
+	email       string
+	level       uint32
+	key         []byte
+	blockCipher cipher.Block
+}
+
 type RelayInbound struct {
-	networks     []net.Network
-	destinations []*RelayDestination
-	service      *shadowaead_2022.RelayService[int]
+	networks        []net.Network
+	method          *CipherMethod
+	relayPSK        []byte
+	relayBlock      cipher.Block
+	destinations    map[[AESBlockSize]byte]*relayDest
+	rawDestinations []*RelayDestination
+	policyManager   policy.Manager
 }
 
 func NewRelayServer(ctx context.Context, config *RelayServerConfig) (*RelayInbound, error) {
@@ -48,39 +57,63 @@ func NewRelayServer(ctx context.Context, config *RelayServerConfig) (*RelayInbou
 			net.Network_UDP,
 		}
 	}
-	inbound := &RelayInbound{
-		networks:     networks,
-		destinations: config.Destinations,
-	}
-	if !C.Contains(shadowaead_2022.List, config.Method) || !strings.Contains(config.Method, "aes") {
-		return nil, errors.New("unsupported method ", config.Method)
-	}
-	service, err := shadowaead_2022.NewRelayServiceWithPassword[int](config.Method, config.Key, 500, inbound)
+
+	method, err := GetCipherMethod(config.Method)
 	if err != nil {
-		return nil, errors.New("create service").Base(err)
+		return nil, err
+	}
+	if method.IsChaCha {
+		return nil, errors.New("shadowsocks 2022 relay: only aes methods are supported")
 	}
 
-	for i, destination := range config.Destinations {
-		if destination.Email == "" {
+	relayPSK, err := ParseKey(config.Key, method.KeySaltLength)
+	if err != nil {
+		return nil, err
+	}
+
+	relayBlock, err := method.NewBlock(relayPSK)
+	if err != nil {
+		return nil, err
+	}
+
+	v := core.MustFromContext(ctx)
+	i := &RelayInbound{
+		networks:        networks,
+		method:          method,
+		relayPSK:        relayPSK,
+		relayBlock:      relayBlock,
+		destinations:    make(map[[AESBlockSize]byte]*relayDest),
+		rawDestinations: config.Destinations,
+		policyManager:   v.GetFeature(policy.ManagerType()).(policy.Manager),
+	}
+
+	for idx, d := range config.Destinations {
+		if d.Email == "" {
 			u := uuid.New()
-			destination.Email = "unnamed-destination-" + strconv.Itoa(i) + "-" + u.String()
+			d.Email = "unnamed-destination-" + strconv.Itoa(idx) + "-" + u.String()
+		}
+		destKey, err := ParseKey(d.Key, method.KeySaltLength)
+		if err != nil {
+			return nil, err
+		}
+
+		destBlock, err := method.NewBlock(destKey)
+		if err != nil {
+			return nil, err
+		}
+
+		hash := DeriveUserPSKHash(destKey)
+
+		i.destinations[hash] = &relayDest{
+			destination: net.TCPDestination(d.Address.AsAddress(), net.Port(d.Port)),
+			email:       d.Email,
+			level:       uint32(d.Level),
+			key:         destKey,
+			blockCipher: destBlock,
 		}
 	}
-	err = service.UpdateUsersWithPasswords(
-		C.MapIndexed(config.Destinations, func(index int, it *RelayDestination) int { return index }),
-		C.Map(config.Destinations, func(it *RelayDestination) string { return it.Key }),
-		C.Map(config.Destinations, func(it *RelayDestination) M.Socksaddr {
-			return singbridge.ToSocksaddr(net.Destination{
-				Address: it.Address.AsAddress(),
-				Port:    net.Port(it.Port),
-			})
-		}),
-	)
-	if err != nil {
-		return nil, errors.New("create service").Base(err)
-	}
-	inbound.service = service
-	return inbound, nil
+
+	return i, nil
 }
 
 func (i *RelayInbound) Network() []net.Network {
@@ -92,103 +125,206 @@ func (i *RelayInbound) Process(ctx context.Context, network net.Network, connect
 	inbound.Name = "shadowsocks-2022-relay"
 	inbound.CanSpliceCopy = 3
 
-	var metadata M.Metadata
-	if inbound.Source.IsValid() {
-		metadata.Source = M.ParseSocksaddr(inbound.Source.NetAddr())
+	if network == net.Network_TCP {
+		return i.processTCP(ctx, connection, dispatcher)
+	}
+	return i.processUDP(ctx, connection, dispatcher)
+}
+
+func (i *RelayInbound) processTCP(ctx context.Context, conn net.Conn, dispatcher routing.Dispatcher) error {
+	defer conn.Close()
+
+	sessionPolicy := i.policyManager.ForLevel(0)
+	if err := conn.SetReadDeadline(time.Now().Add(sessionPolicy.Timeouts.Handshake)); err != nil {
+		return errors.New("unable to set read deadline").Base(err).AtWarning()
 	}
 
-	ctx = session.ContextWithDispatcher(ctx, dispatcher)
+	// Read Salt + Outer EIH
+	needed := i.method.KeySaltLength + AESBlockSize
+	var headerBuf [48]byte
+	headerSlice := headerBuf[:needed]
+	if _, err := io.ReadFull(conn, headerSlice); err != nil {
+		return err
+	}
 
-	if network == net.Network_TCP {
-		return singbridge.ReturnError(i.service.NewConnection(ctx, connection, metadata))
-	} else {
-		reader := buf.NewReader(connection)
-		pc := &natPacketConn{connection}
-		for {
-			mb, err := reader.ReadMultiBuffer()
-			if err != nil {
-				buf.ReleaseMulti(mb)
-				return singbridge.ReturnError(err)
+	salt := headerSlice[:i.method.KeySaltLength]
+	eih := headerSlice[i.method.KeySaltLength:]
+
+	identitySubkey := DeriveIdentitySubKey(i.relayPSK, salt, i.method.KeySaltLength)
+	block, err := i.method.NewBlock(identitySubkey)
+	if err != nil {
+		return err
+	}
+
+	var decryptedHash [AESBlockSize]byte
+	block.Decrypt(decryptedHash[:], eih)
+
+	targetDest, ok := i.destinations[decryptedHash]
+	if !ok {
+		return ErrInvalidRequest
+	}
+	_ = conn.SetReadDeadline(time.Time{})
+
+	inbound := session.InboundFromContext(ctx)
+	inbound.User = &protocol.MemoryUser{
+		Email: targetDest.email,
+		Level: targetDest.level,
+	}
+
+	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
+		From:   conn.RemoteAddr(),
+		To:     targetDest.destination,
+		Status: log.AccessAccepted,
+		Email:  targetDest.email,
+	})
+
+	errors.LogInfo(ctx, "relaying connection to ", targetDest.destination)
+
+	link, err := dispatcher.Dispatch(ctx, targetDest.destination)
+	if err != nil {
+		return err
+	}
+
+	// Unwrap outer EIH: send client salt to next hop, stripping this hop's EIH
+	saltBuf := buf.New()
+	saltBuf.Write(salt)
+	if err := link.Writer.WriteMultiBuffer(buf.MultiBuffer{saltBuf}); err != nil {
+		return err
+	}
+
+	sessionPolicy = i.policyManager.ForLevel(targetDest.level)
+	ctx, cancel := context.WithCancel(ctx)
+	timer := signal.CancelAfterInactivity(ctx, cancel, sessionPolicy.Timeouts.ConnectionIdle)
+	ctx = policy.ContextWithBufferPolicy(ctx, sessionPolicy.Buffer)
+
+	requestDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.DownlinkOnly)
+		return buf.Copy(buf.NewReader(conn), link.Writer, buf.UpdateActivity(timer))
+	}
+
+	responseDone := func() error {
+		defer timer.SetTimeout(sessionPolicy.Timeouts.UplinkOnly)
+		return buf.Copy(link.Reader, buf.NewWriter(conn), buf.UpdateActivity(timer))
+	}
+
+	responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+	return task.Run(ctx, requestDone, responseDoneAndCloseWriter)
+}
+
+func (i *RelayInbound) processUDP(ctx context.Context, conn stat.Connection, dispatcher routing.Dispatcher) error {
+	udpConns := utils.NewTypedSyncMap[uint64, *udpConnEntry]()
+	defer func() {
+		udpConns.Range(func(key uint64, entry *udpConnEntry) bool {
+			entry.timer.SetTimeout(0)
+			return true
+		})
+	}()
+
+	reader := buf.NewReader(conn)
+	for {
+		mb, err := reader.ReadMultiBuffer()
+		if err != nil {
+			buf.ReleaseMulti(mb)
+			return err
+		}
+
+		for _, b := range mb {
+			data := b.Bytes()
+			if len(data) < 2*AESBlockSize {
+				b.Release()
+				continue
 			}
-			for _, buffer := range mb {
-				packet := B.As(buffer.Bytes()).ToOwned()
-				buffer.Release()
-				err = i.service.NewPacket(ctx, pc, packet, metadata)
+
+			var packetHeader [AESBlockSize]byte
+			i.relayBlock.Decrypt(packetHeader[:], data[:AESBlockSize])
+
+			var eiHeader [AESBlockSize]byte
+			i.relayBlock.Decrypt(eiHeader[:], data[AESBlockSize:2*AESBlockSize])
+			for idx := 0; idx < AESBlockSize; idx++ {
+				eiHeader[idx] ^= packetHeader[idx]
+			}
+
+			targetDest, ok := i.destinations[eiHeader]
+			if !ok {
+				b.Release()
+				continue
+			}
+
+			// Extract sessionID from raw packetHeader for session-level link caching before re-encrypting
+			sessionID := binary.BigEndian.Uint64(packetHeader[:8])
+
+			// Re-encrypt packetHeader with next hop block cipher
+			targetDest.blockCipher.Encrypt(packetHeader[:], packetHeader[:])
+
+			// Strip outer EIH: replace second block with re-encrypted packetHeader and advance
+			copy(data[AESBlockSize:2*AESBlockSize], packetHeader[:])
+			b.Advance(int32(AESBlockSize))
+
+			dest := targetDest.destination
+			dest.Network = net.Network_UDP
+
+			entry, ok := udpConns.Load(sessionID)
+			if !ok {
+				sessCtx, cancel := context.WithCancel(ctx)
+				inbound := session.InboundFromContext(sessCtx)
+				inbound.User = &protocol.MemoryUser{
+					Email: targetDest.email,
+					Level: targetDest.level,
+				}
+
+				sessCtx = log.ContextWithAccessMessage(sessCtx, &log.AccessMessage{
+					From:   conn.RemoteAddr(),
+					To:     dest,
+					Status: log.AccessAccepted,
+					Email:  targetDest.email,
+				})
+
+				link, err := dispatcher.Dispatch(sessCtx, dest)
 				if err != nil {
-					packet.Release()
-					buf.ReleaseMulti(mb)
-					return err
+					cancel()
+					b.Release()
+					continue
+				}
+
+				newEntry := &udpConnEntry{
+					link:   link,
+					cancel: cancel,
+				}
+				sessionPolicy := i.policyManager.ForLevel(targetDest.level)
+				newEntry.timer = signal.CancelAfterInactivity(sessCtx, func() {
+					udpConns.Delete(sessionID)
+					common.Interrupt(link.Reader)
+					common.Interrupt(link.Writer)
+					cancel()
+				}, sessionPolicy.Timeouts.ConnectionIdle)
+
+				actual, loaded := udpConns.LoadOrStore(sessionID, newEntry)
+				if loaded {
+					newEntry.timer.SetTimeout(0)
+					entry = actual
+				} else {
+					entry = newEntry
+					go func(cEntry *udpConnEntry) {
+						defer func() {
+							cEntry.timer.SetTimeout(0)
+						}()
+						for {
+							resMb, err := cEntry.link.Reader.ReadMultiBuffer()
+							if err != nil {
+								return
+							}
+							cEntry.timer.Update()
+							for _, rb := range resMb {
+								_, _ = conn.Write(rb.Bytes())
+								rb.Release()
+							}
+						}
+					}(entry)
 				}
 			}
+
+			entry.timer.Update()
+			_ = entry.link.Writer.WriteMultiBuffer(buf.MultiBuffer{b})
 		}
 	}
 }
-
-func (i *RelayInbound) NewConnection(ctx context.Context, conn net.Conn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	userInt, _ := A.UserFromContext[int](ctx)
-	user := i.destinations[userInt]
-	inbound.User = &protocol.MemoryUser{
-		Email: user.Email,
-		Level: uint32(user.Level),
-	}
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  user.Email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to tcp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_TCP)
-	if err != nil {
-		return err
-	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	return singbridge.CopyConn(ctx, nil, link, conn)
-}
-
-func (i *RelayInbound) NewPacketConnection(ctx context.Context, conn N.PacketConn, metadata M.Metadata) error {
-	inbound := session.InboundFromContext(ctx)
-	userInt, _ := A.UserFromContext[int](ctx)
-	user := i.destinations[userInt]
-	inbound.User = &protocol.MemoryUser{
-		Email: user.Email,
-		Level: uint32(user.Level),
-	}
-	ctx = log.ContextWithAccessMessage(ctx, &log.AccessMessage{
-		From:   metadata.Source,
-		To:     metadata.Destination,
-		Status: log.AccessAccepted,
-		Email:  user.Email,
-	})
-	errors.LogInfo(ctx, "tunnelling request to udp:", metadata.Destination)
-	dispatcher := session.DispatcherFromContext(ctx)
-	destination, err := singbridge.ToDestination(metadata.Destination, net.Network_UDP)
-	if err != nil {
-		return err
-	}
-	link, err := dispatcher.Dispatch(ctx, destination)
-	if err != nil {
-		return err
-	}
-	outConn := &singbridge.PacketConnWrapper{
-		Reader: link.Reader,
-		Writer: link.Writer,
-		Dest:   destination,
-		T: signal.CancelAfterInactivity(ctx, func() {
-			common.Interrupt(link.Reader)
-		}, 300*time.Second),
-	}
-	return bufio.CopyPacketConn(ctx, conn, outConn)
-}
-
-func (i *RelayInbound) NewError(ctx context.Context, err error) {
-	if E.IsClosed(err) {
-		return
-	}
-	errors.LogWarning(ctx, err.Error())
-}

proxy/shadowsocks_2022/kdf.go

@@ -0,0 +1,63 @@
+package shadowsocks_2022
+
+import (
+	"encoding/base64"
+	"strings"
+
+	"lukechampine.com/blake3"
+)
+
+const (
+	ContextSessionSubKey  = "shadowsocks 2022 session subkey"
+	ContextIdentitySubKey = "shadowsocks 2022 identity subkey"
+)
+
+// ParseKey decodes a base64 or raw PSK key string and validates its length
+func ParseKey(key string, keyLength int) ([]byte, error) {
+	raw, err := base64.StdEncoding.DecodeString(key)
+	if err != nil {
+		raw = []byte(key)
+	}
+	if len(raw) != keyLength {
+		return nil, ErrBadKey
+	}
+	return raw, nil
+}
+
+func ParsePSKList(password string, keyLength int) ([][]byte, error) {
+	parts := strings.Split(password, ":")
+	pskList := make([][]byte, len(parts))
+	for i, part := range parts {
+		norm, err := ParseKey(part, keyLength)
+		if err != nil {
+			return nil, err
+		}
+		pskList[i] = norm
+	}
+	return pskList, nil
+}
+
+func deriveSubKey(ctx string, psk, salt []byte, keyLength int) []byte {
+	var keyMaterial [64]byte
+	kmLen := len(psk) + len(salt)
+	copy(keyMaterial[:], psk)
+	copy(keyMaterial[len(psk):], salt)
+	out := make([]byte, keyLength)
+	blake3.DeriveKey(out, ctx, keyMaterial[:kmLen])
+	return out
+}
+
+func DeriveSessionSubKey(psk, salt []byte, keyLength int) []byte {
+	return deriveSubKey(ContextSessionSubKey, psk, salt, keyLength)
+}
+
+func DeriveIdentitySubKey(psk, salt []byte, keyLength int) []byte {
+	return deriveSubKey(ContextIdentitySubKey, psk, salt, keyLength)
+}
+
+func DeriveUserPSKHash(userPSK []byte) [AESBlockSize]byte {
+	h := blake3.Sum512(userPSK)
+	var out [AESBlockSize]byte
+	copy(out[:], h[:AESBlockSize])
+	return out
+}

proxy/shadowsocks_2022/outbound.go

@@ -2,21 +2,20 @@ package shadowsocks_2022
 
 import (
 	"context"
+	"crypto/rand"
+	"io"
 	"time"
 
-	shadowsocks "github.com/sagernet/sing-shadowsocks"
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
-	C "github.com/sagernet/sing/common"
-	B "github.com/sagernet/sing/common/buf"
-	"github.com/sagernet/sing/common/bufio"
-	N "github.com/sagernet/sing/common/network"
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
 	"github.com/xtls/xray-core/common/errors"
 	"github.com/xtls/xray-core/common/net"
+	"github.com/xtls/xray-core/common/retry"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/common/signal"
-	"github.com/xtls/xray-core/common/singbridge"
+	"github.com/xtls/xray-core/common/task"
+	"github.com/xtls/xray-core/core"
+	"github.com/xtls/xray-core/features/policy"
 	"github.com/xtls/xray-core/transport"
 	"github.com/xtls/xray-core/transport/internet"
 )
@@ -28,42 +27,49 @@ func init() {
 }
 
 type Outbound struct {
-	ctx    context.Context
-	server net.Destination
-	method shadowsocks.Method
+	ctx           context.Context
+	server        net.Destination
+	method        *CipherMethod
+	pskList       [][]byte
+	finalPSK      []byte
+	udpCodec      *UDPPacketCodec
+	policyManager policy.Manager
 }
 
 func NewClient(ctx context.Context, config *ClientConfig) (*Outbound, error) {
-	o := &Outbound{
+	method, err := GetCipherMethod(config.Method)
+	if err != nil {
+		return nil, errors.New("unsupported method: ", config.Method).Base(err)
+	}
+
+	pskList, err := ParsePSKList(config.Key, method.KeySaltLength)
+	if err != nil {
+		return nil, errors.New("invalid key: ", config.Key).Base(err)
+	}
+
+	finalPSK := pskList[len(pskList)-1]
+	udpCodec, err := NewUDPPacketCodec(method, finalPSK)
+	if err != nil {
+		return nil, errors.New("failed to create udp packet codec").Base(err)
+	}
+
+	v := core.MustFromContext(ctx)
+	return &Outbound{
 		ctx: ctx,
 		server: net.Destination{
 			Address: config.Address.AsAddress(),
 			Port:    net.Port(config.Port),
 			Network: net.Network_TCP,
 		},
-	}
-	if C.Contains(shadowaead_2022.List, config.Method) {
-		if config.Key == "" {
-			return nil, errors.New("missing psk")
-		}
-		method, err := shadowaead_2022.NewWithPassword(config.Method, config.Key, nil)
-		if err != nil {
-			return nil, errors.New("create method").Base(err)
-		}
-		o.method = method
-	} else {
-		return nil, errors.New("unknown method ", config.Method)
-	}
-	return o, nil
+		method:        method,
+		pskList:       pskList,
+		finalPSK:      finalPSK,
+		udpCodec:      udpCodec,
+		policyManager: v.GetFeature(policy.ManagerType()).(policy.Manager),
+	}, nil
 }
 
 func (o *Outbound) Process(ctx context.Context, link *transport.Link, dialer internet.Dialer) error {
-	var inboundConn net.Conn
-	inbound := session.InboundFromContext(ctx)
-	if inbound != nil {
-		inboundConn = inbound.Conn
-	}
-
 	outbounds := session.OutboundsFromContext(ctx)
 	ob := outbounds[len(outbounds)-1]
 	if !ob.Target.IsValid() {
@@ -78,70 +84,123 @@ func (o *Outbound) Process(ctx context.Context, link *transport.Link, dialer int
 
 	serverDestination := o.server
 	serverDestination.Network = network
-	connection, err := dialer.Dial(ctx, serverDestination)
-	if err != nil {
-		return errors.New("failed to connect to server").Base(err)
-	}
-	defer connection.Close()
 
+	var conn net.Conn
+	if err := retry.ExponentialBackoff(5, 100).On(func() error {
+		rawConn, err := dialer.Dial(ctx, serverDestination)
+		if err != nil {
+			return err
+		}
+		conn = rawConn
+		return nil
+	}); err != nil {
+		return errors.New("failed to find an available destination").Base(err).AtWarning()
+	}
+	defer conn.Close()
+
+	var newCtx context.Context
+	var newCancel context.CancelFunc
 	if session.TimeoutOnlyFromContext(ctx) {
-		ctx, _ = context.WithCancel(context.Background())
+		newCtx, newCancel = context.WithCancel(context.Background())
+	}
+
+	sessionPolicy := o.policyManager.ForLevel(0)
+	ctx, cancel := context.WithCancel(ctx)
+	timer := signal.CancelAfterInactivity(ctx, func() {
+		cancel()
+		if newCancel != nil {
+			newCancel()
+		}
+	}, sessionPolicy.Timeouts.ConnectionIdle)
+
+	ctx = policy.ContextWithBufferPolicy(ctx, sessionPolicy.Buffer)
+
+	if newCtx != nil {
+		ctx = newCtx
 	}
 
 	if network == net.Network_TCP {
-		serverConn := o.method.DialEarlyConn(connection, singbridge.ToSocksaddr(destination))
-		var handshake bool
-		if timeoutReader, isTimeoutReader := link.Reader.(buf.TimeoutReader); isTimeoutReader {
-			mb, err := timeoutReader.ReadMultiBufferTimeout(time.Millisecond * 100)
-			if err != nil && err != buf.ErrNotTimeoutReader && err != buf.ErrReadTimeout {
-				return errors.New("read payload").Base(err)
-			}
-			payload := B.New()
-			for {
-				payload.Reset()
-				nb, n := buf.SplitBytes(mb, payload.FreeBytes())
-				if n > 0 {
-					payload.Truncate(n)
-					_, err = serverConn.Write(payload.Bytes())
-					if err != nil {
-						payload.Release()
-						return errors.New("write payload").Base(err)
-					}
-					handshake = true
-				}
-				if nb.IsEmpty() {
-					break
-				}
-				mb = nb
-			}
-			payload.Release()
-		}
-		if !handshake {
-			_, err = serverConn.Write(nil)
-			if err != nil {
-				return errors.New("client handshake").Base(err)
-			}
-		}
-		return singbridge.CopyConn(ctx, inboundConn, link, serverConn)
-	} else {
-		var packetConn N.PacketConn
-		if pc, isPacketConn := inboundConn.(N.PacketConn); isPacketConn {
-			packetConn = pc
-		} else if nc, isNetPacket := inboundConn.(net.PacketConn); isNetPacket {
-			packetConn = bufio.NewPacketConn(nc)
-		} else {
-			packetConn = &singbridge.PacketConnWrapper{
-				Reader: link.Reader,
-				Writer: link.Writer,
-				Conn:   inboundConn,
-				Dest:   destination,
-				T: signal.CancelAfterInactivity(ctx, func() {
-					common.Interrupt(link.Reader)
-				}, 300*time.Second),
-			}
+		var clientSalt [32]byte
+		clientSaltSlice := clientSalt[:o.method.KeySaltLength]
+		if _, err := io.ReadFull(rand.Reader, clientSaltSlice); err != nil {
+			return errors.New("failed to generate client salt").Base(err)
 		}
 
-		serverConn := o.method.DialPacketConn(connection)
-		return singbridge.ReturnError(bufio.CopyPacketConn(ctx, packetConn, serverConn))
+		requestDone := func() error {
+			defer timer.SetTimeout(sessionPolicy.Timeouts.DownlinkOnly)
+			bufferedWriter := buf.NewBufferedWriter(buf.NewWriter(conn))
+			bodyWriter, err := WriteTCPRequest(bufferedWriter, o.method, o.pskList, destination, clientSaltSlice, nil)
+			if err != nil {
+				return errors.New("failed to write request").Base(err)
+			}
+
+			if err = buf.CopyOnceTimeout(link.Reader, bodyWriter, time.Millisecond*100); err != nil && err != buf.ErrNotTimeoutReader && err != buf.ErrReadTimeout {
+				return errors.New("failed to write A request payload").Base(err).AtWarning()
+			}
+
+			if err := bufferedWriter.SetBuffered(false); err != nil {
+				return err
+			}
+
+			return buf.Copy(link.Reader, bodyWriter, buf.UpdateActivity(timer))
+		}
+
+		responseDone := func() error {
+			defer timer.SetTimeout(sessionPolicy.Timeouts.UplinkOnly)
+
+			responseReader, err := ReadTCPResponse(conn, o.method, o.finalPSK, clientSaltSlice)
+			if err != nil {
+				return err
+			}
+
+			return buf.Copy(responseReader, link.Writer, buf.UpdateActivity(timer))
+		}
+
+		responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+		if err := task.Run(ctx, requestDone, responseDoneAndCloseWriter); err != nil {
+			return errors.New("connection ends").Base(err)
+		}
+
+		return nil
 	}
+
+	if network == net.Network_UDP {
+		requestDone := func() error {
+			defer timer.SetTimeout(sessionPolicy.Timeouts.DownlinkOnly)
+
+			writer := &UDPWriter{
+				Writer:      conn,
+				Destination: destination,
+				Codec:       o.udpCodec,
+			}
+
+			if err := buf.Copy(link.Reader, writer, buf.UpdateActivity(timer)); err != nil {
+				return errors.New("failed to transport all UDP request").Base(err)
+			}
+			return nil
+		}
+
+		responseDone := func() error {
+			defer timer.SetTimeout(sessionPolicy.Timeouts.UplinkOnly)
+
+			reader := &UDPReader{
+				Reader: conn,
+				Codec:  o.udpCodec,
+			}
+
+			if err := buf.Copy(reader, link.Writer, buf.UpdateActivity(timer)); err != nil {
+				return errors.New("failed to transport all UDP response").Base(err)
+			}
+			return nil
+		}
+
+		responseDoneAndCloseWriter := task.OnSuccess(responseDone, task.Close(link.Writer))
+		if err := task.Run(ctx, requestDone, responseDoneAndCloseWriter); err != nil {
+			return errors.New("connection ends").Base(err)
+		}
+
+		return nil
+	}
+
+	return errors.New("unsupported network: ", network)
 }

proxy/shadowsocks_2022/packet.go

@@ -0,0 +1,516 @@
+package shadowsocks_2022
+
+import (
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/binary"
+	"io"
+	"math"
+	mrand "math/rand/v2"
+	"sync/atomic"
+	"time"
+
+	"github.com/xtls/xray-core/common/buf"
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
+)
+
+type UDPCodec struct {
+	method           *CipherMethod
+	psk              []byte
+	blockCipher      cipher.Block
+	chachaCipher     cipher.AEAD
+	clientBodyCipher cipher.AEAD
+	clientSessionID  uint64
+	nextPacketID     atomic.Uint64
+	sessions         *UDPSessionManager
+}
+
+type (
+	UDPPacketCodec = UDPCodec
+	UDPServerCodec = UDPCodec
+)
+
+func newUDPCodec(method *CipherMethod, psk []byte) (*UDPCodec, error) {
+	c := &UDPCodec{
+		method: method,
+		psk:    psk,
+	}
+	var err error
+	if method.IsChaCha {
+		c.chachaCipher, err = method.NewUDPCipher(psk)
+	} else {
+		c.blockCipher, err = method.NewBlock(psk)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return c, nil
+}
+
+func NewUDPPacketCodec(method *CipherMethod, psk []byte) (*UDPCodec, error) {
+	c, err := newUDPCodec(method, psk)
+	if err != nil {
+		return nil, err
+	}
+	var sessID [8]byte
+	if _, err := io.ReadFull(rand.Reader, sessID[:]); err != nil {
+		return nil, err
+	}
+	c.clientSessionID = binary.BigEndian.Uint64(sessID[:])
+
+	if !method.IsChaCha {
+		clientBodyKey := DeriveSessionSubKey(psk, sessID[:], method.KeySaltLength)
+		c.clientBodyCipher, err = method.NewAEAD(clientBodyKey)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return c, nil
+}
+
+func NewUDPServerCodec(method *CipherMethod, psk []byte, sessionTimeout time.Duration) (*UDPCodec, error) {
+	c, err := newUDPCodec(method, psk)
+	if err != nil {
+		return nil, err
+	}
+	c.sessions = NewUDPSessionManager(sessionTimeout)
+	return c, nil
+}
+
+func (c *UDPCodec) EncodeClientPacket(dest net.Destination, payload []byte) (*buf.Buffer, error) {
+	packetID := c.nextPacketID.Add(1)
+	sessID := c.clientSessionID
+
+	// Padding determination (e.g. DNS port 53 disguise)
+	var paddingLen int
+	if dest.Port == 53 && len(payload) < MaxPaddingLength {
+		paddingLen = mrand.IntN(MaxPaddingLength-len(payload)) + 1
+	}
+
+	addrPortLen := AddrPortLength(dest)
+
+	if c.method.IsChaCha {
+		// ChaCha20 mode: 24-byte nonce + plaintext header (27B) + padding + dest + payload + AEAD tag (16B)
+		totalLen := PacketNonceSize + 27 + paddingLen + addrPortLen + len(payload) + AEADTagSize
+		if totalLen > buf.Size {
+			return nil, ErrPacketTooLarge
+		}
+
+		outBuf := buf.New()
+
+		var nonce [PacketNonceSize]byte
+		if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
+			outBuf.Release()
+			return nil, err
+		}
+		outBuf.Write(nonce[:])
+
+		var hdr [16 + 1 + 8 + 2]byte
+		binary.BigEndian.PutUint64(hdr[0:8], sessID)
+		binary.BigEndian.PutUint64(hdr[8:16], packetID)
+		hdr[16] = HeaderTypeClient
+		binary.BigEndian.PutUint64(hdr[17:25], uint64(time.Now().Unix()))
+		binary.BigEndian.PutUint16(hdr[25:27], uint16(paddingLen))
+		outBuf.Write(hdr[:])
+		if paddingLen > 0 {
+			outBuf.Write(zeroPadding[:paddingLen])
+		}
+
+		if err := WriteAddressPort(outBuf, dest); err != nil {
+			outBuf.Release()
+			return nil, err
+		}
+		outBuf.Write(payload)
+
+		plainBytes := outBuf.Bytes()[PacketNonceSize:]
+		outBuf.Extend(int32(c.chachaCipher.Overhead()))
+		c.chachaCipher.Seal(plainBytes[:0], nonce[:], plainBytes, nil)
+		return outBuf, nil
+	}
+
+	// AES mode:
+	// 16B Encrypted Header + (11B header + padding + dest + payload + 16B AEAD tag)
+	totalLen := 16 + 11 + paddingLen + addrPortLen + len(payload) + AEADTagSize
+	if totalLen > buf.Size {
+		return nil, ErrPacketTooLarge
+	}
+
+	outBuf := buf.New()
+
+	var rawHeader [16]byte
+	binary.BigEndian.PutUint64(rawHeader[:8], sessID)
+	binary.BigEndian.PutUint64(rawHeader[8:16], packetID)
+
+	var encryptedHeader [16]byte
+	c.blockCipher.Encrypt(encryptedHeader[:], rawHeader[:])
+	outBuf.Write(encryptedHeader[:])
+
+	bodyAead := c.clientBodyCipher
+
+	var hdr [1 + 8 + 2]byte
+	hdr[0] = HeaderTypeClient
+	binary.BigEndian.PutUint64(hdr[1:9], uint64(time.Now().Unix()))
+	binary.BigEndian.PutUint16(hdr[9:11], uint16(paddingLen))
+	outBuf.Write(hdr[:])
+	if paddingLen > 0 {
+		outBuf.Write(zeroPadding[:paddingLen])
+	}
+
+	if err := WriteAddressPort(outBuf, dest); err != nil {
+		outBuf.Release()
+		return nil, err
+	}
+	outBuf.Write(payload)
+
+	plainBytes := outBuf.Bytes()[16:]
+	bodyNonce := rawHeader[4:16]
+	outBuf.Extend(int32(bodyAead.Overhead()))
+	bodyAead.Seal(plainBytes[:0], bodyNonce, plainBytes, nil)
+	return outBuf, nil
+}
+
+type DecodedUDPPacket struct {
+	SessionID   uint64
+	PacketID    uint64
+	HeaderType  byte
+	Timestamp   uint64
+	Destination net.Destination
+	Payload     []byte
+}
+
+func parseAddressPort(data []byte) (net.Destination, int, error) {
+	if len(data) < 1 {
+		return net.Destination{}, 0, ErrPacketTooShort
+	}
+	switch data[0] {
+	case 1: // IPv4
+		if len(data) < 1+4+2 {
+			return net.Destination{}, 0, ErrPacketTooShort
+		}
+		ip := net.IPAddress(data[1:5])
+		port := binary.BigEndian.Uint16(data[5:7])
+		return net.UDPDestination(ip, net.Port(port)), 7, nil
+	case 4: // IPv6
+		if len(data) < 1+16+2 {
+			return net.Destination{}, 0, ErrPacketTooShort
+		}
+		ip := net.IPAddress(data[1:17])
+		port := binary.BigEndian.Uint16(data[17:19])
+		return net.UDPDestination(ip, net.Port(port)), 19, nil
+	case 3: // Domain
+		if len(data) < 2 {
+			return net.Destination{}, 0, ErrPacketTooShort
+		}
+		domainLen := int(data[1])
+		if len(data) < 2+domainLen+2 {
+			return net.Destination{}, 0, ErrPacketTooShort
+		}
+		domain := string(data[2 : 2+domainLen])
+		port := binary.BigEndian.Uint16(data[2+domainLen : 2+domainLen+2])
+		return net.UDPDestination(net.DomainAddress(domain), net.Port(port)), 2 + domainLen + 2, nil
+	default:
+		return net.Destination{}, 0, errors.New("unknown address type")
+	}
+}
+
+func parsePlainUDPPacket(sessionID, packetID uint64, bodyPlain []byte) (DecodedUDPPacket, error) {
+	if len(bodyPlain) < 1+8+2 {
+		return DecodedUDPPacket{}, ErrPacketTooShort
+	}
+
+	headerType := bodyPlain[0]
+	epoch := binary.BigEndian.Uint64(bodyPlain[1:9])
+	diff := int(math.Abs(float64(time.Now().Unix() - int64(epoch))))
+	if diff > 30 {
+		return DecodedUDPPacket{}, ErrBadTimestamp
+	}
+
+	offset := 9
+	if headerType == HeaderTypeServer {
+		if len(bodyPlain) < offset+8+2 {
+			return DecodedUDPPacket{}, ErrPacketTooShort
+		}
+		offset += 8 // skip clientSessionID
+	}
+
+	paddingLen := int(binary.BigEndian.Uint16(bodyPlain[offset : offset+2]))
+	offset += 2
+
+	if len(bodyPlain) < offset+paddingLen {
+		return DecodedUDPPacket{}, ErrNoPadding
+	}
+	offset += paddingLen
+
+	dest, addrLen, err := parseAddressPort(bodyPlain[offset:])
+	if err != nil {
+		return DecodedUDPPacket{}, err
+	}
+	payload := bodyPlain[offset+addrLen:]
+
+	return DecodedUDPPacket{
+		SessionID:   sessionID,
+		PacketID:    packetID,
+		HeaderType:  headerType,
+		Timestamp:   epoch,
+		Destination: dest,
+		Payload:     payload,
+	}, nil
+}
+
+func (c *UDPCodec) DecodePacket(data []byte) (DecodedUDPPacket, error) {
+	if len(data) < PacketMinimalHeaderSize {
+		return DecodedUDPPacket{}, ErrPacketTooShort
+	}
+
+	if c.method.IsChaCha {
+		if len(data) < PacketNonceSize+AEADTagSize {
+			return DecodedUDPPacket{}, ErrPacketTooShort
+		}
+		nonce := data[:PacketNonceSize]
+		ciphertext := data[PacketNonceSize:]
+		plain, err := c.chachaCipher.Open(ciphertext[:0], nonce, ciphertext, nil)
+		if err != nil {
+			return DecodedUDPPacket{}, errors.New("failed to decrypt chacha udp packet").Base(err)
+		}
+		if len(plain) < 16+1+8+2 {
+			return DecodedUDPPacket{}, ErrPacketTooShort
+		}
+
+		sessionID := binary.BigEndian.Uint64(plain[:8])
+		packetID := binary.BigEndian.Uint64(plain[8:16])
+
+		if c.sessions != nil {
+			sessionItem, _ := c.sessions.GetOrCreate(sessionID)
+			sessionItem.Lock()
+			if !sessionItem.Window.CheckAndAdd(packetID) {
+				sessionItem.Unlock()
+				return DecodedUDPPacket{}, ErrPacketIdNotUnique
+			}
+			sessionItem.Unlock()
+		}
+
+		return parsePlainUDPPacket(sessionID, packetID, plain[16:])
+	}
+
+	// AES mode
+	var rawHeader [16]byte
+	c.blockCipher.Decrypt(rawHeader[:], data[:16])
+	sessionID := binary.BigEndian.Uint64(rawHeader[:8])
+	packetID := binary.BigEndian.Uint64(rawHeader[8:16])
+
+	var bodyAead cipher.AEAD
+	var sessionItem *ServerUDPSession
+
+	if c.sessions != nil {
+		sessionItem, _ = c.sessions.GetOrCreate(sessionID)
+		sessionItem.Lock()
+		if !sessionItem.Window.Check(packetID) {
+			sessionItem.Unlock()
+			return DecodedUDPPacket{}, ErrPacketIdNotUnique
+		}
+		sessionItem.Unlock()
+
+		bodyAead = sessionItem.GetRemoteCipher()
+		if bodyAead == nil {
+			bodyKey := DeriveSessionSubKey(c.psk, rawHeader[:8], c.method.KeySaltLength)
+			var err error
+			bodyAead, err = c.method.NewAEAD(bodyKey)
+			if err != nil {
+				return DecodedUDPPacket{}, err
+			}
+			sessionItem.SetRemoteCipher(bodyAead)
+		}
+	} else {
+		bodyKey := DeriveSessionSubKey(c.psk, rawHeader[:8], c.method.KeySaltLength)
+		var err error
+		bodyAead, err = c.method.NewAEAD(bodyKey)
+		if err != nil {
+			return DecodedUDPPacket{}, err
+		}
+	}
+
+	bodyNonce := rawHeader[4:16]
+	bodyCipher := data[16:]
+	bodyPlain, err := bodyAead.Open(bodyCipher[:0], bodyNonce, bodyCipher, nil)
+	if err != nil {
+		return DecodedUDPPacket{}, errors.New("failed to decrypt aes udp body").Base(err)
+	}
+
+	if sessionItem != nil {
+		sessionItem.Lock()
+		sessionItem.Window.Add(packetID)
+		sessionItem.Unlock()
+	}
+
+	return parsePlainUDPPacket(sessionID, packetID, bodyPlain)
+}
+
+func (s *ServerUDPSession) EnsureServerState(method *CipherMethod, headerBlock cipher.Block, chachaCipher cipher.AEAD, psk []byte) error {
+	s.Lock()
+	defer s.Unlock()
+	if s.ServerSessionID != 0 {
+		return nil
+	}
+	var sidBuf [8]byte
+	for {
+		if _, err := io.ReadFull(rand.Reader, sidBuf[:]); err != nil {
+			return err
+		}
+		s.ServerSessionID = binary.BigEndian.Uint64(sidBuf[:])
+		if s.ServerSessionID != 0 {
+			break
+		}
+	}
+	if method.IsChaCha {
+		s.ServerChaCha = chachaCipher
+	} else {
+		s.ServerBlockCipher = headerBlock
+		bodyKey := DeriveSessionSubKey(psk, sidBuf[:], method.KeySaltLength)
+		bodyAead, err := method.NewAEAD(bodyKey)
+		if err != nil {
+			s.ServerSessionID = 0
+			return err
+		}
+		s.ServerCipher = bodyAead
+	}
+	return nil
+}
+
+func (s *ServerUDPSession) EncodeServerPacket(method *CipherMethod, clientSessionID uint64, dest net.Destination, payload []byte) ([]byte, error) {
+	serverSessionID := s.ServerSessionID
+	serverPacketID := s.ServerPacketID.Add(1)
+
+	if method.IsChaCha {
+		var nonce [PacketNonceSize]byte
+		if _, err := io.ReadFull(rand.Reader, nonce[:]); err != nil {
+			return nil, err
+		}
+
+		plainBuf := buf.New()
+		defer plainBuf.Release()
+
+		var hdr [16 + 1 + 8 + 8 + 2]byte
+		binary.BigEndian.PutUint64(hdr[0:8], serverSessionID)
+		binary.BigEndian.PutUint64(hdr[8:16], serverPacketID)
+		hdr[16] = HeaderTypeServer
+		binary.BigEndian.PutUint64(hdr[17:25], uint64(time.Now().Unix()))
+		binary.BigEndian.PutUint64(hdr[25:33], clientSessionID)
+		binary.BigEndian.PutUint16(hdr[33:35], 0)
+		plainBuf.Write(hdr[:])
+
+		if err := WriteAddressPort(plainBuf, dest); err != nil {
+			return nil, err
+		}
+		plainBuf.Write(payload)
+
+		sealed := s.ServerChaCha.Seal(nil, nonce[:], plainBuf.Bytes(), nil)
+		res := make([]byte, PacketNonceSize+len(sealed))
+		copy(res[:PacketNonceSize], nonce[:])
+		copy(res[PacketNonceSize:], sealed)
+		return res, nil
+	}
+
+	// AES mode
+	var rawHeader [16]byte
+	binary.BigEndian.PutUint64(rawHeader[:8], serverSessionID)
+	binary.BigEndian.PutUint64(rawHeader[8:16], serverPacketID)
+
+	var encryptedHeader [16]byte
+	s.ServerBlockCipher.Encrypt(encryptedHeader[:], rawHeader[:])
+
+	bodyBuf := buf.New()
+	defer bodyBuf.Release()
+
+	var hdr [1 + 8 + 8 + 2]byte
+	hdr[0] = HeaderTypeServer
+	binary.BigEndian.PutUint64(hdr[1:9], uint64(time.Now().Unix()))
+	binary.BigEndian.PutUint64(hdr[9:17], clientSessionID)
+	binary.BigEndian.PutUint16(hdr[17:19], 0)
+	bodyBuf.Write(hdr[:])
+
+	if err := WriteAddressPort(bodyBuf, dest); err != nil {
+		return nil, err
+	}
+	bodyBuf.Write(payload)
+
+	bodyNonce := rawHeader[4:16]
+	sealedBody := s.ServerCipher.Seal(nil, bodyNonce, bodyBuf.Bytes(), nil)
+
+	res := make([]byte, 16+len(sealedBody))
+	copy(res[:16], encryptedHeader[:])
+	copy(res[16:], sealedBody)
+	return res, nil
+}
+
+func (c *UDPCodec) EncodeServerPacket(clientSessionID uint64, dest net.Destination, payload []byte) ([]byte, error) {
+	sessionItem, _ := c.sessions.GetOrCreate(clientSessionID)
+	if err := sessionItem.EnsureServerState(c.method, c.blockCipher, c.chachaCipher, c.psk); err != nil {
+		return nil, err
+	}
+	return sessionItem.EncodeServerPacket(c.method, clientSessionID, dest, payload)
+}
+
+func (c *UDPCodec) EncodePacket(clientSessionID uint64, dest net.Destination, payload []byte) ([]byte, error) {
+	return c.EncodeServerPacket(clientSessionID, dest, payload)
+}
+
+type UDPWriter struct {
+	Writer      io.Writer
+	Destination net.Destination
+	Codec       *UDPPacketCodec
+}
+
+func (w *UDPWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
+	for {
+		mb2, b := buf.SplitFirst(mb)
+		mb = mb2
+		if b == nil {
+			break
+		}
+		dest := w.Destination
+		if b.UDP != nil {
+			dest = *b.UDP
+		}
+		pktBuf, err := w.Codec.EncodeClientPacket(dest, b.Bytes())
+		b.Release()
+		if err != nil {
+			buf.ReleaseMulti(mb)
+			return err
+		}
+		_, writeErr := w.Writer.Write(pktBuf.Bytes())
+		pktBuf.Release()
+		if writeErr != nil {
+			buf.ReleaseMulti(mb)
+			return writeErr
+		}
+	}
+	return nil
+}
+
+type UDPReader struct {
+	Reader io.Reader
+	Codec  *UDPPacketCodec
+}
+
+func (r *UDPReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	for {
+		buffer := buf.New()
+		_, err := buffer.ReadFrom(r.Reader)
+		if err != nil {
+			buffer.Release()
+			return nil, err
+		}
+
+		decoded, err := r.Codec.DecodePacket(buffer.Bytes())
+		if err != nil {
+			buffer.Release()
+			continue
+		}
+		buffer.Clear()
+		buffer.Write(decoded.Payload)
+		dest := decoded.Destination
+		buffer.UDP = &dest
+		return buf.MultiBuffer{buffer}, nil
+	}
+}

proxy/shadowsocks_2022/relay_test.go

@@ -0,0 +1,230 @@
+package shadowsocks_2022_test
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/binary"
+	gonet "net"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/xtls/xray-core/common"
+	"github.com/xtls/xray-core/common/buf"
+	"github.com/xtls/xray-core/common/net"
+	. "github.com/xtls/xray-core/proxy/shadowsocks_2022"
+	"github.com/xtls/xray-core/transport"
+	"lukechampine.com/blake3"
+)
+
+// encodeRelayClientUDPPacket encodes a Shadowsocks-2022 UDP packet with 1 layer of EIH (Relay)
+func encodeRelayClientUDPPacket(relayKey, destKey []byte, sessionID, packetID uint64, dest net.Destination, payload []byte) ([]byte, error) {
+	method, err := GetCipherMethod(MethodAES128GCM)
+	if err != nil {
+		return nil, err
+	}
+	relayBlock, err := method.NewBlock(relayKey)
+	if err != nil {
+		return nil, err
+	}
+
+	// 1. Plain packet header: sessionID (8B) + packetID (8B)
+	var rawHeader [16]byte
+	binary.BigEndian.PutUint64(rawHeader[:8], sessionID)
+	binary.BigEndian.PutUint64(rawHeader[8:16], packetID)
+
+	// Encrypt packetHeader under relayKey
+	var encPacketHeader [16]byte
+	relayBlock.Encrypt(encPacketHeader[:], rawHeader[:])
+
+	// 2. EI Header: blake3(destKey)[:16] ^ rawHeader
+	var destHash [16]byte
+	hash512 := blake3.Sum512(destKey)
+	copy(destHash[:], hash512[:16])
+
+	var eiHeader [16]byte
+	for i := 0; i < 16; i++ {
+		eiHeader[i] = destHash[i] ^ rawHeader[i]
+	}
+	var encEIHeader [16]byte
+	relayBlock.Encrypt(encEIHeader[:], eiHeader[:])
+
+	// 3. Payload under destination server's AEAD
+	bodyKey := DeriveSessionSubKey(destKey, rawHeader[:8], 16)
+	bodyAead, err := method.NewAEAD(bodyKey)
+	if err != nil {
+		return nil, err
+	}
+	bodyNonce := rawHeader[4:16]
+
+	outBuf := buf.New()
+	defer outBuf.Release()
+
+	// VarHeader: client type (1) + timestamp (8) + paddingLen (2) + padding + dest + payload
+	var hdr [1 + 8 + 2]byte
+	hdr[0] = HeaderTypeClient
+	binary.BigEndian.PutUint64(hdr[1:9], uint64(time.Now().Unix()))
+	binary.BigEndian.PutUint16(hdr[9:11], 0)
+	outBuf.Write(hdr[:])
+
+	if err := WriteAddressPort(outBuf, dest); err != nil {
+		return nil, err
+	}
+	outBuf.Write(payload)
+
+	plainBytes := outBuf.Bytes()
+	outBuf.Extend(int32(bodyAead.Overhead()))
+	bodyAead.Seal(plainBytes[:0], bodyNonce, plainBytes, nil)
+
+	// Full packet: encPacketHeader (16B) + encEIHeader (16B) + sealedBody
+	packet := make([]byte, 0, 32+outBuf.Len())
+	packet = append(packet, encPacketHeader[:]...)
+	packet = append(packet, encEIHeader[:]...)
+	packet = append(packet, outBuf.Bytes()...)
+	return packet, nil
+}
+
+func TestRelayUDPSessionStabilityAndDispatch(t *testing.T) {
+	relayKey := []byte("0123456789abcdef")
+	destKey := []byte("fedcba9876543210")
+	relayKeyB64 := base64.StdEncoding.EncodeToString(relayKey)
+	destKeyB64 := base64.StdEncoding.EncodeToString(destKey)
+
+	config := &RelayServerConfig{
+		Method: MethodAES128GCM,
+		Key:    relayKeyB64,
+		Destinations: []*RelayDestination{
+			{
+				Key:     destKeyB64,
+				Address: &net.IPOrDomain{Address: &net.IPOrDomain_Ip{Ip: []byte{127, 0, 0, 1}}},
+				Port:    8388,
+				Email:   "dest@example.com",
+			},
+		},
+	}
+
+	inbound, err := NewRelayServer(newTestContext(), config)
+	if err != nil {
+		t.Fatalf("failed to create RelayServer: %v", err)
+	}
+
+	sessionID := uint64(0x1122334455667788)
+	dest := net.UDPDestination(net.LocalHostIP, 8388)
+
+	pkt1, err := encodeRelayClientUDPPacket(relayKey, destKey, sessionID, 1, dest, []byte("xray packet 1"))
+	if err != nil {
+		t.Fatalf("failed to encode pkt1: %v", err)
+	}
+	pkt2, err := encodeRelayClientUDPPacket(relayKey, destKey, sessionID, 2, dest, []byte("xray packet 2"))
+	if err != nil {
+		t.Fatalf("failed to encode pkt2: %v", err)
+	}
+
+	var dispatchCount atomic.Int32
+	var receivedPackets [][]byte
+	var mu sync.Mutex
+
+	disp := &dummyDispatcher{
+		onDispatch: func(ctx context.Context, d net.Destination) (*transport.Link, error) {
+			dispatchCount.Add(1)
+			linkR, linkW := gonet.Pipe()
+			t.Cleanup(func() {
+				linkW.Close()
+				linkR.Close()
+			})
+			link := &transport.Link{
+				Reader: buf.NewReader(linkR),
+				Writer: &customWriter{
+					write: func(mb buf.MultiBuffer) error {
+						mu.Lock()
+						defer mu.Unlock()
+						for _, b := range mb {
+							cpy := make([]byte, b.Len())
+							copy(cpy, b.Bytes())
+							receivedPackets = append(receivedPackets, cpy)
+							b.Release()
+						}
+						return nil
+					},
+				},
+			}
+			return link, nil
+		},
+	}
+
+	clientConn, serverConn := gonet.Pipe()
+	defer clientConn.Close()
+	defer serverConn.Close()
+
+	inboundConn := &dummyStatConn{Conn: serverConn}
+	ctx, cancel := context.WithCancel(newTestContext())
+	defer cancel()
+
+	go func() {
+		_ = inbound.Process(ctx, net.Network_UDP, inboundConn, disp)
+	}()
+
+	// Send Packet 1
+	_, err = clientConn.Write(pkt1)
+	if err != nil {
+		t.Fatalf("write pkt1 failed: %v", err)
+	}
+	time.Sleep(50 * time.Millisecond)
+
+	// Send Packet 2 (same sessionID, packetID=2)
+	_, err = clientConn.Write(pkt2)
+	if err != nil {
+		t.Fatalf("write pkt2 failed: %v", err)
+	}
+	time.Sleep(50 * time.Millisecond)
+
+	// Check dispatch count: For the SAME UDP session, Dispatch MUST be called exactly ONCE!
+	if count := dispatchCount.Load(); count != 1 {
+		t.Fatalf("CRITICAL BUG CONFIRMED: expected dispatchCount = 1 for same session, got %d (sessionID was corrupted by Encrypt!)", count)
+	}
+
+	// Verify downstream destination can decode both packets
+	method, err := GetCipherMethod(MethodAES128GCM)
+	common.Must(err)
+	destCodec, err := NewUDPServerCodec(method, destKey, 300*time.Second)
+	common.Must(err)
+
+	mu.Lock()
+	pkts := receivedPackets
+	mu.Unlock()
+
+	if len(pkts) != 2 {
+		t.Fatalf("expected 2 received packets at destination, got %d", len(pkts))
+	}
+
+	dec1, err := destCodec.DecodePacket(pkts[0])
+	if err != nil {
+		t.Fatalf("dest failed to decode packet 1: %v", err)
+	}
+	if dec1.SessionID != sessionID || dec1.PacketID != 1 || string(dec1.Payload) != "xray packet 1" {
+		t.Fatalf("dec1 mismatch: sess=%x, pktID=%d, payload=%s", dec1.SessionID, dec1.PacketID, string(dec1.Payload))
+	}
+
+	dec2, err := destCodec.DecodePacket(pkts[1])
+	if err != nil {
+		t.Fatalf("dest failed to decode packet 2: %v", err)
+	}
+	if dec2.SessionID != sessionID || dec2.PacketID != 2 || string(dec2.Payload) != "xray packet 2" {
+		t.Fatalf("dec2 mismatch: sess=%x, pktID=%d, payload=%s", dec2.SessionID, dec2.PacketID, string(dec2.Payload))
+	}
+}
+
+type customWriter struct {
+	write func(mb buf.MultiBuffer) error
+}
+
+func (w *customWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
+	return w.write(mb)
+}
+
+func (w *customWriter) Close() error {
+	return nil
+}
+
+func (w *customWriter) Interrupt() {}

proxy/shadowsocks_2022/replay.go

@@ -0,0 +1,159 @@
+package shadowsocks_2022
+
+import (
+	"crypto/cipher"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/xtls/xray-core/common/protocol"
+	"github.com/xtls/xray-core/common/utils"
+)
+
+const (
+	swBlockBitLog = 6                                // 1<<6 == 64 bits
+	swBlockBits   = 1 << swBlockBitLog               // 64
+	swRingBlocks  = 1 << 7                           // 128
+	swBlockMask   = swRingBlocks - 1                 // 127
+	swBitMask     = swBlockBits - 1                  // 63
+	swSize        = (swRingBlocks - 1) * swBlockBits // 8128
+)
+
+type SlidingWindow struct {
+	last uint64
+	ring [swRingBlocks]uint64
+}
+
+func (f *SlidingWindow) Reset() {
+	f.last = 0
+	f.ring[0] = 0
+}
+
+func (f *SlidingWindow) Check(counter uint64) bool {
+	switch {
+	case counter > f.last:
+		return true
+	case f.last-counter > swSize:
+		return false
+	}
+
+	blockIndex := (counter >> swBlockBitLog) & swBlockMask
+	bitIndex := counter & swBitMask
+	return (f.ring[blockIndex]>>bitIndex)&1 == 0
+}
+
+func (f *SlidingWindow) Add(counter uint64) {
+	blockIndex := counter >> swBlockBitLog
+
+	if counter > f.last {
+		lastBlockIndex := f.last >> swBlockBitLog
+		diff := int(blockIndex - lastBlockIndex)
+		if diff > swRingBlocks {
+			diff = swRingBlocks
+		}
+
+		for i := 0; i < diff; i++ {
+			lastBlockIndex = (lastBlockIndex + 1) & swBlockMask
+			f.ring[lastBlockIndex] = 0
+		}
+
+		f.last = counter
+	}
+
+	blockIndex &= swBlockMask
+	bitIndex := counter & swBitMask
+	f.ring[blockIndex] |= 1 << bitIndex
+}
+
+func (f *SlidingWindow) CheckAndAdd(counter uint64) bool {
+	if !f.Check(counter) {
+		return false
+	}
+	f.Add(counter)
+	return true
+}
+
+type ServerUDPSession struct {
+	sync.Mutex
+	SessionID    uint64
+	RemoteCipher atomic.Pointer[cipher.AEAD]
+	Window       SlidingWindow
+	User         *protocol.MemoryUser
+	UserPSK      []byte
+	LastActive   atomic.Int64 // Unix timestamp in seconds
+
+	ServerSessionID   uint64
+	ServerPacketID    atomic.Uint64
+	ServerCipher      cipher.AEAD
+	ServerBlockCipher cipher.Block
+	ServerChaCha      cipher.AEAD
+}
+
+func (s *ServerUDPSession) GetRemoteCipher() cipher.AEAD {
+	ptr := s.RemoteCipher.Load()
+	if ptr == nil {
+		return nil
+	}
+	return *ptr
+}
+
+func (s *ServerUDPSession) SetRemoteCipher(c cipher.AEAD) {
+	s.RemoteCipher.Store(&c)
+}
+
+type UDPSessionManager struct {
+	sessions  *utils.TypedSyncMap[uint64, *ServerUDPSession]
+	timeout   time.Duration
+	lastClean atomic.Int64 // Unix timestamp in seconds
+}
+
+func NewUDPSessionManager(timeout time.Duration) *UDPSessionManager {
+	return &UDPSessionManager{
+		sessions: utils.NewTypedSyncMap[uint64, *ServerUDPSession](),
+		timeout:  timeout,
+	}
+}
+
+func (m *UDPSessionManager) GetOrCreate(sessionID uint64) (*ServerUDPSession, bool) {
+	now := time.Now().Unix()
+	if s, ok := m.sessions.Load(sessionID); ok {
+		s.LastActive.Store(now)
+		return s, true
+	}
+
+	s := &ServerUDPSession{
+		SessionID: sessionID,
+	}
+	s.LastActive.Store(now)
+
+	actual, loaded := m.sessions.LoadOrStore(sessionID, s)
+	if loaded {
+		actual.LastActive.Store(now)
+		return actual, true
+	}
+
+	// Trigger cleanup if at least 30 seconds have passed since last cleanup
+	last := m.lastClean.Load()
+	if now-last > 30 && m.lastClean.CompareAndSwap(last, now) {
+		go m.cleanup(now)
+	}
+
+	return s, false
+}
+
+func (m *UDPSessionManager) cleanup(now int64) {
+	timeoutSec := int64(m.timeout.Seconds())
+	if timeoutSec <= 0 {
+		timeoutSec = 60
+	}
+	m.sessions.Range(func(k uint64, v *ServerUDPSession) bool {
+		if now-v.LastActive.Load() > timeoutSec {
+			m.sessions.Delete(k)
+		}
+		return true
+	})
+}
+
+func (m *UDPSessionManager) Delete(sessionID uint64) {
+	m.sessions.Delete(sessionID)
+}

proxy/shadowsocks_2022/shadowsocks_2022.go

@@ -1 +1,66 @@
 package shadowsocks_2022
+
+import (
+	"context"
+	"strings"
+	"sync"
+
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/signal"
+	"github.com/xtls/xray-core/transport"
+)
+
+type udpConnEntry struct {
+	sync.Mutex
+	link   *transport.Link
+	timer  *signal.ActivityTimer
+	cancel context.CancelFunc
+}
+
+const (
+	HeaderTypeClient              = 0
+	HeaderTypeServer              = 1
+	MaxPaddingLength              = 900
+	PacketNonceSize               = 24
+	MaxPacketSize                 = 65535
+	RequestHeaderFixedChunkLength = 1 + 8 + 2 // Type (1B) + Timestamp (8B) + VarHeaderLen (2B)
+	PacketMinimalHeaderSize       = 30
+	StreamNonceSize               = 12
+	AESBlockSize                  = 16
+	AEADTagSize                   = 16
+)
+
+var zeroPadding [MaxPaddingLength]byte
+
+const (
+	MethodAES128GCM        = "2022-blake3-aes-128-gcm"
+	MethodAES256GCM        = "2022-blake3-aes-256-gcm"
+	MethodChaCha20Poly1305 = "2022-blake3-chacha20-poly1305"
+)
+
+var List = []string{
+	MethodAES128GCM,
+	MethodAES256GCM,
+	MethodChaCha20Poly1305,
+}
+
+var (
+	ErrBadKey            = errors.New("bad key")
+	ErrBadHeaderType     = errors.New("bad header type")
+	ErrBadTimestamp      = errors.New("bad timestamp")
+	ErrSaltNotUnique     = errors.New("salt not unique")
+	ErrPacketIdNotUnique = errors.New("packet id not unique")
+	ErrPacketTooShort    = errors.New("packet too short")
+	ErrPacketTooLarge    = errors.New("packet too large")
+	ErrNoPadding         = errors.New("bad request: missing payload or padding")
+	ErrInvalidRequest    = errors.New("invalid request")
+)
+
+func IsSupportedMethod(method string) bool {
+	for _, m := range List {
+		if strings.EqualFold(m, method) {
+			return true
+		}
+	}
+	return false
+}

proxy/shadowsocks_2022/shadowsocks_2022_test.go

@@ -0,0 +1,794 @@
+package shadowsocks_2022_test
+
+import (
+	"bytes"
+	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/binary"
+	"io"
+	gonet "net"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/xtls/xray-core/common"
+	"github.com/xtls/xray-core/common/antireplay"
+	"github.com/xtls/xray-core/common/buf"
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
+	"github.com/xtls/xray-core/common/protocol"
+	"github.com/xtls/xray-core/common/serial"
+	"github.com/xtls/xray-core/common/session"
+	"github.com/xtls/xray-core/core"
+	"github.com/xtls/xray-core/features/routing"
+	. "github.com/xtls/xray-core/proxy/shadowsocks_2022"
+	"github.com/xtls/xray-core/transport"
+	"github.com/xtls/xray-core/transport/internet/stat"
+)
+
+func newTestContext() context.Context {
+	v, err := core.New(&core.Config{})
+	common.Must(err)
+	ctx := context.WithValue(context.Background(), core.XrayKey(1), v)
+	ctx = session.ContextWithInbound(ctx, &session.Inbound{})
+	return ctx
+}
+
+func generateRandomKey(size int) string {
+	b := make([]byte, size)
+	_, _ = rand.Read(b)
+	return base64.StdEncoding.EncodeToString(b)
+}
+
+func TestKDF(t *testing.T) {
+	// Test ParseKey
+	if _, err := ParseKey("", 16); err != ErrBadKey {
+		t.Fatalf("expected ErrBadKey for empty key, got %v", err)
+	}
+
+	shortKey := base64.StdEncoding.EncodeToString([]byte("short"))
+	if _, err := ParseKey(shortKey, 16); err != ErrBadKey {
+		t.Fatalf("expected ErrBadKey for short key, got %v", err)
+	}
+
+	exactKey := []byte("0123456789abcdef")
+	exactKeyB64 := base64.StdEncoding.EncodeToString(exactKey)
+	normExact, err := ParseKey(exactKeyB64, 16)
+	if err != nil || !bytes.Equal(normExact, exactKey) {
+		t.Fatalf("unexpected parsed exact key: %v, err: %v", normExact, err)
+	}
+
+	longKey := base64.StdEncoding.EncodeToString([]byte("0123456789abcdef_longer_key_for_testing"))
+	if _, err := ParseKey(longKey, 16); err != ErrBadKey {
+		t.Fatalf("expected ErrBadKey for long key, got %v", err)
+	}
+
+	// Test Session Subkey determinism
+	salt := []byte("random_salt_1234")
+	k1 := DeriveSessionSubKey(normExact, salt, 16)
+	k2 := DeriveSessionSubKey(normExact, salt, 16)
+	if !bytes.Equal(k1, k2) {
+		t.Fatal("DeriveSessionSubKey should be deterministic")
+	}
+
+	// Identity subkey must differ from session subkey with same inputs
+	idKey := DeriveIdentitySubKey(normExact, salt, 16)
+	if bytes.Equal(k1, idKey) {
+		t.Fatal("DeriveIdentitySubKey must differ from DeriveSessionSubKey")
+	}
+
+	// User PSK hash
+	h1 := DeriveUserPSKHash(normExact)
+	h2 := DeriveUserPSKHash(normExact)
+	if h1 != h2 {
+		t.Fatal("DeriveUserPSKHash should be deterministic")
+	}
+}
+
+func TestReplayFilter(t *testing.T) {
+	filter := antireplay.NewMapFilter[string](60)
+
+	salt1 := []byte("test_salt_111111")
+	salt2 := []byte("test_salt_222222")
+
+	if !filter.Check(string(salt1)) {
+		t.Fatal("first check on salt1 should be true")
+	}
+	if filter.Check(string(salt1)) {
+		t.Fatal("second check on salt1 should be false (replay detected)")
+	}
+
+	if !filter.Check(string(salt2)) {
+		t.Fatal("first check on salt2 should be true")
+	}
+
+	// Test SlidingWindow
+	var window SlidingWindow
+	if !window.Check(1) {
+		t.Fatal("packet 1 should be accepted")
+	}
+	window.Add(1)
+
+	if window.Check(1) {
+		t.Fatal("duplicate packet 1 should be rejected")
+	}
+
+	if !window.Check(100) {
+		t.Fatal("packet 100 should be accepted")
+	}
+	window.Add(100)
+
+	if window.Check(100) {
+		t.Fatal("duplicate packet 100 should be rejected")
+	}
+
+	if !window.Check(50) {
+		t.Fatal("out-of-order packet 50 within window should be accepted")
+	}
+	window.Add(50)
+	if window.Check(50) {
+		t.Fatal("duplicate packet 50 should be rejected")
+	}
+
+	// Check packet far behind window (> 8128)
+	window.Add(10000)
+	if window.Check(1) {
+		t.Fatal("packet 1 should be rejected as behind window")
+	}
+}
+
+func TestTCPStreamAndHandshake(t *testing.T) {
+	methods := []struct {
+		name    string
+		keySize int
+	}{
+		{MethodAES128GCM, 16},
+		{MethodAES256GCM, 32},
+		{MethodChaCha20Poly1305, 32},
+	}
+
+	dest := net.TCPDestination(net.LocalHostIP, net.Port(8080))
+	testPayload := []byte("Hello, Shadowsocks 2022 Native Implementation!")
+
+	for _, m := range methods {
+		t.Run(m.name, func(t *testing.T) {
+			rawKey := make([]byte, m.keySize)
+			_, _ = rand.Read(rawKey)
+			method, err := GetCipherMethod(m.name)
+			common.Must(err)
+
+			clientConn, serverConn := gonet.Pipe()
+			defer clientConn.Close()
+			defer serverConn.Close()
+
+			var wg sync.WaitGroup
+			wg.Add(2)
+
+			var receivedDest net.Destination
+			var receivedPayload []byte
+
+			// Server goroutine
+			go func() {
+				defer wg.Done()
+				salt := make([]byte, method.KeySaltLength)
+				_, err := io.ReadFull(serverConn, salt)
+				common.Must(err)
+
+				sessionKey := DeriveSessionSubKey(rawKey, salt, method.KeySaltLength)
+				aead, err := method.NewAEAD(sessionKey)
+				common.Must(err)
+
+				reader := NewStreamReader(serverConn, aead)
+
+				// Read fixed chunk (11 + 16 bytes)
+				var fixedBuf [RequestHeaderFixedChunkLength + AEADTagSize]byte
+				_, err = io.ReadFull(serverConn, fixedBuf[:])
+				common.Must(err)
+
+				plainFixed, err := aead.Open(fixedBuf[:0], reader.Nonce(), fixedBuf[:], nil)
+				common.Must(err)
+				IncreaseNonce(reader.Nonce())
+				if plainFixed[0] != HeaderTypeClient {
+					t.Errorf("expected client header type, got %d", plainFixed[0])
+				}
+
+				// Read variable chunk
+				varLen := int(plainFixed[9])<<8 | int(plainFixed[10])
+				varBuf := make([]byte, varLen+AEADTagSize)
+				_, err = io.ReadFull(serverConn, varBuf)
+				common.Must(err)
+
+				plainVar, err := aead.Open(varBuf[:0], reader.Nonce(), varBuf, nil)
+				common.Must(err)
+				IncreaseNonce(reader.Nonce())
+
+				vBuf := buf.New()
+				vBuf.Write(plainVar)
+				receivedDest, err = ReadAddressPort(vBuf)
+				common.Must(err)
+
+				// Skip padding
+				var padBytes [2]byte
+				_, _ = vBuf.Read(padBytes[:])
+				padLen := int(padBytes[0])<<8 | int(padBytes[1])
+				vBuf.Advance(int32(padLen))
+
+				receivedPayload = make([]byte, vBuf.Len())
+				copy(receivedPayload, vBuf.Bytes())
+				vBuf.Release()
+
+				// Server sends response handshake
+				serverSalt := make([]byte, method.KeySaltLength)
+				_, _ = rand.Read(serverSalt)
+				respKey := DeriveSessionSubKey(rawKey, serverSalt, method.KeySaltLength)
+				respAead, err := method.NewAEAD(respKey)
+				writer := NewStreamWriter(serverConn, respAead)
+				_, _ = serverConn.Write(serverSalt)
+
+				fixedResp := make([]byte, 1+8+method.KeySaltLength+2)
+				fixedResp[0] = HeaderTypeServer
+				binary.BigEndian.PutUint64(fixedResp[1:9], uint64(time.Now().Unix()))
+				copy(fixedResp[9:9+method.KeySaltLength], salt)
+				binary.BigEndian.PutUint16(fixedResp[9+method.KeySaltLength:11+method.KeySaltLength], 0)
+
+				fixedChunk := respAead.Seal(nil, writer.Nonce(), fixedResp, nil)
+				IncreaseNonce(writer.Nonce())
+				_, _ = serverConn.Write(fixedChunk)
+
+				// Echo stream data
+				mb, err := reader.ReadMultiBuffer()
+				common.Must(err)
+				_ = writer.WriteMultiBuffer(mb)
+			}()
+
+			// Client goroutine
+			go func() {
+				defer wg.Done()
+				clientSalt, writer, err := ClientHandshake(clientConn, method, [][]byte{rawKey}, dest, testPayload)
+				common.Must(err)
+
+				reader, _, err := ClientVerifyServerResponse(clientConn, method, rawKey, clientSalt)
+				common.Must(err)
+
+				// Send additional stream data
+				streamData := []byte("stream chunk test")
+				_ = writer.WriteChunk(streamData)
+
+				mb, err := reader.ReadMultiBuffer()
+				common.Must(err)
+				if !bytes.Equal(mb[0].Bytes(), streamData) {
+					t.Errorf("echoed stream data mismatch: got %s, want %s", mb[0].Bytes(), streamData)
+				}
+				buf.ReleaseMulti(mb)
+			}()
+
+			wg.Wait()
+
+			if receivedDest.NetAddr() != dest.NetAddr() {
+				t.Errorf("destination mismatch: got %s, want %s", receivedDest.NetAddr(), dest.NetAddr())
+			}
+			if diff := cmp.Diff(receivedPayload, testPayload); diff != "" {
+				t.Errorf("payload mismatch: %s", diff)
+			}
+		})
+	}
+}
+
+func TestUDPCodec(t *testing.T) {
+	methods := []string{
+		MethodAES128GCM,
+		MethodAES256GCM,
+		MethodChaCha20Poly1305,
+	}
+
+	dest := net.UDPDestination(net.LocalHostIP, net.Port(53))
+	payload := []byte("DNS query payload")
+
+	for _, methodName := range methods {
+		t.Run(methodName, func(t *testing.T) {
+			method, err := GetCipherMethod(methodName)
+			common.Must(err)
+
+			psk := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(psk)
+
+			clientCodec, err := NewUDPPacketCodec(method, psk)
+			common.Must(err)
+			serverCodec, err := NewUDPServerCodec(method, psk, time.Minute)
+			common.Must(err)
+
+			pktBuf, err := clientCodec.EncodeClientPacket(dest, payload)
+			common.Must(err)
+			defer pktBuf.Release()
+
+			decoded, err := serverCodec.DecodePacket(pktBuf.Bytes())
+			common.Must(err)
+
+			if decoded.HeaderType != HeaderTypeClient {
+				t.Errorf("expected header type %d, got %d", HeaderTypeClient, decoded.HeaderType)
+			}
+			if decoded.Destination.Port != dest.Port {
+				t.Errorf("port mismatch: got %d, want %d", decoded.Destination.Port, dest.Port)
+			}
+			if !bytes.Equal(decoded.Payload, payload) {
+				t.Errorf("payload mismatch: got %s, want %s", decoded.Payload, payload)
+			}
+		})
+	}
+}
+
+func TestMultiUserManager(t *testing.T) {
+	masterKey := generateRandomKey(16)
+	userKey1 := generateRandomKey(16)
+	userKey2 := generateRandomKey(16)
+
+	config := &MultiUserServerConfig{
+		Method: MethodAES128GCM,
+		Key:    masterKey,
+		Users: []*protocol.User{
+			{
+				Email:   "user1@example.com",
+				Account: serial.ToTypedMessage(&Account{Key: userKey1}),
+			},
+		},
+	}
+
+	inbound, err := NewMultiServer(newTestContext(), config)
+	common.Must(err)
+
+	if inbound.GetUsersCount(context.Background()) != 1 {
+		t.Fatalf("expected 1 user, got %d", inbound.GetUsersCount(context.Background()))
+	}
+
+	u1 := inbound.GetUser(context.Background(), "user1@example.com")
+	if u1 == nil || u1.Email != "user1@example.com" {
+		t.Fatal("user1 not found")
+	}
+
+	// Add User 2
+	rawKey2, _ := base64.StdEncoding.DecodeString(userKey2)
+	u2 := &protocol.MemoryUser{
+		Email: "user2@example.com",
+		Account: &MemoryAccount{
+			Key: rawKey2,
+		},
+	}
+	err = inbound.AddUser(context.Background(), u2)
+	common.Must(err)
+
+	if inbound.GetUsersCount(context.Background()) != 2 {
+		t.Fatalf("expected 2 users, got %d", inbound.GetUsersCount(context.Background()))
+	}
+
+	// Remove User 1
+	err = inbound.RemoveUser(context.Background(), "user1@example.com")
+	common.Must(err)
+
+	if inbound.GetUsersCount(context.Background()) != 1 {
+		t.Fatalf("expected 1 user, got %d", inbound.GetUsersCount(context.Background()))
+	}
+	if inbound.GetUser(context.Background(), "user1@example.com") != nil {
+		t.Fatal("user1 should have been removed")
+	}
+}
+
+type dummyDispatcher struct {
+	onDispatch func(ctx context.Context, dest net.Destination) (*transport.Link, error)
+}
+
+func (d *dummyDispatcher) Dispatch(ctx context.Context, dest net.Destination) (*transport.Link, error) {
+	if d.onDispatch != nil {
+		return d.onDispatch(ctx, dest)
+	}
+	return nil, errors.New("not handled")
+}
+
+func (d *dummyDispatcher) DispatchLink(ctx context.Context, dest net.Destination, link *transport.Link) error {
+	return nil
+}
+
+func (d *dummyDispatcher) Start() error      { return nil }
+func (d *dummyDispatcher) Close() error      { return nil }
+func (d *dummyDispatcher) Type() interface{} { return routing.DispatcherType() }
+
+type dummyStatConn struct {
+	gonet.Conn
+}
+
+func (c *dummyStatConn) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	b := buf.New()
+	_, err := b.ReadFrom(c.Conn)
+	return buf.MultiBuffer{b}, err
+}
+
+func (c *dummyStatConn) WriteMultiBuffer(mb buf.MultiBuffer) error {
+	defer buf.ReleaseMulti(mb)
+	for _, b := range mb {
+		if _, err := c.Conn.Write(b.Bytes()); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func TestMultiUserTCPConnection(t *testing.T) {
+	masterKey := generateRandomKey(16)
+	userKey1 := generateRandomKey(16)
+	userKey2 := generateRandomKey(16)
+
+	config := &MultiUserServerConfig{
+		Method: MethodAES128GCM,
+		Key:    masterKey,
+		Users: []*protocol.User{
+			{
+				Email:   "user1@example.com",
+				Account: serial.ToTypedMessage(&Account{Key: userKey1}),
+			},
+			{
+				Email:   "user2@example.com",
+				Account: serial.ToTypedMessage(&Account{Key: userKey2}),
+			},
+		},
+	}
+
+	testCtx := newTestContext()
+	inbound, err := NewMultiServer(testCtx, config)
+	common.Must(err)
+
+	clientConn, serverConn := gonet.Pipe()
+	defer clientConn.Close()
+	defer serverConn.Close()
+
+	dest := net.TCPDestination(net.LocalHostIP, 443)
+	method, err := GetCipherMethod(MethodAES128GCM)
+	common.Must(err)
+
+	masterRaw, _ := base64.StdEncoding.DecodeString(masterKey)
+	user2Raw, _ := base64.StdEncoding.DecodeString(userKey2)
+	clientPSKList := [][]byte{masterRaw, user2Raw}
+
+	dispatchedUserChan := make(chan string, 1)
+
+	disp := &dummyDispatcher{
+		onDispatch: func(ctx context.Context, d net.Destination) (*transport.Link, error) {
+			inbound := session.InboundFromContext(ctx)
+			if inbound != nil && inbound.User != nil {
+				dispatchedUserChan <- inbound.User.Email
+			}
+			link := &transport.Link{
+				Reader: buf.NewReader(bytes.NewReader(nil)),
+				Writer: buf.Discard,
+			}
+			return link, nil
+		},
+	}
+
+	go func() {
+		_ = inbound.Process(testCtx, net.Network_TCP, &dummyStatConn{Conn: serverConn}, disp)
+	}()
+
+	clientSalt, writer, err := ClientHandshake(clientConn, method, clientPSKList, dest, []byte("ping"))
+	common.Must(err)
+
+	reader, _, err := ClientVerifyServerResponse(clientConn, method, user2Raw, clientSalt)
+	common.Must(err)
+	_ = writer
+	_ = reader
+
+	select {
+	case email := <-dispatchedUserChan:
+		if email != "user2@example.com" {
+			t.Fatalf("expected user2@example.com, got %s", email)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for dispatched user")
+	}
+}
+
+func TestUDPReaderWriter(t *testing.T) {
+	for _, methodName := range []string{MethodAES128GCM, MethodAES256GCM, MethodChaCha20Poly1305} {
+		t.Run(methodName, func(t *testing.T) {
+			method, err := GetCipherMethod(methodName)
+			common.Must(err)
+			rawPSK := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(rawPSK)
+
+			clientCodec, err := NewUDPPacketCodec(method, rawPSK)
+			common.Must(err)
+			serverCodec, err := NewUDPServerCodec(method, rawPSK, time.Minute)
+			common.Must(err)
+
+			dest := net.UDPDestination(net.LocalHostIP, 53)
+
+			// Client to Server
+			clientPacketBuf, err := clientCodec.EncodeClientPacket(dest, []byte("hello dns"))
+			common.Must(err)
+			defer clientPacketBuf.Release()
+
+			serverDecoded, err := serverCodec.DecodePacket(clientPacketBuf.Bytes())
+			common.Must(err)
+			if string(serverDecoded.Payload) != "hello dns" {
+				t.Fatalf("unexpected server decoded payload: %s", string(serverDecoded.Payload))
+			}
+
+			// Server to Client
+			serverPacket, err := serverCodec.EncodePacket(serverDecoded.SessionID, dest, []byte("dns response"))
+			common.Must(err)
+
+			clientDecoded, err := clientCodec.DecodePacket(serverPacket)
+			common.Must(err)
+			if string(clientDecoded.Payload) != "dns response" {
+				t.Fatalf("unexpected client decoded payload: %s", string(clientDecoded.Payload))
+			}
+
+			// Test UDPWriter and UDPReader pipeline
+			pipeR, pipeW := gonet.Pipe()
+			defer pipeR.Close()
+			defer pipeW.Close()
+
+			writer := &UDPWriter{
+				Writer:      pipeW,
+				Destination: dest,
+				Codec:       clientCodec,
+			}
+			reader := &UDPReader{
+				Reader: pipeR,
+				Codec:  clientCodec,
+			}
+
+			go func() {
+				// Simulate server echoing back as server response
+				buf := make([]byte, 2048)
+				n, err := pipeR.Read(buf)
+				if err != nil {
+					return
+				}
+				dec, err := serverCodec.DecodePacket(buf[:n])
+				if err != nil {
+					return
+				}
+				resp, err := serverCodec.EncodePacket(dec.SessionID, dest, dec.Payload)
+				if err != nil {
+					return
+				}
+				_, _ = pipeW.Write(resp)
+			}()
+
+			b := buf.New()
+			b.WriteString("piped udp packet")
+			common.Must(writer.WriteMultiBuffer(buf.MultiBuffer{b}))
+
+			received, err := reader.ReadMultiBuffer()
+			common.Must(err)
+			if received[0].String() != "piped udp packet" {
+				t.Fatalf("expected 'piped udp packet', got '%s'", received[0].String())
+			}
+		})
+	}
+}
+
+func TestTCPRequestResponse(t *testing.T) {
+	for _, methodName := range []string{MethodAES128GCM, MethodAES256GCM, MethodChaCha20Poly1305} {
+		t.Run(methodName, func(t *testing.T) {
+			method, err := GetCipherMethod(methodName)
+			common.Must(err)
+			rawPSK := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(rawPSK)
+
+			clientConn, serverConn := gonet.Pipe()
+			defer clientConn.Close()
+			defer serverConn.Close()
+
+			clientSalt := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(clientSalt)
+			dest := net.TCPDestination(net.LocalHostIP, 80)
+
+			go func() {
+				// Server side: read handshake and verify clientSalt
+				salt := make([]byte, method.KeySaltLength)
+				if _, err := io.ReadFull(serverConn, salt); err != nil {
+					t.Errorf("server read salt error: %v", err)
+					return
+				}
+				sessionKey := DeriveSessionSubKey(rawPSK, salt, method.KeySaltLength)
+				aead, err := method.NewAEAD(sessionKey)
+				if err != nil {
+					t.Errorf("server AEAD error: %v", err)
+					return
+				}
+				sReader := NewStreamReader(serverConn, aead)
+				var fixedBuf [RequestHeaderFixedChunkLength + AEADTagSize]byte
+				if _, err := io.ReadFull(serverConn, fixedBuf[:]); err != nil {
+					t.Errorf("server read fixed error: %v", err)
+					return
+				}
+				plainFixed, err := aead.Open(fixedBuf[:0], sReader.Nonce(), fixedBuf[:], nil)
+				if err != nil {
+					t.Errorf("server decrypt fixed error: %v", err)
+					return
+				}
+				IncreaseNonce(sReader.Nonce())
+
+				varLen := int(binary.BigEndian.Uint16(plainFixed[9:11]))
+				varBuf := make([]byte, varLen+AEADTagSize)
+				if _, err := io.ReadFull(serverConn, varBuf); err != nil {
+					t.Errorf("server read var error: %v", err)
+					return
+				}
+				plainVar, err := aead.Open(varBuf[:0], sReader.Nonce(), varBuf, nil)
+				if err != nil {
+					t.Errorf("server decrypt var error: %v", err)
+					return
+				}
+				IncreaseNonce(sReader.Nonce())
+
+				vBuf := buf.New()
+				vBuf.Write(plainVar)
+				receivedDest, err := ReadAddressPort(vBuf)
+				if err != nil || receivedDest != dest {
+					t.Errorf("dest mismatch: %v vs %v, err: %v", receivedDest, dest, err)
+					return
+				}
+
+				// Echo client salt back to client using WriteTCPResponse
+				sWriter, err := WriteTCPResponse(serverConn, method, rawPSK, salt, []byte("early-reply"))
+				if err != nil {
+					t.Errorf("server response error: %v", err)
+					return
+				}
+				_ = sWriter
+			}()
+
+			bodyWriter, err := WriteTCPRequest(clientConn, method, [][]byte{rawPSK}, dest, clientSalt, nil)
+			common.Must(err)
+			_ = bodyWriter
+
+			responseReader, err := ReadTCPResponse(clientConn, method, rawPSK, clientSalt)
+			common.Must(err)
+
+			mb, err := responseReader.ReadMultiBuffer()
+			common.Must(err)
+			if mb[0].String() != "early-reply" {
+				t.Fatalf("expected early-reply, got %s", mb[0].String())
+			}
+		})
+	}
+}
+
+func TestUDPReplayProtection(t *testing.T) {
+	for _, methodName := range []string{MethodAES128GCM, MethodAES256GCM, MethodChaCha20Poly1305} {
+		t.Run(methodName, func(t *testing.T) {
+			method, err := GetCipherMethod(methodName)
+			common.Must(err)
+			rawPSK := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(rawPSK)
+
+			clientCodec, err := NewUDPPacketCodec(method, rawPSK)
+			common.Must(err)
+			serverCodec, err := NewUDPServerCodec(method, rawPSK, time.Minute)
+			common.Must(err)
+
+			dest := net.UDPDestination(net.LocalHostIP, 53)
+			pktBuf, err := clientCodec.EncodeClientPacket(dest, []byte("dns 1"))
+			common.Must(err)
+			defer pktBuf.Release()
+
+			rawCopy := make([]byte, pktBuf.Len())
+			copy(rawCopy, pktBuf.Bytes())
+
+			// First decode should succeed
+			_, err = serverCodec.DecodePacket(pktBuf.Bytes())
+			if err != nil {
+				t.Fatalf("first decode failed: %v", err)
+			}
+
+			// Replay same packet wire bytes should fail with ErrPacketIdNotUnique
+			_, err = serverCodec.DecodePacket(rawCopy)
+			if err != ErrPacketIdNotUnique {
+				t.Fatalf("expected ErrPacketIdNotUnique on replay, got: %v", err)
+			}
+		})
+	}
+}
+
+func TestServerUDPSessionStabilityAndMonotonicPacketID(t *testing.T) {
+	for _, methodName := range []string{MethodAES128GCM, MethodAES256GCM, MethodChaCha20Poly1305} {
+		t.Run(methodName, func(t *testing.T) {
+			method, err := GetCipherMethod(methodName)
+			common.Must(err)
+			rawPSK := make([]byte, method.KeySaltLength)
+			_, _ = rand.Read(rawPSK)
+
+			clientCodec, err := NewUDPPacketCodec(method, rawPSK)
+			common.Must(err)
+			serverCodec, err := NewUDPServerCodec(method, rawPSK, time.Minute)
+			common.Must(err)
+
+			dest := net.UDPDestination(net.LocalHostIP, 53)
+
+			// Client sends packet 1
+			pkt1, err := clientCodec.EncodeClientPacket(dest, []byte("request 1"))
+			common.Must(err)
+			defer pkt1.Release()
+
+			dec1, err := serverCodec.DecodePacket(pkt1.Bytes())
+			common.Must(err)
+
+			// Server sends response 1
+			resp1, err := serverCodec.EncodePacket(dec1.SessionID, dest, []byte("response 1"))
+			common.Must(err)
+
+			// Server sends response 2 to the same client session
+			resp2, err := serverCodec.EncodePacket(dec1.SessionID, dest, []byte("response 2"))
+			common.Must(err)
+
+			// Decode both on client
+			cDec1, err := clientCodec.DecodePacket(resp1)
+			common.Must(err)
+			cDec2, err := clientCodec.DecodePacket(resp2)
+			common.Must(err)
+
+			if cDec1.SessionID != cDec2.SessionID {
+				t.Fatalf("expected stable server session ID, got %d and %d", cDec1.SessionID, cDec2.SessionID)
+			}
+			if cDec2.PacketID <= cDec1.PacketID {
+				t.Fatalf("expected monotonically increasing packet ID, got %d then %d", cDec1.PacketID, cDec2.PacketID)
+			}
+			if string(cDec1.Payload) != "response 1" || string(cDec2.Payload) != "response 2" {
+				t.Fatalf("payload mismatch")
+			}
+		})
+	}
+}
+
+type mockDialer struct {
+	dial func(ctx context.Context, dest net.Destination) (stat.Connection, error)
+}
+
+func (d *mockDialer) Dial(ctx context.Context, dest net.Destination) (stat.Connection, error) {
+	if d.dial != nil {
+		return d.dial(ctx, dest)
+	}
+	c1, c2 := gonet.Pipe()
+	_ = c2.Close()
+	return &dummyStatConn{Conn: c1}, nil
+}
+
+func (d *mockDialer) DestIpAddress() net.IP {
+	return net.IP{127, 0, 0, 1}
+}
+
+func (d *mockDialer) SetOutboundGateway(ctx context.Context, ob *session.Outbound) {}
+
+func TestOutboundProcess(t *testing.T) {
+	testCtx := newTestContext()
+	key := generateRandomKey(16)
+	clientConfig := &ClientConfig{
+		Address: &net.IPOrDomain{Address: &net.IPOrDomain_Ip{Ip: []byte{127, 0, 0, 1}}},
+		Port:    1080,
+		Method:  MethodAES128GCM,
+		Key:     key,
+	}
+
+	outbound, err := NewClient(testCtx, clientConfig)
+	common.Must(err)
+
+	ctx := session.ContextWithOutbounds(testCtx, []*session.Outbound{
+		{
+			Target: net.TCPDestination(net.LocalHostIP, 80),
+		},
+	})
+
+	link := &transport.Link{
+		Reader: buf.NewReader(bytes.NewReader(nil)),
+		Writer: buf.Discard,
+	}
+
+	dialer := &mockDialer{}
+	err = outbound.Process(ctx, link, dialer)
+	if err == nil {
+		t.Fatal("expected error from closed mock dialer pipe, got nil")
+	}
+}

proxy/shadowsocks_2022/stream.go

@@ -0,0 +1,540 @@
+package shadowsocks_2022
+
+import (
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/binary"
+	"io"
+	"math"
+	mrand "math/rand"
+	"time"
+
+	"github.com/xtls/xray-core/common/buf"
+	"github.com/xtls/xray-core/common/errors"
+	"github.com/xtls/xray-core/common/net"
+	"github.com/xtls/xray-core/common/protocol"
+)
+
+var addrParser = protocol.NewAddressParser(
+	protocol.AddressFamilyByte(0x01, net.AddressFamilyIPv4),
+	protocol.AddressFamilyByte(0x04, net.AddressFamilyIPv6),
+	protocol.AddressFamilyByte(0x03, net.AddressFamilyDomain),
+	protocol.WithAddressTypeParser(func(b byte) byte {
+		return b & 0x0F
+	}),
+)
+
+func IncreaseNonce(nonce []byte) {
+	for i := range nonce {
+		nonce[i]++
+		if nonce[i] != 0 {
+			return
+		}
+	}
+}
+
+// WriteAddressPort writes a destination address and port in SOCKS5 format
+func WriteAddressPort(w io.Writer, dest net.Destination) error {
+	return addrParser.WriteAddressPort(w, dest.Address, dest.Port)
+}
+
+// ReadAddressPort reads a destination address and port in SOCKS5 format
+func ReadAddressPort(r io.Reader) (net.Destination, error) {
+	addr, port, err := addrParser.ReadAddressPort(nil, r)
+	if err != nil {
+		return net.Destination{}, err
+	}
+	return net.TCPDestination(addr, port), nil
+}
+
+// AddrPortLength returns the serialized length of a destination in SOCKS5 format
+func AddrPortLength(dest net.Destination) int {
+	switch dest.Address.Family() {
+	case net.AddressFamilyIPv4:
+		return 1 + 4 + 2
+	case net.AddressFamilyDomain:
+		return 1 + 1 + len(dest.Address.Domain()) + 2
+	case net.AddressFamilyIPv6:
+		return 1 + 16 + 2
+	default:
+		return 0
+	}
+}
+
+type StreamWriter struct {
+	writer io.Writer
+	cipher cipher.AEAD
+	nonce  [StreamNonceSize]byte
+	lenBuf [2]byte
+	buf    []byte
+}
+
+func NewStreamWriter(w io.Writer, c cipher.AEAD) *StreamWriter {
+	return &StreamWriter{
+		writer: w,
+		cipher: c,
+		buf:    make([]byte, 0, MaxPacketSize+2+2*AEADTagSize),
+	}
+}
+
+func (w *StreamWriter) Nonce() []byte {
+	return w.nonce[:]
+}
+
+func (w *StreamWriter) Cipher() cipher.AEAD {
+	return w.cipher
+}
+
+func (w *StreamWriter) WriteChunk(payload []byte) error {
+	payloadLen := len(payload)
+	if payloadLen == 0 {
+		return nil
+	}
+	if payloadLen > MaxPacketSize {
+		return errors.New("payload exceeds MaxPacketSize")
+	}
+
+	binary.BigEndian.PutUint16(w.lenBuf[:], uint16(payloadLen))
+	w.buf = w.cipher.Seal(w.buf[:0], w.nonce[:], w.lenBuf[:], nil)
+	IncreaseNonce(w.nonce[:])
+
+	w.buf = w.cipher.Seal(w.buf, w.nonce[:], payload, nil)
+	IncreaseNonce(w.nonce[:])
+
+	_, err := w.writer.Write(w.buf)
+	return err
+}
+
+func (w *StreamWriter) Write(p []byte) (int, error) {
+	n := len(p)
+	for len(p) > 0 {
+		chunkSize := len(p)
+		if chunkSize > MaxPacketSize {
+			chunkSize = MaxPacketSize
+		}
+		if err := w.WriteChunk(p[:chunkSize]); err != nil {
+			return 0, err
+		}
+		p = p[chunkSize:]
+	}
+	return n, nil
+}
+
+func (w *StreamWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
+	defer buf.ReleaseMulti(mb)
+	for _, b := range mb {
+		if err := w.WriteChunk(b.Bytes()); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+type StreamReader struct {
+	reader io.Reader
+	cipher cipher.AEAD
+	nonce  [StreamNonceSize]byte
+	lenBuf [2 + AEADTagSize]byte
+	buffer []byte
+	cached int
+	offset int
+}
+
+func NewStreamReader(r io.Reader, c cipher.AEAD) *StreamReader {
+	return &StreamReader{
+		reader: r,
+		cipher: c,
+		buffer: make([]byte, MaxPacketSize+AEADTagSize),
+	}
+}
+
+func (r *StreamReader) Nonce() []byte {
+	return r.nonce[:]
+}
+
+func (r *StreamReader) Cipher() cipher.AEAD {
+	return r.cipher
+}
+
+func (r *StreamReader) Read(p []byte) (int, error) {
+	if r.cached > 0 {
+		n := copy(p, r.buffer[r.offset:r.offset+r.cached])
+		r.cached -= n
+		r.offset += n
+		return n, nil
+	}
+
+	// Read 2-byte length + AEAD tag (18 bytes)
+	if _, err := io.ReadFull(r.reader, r.lenBuf[:]); err != nil {
+		return 0, err
+	}
+
+	decryptedLen, err := r.cipher.Open(r.lenBuf[:0], r.nonce[:], r.lenBuf[:], nil)
+	if err != nil {
+		return 0, errors.New("failed to decrypt chunk length").Base(err)
+	}
+	IncreaseNonce(r.nonce[:])
+
+	payloadLen := int(binary.BigEndian.Uint16(decryptedLen))
+	if payloadLen == 0 {
+		return 0, nil
+	}
+
+	chunkEnd := payloadLen + AEADTagSize
+	if _, err := io.ReadFull(r.reader, r.buffer[:chunkEnd]); err != nil {
+		return 0, err
+	}
+
+	decryptedPayload, err := r.cipher.Open(r.buffer[:0], r.nonce[:], r.buffer[:chunkEnd], nil)
+	if err != nil {
+		return 0, errors.New("failed to decrypt chunk payload").Base(err)
+	}
+	IncreaseNonce(r.nonce[:])
+
+	r.cached = len(decryptedPayload)
+	r.offset = 0
+
+	n := copy(p, r.buffer[r.offset:r.offset+r.cached])
+	r.cached -= n
+	r.offset += n
+	return n, nil
+}
+
+func (r *StreamReader) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	if r.cached > 0 {
+		b := buf.New()
+		b.Write(r.buffer[r.offset : r.offset+r.cached])
+		r.cached = 0
+		r.offset = 0
+		return buf.MultiBuffer{b}, nil
+	}
+
+	if _, err := io.ReadFull(r.reader, r.lenBuf[:]); err != nil {
+		return nil, err
+	}
+
+	decryptedLen, err := r.cipher.Open(r.lenBuf[:0], r.nonce[:], r.lenBuf[:], nil)
+	if err != nil {
+		return nil, errors.New("failed to decrypt chunk length").Base(err)
+	}
+	IncreaseNonce(r.nonce[:])
+
+	payloadLen := int(binary.BigEndian.Uint16(decryptedLen))
+	if payloadLen == 0 {
+		return nil, nil
+	}
+
+	chunkEnd := payloadLen + AEADTagSize
+	if _, err := io.ReadFull(r.reader, r.buffer[:chunkEnd]); err != nil {
+		return nil, err
+	}
+
+	decryptedPayload, err := r.cipher.Open(r.buffer[:0], r.nonce[:], r.buffer[:chunkEnd], nil)
+	if err != nil {
+		return nil, errors.New("failed to decrypt chunk payload").Base(err)
+	}
+	IncreaseNonce(r.nonce[:])
+
+	b := buf.New()
+	b.Write(decryptedPayload)
+	return buf.MultiBuffer{b}, nil
+}
+
+type ClientRequestHeader struct {
+	Destination net.Destination
+	EarlyData   []byte
+}
+
+func ReadClientRequestHeader(conn io.Reader, reader *StreamReader) (*ClientRequestHeader, error) {
+	var fixedBuf [RequestHeaderFixedChunkLength + AEADTagSize]byte
+	if _, err := io.ReadFull(conn, fixedBuf[:]); err != nil {
+		return nil, err
+	}
+
+	plainFixed, err := reader.cipher.Open(fixedBuf[:0], reader.Nonce(), fixedBuf[:], nil)
+	if err != nil {
+		return nil, errors.New("failed to decrypt client request header").Base(err)
+	}
+	IncreaseNonce(reader.Nonce())
+
+	if plainFixed[0] != HeaderTypeClient {
+		return nil, ErrBadHeaderType
+	}
+
+	epoch := binary.BigEndian.Uint64(plainFixed[1:9])
+	diff := int(math.Abs(float64(time.Now().Unix() - int64(epoch))))
+	if diff > 30 {
+		return nil, ErrBadTimestamp
+	}
+
+	varHeaderLen := int(binary.BigEndian.Uint16(plainFixed[9:11]))
+	if varHeaderLen == 0 {
+		return nil, ErrInvalidRequest
+	}
+
+	var stackVarChunk [512]byte
+	var varChunkCipher []byte
+	needed := varHeaderLen + AEADTagSize
+	if needed <= len(stackVarChunk) {
+		varChunkCipher = stackVarChunk[:needed]
+	} else {
+		varChunkCipher = make([]byte, needed)
+	}
+	if _, err := io.ReadFull(conn, varChunkCipher); err != nil {
+		return nil, err
+	}
+
+	plainVar, err := reader.cipher.Open(varChunkCipher[:0], reader.Nonce(), varChunkCipher, nil)
+	if err != nil {
+		return nil, errors.New("failed to decrypt variable request header").Base(err)
+	}
+	IncreaseNonce(reader.Nonce())
+
+	b := buf.New()
+	b.Write(plainVar)
+	defer b.Release()
+
+	dest, err := ReadAddressPort(b)
+	if err != nil {
+		return nil, err
+	}
+
+	var padLenBytes [2]byte
+	if _, err := b.Read(padLenBytes[:]); err != nil {
+		return nil, err
+	}
+	paddingLen := int(binary.BigEndian.Uint16(padLenBytes[:]))
+	if int(b.Len()) < paddingLen {
+		return nil, ErrNoPadding
+	}
+	if paddingLen > 0 {
+		b.Advance(int32(paddingLen))
+	}
+
+	var earlyData []byte
+	if b.Len() > 0 {
+		earlyData = make([]byte, b.Len())
+		copy(earlyData, b.Bytes())
+	}
+
+	return &ClientRequestHeader{
+		Destination: dest,
+		EarlyData:   earlyData,
+	}, nil
+}
+
+// ClientHandshake writes the full client request header to w
+func ClientHandshake(w io.Writer, method *CipherMethod, pskList [][]byte, dest net.Destination, payload []byte) ([]byte, *StreamWriter, error) {
+	salt := make([]byte, method.KeySaltLength)
+	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
+		return nil, nil, err
+	}
+	writer, err := WriteTCPRequest(w, method, pskList, dest, salt, payload)
+	if err != nil {
+		return nil, nil, err
+	}
+	return salt, writer.(*StreamWriter), nil
+}
+
+// ClientVerifyServerResponse reads and verifies the server's handshake response
+func ClientVerifyServerResponse(r io.Reader, method *CipherMethod, psk []byte, clientSalt []byte) (*StreamReader, []byte, error) {
+	reader, err := ReadTCPResponse(r, method, psk, clientSalt)
+	if err != nil {
+		return nil, nil, err
+	}
+	sr := reader.(*StreamReader)
+	var initialPayload []byte
+	if sr.cached > 0 {
+		initialPayload = make([]byte, sr.cached)
+		copy(initialPayload, sr.buffer[sr.offset:sr.offset+sr.cached])
+	}
+	return sr, initialPayload, nil
+}
+
+// WriteTCPRequest writes the Shadowsocks 2022 request header into w and returns a body writer.
+func WriteTCPRequest(w io.Writer, method *CipherMethod, pskList [][]byte, dest net.Destination, clientSalt []byte, payload []byte) (buf.Writer, error) {
+	finalPSK := pskList[len(pskList)-1]
+	sessionKey := DeriveSessionSubKey(finalPSK, clientSalt, method.KeySaltLength)
+	aead, err := method.NewAEAD(sessionKey)
+	if err != nil {
+		return nil, err
+	}
+
+	writer := NewStreamWriter(w, aead)
+
+	handshakeBuf := buf.New()
+	defer handshakeBuf.Release()
+
+	handshakeBuf.Write(clientSalt)
+
+	if len(pskList) > 1 {
+		for i := 0; i < len(pskList)-1; i++ {
+			currPSK := pskList[i]
+			identitySubkey := DeriveIdentitySubKey(currPSK, clientSalt, method.KeySaltLength)
+			block, err := method.NewBlock(identitySubkey)
+			if err != nil {
+				return nil, err
+			}
+			nextPSK := pskList[i+1]
+			pskHash := DeriveUserPSKHash(nextPSK)
+			var encryptedEIH [AESBlockSize]byte
+			block.Encrypt(encryptedEIH[:], pskHash[:])
+			handshakeBuf.Write(encryptedEIH[:])
+		}
+	}
+
+	payloadLen := len(payload)
+	var paddingLen int
+	if payloadLen < MaxPaddingLength {
+		paddingLen = mrand.Intn(MaxPaddingLength-payloadLen) + 1
+	}
+	addrPortLen := AddrPortLength(dest)
+	varHeaderLen := addrPortLen + 2 + paddingLen + payloadLen
+
+	var fixedHeaderPlaintext [RequestHeaderFixedChunkLength]byte
+	fixedHeaderPlaintext[0] = HeaderTypeClient
+	binary.BigEndian.PutUint64(fixedHeaderPlaintext[1:9], uint64(time.Now().Unix()))
+	binary.BigEndian.PutUint16(fixedHeaderPlaintext[9:11], uint16(varHeaderLen))
+
+	fixedChunk := writer.cipher.Seal(nil, writer.nonce[:], fixedHeaderPlaintext[:], nil)
+	IncreaseNonce(writer.nonce[:])
+	handshakeBuf.Write(fixedChunk)
+
+	varHeaderBuf := buf.New()
+	defer varHeaderBuf.Release()
+
+	if err := WriteAddressPort(varHeaderBuf, dest); err != nil {
+		return nil, err
+	}
+
+	var padLenBytes [2]byte
+	binary.BigEndian.PutUint16(padLenBytes[:], uint16(paddingLen))
+	varHeaderBuf.Write(padLenBytes[:])
+
+	if paddingLen > 0 {
+		varHeaderBuf.Write(zeroPadding[:paddingLen])
+	}
+
+	if payloadLen > 0 {
+		varHeaderBuf.Write(payload)
+	}
+
+	varChunk := writer.cipher.Seal(nil, writer.nonce[:], varHeaderBuf.Bytes(), nil)
+	IncreaseNonce(writer.nonce[:])
+	handshakeBuf.Write(varChunk)
+
+	if _, err := w.Write(handshakeBuf.Bytes()); err != nil {
+		return nil, err
+	}
+
+	return writer, nil
+}
+
+// ReadTCPResponse reads and verifies the server's handshake response and returns a reader for the stream.
+func ReadTCPResponse(r io.Reader, method *CipherMethod, psk []byte, clientSalt []byte) (buf.Reader, error) {
+	var serverSalt [32]byte
+	serverSaltSlice := serverSalt[:method.KeySaltLength]
+	if _, err := io.ReadFull(r, serverSaltSlice); err != nil {
+		return nil, err
+	}
+
+	sessionKey := DeriveSessionSubKey(psk, serverSaltSlice, method.KeySaltLength)
+	aead, err := method.NewAEAD(sessionKey)
+	if err != nil {
+		return nil, err
+	}
+
+	reader := NewStreamReader(r, aead)
+
+	fixedPlainLen := 1 + 8 + method.KeySaltLength + 2
+	chunkCipherLen := fixedPlainLen + AEADTagSize
+	var chunkBuf [64]byte
+	chunkSlice := chunkBuf[:chunkCipherLen]
+	if _, err := io.ReadFull(r, chunkSlice); err != nil {
+		return nil, err
+	}
+
+	decryptedFixed, err := reader.cipher.Open(chunkSlice[:0], reader.nonce[:], chunkSlice, nil)
+	if err != nil {
+		return nil, errors.New("failed to decrypt server response header").Base(err)
+	}
+	IncreaseNonce(reader.nonce[:])
+
+	if decryptedFixed[0] != HeaderTypeServer {
+		return nil, ErrBadHeaderType
+	}
+
+	serverEpoch := binary.BigEndian.Uint64(decryptedFixed[1:9])
+	diff := int(math.Abs(float64(time.Now().Unix() - int64(serverEpoch))))
+	if diff > 30 {
+		return nil, ErrBadTimestamp
+	}
+
+	echoedSalt := decryptedFixed[9 : 9+method.KeySaltLength]
+	for i := 0; i < method.KeySaltLength; i++ {
+		if echoedSalt[i] != clientSalt[i] {
+			return nil, errors.New("bad request salt")
+		}
+	}
+
+	initialPayloadLen := int(binary.BigEndian.Uint16(decryptedFixed[9+method.KeySaltLength : 11+method.KeySaltLength]))
+	if initialPayloadLen > 0 {
+		initialCipherLen := initialPayloadLen + AEADTagSize
+		if _, err := io.ReadFull(r, reader.buffer[:initialCipherLen]); err != nil {
+			return nil, err
+		}
+		decryptedInitial, err := reader.cipher.Open(reader.buffer[:0], reader.nonce[:], reader.buffer[:initialCipherLen], nil)
+		if err != nil {
+			return nil, errors.New("failed to decrypt initial response payload").Base(err)
+		}
+		IncreaseNonce(reader.nonce[:])
+		reader.cached = len(decryptedInitial)
+		reader.offset = 0
+	}
+
+	return reader, nil
+}
+
+// WriteTCPResponse writes the server handshake response and returns a body writer for server stream.
+func WriteTCPResponse(w io.Writer, method *CipherMethod, psk []byte, clientSalt []byte, initialPayload []byte) (buf.Writer, error) {
+	var serverSalt [32]byte
+	serverSaltSlice := serverSalt[:method.KeySaltLength]
+	if _, err := io.ReadFull(rand.Reader, serverSaltSlice); err != nil {
+		return nil, err
+	}
+
+	respKey := DeriveSessionSubKey(psk, serverSaltSlice, method.KeySaltLength)
+	respAead, err := method.NewAEAD(respKey)
+	if err != nil {
+		return nil, err
+	}
+	writer := NewStreamWriter(w, respAead)
+
+	respBuf := buf.New()
+	defer respBuf.Release()
+
+	respBuf.Write(serverSaltSlice)
+
+	var fixedRespPlain [1 + 8 + 32 + 2]byte
+	fixedRespSlice := fixedRespPlain[:1+8+method.KeySaltLength+2]
+	fixedRespSlice[0] = HeaderTypeServer
+	binary.BigEndian.PutUint64(fixedRespSlice[1:9], uint64(time.Now().Unix()))
+	copy(fixedRespSlice[9:9+method.KeySaltLength], clientSalt)
+	binary.BigEndian.PutUint16(fixedRespSlice[9+method.KeySaltLength:11+method.KeySaltLength], uint16(len(initialPayload)))
+
+	fixedRespChunk := writer.cipher.Seal(nil, writer.nonce[:], fixedRespSlice, nil)
+	IncreaseNonce(writer.nonce[:])
+	respBuf.Write(fixedRespChunk)
+
+	if len(initialPayload) > 0 {
+		initialChunk := writer.cipher.Seal(nil, writer.nonce[:], initialPayload, nil)
+		IncreaseNonce(writer.nonce[:])
+		respBuf.Write(initialChunk)
+	}
+
+	if _, err := w.Write(respBuf.Bytes()); err != nil {
+		return nil, err
+	}
+
+	return writer, nil
+}

testing/scenarios/shadowsocks_2022_test.go

@@ -6,7 +6,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/sagernet/sing-shadowsocks/shadowaead_2022"
 	"github.com/xtls/xray-core/app/log"
 	"github.com/xtls/xray-core/app/proxyman"
 	"github.com/xtls/xray-core/common"
@@ -22,9 +21,19 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
+var ss2022Methods = []string{
+	shadowsocks_2022.MethodAES128GCM,
+	shadowsocks_2022.MethodAES256GCM,
+	shadowsocks_2022.MethodChaCha20Poly1305,
+}
+
 func TestShadowsocks2022Tcp(t *testing.T) {
-	for _, method := range shadowaead_2022.List {
-		password := make([]byte, 32)
+	for _, method := range ss2022Methods {
+		keySize := 32
+		if method == shadowsocks_2022.MethodAES128GCM {
+			keySize = 16
+		}
+		password := make([]byte, keySize)
 		rand.Read(password)
 		t.Run(method, func(t *testing.T) {
 			testShadowsocks2022Tcp(t, method, base64.StdEncoding.EncodeToString(password))
@@ -33,21 +42,21 @@ func TestShadowsocks2022Tcp(t *testing.T) {
 }
 
 func TestShadowsocks2022UdpAES128(t *testing.T) {
-	password := make([]byte, 32)
+	password := make([]byte, 16)
 	rand.Read(password)
-	testShadowsocks2022Udp(t, shadowaead_2022.List[0], base64.StdEncoding.EncodeToString(password))
+	testShadowsocks2022Udp(t, shadowsocks_2022.MethodAES128GCM, base64.StdEncoding.EncodeToString(password))
 }
 
 func TestShadowsocks2022UdpAES256(t *testing.T) {
 	password := make([]byte, 32)
 	rand.Read(password)
-	testShadowsocks2022Udp(t, shadowaead_2022.List[1], base64.StdEncoding.EncodeToString(password))
+	testShadowsocks2022Udp(t, shadowsocks_2022.MethodAES256GCM, base64.StdEncoding.EncodeToString(password))
 }
 
 func TestShadowsocks2022UdpChacha(t *testing.T) {
 	password := make([]byte, 32)
 	rand.Read(password)
-	testShadowsocks2022Udp(t, shadowaead_2022.List[2], base64.StdEncoding.EncodeToString(password))
+	testShadowsocks2022Udp(t, shadowsocks_2022.MethodChaCha20Poly1305, base64.StdEncoding.EncodeToString(password))
 }
 
 func testShadowsocks2022Tcp(t *testing.T, method string, password string) {