socks: Add custom udp listener

protocol/socks/handshake.go

@@ -25,6 +25,10 @@ type HandlerEx interface {
 	N.UDPConnectionHandlerEx
 }
 
+type PacketListener interface {
+	ListenPacket(listenConfig net.ListenConfig, ctx context.Context, network string, address string) (net.PacketConn, error)
+}
+
 func ClientHandshake4(conn io.ReadWriter, command byte, destination M.Socksaddr, username string) (socks4.Response, error) {
 	err := socks4.WriteRequest(conn, socks4.Request{
 		Command:     command,
@@ -121,6 +125,8 @@ func HandleConnectionEx(
 	ctx context.Context, conn net.Conn, reader *std_bufio.Reader,
 	authenticator *auth.Authenticator,
 	handler HandlerEx,
+	packetListener PacketListener,
+	// resolver TorResolver,
 	source M.Socksaddr,
 	onClose N.CloseHandlerFunc,
 ) error {
@@ -148,6 +154,11 @@ func HandleConnectionEx(
 			}
 			handler.NewConnectionEx(auth.ContextWithUser(ctx, request.Username), NewLazyConn(conn, version), source, request.Destination, onClose)
 			return nil
+		/*case CommandTorResolve, CommandTorResolvePTR:
+		if resolver == nil {
+			return E.New("socks4: torsocks: commands not implemented")
+		}
+		return handleTorSocks4(ctx, conn, request, resolver)*/
 		default:
 			err = socks4.WriteResponse(conn, socks4.Response{
 				ReplyCode: socks4.ReplyCodeRejectedOrFailed,
@@ -214,8 +225,15 @@ func HandleConnectionEx(
 			handler.NewConnectionEx(ctx, NewLazyConn(conn, version), source, request.Destination, onClose)
 			return nil
 		case socks5.CommandUDPAssociate:
-			var udpConn *net.UDPConn
+			var (
-			udpConn, err = net.ListenUDP(M.NetworkFromNetAddr("udp", M.AddrFromNet(conn.LocalAddr())), net.UDPAddrFromAddrPort(netip.AddrPortFrom(M.AddrFromNet(conn.LocalAddr()), 0)))
+				listenConfig net.ListenConfig
+				udpConn      net.PacketConn
+			)
+			if packetListener != nil {
+				udpConn, err = packetListener.ListenPacket(listenConfig, ctx, M.NetworkFromNetAddr("udp", M.AddrFromNet(conn.LocalAddr())), M.SocksaddrFrom(M.AddrFromNet(conn.LocalAddr()), 0).String())
+			} else {
+				udpConn, err = listenConfig.ListenPacket(ctx, M.NetworkFromNetAddr("udp", M.AddrFromNet(conn.LocalAddr())), M.SocksaddrFrom(M.AddrFromNet(conn.LocalAddr()), 0).String())
+			}
 			if err != nil {
 				return E.Cause(err, "socks5: listen udp")
 			}
@@ -236,6 +254,11 @@ func HandleConnectionEx(
 			socksPacketConn = bufio.NewCachedPacketConn(socksPacketConn, firstPacket, destination)
 			handler.NewPacketConnectionEx(ctx, socksPacketConn, source, destination, onClose)
 			return nil
+		/*case CommandTorResolve, CommandTorResolvePTR:
+		if resolver == nil {
+			return E.New("socks4: torsocks: commands not implemented")
+		}
+		return handleTorSocks5(ctx, conn, request, resolver)*/
 		default:
 			err = socks5.WriteResponse(conn, socks5.Response{
 				ReplyCode: socks5.ReplyCodeUnsupported,

protocol/socks/handshake_tor.go

@@ -0,0 +1,146 @@
+package socks
+
+import (
+	"context"
+	"net"
+	"net/netip"
+	"os"
+	"strings"
+
+	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
+	"github.com/sagernet/sing/protocol/socks/socks4"
+	"github.com/sagernet/sing/protocol/socks/socks5"
+)
+
+const (
+	CommandTorResolve    byte = 0xF0
+	CommandTorResolvePTR byte = 0xF1
+)
+
+type TorResolver interface {
+	LookupIP(ctx context.Context, host string) (netip.Addr, error)
+	LookupPTR(ctx context.Context, addr netip.Addr) (string, error)
+}
+
+func handleTorSocks4(ctx context.Context, conn net.Conn, request socks4.Request, resolver TorResolver) error {
+	switch request.Command {
+	case CommandTorResolve:
+		if !request.Destination.IsFqdn() {
+			return E.New("socks4: torsocks: invalid destination")
+		}
+		ipAddr, err := resolver.LookupIP(ctx, request.Destination.Fqdn)
+		if err != nil {
+			err = socks4.WriteResponse(conn, socks4.Response{
+				ReplyCode: socks4.ReplyCodeRejectedOrFailed,
+			})
+			if err != nil {
+				return err
+			}
+			return E.Cause(err, "socks4: torsocks: lookup failed for domain: ", request.Destination.Fqdn)
+		}
+		err = socks4.WriteResponse(conn, socks4.Response{
+			ReplyCode:   socks4.ReplyCodeGranted,
+			Destination: M.SocksaddrFrom(ipAddr, 0),
+		})
+		if err != nil {
+			return E.Cause(err, "socks4: torsocks: write response")
+		}
+		return nil
+	case CommandTorResolvePTR:
+		var ipAddr netip.Addr
+		if request.Destination.IsIP() {
+			ipAddr = request.Destination.Addr
+		} else if strings.HasSuffix(request.Destination.Fqdn, ".in-addr.arpa") {
+			ipAddr, _ = netip.ParseAddr(request.Destination.Fqdn[:len(request.Destination.Fqdn)-len(".in-addr.arpa")])
+		} else if strings.HasSuffix(request.Destination.Fqdn, ".ip6.arpa") {
+			ipAddr, _ = netip.ParseAddr(strings.ReplaceAll(request.Destination.Fqdn[:len(request.Destination.Fqdn)-len(".ip6.arpa")], ".", ":"))
+		}
+		if !ipAddr.IsValid() {
+			return E.New("socks4: torsocks: invalid destination")
+		}
+		host, err := resolver.LookupPTR(ctx, ipAddr)
+		if err != nil {
+			err = socks4.WriteResponse(conn, socks4.Response{
+				ReplyCode: socks4.ReplyCodeRejectedOrFailed,
+			})
+			if err != nil {
+				return err
+			}
+			return E.Cause(err, "socks4: torsocks: lookup PTR failed for ip: ", ipAddr)
+		}
+		err = socks4.WriteResponse(conn, socks4.Response{
+			ReplyCode: socks4.ReplyCodeGranted,
+			Destination: M.Socksaddr{
+				Fqdn: host,
+			},
+		})
+		if err != nil {
+			return E.Cause(err, "socks4: torsocks: write response")
+		}
+		return nil
+	default:
+		return os.ErrInvalid
+	}
+}
+
+func handleTorSocks5(ctx context.Context, conn net.Conn, request socks5.Request, resolver TorResolver) error {
+	switch request.Command {
+	case CommandTorResolve:
+		if !request.Destination.IsFqdn() {
+			return E.New("socks5: torsocks: invalid destination")
+		}
+		ipAddr, err := resolver.LookupIP(ctx, request.Destination.Fqdn)
+		if err != nil {
+			err = socks5.WriteResponse(conn, socks5.Response{
+				ReplyCode: socks5.ReplyCodeFailure,
+			})
+			if err != nil {
+				return err
+			}
+			return E.Cause(err, "socks5: torsocks: lookup failed for domain: ", request.Destination.Fqdn)
+		}
+		err = socks5.WriteResponse(conn, socks5.Response{
+			ReplyCode: socks5.ReplyCodeSuccess,
+			Bind:      M.SocksaddrFrom(ipAddr, 0),
+		})
+		if err != nil {
+			return E.Cause(err, "socks5: torsocks: write response")
+		}
+		return nil
+	case CommandTorResolvePTR:
+		var ipAddr netip.Addr
+		if request.Destination.IsIP() {
+			ipAddr = request.Destination.Addr
+		} else if strings.HasSuffix(request.Destination.Fqdn, ".in-addr.arpa") {
+			ipAddr, _ = netip.ParseAddr(request.Destination.Fqdn[:len(request.Destination.Fqdn)-len(".in-addr.arpa")])
+		} else if strings.HasSuffix(request.Destination.Fqdn, ".ip6.arpa") {
+			ipAddr, _ = netip.ParseAddr(strings.ReplaceAll(request.Destination.Fqdn[:len(request.Destination.Fqdn)-len(".ip6.arpa")], ".", ":"))
+		}
+		if !ipAddr.IsValid() {
+			return E.New("socks5: torsocks: invalid destination")
+		}
+		host, err := resolver.LookupPTR(ctx, ipAddr)
+		if err != nil {
+			err = socks5.WriteResponse(conn, socks5.Response{
+				ReplyCode: socks5.ReplyCodeFailure,
+			})
+			if err != nil {
+				return err
+			}
+			return E.Cause(err, "socks5: torsocks: lookup PTR failed for ip: ", ipAddr)
+		}
+		err = socks5.WriteResponse(conn, socks5.Response{
+			ReplyCode: socks5.ReplyCodeSuccess,
+			Bind: M.Socksaddr{
+				Fqdn: host,
+			},
+		})
+		if err != nil {
+			return E.Cause(err, "socks5: torsocks: write response")
+		}
+		return nil
+	default:
+		return os.ErrInvalid
+	}
+}