Three types of ALPN for post-handshake records detection & imitation

XTLS/Xray-core#4778 (comment)

Author: RPRX

record_detect.go

@@ -5,6 +5,7 @@ import (
 	"encoding/binary"
 	"io"
 	"net"
+	"strconv"
 	"sync"
 	"time"
 
@@ -16,36 +17,50 @@ var GlobalPostHandshakeRecordsLens sync.Map
 
 func DetectPostHandshakeRecordsLens(config *Config) {
 	for sni := range config.ServerNames {
-		key := config.Dest + " " + sni
-		if _, loaded := GlobalPostHandshakeRecordsLens.LoadOrStore(key, false); !loaded {
-			go func() {
-				defer func() {
-					val, _ := GlobalPostHandshakeRecordsLens.Load(key)
-					if _, ok := val.(bool); ok {
-						GlobalPostHandshakeRecordsLens.Store(key, []int{})
+		for alpn := range 3 { // 0, 1, 2
+			key := config.Dest + " " + sni + " " + strconv.Itoa(alpn)
+			if _, loaded := GlobalPostHandshakeRecordsLens.LoadOrStore(key, false); !loaded {
+				go func() {
+					defer func() {
+						val, _ := GlobalPostHandshakeRecordsLens.Load(key)
+						if _, ok := val.(bool); ok {
+							GlobalPostHandshakeRecordsLens.Store(key, []int{})
+						}
+					}()
+					target, err := net.Dial("tcp", config.Dest)
+					if err != nil {
+						return
 					}
-				}()
-				target, err := net.Dial("tcp", config.Dest)
-				if err != nil {
-					return
-				}
-				if config.Xver == 1 || config.Xver == 2 {
-					if _, err = proxyproto.HeaderProxyFromAddrs(config.Xver, target.LocalAddr(), target.RemoteAddr()).WriteTo(target); err != nil {
+					if config.Xver == 1 || config.Xver == 2 {
+						if _, err = proxyproto.HeaderProxyFromAddrs(config.Xver, target.LocalAddr(), target.RemoteAddr()).WriteTo(target); err != nil {
+							return
+						}
+					}
+					detectConn := &DetectConn{
+						Conn: target,
+						Key:  key,
+					}
+					fingerprint := utls.HelloChrome_Auto
+					nextProtos := []string{"h2", "http/1.1"}
+					if alpn != 2 {
+						fingerprint = utls.HelloGolang
+					}
+					if alpn == 1 {
+						nextProtos = []string{"http/1.1"}
+					}
+					if alpn == 0 {
+						nextProtos = nil
+					}
+					uConn := utls.UClient(detectConn, &utls.Config{
+						ServerName: sni, // needs new loopvar behaviour
+						NextProtos: nextProtos,
+					}, fingerprint)
+					if err = uConn.Handshake(); err != nil {
 						return
 					}
-				}
-				detectConn := &DetectConn{
-					Conn: target,
-					Key:  key,
-				}
-				uConn := utls.UClient(detectConn, &utls.Config{
-					ServerName: sni, // needs new loopvar behaviour
-				}, utls.HelloChrome_Auto)
-				if err = uConn.Handshake(); err != nil {
-					return
-				}
-				io.Copy(io.Discard, uConn)
-			}()
+					io.Copy(io.Discard, uConn)
+				}()
+			}
 		}
 	}
 }

tls.go

@@ -371,7 +371,15 @@ func Server(ctx context.Context, conn net.Conn, config *Config) (*Conn, error) {
 				break
 			}
 			for {
-				if val, ok := GlobalPostHandshakeRecordsLens.Load(config.Dest + " " + hs.clientHello.serverName); ok {
+				key := config.Dest + " " + hs.clientHello.serverName
+				if len(hs.clientHello.alpnProtocols) == 0 {
+					key += " 0"
+				} else if hs.clientHello.alpnProtocols[0] == "h2" {
+					key += " 2"
+				} else {
+					key += " 1"
+				}
+				if val, ok := GlobalPostHandshakeRecordsLens.Load(key); ok {
 					if postHandshakeRecordsLens, ok := val.([]int); ok {
 						for _, length := range postHandshakeRecordsLens {
 							plainText := make([]byte, length-16)