Remove client metadata from AnyTLS requests by default

protocol/anytls/client_metadata.go

@@ -0,0 +1,64 @@
+package anytls
+
+import (
+	"encoding/binary"
+	"net"
+	"reflect"
+	"strings"
+	"sync"
+	"unsafe"
+
+	"github.com/sagernet/sing/common"
+
+	anytls "github.com/anytls/sing-anytls"
+	"github.com/anytls/sing-anytls/session"
+)
+
+const (
+	commandSettings = 4
+	frameHeaderSize = 7
+)
+
+var (
+	clientSessionField, _   = reflect.TypeFor[anytls.Client]().FieldByName("sessionClient")
+	streamSessionField, _   = reflect.TypeFor[session.Stream]().FieldByName("sess")
+	sessionConnLockField, _ = reflect.TypeFor[session.Session]().FieldByName("connLock")
+	sessionBufferField, _   = reflect.TypeFor[session.Session]().FieldByName("buffer")
+)
+
+func sessionClientOf(client *anytls.Client) *session.Client {
+	return *(**session.Client)(unsafe.Add(unsafe.Pointer(client), clientSessionField.Offset))
+}
+
+func (h *Outbound) rewriteClientMetadata(conn net.Conn) {
+	sess := *(**session.Session)(unsafe.Add(unsafe.Pointer(conn.(*session.Stream)), streamSessionField.Offset))
+	connLock := (*sync.Mutex)(unsafe.Add(unsafe.Pointer(sess), sessionConnLockField.Offset))
+	bufferPointer := (*[]byte)(unsafe.Add(unsafe.Pointer(sess), sessionBufferField.Offset))
+	connLock.Lock()
+	defer connLock.Unlock()
+	buffer := *bufferPointer
+	offset := 0
+	for offset+frameHeaderSize <= len(buffer) {
+		dataLength := int(binary.BigEndian.Uint16(buffer[offset+5 : offset+7]))
+		frameEnd := offset + frameHeaderSize + dataLength
+		if frameEnd > len(buffer) {
+			return
+		}
+		if buffer[offset] == commandSettings {
+			data := []byte(strings.Join(common.Map(strings.Split(string(buffer[offset+frameHeaderSize:frameEnd]), "\n"), func(line string) string {
+				if strings.HasPrefix(line, "client=") {
+					return "client=" + h.clientMetadata
+				}
+				return line
+			}), "\n"))
+			newBuffer := make([]byte, 0, offset+frameHeaderSize+len(data)+len(buffer)-frameEnd)
+			newBuffer = append(newBuffer, buffer[:offset+5]...)
+			newBuffer = binary.BigEndian.AppendUint16(newBuffer, uint16(len(data)))
+			newBuffer = append(newBuffer, data...)
+			newBuffer = append(newBuffer, buffer[frameEnd:]...)
+			*bufferPointer = newBuffer
+			return
+		}
+		offset = frameEnd
+	}
+}