add tunnel feature for relay

internal/util/forward/forward.go

@@ -0,0 +1,98 @@
+package forward
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"crypto/tls"
+	"encoding/binary"
+	"io"
+	"net/http"
+	"strings"
+
+	dissector "github.com/go-gost/tls-dissector"
+	xio "github.com/go-gost/x/internal/io"
+)
+
+func Sniffing(ctx context.Context, rdw io.ReadWriter) (rw io.ReadWriter, host string, protocol string, err error) {
+	rw = rdw
+
+	// try to sniff TLS traffic
+	var hdr [dissector.RecordHeaderLen]byte
+	_, err = io.ReadFull(rw, hdr[:])
+	rw = xio.NewReadWriter(io.MultiReader(bytes.NewReader(hdr[:]), rw), rw)
+	if err == nil &&
+		hdr[0] == dissector.Handshake &&
+		binary.BigEndian.Uint16(hdr[1:3]) == tls.VersionTLS10 {
+		rw, host, err = sniffSNI(ctx, rw)
+		return
+	}
+
+	// try to sniff HTTP traffic
+	if isHTTP(string(hdr[:])) {
+		buf := new(bytes.Buffer)
+		var r *http.Request
+		r, err = http.ReadRequest(bufio.NewReader(io.TeeReader(rw, buf)))
+		rw = xio.NewReadWriter(io.MultiReader(buf, rw), rw)
+		if err == nil {
+			host = r.Host
+			return
+		}
+	}
+
+	protocol = sniffProtocol(hdr[:])
+
+	return
+}
+
+func sniffSNI(ctx context.Context, rw io.ReadWriter) (io.ReadWriter, string, error) {
+	buf := new(bytes.Buffer)
+	host, err := getServerName(ctx, io.TeeReader(rw, buf))
+	rw = xio.NewReadWriter(io.MultiReader(buf, rw), rw)
+	return rw, host, err
+}
+
+func getServerName(ctx context.Context, r io.Reader) (host string, err error) {
+	record, err := dissector.ReadRecord(r)
+	if err != nil {
+		return
+	}
+
+	clientHello := dissector.ClientHelloMsg{}
+	if err = clientHello.Decode(record.Opaque); err != nil {
+		return
+	}
+
+	for _, ext := range clientHello.Extensions {
+		if ext.Type() == dissector.ExtServerName {
+			snExtension := ext.(*dissector.ServerNameExtension)
+			host = snExtension.Name
+			break
+		}
+	}
+
+	return
+}
+
+func isHTTP(s string) bool {
+	return strings.HasPrefix(http.MethodGet, s[:3]) ||
+		strings.HasPrefix(http.MethodPost, s[:4]) ||
+		strings.HasPrefix(http.MethodPut, s[:3]) ||
+		strings.HasPrefix(http.MethodDelete, s) ||
+		strings.HasPrefix(http.MethodOptions, s) ||
+		strings.HasPrefix(http.MethodPatch, s) ||
+		strings.HasPrefix(http.MethodHead, s[:4]) ||
+		strings.HasPrefix(http.MethodConnect, s) ||
+		strings.HasPrefix(http.MethodTrace, s)
+}
+
+const (
+	SSHv2 = "SSH-2"
+)
+
+func sniffProtocol(hdr []byte) string {
+	if string(hdr) == SSHv2 {
+		return "ssh"
+	}
+	return ""
+}