v1.0.0

common/protocol/tls/sniff.go

@@ -0,0 +1,146 @@
+package tls
+
+import (
+	"encoding/binary"
+	"errors"
+	"strings"
+
+	"github.com/xtls/xray-core/v1/common"
+)
+
+type SniffHeader struct {
+	domain string
+}
+
+func (h *SniffHeader) Protocol() string {
+	return "tls"
+}
+
+func (h *SniffHeader) Domain() string {
+	return h.domain
+}
+
+var errNotTLS = errors.New("not TLS header")
+var errNotClientHello = errors.New("not client hello")
+
+func IsValidTLSVersion(major, minor byte) bool {
+	return major == 3
+}
+
+// ReadClientHello returns server name (if any) from TLS client hello message.
+// https://github.com/golang/go/blob/master/src/crypto/tls/handshake_messages.go#L300
+func ReadClientHello(data []byte, h *SniffHeader) error {
+	if len(data) < 42 {
+		return common.ErrNoClue
+	}
+	sessionIDLen := int(data[38])
+	if sessionIDLen > 32 || len(data) < 39+sessionIDLen {
+		return common.ErrNoClue
+	}
+	data = data[39+sessionIDLen:]
+	if len(data) < 2 {
+		return common.ErrNoClue
+	}
+	// cipherSuiteLen is the number of bytes of cipher suite numbers. Since
+	// they are uint16s, the number must be even.
+	cipherSuiteLen := int(data[0])<<8 | int(data[1])
+	if cipherSuiteLen%2 == 1 || len(data) < 2+cipherSuiteLen {
+		return errNotClientHello
+	}
+	data = data[2+cipherSuiteLen:]
+	if len(data) < 1 {
+		return common.ErrNoClue
+	}
+	compressionMethodsLen := int(data[0])
+	if len(data) < 1+compressionMethodsLen {
+		return common.ErrNoClue
+	}
+	data = data[1+compressionMethodsLen:]
+
+	if len(data) == 0 {
+		return errNotClientHello
+	}
+	if len(data) < 2 {
+		return errNotClientHello
+	}
+
+	extensionsLength := int(data[0])<<8 | int(data[1])
+	data = data[2:]
+	if extensionsLength != len(data) {
+		return errNotClientHello
+	}
+
+	for len(data) != 0 {
+		if len(data) < 4 {
+			return errNotClientHello
+		}
+		extension := uint16(data[0])<<8 | uint16(data[1])
+		length := int(data[2])<<8 | int(data[3])
+		data = data[4:]
+		if len(data) < length {
+			return errNotClientHello
+		}
+
+		if extension == 0x00 { /* extensionServerName */
+			d := data[:length]
+			if len(d) < 2 {
+				return errNotClientHello
+			}
+			namesLen := int(d[0])<<8 | int(d[1])
+			d = d[2:]
+			if len(d) != namesLen {
+				return errNotClientHello
+			}
+			for len(d) > 0 {
+				if len(d) < 3 {
+					return errNotClientHello
+				}
+				nameType := d[0]
+				nameLen := int(d[1])<<8 | int(d[2])
+				d = d[3:]
+				if len(d) < nameLen {
+					return errNotClientHello
+				}
+				if nameType == 0 {
+					serverName := string(d[:nameLen])
+					// An SNI value may not include a
+					// trailing dot. See
+					// https://tools.ietf.org/html/rfc6066#section-3.
+					if strings.HasSuffix(serverName, ".") {
+						return errNotClientHello
+					}
+					h.domain = serverName
+					return nil
+				}
+				d = d[nameLen:]
+			}
+		}
+		data = data[length:]
+	}
+
+	return errNotTLS
+}
+
+func SniffTLS(b []byte) (*SniffHeader, error) {
+	if len(b) < 5 {
+		return nil, common.ErrNoClue
+	}
+
+	if b[0] != 0x16 /* TLS Handshake */ {
+		return nil, errNotTLS
+	}
+	if !IsValidTLSVersion(b[1], b[2]) {
+		return nil, errNotTLS
+	}
+	headerLen := int(binary.BigEndian.Uint16(b[3:5]))
+	if 5+headerLen > len(b) {
+		return nil, common.ErrNoClue
+	}
+
+	h := &SniffHeader{}
+	err := ReadClientHello(b[5:5+headerLen], h)
+	if err == nil {
+		return h, nil
+	}
+	return nil, err
+}