Support tls-exporter channel binding type

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## jackal - main / unreleased
 
+* [ENHANCEMENT] Re-enable TLS 1.3 channel binding during auth using [RFC 9266](https://www.rfc-editor.org/rfc/rfc9266).
+
 ## 0.61.0 (2022/06/06)
 
 * [ENHANCEMENT] Helm: added support for cloud LB. [237](https://github.com/ortuman/jackal/pull/237) 

pkg/auth/scram.go

@@ -357,6 +357,8 @@ func (s *Scram) getCBindInputString() string {
 		switch s.params.cbMechanism {
 		case "tls-unique":
 			buf.Write(s.tr.ChannelBindingBytes(transport.TLSUnique))
+		case "tls-exporter":
+			buf.Write(s.tr.ChannelBindingBytes(transport.TLSExporter))
 		}
 	}
 	return base64.StdEncoding.EncodeToString(buf.Bytes())

pkg/c2s/in.go

@@ -765,7 +765,7 @@ func (s *inC2S) unauthenticatedFeatures() []stravaganza.Element {
 		sb.WithAttribute(stravaganza.Namespace, saslNamespace)
 		for _, authenticator := range s.authSt.authenticators {
 			if authenticator.UsesChannelBinding() && !supportsCb {
-				continue // transport doesn't support channel binding (eg. TLS 1.3)
+				continue // transport doesn't support channel binding
 			}
 			sb.WithChild(
 				stravaganza.NewBuilder("mechanism").

pkg/transport/socket.go

@@ -47,7 +47,6 @@ type socketTransport struct {
 	wr               io.Writer
 	bw               *bufio.Writer
 	compressed       bool
-	supportsCb       bool
 	connectTimeout   time.Duration
 	keepAliveTimeout time.Duration
 }
@@ -147,7 +146,6 @@ func (s *socketTransport) StartTLS(cfg *tls.Config, asClient bool) {
 		tlsConn = tls.Server(s.conn, cfg)
 	}
 	s.conn = newDeadlineConn(tlsConn, s.connectTimeout, s.keepAliveTimeout)
-	s.supportsCb = tlsConn.ConnectionState().Version < tls.VersionTLS13
 
 	lr := ratelimiter.NewReader(s.conn)
 	if rLim := s.lr.ReadRateLimiter(); rLim != nil {
@@ -169,13 +167,10 @@ func (s *socketTransport) EnableCompression(level compress.Level) {
 }
 
 func (s *socketTransport) SupportsChannelBinding() bool {
-	return s.supportsCb
+	return true
 }
 
 func (s *socketTransport) ChannelBindingBytes(mechanism ChannelBindingMechanism) []byte {
-	if !s.supportsCb {
-		return nil
-	}
 	conn, ok := s.conn.underlyingConn().(tlsStateQueryable)
 	if !ok {
 		return nil
@@ -184,6 +179,13 @@ func (s *socketTransport) ChannelBindingBytes(mechanism ChannelBindingMechanism)
 	case TLSUnique:
 		connSt := conn.ConnectionState()
 		return connSt.TLSUnique
+	case TLSExporter:
+		connSt := conn.ConnectionState()
+		ekm, err := connSt.ExportKeyingMaterial("EXPORTER-Channel-Binding", nil, 32)
+		if err != nil {
+			return nil
+		}
+		return ekm
 	default:
 		break
 	}

pkg/transport/socket_test.go

@@ -87,6 +87,7 @@ func TestSocket(t *testing.T) {
 
 	require.Nil(t, st2.ChannelBindingBytes(ChannelBindingMechanism(99)))
 	require.Nil(t, st2.ChannelBindingBytes(TLSUnique))
+	require.Nil(t, st2.ChannelBindingBytes(TLSExporter))
 
 	_ = st.Close()
 	require.True(t, conn.closed)

pkg/transport/transport.go

@@ -47,6 +47,8 @@ type ChannelBindingMechanism int
 const (
 	// TLSUnique represents 'tls-unique' channel binding mechanism.
 	TLSUnique ChannelBindingMechanism = iota
+	// TLSExporter represents the 'tls-exporter' channel binding mechanism.
+	TLSExporter
 )
 
 // Transport represents a stream transport mechanism.