netxlite: utls for TLS parroting

This is the ground work for https://github.com/ooni/probe/issues/1424.

internal/netxlite/tlshandshaker.go

@@ -5,6 +5,8 @@ import (
 	"crypto/tls"
 	"net"
 	"time"
+
+	utls "gitlab.com/yawning/utls.git"
 )
 
 // TLSHandshaker is the generic TLS handshaker.
@@ -105,4 +107,41 @@ func (h *TLSHandshakerLogger) Handshake(
 	return tlsconn, state, nil
 }
 
+// UTLSConn implements TLSConn and uses a utls UConn as its underlying connection
+type UTLSConn struct {
+	*utls.UConn
+}
+
+// NewConnUTLS creates a NewConn function creating a utls connection with a specified ClientHelloID
+func NewConnUTLS(clientHello *utls.ClientHelloID) func(conn net.Conn, config *tls.Config) TLSConn {
+	return func(conn net.Conn, config *tls.Config) TLSConn {
+		uConfig := &utls.Config{
+			RootCAs:                     config.RootCAs,
+			NextProtos:                  config.NextProtos,
+			ServerName:                  config.ServerName,
+			InsecureSkipVerify:          config.InsecureSkipVerify,
+			DynamicRecordSizingDisabled: config.DynamicRecordSizingDisabled,
+		}
+		tlsConn := utls.UClient(conn, uConfig, *clientHello)
+		return &UTLSConn{tlsConn}
+	}
+}
+
+func (c *UTLSConn) ConnectionState() tls.ConnectionState {
+	uState := c.Conn.ConnectionState()
+	return tls.ConnectionState{
+		Version:                     uState.Version,
+		HandshakeComplete:           uState.HandshakeComplete,
+		DidResume:                   uState.DidResume,
+		CipherSuite:                 uState.CipherSuite,
+		NegotiatedProtocol:          uState.NegotiatedProtocol,
+		ServerName:                  uState.ServerName,
+		PeerCertificates:            uState.PeerCertificates,
+		VerifiedChains:              uState.VerifiedChains,
+		SignedCertificateTimestamps: uState.SignedCertificateTimestamps,
+		OCSPResponse:                uState.OCSPResponse,
+		TLSUnique:                   uState.TLSUnique,
+	}
+}
+
 var _ TLSHandshaker = &TLSHandshakerLogger{}