[tls] Refuse to attempt renegotiation for TLS version 1.3

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/net/tls.c

diff --git a/src/net/tls.c b/src/net/tls.c
index c2cb2cb..a7815ba 100644
--- a/src/net/tls.c
+++ b/src/net/tls.c
@@ -2710,7 +2710,9 @@
 	}
 
 	/* Fail unless server supports secure renegotiation */
-	if ( ! ( tls->secure_renegotiation && tls->extended_master_secret ) ) {
+	if ( tls_version ( tls, TLS_VERSION_TLS_1_3 ) ||
+	     ( ! tls->secure_renegotiation ) ||
+	     ( ! tls->extended_master_secret ) ) {
 		DBGC ( tls, "TLS %p refusing to renegotiate insecurely\n",
 		       tls );
 		return -EPERM_RENEG_INSECURE;