daemon/tls: properly process TLS rehandshake

daemon/io.c

@@ -309,7 +309,7 @@ static void _tcp_accept(uv_stream_t *master, int status, bool tls)
 	uint64_t timeout = KR_CONN_RTT_MAX / 2;
 	session->has_tls = tls;
 	if (tls) {
-		timeout += KR_CONN_RTT_MAX * 3;
+		timeout += TLS_MAX_HANDSHAKE_TIME;
 		if (!session->tls_ctx) {
 			session->tls_ctx = tls_new(master->loop->data);
 			if (!session->tls_ctx) {

daemon/tls.c

@@ -307,11 +307,22 @@ int tls_process(struct worker_ctx *worker, uv_stream_t *handle, const uint8_t *b
 	}
 
 	int submitted = 0;
+	bool is_retrying = false;
+	uint64_t retrying_start = 0;
 	while (true) {
 		ssize_t count = gnutls_record_recv(tls_p->tls_session, tls_p->recv_buf, sizeof(tls_p->recv_buf));
 		if (count == GNUTLS_E_AGAIN) {
 			break;    /* No data available */
-		} else if (count == GNUTLS_E_INTERRUPTED) {
+		} else if (count == GNUTLS_E_INTERRUPTED ||
+			   count == GNUTLS_E_REHANDSHAKE) {
+			if (!is_retrying) {
+				is_retrying = true;
+				retrying_start = kr_now();
+			}
+			uint64_t elapsed = kr_now() - retrying_start;
+			if (elapsed > TLS_MAX_HANDSHAKE_TIME) {
+				return kr_error(EIO);
+			}
 			continue; /* Try reading again */
 		} else if (count < 0) {
 			kr_log_verbose("[%s] gnutls_record_recv failed: %s (%zd)\n",

daemon/tls.h

@@ -26,6 +26,22 @@
 #define MAX_TLS_PADDING KR_EDNS_PAYLOAD
 #define TLS_MAX_UNCORK_RETRIES 100
 
+/* rfc 5476, 7.3 - handshake Protocol overview
+ * https://tools.ietf.org/html/rfc5246#page-33
+ * Message flow for a full handshake (only mandatory messages)
+ * ClientHello           -------->
+                                        ServerHello
+                         <--------      ServerHelloDone
+   ClientKeyExchange
+   Finished              -------->
+                         <--------      Finished
+ *
+ * See also https://blog.cloudflare.com/keyless-ssl-the-nitty-gritty-technical-details/
+ * So it takes 2 RTT.
+ * As we use session tickets, there are additional messages, add one RTT mode.
+ */
+ #define TLS_MAX_HANDSHAKE_TIME (KR_CONN_RTT_MAX * 3)
+
 struct tls_ctx_t;
 struct tls_client_ctx_t;
 struct tls_credentials {