generate_session_ticket: tickets cannot extend the original session time

That is, on a resumed session the server would not issue new tickets
that would have extended the lifetime of the originally issued ticket.

Resolves #476

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>

1 files changed, 22 insertions, 5 deletions

diff --git a/lib/tls13/session_ticket.c b/lib/tls13/session_ticket.c
index ca11fd78a6..77edbcda91 100644
--- a/lib/tls13/session_ticket.c
+++ b/lib/tls13/session_ticket.c
@@ -177,6 +177,20 @@ generate_session_ticket(gnutls_session_t session, tls13_ticket_t *ticket)
 	int ret;
 	gnutls_datum_t packed = { NULL, 0 };
 	tls13_ticket_t ticket_data;
+	time_t now = gnutls_time(0);
+
+	if (session->internals.resumed != RESUME_FALSE) {
+		/* If we are resuming ensure that we don't extend the lifetime
+		 * of the ticket past the original session expiration time */
+		if (now >= session->security_parameters.timestamp + session->internals.expire_time)
+			return GNUTLS_E_INT_RET_0; /* don't send ticket */
+		else
+			ticket->lifetime = session->security_parameters.timestamp +
+					   session->internals.expire_time - now;
+	} else {
+		/* Set ticket lifetime to the default expiration time */
+		ticket->lifetime = session->internals.expire_time;
+	}
 
 	/* Generate a random 32-bit ticket nonce */
 	ticket->nonce_size = 4;
@@ -188,8 +202,6 @@ generate_session_ticket(gnutls_session_t session, tls13_ticket_t *ticket)
 	if ((ret = gnutls_rnd(GNUTLS_RND_NONCE, &ticket->age_add, sizeof(uint32_t))) < 0)
 		return gnutls_assert_val(ret);
 
-	/* Set ticket lifetime to the default expiration time */
-	ticket->lifetime = session->internals.expire_time;
 
 	ticket->prf = session->security_parameters.prf;
 
@@ -239,11 +251,16 @@ int _gnutls13_send_session_ticket(gnutls_session_t session, unsigned again)
 	if (again == 0) {
 		memset(&ticket, 0, sizeof(tls13_ticket_t));
 
-		ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
-		if (ret < 0)
+		ret = generate_session_ticket(session, &ticket);
+		if (ret < 0) {
+			if (ret == GNUTLS_E_INT_RET_0) {
+				return gnutls_assert_val(0);
+			}
+
 			return gnutls_assert_val(ret);
+		}
 
-		ret = generate_session_ticket(session, &ticket);
+		ret = _gnutls_buffer_init_handshake_mbuffer(&buf);
 		if (ret < 0) {
 			gnutls_assert();
 			goto cleanup;