dashdemux: improve validation of UTCtiming element

gst_mpdparser_parse_utctiming_node does not validate the parsed values completely. The following scenarios are incorrectly accepted:
- elements with no schemeIdUri property should be rejected
- elements with unrecognized UTCTiming scheme should be rejected
- elements with empty values should be rejected

The last one triggers a division by 0 in gst_dash_demux_poll_clock_drift:
clock_drift->selected_url = clock_drift->selected_url % g_strv_length (urls);
because it urls is a valid pointer to an empty array.

https://bugzilla.gnome.org/show_bug.cgi?id=759547

1 files changed, 5 insertions, 0 deletions

diff --git a/ext/dash/gstmpdparser.c b/ext/dash/gstmpdparser.c
index ca52ebf6c..851099996 100644
--- a/ext/dash/gstmpdparser.c
+++ b/ext/dash/gstmpdparser.c
@@ -2207,6 +2207,11 @@ gst_mpdparser_parse_utctiming_node (GList ** list, xmlNode * a_node)
     }
     new_timing->urls = g_strsplit (value, " ", max_tokens);
     xmlFree (value);
+  }
+
+  /* append to list only if both method and urls were set */
+  if (new_timing->method != 0 && new_timing->urls != NULL &&
+      g_strv_length (new_timing->urls) != 0) {
     *list = g_list_append (*list, new_timing);
   } else {
     gst_mpdparser_free_utctiming_node (new_timing);