out_splunk: Fix crashes when passed non-array input data (#2457)

At present, non-array inputs cause a segfault when trying to read
key-value pairs out of an assumed-to-be-there map.

Other output plugins already make a check of this form, including es,
gelf, influxdb, kube_meta, td, and syslog -- but splunk currently does
not. This patch simply adds one.

Signed-off-by: Aaron Jacobs <[email protected]>

Author: atheriel

plugins/out_splunk/splunk.c

@@ -74,7 +74,14 @@ static int splunk_format(const void *in_buf, size_t in_bytes,
     msgpack_unpacked_init(&result);
 
     while (msgpack_unpack_next(&result, in_buf, in_bytes, &off) == MSGPACK_UNPACK_SUCCESS) {
+        if (result.data.type != MSGPACK_OBJECT_ARRAY) {
+            continue;
+        }
+
         root = result.data;
+        if (root.via.array.size != 2) {
+            continue;
+        }
 
         /* Get timestamp */
         flb_time_pop_from_msgpack(&tm, &result, &obj);