Merge pull request #250 from mozilla/oss-fuzz-5139142796902400

Add check for required explicit extent offset and length in iloc

Author: baumanj

mp4parse/src/lib.rs

@@ -853,7 +853,7 @@ struct SingleItemTypeReferenceBox {
 
 /// Potential sizes (in bytes) of variable-sized fields of the 'iloc' box
 /// See ISOBMFF (ISO 14496-12:2015) § 8.11.3
-#[derive(Debug)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 enum IlocFieldSize {
     Zero,
     Four,
@@ -1973,6 +1973,16 @@ fn read_iloc<T: Read>(src: &mut BMFFBox<T>) -> Result<TryVec<ItemLocationBoxItem
             ));
         }
 
+        // "If only one extent is used (extent_count = 1) then either or both of the
+        //  offset and length may be implied"
+        if extent_count != 1
+            && (offset_size == IlocFieldSize::Zero || length_size == IlocFieldSize::Zero)
+        {
+            return Err(Error::InvalidData(
+                "extent_count != 1 requires explicit offset and length per ISOBMFF (ISO 14496-12:2015) § 8.11.3.3",
+            ));
+        }
+
         let mut extents = TryVec::with_capacity(extent_count.to_usize())?;
 
         for _ in 0..extent_count {