Allow oversized objects in rare cases

shared/network-data-retrieval/src/object_fetcher.rs

@@ -335,8 +335,8 @@ impl ObjectFetcher {
             }
         };
 
+        // Return an error if the length is unreasonably large, before we get the next segment
         if Self::decode_data_length(&mut data.as_slice(), &mapping)?.is_some() {
-            // We have enough data to decode the length, and the length is reasonable
             if let Ok(data) = Vec::<u8>::decode(&mut data.as_slice()) {
                 // We have the full object
                 return Ok(data);
@@ -351,10 +351,10 @@ impl ObjectFetcher {
             if let SegmentItem::BlockContinuation { bytes, .. } = segment_item {
                 data.extend_from_slice(&bytes);
 
-                if Self::decode_data_length(&mut data.as_slice(), &mapping)?.is_some() {
-                    if let Ok(data) = Vec::<u8>::decode(&mut data.as_slice()) {
-                        return Ok(data);
-                    }
+                // We already downloaded the data, and there are no more segments to download, so
+                // we don't check the length again. In rare cases this can allow oversized objects
+                if let Ok(data) = Vec::<u8>::decode(&mut data.as_slice()) {
+                    return Ok(data);
                 }
             }
         }