diff --git a/images/archive/importer.go b/images/archive/importer.go index 8afdd68f2..c53104950 100644 --- a/images/archive/importer.go +++ b/images/archive/importer.go @@ -269,9 +269,13 @@ func resolveLayers(ctx context.Context, store content.Store, layerFiles []string if ok { desc := descs[digest.Digest(dgst)] if desc != nil { - desc.MediaType = images.MediaTypeDockerSchema2LayerGzip desc.Digest = info.Digest desc.Size = info.Size + mediaType, err := detectLayerMediaType(ctx, store, *desc) + if err != nil { + return fmt.Errorf("failed to detect media type of layer: %w", err) + } + desc.MediaType = mediaType } } return nil @@ -381,3 +385,29 @@ func writeManifest(ctx context.Context, cs content.Ingester, manifest interface{ return desc, nil } + +func detectLayerMediaType(ctx context.Context, store content.Store, desc ocispec.Descriptor) (string, error) { + var mediaType string + // need to parse existing blob to use the proper media type + bytes := make([]byte, 10) + ra, err := store.ReaderAt(ctx, desc) + if err != nil { + return "", fmt.Errorf("failed to read content store to detect layer media type: %w", err) + } + defer ra.Close() + _, err = ra.ReadAt(bytes, 0) + if err != nil && err != io.EOF { + return "", fmt.Errorf("failed to read header bytes from layer to detect media type: %w", err) + } + if err == io.EOF { + // in the case of an empty layer then the media type should be uncompressed + return images.MediaTypeDockerSchema2Layer, nil + } + switch c := compression.DetectCompression(bytes); c { + case compression.Uncompressed: + mediaType = images.MediaTypeDockerSchema2Layer + default: + mediaType = images.MediaTypeDockerSchema2LayerGzip + } + return mediaType, nil +}