admin: Export logos present in challenge.json

admin/sync/file.go

@@ -238,3 +238,21 @@ func WriteFileContent(i Importer, URI string, content []byte) error {
 		return fmt.Errorf("%t is not capable of writing", i)
 	}
 }
+
+func OpenOrGetFile(i Importer, URI string) (fd io.Reader, closer func() error, err error) {
+	if strings.HasPrefix(URI, "$FILES$") {
+		var fdc io.ReadCloser
+		fdc, err = os.Open(path.Join(fic.FilesDir, strings.TrimPrefix(URI, "$FILES$/")))
+		fd = fdc
+		closer = fdc.Close
+	} else {
+		fd, err = GlobalImporter.GetFile(URI)
+		if fdcloser, ok := fd.(io.ReadCloser); ok {
+			closer = fdcloser.Close
+		} else {
+			closer = func() error { return nil }
+		}
+	}
+
+	return
+}