support pluggable backstores for storing assertions

asserts/fsentryutils.go

@@ -0,0 +1,49 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2015 Canonical Ltd
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+package asserts
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+
+	"github.com/ubuntu-core/snappy/helpers"
+)
+
+// utilities to read/write fs entries
+
+func atomicWriteEntry(data []byte, secret bool, top string, subpath ...string) error {
+	fpath := filepath.Join(top, filepath.Join(subpath...))
+	dir := filepath.Dir(fpath)
+	err := os.MkdirAll(dir, 0775)
+	if err != nil {
+		return err
+	}
+	fperm := 0664
+	if secret {
+		fperm = 0600
+	}
+	return helpers.AtomicWriteFile(fpath, data, os.FileMode(fperm), 0)
+}
+
+func readEntry(top string, subpath ...string) ([]byte, error) {
+	fpath := filepath.Join(top, filepath.Join(subpath...))
+	return ioutil.ReadFile(fpath)
+}