feat: verify by checksum and remove if invalid

pkg/sum/sum.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2020 Proton Technologies AG
+//
+// This file is part of ProtonMail Bridge.
+//
+// ProtonMail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// ProtonMail Bridge 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 ProtonMail Bridge.  If not, see <https://www.gnu.org/licenses/>.
+
+package sum
+
+import (
+	"crypto/sha512"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// RecursiveSum computes the sha512 sum of all files in the root directory and descendents.
+// If a skipFile is provided (e.g. the path of a checksum file relative to rootDir), it (and its signature) is ignored.
+func RecursiveSum(rootDir, skipFile string) ([]byte, error) {
+	hash := sha512.New()
+
+	if err := filepath.Walk(rootDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if info.IsDir() {
+			return nil
+		}
+
+		// The hashfile itself isn't included in the hash.
+		if path == filepath.Join(rootDir, skipFile) || path == filepath.Join(rootDir, skipFile+".sig") {
+			return nil
+		}
+
+		if _, err := hash.Write([]byte(strings.TrimPrefix(path, rootDir))); err != nil {
+			return err
+		}
+
+		f, err := os.Open(path) // nolint[gosec]
+		if err != nil {
+			return err
+		}
+
+		if _, err := io.Copy(hash, f); err != nil {
+			return err
+		}
+
+		return nil
+	}); err != nil {
+		return nil, err
+	}
+
+	return hash.Sum([]byte{}), nil
+}