Refactor handling of runtime configuration to prepare for reloading

cmd/backup/encrypt_archive.go

@@ -0,0 +1,63 @@
+// Copyright 2024 - Offen Authors <hioffen@posteo.de>
+// SPDX-License-Identifier: MPL-2.0
+
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"path"
+
+	openpgp "github.com/ProtonMail/go-crypto/openpgp/v2"
+)
+
+// encryptArchive encrypts the backup file using PGP and the configured passphrase.
+// In case no passphrase is given it returns early, leaving the backup file
+// untouched.
+func (s *script) encryptArchive() error {
+	if s.c.GpgPassphrase == "" {
+		return nil
+	}
+
+	gpgFile := fmt.Sprintf("%s.gpg", s.file)
+	s.registerHook(hookLevelPlumbing, func(error) error {
+		if err := remove(gpgFile); err != nil {
+			return fmt.Errorf("encryptArchive: error removing gpg file: %w", err)
+		}
+		s.logger.Info(
+			fmt.Sprintf("Removed GPG file `%s`.", gpgFile),
+		)
+		return nil
+	})
+
+	outFile, err := os.Create(gpgFile)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error opening out file: %w", err)
+	}
+	defer outFile.Close()
+
+	_, name := path.Split(s.file)
+	dst, err := openpgp.SymmetricallyEncrypt(outFile, []byte(s.c.GpgPassphrase), &openpgp.FileHints{
+		FileName: name,
+	}, nil)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error encrypting backup file: %w", err)
+	}
+	defer dst.Close()
+
+	src, err := os.Open(s.file)
+	if err != nil {
+		return fmt.Errorf("encryptArchive: error opening backup file `%s`: %w", s.file, err)
+	}
+
+	if _, err := io.Copy(dst, src); err != nil {
+		return fmt.Errorf("encryptArchive: error writing ciphertext to file: %w", err)
+	}
+
+	s.file = gpgFile
+	s.logger.Info(
+		fmt.Sprintf("Encrypted backup using given passphrase, saving as `%s`.", s.file),
+	)
+	return nil
+}