From 6add1868672ac5b438d14035581428eb75675284 Mon Sep 17 00:00:00 2001
From: Michael Eischer <michael.eischer@fau.de>
Date: Sun, 20 Sep 2020 00:37:58 +0200
Subject: [PATCH] key: Check that a new key file actually works

---
 cmd/restic/cmd_key.go | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/cmd/restic/cmd_key.go b/cmd/restic/cmd_key.go
index bbd4f0f90..69c2542b7 100644
--- a/cmd/restic/cmd_key.go
+++ b/cmd/restic/cmd_key.go
@@ -131,6 +131,11 @@ func addKey(gopts GlobalOptions, repo *repository.Repository) error {
 		return errors.Fatalf("creating new key failed: %v\n", err)
 	}
 
+	err = switchToNewKeyAndRemoveIfBroken(gopts.ctx, repo, id, pw)
+	if err != nil {
+		return err
+	}
+
 	Verbosef("saved new key as %s\n", id)
 
 	return nil
@@ -161,8 +166,14 @@ func changePassword(gopts GlobalOptions, repo *repository.Repository) error {
 	if err != nil {
 		return errors.Fatalf("creating new key failed: %v\n", err)
 	}
+	oldID := repo.KeyName()
 
-	h := restic.Handle{Type: restic.KeyFile, Name: repo.KeyName()}
+	err = switchToNewKeyAndRemoveIfBroken(gopts.ctx, repo, id, pw)
+	if err != nil {
+		return err
+	}
+
+	h := restic.Handle{Type: restic.KeyFile, Name: oldID}
 	err = repo.Backend().Remove(gopts.ctx, h)
 	if err != nil {
 		return err
@@ -173,6 +184,19 @@ func changePassword(gopts GlobalOptions, repo *repository.Repository) error {
 	return nil
 }
 
+func switchToNewKeyAndRemoveIfBroken(ctx context.Context, repo *repository.Repository, key *repository.Key, pw string) error {
+	// Verify new key to make sure it really works. A broken key can render the
+	// whole repository inaccessible
+	err := repo.SearchKey(ctx, pw, 0, key.Name())
+	if err != nil {
+		// the key is invalid, try to remove it
+		h := restic.Handle{Type: restic.KeyFile, Name: key.Name()}
+		_ = repo.Backend().Remove(ctx, h)
+		return errors.Fatalf("failed to access repository with new key: %v", err)
+	}
+	return nil
+}
+
 func runKey(gopts GlobalOptions, args []string) error {
 	if len(args) < 1 || (args[0] == "remove" && len(args) != 2) || (args[0] != "remove" && len(args) != 1) {
 		return errors.Fatal("wrong number of arguments")