Merge pull request restic#4853 from MichaelEischer/safer-repo-init

init: double check that no repository exists yet

internal/repository/repository.go

@@ -772,6 +772,14 @@ func (r *Repository) Init(ctx context.Context, version uint, password string, ch
 	if err == nil {
 		return errors.New("repository master key and config already initialized")
 	}
+	// double check to make sure that a repository is not accidentally reinitialized
+	// if the backend somehow fails to stat the config file. An initialized repository
+	// must always contain at least one key file.
+	if err := r.List(ctx, restic.KeyFile, func(_ restic.ID, _ int64) error {
+		return errors.New("repository already contains keys")
+	}); err != nil {
+		return err
+	}
 
 	cfg, err := restic.CreateConfig(version)
 	if err != nil {

internal/repository/repository_test.go

@@ -9,6 +9,7 @@ import (
 	"math/rand"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -457,3 +458,19 @@ func TestListPack(t *testing.T) {
 
 	rtest.Assert(t, !c.Has(backend.Handle{Type: restic.PackFile, Name: packID.String()}), "tree pack should no longer be cached as ListPack does not set IsMetadata in the backend.Handle")
 }
+
+func TestNoDoubleInit(t *testing.T) {
+	r, be := repository.TestRepositoryWithVersion(t, restic.StableRepoVersion)
+
+	repo, err := repository.New(be, repository.Options{})
+	rtest.OK(t, err)
+
+	pol := r.Config().ChunkerPolynomial
+	err = repo.Init(context.TODO(), r.Config().Version, test.TestPassword, &pol)
+	rtest.Assert(t, strings.Contains(err.Error(), "repository master key and config already initialized"), "expected config exist error, got %q", err)
+
+	// must also prevent init if only keys exist
+	rtest.OK(t, be.Remove(context.TODO(), backend.Handle{Type: backend.ConfigFile}))
+	err = repo.Init(context.TODO(), r.Config().Version, test.TestPassword, &pol)
+	rtest.Assert(t, strings.Contains(err.Error(), "repository already contains keys"), "expected already contains keys error, got %q", err)
+}