Add --insecure-no-password option

This also includes two derived options `--from-insecure-no-password`
used for commands that require specifying a source repository. And
`--new-insecure-no-password` for the `key add` and `key passwd`
commands.

Specifying `--insecure-no-password` disabled the password prompt and
immediately uses an empty password. Passing a password via CLI option or
environment variable at the same time is an error.

cmd/restic/cmd_backup.go

@@ -257,7 +257,7 @@ func readFilenamesRaw(r io.Reader) (names []string, err error) {
 
 // Check returns an error when an invalid combination of options was set.
 func (opts BackupOptions) Check(gopts GlobalOptions, args []string) error {
-	if gopts.password == "" {
+	if gopts.password == "" && !gopts.InsecureNoPassword {
 		if opts.Stdin {
 			return errors.Fatal("cannot read both password and data from stdin")
 		}

cmd/restic/cmd_backup_integration_test.go

@@ -627,3 +627,17 @@ func TestStdinFromCommandFailNoOutputAndExitCode(t *testing.T) {
 
 	testRunCheck(t, env.gopts)
 }
+
+func TestBackupEmptyPassword(t *testing.T) {
+	// basic sanity test that empty passwords work
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+
+	env.gopts.password = ""
+	env.gopts.InsecureNoPassword = true
+
+	testSetupBackupData(t, env)
+	testRunBackup(t, filepath.Dir(env.testdata), []string{"testdata"}, BackupOptions{}, env.gopts)
+	testListSnapshots(t, env.gopts, 1)
+	testRunCheck(t, env.gopts)
+}

cmd/restic/cmd_copy_integration_test.go

@@ -13,10 +13,12 @@ func testRunCopy(t testing.TB, srcGopts GlobalOptions, dstGopts GlobalOptions) {
 	gopts := srcGopts
 	gopts.Repo = dstGopts.Repo
 	gopts.password = dstGopts.password
+	gopts.InsecureNoPassword = dstGopts.InsecureNoPassword
 	copyOpts := CopyOptions{
 		secondaryRepoOptions: secondaryRepoOptions{
-			Repo:     srcGopts.Repo,
+			Repo:               srcGopts.Repo,
-			password: srcGopts.password,
+			password:           srcGopts.password,
+			InsecureNoPassword: srcGopts.InsecureNoPassword,
 		},
 	}
 
@@ -134,3 +136,22 @@ func TestCopyUnstableJSON(t *testing.T) {
 	testRunCheck(t, env2.gopts)
 	testListSnapshots(t, env2.gopts, 1)
 }
+
+func TestCopyToEmptyPassword(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	env2, cleanup2 := withTestEnvironment(t)
+	defer cleanup2()
+	env2.gopts.password = ""
+	env2.gopts.InsecureNoPassword = true
+
+	testSetupBackupData(t, env)
+	testRunBackup(t, "", []string{filepath.Join(env.testdata, "0", "0", "9")}, BackupOptions{}, env.gopts)
+
+	testRunInit(t, env2.gopts)
+	testRunCopy(t, env.gopts, env2.gopts)
+
+	testListSnapshots(t, env.gopts, 1)
+	testListSnapshots(t, env2.gopts, 1)
+	testRunCheck(t, env2.gopts)
+}

cmd/restic/cmd_key_add.go

@@ -28,12 +28,14 @@ Exit status is 0 if the command is successful, and non-zero if there was any err
 
 type KeyAddOptions struct {
 	NewPasswordFile    string
+	InsecureNoPassword bool
 	Username           string
 	Hostname           string
 }
 
 func (opts *KeyAddOptions) Add(flags *pflag.FlagSet) {
 	flags.StringVarP(&opts.NewPasswordFile, "new-password-file", "", "", "`file` from which to read the new password")
+	flags.BoolVar(&opts.InsecureNoPassword, "new-insecure-no-password", false, "add an empty password for the repository (insecure)")
 	flags.StringVarP(&opts.Username, "user", "", "", "the username for new key")
 	flags.StringVarP(&opts.Hostname, "host", "", "", "the hostname for new key")
 }
@@ -63,7 +65,7 @@ func runKeyAdd(ctx context.Context, gopts GlobalOptions, opts KeyAddOptions, arg
 }
 
 func addKey(ctx context.Context, repo *repository.Repository, gopts GlobalOptions, opts KeyAddOptions) error {
-	pw, err := getNewPassword(ctx, gopts, opts.NewPasswordFile)
+	pw, err := getNewPassword(ctx, gopts, opts.NewPasswordFile, opts.InsecureNoPassword)
 	if err != nil {
 		return err
 	}
@@ -86,19 +88,35 @@ func addKey(ctx context.Context, repo *repository.Repository, gopts GlobalOption
 // testKeyNewPassword is used to set a new password during integration testing.
 var testKeyNewPassword string
 
-func getNewPassword(ctx context.Context, gopts GlobalOptions, newPasswordFile string) (string, error) {
+func getNewPassword(ctx context.Context, gopts GlobalOptions, newPasswordFile string, insecureNoPassword bool) (string, error) {
 	if testKeyNewPassword != "" {
 		return testKeyNewPassword, nil
 	}
 
+	if insecureNoPassword {
+		if newPasswordFile != "" {
+			return "", fmt.Errorf("only either --new-password-file or --new-insecure-no-password may be specified")
+		}
+		return "", nil
+	}
+
 	if newPasswordFile != "" {
-		return loadPasswordFromFile(newPasswordFile)
+		password, err := loadPasswordFromFile(newPasswordFile)
+		if err != nil {
+			return "", err
+		}
+		if password == "" {
+			return "", fmt.Errorf("an empty password is not allowed by default. Pass the flag `--new-insecure-no-password` to restic to disable this check")
+		}
+		return password, nil
 	}
 
 	// Since we already have an open repository, temporary remove the password
 	// to prompt the user for the passwd.
 	newopts := gopts
 	newopts.password = ""
+	// empty passwords are already handled above
+	newopts.InsecureNoPassword = false
 
 	return ReadPasswordTwice(ctx, newopts,
 		"enter new password: ",

cmd/restic/cmd_key_integration_test.go

@@ -3,6 +3,8 @@ package main
 import (
 	"bufio"
 	"context"
+	"os"
+	"path/filepath"
 	"regexp"
 	"strings"
 	"testing"
@@ -109,6 +111,43 @@ func TestKeyAddRemove(t *testing.T) {
 	testRunKeyAddNewKeyUserHost(t, env.gopts)
 }
 
+func TestKeyAddInvalid(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	testRunInit(t, env.gopts)
+
+	err := runKeyAdd(context.TODO(), env.gopts, KeyAddOptions{
+		NewPasswordFile:    "some-file",
+		InsecureNoPassword: true,
+	}, []string{})
+	rtest.Assert(t, strings.Contains(err.Error(), "only either"), "unexpected error message, got %q", err)
+
+	pwfile := filepath.Join(t.TempDir(), "pwfile")
+	rtest.OK(t, os.WriteFile(pwfile, []byte{}, 0o666))
+
+	err = runKeyAdd(context.TODO(), env.gopts, KeyAddOptions{
+		NewPasswordFile: pwfile,
+	}, []string{})
+	rtest.Assert(t, strings.Contains(err.Error(), "an empty password is not allowed by default"), "unexpected error message, got %q", err)
+}
+
+func TestKeyAddEmpty(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	// must list keys more than once
+	env.gopts.backendTestHook = nil
+	defer cleanup()
+	testRunInit(t, env.gopts)
+
+	rtest.OK(t, runKeyAdd(context.TODO(), env.gopts, KeyAddOptions{
+		InsecureNoPassword: true,
+	}, []string{}))
+
+	env.gopts.password = ""
+	env.gopts.InsecureNoPassword = true
+
+	testRunCheck(t, env.gopts)
+}
+
 type emptySaveBackend struct {
 	backend.Backend
 }

cmd/restic/cmd_key_passwd.go

@@ -53,7 +53,7 @@ func runKeyPasswd(ctx context.Context, gopts GlobalOptions, opts KeyPasswdOption
 }
 
 func changePassword(ctx context.Context, repo *repository.Repository, gopts GlobalOptions, opts KeyPasswdOptions) error {
-	pw, err := getNewPassword(ctx, gopts, opts.NewPasswordFile)
+	pw, err := getNewPassword(ctx, gopts, opts.NewPasswordFile, opts.InsecureNoPassword)
 	if err != nil {
 		return err
 	}

cmd/restic/global.go

@@ -52,22 +52,23 @@ type backendWrapper func(r backend.Backend) (backend.Backend, error)
 
 // GlobalOptions hold all global options for restic.
 type GlobalOptions struct {
-	Repo            string
+	Repo               string
-	RepositoryFile  string
+	RepositoryFile     string
-	PasswordFile    string
+	PasswordFile       string
-	PasswordCommand string
+	PasswordCommand    string
-	KeyHint         string
+	KeyHint            string
-	Quiet           bool
+	Quiet              bool
-	Verbose         int
+	Verbose            int
-	NoLock          bool
+	NoLock             bool
-	RetryLock       time.Duration
+	RetryLock          time.Duration
-	JSON            bool
+	JSON               bool
-	CacheDir        string
+	CacheDir           string
-	NoCache         bool
+	NoCache            bool
-	CleanupCache    bool
+	CleanupCache       bool
-	Compression     repository.CompressionMode
+	Compression        repository.CompressionMode
-	PackSize        uint
+	PackSize           uint
-	NoExtraVerify   bool
+	NoExtraVerify      bool
+	InsecureNoPassword bool
 
 	backend.TransportOptions
 	limiter.Limits
@@ -125,6 +126,7 @@ func init() {
 	f.BoolVar(&globalOptions.NoCache, "no-cache", false, "do not use a local cache")
 	f.StringSliceVar(&globalOptions.RootCertFilenames, "cacert", nil, "`file` to load root certificates from (default: use system certificates or $RESTIC_CACERT)")
 	f.StringVar(&globalOptions.TLSClientCertKeyFilename, "tls-client-cert", "", "path to a `file` containing PEM encoded TLS client certificate and private key (default: $RESTIC_TLS_CLIENT_CERT)")
+	f.BoolVar(&globalOptions.InsecureNoPassword, "insecure-no-password", false, "use an empty password for the repository, must be passed to every restic command (insecure)")
 	f.BoolVar(&globalOptions.InsecureTLS, "insecure-tls", false, "skip TLS certificate verification when connecting to the repository (insecure)")
 	f.BoolVar(&globalOptions.CleanupCache, "cleanup-cache", false, "auto remove old cache directories")
 	f.Var(&globalOptions.Compression, "compression", "compression mode (only available for repository format version 2), one of (auto|off|max) (default: $RESTIC_COMPRESSION)")
@@ -327,6 +329,13 @@ func readPasswordTerminal(ctx context.Context, in *os.File, out *os.File, prompt
 // variable RESTIC_PASSWORD or prompts the user. If the context is canceled,
 // the function leaks the password reading goroutine.
 func ReadPassword(ctx context.Context, opts GlobalOptions, prompt string) (string, error) {
+	if opts.InsecureNoPassword {
+		if opts.password != "" {
+			return "", errors.Fatal("--insecure-no-password must not be specified together with providing a password via a cli option or environment variable")
+		}
+		return "", nil
+	}
+
 	if opts.password != "" {
 		return opts.password, nil
 	}
@@ -348,7 +357,7 @@ func ReadPassword(ctx context.Context, opts GlobalOptions, prompt string) (strin
 	}
 
 	if len(password) == 0 {
-		return "", errors.Fatal("an empty password is not a password")
+		return "", errors.Fatal("an empty password is not allowed by default. Pass the flag `--insecure-no-password` to restic to disable this check")
 	}
 
 	return password, nil
@@ -445,7 +454,7 @@ func OpenRepository(ctx context.Context, opts GlobalOptions) (*repository.Reposi
 	}
 
 	passwordTriesLeft := 1
-	if stdinIsTerminal() && opts.password == "" {
+	if stdinIsTerminal() && opts.password == "" && !opts.InsecureNoPassword {
 		passwordTriesLeft = 3
 	}
 

cmd/restic/global_test.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"context"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	rtest "github.com/restic/restic/internal/test"
@@ -50,3 +52,14 @@ func TestReadRepo(t *testing.T) {
 		t.Fatal("must not read repository path from invalid file path")
 	}
 }
+
+func TestReadEmptyPassword(t *testing.T) {
+	opts := GlobalOptions{InsecureNoPassword: true}
+	password, err := ReadPassword(context.TODO(), opts, "test")
+	rtest.OK(t, err)
+	rtest.Equals(t, "", password, "got unexpected password")
+
+	opts.password = "invalid"
+	_, err = ReadPassword(context.TODO(), opts, "test")
+	rtest.Assert(t, strings.Contains(err.Error(), "must not be specified together with providing a password via a cli option or environment variable"), "unexpected error message, got %v", err)
+}

cmd/restic/secondary_repo.go

@@ -11,11 +11,12 @@ import (
 type secondaryRepoOptions struct {
 	password string
 	// from-repo options
-	Repo            string
+	Repo               string
-	RepositoryFile  string
+	RepositoryFile     string
-	PasswordFile    string
+	PasswordFile       string
-	PasswordCommand string
+	PasswordCommand    string
-	KeyHint         string
+	KeyHint            string
+	InsecureNoPassword bool
 	// repo2 options
 	LegacyRepo            string
 	LegacyRepositoryFile  string
@@ -49,6 +50,7 @@ func initSecondaryRepoOptions(f *pflag.FlagSet, opts *secondaryRepoOptions, repo
 	f.StringVarP(&opts.PasswordFile, "from-password-file", "", "", "`file` to read the source repository password from (default: $RESTIC_FROM_PASSWORD_FILE)")
 	f.StringVarP(&opts.KeyHint, "from-key-hint", "", "", "key ID of key to try decrypting the source repository first (default: $RESTIC_FROM_KEY_HINT)")
 	f.StringVarP(&opts.PasswordCommand, "from-password-command", "", "", "shell `command` to obtain the source repository password from (default: $RESTIC_FROM_PASSWORD_COMMAND)")
+	f.BoolVar(&opts.InsecureNoPassword, "from-insecure-no-password", false, "use an empty password for the source repository, must be passed to every restic command (insecure)")
 
 	opts.Repo = os.Getenv("RESTIC_FROM_REPOSITORY")
 	opts.RepositoryFile = os.Getenv("RESTIC_FROM_REPOSITORY_FILE")
@@ -63,7 +65,7 @@ func fillSecondaryGlobalOpts(ctx context.Context, opts secondaryRepoOptions, gop
 	}
 
 	hasFromRepo := opts.Repo != "" || opts.RepositoryFile != "" || opts.PasswordFile != "" ||
-		opts.KeyHint != "" || opts.PasswordCommand != ""
+		opts.KeyHint != "" || opts.PasswordCommand != "" || opts.InsecureNoPassword
 	hasRepo2 := opts.LegacyRepo != "" || opts.LegacyRepositoryFile != "" || opts.LegacyPasswordFile != "" ||
 		opts.LegacyKeyHint != "" || opts.LegacyPasswordCommand != ""
 
@@ -85,6 +87,7 @@ func fillSecondaryGlobalOpts(ctx context.Context, opts secondaryRepoOptions, gop
 		dstGopts.PasswordFile = opts.PasswordFile
 		dstGopts.PasswordCommand = opts.PasswordCommand
 		dstGopts.KeyHint = opts.KeyHint
+		dstGopts.InsecureNoPassword = opts.InsecureNoPassword
 
 		pwdEnv = "RESTIC_FROM_PASSWORD"
 		repoPrefix = "source"
@@ -98,6 +101,8 @@ func fillSecondaryGlobalOpts(ctx context.Context, opts secondaryRepoOptions, gop
 		dstGopts.PasswordFile = opts.LegacyPasswordFile
 		dstGopts.PasswordCommand = opts.LegacyPasswordCommand
 		dstGopts.KeyHint = opts.LegacyKeyHint
+		// keep existing bevhaior for legacy options
+		dstGopts.InsecureNoPassword = false
 
 		pwdEnv = "RESTIC_PASSWORD2"
 	}