Merge pull request #1564 from restic/sftp-password-prompt

sftp: Prompt for password, don't terminate on SIGINT

cmd/restic/cleanup.go

@@ -22,19 +22,9 @@ var stderr = os.Stderr
 func init() {
 	cleanupHandlers.ch = make(chan os.Signal)
 	go CleanupHandler(cleanupHandlers.ch)
-	InstallSignalHandler()
-}
-
-// InstallSignalHandler listens for SIGINT, and triggers the cleanup handlers.
-func InstallSignalHandler() {
 	signal.Notify(cleanupHandlers.ch, syscall.SIGINT)
 }
 
-// SuspendSignalHandler removes the signal handler for SIGINT.
-func SuspendSignalHandler() {
-	signal.Reset(syscall.SIGINT)
-}
-
 // AddCleanupHandler adds the function f to the list of cleanup handlers so
 // that it is executed when all the cleanup handlers are run, e.g. when SIGINT
 // is received.

cmd/restic/global.go

@@ -555,7 +555,7 @@ func open(s string, gopts GlobalOptions, opts options.Options) (restic.Backend,
 		// wrap the backend in a LimitBackend so that the throughput is limited
 		be = limiter.LimitBackend(be, limiter.NewStaticLimiter(gopts.LimitUploadKb, gopts.LimitDownloadKb))
 	case "sftp":
-		be, err = sftp.Open(cfg.(sftp.Config), SuspendSignalHandler, InstallSignalHandler)
+		be, err = sftp.Open(cfg.(sftp.Config))
 		// wrap the backend in a LimitBackend so that the throughput is limited
 		be = limiter.LimitBackend(be, limiter.NewStaticLimiter(gopts.LimitUploadKb, gopts.LimitDownloadKb))
 	case "s3":
@@ -614,7 +614,7 @@ func create(s string, opts options.Options) (restic.Backend, error) {
 	case "local":
 		return local.Create(cfg.(local.Config))
 	case "sftp":
-		return sftp.Create(cfg.(sftp.Config), SuspendSignalHandler, InstallSignalHandler)
+		return sftp.Create(cfg.(sftp.Config))
 	case "s3":
 		return s3.Create(cfg.(s3.Config), rt)
 	case "gs":

internal/backend/sftp/foreground_unix.go

@@ -0,0 +1,73 @@
+// +build !windows
+
+package sftp
+
+import (
+	"os"
+	"os/exec"
+	"os/signal"
+	"syscall"
+	"unsafe"
+
+	"github.com/restic/restic/internal/errors"
+)
+
+func tcsetpgrp(fd int, pid int) error {
+	_, _, errno := syscall.RawSyscall(syscall.SYS_IOCTL, uintptr(fd),
+		uintptr(syscall.TIOCSPGRP), uintptr(unsafe.Pointer(&pid)))
+	if errno == 0 {
+		return nil
+	}
+
+	return errno
+}
+
+// startForeground runs cmd in the foreground, by temporarily switching to the
+// new process group created for cmd. The returned function `bg` switches back
+// to the previous process group.
+func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
+	// open the TTY, we need the file descriptor
+	tty, err := os.OpenFile("/dev/tty", os.O_RDWR, 0)
+	if err != nil {
+		return nil, errors.Wrap(err, "open TTY")
+	}
+
+	signal.Ignore(syscall.SIGTTIN)
+	signal.Ignore(syscall.SIGTTOU)
+
+	// run the command in its own process group
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+	}
+
+	// start the process
+	err = cmd.Start()
+	if err != nil {
+		_ = tty.Close()
+		return nil, errors.Wrap(err, "cmd.Start")
+	}
+
+	// move the command's process group into the foreground
+	prev := syscall.Getpgrp()
+	err = tcsetpgrp(int(tty.Fd()), cmd.Process.Pid)
+	if err != nil {
+		_ = tty.Close()
+		return nil, err
+	}
+
+	bg = func() error {
+		signal.Reset(syscall.SIGTTIN)
+		signal.Reset(syscall.SIGTTOU)
+
+		// reset the foreground process group
+		err = tcsetpgrp(int(tty.Fd()), prev)
+		if err != nil {
+			_ = tty.Close()
+			return err
+		}
+
+		return tty.Close()
+	}
+
+	return bg, nil
+}

internal/backend/sftp/foreground_windows.go

@@ -0,0 +1,21 @@
+package sftp
+
+import (
+	"os/exec"
+
+	"github.com/restic/restic/internal/errors"
+)
+
+// startForeground runs cmd in the foreground, by temporarily switching to the
+// new process group created for cmd. The returned function `bg` switches back
+// to the previous process group.
+func startForeground(cmd *exec.Cmd) (bg func() error, err error) {
+	// just start the process and hope for the best
+	err = cmd.Start()
+	if err != nil {
+		return nil, errors.Wrap(err, "cmd.Start")
+	}
+
+	bg = func() error { return nil }
+	return bg, nil
+}

internal/backend/sftp/layout_test.go

@@ -46,7 +46,7 @@ func TestLayout(t *testing.T) {
 				Command: fmt.Sprintf("%q -e", sftpServer),
 				Path:    repo,
 				Layout:  test.layout,
-			}, nil, nil)
+			})
 			if err != nil {
 				t.Fatal(err)
 			}

internal/backend/sftp/sftp.go

@@ -36,7 +36,7 @@ var _ restic.Backend = &SFTP{}
 
 const defaultLayout = "default"
 
-func startClient(preExec, postExec func(), program string, args ...string) (*SFTP, error) {
+func startClient(program string, args ...string) (*SFTP, error) {
 	debug.Log("start client %v %v", program, args)
 	// Connect to a remote host and request the sftp subsystem via the 'ssh'
 	// command.  This assumes that passwordless login is correctly configured.
@@ -65,19 +65,11 @@ func startClient(preExec, postExec func(), program string, args ...string) (*SFT
 		return nil, errors.Wrap(err, "cmd.StdoutPipe")
 	}
 
-	if preExec != nil {
+	bg, err := startForeground(cmd)
-		preExec()
+	if err != nil {
-	}
-
-	// start the process
-	if err := cmd.Start(); err != nil {
 		return nil, errors.Wrap(err, "cmd.Start")
 	}
 
-	if postExec != nil {
-		postExec()
-	}
-
 	// wait in a different goroutine
 	ch := make(chan error, 1)
 	go func() {
@@ -92,6 +84,11 @@ func startClient(preExec, postExec func(), program string, args ...string) (*SFT
 		return nil, errors.Errorf("unable to start the sftp session, error: %v", err)
 	}
 
+	err = bg()
+	if err != nil {
+		return nil, errors.Wrap(err, "bg")
+	}
+
 	return &SFTP{c: client, cmd: cmd, result: ch}, nil
 }
 
@@ -111,7 +108,7 @@ func (r *SFTP) clientError() error {
 // Open opens an sftp backend as described by the config by running
 // "ssh" with the appropriate arguments (or cfg.Command, if set). The function
 // preExec is run just before, postExec just after starting a program.
-func Open(cfg Config, preExec, postExec func()) (*SFTP, error) {
+func Open(cfg Config) (*SFTP, error) {
 	debug.Log("open backend with config %#v", cfg)
 
 	cmd, args, err := buildSSHCommand(cfg)
@@ -119,7 +116,7 @@ func Open(cfg Config, preExec, postExec func()) (*SFTP, error) {
 		return nil, err
 	}
 
-	sftp, err := startClient(preExec, postExec, cmd, args...)
+	sftp, err := startClient(cmd, args...)
 	if err != nil {
 		debug.Log("unable to start program: %v", err)
 		return nil, err
@@ -204,13 +201,13 @@ func buildSSHCommand(cfg Config) (cmd string, args []string, err error) {
 // Create creates an sftp backend as described by the config by running "ssh"
 // with the appropriate arguments (or cfg.Command, if set). The function
 // preExec is run just before, postExec just after starting a program.
-func Create(cfg Config, preExec, postExec func()) (*SFTP, error) {
+func Create(cfg Config) (*SFTP, error) {
 	cmd, args, err := buildSSHCommand(cfg)
 	if err != nil {
 		return nil, err
 	}
 
-	sftp, err := startClient(preExec, postExec, cmd, args...)
+	sftp, err := startClient(cmd, args...)
 	if err != nil {
 		debug.Log("unable to start program: %v", err)
 		return nil, err
@@ -238,7 +235,7 @@ func Create(cfg Config, preExec, postExec func()) (*SFTP, error) {
 	}
 
 	// open backend
-	return Open(cfg, preExec, postExec)
+	return Open(cfg)
 }
 
 // Location returns this backend's location (the directory name).

internal/backend/sftp/sftp_test.go

@@ -50,13 +50,13 @@ func newTestSuite(t testing.TB) *test.Suite {
 		// CreateFn is a function that creates a temporary repository for the tests.
 		Create: func(config interface{}) (restic.Backend, error) {
 			cfg := config.(sftp.Config)
-			return sftp.Create(cfg, nil, nil)
+			return sftp.Create(cfg)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
 		Open: func(config interface{}) (restic.Backend, error) {
 			cfg := config.(sftp.Config)
-			return sftp.Open(cfg, nil, nil)
+			return sftp.Open(cfg)
 		},
 
 		// CleanupFn removes data created during the tests.

internal/restic/node_unix_test.go

@@ -101,7 +101,7 @@ func TestNodeFromFileInfo(t *testing.T) {
 		t.Run("", func(t *testing.T) {
 			fi, found := stat(t, test.filename)
 			if !found && test.canSkip {
-				t.Skipf("%v not found in filesystem")
+				t.Skipf("%v not found in filesystem", test.filename)
 				return
 			}