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ssh/tailssh: close tty on session close

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We were only closing on side of the pty/tty pair.
Close the other side too.

Thanks to @fritterhoff for reporting and debugging the issue!

Fixes #8119

Signed-off-by: Maisem Ali <maisem@tailscale.com>
This commit is contained in:
Maisem Ali 2023-05-17 12:18:23 -07:00 committed by Maisem Ali
parent 03e848e3b5
commit 0ca8bf1e26
2 changed files with 24 additions and 11 deletions
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20
ssh/tailssh/incubator.go
View File

@ -452,7 +452,7 @@ func (ss *sshSession) launchProcess() error {
return ss.startWithStdPipes()
}
ss.ptyReq = &ptyReq
pty, err := ss.startWithPTY()
pty, tty, err := ss.startWithPTY()
if err != nil {
return err
}
@ -461,10 +461,13 @@ func (ss *sshSession) launchProcess() error {
// dup.
ptyDup, err := syscall.Dup(int(pty.Fd()))
if err != nil {
pty.Close()
tty.Close()
return err
}
go resizeWindow(ptyDup /* arbitrary fd */, winCh)
ss.tty = tty
ss.stdin = pty
ss.stdout = os.NewFile(uintptr(ptyDup), pty.Name())
ss.stderr = nil // not available for pty
@ -544,17 +547,16 @@ func resizeWindow(fd int, winCh <-chan ssh.Window) {
}
// startWithPTY starts cmd with a pseudo-terminal attached to Stdin, Stdout and Stderr.
func (ss *sshSession) startWithPTY() (ptyFile *os.File, err error) {
func (ss *sshSession) startWithPTY() (ptyFile, tty *os.File, err error) {
ptyReq := ss.ptyReq
cmd := ss.cmd
if cmd == nil {
return nil, errors.New("nil ss.cmd")
return nil, nil, errors.New("nil ss.cmd")
}
if ptyReq == nil {
return nil, errors.New("nil ss.ptyReq")
return nil, nil, errors.New("nil ss.ptyReq")
}
var tty *os.File
ptyFile, tty, err = pty.Open()
if err != nil {
err = fmt.Errorf("pty.Open: %w", err)
@ -568,7 +570,7 @@ func (ss *sshSession) startWithPTY() (ptyFile *os.File, err error) {
}()
ptyRawConn, err := tty.SyscallConn()
if err != nil {
return nil, fmt.Errorf("SyscallConn: %w", err)
return nil, nil, fmt.Errorf("SyscallConn: %w", err)
}
var ctlErr error
if err := ptyRawConn.Control(func(fd uintptr) {
@ -615,10 +617,10 @@ func (ss *sshSession) startWithPTY() (ptyFile *os.File, err error) {
return
}
}); err != nil {
return nil, fmt.Errorf("ptyRawConn.Control: %w", err)
return nil, nil, fmt.Errorf("ptyRawConn.Control: %w", err)
}
if ctlErr != nil {
return nil, fmt.Errorf("ptyRawConn.Control func: %w", ctlErr)
return nil, nil, fmt.Errorf("ptyRawConn.Control func: %w", ctlErr)
}
cmd.SysProcAttr = &syscall.SysProcAttr{
Setctty: true,
@ -642,7 +644,7 @@ func (ss *sshSession) startWithPTY() (ptyFile *os.File, err error) {
if err = cmd.Start(); err != nil {
return
}
return ptyFile, nil
return ptyFile, tty, nil
}
// startWithStdPipes starts cmd with os.Pipe for Stdin, Stdout and Stderr.

13
ssh/tailssh/tailssh.go
View File

@ -28,6 +28,7 @@
"strings"
"sync"
"sync/atomic"
"syscall"
"time"
gossh "github.com/tailscale/golang-x-crypto/ssh"
@ -811,6 +812,7 @@ type sshSession struct {
stdout io.ReadCloser
stderr io.Reader // nil for pty sessions
ptyReq *ssh.Pty // non-nil for pty sessions
tty *os.File // non-nil for pty sessions, must be closed after process exits
// We use this sync.Once to ensure that we only terminate the process once,
// either it exits itself or is terminated
@ -1087,6 +1089,7 @@ func (ss *sshSession) run() {
}
go ss.killProcessOnContextDone()
var processDone atomic.Bool
go func() {
defer ss.stdin.Close()
if _, err := io.Copy(rec.writer("i", ss.stdin), ss); err != nil {
@ -1104,9 +1107,12 @@ func (ss *sshSession) run() {
defer ss.stdout.Close()
_, err := io.Copy(rec.writer("o", ss), ss.stdout)
if err != nil && !errors.Is(err, io.EOF) {
logf("stdout copy: %v", err)
isErrBecauseProcessExited := processDone.Load() && errors.Is(err, syscall.EIO)
if !isErrBecauseProcessExited {
logf("stdout copy: %v, %T", err)
ss.cancelCtx(err)
}
}
if openOutputStreams.Add(-1) == 0 {
ss.CloseWrite()
}
@ -1124,7 +1130,12 @@ func (ss *sshSession) run() {
}()
}
if ss.tty != nil {
// If running a tty session, close the tty when the session is done.
defer ss.tty.Close()
}
err = ss.cmd.Wait()
processDone.Store(true)
// This will either make the SSH Termination goroutine be a no-op,
// or itself will be a no-op because the process was killed by the
// aforementioned goroutine.