Local echo disabled when emergency shell is entered after mount timeout during password prompt

[nmeum]

While performing some tests with Booster on LUKS-encrypted system. I noticed that the BusyBox emergency shell does not have local echo enabled when it is started due to the mount_timeout option while Booster is prompting for a password.

This is due to the fact that the readPassword function correctly disables local echo:

booster/init/console.go

Lines 195 to 201 in 8666e7b

	newState := *termios
	newState.Lflag &^= unix.ECHO
	newState.Lflag |= unix.ICANON | unix.ISIG
	newState.Iflag |= unix.ICRNL
	if err := unix.IoctlSetTermios(fd, unix.TCSETS, &newState); err != nil {
	return nil, err
	}

The function also restores local echo via defer:

booster/init/console.go

Line 203 in 8666e7b

defer unix.IoctlSetTermios(fd, unix.TCSETS, termios)

However, I believe on mount timeout this function will not return (since it is executed in a different goroutine) and thus the defer statement is not executed. Hence, I think the emergencyShell implementation needs to restore some sort of sane stty settings:

booster/init/main.go

Lines 790 to 796 in edeff4c

	func emergencyShell() {
	if _, err := os.Stat("/usr/bin/busybox"); !os.IsNotExist(err) {
	if err := unix.Exec("/usr/bin/busybox", []string{"sh", "-I"}, nil); err != nil {
	severe("Unable to start an emergency shell: %v", err)
	}
	}
	}

This could either be achieved by executing something like busybox stty sane before spawing the shell (which would require the stty Busybox applet) or, alternatively, by manually modifying the termios settings accordingly (see readPassword code above).