podman

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//go:build linux
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// +build linux
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package chroot
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import (
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	"fmt"
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	"os"
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	"syscall"
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	"unsafe"
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	"golang.org/x/sys/unix"
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)
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// Open a PTY using the /dev/ptmx device. The main advantage of using
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// this instead of posix_openpt is that it avoids cgo.
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func getPtyDescriptors() (int, int, error) {
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	// Create a pseudo-terminal -- open a copy of the master side.
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	controlFd, err := unix.Open("/dev/ptmx", os.O_RDWR, 0600)
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	if err != nil {
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		return -1, -1, fmt.Errorf("opening PTY master using /dev/ptmx: %v", err)
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	}
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	// Set the kernel's lock to "unlocked".
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	locked := 0
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	if result, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(controlFd), unix.TIOCSPTLCK, uintptr(unsafe.Pointer(&locked))); int(result) == -1 {
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		return -1, -1, fmt.Errorf("unlocking PTY descriptor: %v", err)
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	}
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	// Get a handle for the other end.
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	ptyFd, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(controlFd), unix.TIOCGPTPEER, unix.O_RDWR|unix.O_NOCTTY)
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	if int(ptyFd) == -1 {
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		if errno, isErrno := err.(syscall.Errno); !isErrno || (errno != syscall.EINVAL && errno != syscall.ENOTTY) {
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			return -1, -1, fmt.Errorf("getting PTY descriptor: %v", err)
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		}
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		// EINVAL means the kernel's too old to understand TIOCGPTPEER.  Try TIOCGPTN.
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		ptyN, err := unix.IoctlGetInt(controlFd, unix.TIOCGPTN)
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		if err != nil {
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			return -1, -1, fmt.Errorf("getting PTY number: %v", err)
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		}
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		ptyName := fmt.Sprintf("/dev/pts/%d", ptyN)
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		fd, err := unix.Open(ptyName, unix.O_RDWR|unix.O_NOCTTY, 0620)
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		if err != nil {
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			return -1, -1, fmt.Errorf("opening PTY %q: %v", ptyName, err)
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		}
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		ptyFd = uintptr(fd)
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	}
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	return controlFd, int(ptyFd), nil
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}
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