blob: 5c8769b2e249f56387a622b3ce44aede45428001 [file] [log] [blame]
package libcontainer
import (
"fmt"
"os"
"path/filepath"
"syscall"
"unsafe"
"github.com/opencontainers/runc/libcontainer/label"
)
// NewConsole returns an initialized console that can be used within a container by copying bytes
// from the master side to the slave that is attached as the tty for the container's init process.
func NewConsole(uid, gid int) (Console, error) {
master, err := os.OpenFile("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_CLOEXEC, 0)
if err != nil {
return nil, err
}
if err := saneTerminal(master); err != nil {
return nil, err
}
console, err := ptsname(master)
if err != nil {
return nil, err
}
if err := unlockpt(master); err != nil {
return nil, err
}
if err := os.Chmod(console, 0600); err != nil {
return nil, err
}
if err := os.Chown(console, uid, gid); err != nil {
return nil, err
}
return &linuxConsole{
slavePath: console,
master: master,
}, nil
}
// newConsoleFromPath is an internal function returning an initialized console for use inside
// a container's MNT namespace.
func newConsoleFromPath(slavePath string) *linuxConsole {
return &linuxConsole{
slavePath: slavePath,
}
}
// linuxConsole is a linux pseudo TTY for use within a container.
type linuxConsole struct {
master *os.File
slavePath string
}
func (c *linuxConsole) Fd() uintptr {
return c.master.Fd()
}
func (c *linuxConsole) Path() string {
return c.slavePath
}
func (c *linuxConsole) Read(b []byte) (int, error) {
return c.master.Read(b)
}
func (c *linuxConsole) Write(b []byte) (int, error) {
return c.master.Write(b)
}
func (c *linuxConsole) Close() error {
if m := c.master; m != nil {
return m.Close()
}
return nil
}
// mount initializes the console inside the rootfs mounting with the specified mount label
// and applying the correct ownership of the console.
func (c *linuxConsole) mount(rootfs, mountLabel string) error {
oldMask := syscall.Umask(0000)
defer syscall.Umask(oldMask)
if err := label.SetFileLabel(c.slavePath, mountLabel); err != nil {
return err
}
dest := filepath.Join(rootfs, "/dev/console")
f, err := os.Create(dest)
if err != nil && !os.IsExist(err) {
return err
}
if f != nil {
f.Close()
}
return syscall.Mount(c.slavePath, dest, "bind", syscall.MS_BIND, "")
}
// dupStdio opens the slavePath for the console and dups the fds to the current
// processes stdio, fd 0,1,2.
func (c *linuxConsole) dupStdio() error {
slave, err := c.open(syscall.O_RDWR)
if err != nil {
return err
}
fd := int(slave.Fd())
for _, i := range []int{0, 1, 2} {
if err := syscall.Dup3(fd, i, 0); err != nil {
return err
}
}
return nil
}
// open is a clone of os.OpenFile without the O_CLOEXEC used to open the pty slave.
func (c *linuxConsole) open(flag int) (*os.File, error) {
r, e := syscall.Open(c.slavePath, flag, 0)
if e != nil {
return nil, &os.PathError{
Op: "open",
Path: c.slavePath,
Err: e,
}
}
return os.NewFile(uintptr(r), c.slavePath), nil
}
func ioctl(fd uintptr, flag, data uintptr) error {
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, flag, data); err != 0 {
return err
}
return nil
}
// unlockpt unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by f.
// unlockpt should be called before opening the slave side of a pty.
func unlockpt(f *os.File) error {
var u int32
return ioctl(f.Fd(), syscall.TIOCSPTLCK, uintptr(unsafe.Pointer(&u)))
}
// ptsname retrieves the name of the first available pts for the given master.
func ptsname(f *os.File) (string, error) {
var n int32
if err := ioctl(f.Fd(), syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n))); err != nil {
return "", err
}
return fmt.Sprintf("/dev/pts/%d", n), nil
}
// saneTerminal sets the necessary tty_ioctl(4)s to ensure that a pty pair
// created by us acts normally. In particular, a not-very-well-known default of
// Linux unix98 ptys is that they have +onlcr by default. While this isn't a
// problem for terminal emulators, because we relay data from the terminal we
// also relay that funky line discipline.
func saneTerminal(terminal *os.File) error {
// Go doesn't have a wrapper for any of the termios ioctls.
var termios syscall.Termios
if err := ioctl(terminal.Fd(), syscall.TCGETS, uintptr(unsafe.Pointer(&termios))); err != nil {
return fmt.Errorf("ioctl(tty, tcgets): %s", err.Error())
}
// Set -onlcr so we don't have to deal with \r.
termios.Oflag &^= syscall.ONLCR
if err := ioctl(terminal.Fd(), syscall.TCSETS, uintptr(unsafe.Pointer(&termios))); err != nil {
return fmt.Errorf("ioctl(tty, tcsets): %s", err.Error())
}
return nil
}