Add exec and terminal support

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

execution/executors/oci/console.go

@@ -0,0 +1,54 @@
+package oci
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// 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) (*os.File, string, error) {
+	master, err := os.OpenFile("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_CLOEXEC, 0)
+	if 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 master, console, 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
+}