validation: add a new test for NSPathMatchTypeError

`checkNSPathMatchType` checks if the container returns an error when
deliberately setting a wrong namespace type. Doing that, it is possible
to verify `NSPathMatchTypeError`, i.e. `The runtime MUST generate an
error if path is not associated with a namespace of type "type"`.

See also opencontainers#572

Signed-off-by: Dongsu Park <dongsu@kinvolk.io>

validation/linux_ns_path_type.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"fmt"
+	"os/exec"
+	"runtime"
+	"syscall"
+
+	"github.com/mndrix/tap-go"
+	rspec "github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/opencontainers/runtime-tools/specerror"
+	"github.com/opencontainers/runtime-tools/validation/util"
+)
+
+func getRuntimeToolsNamespace(ns string) string {
+	// Deal with exceptional cases of "net" and "mnt", because those strings
+	// cannot be recognized by mapStrToNamespace(), which actually expects
+	// "network" and "mount" respectively.
+	switch ns {
+	case "net":
+		return "network"
+	case "mnt":
+		return "mount"
+	}
+
+	// In other cases, return just the original string
+	return ns
+}
+
+func checkNSPathMatchType(t *tap.T, ns, wrongNs string) error {
+	// Deliberately set ns path with a wrong namespace, to check if the runtime
+	// returns error when running with the wrong namespace path.
+	unshareNsPath := fmt.Sprintf("/proc/self/ns/%s", wrongNs)
+
+	g, err := util.GetDefaultGenerator()
+	if err != nil {
+		return fmt.Errorf("cannot get default config from generator: %v", err)
+	}
+
+	rtns := getRuntimeToolsNamespace(ns)
+	g.AddOrReplaceLinuxNamespace(rtns, unshareNsPath)
+
+	err = util.RuntimeOutsideValidate(g, nil)
+
+	t.Ok(err != nil, fmt.Sprintf("got error when setting a wrong namespace path %q with type %s", unshareNsPath, rtns))
+	if err == nil {
+		rfcError, errRfc := specerror.NewRFCError(specerror.NSPathMatchTypeError,
+			fmt.Errorf("got no error when setting a wrong namespace path %q with type %s", unshareNsPath, rtns),
+			rspec.Version)
+		if errRfc != nil {
+			return fmt.Errorf("cannot get new rfcError: %v", errRfc)
+		}
+		diagnostic := map[string]string{
+			"expected":       fmt.Sprintf("err == %v", err),
+			"actual":         "err == nil",
+			"namespace type": rtns,
+			"level":          rfcError.Level.String(),
+			"reference":      rfcError.Reference,
+		}
+		t.YAML(diagnostic)
+
+		return fmt.Errorf("cannot validate path with wrong type")
+	}
+
+	return nil
+}
+
+func testNSPathMatchType(t *tap.T, ns, unshareOpt, wrongNs string) error {
+	// Calling 'unshare' (part of util-linux) is easier than doing it from
+	// Golang: mnt namespaces cannot be unshared from multithreaded
+	// programs.
+	cmd := exec.Command("unshare", unshareOpt, "--fork", "sleep", "10000")
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	err := cmd.Start()
+	if err != nil {
+		return fmt.Errorf("cannot run unshare: %s", err)
+	}
+	defer func() {
+		if cmd.Process != nil {
+			cmd.Process.Kill()
+		}
+		cmd.Wait()
+		syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
+	}()
+	if cmd.Process == nil {
+		return fmt.Errorf("process failed to start")
+	}
+
+	return checkNSPathMatchType(t, ns, wrongNs)
+}
+
+func main() {
+	t := tap.New()
+	t.Header(0)
+
+	cases := []struct {
+		name       string
+		unshareOpt string
+		wrongname  string
+	}{
+		{"cgroup", "--cgroup", "ipc"},
+		{"ipc", "--ipc", "mnt"},
+		{"mnt", "--mount", "net"},
+		{"net", "--net", "pid"},
+		{"pid", "--pid", "user"},
+		{"user", "--user", "uts"},
+		{"uts", "--uts", "cgroup"},
+	}
+
+	for _, c := range cases {
+		if "linux" != runtime.GOOS {
+			t.Skip(1, fmt.Sprintf("linux-specific namespace test: %s", c))
+		}
+
+		err := testNSPathMatchType(t, c.name, c.unshareOpt, c.wrongname)
+		t.Ok(err == nil, fmt.Sprintf("namespace path matches with type %s", c.name))
+	}
+
+	t.AutoPlan()
+}