Refactor pkg/util/selinux

pkg/kubelet/kubelet_volumes.go

@@ -94,7 +94,7 @@ func (kl *Kubelet) relabelVolumes(pod *api.Pod, volumes kubecontainer.VolumeMap)
 		return err
 	}
 
-	selinuxRunner := selinux.NewSelinuxContextRunner()
+	selinuxRunner := selinux.NewSELinuxRunner()
 	// Apply the pod's Level to the rootDirContext
 	rootDirSELinuxOptions, err := securitycontext.ParseSELinuxOptions(rootDirContext)
 	if err != nil {
@@ -115,7 +115,7 @@ func (kl *Kubelet) relabelVolumes(pod *api.Pod, volumes kubecontainer.VolumeMap)
 				if err != nil {
 					return err
 				}
-				return selinuxRunner.SetContext(path, volumeContext)
+				return selinuxRunner.Setfilecon(path, volumeContext)
 			})
 			if err != nil {
 				return err

pkg/kubelet/rkt/rkt.go

@@ -1082,7 +1082,7 @@ func (r *Runtime) preparePodArgs(manifest *appcschema.PodManifest, manifestFileN
 }
 
 func (r *Runtime) getSelinuxContext(opt *api.SELinuxOptions) (string, error) {
-	selinuxRunner := selinux.NewSelinuxContextRunner()
+	selinuxRunner := selinux.NewSELinuxRunner()
 	str, err := selinuxRunner.Getfilecon(r.config.Dir)
 	if err != nil {
 		return "", err

pkg/util/selinux/doc.go

@@ -14,5 +14,6 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-// Package selinux contains selinux utility functions.
+// Package selinux contains wrapper functions for the libcontainer SELinux
+// package.  A NOP implementation is provided for non-linux platforms.
 package selinux // import "k8s.io/kubernetes/pkg/util/selinux"

pkg/util/selinux/selinux.go

@@ -16,14 +16,24 @@ limitations under the License.
 
 package selinux
 
-// SelinuxContextRunner knows how to chcon of a directory and
-// how to get the selinux context of a file.
-type SelinuxContextRunner interface {
-	SetContext(dir, context string) error
+// Note: the libcontainer SELinux package is only built for Linux, so it is
+// necessary to have a NOP wrapper which is built for non-Linux platforms to
+// allow code that links to this package not to differentiate its own methods
+// for Linux and non-Linux platforms.
+//
+// SELinuxRunner wraps certain libcontainer SELinux calls. For more
+// information, see:
+//
+// https://github.com/opencontainers/runc/blob/master/libcontainer/selinux/selinux.go
+type SELinuxRunner interface {
+	// Getfilecon returns the SELinux context for the given path or returns an
+	// error.
 	Getfilecon(path string) (string, error)
 }
 
-// NewSelinuxContextRunner returns a new chconRunner.
-func NewSelinuxContextRunner() SelinuxContextRunner {
-	return &realSelinuxContextRunner{}
+// NewSELinuxRunner returns a new SELinuxRunner appropriate for the platform.
+// On Linux, all methods short-circuit and return NOP values if SELinux is
+// disabled. On non-Linux platforms, a NOP implementation is returned.
+func NewSELinuxRunner() SELinuxRunner {
+	return &realSELinuxRunner{}
 }

pkg/util/selinux/selinux_linux.go

@@ -19,25 +19,34 @@ limitations under the License.
 package selinux
 
 import (
-	"fmt"
-
 	"github.com/opencontainers/runc/libcontainer/selinux"
 )
 
-type realSelinuxContextRunner struct{}
+// SELinuxEnabled returns whether SELinux is enabled on the system.  SELinux
+// has a tri-state:
+//
+// 1.  disabled: SELinux Kernel modules not loaded, SELinux policy is not
+//     checked during Kernel MAC checks
+// 2.  enforcing: Enabled; SELinux policy violations are denied and logged
+//     in the audit log
+// 3.  permissive: Enabled, but SELinux policy violations are permitted and
+//     logged in the audit log
+//
+// SELinuxEnabled returns true if SELinux is enforcing or permissive, and
+// false if it is disabled.
+func SELinuxEnabled() bool {
+	return selinux.SelinuxEnabled()
+}
 
-func (_ *realSelinuxContextRunner) SetContext(dir, context string) error {
-	// If SELinux is not enabled, return an empty string
-	if !selinux.SelinuxEnabled() {
-		return nil
-	}
+// realSELinuxRunner is the real implementation of SELinuxRunner interface for
+// Linux.
+type realSELinuxRunner struct{}
 
-	return selinux.Setfilecon(dir, context)
-}
+var _ SELinuxRunner = &realSELinuxRunner{}
 
-func (_ *realSelinuxContextRunner) Getfilecon(path string) (string, error) {
-	if !selinux.SelinuxEnabled() {
-		return "", fmt.Errorf("SELinux is not enabled")
+func (_ *realSELinuxRunner) Getfilecon(path string) (string, error) {
+	if !SELinuxEnabled() {
+		return "", nil
 	}
 	return selinux.Getfilecon(path)
 }

pkg/util/selinux/selinux_unsupported.go

@@ -18,14 +18,16 @@ limitations under the License.
 
 package selinux
 
-type realSelinuxContextRunner struct{}
-
-func (_ *realSelinuxContextRunner) SetContext(dir, context string) error {
-	// NOP
-	return nil
+// SELinuxEnabled always returns false on non-linux platforms.
+func SELinuxEnabled() bool {
+	return false
 }
 
-func (_ *realSelinuxContextRunner) Getfilecon(path string) (string, error) {
-	// NOP
+// realSELinuxRunner is the NOP implementation of the SELinuxRunner interface.
+type realSELinuxRunner struct{}
+
+var _ SELinuxRunner = &realSELinuxRunner{}
+
+func (_ *realSELinuxRunner) Getfilecon(path string) (string, error) {
 	return "", nil
 }

pkg/volume/empty_dir/empty_dir.go

@@ -25,6 +25,7 @@ import (
 	"k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/types"
 	"k8s.io/kubernetes/pkg/util/mount"
+	"k8s.io/kubernetes/pkg/util/selinux"
 	"k8s.io/kubernetes/pkg/util/strings"
 	"k8s.io/kubernetes/pkg/volume"
 	volumeutil "k8s.io/kubernetes/pkg/volume/util"
@@ -204,7 +205,7 @@ func (ed *emptyDir) SetUpAt(dir string, fsGroup *int64) error {
 
 	// Determine the effective SELinuxOptions to use for this volume.
 	securityContext := ""
-	if selinuxEnabled() {
+	if selinux.SELinuxEnabled() {
 		securityContext = ed.rootContext
 	}
 

pkg/volume/empty_dir/empty_dir_linux.go

@@ -23,7 +23,6 @@ import (
 	"syscall"
 
 	"github.com/golang/glog"
-	"github.com/opencontainers/runc/libcontainer/selinux"
 	"k8s.io/kubernetes/pkg/util/mount"
 )
 
@@ -52,8 +51,3 @@ func (m *realMountDetector) GetMountMedium(path string) (storageMedium, bool, er
 	}
 	return mediumUnknown, !notMnt, nil
 }
-
-// selinuxEnabled determines whether SELinux is enabled.
-func selinuxEnabled() bool {
-	return selinux.SelinuxEnabled()
-}

pkg/volume/empty_dir/empty_dir_unsupported.go

@@ -30,7 +30,3 @@ type realMountDetector struct {
 func (m *realMountDetector) GetMountMedium(path string) (storageMedium, bool, error) {
 	return mediumUnknown, false, nil
 }
-
-func selinuxEnabled() bool {
-	return false
-}