Add label.InitLabels functioni. Allows generation of labels based on options

This will allow us to do the following with docker.

Customize the way that a labeling system like SELinux will run on a container.

    --label-opt="user:USER"  : Set the label user for the container
    --label-opt="role:ROLE"  : Set the label role for the container
    --label-opt="type:TYPE"  : Set the label type for the container
    --label-opt="level:LEVEL"  : Set the label level for the container
    --label-opt="disabled"  : Turn off label confinement for the container

Since we are passing a list of string options instead of a space separated
string of options, I will change function calls to use InitLabels instead of
GenLabels.  Genlabels interface is Deprecated.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

label/label.go

@@ -2,6 +2,13 @@
 
 package label
 
+// InitLabels returns the process label and file labels to be used within
+// the container.  A list of options can be passed into this function to alter
+// the labels.
+func InitLabels(options []string) (string, string, error) {
+	return "", "", nil
+}
+
 func GenLabels(options string) (string, string, error) {
 	return "", "", nil
 }
@@ -22,7 +29,7 @@ func Relabel(path string, fileLabel string, relabel string) error {
 	return nil
 }
 
-func GetPidCon(pid int) (string, error) {
+func GetPidLabel(pid int) (string, error) {
 	return "", nil
 }
 

label/label_selinux.go

@@ -9,30 +9,49 @@ import (
 	"github.com/docker/libcontainer/selinux"
 )
 
-func GenLabels(options string) (string, string, error) {
+// InitLabels returns the process label and file labels to be used within
+// the container.  A list of options can be passed into this function to alter
+// the labels.  The labels returned will include a random MCS String, that is
+// guaranteed to be unique.
+func InitLabels(options []string) (string, string, error) {
 	if !selinux.SelinuxEnabled() {
 		return "", "", nil
 	}
 	var err error
 	processLabel, mountLabel := selinux.GetLxcContexts()
 	if processLabel != "" {
-		var (
-			s = strings.Fields(options)
-			l = len(s)
-		)
-		if l > 0 {
-			pcon := selinux.NewContext(processLabel)
-			for i := 0; i < l; i++ {
-				o := strings.Split(s[i], "=")
-				pcon[o[0]] = o[1]
+		pcon := selinux.NewContext(processLabel)
+		mcon := selinux.NewContext(mountLabel)
+		for _, opt := range options {
+			if opt == "disable" {
+				return "", "", nil
+			}
+			if i := strings.Index(opt, ":"); i == -1 {
+				return "", "", fmt.Errorf("Bad SELinux Option")
+			}
+			con := strings.SplitN(opt, ":", 2)
+			pcon[con[0]] = con[1]
+			if con[0] == "level" || con[0] == "user" {
+				mcon[con[0]] = con[1]
 			}
-			processLabel = pcon.Get()
-			mountLabel, err = selinux.CopyLevel(processLabel, mountLabel)
 		}
+		processLabel = pcon.Get()
+		mountLabel = mcon.Get()
 	}
 	return processLabel, mountLabel, err
 }
 
+// DEPRECATED: The GenLabels function is only to be used during the transition to the official API.
+func GenLabels(options string) (string, string, error) {
+	return InitLabels(strings.Fields(options))
+}
+
+// FormatMountLabel returns a string to be used by the mount command.
+// The format of this string will be used to alter the labeling of the mountpoint.
+// The string returned is suitable to be used as the options field of the mount command.
+// If you need to have additional mount point options, you can pass them in as
+// the first parameter.  Second parameter is the label that you wish to apply
+// to all content in the mount point.
 func FormatMountLabel(src, mountLabel string) string {
 	if mountLabel != "" {
 		switch src {
@@ -45,6 +64,8 @@ func FormatMountLabel(src, mountLabel string) string {
 	return src
 }
 
+// SetProcessLabel takes a process label and tells the kernel to assign the
+// label to the next program executed by the current process.
 func SetProcessLabel(processLabel string) error {
 	if selinux.SelinuxEnabled() {
 		return selinux.Setexeccon(processLabel)
@@ -52,6 +73,9 @@ func SetProcessLabel(processLabel string) error {
 	return nil
 }
 
+// GetProcessLabel returns the process label that the kernel will assign
+// to the next program executed by the current process.  If "" is returned
+// this indicates that the default labeling will happen for the process.
 func GetProcessLabel() (string, error) {
 	if selinux.SelinuxEnabled() {
 		return selinux.Getexeccon()
@@ -59,6 +83,7 @@ func GetProcessLabel() (string, error) {
 	return "", nil
 }
 
+// SetFileLabel modifies the "path" label to the specified file label
 func SetFileLabel(path string, fileLabel string) error {
 	if selinux.SelinuxEnabled() && fileLabel != "" {
 		return selinux.Setfilecon(path, fileLabel)
@@ -83,17 +108,22 @@ func Relabel(path string, fileLabel string, relabel string) error {
 	return selinux.Chcon(path, fileLabel, true)
 }
 
-func GetPidCon(pid int) (string, error) {
+// GetPidLabel will return the label of the process running with the specified pid
+func GetPidLabel(pid int) (string, error) {
 	if !selinux.SelinuxEnabled() {
 		return "", nil
 	}
 	return selinux.Getpidcon(pid)
 }
 
+// Init initialises the labeling system
 func Init() {
 	selinux.SelinuxEnabled()
 }
 
+// ReserveLabel will record the fact that the MCS label has already been used.
+// This will prevent InitLabels from using the MCS label in a newly created
+// container
 func ReserveLabel(label string) error {
 	selinux.ReserveLabel(label)
 	return nil

label/label_selinux_test.go

@@ -0,0 +1,48 @@
+// +build selinux,linux
+
+package label
+
+import (
+	"testing"
+
+	"github.com/docker/libcontainer/selinux"
+)
+
+func TestInit(t *testing.T) {
+	if selinux.SelinuxEnabled() {
+		var testNull []string
+		plabel, mlabel, err := InitLabels(testNull)
+		if err != nil {
+			t.Log("InitLabels Failed")
+			t.Fatal(err)
+		}
+		testDisabled := []string{"disable"}
+		plabel, mlabel, err = InitLabels(testDisabled)
+		if err != nil {
+			t.Log("InitLabels Disabled Failed")
+			t.Fatal(err)
+		}
+		if plabel != "" {
+			t.Log("InitLabels Disabled Failed")
+			t.Fatal()
+		}
+		testUser := []string{"user:user_u", "role:user_r", "type:user_t", "level:s0:c1,c15"}
+		plabel, mlabel, err = InitLabels(testUser)
+		if err != nil {
+			t.Log("InitLabels User Failed")
+			t.Fatal(err)
+		}
+		if plabel != "user_u:user_r:user_t:s0:c1,c15" || mlabel != "user_u:object_r:svirt_sandbox_file_t:s0:c1,c15" {
+			t.Log("InitLabels User Failed")
+			t.Log(plabel, mlabel)
+			t.Fatal(err)
+		}
+
+		testBadData := []string{"user", "role:user_r", "type:user_t", "level:s0:c1,c15"}
+		plabel, mlabel, err = InitLabels(testBadData)
+		if err == nil {
+			t.Log("InitLabels Bad Failed")
+			t.Fatal(err)
+		}
+	}
+}