libcontainer: configs: add proper HostUID and HostGID

Previously Host{U,G}ID only gave you the root mapping, which isn't very
useful if you are trying to do other things with the IDMaps.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

libcontainer/configs/config_unix.go

@@ -4,38 +4,50 @@ package configs
 
 import "fmt"
 
-// HostUID gets the root uid for the process on host which could be non-zero
-// when user namespaces are enabled.
-func (c Config) HostUID() (int, error) {
+// HostUID gets the translated uid for the process on host which could be
+// different when user namespaces are enabled.
+func (c Config) HostUID(containerId int) (int, error) {
 	if c.Namespaces.Contains(NEWUSER) {
 		if c.UidMappings == nil {
-			return -1, fmt.Errorf("User namespaces enabled, but no user mappings found.")
+			return -1, fmt.Errorf("User namespaces enabled, but no uid mappings found.")
 		}
-		id, found := c.hostIDFromMapping(0, c.UidMappings)
+		id, found := c.hostIDFromMapping(containerId, c.UidMappings)
 		if !found {
-			return -1, fmt.Errorf("User namespaces enabled, but no root user mapping found.")
+			return -1, fmt.Errorf("User namespaces enabled, but no user mapping found.")
 		}
 		return id, nil
 	}
-	// Return default root uid 0
-	return 0, nil
+	// Return unchanged id.
+	return containerId, nil
 }
 
-// HostGID gets the root gid for the process on host which could be non-zero
+// HostRootUID gets the root uid for the process on host which could be non-zero
 // when user namespaces are enabled.
-func (c Config) HostGID() (int, error) {
+func (c Config) HostRootUID() (int, error) {
+	return c.HostUID(0)
+}
+
+// HostGID gets the translated gid for the process on host which could be
+// different when user namespaces are enabled.
+func (c Config) HostGID(containerId int) (int, error) {
 	if c.Namespaces.Contains(NEWUSER) {
 		if c.GidMappings == nil {
 			return -1, fmt.Errorf("User namespaces enabled, but no gid mappings found.")
 		}
-		id, found := c.hostIDFromMapping(0, c.GidMappings)
+		id, found := c.hostIDFromMapping(containerId, c.GidMappings)
 		if !found {
-			return -1, fmt.Errorf("User namespaces enabled, but no root group mapping found.")
+			return -1, fmt.Errorf("User namespaces enabled, but no group mapping found.")
 		}
 		return id, nil
 	}
-	// Return default root gid 0
-	return 0, nil
+	// Return unchanged id.
+	return containerId, nil
+}
+
+// HostRootGID gets the root gid for the process on host which could be non-zero
+// when user namespaces are enabled.
+func (c Config) HostRootGID() (int, error) {
+	return c.HostGID(0)
 }
 
 // Utility function that gets a host ID for a container ID from user namespace map

libcontainer/configs/config_unix_test.go

@@ -65,11 +65,11 @@ func TestRemoveNamespace(t *testing.T) {
 	}
 }
 
-func TestHostUIDNoUSERNS(t *testing.T) {
+func TestHostRootUIDNoUSERNS(t *testing.T) {
 	config := &Config{
 		Namespaces: Namespaces{},
 	}
-	uid, err := config.HostUID()
+	uid, err := config.HostRootUID()
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -78,7 +78,7 @@ func TestHostUIDNoUSERNS(t *testing.T) {
 	}
 }
 
-func TestHostUIDWithUSERNS(t *testing.T) {
+func TestHostRootUIDWithUSERNS(t *testing.T) {
 	config := &Config{
 		Namespaces: Namespaces{{Type: NEWUSER}},
 		UidMappings: []IDMap{
@@ -89,7 +89,7 @@ func TestHostUIDWithUSERNS(t *testing.T) {
 			},
 		},
 	}
-	uid, err := config.HostUID()
+	uid, err := config.HostRootUID()
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -98,11 +98,11 @@ func TestHostUIDWithUSERNS(t *testing.T) {
 	}
 }
 
-func TestHostGIDNoUSERNS(t *testing.T) {
+func TestHostRootGIDNoUSERNS(t *testing.T) {
 	config := &Config{
 		Namespaces: Namespaces{},
 	}
-	uid, err := config.HostGID()
+	uid, err := config.HostRootGID()
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -111,7 +111,7 @@ func TestHostGIDNoUSERNS(t *testing.T) {
 	}
 }
 
-func TestHostGIDWithUSERNS(t *testing.T) {
+func TestHostRootGIDWithUSERNS(t *testing.T) {
 	config := &Config{
 		Namespaces: Namespaces{{Type: NEWUSER}},
 		GidMappings: []IDMap{
@@ -122,7 +122,7 @@ func TestHostGIDWithUSERNS(t *testing.T) {
 			},
 		},
 	}
-	uid, err := config.HostGID()
+	uid, err := config.HostRootGID()
 	if err != nil {
 		t.Fatal(err)
 	}

libcontainer/configs/validate/rootless.go

@@ -37,7 +37,7 @@ func (v *ConfigValidator) rootless(config *configs.Config) error {
 }
 
 func rootlessMappings(config *configs.Config) error {
-	rootuid, err := config.HostUID()
+	rootuid, err := config.HostRootUID()
 	if err != nil {
 		return fmt.Errorf("failed to get root uid from uidMappings: %v", err)
 	}
@@ -50,7 +50,7 @@ func rootlessMappings(config *configs.Config) error {
 		}
 	}
 
-	rootgid, err := config.HostGID()
+	rootgid, err := config.HostRootGID()
 	if err != nil {
 		return fmt.Errorf("failed to get root gid from gidMappings: %v", err)
 	}

libcontainer/container_linux.go

@@ -307,11 +307,11 @@ func (c *linuxContainer) Signal(s os.Signal, all bool) error {
 }
 
 func (c *linuxContainer) createExecFifo() error {
-	rootuid, err := c.Config().HostUID()
+	rootuid, err := c.Config().HostRootUID()
 	if err != nil {
 		return err
 	}
-	rootgid, err := c.Config().HostGID()
+	rootgid, err := c.Config().HostRootGID()
 	if err != nil {
 		return err
 	}

libcontainer/factory_linux.go

@@ -164,11 +164,11 @@ func (l *LinuxFactory) Create(id string, config *configs.Config) (Container, err
 	if err := l.Validator.Validate(config); err != nil {
 		return nil, newGenericError(err, ConfigInvalid)
 	}
-	uid, err := config.HostUID()
+	uid, err := config.HostRootUID()
 	if err != nil {
 		return nil, newGenericError(err, SystemError)
 	}
-	gid, err := config.HostGID()
+	gid, err := config.HostRootGID()
 	if err != nil {
 		return nil, newGenericError(err, SystemError)
 	}

libcontainer/specconv/spec_linux.go

@@ -610,11 +610,11 @@ func setupUserNamespace(spec *specs.Spec, config *configs.Config) error {
 	for _, m := range spec.Linux.GIDMappings {
 		config.GidMappings = append(config.GidMappings, create(m))
 	}
-	rootUID, err := config.HostUID()
+	rootUID, err := config.HostRootUID()
 	if err != nil {
 		return err
 	}
-	rootGID, err := config.HostGID()
+	rootGID, err := config.HostRootGID()
 	if err != nil {
 		return err
 	}

utils_linux.go

@@ -242,12 +242,12 @@ func (r *runner) run(config *specs.Process) (int, error) {
 	for i := baseFd; i < baseFd+r.preserveFDs; i++ {
 		process.ExtraFiles = append(process.ExtraFiles, os.NewFile(uintptr(i), "PreserveFD:"+strconv.Itoa(i)))
 	}
-	rootuid, err := r.container.Config().HostUID()
+	rootuid, err := r.container.Config().HostRootUID()
 	if err != nil {
 		r.destroy()
 		return -1, err
 	}
-	rootgid, err := r.container.Config().HostGID()
+	rootgid, err := r.container.Config().HostRootGID()
 	if err != nil {
 		r.destroy()
 		return -1, err