label.go

/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package label

import (
	"sync"

	"github.com/opencontainers/selinux/go-selinux"
)

type Store struct {
	sync.Mutex
	levels   map[string]int
	Releaser func(string)
	Reserver func(string)
}

func NewStore() *Store {
	return &Store{
		levels:   map[string]int{},
		Releaser: selinux.ReleaseLabel,
		Reserver: selinux.ReserveLabel,
	}
}

func (s *Store) Reserve(label string) error {
	s.Lock()
	defer s.Unlock()

	context, err := selinux.NewContext(label)
	if err != nil {
		return err
	}

	level := context["level"]
	// no reason to count empty
	if level == "" {
		return nil
	}

	if _, ok := s.levels[level]; !ok {
		s.Reserver(label)
	}

	s.levels[level]++
	return nil
}

func (s *Store) Release(label string) {
	s.Lock()
	defer s.Unlock()

	context, err := selinux.NewContext(label)
	if err != nil {
		return
	}

	level := context["level"]
	if level == "" {
		return
	}

	count, ok := s.levels[level]
	if !ok {
		return
	}
	switch {
	case count == 1:
		s.Releaser(label)
		delete(s.levels, level)
	case count < 1:
		delete(s.levels, level)
	case count > 1:
		s.levels[level] = count - 1
	}
}