96 lines
2.9 KiB
Go
96 lines
2.9 KiB
Go
// Copyright 2018 Google Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package sandbox
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"syscall"
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"gvisor.googlesource.com/gvisor/pkg/log"
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"gvisor.googlesource.com/gvisor/runsc/specutils"
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)
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// chrootBinPath is the location inside the chroot where the runsc binary will
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// be mounted.
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const chrootBinPath = "/runsc"
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// mountInChroot creates the destination mount point in the given chroot and
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// mounts the source.
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func mountInChroot(chroot, src, dst, typ string, flags uint32) error {
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chrootDst := filepath.Join(chroot, dst)
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log.Infof("Mounting %q at %q", src, chrootDst)
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if err := specutils.Mount(src, chrootDst, typ, flags); err != nil {
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return fmt.Errorf("error mounting %q at %q: %v", src, chrootDst, err)
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}
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return nil
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}
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// setUpChroot creates an empty directory with runsc mounted at /runsc and proc
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// mounted at /proc.
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func setUpChroot() (string, error) {
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// Create the chroot directory and make it accessible to all users.
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chroot, err := ioutil.TempDir("", "runsc-sandbox-chroot-")
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if err != nil {
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return "", fmt.Errorf("TempDir() failed: %v", err)
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}
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if err := os.Chmod(chroot, 0777); err != nil {
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return "", fmt.Errorf("Chmod(%q) failed: %v", chroot, err)
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}
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log.Infof("Setting up sandbox chroot in %q", chroot)
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// Mount /proc.
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if err := mountInChroot(chroot, "proc", "/proc", "proc", 0); err != nil {
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return "", fmt.Errorf("error mounting proc in chroot: %v", err)
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}
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// Mount runsc at /runsc in the chroot.
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binPath, err := specutils.BinPath()
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if err != nil {
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return "", err
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}
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if err := mountInChroot(chroot, binPath, chrootBinPath, "bind", syscall.MS_BIND|syscall.MS_RDONLY); err != nil {
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return "", fmt.Errorf("error mounting runsc in chroot: %v", err)
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}
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return chroot, nil
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}
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// tearDownChroot unmounts /proc and /runsc from the chroot before deleting the
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// directory.
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func tearDownChroot(chroot string) error {
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// Unmount /proc.
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proc := filepath.Join(chroot, "proc")
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if err := syscall.Unmount(proc, 0); err != nil {
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return fmt.Errorf("error unmounting %q: %v", proc, err)
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}
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// Unmount /runsc.
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exe := filepath.Join(chroot, chrootBinPath)
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if err := syscall.Unmount(exe, 0); err != nil {
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return fmt.Errorf("error unmounting %q: %v", exe, err)
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}
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// Remove chroot directory.
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if err := os.RemoveAll(chroot); err != nil {
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return fmt.Errorf("error removing %q: %v", chroot, err)
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}
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return nil
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}
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