150 lines
3.6 KiB
Go
150 lines
3.6 KiB
Go
// +build linux
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/*
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Copyright 2017 The Kubernetes Authors.
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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*/
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package host_path
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import (
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"fmt"
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"k8s.io/utils/exec"
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)
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const (
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hostProcMountsNamespace = "/rootfs/proc/1/ns/mnt"
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nsenterCmd = "nsenter"
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statCmd = "stat"
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touchCmd = "touch"
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mkdirCmd = "mkdir"
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)
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// nsenterFileTypeChecker is part of experimental support for running the kubelet
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// in a container. nsenterFileTypeChecker works by executing "nsenter" to run commands in
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// the host's mount namespace.
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//
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// nsenterFileTypeChecker requires:
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//
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// 1. The host's root filesystem must be available at "/rootfs";
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// 2. The "nsenter" binary must be on the Kubelet process' PATH in the container's
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// filesystem;
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// 3. The Kubelet process must have CAP_SYS_ADMIN (required by "nsenter"); at
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// the present, this effectively means that the kubelet is running in a
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// privileged container;
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// 4. The host image must have "stat", "touch", "mkdir" binaries in "/bin", "/usr/sbin", or "/usr/bin";
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type nsenterFileTypeChecker struct {
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path string
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exists bool
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}
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func newNsenterFileTypeChecker(path string) (hostPathTypeChecker, error) {
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ftc := &nsenterFileTypeChecker{path: path}
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ftc.Exists()
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return ftc, nil
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}
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func (ftc *nsenterFileTypeChecker) Exists() bool {
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args := []string{
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fmt.Sprintf("--mount=%s", hostProcMountsNamespace),
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"--",
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"ls",
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ftc.path,
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}
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exec := exec.New()
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_, err := exec.Command(nsenterCmd, args...).CombinedOutput()
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if err == nil {
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ftc.exists = true
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}
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return ftc.exists
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}
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func (ftc *nsenterFileTypeChecker) IsFile() bool {
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if !ftc.Exists() {
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return false
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}
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return !ftc.IsDir()
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}
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func (ftc *nsenterFileTypeChecker) MakeFile() error {
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args := []string{
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fmt.Sprintf("--mount=%s", hostProcMountsNamespace),
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"--",
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touchCmd,
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ftc.path,
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}
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exec := exec.New()
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if _, err := exec.Command(nsenterCmd, args...).CombinedOutput(); err != nil {
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return err
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}
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return nil
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}
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func (ftc *nsenterFileTypeChecker) IsDir() bool {
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return ftc.checkMimetype("directory")
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}
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func (ftc *nsenterFileTypeChecker) MakeDir() error {
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args := []string{
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fmt.Sprintf("--mount=%s", hostProcMountsNamespace),
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"--",
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mkdirCmd,
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"-p",
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ftc.path,
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}
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exec := exec.New()
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if _, err := exec.Command(nsenterCmd, args...).CombinedOutput(); err != nil {
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return err
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}
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return nil
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}
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func (ftc *nsenterFileTypeChecker) IsBlock() bool {
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return ftc.checkMimetype("block special file")
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}
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func (ftc *nsenterFileTypeChecker) IsChar() bool {
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return ftc.checkMimetype("character special file")
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}
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func (ftc *nsenterFileTypeChecker) IsSocket() bool {
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return ftc.checkMimetype("socket")
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}
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func (ftc *nsenterFileTypeChecker) GetPath() string {
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return ftc.path
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}
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func (ftc *nsenterFileTypeChecker) checkMimetype(checkedType string) bool {
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if !ftc.Exists() {
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return false
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}
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args := []string{
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fmt.Sprintf("--mount=%s", hostProcMountsNamespace),
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"--",
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statCmd,
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"-L",
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`--printf "%F"`,
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ftc.path,
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}
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exec := exec.New()
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outputBytes, err := exec.Command(nsenterCmd, args...).CombinedOutput()
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if err != nil {
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return false
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}
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return string(outputBytes) == checkedType
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}
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