cp.go

/*
Copyright 2016 The Kubernetes 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 cmd

import (
	"archive/tar"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path"
	"path/filepath"
	"strings"

	"k8s.io/cli-runtime/pkg/genericclioptions"
	"k8s.io/client-go/kubernetes"
	restclient "k8s.io/client-go/rest"
	"k8s.io/kubernetes/pkg/kubectl/cmd/templates"
	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
	"k8s.io/kubernetes/pkg/kubectl/util/i18n"

	"bytes"

	"github.com/renstrom/dedent"
	"github.com/spf13/cobra"
)

var (
	cpExample = templates.Examples(i18n.T(`
		# !!!Important Note!!!
		# Requires that the 'tar' binary is present in your container
		# image.  If 'tar' is not present, 'kubectl cp' will fail.

		# Copy /tmp/foo_dir local directory to /tmp/bar_dir in a remote pod in the default namespace
		kubectl cp /tmp/foo_dir <some-pod>:/tmp/bar_dir

		# Copy /tmp/foo local file to /tmp/bar in a remote pod in a specific container
		kubectl cp /tmp/foo <some-pod>:/tmp/bar -c <specific-container>

		# Copy /tmp/foo local file to /tmp/bar in a remote pod in namespace <some-namespace>
		kubectl cp /tmp/foo <some-namespace>/<some-pod>:/tmp/bar

		# Copy /tmp/foo from a remote pod to /tmp/bar locally
		kubectl cp <some-namespace>/<some-pod>:/tmp/foo /tmp/bar`))

	cpUsageStr = dedent.Dedent(`
		expected 'cp <file-spec-src> <file-spec-dest> [-c container]'.
		<file-spec> is:
		[namespace/]pod-name:/file/path for a remote file
		/file/path for a local file`)
)

type CopyOptions struct {
	Container string
	Namespace string

	ClientConfig *restclient.Config
	Clientset    kubernetes.Interface

	genericclioptions.IOStreams
}

func NewCopyOptions(ioStreams genericclioptions.IOStreams) *CopyOptions {
	return &CopyOptions{
		IOStreams: ioStreams,
	}
}

// NewCmdCp creates a new Copy command.
func NewCmdCp(f cmdutil.Factory, ioStreams genericclioptions.IOStreams) *cobra.Command {
	o := NewCopyOptions(ioStreams)

	cmd := &cobra.Command{
		Use: "cp <file-spec-src> <file-spec-dest>",
		DisableFlagsInUseLine: true,
		Short:   i18n.T("Copy files and directories to and from containers."),
		Long:    "Copy files and directories to and from containers.",
		Example: cpExample,
		Run: func(cmd *cobra.Command, args []string) {
			cmdutil.CheckErr(o.Complete(f, cmd))
			cmdutil.CheckErr(o.Run(args))
		},
	}
	cmd.Flags().StringVarP(&o.Container, "container", "c", o.Container, "Container name. If omitted, the first container in the pod will be chosen")

	return cmd
}

type fileSpec struct {
	PodNamespace string
	PodName      string
	File         string
}

var (
	errFileSpecDoesntMatchFormat = errors.New("Filespec must match the canonical format: [[namespace/]pod:]file/path")
	errFileCannotBeEmpty         = errors.New("Filepath can not be empty")
)

func extractFileSpec(arg string) (fileSpec, error) {
	if i := strings.Index(arg, ":"); i == -1 {
		return fileSpec{File: arg}, nil
	} else if i > 0 {
		file := arg[i+1:]
		pod := arg[:i]
		pieces := strings.Split(pod, "/")
		if len(pieces) == 1 {
			return fileSpec{
				PodName: pieces[0],
				File:    file,
			}, nil
		}
		if len(pieces) == 2 {
			return fileSpec{
				PodNamespace: pieces[0],
				PodName:      pieces[1],
				File:         file,
			}, nil
		}
	}

	return fileSpec{}, errFileSpecDoesntMatchFormat
}

func (o *CopyOptions) Complete(f cmdutil.Factory, cmd *cobra.Command) error {
	var err error
	o.Namespace, _, err = f.ToRawKubeConfigLoader().Namespace()
	if err != nil {
		return err
	}

	o.Clientset, err = f.KubernetesClientSet()
	if err != nil {
		return err
	}

	o.ClientConfig, err = f.ToRESTConfig()
	if err != nil {
		return err
	}
	return nil
}

func (o *CopyOptions) Validate(cmd *cobra.Command, args []string) error {
	if len(args) != 2 {
		return cmdutil.UsageErrorf(cmd, cpUsageStr)
	}
	return nil
}

func (o *CopyOptions) Run(args []string) error {
	if len(args) < 2 {
		return fmt.Errorf("source and destination are required")
	}
	srcSpec, err := extractFileSpec(args[0])
	if err != nil {
		return err
	}
	destSpec, err := extractFileSpec(args[1])
	if err != nil {
		return err
	}

	if len(srcSpec.PodName) != 0 && len(destSpec.PodName) != 0 {
		if _, err := os.Stat(args[0]); err == nil {
			return o.copyToPod(fileSpec{File: args[0]}, destSpec)
		}
		return fmt.Errorf("src doesn't exist in local filesystem")
	}

	if len(srcSpec.PodName) != 0 {
		return o.copyFromPod(srcSpec, destSpec)
	}
	if len(destSpec.PodName) != 0 {
		return o.copyToPod(srcSpec, destSpec)
	}
	return fmt.Errorf("one of src or dest must be a remote file specification")
}

// checkDestinationIsDir receives a destination fileSpec and
// determines if the provided destination path exists on the
// pod. If the destination path does not exist or is _not_ a
// directory, an error is returned with the exit code received.
func (o *CopyOptions) checkDestinationIsDir(dest fileSpec) error {
	options := &ExecOptions{
		StreamOptions: StreamOptions{
			IOStreams: genericclioptions.IOStreams{
				Out:    bytes.NewBuffer([]byte{}),
				ErrOut: bytes.NewBuffer([]byte{}),
			},

			Namespace: dest.PodNamespace,
			PodName:   dest.PodName,
		},

		Command:  []string{"test", "-d", dest.File},
		Executor: &DefaultRemoteExecutor{},
	}

	return o.execute(options)
}

func (o *CopyOptions) copyToPod(src, dest fileSpec) error {
	if len(src.File) == 0 || len(dest.File) == 0 {
		return errFileCannotBeEmpty
	}
	reader, writer := io.Pipe()

	// strip trailing slash (if any)
	if dest.File != "/" && strings.HasSuffix(string(dest.File[len(dest.File)-1]), "/") {
		dest.File = dest.File[:len(dest.File)-1]
	}

	if err := o.checkDestinationIsDir(dest); err == nil {
		// If no error, dest.File was found to be a directory.
		// Copy specified src into it
		dest.File = dest.File + "/" + path.Base(src.File)
	}

	go func() {
		defer writer.Close()
		err := makeTar(src.File, dest.File, writer)
		cmdutil.CheckErr(err)
	}()

	// TODO: Improve error messages by first testing if 'tar' is present in the container?
	cmdArr := []string{"tar", "xf", "-"}
	destDir := path.Dir(dest.File)
	if len(destDir) > 0 {
		cmdArr = append(cmdArr, "-C", destDir)
	}

	options := &ExecOptions{
		StreamOptions: StreamOptions{
			IOStreams: genericclioptions.IOStreams{
				In:     reader,
				Out:    o.Out,
				ErrOut: o.ErrOut,
			},
			Stdin: true,

			Namespace: dest.PodNamespace,
			PodName:   dest.PodName,
		},

		Command:  cmdArr,
		Executor: &DefaultRemoteExecutor{},
	}
	return o.execute(options)
}

func (o *CopyOptions) copyFromPod(src, dest fileSpec) error {
	if len(src.File) == 0 || len(dest.File) == 0 {
		return errFileCannotBeEmpty
	}

	reader, outStream := io.Pipe()
	options := &ExecOptions{
		StreamOptions: StreamOptions{
			IOStreams: genericclioptions.IOStreams{
				In:     nil,
				Out:    outStream,
				ErrOut: o.Out,
			},

			Namespace: src.PodNamespace,
			PodName:   src.PodName,
		},

		// TODO: Improve error messages by first testing if 'tar' is present in the container?
		Command:  []string{"tar", "cf", "-", src.File},
		Executor: &DefaultRemoteExecutor{},
	}

	go func() {
		defer outStream.Close()
		o.execute(options)
	}()
	prefix := getPrefix(src.File)
	prefix = path.Clean(prefix)
	// remove extraneous path shortcuts - these could occur if a path contained extra "../"
	// and attempted to navigate beyond "/" in a remote filesystem
	prefix = stripPathShortcuts(prefix)
	return o.untarAll(reader, dest.File, prefix)
}

// stripPathShortcuts removes any leading or trailing "../" from a given path
func stripPathShortcuts(p string) string {
	newPath := path.Clean(p)
	trimmed := strings.TrimPrefix(newPath, "../")

	for trimmed != newPath {
		newPath = trimmed
		trimmed = strings.TrimPrefix(newPath, "../")
	}

	// trim leftover {".", ".."}
	if newPath == "." || newPath == ".." {
		newPath = ""
	}

	if len(newPath) > 0 && string(newPath[0]) == "/" {
		return newPath[1:]
	}

	return newPath
}

func makeTar(srcPath, destPath string, writer io.Writer) error {
	// TODO: use compression here?
	tarWriter := tar.NewWriter(writer)
	defer tarWriter.Close()

	srcPath = path.Clean(srcPath)
	destPath = path.Clean(destPath)
	return recursiveTar(path.Dir(srcPath), path.Base(srcPath), path.Dir(destPath), path.Base(destPath), tarWriter)
}

func recursiveTar(srcBase, srcFile, destBase, destFile string, tw *tar.Writer) error {
	filepath := path.Join(srcBase, srcFile)
	stat, err := os.Lstat(filepath)
	if err != nil {
		return err
	}
	if stat.IsDir() {
		files, err := ioutil.ReadDir(filepath)
		if err != nil {
			return err
		}
		if len(files) == 0 {
			//case empty directory
			hdr, _ := tar.FileInfoHeader(stat, filepath)
			hdr.Name = destFile
			if err := tw.WriteHeader(hdr); err != nil {
				return err
			}
		}
		for _, f := range files {
			if err := recursiveTar(srcBase, path.Join(srcFile, f.Name()), destBase, path.Join(destFile, f.Name()), tw); err != nil {
				return err
			}
		}
		return nil
	} else if stat.Mode()&os.ModeSymlink != 0 {
		//case soft link
		hdr, _ := tar.FileInfoHeader(stat, filepath)
		target, err := os.Readlink(filepath)
		if err != nil {
			return err
		}

		hdr.Linkname = target
		hdr.Name = destFile
		if err := tw.WriteHeader(hdr); err != nil {
			return err
		}
	} else {
		//case regular file or other file type like pipe
		hdr, err := tar.FileInfoHeader(stat, filepath)
		if err != nil {
			return err
		}
		hdr.Name = destFile

		if err := tw.WriteHeader(hdr); err != nil {
			return err
		}

		f, err := os.Open(filepath)
		if err != nil {
			return err
		}
		defer f.Close()

		if _, err := io.Copy(tw, f); err != nil {
			return err
		}
		return f.Close()
	}
	return nil
}

// clean prevents path traversals by stripping them out.
// This is adapted from https://golang.org/src/net/http/fs.go#L74
func clean(fileName string) string {
	return path.Clean(string(os.PathSeparator) + fileName)
}

func (o *CopyOptions) untarAll(reader io.Reader, destDir, prefix string) error {
	// TODO: use compression here?
	tarReader := tar.NewReader(reader)
	for {
		header, err := tarReader.Next()
		if err != nil {
			if err != io.EOF {
				return err
			}
			break
		}

		// All the files will start with the prefix, which is the directory where
		// they were located on the pod, we need to strip down that prefix, but
		// if the prefix is missing it means the tar was tempered with.
		// For the case where prefix is empty we need to ensure that the path
		// is not absolute, which also indicates the tar file was tempered with.
		if !strings.HasPrefix(header.Name, prefix) {
			return fmt.Errorf("tar contents corrupted")
		}

		// basic file information
		mode := header.FileInfo().Mode()
		destFileName := path.Join(destDir, header.Name[len(prefix):])
		baseName := path.Dir(destFileName)

		if err := os.MkdirAll(baseName, 0755); err != nil {
			return err
		}
		if header.FileInfo().IsDir() {
			if err := os.MkdirAll(destFileName, 0755); err != nil {
				return err
			}
			continue
		}

		// We need to ensure that the destination file is always within boundries
		// of the destination directory. This prevents any kind of path traversal
		// from within tar archive.
		dir, file := filepath.Split(destFileName)
		evaledPath, err := filepath.EvalSymlinks(dir)
		if err != nil {
			return err
		}
		// For scrutiny we verify both the actual destination as well as we follow
		// all the links that might lead outside of the destination directory.
		if !isDestRelative(destDir, destFileName) || !isDestRelative(destDir, filepath.Join(evaledPath, file)) {
			fmt.Fprintf(o.IOStreams.ErrOut, "warning: link %q is pointing to %q which is outside target destination, skipping\n", destFileName, header.Linkname)
			continue
		}

		if mode&os.ModeSymlink != 0 {
			linkname := header.Linkname
			// We need to ensure that the link destination is always within boundries
			// of the destination directory. This prevents any kind of path traversal
			// from within tar archive.
			if !isDestRelative(destDir, linkJoin(destFileName, linkname)) {
				fmt.Fprintf(o.IOStreams.ErrOut, "warning: link %q is pointing to %q which is outside target destination, skipping\n", destFileName, header.Linkname)
				continue
			}
			if err := os.Symlink(linkname, destFileName); err != nil {
				return err
			}
		} else {
			outFile, err := os.Create(destFileName)
			if err != nil {
				return err
			}
			defer outFile.Close()
			if _, err := io.Copy(outFile, tarReader); err != nil {
				return err
			}
			if err := outFile.Close(); err != nil {
				return err
			}
		}
	}

	return nil
}

// linkJoin joins base and link to get the final path to be created.
// It will consider whether link is an absolute path or not when returning result.
func linkJoin(base, link string) string {
	if filepath.IsAbs(link) {
		return link
	}
	return filepath.Join(base, link)
}

// isDestRelative returns true if dest is pointing outside the base directory,
// false otherwise.
func isDestRelative(base, dest string) bool {
	fullPath := dest
	if !filepath.IsAbs(dest) {
		fullPath = filepath.Join(base, dest)
	}
	relative, err := filepath.Rel(base, fullPath)
	if err != nil {
		return false
	}
	return relative == "." || relative == stripPathShortcuts(relative)
}

func getPrefix(file string) string {
	// tar strips the leading '/' if it's there, so we will too
	return strings.TrimLeft(file, "/")
}

func (o *CopyOptions) execute(options *ExecOptions) error {
	if len(options.Namespace) == 0 {
		options.Namespace = o.Namespace
	}

	if len(o.Container) > 0 {
		options.ContainerName = o.Container
	}

	options.Config = o.ClientConfig
	options.PodClient = o.Clientset.Core()

	if err := options.Validate(); err != nil {
		return err
	}

	if err := options.Run(); err != nil {
		return err
	}
	return nil
}