daemon/archive.go

package daemon

import (
	"errors"
	"io"
	"os"
	"path/filepath"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/pkg/archive"
	"github.com/docker/docker/pkg/chrootarchive"
	"github.com/docker/docker/pkg/ioutils"
)

// ErrExtractPointNotDirectory is used to convey that the operation to extract
// a tar archive to a directory in a container has failed because the specified
// path does not refer to a directory.
var ErrExtractPointNotDirectory = errors.New("extraction point is not a directory")

// ContainerCopy performs a depracated operation of archiving the resource at
// the specified path in the conatiner identified by the given name.
func (daemon *Daemon) ContainerCopy(name string, res string) (io.ReadCloser, error) {
	container, err := daemon.Get(name)
	if err != nil {
		return nil, err
	}

	if res[0] == '/' {
		res = res[1:]
	}

	return container.Copy(res)
}

// ContainerStatPath stats the filesystem resource at the specified path in the
// container identified by the given name.
func (daemon *Daemon) ContainerStatPath(name string, path string) (stat *types.ContainerPathStat, err error) {
	container, err := daemon.Get(name)
	if err != nil {
		return nil, err
	}

	return container.StatPath(path)
}

// ContainerArchivePath creates an archive of the filesystem resource at the
// specified path in the container identified by the given name. Returns a
// tar archive of the resource and whether it was a directory or a single file.
func (daemon *Daemon) ContainerArchivePath(name string, path string) (content io.ReadCloser, stat *types.ContainerPathStat, err error) {
	container, err := daemon.Get(name)
	if err != nil {
		return nil, nil, err
	}

	return container.ArchivePath(path)
}

// ContainerExtractToDir extracts the given archive to the specified location
// in the filesystem of the container identified by the given name. The given
// path must be of a directory in the container. If it is not, the error will
// be ErrExtractPointNotDirectory. If noOverwriteDirNonDir is true then it will
// be an error if unpacking the given content would cause an existing directory
// to be replaced with a non-directory and vice versa.
func (daemon *Daemon) ContainerExtractToDir(name, path string, noOverwriteDirNonDir bool, content io.Reader) error {
	container, err := daemon.Get(name)
	if err != nil {
		return err
	}

	return container.ExtractToDir(path, noOverwriteDirNonDir, content)
}

// resolvePath resolves the given path in the container to a resource on the
// host. Returns a resolved path (absolute path to the resource on the host),
// the absolute path to the resource relative to the container's rootfs, and
// a error if the path points to outside the container's rootfs.
func (container *Container) resolvePath(path string) (resolvedPath, absPath string, err error) {
	// Consider the given path as an absolute path in the container.
	absPath = archive.PreserveTrailingDotOrSeparator(filepath.Join(string(filepath.Separator), path), path)

	// Split the absPath into its Directory and Base components. We will
	// resolve the dir in the scope of the container then append the base.
	dirPath, basePath := filepath.Split(absPath)

	resolvedDirPath, err := container.GetResourcePath(dirPath)
	if err != nil {
		return "", "", err
	}

	// resolvedDirPath will have been cleaned (no trailing path separators) so
	// we can manually join it with the base path element.
	resolvedPath = resolvedDirPath + string(filepath.Separator) + basePath

	return resolvedPath, absPath, nil
}

// statPath is the unexported version of StatPath. Locks and mounts should
// be aquired before calling this method and the given path should be fully
// resolved to a path on the host corresponding to the given absolute path
// inside the container.
func (container *Container) statPath(resolvedPath, absPath string) (stat *types.ContainerPathStat, err error) {
	lstat, err := os.Lstat(resolvedPath)
	if err != nil {
		return nil, err
	}

	var linkTarget string
	if lstat.Mode()&os.ModeSymlink != 0 {
		// Fully evaluate the symlink in the scope of the container rootfs.
		hostPath, err := container.GetResourcePath(absPath)
		if err != nil {
			return nil, err
		}

		linkTarget, err = filepath.Rel(container.basefs, hostPath)
		if err != nil {
			return nil, err
		}

		// Make it an absolute path.
		linkTarget = filepath.Join(string(filepath.Separator), linkTarget)
	}

	return &types.ContainerPathStat{
		Name:       filepath.Base(absPath),
		Size:       lstat.Size(),
		Mode:       lstat.Mode(),
		Mtime:      lstat.ModTime(),
		LinkTarget: linkTarget,
	}, nil
}

// StatPath stats the filesystem resource at the specified path in this
// container. Returns stat info about the resource.
func (container *Container) StatPath(path string) (stat *types.ContainerPathStat, err error) {
	container.Lock()
	defer container.Unlock()

	if err = container.Mount(); err != nil {
		return nil, err
	}
	defer container.Unmount()

	err = container.mountVolumes()
	defer container.UnmountVolumes(true)
	if err != nil {
		return nil, err
	}

	resolvedPath, absPath, err := container.resolvePath(path)
	if err != nil {
		return nil, err
	}

	return container.statPath(resolvedPath, absPath)
}

// ArchivePath creates an archive of the filesystem resource at the specified
// path in this container. Returns a tar archive of the resource and stat info
// about the resource.
func (container *Container) ArchivePath(path string) (content io.ReadCloser, stat *types.ContainerPathStat, err error) {
	container.Lock()

	defer func() {
		if err != nil {
			// Wait to unlock the container until the archive is fully read
			// (see the ReadCloseWrapper func below) or if there is an error
			// before that occurs.
			container.Unlock()
		}
	}()

	if err = container.Mount(); err != nil {
		return nil, nil, err
	}

	defer func() {
		if err != nil {
			// unmount any volumes
			container.UnmountVolumes(true)
			// unmount the container's rootfs
			container.Unmount()
		}
	}()

	if err = container.mountVolumes(); err != nil {
		return nil, nil, err
	}

	resolvedPath, absPath, err := container.resolvePath(path)
	if err != nil {
		return nil, nil, err
	}

	stat, err = container.statPath(resolvedPath, absPath)
	if err != nil {
		return nil, nil, err
	}

	// We need to rebase the archive entries if the last element of the
	// resolved path was a symlink that was evaluated and is now different
	// than the requested path. For example, if the given path was "/foo/bar/",
	// but it resolved to "/var/lib/docker/containers/{id}/foo/baz/", we want
	// to ensure that the archive entries start with "bar" and not "baz". This
	// also catches the case when the root directory of the container is
	// requested: we want the archive entries to start with "/" and not the
	// container ID.
	data, err := archive.TarResourceRebase(resolvedPath, filepath.Base(absPath))
	if err != nil {
		return nil, nil, err
	}

	content = ioutils.NewReadCloserWrapper(data, func() error {
		err := data.Close()
		container.UnmountVolumes(true)
		container.Unmount()
		container.Unlock()
		return err
	})

	container.LogEvent("archive-path")

	return content, stat, nil
}

// ExtractToDir extracts the given tar archive to the specified location in the
// filesystem of this container. The given path must be of a directory in the
// container. If it is not, the error will be ErrExtractPointNotDirectory. If
// noOverwriteDirNonDir is true then it will be an error if unpacking the
// given content would cause an existing directory to be replaced with a non-
// directory and vice versa.
func (container *Container) ExtractToDir(path string, noOverwriteDirNonDir bool, content io.Reader) (err error) {
	container.Lock()
	defer container.Unlock()

	if err = container.Mount(); err != nil {
		return err
	}
	defer container.Unmount()

	err = container.mountVolumes()
	defer container.UnmountVolumes(true)
	if err != nil {
		return err
	}

	// The destination path needs to be resolved to a host path, with all
	// symbolic links followed in the scope of the container's rootfs. Note
	// that we do not use `container.resolvePath(path)` here because we need
	// to also evaluate the last path element if it is a symlink. This is so
	// that you can extract an archive to a symlink that points to a directory.

	// Consider the given path as an absolute path in the container.
	absPath := archive.PreserveTrailingDotOrSeparator(filepath.Join(string(filepath.Separator), path), path)

	// This will evaluate the last path element if it is a symlink.
	resolvedPath, err := container.GetResourcePath(absPath)
	if err != nil {
		return err
	}

	stat, err := os.Lstat(resolvedPath)
	if err != nil {
		return err
	}

	if !stat.IsDir() {
		return ErrExtractPointNotDirectory
	}

	// Need to check if the path is in a volume. If it is, it cannot be in a
	// read-only volume. If it is not in a volume, the container cannot be
	// configured with a read-only rootfs.

	// Use the resolved path relative to the container rootfs as the new
	// absPath. This way we fully follow any symlinks in a volume that may
	// lead back outside the volume.
	baseRel, err := filepath.Rel(container.basefs, resolvedPath)
	if err != nil {
		return err
	}
	// Make it an absolute path.
	absPath = filepath.Join(string(filepath.Separator), baseRel)

	toVolume, err := checkIfPathIsInAVolume(container, absPath)
	if err != nil {
		return err
	}

	if !toVolume && container.hostConfig.ReadonlyRootfs {
		return ErrContainerRootfsReadonly
	}

	options := &archive.TarOptions{
		ChownOpts: &archive.TarChownOptions{
			UID: 0, GID: 0, // TODO: use config.User? Remap to userns root?
		},
		NoOverwriteDirNonDir: noOverwriteDirNonDir,
	}

	if err := chrootarchive.Untar(content, resolvedPath, options); err != nil {
		return err
	}

	container.LogEvent("extract-to-dir")

	return nil
}

// checkIfPathIsInAVolume checks if the path is in a volume. If it is, it
// cannot be in a read-only volume. If it  is not in a volume, the container
// cannot be configured with a read-only rootfs.
func checkIfPathIsInAVolume(container *Container, absPath string) (bool, error) {
	var toVolume bool
	for _, mnt := range container.MountPoints {
		if toVolume = mnt.hasResource(absPath); toVolume {
			if mnt.RW {
				break
			}
			return false, ErrVolumeReadonly
		}
	}
	return toVolume, nil
}