remote copy

Implement `podman-remote cp` and break out the logic from the previously
added `pkg/copy` into it's basic building blocks and move them up into
the `ContainerEngine` interface and `cmd/podman`.

The `--pause` and `--extract` flags are now deprecated and turned into
nops.

Note that this commit is vendoring a non-release version of Buildah to
pull in updates to the copier package.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 251 insertions, 0 deletions

diff --git a/pkg/domain/infra/abi/containers_stat.go b/pkg/domain/infra/abi/containers_stat.go
new file mode 100644
index 000000000..c9610d1b9
--- /dev/null
+++ b/pkg/domain/infra/abi/containers_stat.go
@@ -0,0 +1,251 @@
+package abi
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+
+	buildahCopiah "github.com/containers/buildah/copier"
+	"github.com/containers/podman/v2/libpod"
+	"github.com/containers/podman/v2/pkg/copy"
+	"github.com/containers/podman/v2/pkg/domain/entities"
+	securejoin "github.com/cyphar/filepath-securejoin"
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+)
+
+func (ic *ContainerEngine) containerStat(container *libpod.Container, containerPath string) (*entities.ContainerStatReport, string, string, error) {
+	containerMountPoint, err := container.Mount()
+	if err != nil {
+		return nil, "", "", err
+	}
+
+	// Make sure that "/" copies the *contents* of the mount point and not
+	// the directory.
+	if containerPath == "/" {
+		containerPath += "/."
+	}
+
+	// Now resolve the container's path.  It may hit a volume, it may hit a
+	// bind mount, it may be relative.
+	resolvedRoot, resolvedContainerPath, err := resolveContainerPaths(container, containerMountPoint, containerPath)
+	if err != nil {
+		return nil, "", "", err
+	}
+
+	statInfo, statInfoErr := secureStat(resolvedRoot, resolvedContainerPath)
+	if statInfoErr != nil {
+		// Not all errors from secureStat map to ErrNotExist, so we
+		// have to look into the error string.  Turning it into an
+		// ENOENT let's the API handlers return the correct status code
+		// which is crucuial for the remote client.
+		if os.IsNotExist(err) || strings.Contains(statInfoErr.Error(), "o such file or directory") {
+			statInfoErr = copy.ENOENT
+		}
+		//  If statInfo is nil, there's nothing we can do anymore.  A
+		//  non-nil statInfo may indicate a symlink where we must have
+		//  a closer look.
+		if statInfo == nil {
+			return nil, "", "", statInfoErr
+		}
+	}
+
+	// Now make sure that the info's LinkTarget is relative to the
+	// container's mount.
+	var absContainerPath string
+
+	if statInfo.IsSymlink {
+		// Evaluated symlinks are always relative to the container's mount point.
+		absContainerPath = statInfo.ImmediateTarget
+	} else if strings.HasPrefix(resolvedContainerPath, containerMountPoint) {
+		// If the path is on the container's mount point, strip it off.
+		absContainerPath = strings.TrimPrefix(resolvedContainerPath, containerMountPoint)
+		absContainerPath = filepath.Join("/", absContainerPath)
+	} else {
+		// No symlink and not on the container's mount point, so let's
+		// move it back to the original input.  It must have evaluated
+		// to a volume or bind mount but we cannot return host paths.
+		absContainerPath = containerPath
+	}
+
+	// Now we need to make sure to preseve the base path as specified by
+	// the user.  The `filepath` packages likes to remove trailing slashes
+	// and dots that are crucial to the copy logic.
+	absContainerPath = copy.PreserveBasePath(containerPath, absContainerPath)
+	resolvedContainerPath = copy.PreserveBasePath(containerPath, resolvedContainerPath)
+
+	info := copy.FileInfo{
+		IsDir:      statInfo.IsDir,
+		Name:       filepath.Base(absContainerPath),
+		Size:       statInfo.Size,
+		Mode:       statInfo.Mode,
+		ModTime:    statInfo.ModTime,
+		LinkTarget: absContainerPath,
+	}
+
+	return &entities.ContainerStatReport{FileInfo: info}, resolvedRoot, resolvedContainerPath, statInfoErr
+}
+
+func (ic *ContainerEngine) ContainerStat(ctx context.Context, nameOrID string, containerPath string) (*entities.ContainerStatReport, error) {
+	container, err := ic.Libpod.LookupContainer(nameOrID)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		if err := container.Unmount(false); err != nil {
+			logrus.Errorf("Error unmounting container: %v", err)
+		}
+	}()
+
+	statReport, _, _, err := ic.containerStat(container, containerPath)
+	return statReport, err
+}
+
+// resolveContainerPaths resolves the container's mount point and the container
+// path as specified by the user.  Both may resolve to paths outside of the
+// container's mount point when the container path hits a volume or bind mount.
+//
+// NOTE: We must take volumes and bind mounts into account as, regrettably, we
+// can copy to/from stopped containers.  In that case, the volumes and bind
+// mounts are not present.  For running containers, the runtime (e.g., runc or
+// crun) takes care of these mounts.  For stopped ones, we need to do quite
+// some dance, as done below.
+func resolveContainerPaths(container *libpod.Container, mountPoint string, containerPath string) (string, string, error) {
+	// Let's first make sure we have a path relative to the mount point.
+	pathRelativeToContainerMountPoint := containerPath
+	if !filepath.IsAbs(containerPath) {
+		// If the containerPath is not absolute, it's relative to the
+		// container's working dir.  To be extra careful, let's first
+		// join the working dir with "/", and the add the containerPath
+		// to it.
+		pathRelativeToContainerMountPoint = filepath.Join(filepath.Join("/", container.WorkingDir()), containerPath)
+	}
+	resolvedPathOnTheContainerMountPoint := filepath.Join(mountPoint, pathRelativeToContainerMountPoint)
+	pathRelativeToContainerMountPoint = strings.TrimPrefix(pathRelativeToContainerMountPoint, mountPoint)
+	pathRelativeToContainerMountPoint = filepath.Join("/", pathRelativeToContainerMountPoint)
+
+	// Now we have an "absolute container Path" but not yet resolved on the
+	// host (e.g., "/foo/bar/file.txt").  As mentioned above, we need to
+	// check if "/foo/bar/file.txt" is on a volume or bind mount.  To do
+	// that, we need to walk *down* the paths to the root.  Assuming
+	// volume-1 is mounted to "/foo" and volume-2 is mounted to "/foo/bar",
+	// we must select "/foo/bar".  Once selected, we need to rebase the
+	// remainder (i.e, "/file.txt") on the volume's mount point on the
+	// host.  Same applies to bind mounts.
+
+	searchPath := pathRelativeToContainerMountPoint
+	for {
+		volume, err := findVolume(container, searchPath)
+		if err != nil {
+			return "", "", err
+		}
+		if volume != nil {
+			logrus.Debugf("Container path %q resolved to volume %q on path %q", containerPath, volume.Name(), searchPath)
+			// We found a matching volume for searchPath.  We now
+			// need to first find the relative path of our input
+			// path to the searchPath, and then join it with the
+			// volume's mount point.
+			pathRelativeToVolume := strings.TrimPrefix(pathRelativeToContainerMountPoint, searchPath)
+			absolutePathOnTheVolumeMount, err := securejoin.SecureJoin(volume.MountPoint(), pathRelativeToVolume)
+			if err != nil {
+				return "", "", err
+			}
+			return volume.MountPoint(), absolutePathOnTheVolumeMount, nil
+		}
+
+		if mount := findBindMount(container, searchPath); mount != nil {
+			logrus.Debugf("Container path %q resolved to bind mount %q:%q on path %q", containerPath, mount.Source, mount.Destination, searchPath)
+			// We found a matching bind mount for searchPath.  We
+			// now need to first find the relative path of our
+			// input path to the searchPath, and then join it with
+			// the source of the bind mount.
+			pathRelativeToBindMount := strings.TrimPrefix(pathRelativeToContainerMountPoint, searchPath)
+			absolutePathOnTheBindMount, err := securejoin.SecureJoin(mount.Source, pathRelativeToBindMount)
+			if err != nil {
+				return "", "", err
+			}
+			return mount.Source, absolutePathOnTheBindMount, nil
+
+		}
+
+		if searchPath == "/" {
+			// Cannot go beyond "/", so we're done.
+			break
+		}
+
+		// Walk *down* the path (e.g., "/foo/bar/x" -> "/foo/bar").
+		searchPath = filepath.Dir(searchPath)
+	}
+
+	// No volume, no bind mount but just a normal path on the container.
+	return mountPoint, resolvedPathOnTheContainerMountPoint, nil
+}
+
+// findVolume checks if the specified container path matches a volume inside
+// the container.  It returns a matching volume or nil.
+func findVolume(c *libpod.Container, containerPath string) (*libpod.Volume, error) {
+	runtime := c.Runtime()
+	cleanedContainerPath := filepath.Clean(containerPath)
+	for _, vol := range c.Config().NamedVolumes {
+		if cleanedContainerPath == filepath.Clean(vol.Dest) {
+			return runtime.GetVolume(vol.Name)
+		}
+	}
+	return nil, nil
+}
+
+// findBindMount checks if the specified container path matches a bind mount
+// inside the container.  It returns a matching mount or nil.
+func findBindMount(c *libpod.Container, containerPath string) *specs.Mount {
+	cleanedPath := filepath.Clean(containerPath)
+	for _, m := range c.Config().Spec.Mounts {
+		if m.Type != "bind" {
+			continue
+		}
+		if cleanedPath == filepath.Clean(m.Destination) {
+			mount := m
+			return &mount
+		}
+	}
+	return nil
+}
+
+// secureStat extracts file info for path in a chroot'ed environment in root.
+func secureStat(root string, path string) (*buildahCopiah.StatForItem, error) {
+	var glob string
+	var err error
+
+	// If root and path are equal, then dir must be empty and the glob must
+	// be ".".
+	if filepath.Clean(root) == filepath.Clean(path) {
+		glob = "."
+	} else {
+		glob, err = filepath.Rel(root, path)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	globStats, err := buildahCopiah.Stat(root, "", buildahCopiah.StatOptions{}, []string{glob})
+	if err != nil {
+		return nil, err
+	}
+
+	if len(globStats) != 1 {
+		return nil, errors.Errorf("internal error: secureStat: expected 1 item but got %d", len(globStats))
+	}
+
+	stat, exists := globStats[0].Results[glob] // only one glob passed, so that's okay
+	if !exists {
+		return nil, copy.ENOENT
+	}
+
+	var statErr error
+	if stat.Error != "" {
+		statErr = errors.New(stat.Error)
+	}
+	return stat, statErr
+}