libcontainer: move CleanPath and StripRoot to internal/pathrs

These helpers will be needed for the compatibility code added in future
patches in this series, but because "internal/pathrs" is imported by
"libcontainer/utils" we need to move them so that we can avoid circular
dependencies.

Because the old functions were in a non-internal package it is possible
some downstreams use them, so add some wrappers but mark them as
deprecated.

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

libcontainer/utils/utils.go

@@ -4,11 +4,11 @@ package utils
 import (
 	"encoding/json"
 	"io"
-	"os"
-	"path/filepath"
 	"strings"
 
 	"golang.org/x/sys/unix"
+
+	"github.com/opencontainers/runc/internal/pathrs"
 )
 
 const (
@@ -37,53 +37,6 @@ func WriteJSON(w io.Writer, v any) error {
 	return err
 }
 
-// CleanPath makes a path safe for use with filepath.Join. This is done by not
-// only cleaning the path, but also (if the path is relative) adding a leading
-// '/' and cleaning it (then removing the leading '/'). This ensures that a
-// path resulting from prepending another path will always resolve to lexically
-// be a subdirectory of the prefixed path. This is all done lexically, so paths
-// that include symlinks won't be safe as a result of using CleanPath.
-func CleanPath(path string) string {
-	// Deal with empty strings nicely.
-	if path == "" {
-		return ""
-	}
-
-	// Ensure that all paths are cleaned (especially problematic ones like
-	// "/../../../../../" which can cause lots of issues).
-
-	if filepath.IsAbs(path) {
-		return filepath.Clean(path)
-	}
-
-	// If the path isn't absolute, we need to do more processing to fix paths
-	// such as "../../../../<etc>/some/path". We also shouldn't convert absolute
-	// paths to relative ones.
-	path = filepath.Clean(string(os.PathSeparator) + path)
-	// This can't fail, as (by definition) all paths are relative to root.
-	path, _ = filepath.Rel(string(os.PathSeparator), path)
-
-	return path
-}
-
-// StripRoot returns the passed path, stripping the root path if it was
-// (lexicially) inside it. Note that both passed paths will always be treated
-// as absolute, and the returned path will also always be absolute. In
-// addition, the paths are cleaned before stripping the root.
-func StripRoot(root, path string) string {
-	// Make the paths clean and absolute.
-	root, path = CleanPath("/"+root), CleanPath("/"+path)
-	switch {
-	case path == root:
-		path = "/"
-	case root == "/":
-		// do nothing
-	default:
-		path = strings.TrimPrefix(path, root+"/")
-	}
-	return CleanPath("/" + path)
-}
-
 // SearchLabels searches through a list of key=value pairs for a given key,
 // returning its value, and the binary flag telling whether the key exist.
 func SearchLabels(labels []string, key string) (string, bool) {
@@ -114,3 +67,23 @@ func Annotations(labels []string) (bundle string, userAnnotations map[string]str
 	}
 	return bundle, userAnnotations
 }
+
+// CleanPath makes a path safe for use with filepath.Join. This is done by not
+// only cleaning the path, but also (if the path is relative) adding a leading
+// '/' and cleaning it (then removing the leading '/'). This ensures that a
+// path resulting from prepending another path will always resolve to lexically
+// be a subdirectory of the prefixed path. This is all done lexically, so paths
+// that include symlinks won't be safe as a result of using CleanPath.
+//
+// Deprecated: This function has been moved to internal/pathrs and this wrapper
+// will be removed in runc 1.5.
+var CleanPath = pathrs.LexicallyCleanPath
+
+// StripRoot returns the passed path, stripping the root path if it was
+// (lexicially) inside it. Note that both passed paths will always be treated
+// as absolute, and the returned path will also always be absolute. In
+// addition, the paths are cleaned before stripping the root.
+//
+// Deprecated: This function has been moved to internal/pathrs and this wrapper
+// will be removed in runc 1.5.
+var StripRoot = pathrs.LexicallyStripRoot