Move ContainerRoot type to oci package

Thsi change moves the ContainerRoot type to the oci package and updates
state.GetContainerRootDirPath to return a variable of type ContainerRoot. This
enabled better reuse between hooks.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/oci/container-root.go

@@ -0,0 +1,77 @@
+/**
+# SPDX-FileCopyrightText: Copyright (c) 2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# 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 oci
+
+import (
+	"os"
+	"path/filepath"
+
+	"github.com/moby/sys/symlink"
+)
+
+// A ContainerRoot represents the root directory of a container's filesystem.
+type ContainerRoot string
+
+// GlobFiles matches the specified pattern in the container root.
+// The files that match must be regular files. Symlinks and directories are ignored.
+func (r ContainerRoot) GlobFiles(pattern string) ([]string, error) {
+	patternPath, err := r.Resolve(pattern)
+	if err != nil {
+		return nil, err
+	}
+	matches, err := filepath.Glob(patternPath)
+	if err != nil {
+		return nil, err
+	}
+	var files []string
+	for _, match := range matches {
+		info, err := os.Lstat(match)
+		if err != nil {
+			return nil, err
+		}
+		// Ignore symlinks.
+		if info.Mode()&os.ModeSymlink != 0 {
+			continue
+		}
+		// Ignore directories.
+		if info.IsDir() {
+			continue
+		}
+		files = append(files, match)
+	}
+	return files, nil
+}
+
+// HasPath checks whether the specified path exists in the root.
+func (r ContainerRoot) HasPath(path string) bool {
+	resolved, err := r.Resolve(path)
+	if err != nil {
+		return false
+	}
+	if _, err := os.Stat(resolved); err != nil && os.IsNotExist(err) {
+		return false
+	}
+	return true
+}
+
+// Resolve returns the absolute path including root path.
+// Symlinks are resolved, but are guaranteed to resolve in the root.
+func (r ContainerRoot) Resolve(path string) (string, error) {
+	absolute := filepath.Clean(filepath.Join(string(r), path))
+	return symlink.FollowSymlinkInScope(absolute, string(r))
+}

internal/oci/state.go

@@ -72,9 +72,11 @@ func (s *State) LoadSpec() (*specs.Spec, error) {
 	return spec, nil
 }
 
-// GetContainerRoot returns the root for the container from the associated spec. If the spec is not yet loaded, it is
-// loaded and cached.
-func (s *State) GetContainerRoot() (string, error) {
+// GetContainerRootDirPath returns the root for the container from the associated spec.
+// If the spec is not yet loaded, it is loaded and cached.
+// The container root directory is the absolute path to the directory containing the root
+// of the container filesystem on the host.
+func (s *State) GetContainerRootDirPath() (ContainerRoot, error) {
 	spec, err := s.LoadSpec()
 	if err != nil {
 		return "", err
@@ -85,9 +87,9 @@ func (s *State) GetContainerRoot() (string, error) {
 		containerRoot = spec.Root.Path
 	}
 
-	if filepath.IsAbs(containerRoot) {
-		return containerRoot, nil
+	if !filepath.IsAbs(containerRoot) {
+		containerRoot = filepath.Join(s.Bundle, containerRoot)
 	}
 
-	return filepath.Join(s.Bundle, containerRoot), nil
+	return ContainerRoot(containerRoot), nil
 }