fix(unikontainers): secure container state paths

.github/contributors.yaml

@@ -128,3 +128,6 @@ users:
   OdysseasKalaitsidis:
     name: Odysseas Kalaitsidis
     email: odysseaskalaitsides@gmail.com
+  tagadearpit:
+    name: Arpit Tagade
+    email: 143588157+tagadearpit@users.noreply.github.com

cmd/urunc/delete.go

@@ -17,10 +17,11 @@ package main
 import (
 	"context"
 	"errors"
+	"fmt"
 	"os"
-	"path/filepath"
 	"runtime"
 
+	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli/v3"
 )
@@ -62,11 +63,15 @@ status of "ubuntu01" as "stopped" the following will delete resources held for
 					return ErrEmptyContainerID
 				}
 				rootDir := cmd.String("root")
-				containerDir := filepath.Join(rootDir, containerID)
-				e := os.RemoveAll(containerDir)
+				containerDir, e := securejoin.SecureJoin(rootDir, containerID)
+				if e != nil {
+					return fmt.Errorf("failed to resolve container directory: %w", e)
+				}
+				e = os.RemoveAll(containerDir)
 				if e != nil {
 					logrus.Errorf("remove %s: %v", containerDir, e)
 				}
+
 				if cmd.Bool("force") {
 					return nil
 				}

pkg/unikontainers/path_security_test.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2023-2026, Nubificus LTD
+//
+// 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 unikontainers
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/opencontainers/runtime-spec/specs-go"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetRejectsContainerDirSymlink(t *testing.T) {
+	rootDir := t.TempDir()
+	outsideDir := t.TempDir()
+	bundleDir := t.TempDir()
+
+	spec := &specs.Spec{
+		Version: "1.0.2",
+		Linux:   &specs.Linux{},
+	}
+	specData, err := json.Marshal(spec)
+	require.NoError(t, err)
+	require.NoError(t, os.WriteFile(filepath.Join(bundleDir, configFilename), specData, 0o600))
+
+	state := &specs.State{
+		Version: "1.0.2",
+		ID:      "victim",
+		Bundle:  bundleDir,
+		Annotations: map[string]string{
+			annotType:       "linux",
+			annotHypervisor: "qemu",
+		},
+	}
+	stateData, err := json.Marshal(state)
+	require.NoError(t, err)
+	require.NoError(t, os.WriteFile(filepath.Join(outsideDir, stateFilename), stateData, 0o600))
+
+	require.NoError(t, os.Symlink(outsideDir, filepath.Join(rootDir, state.ID)))
+
+	_, err = Get(state.ID, rootDir)
+	require.ErrorIs(t, err, os.ErrNotExist)
+}

pkg/unikontainers/unikontainers.go

@@ -29,6 +29,7 @@ import (
 	"sync"
 	"syscall"
 
+	securejoin "github.com/cyphar/filepath-securejoin"
 	"github.com/urunc-dev/urunc/pkg/network"
 	"github.com/urunc-dev/urunc/pkg/unikontainers/hypervisors"
 	"github.com/urunc-dev/urunc/pkg/unikontainers/types"
@@ -93,7 +94,10 @@ func New(bundlePath string, containerID string, rootDir string, cfg *UruncConfig
 	confMap := config.Map()
 
 	maps.Copy(confMap, cfg.Map())
-	containerDir := filepath.Join(rootDir, containerID)
+	containerDir, err := securejoin.SecureJoin(rootDir, containerID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to resolve container directory: %w", err)
+	}
 	state := &specs.State{
 		Version:     spec.Version,
 		ID:          containerID,
@@ -114,7 +118,10 @@ func New(bundlePath string, containerID string, rootDir string, cfg *UruncConfig
 // Get retrieves unikernel data from disk to create a Unikontainer object
 func Get(containerID string, rootDir string) (*Unikontainer, error) {
 	u := &Unikontainer{}
-	containerDir := filepath.Join(rootDir, containerID)
+	containerDir, err := securejoin.SecureJoin(rootDir, containerID)
+	if err != nil {
+		return nil, fmt.Errorf("failed to resolve container directory: %w", err)
+	}
 	stateFilePath := filepath.Join(containerDir, stateFilename)
 	state, err := loadUnikontainerState(stateFilePath)
 	if err != nil {