fix(isolation): reject native traversal forms

Author: shixi-li

src/copy-containment.js

@@ -78,26 +78,27 @@ function assertPinnedRoot(root, label, relativePath) {
   }
 }
 
-function validateRelativePath(relativePath) {
+function validateRelativePath(relativePath, pathApi = path) {
   if (typeof relativePath !== 'string' || relativePath.length === 0) {
     throw containmentError(relativePath, 'path must be a non-empty relative string');
   }
   if (relativePath.includes('\0')) {
     throw containmentError(relativePath, 'path contains a null byte');
   }
-  if (path.isAbsolute(relativePath) || path.parse(relativePath).root) {
+  if (pathApi.isAbsolute(relativePath) || pathApi.parse(relativePath).root) {
     throw containmentError(relativePath, 'absolute paths are not allowed');
   }
 
-  const components = relativePath.split(path.sep);
+  const components =
+    pathApi.sep === '\\' ? relativePath.split(/[\\/]/) : relativePath.split(pathApi.sep);
   if (components.some((component) => component === '' || component === '.' || component === '..')) {
     throw containmentError(
       relativePath,
       'empty, current-directory, and traversal components are not allowed'
     );
   }
 
-  return path.normalize(relativePath);
+  return pathApi.normalize(relativePath);
 }
 
 function resolveSourcePath(boundary, relativePath) {

src/isolation-manager.js

@@ -1323,7 +1323,7 @@ class IsolationManager {
       }
     };
 
-    function handleEntry(entry, srcPath, relPath, relativePath, ancestorDirectories) {
+    function handleEntry(entry, relPath, relativePath, ancestorDirectories) {
       if (entry.isSymbolicLink()) {
         const resolvedSourcePath = resolveSourcePath(copyBoundary, relPath);
         const targetStats = fs.statSync(resolvedSourcePath);
@@ -1365,11 +1365,10 @@ class IsolationManager {
         }
 
         const entryName = validateRelativePath(entry.name);
-        const srcPath = path.join(currentSrc, entryName);
         const relPath = relativePath ? path.join(relativePath, entryName) : entryName;
 
         try {
-          handleEntry(entry, srcPath, relPath, relativePath, childAncestors);
+          handleEntry(entry, relPath, relativePath, childAncestors);
         } catch (err) {
           if (shouldIgnoreFsError(err)) {
             continue;

tests/isolation-copy-containment.test.js

@@ -9,6 +9,7 @@ const {
   CopyContainmentError,
   createCopyBoundary,
   resolveCopyPath,
+  validateRelativePath,
 } = require('../src/copy-containment');
 
 function writeFlatFiles(directory, count) {
@@ -50,6 +51,12 @@ describe('isolation copy containment', function () {
     manager = new IsolationManager();
   });
 
+  it('rejects either Windows separator before win32 normalization', function () {
+    for (const unsafePath of ['nested\\..\\..\\escape', 'nested/../../escape']) {
+      assert.throws(() => validateRelativePath(unsafePath, path.win32), isContainmentError);
+    }
+  });
+
   afterEach(function () {
     fs.rmSync(fixtureRoot, { recursive: true, force: true });
   });