fix: block symlink escapes in skills file ops

skills-engine/__tests__/file-ops.test.ts

@@ -4,6 +4,19 @@ import path from 'path';
 import { executeFileOps } from '../file-ops.js';
 import { createTempDir, cleanup } from './test-helpers.js';
 
+function shouldSkipSymlinkTests(err: unknown): boolean {
+  return !!(
+    err &&
+    typeof err === 'object' &&
+    'code' in err &&
+    (
+      (err as { code?: string }).code === 'EPERM' ||
+      (err as { code?: string }).code === 'EACCES' ||
+      (err as { code?: string }).code === 'ENOSYS'
+    )
+  );
+}
+
 describe('file-ops', () => {
   let tmpDir: string;
   const originalCwd = process.cwd();
@@ -90,4 +103,53 @@ describe('file-ops', () => {
     expect(result.success).toBe(false);
     expect(result.errors.length).toBeGreaterThan(0);
   });
+
+  it('move rejects symlink escape to outside project root', () => {
+    const outsideDir = createTempDir();
+
+    try {
+      fs.symlinkSync(outsideDir, path.join(tmpDir, 'linkdir'));
+    } catch (err) {
+      cleanup(outsideDir);
+      if (shouldSkipSymlinkTests(err)) return;
+      throw err;
+    }
+
+    fs.writeFileSync(path.join(tmpDir, 'source.ts'), 'content');
+
+    const result = executeFileOps([
+      { type: 'move', from: 'source.ts', to: 'linkdir/pwned.ts' },
+    ], tmpDir);
+
+    expect(result.success).toBe(false);
+    expect(result.errors.some((e) => e.includes('escapes project root'))).toBe(true);
+    expect(fs.existsSync(path.join(tmpDir, 'source.ts'))).toBe(true);
+    expect(fs.existsSync(path.join(outsideDir, 'pwned.ts'))).toBe(false);
+
+    cleanup(outsideDir);
+  });
+
+  it('delete rejects symlink escape to outside project root', () => {
+    const outsideDir = createTempDir();
+    const outsideFile = path.join(outsideDir, 'victim.ts');
+    fs.writeFileSync(outsideFile, 'secret');
+
+    try {
+      fs.symlinkSync(outsideDir, path.join(tmpDir, 'linkdir'));
+    } catch (err) {
+      cleanup(outsideDir);
+      if (shouldSkipSymlinkTests(err)) return;
+      throw err;
+    }
+
+    const result = executeFileOps([
+      { type: 'delete', path: 'linkdir/victim.ts' },
+    ], tmpDir);
+
+    expect(result.success).toBe(false);
+    expect(result.errors.some((e) => e.includes('escapes project root'))).toBe(true);
+    expect(fs.existsSync(outsideFile)).toBe(true);
+
+    cleanup(outsideDir);
+  });
 });

skills-engine/file-ops.ts

@@ -2,11 +2,65 @@ import fs from 'fs';
 import path from 'path';
 import type { FileOperation, FileOpsResult } from './types.js';
 
+function isWithinRoot(rootPath: string, targetPath: string): boolean {
+  return targetPath === rootPath || targetPath.startsWith(rootPath + path.sep);
+}
+
+function nearestExistingPathOrSymlink(candidateAbsPath: string): string {
+  let current = candidateAbsPath;
+  while (true) {
+    try {
+      fs.lstatSync(current);
+      return current;
+    } catch {
+      const parent = path.dirname(current);
+      if (parent === current) {
+        throw new Error(`Invalid file operation path: "${candidateAbsPath}"`);
+      }
+      current = parent;
+    }
+  }
+}
+
+function resolveRealPathWithSymlinkAwareAnchor(candidateAbsPath: string): string {
+  const anchorPath = nearestExistingPathOrSymlink(candidateAbsPath);
+  const anchorStat = fs.lstatSync(anchorPath);
+  let realAnchor: string;
+
+  if (anchorStat.isSymbolicLink()) {
+    const linkTarget = fs.readlinkSync(anchorPath);
+    const linkResolved = path.resolve(path.dirname(anchorPath), linkTarget);
+    realAnchor = fs.realpathSync(linkResolved);
+  } else {
+    realAnchor = fs.realpathSync(anchorPath);
+  }
+
+  const relativeRemainder = path.relative(anchorPath, candidateAbsPath);
+  return relativeRemainder
+    ? path.resolve(realAnchor, relativeRemainder)
+    : realAnchor;
+}
+
 function safePath(projectRoot: string, relativePath: string): string | null {
-  const resolved = path.resolve(projectRoot, relativePath);
-  if (!resolved.startsWith(projectRoot + path.sep) && resolved !== projectRoot) {
+  if (typeof relativePath !== 'string' || relativePath.trim() === '') {
     return null;
   }
+
+  const root = path.resolve(projectRoot);
+  const resolved = path.resolve(root, relativePath);
+  if (!isWithinRoot(root, resolved)) {
+    return null;
+  }
+  if (resolved === root) {
+    return null;
+  }
+
+  const realRoot = fs.realpathSync(root);
+  const realParent = resolveRealPathWithSymlinkAwareAnchor(path.dirname(resolved));
+  if (!isWithinRoot(realRoot, realParent)) {
+    return null;
+  }
+
   return resolved;
 }