path-validation.test.ts•41.4 kB
import { describe, it, expect, beforeEach, afterEach } from 'vitest';
import * as path from 'path';
import * as fs from 'fs/promises';
import * as os from 'os';
import { isPathWithinAllowedDirectories } from '../path-validation.js';
/**
* Check if the current environment supports symlink creation
*/
async function checkSymlinkSupport(): Promise<boolean> {
const testDir = await fs.mkdtemp(path.join(os.tmpdir(), 'symlink-test-'));
try {
const targetFile = path.join(testDir, 'target.txt');
const linkFile = path.join(testDir, 'link.txt');
await fs.writeFile(targetFile, 'test');
await fs.symlink(targetFile, linkFile);
// If we get here, symlinks are supported
return true;
} catch (error) {
// EPERM indicates no symlink permissions
if ((error as NodeJS.ErrnoException).code === 'EPERM') {
return false;
}
// Other errors might indicate a real problem
throw error;
} finally {
await fs.rm(testDir, { recursive: true, force: true });
}
}
// Global variable to store symlink support status
let symlinkSupported: boolean | null = null;
/**
* Get cached symlink support status, checking once per test run
*/
async function getSymlinkSupport(): Promise<boolean> {
if (symlinkSupported === null) {
symlinkSupported = await checkSymlinkSupport();
if (!symlinkSupported) {
console.log('\n⚠️ Symlink tests will be skipped - symlink creation not supported in this environment');
console.log(' On Windows, enable Developer Mode or run as Administrator to enable symlink tests');
}
}
return symlinkSupported;
}
describe('Path Validation', () => {
it('allows exact directory match', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/project', allowed)).toBe(true);
});
it('allows subdirectories', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/project/src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/src/index.js', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/deeply/nested/file.txt', allowed)).toBe(true);
});
it('blocks similar directory names (prefix vulnerability)', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/project2', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project_backup', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project-old', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/projectile', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project.bak', allowed)).toBe(false);
});
it('blocks paths outside allowed directories', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/other', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/etc/passwd', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/', allowed)).toBe(false);
});
it('handles multiple allowed directories', () => {
const allowed = ['/home/user/project1', '/home/user/project2'];
expect(isPathWithinAllowedDirectories('/home/user/project1/src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project2/src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project3', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project1_backup', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project2-old', allowed)).toBe(false);
});
it('blocks parent and sibling directories', () => {
const allowed = ['/test/allowed'];
// Parent directory
expect(isPathWithinAllowedDirectories('/test', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/', allowed)).toBe(false);
// Sibling with common prefix
expect(isPathWithinAllowedDirectories('/test/allowed_sibling', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/test/allowed2', allowed)).toBe(false);
});
it('handles paths with special characters', () => {
const allowed = ['/home/user/my-project (v2)'];
expect(isPathWithinAllowedDirectories('/home/user/my-project (v2)', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/my-project (v2)/src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/my-project (v2)_backup', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/my-project', allowed)).toBe(false);
});
describe('Input validation', () => {
it('rejects empty inputs', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project', [])).toBe(false);
});
it('handles trailing separators correctly', () => {
const allowed = ['/home/user/project'];
// Path with trailing separator should still match
expect(isPathWithinAllowedDirectories('/home/user/project/', allowed)).toBe(true);
// Allowed directory with trailing separator
const allowedWithSep = ['/home/user/project/'];
expect(isPathWithinAllowedDirectories('/home/user/project', allowedWithSep)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/', allowedWithSep)).toBe(true);
// Should still block similar names with or without trailing separators
expect(isPathWithinAllowedDirectories('/home/user/project2', allowedWithSep)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project2', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project2/', allowed)).toBe(false);
});
it('skips empty directory entries in allowed list', () => {
const allowed = ['', '/home/user/project', ''];
expect(isPathWithinAllowedDirectories('/home/user/project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/src', allowed)).toBe(true);
// Should still validate properly with empty entries
expect(isPathWithinAllowedDirectories('/home/user/other', allowed)).toBe(false);
});
it('handles Windows paths with trailing separators', () => {
if (path.sep === '\\') {
const allowed = ['C:\\Users\\project'];
// Path with trailing separator
expect(isPathWithinAllowedDirectories('C:\\Users\\project\\', allowed)).toBe(true);
// Allowed with trailing separator
const allowedWithSep = ['C:\\Users\\project\\'];
expect(isPathWithinAllowedDirectories('C:\\Users\\project', allowedWithSep)).toBe(true);
expect(isPathWithinAllowedDirectories('C:\\Users\\project\\', allowedWithSep)).toBe(true);
// Should still block similar names
expect(isPathWithinAllowedDirectories('C:\\Users\\project2\\', allowed)).toBe(false);
}
});
});
describe('Error handling', () => {
it('normalizes relative paths to absolute', () => {
const allowed = [process.cwd()];
// Relative paths get normalized to absolute paths based on cwd
expect(isPathWithinAllowedDirectories('relative/path', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('./file', allowed)).toBe(true);
// Parent directory references that escape allowed directory
const parentAllowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('../parent', parentAllowed)).toBe(false);
});
it('returns false for relative paths in allowed directories', () => {
const badAllowed = ['relative/path', '/some/other/absolute/path'];
// Relative paths in allowed dirs are normalized to absolute based on cwd
// The normalized 'relative/path' won't match our test path
expect(isPathWithinAllowedDirectories('/some/other/absolute/path/file', badAllowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/absolute/path/file', badAllowed)).toBe(false);
});
it('handles null and undefined inputs gracefully', () => {
const allowed = ['/home/user/project'];
// Should return false, not crash
expect(isPathWithinAllowedDirectories(null as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories(undefined as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/path', null as any)).toBe(false);
expect(isPathWithinAllowedDirectories('/path', undefined as any)).toBe(false);
});
});
describe('Unicode and special characters', () => {
it('handles unicode characters in paths', () => {
const allowed = ['/home/user/café'];
expect(isPathWithinAllowedDirectories('/home/user/café', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/café/file', allowed)).toBe(true);
// Different unicode representation won't match (not normalized)
const decomposed = '/home/user/cafe\u0301'; // e + combining accent
expect(isPathWithinAllowedDirectories(decomposed, allowed)).toBe(false);
});
it('handles paths with spaces correctly', () => {
const allowed = ['/home/user/my project'];
expect(isPathWithinAllowedDirectories('/home/user/my project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/my project/file', allowed)).toBe(true);
// Partial matches should fail
expect(isPathWithinAllowedDirectories('/home/user/my', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/my proj', allowed)).toBe(false);
});
});
describe('Overlapping allowed directories', () => {
it('handles nested allowed directories correctly', () => {
const allowed = ['/home', '/home/user', '/home/user/project'];
// All paths under /home are allowed
expect(isPathWithinAllowedDirectories('/home/anything', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/anything', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/anything', allowed)).toBe(true);
// First match wins (most permissive)
expect(isPathWithinAllowedDirectories('/home/other/deep/path', allowed)).toBe(true);
});
it('handles root directory as allowed', () => {
const allowed = ['/'];
// Everything is allowed under root (dangerous configuration)
expect(isPathWithinAllowedDirectories('/', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/any/path', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/etc/passwd', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/secret', allowed)).toBe(true);
// But only on the same filesystem root
if (path.sep === '\\') {
expect(isPathWithinAllowedDirectories('D:\\other', ['/'])).toBe(false);
}
});
});
describe('Cross-platform behavior', () => {
it('handles Windows-style paths on Windows', () => {
if (path.sep === '\\') {
const allowed = ['C:\\Users\\project'];
expect(isPathWithinAllowedDirectories('C:\\Users\\project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('C:\\Users\\project\\src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('C:\\Users\\project2', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('C:\\Users\\project_backup', allowed)).toBe(false);
}
});
it('handles Unix-style paths on Unix', () => {
if (path.sep === '/') {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project2', allowed)).toBe(false);
}
});
});
describe('Validation Tests - Path Traversal', () => {
it('blocks path traversal attempts', () => {
const allowed = ['/home/user/project'];
// Basic traversal attempts
expect(isPathWithinAllowedDirectories('/home/user/project/../../../etc/passwd', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/../../other', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/../project2', allowed)).toBe(false);
// Mixed traversal with valid segments
expect(isPathWithinAllowedDirectories('/home/user/project/src/../../project2', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/./../../other', allowed)).toBe(false);
// Multiple traversal sequences
expect(isPathWithinAllowedDirectories('/home/user/project/../project/../../../etc', allowed)).toBe(false);
});
it('blocks traversal in allowed directories', () => {
const allowed = ['/home/user/project/../safe'];
// The allowed directory itself should be normalized and safe
expect(isPathWithinAllowedDirectories('/home/user/safe/file', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/file', allowed)).toBe(false);
});
it('handles complex traversal patterns', () => {
const allowed = ['/home/user/project'];
// Double dots in filenames (not traversal) - these normalize to paths within allowed dir
expect(isPathWithinAllowedDirectories('/home/user/project/..test', allowed)).toBe(true); // Not traversal
expect(isPathWithinAllowedDirectories('/home/user/project/test..', allowed)).toBe(true); // Not traversal
expect(isPathWithinAllowedDirectories('/home/user/project/te..st', allowed)).toBe(true); // Not traversal
// Actual traversal
expect(isPathWithinAllowedDirectories('/home/user/project/../test', allowed)).toBe(false); // Is traversal - goes to /home/user/test
// Edge case: /home/user/project/.. normalizes to /home/user (parent dir)
expect(isPathWithinAllowedDirectories('/home/user/project/..', allowed)).toBe(false); // Goes to parent
});
});
describe('Validation Tests - Null Bytes', () => {
it('rejects paths with null bytes', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories('/home/user/project\x00/etc/passwd', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/test\x00.txt', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('\x00/home/user/project', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/\x00', allowed)).toBe(false);
});
it('rejects allowed directories with null bytes', () => {
const allowed = ['/home/user/project\x00'];
expect(isPathWithinAllowedDirectories('/home/user/project', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project/file', allowed)).toBe(false);
});
});
describe('Validation Tests - Special Characters', () => {
it('allows percent signs in filenames', () => {
const allowed = ['/home/user/project'];
// Percent is a valid filename character
expect(isPathWithinAllowedDirectories('/home/user/project/report_50%.pdf', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/Q1_25%_growth', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/%41', allowed)).toBe(true); // File named %41
// URL encoding is NOT decoded by path.normalize, so these are just odd filenames
expect(isPathWithinAllowedDirectories('/home/user/project/%2e%2e', allowed)).toBe(true); // File named "%2e%2e"
expect(isPathWithinAllowedDirectories('/home/user/project/file%20name', allowed)).toBe(true); // File with %20 in name
});
it('handles percent signs in allowed directories', () => {
const allowed = ['/home/user/project%20files'];
// This is a directory literally named "project%20files"
expect(isPathWithinAllowedDirectories('/home/user/project%20files/test', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project files/test', allowed)).toBe(false); // Different dir
});
});
describe('Path Normalization', () => {
it('normalizes paths before comparison', () => {
const allowed = ['/home/user/project'];
// Trailing slashes
expect(isPathWithinAllowedDirectories('/home/user/project/', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project//', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project///', allowed)).toBe(true);
// Current directory references
expect(isPathWithinAllowedDirectories('/home/user/project/./src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/./project/src', allowed)).toBe(true);
// Multiple slashes
expect(isPathWithinAllowedDirectories('/home/user/project//src//file', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home//user//project//src', allowed)).toBe(true);
// Should still block outside paths
expect(isPathWithinAllowedDirectories('/home/user//project2', allowed)).toBe(false);
});
it('handles mixed separators correctly', () => {
if (path.sep === '\\') {
const allowed = ['C:\\Users\\project'];
// Mixed separators should be normalized
expect(isPathWithinAllowedDirectories('C:/Users/project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('C:\\Users/project\\src', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('C:/Users\\project/src', allowed)).toBe(true);
}
});
});
describe('Edge Cases', () => {
it('rejects non-string inputs safely', () => {
const allowed = ['/home/user/project'];
expect(isPathWithinAllowedDirectories(123 as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories({} as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories([] as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories(null as any, allowed)).toBe(false);
expect(isPathWithinAllowedDirectories(undefined as any, allowed)).toBe(false);
// Non-string in allowed directories
expect(isPathWithinAllowedDirectories('/home/user/project', [123 as any])).toBe(false);
expect(isPathWithinAllowedDirectories('/home/user/project', [{} as any])).toBe(false);
});
it('handles very long paths', () => {
const allowed = ['/home/user/project'];
// Create a very long path that's still valid
const longSubPath = 'a/'.repeat(1000) + 'file.txt';
expect(isPathWithinAllowedDirectories(`/home/user/project/${longSubPath}`, allowed)).toBe(true);
// Very long path that escapes
const escapePath = 'a/'.repeat(1000) + '../'.repeat(1001) + 'etc/passwd';
expect(isPathWithinAllowedDirectories(`/home/user/project/${escapePath}`, allowed)).toBe(false);
});
});
describe('Additional Coverage', () => {
it('handles allowed directories with traversal that normalizes safely', () => {
// These allowed dirs contain traversal but normalize to valid paths
const allowed = ['/home/user/../user/project'];
// Should normalize to /home/user/project and work correctly
expect(isPathWithinAllowedDirectories('/home/user/project/file', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/other', allowed)).toBe(false);
});
it('handles symbolic dots in filenames', () => {
const allowed = ['/home/user/project'];
// Single and double dots as actual filenames (not traversal)
expect(isPathWithinAllowedDirectories('/home/user/project/.', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('/home/user/project/..', allowed)).toBe(false); // This normalizes to parent
expect(isPathWithinAllowedDirectories('/home/user/project/...', allowed)).toBe(true); // Three dots is a valid filename
expect(isPathWithinAllowedDirectories('/home/user/project/....', allowed)).toBe(true); // Four dots is a valid filename
});
it('handles UNC paths on Windows', () => {
if (path.sep === '\\') {
const allowed = ['\\\\server\\share\\project'];
expect(isPathWithinAllowedDirectories('\\\\server\\share\\project', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('\\\\server\\share\\project\\file', allowed)).toBe(true);
expect(isPathWithinAllowedDirectories('\\\\server\\share\\other', allowed)).toBe(false);
expect(isPathWithinAllowedDirectories('\\\\other\\share\\project', allowed)).toBe(false);
}
});
});
describe('Symlink Tests', () => {
let testDir: string;
let allowedDir: string;
let forbiddenDir: string;
beforeEach(async () => {
testDir = await fs.mkdtemp(path.join(os.tmpdir(), 'fs-error-test-'));
allowedDir = path.join(testDir, 'allowed');
forbiddenDir = path.join(testDir, 'forbidden');
await fs.mkdir(allowedDir, { recursive: true });
await fs.mkdir(forbiddenDir, { recursive: true });
});
afterEach(async () => {
await fs.rm(testDir, { recursive: true, force: true });
});
it('validates symlink handling', async () => {
// Test with symlinks
try {
const linkPath = path.join(allowedDir, 'bad-link');
const targetPath = path.join(forbiddenDir, 'target.txt');
await fs.writeFile(targetPath, 'content');
await fs.symlink(targetPath, linkPath);
// In real implementation, this would throw with the resolved path
const realPath = await fs.realpath(linkPath);
const allowed = [allowedDir];
// Symlink target should be outside allowed directory
expect(isPathWithinAllowedDirectories(realPath, allowed)).toBe(false);
} catch (error) {
// Skip if no symlink permissions
}
});
it('handles non-existent paths correctly', async () => {
const newFilePath = path.join(allowedDir, 'subdir', 'newfile.txt');
// Parent directory doesn't exist
try {
await fs.access(newFilePath);
} catch (error) {
expect((error as NodeJS.ErrnoException).code).toBe('ENOENT');
}
// After creating parent, validation should work
await fs.mkdir(path.dirname(newFilePath), { recursive: true });
const allowed = [allowedDir];
expect(isPathWithinAllowedDirectories(newFilePath, allowed)).toBe(true);
});
// Test path resolution consistency for symlinked files
it('validates symlinked files consistently between path and resolved forms', async () => {
try {
// Setup: Create target file in forbidden area
const targetFile = path.join(forbiddenDir, 'target.txt');
await fs.writeFile(targetFile, 'TARGET_CONTENT');
// Create symlink inside allowed directory pointing to forbidden file
const symlinkPath = path.join(allowedDir, 'link-to-target.txt');
await fs.symlink(targetFile, symlinkPath);
// The symlink path itself passes validation (looks like it's in allowed dir)
expect(isPathWithinAllowedDirectories(symlinkPath, [allowedDir])).toBe(true);
// But the resolved path should fail validation
const resolvedPath = await fs.realpath(symlinkPath);
expect(isPathWithinAllowedDirectories(resolvedPath, [allowedDir])).toBe(false);
// Verify the resolved path goes to the forbidden location (normalize both paths for macOS temp dirs)
expect(await fs.realpath(resolvedPath)).toBe(await fs.realpath(targetFile));
} catch (error) {
// Skip if no symlink permissions on the system
if ((error as NodeJS.ErrnoException).code !== 'EPERM') {
throw error;
}
}
});
// Test allowed directory resolution behavior
it('validates paths correctly when allowed directory is resolved from symlink', async () => {
try {
// Setup: Create the actual target directory with content
const actualTargetDir = path.join(testDir, 'actual-target');
await fs.mkdir(actualTargetDir, { recursive: true });
const targetFile = path.join(actualTargetDir, 'file.txt');
await fs.writeFile(targetFile, 'FILE_CONTENT');
// Setup: Create symlink directory that points to target
const symlinkDir = path.join(testDir, 'symlink-dir');
await fs.symlink(actualTargetDir, symlinkDir);
// Simulate resolved allowed directory (what the server startup should do)
const resolvedAllowedDir = await fs.realpath(symlinkDir);
const resolvedTargetDir = await fs.realpath(actualTargetDir);
expect(resolvedAllowedDir).toBe(resolvedTargetDir);
// Test 1: File access through original symlink path should pass validation with resolved allowed dir
const fileViaSymlink = path.join(symlinkDir, 'file.txt');
const resolvedFile = await fs.realpath(fileViaSymlink);
expect(isPathWithinAllowedDirectories(resolvedFile, [resolvedAllowedDir])).toBe(true);
// Test 2: File access through resolved path should also pass validation
const fileViaResolved = path.join(resolvedTargetDir, 'file.txt');
expect(isPathWithinAllowedDirectories(fileViaResolved, [resolvedAllowedDir])).toBe(true);
// Test 3: Demonstrate inconsistent behavior with unresolved allowed directories
// If allowed dirs were not resolved (storing symlink paths instead):
const unresolvedAllowedDirs = [symlinkDir];
// This validation would incorrectly fail for the same content:
expect(isPathWithinAllowedDirectories(resolvedFile, unresolvedAllowedDirs)).toBe(false);
} catch (error) {
// Skip if no symlink permissions on the system
if ((error as NodeJS.ErrnoException).code !== 'EPERM') {
throw error;
}
}
});
it('resolves nested symlink chains completely', async () => {
try {
// Setup: Create target file in forbidden area
const actualTarget = path.join(forbiddenDir, 'target-file.txt');
await fs.writeFile(actualTarget, 'FINAL_CONTENT');
// Create chain of symlinks: allowedFile -> link2 -> link1 -> actualTarget
const link1 = path.join(testDir, 'intermediate-link1');
const link2 = path.join(testDir, 'intermediate-link2');
const allowedFile = path.join(allowedDir, 'seemingly-safe-file');
await fs.symlink(actualTarget, link1);
await fs.symlink(link1, link2);
await fs.symlink(link2, allowedFile);
// The allowed file path passes basic validation
expect(isPathWithinAllowedDirectories(allowedFile, [allowedDir])).toBe(true);
// But complete resolution reveals the forbidden target
const fullyResolvedPath = await fs.realpath(allowedFile);
expect(isPathWithinAllowedDirectories(fullyResolvedPath, [allowedDir])).toBe(false);
expect(await fs.realpath(fullyResolvedPath)).toBe(await fs.realpath(actualTarget));
} catch (error) {
// Skip if no symlink permissions on the system
if ((error as NodeJS.ErrnoException).code !== 'EPERM') {
throw error;
}
}
});
});
describe('Path Validation Race Condition Tests', () => {
let testDir: string;
let allowedDir: string;
let forbiddenDir: string;
let targetFile: string;
let testPath: string;
beforeEach(async () => {
testDir = await fs.mkdtemp(path.join(os.tmpdir(), 'race-test-'));
allowedDir = path.join(testDir, 'allowed');
forbiddenDir = path.join(testDir, 'outside');
targetFile = path.join(forbiddenDir, 'target.txt');
testPath = path.join(allowedDir, 'test.txt');
await fs.mkdir(allowedDir, { recursive: true });
await fs.mkdir(forbiddenDir, { recursive: true });
await fs.writeFile(targetFile, 'ORIGINAL CONTENT', 'utf-8');
});
afterEach(async () => {
await fs.rm(testDir, { recursive: true, force: true });
});
it('validates non-existent file paths based on parent directory', async () => {
const allowed = [allowedDir];
expect(isPathWithinAllowedDirectories(testPath, allowed)).toBe(true);
await expect(fs.access(testPath)).rejects.toThrow();
const parentDir = path.dirname(testPath);
expect(isPathWithinAllowedDirectories(parentDir, allowed)).toBe(true);
});
it('demonstrates symlink race condition allows writing outside allowed directories', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping symlink race condition test - symlinks not supported');
return;
}
const allowed = [allowedDir];
await expect(fs.access(testPath)).rejects.toThrow();
expect(isPathWithinAllowedDirectories(testPath, allowed)).toBe(true);
await fs.symlink(targetFile, testPath);
await fs.writeFile(testPath, 'MODIFIED CONTENT', 'utf-8');
const targetContent = await fs.readFile(targetFile, 'utf-8');
expect(targetContent).toBe('MODIFIED CONTENT');
const resolvedPath = await fs.realpath(testPath);
expect(isPathWithinAllowedDirectories(resolvedPath, allowed)).toBe(false);
});
it('shows timing differences between validation approaches', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping timing validation test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const validation1 = isPathWithinAllowedDirectories(testPath, allowed);
expect(validation1).toBe(true);
await fs.symlink(targetFile, testPath);
const resolvedPath = await fs.realpath(testPath);
const validation2 = isPathWithinAllowedDirectories(resolvedPath, allowed);
expect(validation2).toBe(false);
expect(validation1).not.toBe(validation2);
});
it('validates directory creation timing', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping directory creation timing test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const testDir = path.join(allowedDir, 'newdir');
expect(isPathWithinAllowedDirectories(testDir, allowed)).toBe(true);
await fs.symlink(forbiddenDir, testDir);
expect(isPathWithinAllowedDirectories(testDir, allowed)).toBe(true);
const resolved = await fs.realpath(testDir);
expect(isPathWithinAllowedDirectories(resolved, allowed)).toBe(false);
});
it('demonstrates exclusive file creation behavior', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping exclusive file creation test - symlinks not supported');
return;
}
const allowed = [allowedDir];
await fs.symlink(targetFile, testPath);
await expect(fs.open(testPath, 'wx')).rejects.toThrow(/EEXIST/);
await fs.writeFile(testPath, 'NEW CONTENT', 'utf-8');
const targetContent = await fs.readFile(targetFile, 'utf-8');
expect(targetContent).toBe('NEW CONTENT');
});
it('should use resolved parent paths for non-existent files', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping resolved parent paths test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const symlinkDir = path.join(allowedDir, 'link');
await fs.symlink(forbiddenDir, symlinkDir);
const fileThroughSymlink = path.join(symlinkDir, 'newfile.txt');
expect(fileThroughSymlink.startsWith(allowedDir)).toBe(true);
const parentDir = path.dirname(fileThroughSymlink);
const resolvedParent = await fs.realpath(parentDir);
expect(isPathWithinAllowedDirectories(resolvedParent, allowed)).toBe(false);
const expectedSafePath = path.join(resolvedParent, path.basename(fileThroughSymlink));
expect(isPathWithinAllowedDirectories(expectedSafePath, allowed)).toBe(false);
});
it('demonstrates parent directory symlink traversal', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping parent directory symlink traversal test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const deepPath = path.join(allowedDir, 'sub1', 'sub2', 'file.txt');
expect(isPathWithinAllowedDirectories(deepPath, allowed)).toBe(true);
const sub1Path = path.join(allowedDir, 'sub1');
await fs.symlink(forbiddenDir, sub1Path);
await fs.mkdir(path.join(sub1Path, 'sub2'), { recursive: true });
await fs.writeFile(deepPath, 'CONTENT', 'utf-8');
const realPath = await fs.realpath(deepPath);
const realAllowedDir = await fs.realpath(allowedDir);
const realForbiddenDir = await fs.realpath(forbiddenDir);
expect(realPath.startsWith(realAllowedDir)).toBe(false);
expect(realPath.startsWith(realForbiddenDir)).toBe(true);
});
it('should prevent race condition between validatePath and file operation', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping race condition prevention test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const racePath = path.join(allowedDir, 'race-file.txt');
const targetFile = path.join(forbiddenDir, 'target.txt');
await fs.writeFile(targetFile, 'ORIGINAL CONTENT', 'utf-8');
// Path validation would pass (file doesn't exist, parent is in allowed dir)
expect(await fs.access(racePath).then(() => false).catch(() => true)).toBe(true);
expect(isPathWithinAllowedDirectories(racePath, allowed)).toBe(true);
// Race condition: symlink created after validation but before write
await fs.symlink(targetFile, racePath);
// With exclusive write flag, write should fail on symlink
await expect(
fs.writeFile(racePath, 'NEW CONTENT', { encoding: 'utf-8', flag: 'wx' })
).rejects.toThrow(/EEXIST/);
// Verify content unchanged
const targetContent = await fs.readFile(targetFile, 'utf-8');
expect(targetContent).toBe('ORIGINAL CONTENT');
// The symlink exists but write was blocked
const actualWritePath = await fs.realpath(racePath);
expect(actualWritePath).toBe(await fs.realpath(targetFile));
expect(isPathWithinAllowedDirectories(actualWritePath, allowed)).toBe(false);
});
it('should allow overwrites to legitimate files within allowed directories', async () => {
const allowed = [allowedDir];
const legitFile = path.join(allowedDir, 'legit-file.txt');
// Create a legitimate file
await fs.writeFile(legitFile, 'ORIGINAL', 'utf-8');
// Opening with w should work for legitimate files
const fd = await fs.open(legitFile, 'w');
try {
await fd.write('UPDATED', 0, 'utf-8');
} finally {
await fd.close();
}
const content = await fs.readFile(legitFile, 'utf-8');
expect(content).toBe('UPDATED');
});
it('should handle symlinks that point within allowed directories', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping symlinks within allowed directories test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const targetFile = path.join(allowedDir, 'target.txt');
const symlinkPath = path.join(allowedDir, 'symlink.txt');
// Create target file within allowed directory
await fs.writeFile(targetFile, 'TARGET CONTENT', 'utf-8');
// Create symlink pointing to allowed file
await fs.symlink(targetFile, symlinkPath);
// Opening symlink with w follows it to the target
const fd = await fs.open(symlinkPath, 'w');
try {
await fd.write('UPDATED VIA SYMLINK', 0, 'utf-8');
} finally {
await fd.close();
}
// Both symlink and target should show updated content
const symlinkContent = await fs.readFile(symlinkPath, 'utf-8');
const targetContent = await fs.readFile(targetFile, 'utf-8');
expect(symlinkContent).toBe('UPDATED VIA SYMLINK');
expect(targetContent).toBe('UPDATED VIA SYMLINK');
});
it('should prevent overwriting files through symlinks pointing outside allowed directories', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping symlink overwrite prevention test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const legitFile = path.join(allowedDir, 'existing.txt');
const targetFile = path.join(forbiddenDir, 'target.txt');
// Create a legitimate file first
await fs.writeFile(legitFile, 'LEGIT CONTENT', 'utf-8');
// Create target file in forbidden directory
await fs.writeFile(targetFile, 'FORBIDDEN CONTENT', 'utf-8');
// Now replace the legitimate file with a symlink to forbidden location
await fs.unlink(legitFile);
await fs.symlink(targetFile, legitFile);
// Simulate the server's validation logic
const stats = await fs.lstat(legitFile);
expect(stats.isSymbolicLink()).toBe(true);
const realPath = await fs.realpath(legitFile);
expect(isPathWithinAllowedDirectories(realPath, allowed)).toBe(false);
// With atomic rename, symlinks are replaced not followed
// So this test now demonstrates the protection
// Verify content remains unchanged
const targetContent = await fs.readFile(targetFile, 'utf-8');
expect(targetContent).toBe('FORBIDDEN CONTENT');
});
it('demonstrates race condition in read operations', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping race condition in read operations test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const legitFile = path.join(allowedDir, 'readable.txt');
const secretFile = path.join(forbiddenDir, 'secret.txt');
// Create legitimate file
await fs.writeFile(legitFile, 'PUBLIC CONTENT', 'utf-8');
// Create secret file in forbidden directory
await fs.writeFile(secretFile, 'SECRET CONTENT', 'utf-8');
// Step 1: validatePath would pass for legitimate file
expect(isPathWithinAllowedDirectories(legitFile, allowed)).toBe(true);
// Step 2: Race condition - replace file with symlink after validation
await fs.unlink(legitFile);
await fs.symlink(secretFile, legitFile);
// Step 3: Read operation follows symlink to forbidden location
const content = await fs.readFile(legitFile, 'utf-8');
// This shows the vulnerability - we read forbidden content
expect(content).toBe('SECRET CONTENT');
expect(isPathWithinAllowedDirectories(await fs.realpath(legitFile), allowed)).toBe(false);
});
it('verifies rename does not follow symlinks', async () => {
const symlinkSupported = await getSymlinkSupport();
if (!symlinkSupported) {
console.log(' ⏭️ Skipping rename symlink test - symlinks not supported');
return;
}
const allowed = [allowedDir];
const tempFile = path.join(allowedDir, 'temp.txt');
const targetSymlink = path.join(allowedDir, 'target-symlink.txt');
const forbiddenTarget = path.join(forbiddenDir, 'forbidden-target.txt');
// Create forbidden target
await fs.writeFile(forbiddenTarget, 'ORIGINAL CONTENT', 'utf-8');
// Create symlink pointing to forbidden location
await fs.symlink(forbiddenTarget, targetSymlink);
// Write temp file
await fs.writeFile(tempFile, 'NEW CONTENT', 'utf-8');
// Rename temp file to symlink path
await fs.rename(tempFile, targetSymlink);
// Check what happened
const symlinkExists = await fs.lstat(targetSymlink).then(() => true).catch(() => false);
const isSymlink = symlinkExists && (await fs.lstat(targetSymlink)).isSymbolicLink();
const targetContent = await fs.readFile(targetSymlink, 'utf-8');
const forbiddenContent = await fs.readFile(forbiddenTarget, 'utf-8');
// Rename should replace the symlink with a regular file
expect(isSymlink).toBe(false);
expect(targetContent).toBe('NEW CONTENT');
expect(forbiddenContent).toBe('ORIGINAL CONTENT'); // Unchanged
});
});
});