Path Traversal on Digitalocean

Detecting path traversal in Digitalocean applications requires both static analysis and runtime scanning. middleBrick's black-box scanner identifies these vulnerabilities by testing unauthenticated endpoints with path traversal payloads.

For Digitalocean Spaces applications, middleBrick tests common traversal patterns:

../../etc/passwd
../windows/win.ini
....//....//etc/passwd
./././etc/passwd
WEB-INF/web.xml

The scanner examines how the application handles these requests, looking for:

• Information disclosure through error messages
• Unexpected redirects to sensitive locations
• HTTP 200 responses containing sensitive data
• Differentiated error responses that reveal file existence

For Digitalocean App Platform deployments, middleBrick also checks for:

• Environment variable exposure through traversal
• Access to .do files (Digitalocean configuration files)
• Traversal in Dockerfile paths during build processes

Manual testing should include:

curl -v 'https://your-app.digitalocean.app/download/../../etc/passwd'
curl -v 'https://your-app.digitalocean.app/download/..%2f..%2fetc%2fpasswd' # URL encoded

Digitalocean's Spaces API has built-in protections, but applications often add layers that reintroduce vulnerabilities. middleBrick's OpenAPI analysis can identify risky path parameters in your API specification that might be vulnerable to traversal attacks.

Remediating path traversal in Digitalocean applications requires input validation and safe path handling. Here are Digitalocean-specific fixes:

1. Input Validation with Pathname Module

const { S3Client } = require('@aws-sdk/client-s3');
const path = require('path');

const s3Client = new S3Client({
  region: 'nyc3',
  credentials: { accessKeyId: process.env.SPACES_KEY, secretAccessKey: process.env.SPACES_SECRET }
});

app.get('/download/:filename', async (req, res) => {
  const filename = req.params.filename;
  
  // Validate: only allow alphanumeric, hyphens, underscores, and dots
  if (!/^[a-zA-Z0-9._-]+$/.test(filename)) {
    return res.status(400).send('Invalid filename');
  }
  
  // Prevent traversal by resolving and checking prefix
  const safePath = path.normalize(filename);
  if (safePath.startsWith('.') || safePath.includes('..')) {
    return res.status(400).send('Invalid path');
  }
  
  const params = {
    Bucket: 'my-space',
    Key: safePath
  };
  
  try {
    const url = await getSignedUrl(s3Client, 'getObject', params);
    res.redirect(url);
  } catch (err) {
    res.status(404).send('File not found');
  }

2. Using Digitalocean's Built-in Security Features

Digitalocean App Platform provides security configurations that help prevent traversal attacks:

# app.yaml for Digitalocean App Platform
name: my-app
region: nyc
services:
- name: api
  git:
    repo_clone_url: https://github.com/your-org/your-repo.git
    branch: main
  build_command: npm run build
  run_command: npm start
  health_check_path: /health
  environment_variables:
      scope: RUN_TIME
      value: production
  # Security hardening

3. Safe Path Construction with Digitalocean Spaces

const { S3Client, GetObjectCommand } = require('@aws-sdk/client-s3');

const s3Client = new S3Client({
  region: 'nyc3',
  credentials: {
    accessKeyId: process.env.SPACES_KEY,
    secretAccessKey: process.env.SPACES_SECRET
  }
});

function safeDownload(filename) {
  // Whitelist allowed characters
  if (!/^[a-zA-Z0-9_.-]+$/.test(filename)) {
    throw new Error('Invalid characters in filename');
  }
  
  // Resolve to absolute path within allowed directory
  const baseDir = 'uploads/';
  const fullPath = path.join(baseDir, filename);
  
  // Verify the resolved path is within the base directory
  if (!fullPath.startsWith(baseDir)) {
    throw new Error('Path traversal attempt detected');
  }
  
  return fullPath;
}

app.get('/secure-download/:filename', async (req, res) => {
  try {
    const safePath = safeDownload(req.params.filename);
    const params = {
      Bucket: 'my-space',
      Key: safePath
    };
    
    const data = await s3Client.send(new GetObjectCommand(params));
    res.attachment(safePath.split('/').pop());
    data.Body.pipe(res);
  } catch (err) {
    res.status(400).send('Invalid request');
  }