Nosql Injection on Fly Io

Nosql Injection in Fly Io applications typically occurs when user input is directly interpolated into MongoDB queries without proper sanitization. Fly Io's serverless architecture means your application code runs in ephemeral containers, but this doesn't protect against injection attacks targeting your database layer.

The most common vulnerability pattern in Fly Io apps involves Node.js applications using the native MongoDB driver or Mongoose ODM. Consider this vulnerable code running on a Fly Io app:

const express = require('express');
const { MongoClient } = require('mongodb');
const app = express();

app.get('/users/search', async (req, res) => {
  const { name } = req.query;
  const client = new MongoClient(process.env.MONGO_URI);
  await client.connect();
  const db = client.db();
  
  // VULNERABLE: Direct interpolation of user input
  const query = { name: { $regex: name } };
  const results = await db.collection('users').find(query).toArray();
  
  res.json(results);
  await client.close();
});

An attacker could exploit this by sending a request like:

/users/search?name=.*%7B%24ne%3A%27%27%7D

This translates to a regex pattern that matches all documents, effectively bypassing authentication or authorization checks. The attack works because MongoDB's query language allows operators like $regex, $where, and $ne to be nested within other operators.

Another common pattern in Fly Io apps involves aggregation pipeline injection:

app.get('/products', async (req, res) => {
  const { category, limit } = req.query;
  
  const pipeline = [
    { $match: { category } },
    { $limit: parseInt(limit) || 10 }
  ];
  
  const results = await db.collection('products').aggregate(pipeline).toArray();
  res.json(results);
});

If an attacker sends category[$ne]=, they can manipulate the $match stage to return all products regardless of category. This is particularly dangerous in Fly Io's multi-tenant environments where different applications might share the same database cluster.

Fly Io's deployment model can exacerbate these issues. When you deploy with fly deploy, your application might scale horizontally across multiple regions, creating opportunities for timing-based attacks if your application doesn't properly handle concurrent database operations with injected queries.

Detecting NoSQL injection in Fly Io applications requires a combination of static analysis and runtime scanning. middleBrick's black-box scanning approach is particularly effective for Fly Io deployments since it doesn't require access to your source code or database credentials.

For runtime detection, middleBrick tests your Fly Io API endpoints with specifically crafted payloads targeting MongoDB's query operators. The scanner sends requests containing:

• { $where: 'this.user == "admin"' } - JavaScript code injection
• { $ne: null } - Match all documents
• { $regex: '.*' } - Wildcard pattern matching
• { $expr: { $gt: [ '$salary', 100000 ] } } - Expression-based queries
• { $or: [ { admin: true }, { admin: true } ] } - Logical operator abuse

When scanning a Fly Io app deployed at https://api.example.fly.dev, middleBrick's CLI shows:

$ middlebrick scan https://api.example.fly.dev
Scan started: API Security Assessment
Testing endpoint: GET /users/search
✓ Authentication check passed
⚠️  BOLA/IDOR check - suspicious query structure
✗ NoSQL Injection detected: $where operator abuse
   Severity: High
   Recommendation: Use parameterized queries or input validation

For local development on Fly Io, you can use the built-in MongoDB query validator. Add this middleware to catch suspicious patterns before they reach your database:

const mongoValidator = (req, res, next) => {
  const suspiciousOperators = ['$where', '$regex', '$ne', '$nin', '$not'];
  
  if (queryKeys.some(key => suspiciousOperators.some(op => key.includes(op)))) {
    return res.status(400).json({
      error: 'Invalid query parameters detected',
      details: 'Query contains suspicious MongoDB operators'
    });
  }
  next();
};

middleBrick also checks for improper error handling, which is crucial in Fly Io apps. When NoSQL injection attempts cause database errors, your application should never expose stack traces or database error messages to clients. The scanner verifies that error responses are properly sanitized.

Remediating NoSQL injection in Fly Io applications requires a defense-in-depth approach. Start with input validation using a whitelist approach specific to your application's needs:

const validateInput = (input, schema) => {
  const { error } = schema.validate(input);
  if (error) throw new Error('Invalid input');
  return input;
};

const userSchema = Joi.object({
  name: Joi.string().trim().max(100).required(),
  email: Joi.string().email().required(),
  age: Joi.number().integer().min(0).max(120).optional()
});

For Fly Io's serverless model, implement query parameterization using MongoDB's native features:

app.get('/users/search', async (req, res) => {
  const { name } = req.query;
  
  // Strict validation before query construction
  if (name && typeof name !== 'string') {
    return res.status(400).json({ error: 'Invalid name parameter' });
  }
  
  const client = new MongoClient(process.env.MONGO_URI);
  await client.connect();
  const db = client.db();
  
  // SAFE: Use explicit field matching, no operator injection
  const query = name ? { name: { $regex: `^${name}$`, $options: 'i' } } : {};
  const results = await db.collection('users').find(query).toArray();
  
  res.json(results);
  await client.close();
});

Fly Io's edge deployment capabilities allow you to implement request filtering at the edge before requests reach your application:

// fly.toml configuration for edge protection
[http.middlewares.nosql_protection]
  [http.middlewares.nosql_protection.ratelimit]
  requests = 100
  window = "1m"
  
  [http.middlewares.nosql_protection.requestheaders]
  # Block requests containing suspicious patterns
  [http.middlewares.nosql_protection.requestheaders.add]
  x-blocked-reason = "Potential NoSQL injection attempt"
  
  [http.middlewares.nosql_protection.requestheaders.setifmissing]
  x-security-scanned = "true"

For aggregation pipelines, always use explicit operator arrays rather than dynamic construction:

const buildSafePipeline = (category, limit) => {
  const pipeline = [];
  
  if (category) {
    // SAFE: Explicit operator, no user control over structure
    pipeline.push({ $match: { category: category } });
  }
  
  if (limit) {
    const safeLimit = Math.min(parseInt(limit), 100); // Cap maximum
    pipeline.push({ $limit: safeLimit });
  }
  
  return pipeline;
};

Deploy these changes to your Fly Io app with proper testing:

fly deploy --remote-only --strategy rolling

# After deployment, verify with middleBrick
middlebrick scan https://your-app.fly.dev

middleBrick's GitHub Action can be configured to fail your CI pipeline if NoSQL injection vulnerabilities are detected:

name: API Security Scan
on: [push]
jobs:
  security-scan:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Run middleBrick Scan
        uses: middlebrick/middlebrick-action@v1
        with:
          target_url: ${{ secrets.API_URL }}
          fail_threshold: "high"