Nosql Injection in Fiber with Api Keys

Nosql Injection occurs when user-controlled input is directly interpreted as part of a NoSQL query, allowing an attacker to alter query logic. In the Go Fiber framework, this risk is amplified when endpoints that accept query parameters, headers, or request bodies also rely on API keys for access control without proper validation and sanitization.

Consider a Fiber route that retrieves a user profile using a username provided via a URL path parameter and an API key passed in a request header. If the API key is used only for basic authentication checks and the username is directly interpolated into a NoSQL query (for example, a MongoDB query), an attacker can supply crafted input such as {'$ne': null} to manipulate the query’s logic. Because the API key does not sanitize or validate the data used in the query, the server may unintentionally return other users’ records or bypass intended filters.

Additionally, API keys exposed in client-side code or transmitted over insecure channels can be intercepted and reused in injection attempts. An attacker who discovers or guesses a valid API key might send specially crafted requests where input fields like filter or search are controlled, enabling them to inject operators such as $gt, $in, or $or into the backend query. This changes the scope of data returned or triggers unauthorized operations, demonstrating how improper handling of API keys combined with untrusted input creates a Nosql Injection surface.

Real-world patterns include routes that build queries from JSON payloads without schema validation, where keys like username or organizationId are used directly in match conditions. If the API key is accepted as a header and used to scope data but the underlying query is not hardened, the API may leak information across tenants or allow privilege escalation when an attacker modifies injected query structures.

These issues map to common categories in the OWASP API Top 10, particularly Broken Object Level Authorization and Injection. Because Fiber applications often handle high-throughput requests, unchecked input combined with key-based access can lead to data exposure or unauthorized dataset traversal, even when the API key mechanism appears intact.

Remediation focuses on strict input validation, avoiding direct concatenation of user data into NoSQL queries, and ensuring API key usage does not bypass query construction safety.

• Validate and sanitize all inputs: Use structured validation libraries to ensure incoming data conforms to expected formats before using it in queries.
• Parameterize queries: Build query objects programmatically without inserting raw user input directly into query operators.
• Scope data by tenant or user ID explicitly, rather than relying on input-derived values alone.
• Do not expose API keys in URLs or logs, and enforce HTTPS to prevent interception.

Example: Unsafe Fiber route with potential Nosql Injection

const { app } = require('express')(); // Fiber uses similar patterns
const MongoClient = require('mongodb').MongoClient;

app.get('/profile/:username', async (req, res) => {
  const apiKey = req.headers['x-api-key'];
  if (!validateKey(apiKey)) {
    return res.status(401).send('Unauthorized');
  }
  const client = new MongoClient('mongodb://localhost:27017');
  await client.connect();
  const db = client.db('mydb');
  // UNSAFE: username injected directly into query
  const user = await db.collection('users').findOne({
    username: req.params.username,
    accessKey: apiKey
  });
  res.json(user);
});

Example: Secured Fiber route with proper handling

const { app } = require('express')();
const MongoClient = require('mongodb').MongoClient;
const { body, param, header } = require('express-validator');

const validateKey = (key) => {
  // Replace with secure key lookup and verification
  return typeof key === 'string' && key.length === 32;
};

app.get('/profile/:username', [
  param('username').isAlphanumeric().isLength({ min: 3, max: 20 }),
  header('x-api-key').custom((value) => validateKey(value))
], async (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).json({ errors: errors.array() });
  }

  const apiKey = req.headers['x-api-key'];
  const client = new MongoClient('mongodb://localhost:27017');
  await client.connect();
  const db = client.db('mydb');

  // SAFE: username is parameterized, not concatenated into query structure
  const user = await db.collection('users').findOne({
    username: req.params.username,
    accessKey: apiKey
  });

  if (!user) {
    return res.status(404).send('Not found');
  }
  res.json(user);
});

In this secured pattern, the API key is still used for access checks and query scoping, but the username is strictly validated and never used to construct query operators dynamically. This prevents injection via special operators while preserving the intended access control behavior.

For production deployments, combine this approach with environment-managed key verification and continuous scanning. Tools like middleBrick can automatically detect such patterns by submitting the unauthenticated attack surface of your Fiber endpoints and analyzing how API keys interact with input handling, providing prioritized findings and remediation guidance without requiring internal configuration.