Data Exposure in Chi with Basic Auth

The combination of Chi and HTTP Basic Authentication can unintentionally expose sensitive data when credentials are handled or transmitted in an unsafe manner. Chi is a lightweight routing library for Node.js, and while it does not enforce authentication itself, it is commonly used to define routes that may rely on Basic Auth headers passed by clients.

In a black-box scan, middleBrick checks whether authentication is required for an endpoint and how credentials are managed. If an API uses Basic Auth over unencrypted HTTP, credentials are encoded in Base64 and sent in the Authorization header. Base64 is not encryption; it is easily reversible. Without TLS, these credentials can be intercepted and decoded by an attacker on the network path.

Additionally, data exposure can occur server-side if route handlers in Chi log or expose Authorization headers inadvertently. For example, a developer might log the full request object for debugging, which includes the authorization header. This can lead to credential leakage in log files or monitoring systems.

middleBrick’s Data Exposure checks look for unencrypted transmission of credentials, missing security headers such as Strict-Transport-Security, and improper handling of sensitive data in application code. When Basic Auth is used without HTTPS, middleBrick flags the finding with high severity, noting that credentials can be recovered from network traffic.

Another scenario involves misconfigured CORS or missing input validation in Chi routes, which can allow unauthorized origins to access authenticated endpoints. This may expose protected resources or reveal that Basic Auth is in use, aiding attackers in crafting targeted credential brute-force attempts. The scanner cross-references the OpenAPI spec, if provided, with runtime behavior to confirm whether authentication is consistently enforced and whether responses inadvertently include sensitive data.

For LLM-related endpoints, Data Exposure also checks whether prompts, system messages, or outputs leak through misconfigured routes. While this is less common with Basic Auth–only APIs, the risk increases when combined with verbose error messages or debug endpoints that reveal internal state.

Overall, the risk arises from using Basic Auth without transport encryption and proper server-side handling. middleBrick identifies these gaps by testing unauthenticated attack surfaces and correlating spec definitions with observed responses, ensuring that exposure points are clearly documented with remediation guidance.

To remediate Data Exposure when using Basic Auth with Chi, enforce HTTPS and avoid logging or mishandling credentials. Below are concrete code examples demonstrating secure practices.

First, always terminate TLS at the proxy or server layer. In development, you can use https module to serve Chi apps securely:

const https = require('https');
const fs = require('fs');
const { router } = require('itty-router');

const app = router();

app.get('/secure', (request) => {
  const auth = request.headers.get('authorization');
  if (!auth || !auth.startsWith('Basic ')) {
    return new Response('Unauthorized', { status: 401, headers: { 'WWW-Authenticate': 'Basic' } });
  }
  // Validate credentials here (e.g., compare against environment variables)
  return new Response('Secure Data');
});

const options = {
  key: fs.readFileSync('server.key'),
  cert: fs.readFileSync('server.crt')
};

https.createServer(options, app).listen(8443, () => {
  console.log('HTTPS server running on port 8443');
});

Second, avoid logging sensitive headers. Ensure your Chi routes do not include the Authorization header in logs:

app.get('/data', (request) => {
  // Bad: logging authorization header
  // console.log(request.headers);

  // Good: extract only necessary, non-sensitive data
  const path = request.url;
  console.log(`Request received for: ${path}`);

  const auth = request.headers.get('authorization');
  if (!auth || !isValidCredential(auth)) {
    return new Response('Forbidden', { status: 403 });
  }
  return new Response('OK');
});

function isValidCredential(authHeader) {
  const expected = 'Basic ' + Buffer.from('user:pass').toString('base64');
  return authHeader === expected;
}

Third, use environment variables to store credentials and avoid hardcoding them in route handlers:

const USER = process.env.BASIC_USER;
const PASS = process.env.BASIC_PASS;
const expected = 'Basic ' + Buffer.from(`${USER}:${PASS}`).toString('base64');

app.get('/protected', (request) => {
  const auth = request.headers.get('authorization');
  if (auth !== expected) {
    return new Response('Unauthorized', { status: 401, headers: { 'WWW-Authenticate': 'Basic' } });
  }
  return new Response('Authorized content');
});

Finally, consider migrating from Basic Auth to token-based mechanisms such as Bearer tokens where possible, as they offer better control and revocation capabilities. If Basic Auth must be used, ensure strict transport security and avoid exposing credentials in any part of the application stack.