Integrity Failures in Fiber with Basic Auth

In Go Fiber, using HTTP Basic Authentication without additional integrity controls can expose endpoints to integrity failures. An integrity failure occurs when an attacker can modify request data or authentication-related parameters between the client and server, or when the server processes tampered data in an unsafe way. With Basic Auth, credentials are base64-encoded but not encrypted; if transport integrity is not enforced (e.g., missing or misconfigured TLS), credentials can be intercepted. More critically, integrity failures can manifest when user-controlled data derived from authenticated contexts is used in unsafe operations, such as constructing file paths, database queries, or internal API calls, enabling authenticated tampering attacks.

Consider an authenticated endpoint in Fiber that reads a resource identifier from a header or query parameter after Basic Auth validates the user. If the server trusts the client-supplied identifier without validation, an authenticated attacker can modify the identifier to access or act on other resources (often related to authorization flaws, but integrity failures focus on data manipulation). Similarly, if the server reflects user input into system commands or deserialization routines after authentication, tampered content can lead to unexpected behavior, such as command injection or object injection. Basic Auth alone does not protect against these post-authentication manipulations; integrity mechanisms—such as input validation, canonicalization, and secure serialization—are required to ensure data remains trustworthy after authentication.

Real-world attack patterns mirror findings from OWASP API Top 10 and related frameworks. For example, an unauthenticated attacker might first conduct reconnaissance to discover Basic Auth–protected endpoints, then probe for parameter tampering or injection via authenticated sessions. Insecure deserialization findings, SSRF via manipulated URLs, or unsafe consumption of JSON/XML payloads can follow if integrity checks are missing. middleBrick’s 12 security checks—including Input Validation, Property Authorization, Unsafe Consumption, and SSRF—run in parallel and can surface these integrity-related risks when Basic Auth is present but not paired with strict validation and safe handling of derived data.

middleBrick scans unauthenticated attack surfaces and can detect scenarios where Basic Auth–protected endpoints exhibit integrity weaknesses by analyzing OpenAPI specifications (with full $ref resolution) and correlating runtime behavior. For instance, if a spec defines security schemes using Basic Auth and routes accept mutable user input without clear validation constraints, the scan highlights high-risk inputs and provides remediation guidance. This helps developers understand how integrity failures can coexist with seemingly simple authentication methods and prioritize fixes that ensure authenticated data is never implicitly trusted.

Securing Basic Auth in Fiber requires combining transport integrity, strict input validation, and safe handling of authenticated context. Below are concrete code examples using the Fiber framework and the standard library’s net/http basic authentication helper. These examples assume TLS is enforced at the termination layer (e.g., reverse proxy or load balancer), as Basic Auth must never be used over cleartext HTTP.

First, define a validation middleware that checks credentials and enforces strict parameter validation for authenticated requests:

const basicAuth = require('basic-auth');

const authMiddleware = (req, res, next) => {
  const user = basicAuth(req);
  if (!user || !isValidUser(user.name, user.pass)) {
    res.status(401).send({ error: 'Unauthorized' });
    return;
  }
  // Attach minimal, validated identity to request context
  req.context.user = { name: user.name };
  next();
};

// Example user validation (use constant-time comparison in production)
const isValidUser = (username, password) => {
  // Validate format, length, and use secure credential store
  if (!/^[A-Za-z0-9_-]{3,32}$/.test(username)) return false;
  // password check omitted; integrate with secure secret store
  return true;
};

module.exports = authMiddleware;

Next, apply the middleware to protected routes and validate all inputs derived from authenticated requests. Never trust IDs, paths, or filenames provided by the client—even when the user is authenticated. Use allowlists, canonicalization, and strict type checks:

const express = require('express');
const app = express();
app.use(express.json());

app.get('/resource/:id', authMiddleware, (req, res) => {
  // Validate ID format strictly; do not concatenate into file paths or queries
  const id = req.params.id;
  if (!/^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$/.test(id)) {
    return res.status(400).send({ error: 'Invalid resource identifier' });
  }
  // Use safe data access layer with parameterized queries
  const resource = getResourceById(id);
  if (!resource || resource.owner !== req.context.user.name) {
    return res.status(403).send({ error: 'Forbidden' });
  }
  res.json(resource);
});

function getResourceById(id) {
  // Example: parameterized database query
  // db.query('SELECT * FROM resources WHERE id = $1 AND owner = $2', [id, user])
  return { id, owner: 'alice', data: 'safe' };
}

For request bodies, validate and sanitize all fields before use. Avoid reflection of raw user input and enforce schema validation:

const { body, validationResult } = require('express-validator');

app.post('/update', authMiddleware, [
  body('resourceId').isUUID(),
  body('action').isIn(['read', 'write', 'delete']),
], (req, res) => {
  const errors = validationResult(req);
  if (!errors.isEmpty()) {
    return res.status(400).send({ errors: errors.array() });
  }
  const { resourceId, action } = req.body;
  // Perform action with canonicalized resourceId
  performAction(resourceId, action, req.context.user.name);
  res.send({ status: 'ok' });
});

function performAction(resourceId, action, user) {
  // Safe processing: canonicalize and verify ownership
  const canonicalId = resourceId.toLowerCase();
  // ...
}