Broken Authentication in Fiber with Basic Auth

Basic authentication over unencrypted channels is a common source of broken authentication in Go Fiber applications. Because the credentials are transmitted in an easily decoded header, an attacker who observes the traffic can recover the username and password. When endpoints rely solely on Basic Auth without additional protections, the risk of account compromise and unauthorized access increases, especially when combined with other weaknesses such as missing transport security or weak session management.

In a black-box scan, middleBrick tests unauthenticated attack surfaces and flags authentication issues when endpoints accept Basic Auth credentials but do not enforce sufficient safeguards. For example, if a route uses app.Get("/admin", fiber.BasicAuth(func(user, pass string) bool { return user == "admin" && pass == "secret" })) without HTTPS, credentials can be intercepted. Even when HTTPS is present, relying only on Basic Auth can be risky if the application does not enforce strong password policies, account lockouts, or proper token-based alternatives. Vulnerable patterns also appear when developers accidentally expose admin or debug routes that accept weak or default credentials, effectively turning Basic Auth into a weak gate.

Another aspect is how the application handles authentication failures. Returning detailed error messages or inconsistent HTTP status codes can aid attackers in enumerating valid users. middleBrick checks for authentication bypass indicators, such as routes that do not properly validate credentials or that allow access when credentials are missing or malformed. In API designs where Basic Auth is used for machine-to-machine communication, rotating credentials and binding requests to specific scopes is essential. Without these measures, leaked credentials can lead to privilege escalation, data exposure, or further attacks such as SSRF when the same service account has extended permissions.

middleBrick’s authentication checks examine whether endpoints that use Basic Auth also implement complementary controls, such as rate limiting to deter credential spraying, input validation to prevent header injection, and secure transmission via TLS. Even in unauthenticated scans, the tool can detect whether credentials are accepted over non-TLS connections and whether the response behavior leaks information. By correlating these findings with the runtime tests, the scanner provides a clear view of how broken authentication manifests in a Fiber service that depends on Basic Auth.

To address broken authentication when using Basic Auth in Fiber, always enforce HTTPS, avoid hard-coded credentials, and prefer token-based mechanisms for anything beyond simple testing. Below are concrete, secure patterns you can apply.

Enforce HTTPS and use secure comparison

Ensure your Fiber instance terminates TLS and that all routes requiring authentication are served only over HTTPS. Use a constant-time comparison to mitigate timing attacks when checking credentials.

const crypto = require("crypto");
const https = require("https");
const fs = require("fs");

const app = require("express")(); // Fiber uses Express-like API in examples
const tlsOptions = {
  key: fs.readFileSync("/path/to/server.key"),
  cert: fs.readFileSync("/path/to/server.crt"),
};

function secureCompare(a, b) {
  return crypto.timingSafeEqual(Buffer.from(a), Buffer.from(b));
}

https.createServer(tlsOptions, app).listen(443, () => {
  console.log("Secure server running on port 443");
});

Environment-based credentials and middleware protection

Store usernames and hashed passwords in environment variables. Use a verification function that hashes the provided password and compares it to the stored hash, rather than plain-text checks.

const dotenv = require("dotenv");
dotenv.config();

const validUser = process.env.AUTH_USER; // e.g., admin
const validHash = process.env.AUTH_HASH; // precomputed hash of the password

function verifyCredentials(user, pass) {
  if (!user || !pass) return false;
  const inputHash = crypto.createHash("sha256").update(pass).digest("hex");
  return secureCompare(Buffer.from(inputHash), Buffer.from(validHash));
}

app.get("/admin", (req, res, next) => {
  const header = req.headers["authorization"];
  if (!header || !header.startsWith("Basic ")) {
    res.status(401).set("WWW-Authenticate", "Basic realm="Restricted"").send("Unauthorized");
    return;
  }
  const base64 = header.split(" ")[1];
  const decoded = Buffer.from(base64, "base64").toString("utf8");
  const [user, pass] = decoded.split(":");
  if (verifyCredentials(user, pass)) {
    return next();
  }
  res.status(403).send("Forbidden");
}, (req, res) => {
  res.json({ message: "Access granted to admin" });
});

Avoid default credentials and add rate limiting

Never ship with default usernames or passwords. Integrate rate limiting to reduce the risk of credential spraying. In a production deployment, consider replacing Basic Auth with session-based or token-based authentication for better security and scalability.

const rateLimit = require("express-rate-limit");

const apiLimiter = rateLimit({
  windowMs: 15 * 60 * 1000, // 15 minutes
  max: 30, // limit each IP to 30 requests per window
  message: { error: "Too many requests, try again later." },
});

app.use("/api/", apiLimiter);

By combining TLS, secure credential handling, and operational practices such as rotating credentials and monitoring logs, you reduce the attack surface associated with Basic Auth in Fiber. These steps align with common findings highlighted by security scanners when testing authentication mechanisms.