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Fix Broken User Authentication in Go Fiber

Broken Authentication is the crown jewel for attackers. In Go Fiber, developers frequently fall into the trap of using weak session management, plaintext password comparisons, and failing to implement brute-force protections. Hardening your auth stack requires moving from 'functional' code to 'defensive' code by enforcing cryptographic standards and transport security.

The Vulnerable Pattern

app.Post("/login", func(c *fiber.Ctx) error {
    type Login struct { Username, Password string }
    var input Login
    c.BodyParser(&input)

// VULNERABILITIES:
// 1. Plaintext password comparison (No Hashing)
// 2. No Rate Limiting (Susceptible to brute-force)
// 3. Predictable/Static Session Token
// 4. No Secure Cookie Flags
if input.Username == "admin" && input.Password == "p@ssword123" {
    return c.JSON(fiber.Map{"auth_token": "session_12345"})
}
return c.SendStatus(fiber.StatusUnauthorized)


})

The Secure Implementation

The secure implementation mitigates the OWASP Top 10 Broken Authentication risk through three primary controls. First, the 'limiter' middleware prevents automated credential stuffing by throttling requests. Second, we utilize 'bcrypt' for password verification, which is resistant to rainbow table attacks and incorporates a work factor to slow down offline cracking. Third, the Go Fiber session store is configured with 'CookieHTTPOnly' to prevent XSS-based token theft and 'CookieSecure' to ensure tokens are never transmitted over unencrypted HTTP. We also utilize a server-side session store rather than returning predictable or static JSON tokens.

import (
    "github.com/gofiber/fiber/v2"
    "github.com/gofiber/fiber/v2/middleware/limiter"
    "github.com/gofiber/fiber/v2/middleware/session"
    "golang.org/x/crypto/bcrypt"
    "time"
)

// Initialize secure session store
var store = session.New(session.Config{
Expiration:     1 * time.Hour,
CookieHTTPOnly: true,
CookieSecure:   true,
CookieSameSite: “Lax”,
})


func SetupAuth(app *fiber.App) {
// Implement Rate Limiting to kill brute-force attempts
loginLimiter := limiter.New(limiter.Config{
Max:        5,
Expiration: 1 * time.Minute,
LimitReached: func(c *fiber.Ctx) error {
return c.Status(429).JSON(fiber.Map{“error”: “Too many attempts”})
},
})


app.Post("/login", loginLimiter, func(c *fiber.Ctx) error {
    var input struct{ User, Pass string }
    if err := c.BodyParser(&input); err != nil { return c.SendStatus(400) }

    // 1. Fetch hashed password from DB (Mocked here)
    storedHash := "$2a$12$L8..." 

    // 2. Use Constant-Time Hashing for comparison
    if err := bcrypt.CompareHashAndPassword([]byte(storedHash), []byte(input.Pass)); err != nil {
        return c.SendStatus(401)
    }

    // 3. Generate Cryptographically Secure Session
    sess, _ := store.Get(c)
    sess.Set("uid", "user_id_99")
    if err := sess.Save(); err != nil { return c.SendStatus(500) }

    return c.JSON(fiber.Map{"status": "authenticated"})
})


}

System Alert • ID: 7660
Target: Go Fiber API
Potential Vulnerability

Your Go Fiber API might be exposed to Broken User Authentication

74% of Go Fiber apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.

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