Missing Authentication in Fiber

Missing authentication in Fiber applications typically occurs when endpoints that should be protected are left accessible without any credential verification. This creates opportunities for unauthorized users to access sensitive functionality, manipulate data, or trigger privileged operations.

In Fiber applications, this vulnerability often appears in API endpoints that handle CRUD operations on user data. For example, an endpoint that returns user profiles or allows profile updates without verifying the requester's identity:

app := fiber.New()

app.Get("/api/users/:id", func(c *fiber.Ctx) error {
    id := c.Params("id")
    user, err := db.GetUser(id)
    if err != nil {
        return c.Status(404).SendString("User not found")
    }
    return c.JSON(user) // No authentication check!
})

This endpoint allows any requester to retrieve any user's profile by simply changing the ID parameter—a classic Broken Object Level Authorization (BOLA) scenario that stems from missing authentication.

Another common manifestation appears in administrative endpoints that manage system resources:

app.Post("/api/admin/shutdown", func(c *fiber.Ctx) error {
    // No authentication or authorization check
    return shutdownSystem()
})

Here, anyone who discovers this endpoint could shut down the entire application. Fiber's minimalist design makes it easy to accidentally expose such endpoints when rapid development takes priority over security.

Missing authentication also frequently appears in webhook handlers and callback endpoints:

app.Post("/api/webhooks/payment", func(c *fiber.Ctx) error {
    payload := new(PaymentPayload)
    if err := c.BodyParser(payload); err != nil {
        return c.Status(400).SendString("Invalid payload")
    }
    // Process payment without verifying webhook signature
    processPayment(payload)
    return c.SendStatus(200)
})

Without verifying the webhook's signature or source, attackers can trigger fraudulent payment processing by sending crafted requests to this endpoint.

Detecting missing authentication in Fiber applications requires both manual code review and automated scanning. When reviewing code, look for these patterns:

• Endpoints handling user data without ctx.Locals("user") or similar user context
• Administrative endpoints without middleware protection
• Database queries using request parameters without identity verification
• State-changing operations (POST, PUT, DELETE) without authentication

Automated detection with middleBrick provides comprehensive coverage without requiring source code access. middleBrick's black-box scanner tests the unauthenticated attack surface by attempting to access protected functionality without credentials:

middlebrick scan https://api.example.com --max-depth=3 --output=json

The scanner identifies endpoints that should require authentication but respond to unauthenticated requests. For Fiber applications specifically, middleBrick tests common patterns like:

• User profile endpoints (/api/users/:id, /api/profile)
• Administrative functions (/api/admin/*, /manage/*)
• Webhook handlers (/api/webhooks/*)
• Database operations (/api/data/*, /api/items/*)

middleBrick's LLM security module also detects unauthenticated AI endpoints, which is particularly relevant for Fiber applications using AI/ML libraries:

middlebrick scan https://api.example.com --ai-security

This scan checks for exposed AI model endpoints that could be exploited for prompt injection or data exfiltration without authentication.

Remediating missing authentication in Fiber applications involves implementing proper authentication middleware and applying it consistently across protected endpoints. Here's a comprehensive approach using JWT authentication:

package main

import (
    "github.com/gofiber/fiber/v2"
    "github.com/gofiber/fiber/v2/middleware/jwt"
    "github.com/golang-jwt/jwt/v5"
    "time"
)

func main() {
    app := fiber.New()

    // JWT middleware configuration
    app.Use(jwt.New(jwt.Config{
        SigningKey: []byte("supersecretkey"),
        ErrorHandler: func(c *fiber.Ctx, err error) error {
            return c.Status(401).JSON(fiber.Map{
                "error": "Unauthorized",
                "message": err.Error(),
            })
        },
    }))

    // Protected endpoints
    app.Get("/api/users/me", func(c *fiber.Ctx) error {
        claims := c.Locals("user").(*jwt.Token).Claims.(*jwt.RegisteredClaims)
        userID := claims.Subject
        
        user, err := db.GetUser(userID)
        if err != nil {
            return c.Status(404).SendString("User not found")
        }
        return c.JSON(user)
    })

    app.Put("/api/users/me", func(c *fiber.Ctx) error {
        claims := c.Locals("user").(*jwt.Token).Claims.(*jwt.RegisteredClaims)
        userID := claims.Subject
        
        // Only allow updating own profile
        if c.Params("id") != userID {
            return c.Status(403).SendString("Forbidden")
        }
        
        var updateData map[string]interface{}
        if err := c.BodyParser(&updateData); err != nil {
            return c.Status(400).SendString("Invalid data")
        }
        
        if err := db.UpdateUser(userID, updateData); err != nil {
            return c.Status(500).SendString("Update failed")
        }
        
        return c.SendStatus(204)
    })

    app.Listen(":3000")
}

For administrative endpoints, use role-based access control with Fiber's middleware chaining:

func requireAdminRole() fiber.Handler {
    return func(c *fiber.Ctx) error {
        claims := c.Locals("user").(*jwt.Token).Claims.(*jwt.RegisteredClaims)
        // Assuming roles are stored in the token's claims
        roles := claims.CustomClaims["roles"].([]interface{})
        
        for _, role := range roles {
            if role == "admin" {
                return c.Next()
            }
        }
        return c.Status(403).SendString("Admin access required")
    }
}

// Apply multiple middleware layers
app.Post("/api/admin/shutdown", requireAdminRole(), func(c *fiber.Ctx) error {
    return shutdownSystem()
})

For webhook endpoints, implement signature verification:

app.Post("/api/webhooks/payment", func(c *fiber.Ctx) error {
    signature := c.Get("webhook-signature")
    payload := new(PaymentPayload)
    
    if err := c.BodyParser(payload); err != nil {
        return c.Status(400).SendString("Invalid payload")
    }
    
    if !verifyWebhookSignature(signature, payload) {
        return c.Status(401).SendString("Invalid signature")
    }
    
    processPayment(payload)
    return c.SendStatus(200)
})

Integrating middleBrick into your development workflow helps catch missing authentication before deployment:

# .github/workflows/security.yml
name: Security Scan
on: [push, pull_request]

jobs:
  security:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Run middleBrick Scan
        run: |
          npm install -g middlebrick
          middlebrick scan ${{ secrets.API_URL }} --output=html --report=security-report.html
      - name: Upload Report
        uses: actions/upload-artifact@v3
        with:
          name: security-report
          path: security-report.html

This GitHub Action runs middleBrick scans on every code change, ensuring authentication gaps are caught early in the development cycle.