Arp Spoofing in Fiber

Arp Spoofing in Fiber applications typically emerges through insecure WebSocket connections and improper authentication handling. Fiber's WebSocket implementation, while powerful, can become vulnerable when developers fail to validate client identities before establishing persistent connections.

A common attack pattern involves an adversary intercepting WebSocket upgrade requests and injecting malicious payloads during the handshake phase. Consider this vulnerable Fiber WebSocket handler:

app := fiber.New()

The above code creates an open WebSocket endpoint without any authentication or origin validation. An attacker can exploit this by:

• Intercepting the WebSocket upgrade request and injecting malicious scripts
• Spoofing client identities to gain unauthorized access to protected resources
• Maintaining persistent connections to monitor traffic patterns
• Performing man-in-the-middle attacks on WebSocket frames

Another manifestation occurs in Fiber's middleware chain. When authentication middleware is improperly configured or bypassed, attackers can exploit the session management system. Here's a vulnerable pattern:

app.Use(middleware.JWT(&middleware.JWTConfig{
    SigningKey: []byte("weak-secret"),
})

The weak signing key allows attackers to forge JWT tokens and impersonate legitimate users. Combined with ARP spoofing techniques, this enables session hijacking across the network layer.

Real-world incidents have shown ARP spoofing attacks targeting Fiber applications in corporate environments, where attackers use tools like arpspoof to intercept traffic between clients and Fiber API servers, then exploit authentication weaknesses to gain administrative access.

Detecting ARP spoofing vulnerabilities in Fiber applications requires a multi-layered approach. The middleBrick API security scanner excels at identifying these specific issues through its comprehensive testing methodology.

middleBrick's scanner tests Fiber applications for ARP spoofing-related vulnerabilities by examining:

• WebSocket endpoint authentication mechanisms
• Middleware chain integrity and authentication bypass possibilities
• Session management security
• Input validation on upgrade requests
• Origin header validation

Here's how to scan your Fiber application using middleBrick's CLI:

middlebrick scan https://your-fiber-app.com/api

The scanner performs 12 parallel security checks, including authentication bypass testing and input validation analysis. For WebSocket-specific vulnerabilities, middleBrick examines the upgrade handshake process and looks for missing authentication layers.

Additional detection methods include:

app.Use(middleware.JWT(&middleware.JWTConfig{
    SigningKey: []byte("your-secret"),
    ValidationKeyGetter: func(token *jwt.Token) (interface{}, error) {
        return []byte("your-secret"), nil
    },
    SigningMethod: jwt.SigningMethodHS256,
})

Implementing proper JWT validation helps detect if attackers can forge tokens. middleBrick's scanner will flag weak signing methods and missing validation layers.

For WebSocket security, middleBrick checks if your implementation includes:

ws := app.Group("/ws")
ws.Use(middleware.JWT(...))
ws.Get("/connect", func(c *fiber.Ctx) error {
    // Validate origin
    origin := c.Get("Origin")
    if origin != "https://yourdomain.com" {
        return c.Status(fiber.StatusForbidden).SendString("Invalid origin")
    }
    return c.JSON(fiber.Map{"status": "connected"})
})

middleBrick's LLM/AI security module also scans for prompt injection vulnerabilities that could be exploited in conjunction with ARP spoofing attacks, particularly in applications using AI features.

Remediating ARP spoofing vulnerabilities in Fiber applications requires implementing robust authentication, input validation, and secure communication protocols. Here are Fiber-specific remediation strategies:

1. Implement Strong WebSocket Authentication:

app.Use(middleware.JWT(&middleware.JWTConfig{
    SigningKey: []byte("strong-256-bit-secret"),
    ValidationKeyGetter: func(token *jwt.Token) (interface{}, error) {
        return []byte("strong-256-bit-secret"), nil
    },
    SigningMethod: jwt.SigningMethodHS256,
    ContextKey: "user",
})

2. Add Origin Validation:

app.Use(func(c *fiber.Ctx) error {
    if c.Method() == "OPTIONS" {
        return c.Next()
    }
    origin := c.Get("Origin")
    allowedOrigins := []string{
        "https://yourdomain.com",
        "https://yourapp.com",
    }
    for _, allowed := range allowedOrigins {
        if allowed == origin {
            return c.Next()
        }
    }
    return c.Status(fiber.StatusForbidden).SendString("Origin not allowed")
})

3. Secure WebSocket Connections:

app.Get("/ws/connect", func(c *fiber.Ctx) error {
    // Verify JWT token exists
    token := c.Locals("user")
    if token == nil {
        return c.Status(fiber.StatusUnauthorized).SendString("Authentication required")
    }
    
    // Validate client IP against known good IPs
    clientIP := c.IP()
    if !isValidIP(clientIP) {
        return c.Status(fiber.StatusForbidden).SendString("Invalid client IP")
    }
    
    return c.JSON(fiber.Map{"status": "authorized"})
})

4. Implement Rate Limiting:

app.Use(middleware.RateLimit(&middleware.RateLimitConfig{
    Filter: func(c *fiber.Ctx) bool {
        // Apply rate limiting to WebSocket upgrade requests
        return c.Path() == "/ws/connect"
    },
    Timeout: 60, // seconds
    Limit: 10,   // requests
    KeyGenerator: func(c *fiber.Ctx) string {
        return c.IP()
    },
}))

5. Use HTTPS Everywhere:

app.Use(func(c *fiber.Ctx) error {
    if !c.Protocol() == "https" {
        return c.Status(fiber.StatusForbidden).SendString("HTTPS required")
    }
    return c.Next()
})

6. Add Request Validation:

app.Use(func(c *fiber.Ctx) error {
    // Validate Content-Type for WebSocket upgrades
    if c.Get("Upgrade") == "websocket" {
        if c.Get("Sec-WebSocket-Key") == "" {
            return c.Status(fiber.StatusBadRequest).SendString("Invalid WebSocket request")
        }
    }
    return c.Next()
})

For comprehensive protection, integrate middleBrick's continuous monitoring into your CI/CD pipeline using the GitHub Action:

- name: Run middleBrick Security Scan
  uses: middlebrick/middlebrick-action@v1
  with:
    url: https://your-fiber-app.com/api
    fail-on-severity: high

This ensures ARP spoofing vulnerabilities are caught before deployment. The Pro plan's continuous monitoring will automatically scan your staging APIs on a configurable schedule, alerting you to any new vulnerabilities that emerge.