Arp Spoofing in Buffalo with Bearer Tokens

Arp Spoofing is a Layer 2 attack where an attacker sends falsified ARP messages onto a local network to associate their MAC address with the IP address of a legitimate host, such as a gateway or another API server. In Buffalo, a common Go web framework, this attack is particularly relevant when APIs rely on Bearer Tokens for authentication over HTTP. Bearer Tokens are typically passed in the Authorization header (e.g., Authorization: Bearer <token>). If an attacker performs Arp Spoofing between a client and the server hosting a Buffalo API, they can intercept and modify unencrypted HTTP traffic. Because the Authorization header is not encrypted at the link layer, the attacker can capture or alter the token in transit. This risk is elevated in Buffalo applications that do not enforce HTTPS for all endpoints, or that inadvertently allow HTTP for convenience during development. The token itself becomes exposed to interception, enabling session hijacking or unauthorized API access. Note that middleBrick scans test unauthenticated attack surfaces and include checks for encryption and insecure transport, which can surface missing TLS enforcement as a finding.

To mitigate Arp Spoofing risks when using Bearer Tokens in Buffalo, enforce HTTPS for all requests and avoid transmitting tokens over unencrypted channels. Use secure cookies with the Secure and HttpOnly flags only when tokens are not required in headers; for API token-based auth, ensure TLS is mandatory. Below are concrete code examples for a Buffalo application that enforce HTTPS and validate secure token handling.

1. Enforce HTTPS in Buffalo

Use middleware to redirect HTTP to HTTPS and ensure secure transport. This reduces the risk of token interception via Arp Spoofing on local or untrusted networks.

// app/middleware/secure_redirect.go
package middleware

import (
	"net/http"
)

// SecureRedirect ensures all requests use HTTPS.
func SecureRedirect(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if r.TLS == nil {
			http.Redirect(w, r, "https://"+r.Host+r.RequestURI, http.StatusMovedPermanently)
			return
		}
		next.ServeHTTP(w, r)
	})
}

Then apply this middleware globally in app.go:

// app/app.go
func (a *App) Initialize() {
	a.Use(middleware.SecureRedirect)
	// other middleware and routes
}

2. Use Bearer Tokens over HTTPS only

Ensure API endpoints validate the presence of Bearer Tokens and reject requests without TLS. Below is a simple authentication check applied to a Buffalo route group.

// app/controllers/api_controller.go
package controllers

import (
	"net/http"
	"strings"
)

// RequireBearerAuth is a middleware that checks for a valid Bearer token.
func RequireBearerAuth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		auth := r.Header.Get("Authorization")
		if auth == "" || !strings.HasPrefix(auth, "Bearer ") {
			http.Error(w, "Unauthorized", http.StatusUnauthorized)
			return
		}
		// Optionally validate token against a store or introspection endpoint
		token := strings.TrimPrefix(auth, "Bearer ")
		if !isValidToken(token) {
			http.Error(w, "Forbidden", http.StatusForbidden)
			return
		}
		next.ServeHTTP(w, r)
	})
}

// isValidToken performs a check (e.g., against a database or JWT validation).
func isValidToken(token string) bool {
	// Implement actual validation logic here
	return token == "expected-secure-token"
}

Apply this middleware to sensitive routes in your Buffalo application:

// app/controllers/api_controller.go
func (v *ApiController) MountedRoutes() http.Handler {
	g := v.Group("/api/v1")
	g.Use(controllers.RequireBearerAuth)
	g.GET("/secure-data", controllers.SecureData)
	return g
}

3. Additional recommendations

• Always serve APIs over TLS (e.g., terminate TLS at a load balancer or reverse proxy with valid certificates).
• Set the Secure flag on any cookies that might carry session identifiers, and prefer short-lived access tokens.
• Use HTTP Strict Transport Security (HSTS) headers to instruct browsers to only use HTTPS.

These steps reduce the attack surface for token interception via Arp Spoofing. Note that middleBrick scans can verify whether your Buffalo API enforces HTTPS and transmits Bearer Tokens securely, providing findings and remediation guidance aligned with frameworks like OWASP API Security.