Man In The Middle in Buffalo with Api Keys

A Man In The Middle (MitM) scenario in Buffalo using API keys occurs when an attacker intercepts traffic between a client and a Buffalo-based API endpoint. If requests rely on static API keys passed in headers without transport-layer protections, an attacker on a shared or compromised network can observe and replay those keys. This risk is elevated when TLS is not enforced consistently or when clients accidentally send keys to non-HTTPS endpoints.

Buffalo applications often expose API routes that accept keys via headers (e.g., X-API-Key). If these routes are reachable over HTTP, or if a reverse proxy or load balancer terminates TLS inconsistently, an attacker positioned between the client and server can capture the key. Once obtained, the attacker can impersonate legitimate services or escalate unauthorized actions across the API surface. This aligns with common OWASP API Top 10 risks such as broken object level authorization when combined with weak transport security.

Additionally, if the Buffalo application embeds API keys in JavaScript bundles or logs request headers without redaction, the keys may leak further through client-side code or log exposure. MiddleBrick scans detect these exposures by testing unauthenticated attack surfaces and flagging endpoints that transmit sensitive identifiers like API keys without adequate encryption or validation controls.

Remediation focuses on ensuring API keys are never transmitted in cleartext and are validated on each request. Use HTTPS for all routes, enforce strict header handling, and avoid logging keys. Below are concrete examples using Buffalo’s idioms.

Enforce HTTPS and secure headers

Ensure your Buffalo app redirects HTTP to HTTPS and sets secure headers. In actions/app.go, configure the app with secure options:

// actions/app.go
package actions

import (
	"github.com/gobuffalo/buffalo"
	"github.com/gobuffalo/buffalo/middleware"
)

func App() *buffalo.App {
	app := buffalo.New(buffalo.Options{
		Env:         ENV,
		SessionStore: &middleware.SessionCookieStore{},
		PreWares: []buffalo.PreWare{
			middleware.Secure,
		},
	})

	// Force HTTPS in production
	if ENV == buffalo.EnvProduction {
		app.Use(middleware.ForceSSL)
	}

	return app
}

Validate API keys via middleware without logging them

Create a custom middleware that checks the presence and validity of an API key without echoing it in logs. Place this in actions/middleware/api_key.go:

// actions/middleware/api_key.go
package middleware

import (
	"net/http"

	"github.com/gobuffalo/buffalo"
)

func APIKeyValidator(next buffalo.Handler) buffalo.Handler {
	return func(c buffalo.Context) error {
		key := c.Request().Header.Get("X-API-Key")
		if key == "" {
			c.Response().WriteHeader(http.StatusUnauthorized)
			return c.Render(401, r.JSON(map[string]string{"error": "missing api key"}))
		}
		// Validate against a secure store (e.g., environment variable or vault)
		valid := validateKey(key)
		if !valid {
			c.Response().WriteHeader(http.StatusForbidden)
			return c.Render(403, r.JSON(map[string]string{"error": "invalid api key"}))
		}
		// Ensure the key is not logged
		c.Set("api_key_valid", true)
		return next(c)
	}
}

func validateKey(key string) bool {
	// Replace with secure lookup, e.g., constant-time compare against env
	expected := "super-secret-key"
	return subtleCompare(key, expected)
}

// subtleCompare avoids timing attacks
func subtleCompare(a, b string) bool {
	if len(a) != len(b) {
		return false
	}
	var equal byte
	for i := 0; i < len(a); i++ {
		equal |= a[i] ^ b[i]
	}
	return equal == 0
}

Register middleware and protect routes

In your route definitions, apply the middleware to sensitive endpoints only, avoiding unnecessary overhead:

// actions/app.go continued
func App() *buffalo.App {
	app := buffalo.New(buffalo.Options{ /* ... */ })

	// Apply globally or selectively
	app.Use(middleware.Secure)
	if ENV == buffalo.EnvProduction {
		app.Use(middleware.ForceSSL)
	}

	// Apply API key validation to protected routes
	api := app.Group("/api")
	api.Use(middleware.APIKeyValidator)
	{
		api.Get("/data", dataHandler)
		api.Post("/update", updateHandler)
	}

	return app
}

Rotate keys and avoid client-side embedding

Do not embed API keys in JavaScript or HTML. Instead, use short-lived tokens issued by an authentication service. Configure your CI/CD to rotate keys regularly and store them in environment variables or a secrets manager, never in version control.

These steps reduce the attack surface for MitM when API keys are in use and align with secure Buffalo application practices.