Clickjacking in Gorilla Mux

Clickjacking attacks exploit the trust users have in legitimate websites by tricking them into clicking on hidden or disguised elements. In Gorilla Mux applications, this vulnerability typically manifests through improper handling of HTTP headers that control frame embedding behavior.

The core mechanism involves an attacker creating a malicious page that loads your Gorilla Mux application inside an invisible iframe. Users believe they're interacting with the attacker's page, but their clicks are actually being transmitted to your application. This is particularly dangerous for applications with administrative interfaces or sensitive operations.

In Gorilla Mux, clickjacking vulnerabilities often arise from missing or misconfigured X-Frame-Options headers. Consider this vulnerable handler:

func sensitiveOperation(w http.ResponseWriter, r *http.Request) {
    // No frame protection headers set
    fmt.Fprintf(w, "Performing sensitive operation...")
}

router := mux.NewRouter()
router.HandleFunc("/admin", sensitiveOperation)
http.ListenAndServe(":8080", router)

This handler is vulnerable because browsers have no indication that this endpoint shouldn't be embedded in frames. An attacker could create a page with CSS like:

<div style="overflow: hidden; width: 100px; height: 100px;">
  <iframe src="http://your-app.com/admin" style="transform: scale(2);"></iframe>
</div>

Additionally, Gorilla Mux applications may be vulnerable through CORS misconfigurations. If your application allows cross-origin requests without proper restrictions, attackers can craft sophisticated clickjacking attacks that combine frame embedding with forged requests.

Another manifestation involves dynamic content loading where Gorilla Mux handlers serve different content based on authentication state but fail to set frame protection headers consistently. This creates a scenario where unauthenticated users can be framed, then the application loads authenticated content within that frame.

Detecting clickjacking vulnerabilities in Gorilla Mux applications requires examining both the HTTP response headers and the application's routing logic. The primary indicator is the absence of X-Frame-Options or Content-Security-Policy frame-ancestors directives in responses from sensitive endpoints.

Using middleBrick's CLI tool, you can scan your Gorilla Mux application for clickjacking vulnerabilities:

npx middlebrick scan http://localhost:8080/admin

# Or integrate into your testing pipeline
middlebrick scan --output json http://your-app.com/api/v1/*

middleBrick specifically tests for frame embedding vulnerabilities by attempting to load your endpoints in iframes and checking for protective headers. The scanner examines all endpoints, including those with dynamic routing patterns that Gorilla Mux handles through its path variable system.

For manual verification, you can use curl to check response headers:

curl -I http://localhost:8080/admin

# Look for these headers:
# X-Frame-Options: DENY or SAMEORIGIN
# Content-Security-Policy: frame-ancestors 'none' or 'self'

Gorilla Mux's middleware system provides a centralized location to add clickjacking protection. You should verify that all handlers, including those added through subrouters or route groups, inherit the protection middleware.

Another detection method involves testing with browser developer tools. Open your application in an iframe and inspect the network requests to verify that sensitive endpoints return appropriate frame protection headers regardless of the request context.

Remediating clickjacking vulnerabilities in Gorilla Mux applications involves implementing proper frame protection at the middleware level. The most effective approach uses Gorilla Mux's middleware chain to ensure consistent header application across all routes.

package main

import (
    "net/http"
    "github.com/gorilla/mux"
)

// ClickjackingProtection middleware
func ClickjackingProtection(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // Set X-Frame-Options to DENY all framing
        w.Header().Add("X-Frame-Options", "DENY")
        
        // Alternative: allow same-origin framing only
        // w.Header().Add("X-Frame-Options", "SAMEORIGIN")
        
        // Modern alternative using CSP
        w.Header().Add("Content-Security-Policy", "frame-ancestors 'none'")
        
        next.ServeHTTP(w, r)
    })
}

func main() {
    router := mux.NewRouter()
    
    // Apply clickjacking protection to all routes
    router.Use(ClickjackingProtection)
    
    // Public routes
    router.HandleFunc("/", homeHandler)
    router.HandleFunc("/login", loginHandler)
    
    // Protected routes
    adminRouter := router.PathPrefix("/admin").Subrouter()
    adminRouter.HandleFunc("/dashboard", adminDashboard)
    adminRouter.HandleFunc("/settings", adminSettings)
    
    http.ListenAndServe(":8080", router)
}

func homeHandler(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Public home page"))
}

func loginHandler(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Login page"))
}

func adminDashboard(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Admin dashboard"))
}

func adminSettings(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("Admin settings"))
}

This implementation ensures that every response from your Gorilla Mux application includes clickjacking protection headers. The middleware approach is superior to adding headers in individual handlers because it prevents accidental omissions and maintains consistency.

For applications that need to allow framing on certain pages (like public documentation), you can create conditional middleware:

func ConditionalClickjackingProtection(allowFraming bool) mux.MiddlewareFunc {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            if allowFraming {
                // Only set CSP without frame-ancestors restriction
                w.Header().Add("Content-Security-Policy", "default-src 'self'")
            } else {
                w.Header().Add("X-Frame-Options", "DENY")
                w.Header().Add("Content-Security-Policy", "frame-ancestors 'none'")
            }
            next.ServeHTTP(w, r)
        })
    }
}

// Apply to specific routes
publicRouter := router.PathPrefix("/docs").Subrouter()
publicRouter.Use(ConditionalClickjackingProtection(true))
publicRouter.HandleFunc("/", docsHandler)

Remember to test your implementation thoroughly. Use middleBrick's continuous monitoring to ensure your clickjacking protections remain effective as your application evolves.