Fix BFLA (Broken Function Level Authorization) in Chi
BFLA (Broken Function Level Authorization) in Go's Chi router occurs when sensitive endpoints are exposed without verifying the caller's specific permissions or roles. It is not enough to check if a user is authenticated; you must verify they are authorized to invoke that specific function. In a typical Chi setup, developers often forget to apply role-based middleware to administrative route groups, allowing any logged-in user to perform high-privilege actions.
The Vulnerable Pattern
func main() { r := chi.NewRouter() r.Use(middleware.Logger) r.Use(AuthMiddleware) // Generic authentication check// VULNERABLE: Any authenticated user can hit this r.Delete("/api/v1/users/{id}", DeleteUserHandler)}
func AuthMiddleware(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { // Only checks if a token is valid, not what the user can do token := r.Header.Get(“Authorization”) if !isValid(token) { http.Error(w, “Unauthorized”, 401) return } next.ServeHTTP(w, r) }) }
The Secure Implementation
To mitigate BFLA, you must implement granular authorization checks. The secure implementation uses Chi's 'r.Route' to group privileged functions and applies an 'AdminOnly' middleware. This middleware extracts the user's role from the request context (populated during authentication) and explicitly validates that the user possesses the 'ADMIN' role before allowing the request to reach the 'DeleteUserHandler'. This ensures that even if an attacker knows the URL, they cannot execute the function without the correct privilege level.
func AdminOnly(next http.Handler) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { user := r.Context().Value("user").(*UserClaims) if user.Role != "ADMIN" { http.Error(w, "Forbidden: Admin access required", 403) return } next.ServeHTTP(w, r) }) }func main() { r := chi.NewRouter() r.Use(AuthMiddleware)
// SECURE: Function level authorization enforced via middleware grouping r.Route("/api/v1/admin", func(r chi.Router) { r.Use(AdminOnly) r.Delete("/users/{id}", DeleteUserHandler) })
}
Your Chi API
might be exposed to BFLA (Broken Function Level Authorization)
74% of Chi apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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