Privilege Escalation in Chi

In Go applications that use the chi router (github.com/go-chi/chi/v5), privilege escalation often appears when a handler that should be restricted to a privileged role (e.g., admin) is reachable without proper authorization checks. Because chi focuses on routing and middleware composition, developers sometimes rely on route‑level middleware to enforce authentication but forget to add role‑based checks inside the handler or in a dedicated authorization middleware.

Consider a typical API that exposes administrative actions under the /admin/* subtree. A route group might be created with a global authentication middleware that verifies a JWT and stores the user’s claims in the request context:

r := chi.NewRouter()
r.Use(authMiddleware) // validates token, sets ctx.Value("user", claims)

r.Route("/admin", func(r chi.Router) {
    r.Get("/users", listAllUsers)   // intended for admins only
    r.Post("/users", createUser)   // intended for admins only
})

If listAllUsers or createUser does not inspect the user claim for a role such as "role":"admin", any authenticated user—regardless of their actual privileges—can invoke these endpoints. An attacker who has obtained a valid token for a regular user can therefore escalate to administrative capabilities, a classic BFLA (Broken Function Level Authorization) scenario mapped to OWASP API Top 10 2023 API1:2023 – Broken Object Level Authorization (though the principle is the same for function‑level).

Another Chi‑specific pattern emerges when developers use chi.URLParam to extract identifiers and then directly use them in database queries without verifying that the identifier belongs to the acting user. For example:

r.Get("/orders/{orderID}", func(w http.ResponseWriter, r *http.Request) {
    orderID := chi.URLParam(r, "orderID")
    // No check that the order belongs to ctx.Value("user").ID
    order, err := db.GetOrder(orderID)
    // …
})

Here, a user can enumerate or modify orders belonging to other users, which is an IDOR (Object Level) issue that often co‑occurs with privilege escalation when the same missing check permits administrative actions on resources owned by others.

Remediating privilege escalation in a Chi application involves adding explicit authorization checks either as middleware or directly inside handlers. The goal is to verify that the authenticated user’s role (or any other attribute) satisfies the privilege required for the requested operation.

One clean approach is to create a role‑based middleware that extracts the user claims from the context (set by your authentication middleware) and rejects the request if the required role is missing:

func requireRole(role string) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            userCtx := r.Context().Value("user")
            if userCtx == nil {
                http.Error(w, "unauthenticated", http.StatusUnauthorized)
                return
            }
            claims, ok := userCtx.(map[string]interface{})
            if !ok {
                http.Error(w, "invalid user context", http.StatusInternalServerError)
                return
            }
            userRole, ok := claims["role"].(string)
            if !ok || userRole != role {
                http.Error(w, "forbidden", http.StatusForbidden)
                return
            }
            next.ServeHTTP(w, r)
        })
    }
}

Then apply this middleware to the admin route group:

r.Route("/admin", func(r chi.Router) {
    r.Use(requireRole("admin"))
    r.Get("/users", listAllUsers)
    r.Post("/users", createUser)
})

For IDOR‑style protection, augment the handler to compare the resource identifier with the user’s identity:

r.Get("/orders/{orderID}", func(w http.ResponseWriter, r *http.Request) {
    userCtx := r.Context().Value("user").(map[string]interface{})
    userID := userCtx["id"].(string)
    orderID := chi.URLParam(r, "orderID")

    order, err := db.GetOrder(orderID)
    if err != nil {
        http.Error(w, "order not found", http.StatusNotFound)
        return
    }
    if order.UserID != userID {
        http.Error(w, "forbidden", http.StatusForbidden)
        return
    }
    // proceed with returning the order
    json.NewEncoder(w).Encode(order)
})

These patterns use only Chi’s native features—chi.Router, chi.URLParam, and the standard context package—so they introduce no external dependencies and keep the codebase idiomatic.

After applying the fixes, re‑run middleBrick (via CLI, GitHub Action, or the Dashboard) to verify that the privilege‑escalation findings disappear and the security score improves.