Fix BFLA (Broken Function Level Authorization) in Revel
BFLA occurs when an application fails to verify if a user has the appropriate privileges to access a specific function or administrative endpoint. In the Revel framework, developers often rely on 'hidden' UI elements to restrict access, but fail to enforce these restrictions on the server side. To secure a Revel app, you must implement robust role-based access control (RBAC) using Interceptors to validate user claims before the controller logic executes.
The Vulnerable Pattern
package controllersimport “github.com/revel/revel”
type Admin struct { *revel.Controller }
// VULNERABLE: This endpoint is accessible to any authenticated user // who knows the URL. No server-side role check is performed. func (c Admin) DeleteUser(id int) revel.Result { // Logic to delete user from DB // db.Exec(“DELETE FROM users WHERE id = ?”, id) return c.RenderJSON(map[string]string{“status”: “success”, “message”: “User deleted”}) }
The Secure Implementation
The vulnerability stems from an implicit trust in the client's request. The fix utilizes Revel's 'InterceptMethod' to inject an authorization layer. By registering 'CheckAdmin' as a 'revel.BEFORE' interceptor, we ensure that the session's 'role' claim is validated against the required 'admin' privilege before the 'DeleteUser' function is even reached. If the check fails, a 403 Forbidden response is returned, effectively blocking unauthorized function-level access.
package controllersimport “github.com/revel/revel”
type Admin struct { *revel.Controller }
// SECURE: Interceptor to enforce Authorization func (c Admin) CheckAdmin() revel.Result { role, err := c.Session.Get(“role”) if err != nil || role != “admin” { return c.Forbidden(“Insufficient privileges.”) } return nil }
func init() { // Register the interceptor to run BEFORE any Admin controller methods revel.InterceptMethod(Admin.CheckAdmin, revel.BEFORE) }
func (c Admin) DeleteUser(id int) revel.Result { // Business logic is now protected by the interceptor return c.RenderJSON(map[string]string{“status”: “success”}) }
Your Revel API
might be exposed to BFLA (Broken Function Level Authorization)
74% of Revel apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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