Improving Web Application Security: Threats and - CGISecurity

382 Part III: Building Secure Web ApplicationsRestrict Unauthorized CallersYou code should authorize users based on a role or identity before it connects to thedatabase. Role checks are usually used in the business logic of your application, but ifyou do not have a clear distinction between business and data access logic, useprincipal permission demands on the methods that access the database.The following attribute ensures that only users who are members of the Manager rolecan call the DisplayCustomerInfo method:[PrincipalPermissionAttribute(SecurityAction.Demand, Role="Manager")]public void DisplayCustomerInfo(int CustId){}If you need additional authorization granularity and need to perform role-based logicinside the data access method, use imperative principal permission demands orexplicit role checks as shown in the following code fragment:using System.Security;using System.Security.Permissions;public void DisplayCustomerInfo(int CustId){try{// Imperative principal permission role check to verify that the caller// is a managerPrincipalPermission principalPerm = new PrincipalPermission(null, "Manager");// Code that follows is only executed if the caller is a member// of the "Manager" role}catch( SecurityException ex ){. . .}}The following code fragment uses an explicit, programmatic role check to ensure thatthe caller is a member of the Manager role:public void DisplayCustomerInfo(int CustId){if(!Thread.CurrentPrincipal.IsInRole("Manager")){. . .}}