Improving Web Application Security: Threats and - CGISecurity

132 Part III: Building Secure Web ApplicationsFigure 6.1 shows a logical view of how user security is typically used in a Webapplication to restrict user access to Web pages, business logic, operations, and dataaccess.What can the user do?(Authorization)Who is the user?(Authentication)User Store(SAM, ActiveDirectory or SQLServer)Role-Based SecurityUserWeb PagesBusiness LogicOperationsData AccessWeb ApplicationFigure 6.1A logical view of (user) role-based securityCode Access SecurityCode access security authorizes code when it attempts to access secured resources,such as the file system, registry, network, and so on, or when it attempts to performother privileged operations, such as calling unmanaged code or using reflection.Code access security is an important additional defense mechanism that you can useto provide constraints on a piece of code. An administrator can configure code accesssecurity policy to restrict the resource types that code can access and the otherprivileged operations it can perform. From a Web application standpoint, this meansthat in the event of a compromised process where an attacker takes control of a Webapplication process or injects code to run inside the process, the additional constraintsthat code access security provides can limit the damage that can be done.Figure 6.2 shows a logical view of how code access security is used in a Webapplication to constrain the application’s access to system resources, resources ownedby other applications, and privileged operations, such as calling unmanaged code.