Chapter 11, lesson 2: Using Declarative Security to Protect Assemblies.

Because CAS can restric permissions given to an app., you must write apps to run in a partially trusted security context.

Use declarative CAS demands - ensure that assm has all necessary permissions but none that it does not require.

Reasons to use CAS Assm Decl

• To ensure that the runtime will never run your app without granting access to all required resources - if user attempts to run app and CAS security policy does not grant a required permission, an exception is thrown. Use SecurityAction.RequestMinimum - to declare all CAS perms required by app.
• To create a sandbox for app to ensure an attacker does not manipulae it to access unintended resources - use CAS decl to reduce your assms

Classes for CAS Permissions

• For each type of resource (e.g. files/folders, printers, network access,...) that can be restricted by CAS there is a .NF class.
• Permission Attribute classes - inherit from CodeAccessSecurityAttribute class.
• Action property - specifies how the runtime will interpret the permission. Set to...
• 1) SecurityAction.RequestMinimum - requires a perm. for assm to run. If assm lacks specified perm then runtime throws exception.
• 2) SecurityAction.RequestOptional -
• 3) SecurityAction.RequestRefuse -
• NOTE: CAS is significant only for partially trusted assmebles. The runtime completely ignores CAS decl for fully trusted assemblies.
• combine RequestMinimum and RequestOptional - for non-negotiable permissions for 1 thing, but nothing else required.
• UIPermission, Unrestricted = true - for debugging + RequestOptional.