Something about user access control or security control design

Below is a few strategy to implement the user access control or the security feature in your application.

1. The simplest design will be user name + password and stores these information in a database table. No control over the feature accessibility.
2. One level harder will be using one security "action" to treat as one permission. And one security action represent a menu option, button, input field, display field or a process to be executed. This design requires 1 user class and a collection of permitted/allowed security actions. So, you need two database tables to stores the information. For example, user A allows issuing and editing invoice but not deleting any invoice. In this case, you will have 3 allowed actions (or record) for user A.
3. In case you feel that having one security action mapping to the feature is cumbersome and require lots of hard space, you may consider adding a flag field in the security action. For example, "Invoice" action will have 3 flags: issue, edit and delete where the "flag" is in BIT data type (in MSSQL database). If the flag value is "1" means permitted and "0" means not permitted.
4. Some applications requires another level of sophistication - that is using "user level" in conjunction with the security actions.
5. Another kind of implementation is to have write level (0-10) and read level (0-10). Both values are use in conjunction with the menu option and input fields. For example, the credit limit field for the customer has read level of "5" and write level of "8". If the user's read level is "5" and the user will be able to view the credit limit field. If the user's write level is also "5", then, this credit limit value will be disabled from editing. 

So, which one is better? It's all depend on your need. As for us, we prefer #2 due to easier to implement and future enhancement. It's also very easy to cater for changes.

Let's assume that you read the previous article, the CUser class will have a CanAccess() method which returns true or false. The application should check the result of this method before performing the process/action whereas CUser class.

Different flavor of CanAccess()

• bool CanAccess(Guid action_id)
• bool CanAccess(Guid action_id, PermissionEnum permission) [PermissionEnum {insert, update, delete, select]
• bool CanAccess(Guid action_id, int user_level)
• bool CanAccess(int read_level, int write_level)