If you are not already familiar with the concept of Privilege Escalation, we suggest that you review the article entitled “What Is Privilege Escalation ?“.
For insights into how to detect Privilege Escalation vulnerabilities, please see the article entitled “How To Test For Privilege Escalation“.
Since Privilege Escalation vulnerabilities are the result of the failure to verify that the user has the authority to perform a requested action, prevention boils down to verifying permissions.
Checking Permission By Role
The application must know what role (or roles) the current user is associated with as well as what commands, actions, or requests they can submit. Note that this is a positive (whitelist) model that represents a “deny by default” design approach. Simply put, if a permission is not listed, then it is not available.
Application permissions can be thought of as a “role/permissions matrix”:
|Perm 1||Perm 2||…||Perm N|
Where each role represents a “class” of user enjoying a common set of permissions, and each permission represents a potential command, request, or action that a user might potentially initiate. The presence of an ‘X’ would indicate the role enjoys the permission whereas the absence of an ‘X’ would indicate the absence of that permission.
The above “role/permissions matrix” would be accompanied by a mapping of user accounts to roles (i.e. a users/roles matrix):
|Role 1||Role 2||…||Role N|
Where each user is identified as being associated with one or more roles.
Now when a user submits a command, request, or action to the application, the application need only check whether the permission is granted for one of the roles associated with that user.
Even with properly implemented permissions checking, it is still possible to “drop the ball” in other ways. Clearly, the role/permissions matrix and user/roles matrix should be configurable outside the application and stored in a secure manner with role-based access control. The insecure storage of the role. permission, or user information used by the application can render permissions checking a moot point. Also, any misconfiguration of that same information can lead to Privilege Escalation, even if the application itself is properly checking permissions.
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