Permission Denied

2018/05/28

NetAuth is providing authentication and authorization as a service, but what provides the authorization info to NetAuth for internal actions? Clearly the server can authenticate random users no problem, since after all is has the information to do that on behalf of other clients.

Internal authorization is done in a few ways, either via admin groups or via capabilities.

Admin Groups

Admin groups are, as the name implies, groups with administrative powers. They don’t have power over the entire server, just over specific groups. The idea is that you can have an admin group and point to it from other groups and say “the membership of this group can be managed by that admin group over there” and those entities will be allowed to add and remove other entities from this group.

Admin groups can additionally modify all other metadata on a group including its expansions, the displayed name, and other similar fields.

Capabilities

Capabilities are the other system of authorization within NetAuth. Capabilities gate the access to do broad actions on the server and should not be conferred without careful consideration of the security implications. Capabilities grant the ability to do things like creating and removing objects on the server, changing entity secrets, and even granting more capabilities.

Capabilities can be assigned to either entities directly or groups, though preference should be to assign to a group. This is so that when an entity is added to a role as defined by a group, they gain the appropriate powers associated with that role. Extreme caution should be taken when using expansion rules on groups that have capabilities assigned to them as this can lead to everyone in the server suddenly gaining root authority.

Capabilities are granular and are checked for individually on the actions that require them, with one exception. There is a top level capability that is called “GLOBAL_ROOT” which short-circuits the check logic and will always authorize any action. The “GLOBAL_ROOT” power is also required to be able to assign other capabilities. Since this creates a sort of chicken-and-egg problem, the server itself can assign this capability when launched with special options.