COSEM Class 15 (Association LN): Access Rights & Attribute Level Security

[alex_turner]

Managing Role-Based Access Control (RBAC) in Smart Meters

Class 15 (Association LN) defines which objects and methods an authenticated client can access.

object_list Structure (Attribute 2)

Each entry in the Association View contains:

Structure {
    class_id: Long-Unsigned (e.g. 3 for Register),
    version: Unsigned (e.g. 0),
    logical_name: Octet-String (e.g. 1.0.32.7.0.255),
    access_rights: Structure {
        attribute_access: Array of {
            attribute_id: Integer8,
            access_mode: Enum (0=No Access, 1=Read Only, 2=Write Only, 3=Read/Write),
            access_selectors: Array of Integer8
        },
        method_access: Array of {
            method_id: Integer8,
            access_mode: Enum (0=No Access, 1=Access Allowed)
        }
    }
}

If a Management client attempts to execute SET on a billing register that is marked as Read Only in its Association LN, the meter returns Data-Access-Result: read-write-denied (Code 3).

[david_miller]

Always fetch the complete Association LN (0.0.40.0.X.255) right after login to dynamically discover which OBIS objects and methods your client credentials are permitted to invoke.