Lab 3: Access Control

Access Control

In lecture, we covered the idea of protection states and access control matrices, as well as the Bell-LaPadula Confidentiality Model.

In today’s lab, you’ll be completing challenges that exercise your understanding of the concepts.

Modifying ACMs

Recall that an access control matrix determines the “rights” or “permissions” that subjects in a system have over the objects.

Recall also that updates to an ACM can be done with commands that constitute protection state transitions.

Bell-LaPadula

Bell-LaPadula defines confidentiality according to a lattice of security clearances, characterized by the “dominance” relationship.

A clearance (𝐿, 𝐶) dom (𝐿^{'}, 𝐶^{'}) ⟺ 𝐿^{'} \leq 𝐿 \land 𝐶^{'} \subseteq 𝐶

At a high-level, according to Bell-LaPadula:

$𝑠 read 𝑜 ⟺ 𝑠 dom 𝑜$
$𝑠 write 𝑜 ⟺ 𝑜 dom 𝑠$

Biba

As we have noted in lecture, integrity policies are those that are concerned with the modification of data.

We will soon cover the Biba Model of integrity, which is also a lattice model and the dual of the Bell-LaPadula model.

In order to preserve the integrity of a high-integrity object, a lower integrity subject must not be able to write to it. (i.e. no writes up)

Likewise, a higher integrity subject should not rely on lower integrity object, lest the subject be compromised by relying on untrustworthy information. (i.e. no reads down)