Lecture 9: October 14, 2019
Reading: C text, §5.3, 6.2, 6.4
Due: Lab 1, due October 18, 2019; Homework 2, due October 21, 2019
- Greetings and felicitations!
- Puzzle of the Day
- Declassification problem
- Strong tranquility
- Weak tranquility
- Requirements of integrity models
- Biba Model (strict integrity policy)
- Clark-Wilson Model
- Theme: military model does not provide enough controls for commercial fraud, etc. because it does not cover the right aspects of integrity
- Constrained Data Items (CDI) to which the model applies
- Unconstrained Data Items (UDIs) to which no integrity checks are applied
- Integrity Verification Procedures (IVP) that verify conformance to the integrity spec when IVP is run
- Transaction Procedures (TP) takes system from one well-formed state to another
- Clark-Wilson Certification and Enforcement Rules
- [C1] All IVPs must ensure that all CDIs are in a valid state when the IVP is run.
- [C2] All TPs must be certified to be valid, and each TP is associated with a set of CDIs it is authorized to manipulate.
- [E1] The system must maintain these lists and must ensure only those TPs manipulate those CDIs.
- [E2] The system must maintain a list of User IDs, TP, and CDIs that that TP can manipulate on behalf of that user, and must ensure only those executions are performed.
- [C3] The list of relations in E2 must be certified to meet the separation of duty requirement.
- [E3] The system must authenticate the identity of each user attempting to execute a TP.
- [C4] All TPs must be certified to write to an append-only CDI (the log) all information necessary to reconstruct the operation.
- [C5] Any TP taking a UDI as an input must be certified to perform only valid transformations, else no transformations, for any possible value of the UDI. The transformation should take the input from a UDI to a CDI, or the UDI is rejected (typically, for edits as the keyboard is a UDI).
- [E4] Only the agent permitted to certify entities may change the list of such entities associated with a TP. An agent that can certify an entity may not have any execute rights with respect to that entity.