Users and Rules

CR3     The allowed relations must meet the requirements imposed by the principle of separation of duty.

ER3     The system must authenticate each user attempting to execute a TP

–    Type of authentication undefined, and depends on the instantiation

–    Authentication not required before use of the system, but is required before manipulation of CDIs (requires using TPs)

Logging

CR4     All TPs must append enough information to reconstruct the operation to an append-only CDI.

–   This CDI is the log

–   Auditor needs to be able to determine what happened during reviews of transactions

Handling Untrusted Input

CR5     Any TP that takes as input a UDI may perform only valid transformations, or no transformations, for all possible values of the UDI. The transformation either rejects the UDI or transforms it into a CDI.

–    In bank, numbers entered at keyboard are UDIs, so cannot be input to TPs. TPs must validate numbers (to make them a CDI) before using them; if validation fails, TP rejects UDI

Separation of Duty In Model

ER4     Only the certifier of a TP may change the list of entities associated with that TP. No certifier of a TP, or of an entity associated with that TP, may ever have execute permission with respect to that entity.

Enforces separation of duty with respect to certified and allowed relations

Certification Rules 1 and 2

CR1     When any IVP is run, it must ensure all CDIs are in a valid state

CR2     For some associated set of CDIs, a TP must transform those CDIs in a valid state into a (possibly different) valid state

–    Defines relation certified that associates a set of CDIs with a particular TP

–    Example: TP balance, CDIs accounts, in bank example

Enforcement Rules 1 and 2

ER1     The system must maintain the certified relations and must ensure that only TPs certified to run on a CDI manipulate that CDI.

ER2     The system must associate a user with each TP and set of CDIs. The TP may access those CDIs on behalf of the associated user. The TP cannot access that CDI on behalf of a user not associated with that TP and CDI.

–    System must maintain, enforce certified relation

–    System must also restrict access based on user ID (allowed relation)

Clark-Wilson Integrity Model

•      Integrity defined by a set of constraints

–    Data in a consistent or valid state when it satisfies these

•      Example: Bank

–    D today’s deposits, W withdrawals, YB yesterday’s balance, TB today’s balance

–    Integrity constraint: D + YB –W

•      Well-formed transaction move system from one consistent state to another

•      Issue: who examines, certifies transactions done correctly?

Entities

•      CDIs: constrained data items

–    Data subject to integrity controls

•      UDIs: unconstrained data items

–    Data not subject to integrity controls

•      IVPs: integrity verification procedures

–    Procedures that test the CDIs conform to the integrity constraints

•      TPs: transaction procedures

–    Procedures that take the system from one valid state to another 

Chapter 6: Integrity Policies

•      Overview

•      Requirements

•      Biba’s models

•      Clark-Wilson model

Overview

•      Requirements

–   Very different than confidentiality policies

•      Biba’s model

•      Clark-Wilson model

Requirements of Policies

•              Users will not write their own programs, but will use existing production programs and databases.

•              Programmers will develop and test programs on a non-production system; if they need access to actual data, they will be given production data via a special process, but will use it on their development system.

•              A special process must be followed to install a program from the development system onto the production system.

•              The special process in requirement 3 must be controlled and audited.

•              The managers and auditors must have access to both the system state and the system logs that are generated.