Discussing “Developing Secure Systems with UMLSec”

15 FEB 2006 - Joe Combs

What Problem are we Trying to Solve?Blindly inserting security mechanisms into a

system doesn’t work

Need to bring efforts to mitigate these design limitations before system is actually implemented

Introducing UMLSec• Extension of Unified Modeling

Language - de-facto standard for OO development

• Attempt to encapsulate & make available to developers knowledge on prudent security engineering

• Encapsulation and modularity makes OO systems very well suited to considering security

UML Diagrams of Interest• Use Case - typical interaction between user and system

• Activity - workflow modeling/detailed explanation of use case

• Class - static structure of the system

• Interaction - sequence or collaboration diagram describes interaction between objects via message exchange

• State Chart - dynamic component behavior within an object

• Package - groups parts of a system into higher level units

• Deployment - describes physical arrangement in a real-world instance

UMLSec Notation• Stereotypes

• <<stereotype>>• Extensibility mechanism used to create meta-information

about an entity in the diagram

• Tag-Value Pairs• {tag,value}• Extensibility mechanism to describe a property of a model

element

Use Case Diagram

<<fair exchange>>: if “buys goods” then eventually “sells goods”

Activity Diagram

Solution on right gives fair exchange if payment is <<provable>>

Class Diagram

Ensure class structure provides data security

Key::newkey() guarantees confidentiality & integritybut random does not!

Interaction Diagram

•Purchase system sends Init message to access card passing a session key signed with M’s private key and encrypted with C’s public key

•C decrypts the session key with its private key and verifies signature with M’s public key

•Once session key has been verified in this way, C can encrypt and send secrets using the session key and pass to M on the Resp message

State Chart Diagram

Ensure behavior within a component - access control, database security, etc.

Transition labels:•events - message called on this object•[conditions] - must be true for transition to fire•\actions - carried out if transition fires

Package Diagram

Uses visibility of parts within packages to reason about access privileges

Deployment Diagram

Express security requirements on physical layer of the system:•communication links•hardware security•etc.

Security Patterns

Operation rx() leaks information on the account balance

The Wrapper Pattern

Ensures no low read after a high write

Now What?• UMLSec provides a mechanism for

communicating security concerns, bringing security up to the requirements and design phases of the lifecycle

• Where can this go from here?• Incorporate UMLSec notation for association,

generalization, etc.• Formal methods approaches?