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CMSC 426-626:Common Criteria for Computer/IT Systems

Prof. Krishna Sivalingam

Oct 23, 2006

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Common Criteria

Commoncriteria.org Commoncriteriaportal.org

• Lists CC v3.1 (and older versions)

Originally released in 1998 An International Standards Organisation

(ISO) standard for security evaluation of software products

IT product vendors use the CC as a benchmark for product security

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NIAP

National Information Assurance Partnership (NIAP) is a joint venture between NIST (nist.gov) and NSA (nsa.gov)

Goal: “increase the level of consumer trust in information systems and networks” from http://www.nsa.gov/ia/industry/niap.cfm

One service: Common Criteria Evaluation and Validation Scheme (CCEVS) that “focuses on meeting the security testing, evaluation, and assessment needs of both IT products and consumers.”

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Security concepts and relationships

From CC Part 1 (of v3.1)

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Evaluation concepts & relationships

From CC Part 1 (of v3.1)

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CC Process

A user creates Packages or “Protection Profile” for a desired security product

The PP describes the product’s protection needs

Written by the user (e.g. government, banking industry, vendor’s marketing group, product inventor)

Describes security aspects needed in an IT product

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CC Protection profile (in Combined Federal Criteria)

Rationale• Protection policy and

regulations

• Information protection philosophy

• Expected threats

• Environmental assumptions

• Intended Use Functionality

• Security Features

• Security Services

• Available security mechanisms

Assurance• Profile-specific assurances

• Profile-independent assurances

Dependencies• Internal

• External

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CC Protection Profile

Introduction Product/System Family Description: Generic

description of family of products. Product/System Family Security Environment –

intended use, environment of use, threats to assets, organizational security policies, etc.

Security Objectives IT Security Requirements – Functional and

Assurance Rationale

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What happens with PP?

A vendor develops an IT product based on the requirements set in the PP

Vendor then prepares a “security target” document that describes the security and assurance aspects of the product.• Can relate Security Target to Specs. In the

Protection Profile

Security Target can also be written independent of a PP and sold along with the IT product

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CC Package

A package is a named set of security requirements. A package is either • a functional package, containing only SFRs (Security

Functional Requirements) or

• an assurance package, containing only SARs (Security Assurace Requirements)

• But, not both.

Examples of Assurance packages are the EALs (Evaluation Assurance Level), than run from EAL1 (lowest) through EAL7 (highest)• EAL1 through EAL4 are most common

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Security Target, contd.

From CC, part I:

“The Security Target begins with describing the assets and the threats to those assets. The Security Target then describes the countermeasures (in the form of Security Objectives) and demonstrates that these countermeasures are sufficient to counter these threats: if the countermeasures do what they claim to do, the threats are countered.”

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Security Target (per Comb Fed Crit.)

Rationale• Implementation

fundamentals

• Information protection philosophy

• Countered Threats

• Environmental Assumptions

• Intended Use Functionality

• Security features

• Security services

• Security mechanisms selected

Assurance• Target-specific assurances

• Target-independent assurances

Dependencies• Internal

• External

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Security Target Introduction: description of the target of evaluation (TOE) at three

different abstraction levels Conformance: If the ST is conformant with any PPs or packages Security problem definition: Threats, Assumptions, etc. Security objectives: Extended components definition: describes components not

described in Part 2 or Part 3 of CC document Security requirements: Present security objectives in standard

requirements format TOE Summary specifications: How functional requirements are

implemented and met and how assurance reqts. Are met Rationale: Sec Objectives Rationale, Sec. Reqts. Rationale, TOE

Summary Spec. Rationale, etc.

Before and during evaluation, ST states “what is to be evaluated?” After evaluation, ST states “what was evaluated?”

14From CC Part 1 (of v3.1)

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Classes in Common Criteria

Functionality (11)• Security audit (FAU)• Communications (FCO)• Crypto support (FCS)• User data protection (FDP)• Identification &

Authentication (FIA)

• Sec. Mgmt (FMT)• Privacy (FPR)• Protection of trusted

security functions (FPT)• Resource utilization (FRU)• Trusted Path (FTP)

• TOE Access (FTA)

Assurance (10)• Configuration Management• Delivery and operation• Development• Guidance documents• Life-cycle support

• Testing• Vulnerability Assessment• Maintenance of Assurance• Protection profile evaluation• Security target evaluation

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Classes

Classes are broken down into families, which are broken down into components

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Classes, contd.

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Components

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EAL Levels

EAL1: Functionally Tested EAL2: Structurally Tested; Applicable to systems

with low-moderate assurance needs, but not enough development record (e.g legacy systems)• Based on High-Level Design Analysis & Sec. Fn. Analysis

EAL3: Methodically Tested & Checked• Use of devt. Environment controls and config. Mgt

EAL4: Methodically Designed, Tested & Reviewed• Includes Low-level design, complete interface description,

and subset of implementation• Informal model of security policy• Windows 2000, XP, Red Hat Enterprise Linux (RHEL)

Version 4 Update 1 AS and Red Hat Enterprise Linux (RHEL) Version 4 Update 1 WS

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EAL Levels, contd.

EAL5: Semi-formally Designed and Tested EAL6: Semi-formally Verified Design and

Tested EAL7: Formally Verified Design and Tested

• Formal functional spec. and high-level design

• Implementation representation be used as testing basis

• Independent confirmation of developer’s test results

• Extremely high-risk situations and requires substantial security engineering