Secure Information Sharing Using - PowerPoint Presentation

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Secure Information Sharing UsingAttribute Certificates and Role Based Access Control

Ganesh Godavari, C. Edward Chow 06/22/2005University of Colorado at Colorado Springs

International Conference of Security and Management 2005Slide2

Introduction to Information Sharing

Information Sharing relates to the sharing of information between two or more entities.Synchronous Information Sharingreal-time communicationcollaboration in "same time-different place”Tools -- Instant messaging, Video conferencing ...Asynchronous Information SharingCollaboration in “different time-different place”

Tools -- Discussion boards, E-mail …Slide3

Introduction to Information Sharing

Steps for secure Information sharingAuthenticationUsername/password, pin #, X509 Certificates,AuthorizationGroup based authorization, role based authorization etcAccessSecure storage of Authorization policy is criticalAttribute Certificates (AC)Slide4

Secure Information Sharing

MotivationParadigm Shift “Need to Know” to “Need to Share”Incidents like 9/11, natural disasters relief.Organizations are intertwined more so now then ever.

Rapid deployment of a secure information sharing system for a multi-agency taskforce has become critical issue for homeland security and defense

Information Sharing relates to the sharing of information between multiple agencies or organization.Slide5

Role Based Access Control

USERS

ROLES

SESSIONS

operation

objects

PRMS

session_roles

user_session

User Assignment (UA)

Permission Assignment (PA)

many-to-many relationship

one-to-many relationship

Gives roles activated by the session

User is associated with a session

NIST study shows user’s role less likely to change and roles are tightly related to access rights to information.

File system operations: read, write and execute

DBMS operations: Insert, delete, append and updateSlide6

Attribute Certificates

AC’s Standardized in RFC-3281, “An Internet Attribute Certificate for Authorization”no public key like Public Key Certificate (PKC)used for storing short duration attributesRole, resource allocation, security clearance…AC in security

Strong identity of the holder is not required

access control specification

Non-repudiation of the attributes by the issuer

Privilege delegation, role allocation ….Slide7

Privilege Management Infrastructure (PMI)

Privilege Management InfrastructureSimilar to Public Key InfrastructureFunction is to specify the policy for the attribute certificate issuance and management

Concept

PKI entity

PMI entity

Certificate

Public Key

Certificate (PKC)

Attribute Certificate (AC)

Certificate issuer

Certification

Authority (CA)

Attribute Authority (AA)

Certificate user

Subject

Holder

Certificate

binding

Subject’s Name to

Public Key

Holder’s Name to

Privilege Attribute(s)

Revocation

Certificate

Revocation List

(CRL)

Attribute Certificate

Revocation List (ACRL)

Root of trust

Root CA or Trust

Anchor

Source of Authority (SOA)

Subordinate

Authority

Subordinate

Certification

Authority

Attribute Authority (AA)

Comparison of PKIs and PMIs

[chad2-02]Slide8

Issues with large multi-agency Information System

IssuesHow can we authenticate users belonging to multiple organization?Authorization policy specification encompassing multiple organizationsSolutionsX509 certificates for identification of usersAuthorization based on RBAC[] model

Security Administration can be a management nightmareSlide9

Context Free Grammar of Authorization Policy Specification

sisprivilegeset <role name> <privilegeset name>{ <privilege> := if ( <expression> ) do <action> <expression> := <term> | <term> && <expression> |

( <expression> ) | ! ( <expression> )

<term> := <factor> | <factor> || <term> | ( <term> )

<factor> := <variable operator value>

<operator> := > | >= | < | <= | == | != | #

<action> := grantAccess | rejectAccess |

acquirePrivileges <privilegeset Name> |

contact <authorization server>

}

#: regular expression string matching operatorSlide10

RBAC specification format

<?xml version="1.0" encoding="utf-8" standalone="yes"?><!--===== SIS request example =====--><sis> <Role>administrator</Role> <Group>Info Share</Group>

<OU>UCCS</OU>

</sis>Slide11

Example – File Access Specification

Privilege specification for administratorFile access control specificationsisprivilegeset administrator filematch { if ( ( url # “/etc/passwd” ) && ( requestAction # “get” ) ) do grantAccess# user accounts protection from get and post requests by administrator

if ( ( url # “*~*/private/” ) && ( requestAction # “get” ) ) do rejectAccess

if ( ( url # “*~*/private/” ) && ( requestAction # “post” ) ) do rejectAccess

:

}

#: matching operator (A # B: if A contains B)Slide12

SIS system overview

authorize

Administration

Tool

Server

RBAC

Policy

file

User

Access Control

Decision and

Enforcement

Engine

PKC

User Role

Specification

AC

Authenticate

Mail Server

Database

Instant Msg

Server

Web Server

Create/Change/

Revoke Attribute Certificates

(ACDE)Slide13

Access Control and Decision EnforcementSlide14

Setup CA

The coordinator of the task force from multiple agencies set up a rootCA-MA (root CA for Multiple Agencies).Each agency requests a certificate to be signed by rootCA-MA.Each agency issues a new PKC to each user in its organization involved in the task force.At each server which providing secure information sharing service for this task force, add the rootCA-MA information into CABundle (file containing list of valid CA's).Each client/user installs the certificate in the local browser or application's.Slide15

Choices for storing AC’s

A user's AC can be storedcentral repository of the taskforcewith the agency's local administrator have control only over the AC's of the users belonging to that agencylocally at each agency that defines his role within that agencyuser's privileges are the result of the association of the user with a particular agencyuser's privileges are revokedall the agencies must be notified

Prevent unauthorized access

Trust relationship between organizations determines where the AC's are storedSlide16

Setup PMIOur approach

Store all the user privileges in the organization the user originally belongs to Check user's privileges on every attempt to access the resourcesSetup PMIThe coordinator of the task force signs the AC’s of the members.Agency members AC’s are distributed and installed on the LDAP server of the agency.web servers and shared applications query the PMI for authorization and access controlSlide17

Implementation

Apache (v 1.3.31) + Mod_SSL(v 2.8.18-1.3.31) + openSSL (v 0.9.7d)We modified mod_auth_ldap with AC based ACDEOpenLDAP (v 2.0.27-8)Attribute Certificate's attribute definitions was added to inetorg-person.schemaOpenSSL libraries used for generating X509 certificateswe created AC generation utility using OpenSSL

For validation we use Markus Lorch’s code

We created PKC generation utility based on EXPECTSlide18

SIS Test-bed

Server

LDAP AccessTime (ms)

AC retrieval/validation (ms)

sis-nissc

54.62

96.88

sis-connecticut

51.84

93.77

sis-newjersey

51.19

93.31

Performance

Access Time from a client at sis-canada

All Machines

Pentium-III, 500 MHz

256 MB RAM

Redhat Linux-2.4.20-6Slide19

Conclusions

Developed efficient procedures and tools to set up Public Key Infrastructure for authentication and Privilege Management Infrastructure for authorization.Created a multi-agency SIS test bed based on LDAP and web servers. OpenLDAP servers were enhanced to accept attribute certificates.

LDAP module of the apache web server was extended to achieve secure web access.Slide20

PKC vs. AC

PKC binds a subject (DN) to a public keyAC's binds permission (attributes) to an entity

Version

Serial Number

Signature ID

Subject

Issuer

Validity Period

Subject Public Key Info

Extension’s

S

i

g

n

a

t

u

r

e

Version

Serial Number

Signature ID

Holder

Issuer

Validity Period

Attributes

Extensions

S

i

g

n

a

t

u

r

e

Public Key Certificate

(

PKC

)

Attribute Certificate(AC)