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IS 3957 Doctoral Seminar in Systems and Technology Information Assurance. Introduction James Joshi September 8, 2005. Access Control. Access control Restrict access to system entities to authorized personnel Security Domain
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IS 3957 Doctoral Seminar in Systems and TechnologyInformation Assurance Introduction James Joshi September 8, 2005
Access Control • Access control • Restrict access to system entities to authorized personnel • Security Domain • A bounded group of subjects and objects under a single security policy • Multidomain Secure Environment • Ensuring a secure interaction among participating domains
Current Systems • Single domain systems • Multidomain systems • Open Interconnected Heterogeneous Systems • Web applications, E-Government, Global enterprises
Industry (various ops) • DoDBusiness Operations Environment • Initiate a transaction • Manage a transaction • Manage reference data • Provide performance support • Control access to and protect transaction and reference data • Transmit and translate transactions and reference data DoD Business Operations Environment (Ref: JECPO) Operational View OV-1 Warfighter Operations • Introduction Movement Training Requirements Analysis Maintenance Adjudication T&E Business Protection Environment Auditing Transportation Budget Planning Training Development Construction Mgmt Receiving Program Sch, Dir, Cont Contract Admin Disposal Mgmt Procurement Personnel Admin Engineering Analysis & Approval Payment/ Disbursement Facilities Mgmt Technology Projection Funds Mgmt Inventory Flow Mgmt Oversight Maintenance Planning Health, Safety, Environment Accounting Log Planning DoD Business Operations Business Protection Environment Example
Discretionary Access Control (DAC) • Subjects have ownership over objects • A subject can pass access rights to other subjects at his discretion • Highly flexible and most widely used • Not appropriate for • high assurance systems, e.g., a military system • Many complex commercial security requirements • “Trojan horse” problem
Mandatory Access Control (MAC) • Subjects/objects have security levels forming a lattice • Flow of information is restricted. • Example: (no-readup), (no-writedown) • Well-know MAC model is the Bell-LaPadula model
Some Existing Models • Abstract models • HRU’s Access Control Matrix • Schematic Protection Model and variation • Mandatory • Confidentiality model - Bell-LaPadula • Integrity model • Biba, Lipner’s, Clark-Wilson • Hybrid • Chinese wall
Confidentiality Policy • Also known as information flow policy • Integrity is secondary objective • Eg. Military mission “date” • Bell-LaPadula Model • Formally models military requirements • Information has sensitivity levels or classification • Subjects have clearance • Subjects with clearance are allowed access • Multi-level access control or mandatory access control
Bell-LaPadula: Basics • Mandatory access control • Entities are assigned security levels • Subject has security clearance L(s) = ls • Object has security classification L(o) = lo • Simplest case: Security levels are arranged in a linear order li< li+1 • Example Top secret > Secret > Confidential >Unclassified
“No Read Up” • Information is allowed to flow up, not down • Simple security property: • s can read o if and only if • lo≤ lsand • s has read access to o • Combines mandatory (security levels) and discretionary (permission required) • Prevents subjects from reading objects at higher levels (No Read Up rule)
“No Write Down” • Information is allowed to flow up, not down • *property • s can write o if and only if • ls≤ lo and • s has write access to o • Combines mandatory (security levels) and discretionary (permission required) • Prevents subjects from writing to objects at lower levels (No Write Down rule)
Categories • Total order of classifications not flexible enough • Alice cleared for missiles; Bob cleared for warheads; Both cleared for targets • Solution: Categories • Use set of compartments (from power set of compartments) • Enforce “need to know” principle • Security levels (security level, category set) • (Top Secret, {Nuc, Eur, Asi}) • (Top Secret, {Nuc, Asi}) • Combining with clearance: • (L,C) dominates (L’,C’) L’ ≤L and C’ C • Induces lattice of security levels
Lattice of categories {Nuc, Eur, Us} • Examples of levels • (Top Secret, {Nuc,Asi}) dom (Secret, {Nuc}) • (Secret, {Nuc, Eur}) dom (Confidential, {Nuc,Eur}) • (Top Secret, {Nuc}) dom (Confidential, {Eur}) • Bounds • Greatest lower, • Lowest upper • glbof {X, Nuc, Us} & {X, Eur, Us}? • lubof {X, Nuc, Us} & {X, Eur, Us}? {Nuc, Eur} {Nuc, Us} {Eur, Us} {Us} {Nuc} {Eur} {}
Integrity policy • Requirements different than confidentiality policies • Biba’s models • Low-Water-Mark policy • Ring policy • Strict Integrity policy • Lipner’s model • Combines Bell-LaPadula, Biba for a more practical software development and deployment process • Clark-Wilson model • Transaction integrity • Separation of duty
Biba’s Integrity Policy Model • Based on Bell-LaPadula • Subject, Objects • Integrity Levels with dominance relation • Higher levels • more reliable/trustworthy • More accurate • Information transfer path:Sequence of subjects, objects where • siroi • siwoi+1
Policies • Low-Water-Mark Policy • swo i(o) ≤i(s) prevents writing to higher level • sro i’(s) = min(i(s), i(o)) drops subject’s level • s1xs2 i(s2) ≤i(s1) prevents executing higher level objects • Ring Policy • sro allows any subject to read any object • swo i(o) ≤i(s) (same as above) • s1xs2 i(s2) ≤i(s1) • Biba’s Model: Strict Integrity Policy (dual of Bell-LaPadula) • sro i(s) ≤i(o) (no read-down) • swo i(o) ≤i(s) (no write-up) • s1xs2 i(s2) ≤i(s1) • Theorem for each: • If there is an information transfer path from object o1 to object on+1, then the enforcement of the policy requires that i(on+1) ≤i(o1) for all n>1
Requirements of Commercial Integrity Policies (Lipner) • Users will not write their own programs, but will use existing production programs and databases. • Programmers will develop and test programs on a nonproduction 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.
Integrity Policy: Principles of operation • Requirements induce principles of operation: • Separation of Duty: Single person should not be allowed to carry out all steps of a critical function • Moving a program from Dev. to Prod. system • Developer and Certifier (installer) of a program • Authorizing checks and cashing it • Separation of function • Do not process production data on development system • Auditing • Emphasis on recovery and accountability • Controlled/audited process for updating code on production system
RBAC (NIST Standard) Permissions PA UA Users Roles Operations Objects user_sessions (one-to-many) role_sessions (many-to-many) Sessions An important difference from classical models is that Subject in other models corresponds to a Session in RBAC
Advantages of RBAC • Allows Efficient Security Management • Administrative roles to manage other roles • Role hierarchy allows inheritance of permissions • Principle of least privilege • Minimizes damage • Separation of Duties constraints • Prevents fraud • Grouping Objects • Permissions can be grouped according to a class of objects • Policy-neutrality • Provides generality
Core RBAC (relations) • Permissions = 2Operations x Objects • UA ⊆ Users x Roles • PA ⊆ Permissions x Roles • assigned_users: Roles 2Users • assigned_permissions: Roles 2Permissions • Op(p): set of operations associated with permission p • Ob(p): set of objects associated with permission p • user_sessions: Users 2Sessions • session_user: Sessions Users • session_roles: Sessions 2Roles • session_roles(s) = {r | (session_user(s), r) UA)} • avail_session_perms: Sessions 2Permissions
RBAC with General Role Hierarchy RH (role hierarchy) Permissions PA UA Users Roles Operations Objects user_sessions (one-to-many) role_sessions (many-to-many) Sessions
RBAC with General Role Hierarchy • authorized_users: Roles 2Users authorized_users(r) = {u | r’ ≥ r &(r’, u) UA) • authorized_permissions: Roles 2Permissions authorized_users(r) = {p | r’ ≥ r &(p, r’) PA) • RH ⊆ Roles x Roles is a partial order • called the inheritance relation • written as ≥. (r1 ≥ r2) authorized_users(r1) ⊆ authorized_users(r2) & authorized_permisssions(r2) ⊆ authorized_permisssions(r1)
pp px, py px, py px, py px, py px, py px, py e10 e8, e9 e6, e7 e5 e3, e4 e1, e2 po pa, pb pm, pn px, py p1, p2 Example authorized_users(Employee)? authorized_users(Administrator)? authorized_permissions(Employee)? authorized_permissions(Administrator)?
Constrained RBAC RH (role hierarchy) Static Separation of Duty Permissions PA UA Users Roles Operations Objects user_sessions (one-to-many) Dynamic Separation of Duty Sessions
Static Separation of Duty • SSD ⊆2Roles x N • In absence of hierarchy • Collection of pairs (RS, n) where RS is a role set, n ≥ 2; for all (RS, n) SSD, for allt ⊆RS: |t| ≥ n ∩rtassigned_users(r)= • In presence of hierarchy • Collection of pairs (RS, n) where RS is a role set, n ≥ 2; for all (RS, n) SSD, for allt ⊆RS: |t| ≥ n ∩rtauthorized_uers(r)=
Dynamic Separation of Duty • DSD ⊆2Roles x N • Collection of pairs (RS, n) where RS is a role set, n ≥ 2; • A user cannot activate n or more roles from RS • What if both SSD and DSD contains (RS, n)? • Consider (RS, n) = ({r1, r2, r3}, 2)? • If SSD – can r1, r2 and r3 be assigned to u? • If DSD – can r1, r2 and r3 be assigned to u?
MAC using RBAC HR LW H Read Roles (same lattice) Write Roles (inverse lattice) M1R M2R M1W M2W M1 M2 BLP LR H L • Transformation rules • R = {L1R, L2R,…, LnR, L1W, L2W,…, LnW} • Two separate hierarchies for {L1R, L2R,…, LnR} and { L1W, L2W,…, LnW} • Each user is assigned to exactly two roles: xR and LW • Each session has exactly two roles yR and yW • Permission (o, r) is assigned to xR iff (o, w) is assigned to xW)
Security for Grid-based Computing SystemsIssues and Challenges
What is a Grid? • Enabling the coordinated use of geographically distributed resources — in the absence of central control, omniscience, strong trust relationships connect distributed heterogeneous high performance computer, computer cluster, large-scale database server and large-scale file server with high-speed interconnection network and integrate them into a transparent virtual high-performance computing environment. — Ian Foster
What is a Grid? • Systems & applications that integrate and manage resources and services distributed across multiple security domains • Large and dynamic pool of users and resources • Sharing is highly controlled & coordinated • Dynamic creation of services • Form virtual organizations (VO) • Collaboration is dynamic, ad-hoc • Resource providers belong to different real organizations employing different policies and mechanisms
What is a Grid? Domain 1 Domain 3 Virtual Organization Policy Domain 2 Domain 4 Essentially a Dynamic Multidomain Environment
Grid Security • Globus Toolkit (GT) includes Grid Security Infrastructure (GSI) • PKI to support identity mapping, single sign-on, delegation • GT2 • X.509 certificate, TLS, SSL protocol • Proxy certificate for delegation • Community Authorization Service • GT3 – Open Grid Services Architecture (OGSA) • Align Grid with web services technologies
Limitation of Classic Globus Authorization • Scalability • Each personnel or policy change requires changing policy at each participating site • Authorization is done at VO as well as in each site • Authorization information needs to be managed by individual local site • Expressivity • Native OS methods may not be expressive enough to support VO policies • Consistency • Native OS methods at different sites may not support the same kinds of policies
Grid Challenges • Individual hosts (resource providers) • Each domain must specify highly dynamic set of access control policies • Challenges • Highly flexible access control framework (attribute-based AC) • Multi-domain problem • Multiple policies need to be integrated • Challenges • Multidomain challenges! • Trust issues and Risk management
Secure interoperation • Challenges • Expressive multi-domain policy specification framework • Automation of the integration of policies • Algorithms to detect violations and compute maximal secure interoperation scalability? Policy negotiation Issues (trust) Delegation Identity/Credential mapping
Security Management • Tools and techniques needed to support efficient administration of Grid security • Grid can scale to Internet size • Dynamically changing resource pool • Protection objects may include • Compute cycle; storage elements • Sophisticate instruments • Data (files and database elements) • Services • High level information knowledge/concepts • Dynamic pool of users with diverse credentials • Identity/credential management • Policies and mechanisms evolve
Trust and Risk Management • Trust management is essential for dynamic collaboration environment • Trust-based authorization • Absolute security is not possible • Single point of failure situation • Security assurance may vary • Grid resources may be very sensitive • Trust and risk issues become very crucial • Impact severity of information leaks? • How to control propagation of risks?
Grid Challenges • Individual hosts (resource providers) • flexible access control framework • Multi-domain problem • Semantic heterogeneity & secure interoperability • Security management • Trust issues and Risk management
Local Policy Base Local Policy Base Access Control Module Local Policy Base Multidomain Security Application (e.g., workflow) Application (e.g., workflow) Lightly-coupled Access Control Module Access Control Module Trust-based Application (e.g. workflow) User’s access requests User’s authorization Access Control Module Global Policy Base Application (e.g., workflow) Application (e.g., workflow) Tightly-coupled (Federated system) Access Control Module Local Policy Base
Semantic heterogeneity • Different systems may use different security policies • e.g., DAC, MAC, Chinese wall, Integrity policies etc. • Variations of the same policies • e.g., BLP model and its several variations • Naming conflict on security attributes • Similar roles with different names • Similar permission sets with different role names • Structural conflict • different multilevel lattices / role hierarchies
Secure Interoperability • Principles of secure interoperation Principle of autonomy • If an access is permitted within an individual system, it must also be permitted under secure interoperation in a multi-domain environment. Principle of security • If an access is not permitted within an individual system, it must not be permitted under secure interoperation. • Interoperation of secure systems can create new security breaches
Unsecure Interoperability A X A X d c a a Y Y B C B C b b D Z D Z 2 1 2 1 F12 = {a, b, c, d} F12 = {a, b} (1) F12 = {a, b, d} Direct access (2) F12 = {c} F12 - permitted access between systems 1 and 2
Challenges in Secure Interoperability • How to ensure autonomy and security principles? • Determining inconsistencies/incompleteness in security rules. • Identifying security holes • Selecting optimality criteria for secure interoperability: maximizing number of domains, direct accesses
Assurance and Risk Propagation & Security Management • Assurance and Risk propagation • Breach in one domain can render the whole environment insecure • Cascading problem • Security Management • Centralized/Decentralized • Managing global metapolicy • Managing policy evolution
Approaches to Multidomain Problem • Policy-Metapolicy specification framework • Ad-hoc, Formal models: lattice merging, RBAC • Agent based approach (Policy agents) • Architectural approaches (CORBA, DCE)
A Multi-Domain Access Control Framework • A Multi-Phase Framework • Based on RBAC model Pre-integration Policy Comparison Policy Conformance Merging/ Restructuring Need external mediation policy to handle conflicts/incompleteness Consistent, complete and optimal specification
Pre-integration Phase • Requires RBAC representation of arbitrary policies. A policy mapping technique is needed for non-RBAC systems. • Uses an information base • Semantic information about domains including policies, roles and attributes • Integration/merging strategies to generate the overall configuration of the multi-domain environment.
Policy Comparison and Conformance • Tools & techniques for detecting • Semantic conflicts • Naming conflicts • Structural conflicts • Rule conflicts • Mediation policies are needed for resolution • Predefined meta-policies • Domain cooperation by administrators • Tradeoffs • Determine optimal/heuristic solutions secure interoperability
[De] Merging/Restructuring • Merging/integrating policies • Restructure domain policies according to the selected optimal criteria • Generate integrated global policy • Repeat policy conformance step • Re-evaluation and restructuring of meta-policy