TIARATrust-management, Intrusion-tolerance,

Accountability and Reconstitution Architecture

Howie Shrobe, Andre de Hon, Tom Knight

TIARA Layers

Hardware:Security Tags Processing

Object Abstraction:Structured Memory,

Method Dispatch

Operating System:Hardware Management,Hardware Level Policy

Meta-Object Level:Wrapper Management

Access Control:Policy Enforcement S

ystem S

oftware

Plan Level:Self Monitoring and Recovery

Data Accountability:Provenance Tracking

Application Substrate:Application Data Management

Application

Middlew

are

Tiara Hardware Level

Building The Object Abstraction

Bounds

Identity

Type

Maintaining Data Provenance

Any single attack can ‘sink the boat’

EmergencyRaft

Fundamental ProblemFundamental Problem Based on monolithic security kernel & Based on monolithic security kernel & undifferentiated memoryundifferentiated memory All privileged operations in a single All privileged operations in a single security domainsecurity domain

Consequences:Consequences: Single domain breach gives attacker Single domain breach gives attacker everythingeverything

Many Interfaces and services Many Interfaces and services Huge, complex code base Huge, complex code base

Millions of lines of codeMillions of lines of code Many opportunities for bugsMany opportunities for bugs

Typically 1 bug per 100 LoCTypically 1 bug per 100 LoC Complexity scales closer to NComplexity scales closer to N22 than linear than linear

Impossible to completely vet Impossible to completely vet Large surface of vulnerability for attackLarge surface of vulnerability for attack

Origin of the Problem?Origin of the Problem? Good engineering tradeoffs based Good engineering tradeoffs based on 1970’s and 1980’s technologyon 1970’s and 1980’s technology Gates and memory were expensiveGates and memory were expensive Challenge to build fast, capable Challenge to build fast, capable systemssystems

Minimalist designs ruled the day Minimalist designs ruled the day RISCRISC

Separate domains Separate domains context switch context switch Known to be expensive (10KKnown to be expensive (10K100K 100K cycles)cycles)

System and software engineers System and software engineers know:know: Must avoid crossing domainsMust avoid crossing domains Conclusion:Conclusion: Efficiency means minimum Efficiency means minimum compartmentalizationcompartmentalization

IdeaIdea

Add metadata at the Add metadata at the word levelword level Tag on every word in Tag on every word in memorymemory

RoleRole CodeCode User dataUser data PointerPointer System dataSystem data

ContextContext Owner Owner PedigreePedigree

1010110001110001000011100101010

Data

Type

Context

Example:Example: 32 bit word 32 bit word 24 bits data24 bits data 4 bits type4 bits type 4 bits data context4 bits data context

Security compartmentSecurity compartment PedigreePedigree

[Shown small for illustration purpose only. All fields longer in practice.]

Tagged Data PathTagged Data Path

Data

Register File

Result Data

TagsUnit

Operand 1

Operand 2

Instruction

Tag 1Tag 2

PC

Result Tag

Trap Signal

Trap Dispatch AddressTag

ALU

Process Identifier

Metadata UsesMetadata Uses IsolationIsolation

Elaborate shortlyElaborate shortly Enforce OO modelEnforce OO model SandboxingSandboxing

Multi Level Security (MLS)Multi Level Security (MLS) IntegrityIntegrity Robust Error HandlingRobust Error Handling

Pointer abusePointer abuse Code bashingCode bashing BoundsBounds

PolicyPolicy AuditingAuditing SynchronizationSynchronization ……more in white paper…more in white paper…

Data Result Data

TagsUnit

Operand 1

Operand 2

Instr

Tag 1Tag 2

PC

Result Tag

Trap Signal

Trap Addr

Tag

ALU

PID

Efficient Hardware SupportEfficient Hardware Support

Process tags in Process tags in parallel with datapathparallel with datapath No impact on cycle No impact on cycle

timetime Leverage existing Leverage existing

speculation/in-order speculation/in-order exception and exception and retirement hardwareretirement hardware

Implement common-case Implement common-case fast with small Hash fast with small Hash Execution (HEX) unitExecution (HEX) unit Similar in Similar in

size/complexity to TLBsize/complexity to TLB

CostCost

Dominant cost {area, bandwidth} Dominant cost {area, bandwidth} for tagsfor tags All memories, register files, cachesAll memories, register files, caches HEX modest sizeHEX modest size Memory already dominant area in Memory already dominant area in processorsprocessors

E.g.:E.g.: 32b tag on 32b tag on 128b atomic word128b atomic word

Historical PredecessorsHistorical Predecessors

Burroughs B5000,6000 (1970s)Burroughs B5000,6000 (1970s) 3b tag3b tag Security based on high-level compiled Security based on high-level compiled codecode

Symbolics LISP Machine (1980s)Symbolics LISP Machine (1980s) 8b tag8b tag Only use for robust error handlingOnly use for robust error handling Not explicitly for securityNot explicitly for security

Intel i432 (~1980)Intel i432 (~1980) IBM System 38 (1980s)IBM System 38 (1980s)

1b tag1b tag

Compartment TagsCompartment Tags

Tag every word with a compartment Tag every word with a compartment IDID

Process PermissionsProcess Permissions

Policy table specifies rights for Policy table specifies rights for process on each compartmentprocess on each compartment

Support with HEXSupport with HEX

HEX Unit HEX Unit implements implements policy table on policy table on cycle-by-cycle cycle-by-cycle basisbasis

ResultResult Can haveCan have

Private data to processes (objects)Private data to processes (objects) Richly shared need-to-know data Richly shared need-to-know data

principle of least privilegeprinciple of least privilege WhileWhile

Transfer between objects/services as Transfer between objects/services as procedure callprocedure call

Few cycles, no expensive context Few cycles, no expensive context switchswitch

Change rulesChange rules Eliminate performance penalty for Eliminate performance penalty for strong isolationstrong isolation

Eliminate performance/security Eliminate performance/security tradeofftradeoff

Service IntegrityService Integrity

HEX can enforce policies to HEX can enforce policies to prevent service subversionprevent service subversion Only execute words tagged as Only execute words tagged as instructionsinstructions

Limit PC range for serviceLimit PC range for service Code is tagged write-onlyCode is tagged write-only Ordinary code not able to write Ordinary code not able to write instructionsinstructions Write instructions runable as service roleWrite instructions runable as service role

Enables: CompartmentalizationEnables: Compartmentalization

Double win:Double win: Breach containmentBreach containment

Avoid single point of failureAvoid single point of failureLimit impact of any breachLimit impact of any breach

Small code in compartmentSmall code in compartmentStrong abstraction Strong abstraction complexity complexity management management

~5K lines/compartment~5K lines/compartmentPlausibly verifiablePlausibly verifiable

No single or even doublepenetration can sink the boat

SecureRaft

Generic MechanismGeneric Mechanism

Metadata w/ Programmable HEX unitMetadata w/ Programmable HEX unit Flexible mechanismFlexible mechanism Does not build policy into hardwareDoes not build policy into hardware

Not even the fielding/use of metadata bitsNot even the fielding/use of metadata bits Large set of usesLarge set of uses

See white paperSee white paper

EnablesEnables Selectable security levelsSelectable security levels

Same hardware, different policiesSame hardware, different policies Experimentation Experimentation

New ideasNew ideas Different security strategiesDifferent security strategies

Tiara OS Level

Least Privilege

Isolation

No Kernel

ZKOS OverviewZKOS Overview Traditional Operating Systems:Traditional Operating Systems:

Operate on “Raw Seething Bits”Operate on “Raw Seething Bits” A A sseparate monolithic kernel all of whose eparate monolithic kernel all of whose

components have maximum privilegecomponents have maximum privilege KKernel separation achieved through address space ernel separation achieved through address space

mappingsmappings UUser calls for system service are different than ser calls for system service are different than

normal subroutine callsnormal subroutine calls SSystem services require context switchystem services require context switch

Zero-Zero-Kernel Operating System (ZKOS)Kernel Operating System (ZKOS) Operates on Structured Object-Oriented MemoryOperates on Structured Object-Oriented Memory KKernel functionality is not ernel functionality is not separateseparate or monolithic or monolithic Each kEach kernel component has limited privileges ernel component has limited privileges

corresponding to its taskcorresponding to its task KKernel components are in same address space as user ernel components are in same address space as user

codecode SSeparation achieved via STA taggingeparation achieved via STA tagging UUser calls for system services are normal procedure ser calls for system services are normal procedure

callscalls SSystem services do not require context switchystem services do not require context switch

ZKOS Structured MemoryZKOS Structured Memory

All memory is viewed as consisting of All memory is viewed as consisting of ObjectsObjects Extent, Type, IdentityExtent, Type, Identity

All objects are referenced only through All objects are referenced only through Object-ReferencesObject-References

Only the Memory Manager can create Only the Memory Manager can create object references (in concert with object references (in concert with Domain Manager)Domain Manager) Base, Bounds, Meta-DataBase, Bounds, Meta-Data

Object references are (nearly) Object references are (nearly) immutableimmutable

Object references do not carry Object references do not carry permissionspermissions

There are no raw pointers or pointer There are no raw pointers or pointer arithmeticarithmetic

Reclamation is via Garbage CollectionReclamation is via Garbage Collection No “Raw Seething Bits”No “Raw Seething Bits”

ZKOS Kernel-less IsolationZKOS Kernel-less Isolation ZKOS employs a modular architecture ZKOS employs a modular architecture together with security tagged memory to together with security tagged memory to manage interfaces between OS componentsmanage interfaces between OS components Isolation provide by security tags, not Isolation provide by security tags, not separate address spaceseparate address space

Each OS component operates in its own Each OS component operates in its own security contextssecurity contexts

Communication is via procedure callCommunication is via procedure call Interface memory for each component is separate Interface memory for each component is separate from internal memoryfrom internal memory

ZKOS Components are not different in kind ZKOS Components are not different in kind from other componentsfrom other components

All set-up and management of security-All set-up and management of security-context is done by the context is done by the Domain MangerDomain Manger

The domain manager only changes security The domain manager only changes security tags based on authority from the tags based on authority from the authorization systemauthorization system

Privilege carried in process credentialsPrivilege carried in process credentials

Interactions between ZKOS Interactions between ZKOS ComponentsComponents

Procedure call is the only way that Procedure call is the only way that components interactcomponents interact Procedures implemented by methodsProcedures implemented by methods Object-oriented modularity enforced by STAObject-oriented modularity enforced by STA

Internal code and data is inaccessible Internal code and data is inaccessible to all other components or processes to all other components or processes

Each component uses the following Each component uses the following security contexts for memory:security contexts for memory: Internal component dataInternal component data Internal component codeInternal component code Interface memoryInterface memory

Each component is authorized to perform Each component is authorized to perform only its designated tasksonly its designated tasks

Other components or processes are never Other components or processes are never authorized to access or modify internal authorized to access or modify internal data or code within OS components.data or code within OS components.

Examples: Least Privilege Examples: Least Privilege OperationOperation

Scheduler Scheduler Privilege to loads process id register Privilege to loads process id register in hardwarein hardware

No ability to change process No ability to change process credentialscredentials

No ability to examine or change No ability to examine or change application dataapplication data

System DebuggerSystem Debugger Privilege to examine stack of Privilege to examine stack of application processapplication process

Unable to see or modify private Unable to see or modify private application data on stackapplication data on stack

Tiara Software Level

Object System

Meta Object Protocol

Non-Bypassable Wrappers

Software Layers

Hardware:Security Tags Processing

Object Abstraction:Structured Memory,

Method Dispatch

Operating System:Hardware Management,Hardware Level Policy

Meta-Object Level:Wrapper Management

Access Control:Policy Enforcement S

ystem S

oftware

Plan Level:Self Monitoring and Recovery

Data Accountability:Provenance Tracking

Application Substrate:Application Data Management

Application

Middlew

are

Multi-method DispatchMulti-method Dispatch ZKOS is object oriented all the way down to the ZKOS is object oriented all the way down to the

memory levelmemory level All procedures are potentially implemented by All procedures are potentially implemented by

methods on object classesmethods on object classes Multi-method dispatch enables selection of the Multi-method dispatch enables selection of the

effective method based on the types of effective method based on the types of all all of of the argumentsthe arguments

Security method dispatch:Security method dispatch: Dispatches on all data arguments as usual Dispatches on all data arguments as usual But also dispatches on an additional But also dispatches on an additional process process

credentialcredential argument argument Process authorization credentialProcess authorization credential encodes the role & encodes the role &

privileges of the user-agent on whose behalf the privileges of the user-agent on whose behalf the process runsprocess runs System daemon credentialsSystem daemon credentials User credentialsUser credentials

Failure to match the process authorization Failure to match the process authorization credentials with a method’s invocation security credentials with a method’s invocation security context context Prevents the effective method from being executedPrevents the effective method from being executed Invokes a security exception handlerInvokes a security exception handler

Multi-method dispatch subsumes all object-Multi-method dispatch subsumes all object-oriented modelsoriented models

Wrapper MethodsWrapper Methods

There are different categories of There are different categories of methodsmethods PrimaryPrimary WrapperWrapper

The Effective Method is The Effective Method is combination of all applicable combination of all applicable methodsmethods Wrappers are called firstWrappers are called first Control whether primary method is Control whether primary method is called and with what argumentscalled and with what arguments

There can be different categories There can be different categories of wrapper methodsof wrapper methods

Meta Object Protocol (MOP)Meta Object Protocol (MOP)

Everything is an instance of some Everything is an instance of some classclass

Classes, Functions, and methods Classes, Functions, and methods are instances of meta-classesare instances of meta-classes

Methods on meta-classes control Methods on meta-classes control how the basic operations of the how the basic operations of the object system workobject system work Can build embedded object models with Can build embedded object models with different propertiesdifferent properties

Enough rope to take over and hang the Enough rope to take over and hang the useruser

Meta-Object methods can prevent doing Meta-Object methods can prevent doing bad things including undoing bad things including undoing themselvesthemselves

Tiara Software Level

Access Control

Execution Monitor

Access ControlAccess Control

Many security policies (like role-based Many security policies (like role-based access control) are access control) are naturallynaturally expressed expressed at an object level of granularity using at an object level of granularity using multi-method wrappersmulti-method wrappers Principal: Who is acting and in what rolePrincipal: Who is acting and in what role Operation: What is being doneOperation: What is being done Operands: To what objectsOperands: To what objects Role: Exclude user-agents from adopting Role: Exclude user-agents from adopting certain roles or from adopting them certain roles or from adopting them simultaneouslysimultaneously

Trust policies are defined on maximally Trust policies are defined on maximally general typesgeneral types Reduces the number of policies requiredReduces the number of policies required Provides automatic extension as new subtypes Provides automatic extension as new subtypes are definedare defined

Reduces the time complexity of checking type Reduces the time complexity of checking type and contextand context

Data types & data contexts grounded at Data types & data contexts grounded at hardware levelhardware level

RealOutput

SimulatedOutput

Real Environment (Implementation)

Simulated Environment (Model)

in

in'

out

out'

List ofConflicts

Translator

in out

SimulatedComponent

RealComponent

Reflection

Differencer

Execution Monitoring

Execution Monitoring

Program

Method

Data Model

Method

Method

Duplicated Data Model

Wrappers

Application Scripting

Application Tracking

Execution Monitor

Integrity Checks

Wrapper

Wrapper

Wrapper

Event Stream

Method Selection

Get event info

Get Next Cmd

Get Leg

Get Events

cmd

Get MovementGet Sortie

event

Add Event

Mission Plan

Add Additional Info

MissionPlan

Mission Plan

MissionPlan

Take Off?

Y N

Mission Plan

Mission Plan

Get Events

More Events?

Y N

Each component can be annotated with:

• Entry Events• Exit Events• Allowable Events

Control Flow

Data Flow

Tiara Software Level

Provenance Tracking

Provenance Tracking

• “Provenance Wrappers” imposed around computations

• Values are boxed in “TMS Like Structures”– Value– Support– Certainty

• Code rewritten to track flow through methods• Output boxed in TMS structure relating

outputs to inputs, computation performed, and people involved.

Provenance Based Operations

• Assessing reliability, trustability, accuracy of data– Bayesian propagation

• Revocation• Access Control• Trace Back and Drill Down• Diagnosis in the case of bad executions

AWDRAT

Recovery and

Regeneration

Adaptive Method

Selection

Trust Model: Behavior Compromis

es Attacks

Diagnosis

Architecture level

Execution Monitor

System Model

Application

Software

JavaWrappers

Model Compiler

Wrapper Synthesizer

Monitor Synthesizer

System DLL’s

SafeFamily Wrappers

Event Stream

Execution Discrepancies

Failure LocalizationCompromiseDescriptions

• Architectural monitoring• Wrapper synthesis• Diagnosis• Recovery and regeneration• Adaptive method selection• Trust modeling

The Trust Model and Recovery

• The Trust Model Includes Probability for Each Resource that it is in a compromised state.

• Diagnosis Updates the Trust Model• Trust Model is Read in Upon System Startup• Trust Model Guides method selection

TrustModel

Application

ExecutableCode

AWDRAT

Monitors

AWDRAT

Diagnostic

Service

Application

ExecutableCode

AWDRAT

DecisionTheoreticChoice

AWDRAT

DecisionTheoreticChoice

TrustModel

Tiara Application Demo

• Virtual Briefing Book• Built incrementally• Provenance for every entry

–Drill down

• Access control and degrading of info