Experiences in Intel SGX research - SIGCOMM...Experiences in Intel SGX research Dongsu Han and...

ExperiencesinIntelSGXresearch

DongsuHanandSeongminKimKAIST

Jointworkwith:

ChanghoChoi,SohamDesai*,JuhyengHan,JaehyungHa,PreritJain*,JaeHyukLee,YoujungShin,BrentByounghoonKangandTaesooKim*

1APNet2017*

Trend1:SecurityandPrivacyCriBcalFactorsinTechnologyAdopBon

•  Demandsfor“security”and“privacy”areincreasing– WidespreaduseofTransportLayerSecurity(TLS)–  Popularityofanonymitynetworks(e.g.,Tor)–  UseofstrongauthenTcaTon/encrypToninWiFi

•  ExpectaTononsecurityandprivacyimpactsdesigndecisions:–  OperaTngsystem(iOS,Android)–  Apps/services(e.g.,messenger,adblocker)–  Networkinfrastructure(inter-domainSDN)

2APNet2017

•  Demandsfor“security”and“privacy”areincreasing– WidespreaduseofTransportLayerSecurity(TLS)–  Popularityofanonymitynetworks(e.g.,Tor)–  UseofstrongauthenTcaTon/encrypToninWiFi

•  ExpectaTononsecurityandprivacyimpactsdesigndecisions:–  OperaTngsystem(iOS,Android)–  Apps/services(e.g.,messenger,adblocker)–  Networkinfrastructure(inter-domainSDN)

Trend1:SecurityandPrivacyCriBcalFactorsinTechnologyAdopBon

3APNet2017

Trend2:CommodiBzaBonofTrustedExecuBonEnvironment

•  TrustedExecuTonEnvironment(TEE)–  IsolatedexecuTon:integrityofcode,confidenTality–  Remotea_estaTon

•  CommodiTzaTonofTEE–  TrustedPlaaormModule(TPM):Slowperformance–  ARMTrustZone:Onlyavailableforembeddeddevices–  IntelSodwareGuardExtension(SGX)1.NaTveperformance2.CompaTbilitywithx86

4

The commoditization of TEE brings new opportunities for networking.

APNet2017

SGX:IsolatedExecuBon

•  ApplicaTonkeepsitsdata/codeinsidethe“enclave”–  Smallesta_acksurfacebyreducingTCB(App+processor)–  Protectapp’ssecretfromuntrustedprivilegesodware(e.g.,OS,VMM)

5

CPUPackage

SystemMemory

Enclave

MemoryEncrypTonEngine(MEE)

Snooping

AccessfromOS/VMMEncrypted

code/data

APNet2017

Challenger

SGX:RemoteALestaBon

•  A_estanapplicaTononremoteplaaorm•  ChecktheidenTtyofenclave(hashofcode/datapages)

•  Canestablisha“securechannel”betweenenclaves6

TargetEnclave

QuoBngEnclave

SGXCPU

HostplaaormRemoteplaaorm1.Request

2.CalculateMAC

3.SendMAC

6.Sendsignature

CMAC

Hash

4.Verify 5.Signwithgroupkey[EPID]

APNet2017

SGXResearch:CurrentStatusandChallenges

•  SGXspecificaTonreleasedin2013.– SGXavailableinIntel’sSkylakemicroarchitecture(2015)– HardwareandsodwareimplementaTonsforSGXlagbehindtheirspecificaTons.

7

SGXCPUandSDKisnowavailable!But..•  SpecificaTonforSGX[revision1&2]isnotfullyavailableontheSGXhardware(onlyfuncTonaliTesinrevision1)

•  SGXtechnologyhasacomplexlicensemodel– Hardtoobtainfulllicense.

BarrierstoSGXresearch

APNet2017

Ourwork1.  Open-sourceemulatorplaaormforSGXresearch

-OpenSGX[NDSS16]

2.  WhatimpactdoesSGXhaveonnetworking?-AfirstStepTowardsLeveragingCommodityTrustedexecuTonEnvironmentsforNetworkApplicaTons[HotNets15] -EnhancingSecurityandPrivacyofTor’sEcosystembyusingTrustedExecuTonEnvironment[NSDI17]-SGX-Box:EnablingVisibilityonEncryptedTrafficusingaSecureMiddleboxModule[APNet17]

8

NetworkApplicaBons+TEE=?

•  WhatimpactdoesTEEhaveonnetworking?[HotNets15]

•  Previousefforts:AdopTngTEEtocloudplaaorm–  Haven[OSDI’14]:ProtectsapplicaTonsfromanuntrustedcloud–  VC3[S&P’15]:TrustworthydataanalyTcsinthecloud

9

NetworkApplicaBons

TEE

IntelSGX

Enhancedsecurity

Newdesignspace

NewfuncBonality

CaseStudies:ThreeApplicaBons

1.  Networkinfrastructure:Sodware-definedinter-domainrouTng[HotNets2015]

2.  Peer-to-peersystems:Toranonymitynetwork[NSDI2017]

3.  Middlebox:SecureMiddlebox[APNet2017]10

NetworkApplicaBons

TEE

IntelSGX

Enhancedsecurity

Newdesignspace

NewfuncBonality

Ourwork1.  OpenSGX[NDSS16]:Open-sourceemulatorplaaorm

forSGXresearch

2.  WhatimpactdoesSGXhaveonnetworking?-AfirstStepTowardsLeveragingCommodityTrustedexecuTon

EnvironmentsforNetworkApplicaTons[HotNets15] -

-EnhancingSecurityandPrivacyofTor’sEcosystembyusingTrustedExecuTonEnvironment[NSDI17]-SGX-Box:EnablingVisibilityonEncryptedTrafficusingaSecureMiddleboxModule[APNet17]

11

VirtualAddressSpace PhysicalAddressSpace

1.ECREATECreateanenclave

EPC

Memory(Untrusted)

PlaintextCode/Data

2.EADDAddpages

Code/Data

PlaintextCode/Data

Code/Data

PlaintextCode/Data

PlaintextCode/Data

4.EENTEREnterstheenclave 5.EEXITLeavestheenclave

Code/Data Code/Data

Background:EnclaveLifeCycle

13

3.EINITFinalizetheenclave

Enclave

ApplicaToncode

OpenSGX:DesignGoal

13

•  OfferacompleteplaaormforSGXresearch–  ToexploresodwareandhardwaredesignspaceofSGX–  TodevelopandevaluateSGX-enabledapplicaTons

•  Solvenon-trivialissuesonSGXsodwarecomponents–  Supportforsystemsodwareanduser-levelAPIs–  Familiarprogrammingmodelandinterface–  SecuredesigntodefendagainstpotenTala_ackvectors(e.g.,Iagoa_acks)

APNet2017

OpenSGX:ComponentOverview

14

•  EmulatedSGXhardware •  Enclaveloaderü  ü  ü 

SGXOSEmulaBon

SGXQEMU(HWemulaBon)

EnclaveProgram

OpenSGXtoolchain

Enclaveloader

SGXLibraries Trampoline

Stub

RunBmelibrary

EnclaveDebugger

PerformanceMonitor

•  OSemulaTonlayer

•  OpenSGXuserlibrary•  OpenSGXtoolchain

•  Enclavedebugger•  Performancemonitor

APNet2017

BinaryTranslaTon

OpenSGX:Approach

15

•  Usinguser-spaceemulaTonofQEMU–  BinarytranslaTontosupportSGXinstrucTons–  QEMUhelperrouTnetoimplementcomplexinstrucTons

HelperrouTne-Setregisters-OperatesSGXinstrucBons

QEMU Host(singleaddressspace)

Wrapper

Lib

Stack Heap

Enclave

Code

Data

EPC EPC

EPC

EPC EPC

…

…

enclu(){…

asm(“.byte0x0f”

“.byte0x01”

“.byte0xd7”

“rax=entry”

…}

Entrypoint

…if(opcode==0x0f01d7){helper_enclu();}

…

RIP

EENTER

HardwareEmulaBon

16

•  EmulatesSGXdatastructuresandSGXprocessorkey•  Enclavepagecache(EPC)memorymanagement–  Directmappingonvirtualmemory–  AccessprotecTon:Instrumentmemoryaccess

EPC_begin

EPC_end

enclave_begin

enclave_end

QEMU’stranslaTonrouTne

…Case(Load|Store){}

…

Virtualaddressspace

2.Prohibitothersenclaves’EPCtocurrentenclave’sEPC

1.ProhibitaccessfromhosttoEPC

InstrucBonSupport

17

•  OpenSGXsupportsmostinstrucTonsinthespecificaTon–  ExceptfordebuggingrelatedinstrucTons(e.g.,EDBGRD)–  Instead,itoffersrichenvironmentfordebuggingsinceitisa“so_wareemulator”(e.g.,GDBstub)

•  ProvidessimpleCAPIswhichwrapsassemblycode–  User-levelinstrucTons(ENCLU):accessibletouser-levelAPIs–  Super-levelinstrucTons(ENCLS):Requiressystemsupport

APNet2017

OSEmulaBonLayer

18

•  EmulateOStoexecutetheprivilegedSGXinstrucTons•  OS-neutralinterfacefor:

–  Bootstrapping(EPCallocaTon)–  EnclaveiniTalizaTon&pagetranslaTon–  DynamicEPCpageallocaTon

Systemcall DescripBonsys_sgx_init() AllocateEPCmemoryregion

sys_init_enclave() Createanenclave,AddandmeasureEPCpagessys_add_epc() AllocatesanewEPCpagetotherunningenclave

sys_stat_enclave() ObtainstheenclaveperformancestaTsTcs

APNet2017

NarrowinterfaceforSGXuserlib:TrampolineandStub

…

“Astrictandnarrowinterfacetohandleenclave-hostcommunicaTonusingshareddata/code”

19Enclave

Code

Heap

Lib

EmulatedOS Wrapper

Trampoline

(Shared)

…if(fcode==FUNC_MALLOC)alloc_tramp();…

fcodemcode

argument1

heap_end Stub:ShareddatatospecifythefuncBoncodeandarguments

Trampoline:Sharedcodetocalluser-levelAPIsinthewrapper

Heap

…malloc(100);…

malloc(){…sgx_exit(tram);…}

<SpecificaBon>fcode:FUNC_MALLOCmcode:EAUGsize:100

Stub

FULL!

TrampolineandStubInterface

Stub…

“Astrictandnarrowinterfacetohandleenclave-hostcommunicaTonusingshareddata/code”

20Enclave

Code…malloc(100);…

Heap

Libmalloc(){…sgx_exit(tram);…}

EmulatedOS

intsys_add_epc(){encls(EAUG,…);…

Trampoline

(Shared)

CallEAUG

heap_end

ERESUME

EEXIT

heap_end+4KFUNC_MALLOC

EAUG100

…if(fcode==FUNC_MALLOC)alloc_tramp();…

Wrapper

alloc_tramp(){…sys_add_epc();…}

User-levelAPIstorequestsystemcalls

SystemCall

OpenSGX:UsageExample

21

•  SimilartobuildingaCprogram–  Compile(Similartogcc)–  Sign(Usingprogrammer’skey)–  ExecuTon(Compiledenclavebinaryisloadedandexecuted)

APNet2017

voidenclave_main(){char*hello=“hellosgx!\n”;sgx_enclave_write(hello,strlen(hello));sgx_exit(NULL);}

$opensgx–chello.c$opensgx–shello.sgx–keysign.key$opensgxhello.sgxhello.confhellosgx!

Codeenclave_main()

Data“hellosgx\n”

0x0000EPC1

0x1000EPC2

Entrypoint:SigStruct:…

OpenSGX:CurrentStatus

22

•  Availableatgithub,releasedinMay2015–  14kLoC–  h_ps://github.com/sslab-gatech/opensgx–  11Contributors(Gatech,KAIST,Twosigma,MITRE,…)–  31uniquecloners,1,645Views(January,2016)–  Usedinacademia:S-NFV[SDN-NFVSecurity16],EdgefuncTons[SEC16],

SGX-enabledVMmigraTon[IEEESERVICES16],System-levelOpenSGX[Computers&Security17],…

•  Ourcurrentcommunity

APNet2017

Ourwork1.  OpenSGX[NDSS16]:Open-sourceemulatorplaaorm

forSGXresearch

2.  WhatimpactdoesSGXhaveonnetworking?-AfirstStepTowardsLeveragingCommodityTrustedexecuTon

EnvironmentsforNetworkApplicaTons[HotNets15] -

-EnhancingSecurityandPrivacyofTor’sEcosystembyusingTrustedExecuTonEnvironment[NSDI17]-SGX-Box:EnablingVisibilityonEncryptedTrafficusingaSecureMiddleboxModule[APNet17]

23

Toranonymitynetwork

24

•  Tor:themostpopularanonymitynetworkforInternetusers–  Helpsuserstodefendagainsttrafficanalysisandkeepuser’sprivacy(e.g.,whatsitesyouvisit,IPaddress)[fromTorproject,www.torproject.org]–  Freelyavailableasanopensource–  1.8millionusersonadailybasis

*fromOnionview,h6ps://onionview.codeplex.com/

APNet2017

ThegeographiclocaTonofTorrelays*

Tornetwork:Threatmodel

25

•  Tor’sThreatmodel–  Torisavolunteer-basednetwork:Torrelaysarenottrusted

CanobservesomefracBonofnetworktraffic

CanrunaTorrelaysofhisown

CancompromisesomefracBonofTorrelays

Entry Middle Exit Torclient DesTnaTon

Plain-text

TLSchannel TLSchannel TLSchannel

•  3-hoponionrouTng:asingleTorenTtycannotknowbothclientandserver

ProcessingUnit:Cell(512Bytes)

APNet2017

LimitaBonsofTor

26

Entry Middle Exit Torclients

DesTnaTon

Plain-text


ALackerscanmodifythebehavior

GivefalseinformaTontoothers

Modifyorinjectthecell

Bandwidth20MB/s150MB/s

Inflated!

ProcessingUnit:Cell(512Bytes)

InformaBonvisibletoaLackers

Cell: header

DemulTplexandidenTfyacircuit

Cell

Cell

APNet2017

SGX-Tor:LeveragingIntelSGXonTor

27

IntelSGX

Improvedtrustmodel

OperaBonalprivacy

PracBcalityTornetwork

Middle

Improvedtrustmodel OperaBonalprivacy PracBcality•  SpellsoutwhatuserstrustinpracTce

•  ProvidesulTmateprivacy

•  ProtectssensiTvedataandToroperaTons

•  PreventsmodificaTonsonTorrelays

•  Thechanceofhavingmorehardwareresourcesdonated

•  Incrementallydeployable

•  CompaTbility

SGX-Tor

APNet2017

Userprocess(TorapplicaBon)

SGX-Tor:DesignandImplementaBon

28

Enclavememory

SSLLibrary

ALestaBonModule

SealingModule

Seals/unsealsprivatedata

Integritycheck

Torcode/data(Core)-CircuitEstablishment-Hiddenservice-VoTng-EncrypTon/DecrypTon-Cell/ConsensuscreaTon

Crypto/TLSoperaTonsSecurelyobtainstheentropyandTmevalue

EncryptsandstoresthesensiTvedataoutsidetheenclave

ValidatestheenclavehashoftheTorprogram

APNet2017



29

Enclavememory

SSLLibrary

ALestaBonModule

SealingModule


Integritycheck


Crypto/TLSoperaTons

SystemCall

EnclaveCreaTon

Trusted Untrusted

EnclaveiniTalizaTon

StandardLibrary(glibc)

Torcode/data(Untrusted)

SGXRunBmeLibrary

Applica0on

ECALL

OCALLRequestsystem

services

OCALL/ECALLWrapper



30

Enclavememory

SSLLibrary

ALestaBonModule

SealingModule


Integritycheck


Crypto/TLSoperaTons

SystemCall

EnclaveCreaTon

Trusted Untrusted

EnclaveiniTalizaTon

StandardLibrary(glibc)

Torcode/data(Untrusted)

SGXRunBmeLibrary

Applica0on

ECALL

OCALLRequestsystem

services

OCALL/ECALLWrapper

Narrowinterface

Sanitychecking1.  Argumentlength2.  Addressrange

ALacksdefeatedbyusingSGX-Tor

31

Replay CellcounBng

DirectoryauthoriBes

Maliciousrelay(modifiedTor)

1.BWscanning 2.Detectscanning 3.ReportfakeBW 4.Create

consensusdocument

AdverTsedBWInflated!

2.BandwidthinflaBon

1.TaggingaLack

APNet2017


DesTnaTon

Plain-text


ALacksdefeatedbyusingSGX-Tor

32

Replay CellcounBng

DirectoryauthoriBes

Maliciousrelay(modifiedTor)

1.BWscanning 2.Detectscanning 3.ReportfakeBW 4.Create

consensusdocument

AdverTsedBWInflated!

2.BandwidthinflaBon

1.TaggingaLack

APNet2017


DesTnaTon

Plain-text


ALractmoreclients!

ALacksdefeatedbyusingSGX-Tor(Cont.)

33

-accesssensiBvedata -modifythecodeALackerscannot

ALacksdefeated/miBgatedbySGX-Tor•  CircuitdemulTplexing[S&P06]•  BandwidthinflaTon[PETS07,S&P13]•  Tagginga_ack[TON12,CCS12,S&P13]

…

Entry Middle Exit Torclients DesTnaTon

Plain-text


Enclave

Circuitestablishment

CellcreaTonEncrypTon/DecrypTon

Onion/SSLkeycreaTon

Enclave EnclaveEnclave

Cell

Circuitdescriptor

Privatekeys

SGX-Torisanopensource:h_ps://github.com/KAIST-INA/SGX-Tor

PerformanceevaluaBon

34

•  SGX-Torperformance:WANse�ng–  EstablishaprivateTornetwork–  FortherealisTcscenario,weconsiderthe“localityofrelays”(Asia,EU,U.S.West,U.S.East)

00.20.40.60.81

0 250 500 750 1000

CummulaT

veProb.

Time-to-first-byte(ms)

10MB

100M

B

0 30 60 90 120

HTTPSHTTP

HTTPSHTTP

Throughput(Mbps)

FileSize

(MB)

client

server

Entry(KAIST)

Middle(Cloud)1.EU2.U.S.West3.U.S.East

Exit(Gatech)

<EvaluaBonenvironment>

:SGX-Tor :OriginalTor

11.9%degradaTon 3.9%addiTonallatency

Enclave Enclave

OurEarlyLessonsonSGXresearch

•  PerformanceoverheadscausedbyusingSGX–  EPCPaging(limitedmemoryspace:<200MB)–  Contextswitch(foreachOCALL)

•  WhilebuildingSGX-basedsystem,weshould–  Reduceenclavesizeasmuchaspossible– MinimizecopyingalreadyencrypteddatatoEPC(e.g.,SSL-encryptedpacket)

–  Seallargedatastructuresthatareusedinfrequently

35APNet2017

OurEarlyLessonsonSGXresearch(Cont.)

•  SecurityissueswhilebuildingSGXsystems– Narrowinginterfacetoreducea_acksurfaceandsanitycheckingforinput/outputarguments

– Newa_ackscenarioscausedbyassumingmalicioussystemsodware(e.g.,bandwidthinflaTonbyOSinSGX-Tor)

•  Asaresultofourexperience,wereleaseSGX-portedOpenSSLasanopensource–  h_ps://github.com/sparkly9399/SGX-OpenSSL

36APNet2017

Conclusion•  WedesignandimplementOpenSGX,fullyfuncTonalandinstrucTon-compaTbleSGXemulator

•  CommodiTzaTonofTEEbringsnewopportuniTesfornetworkapplicaTons

•  Ongoingwork:ApplySGXtoNetworkFuncTonVirtualizaTon– BuildingasecuremiddleboxbyleveragingSGX– WillbepresentedinAPNet2017(SGX-Box)

37APNet2017

38APNet2017

OurEarlyLessonsonSGX

39

•  MisconcepBonsonSGX–  SGXfordesktop-likeenvironment:NeedssecureI/Ochannel(integraTonwithhardwaretechnologysuchasIntelIPT)

–  NeedEPIDsupportforremotea_estaTon

•  MalicioususeofIntelSGX– MalwaremightbepossiblebyabusingtheisolaTonproperty–  FailsontradiTonalsignature-basedAVprograms

APNet2017

Comparison:IntelSGXvsOpenSGX

40

IntelSGX OpenSGX Type Hardware SodwareEmulator

InstrucTons 16ENCLS,8ENCLU 13ENCLS,8ENCLU(Exceptdebugging)

Datastructures Specified ○

Paging Pagetable Directmapping

Systemsodware Notspecified UserlevelemulaTon

UserlevelAPIs SDKisavailable(OnlyforWindows) ○

Enclave

DefenseagainstIagoaLacks

41

•  Iagoa_acks[ASPLOS’13]:MaliciousOStriestosubverttrustedapplicaTonbyincorrectbehaviorex)addsincorrectEPCpageforheap

…malloc();

…

ApplicaTon In-enclaveLib

EmulatedOS

Wrapper Stubheap_endcur_heap_ptrvoid*malloc(intsize){

if(cur_heap_ptr==heap_end){stub->mcode=EAUG;exit(trampoline);}

Trampolinemalloc_tramp(){sys_add_epc();}

enclu(EACCEPT,…); intsys_add_epc(){…}

BadEPCpage

Detect!

MemoryStateofOpenSGXProgram

42

SGXOSEmulaBon

QEMUSGX

Userprocess(singleaddressspace)

ENCLS(e.g.,EINIT)

PackageInfoEntrypointMeasurementKey…

SGXLib Trampoline

Stub Wrapper

Lib

Stack Heap

EnclaveProgram

Code

Data

EPC EPC

EPC

EPC EPC

…

…

Privilegeboundary

Systemcallsboundary

ENCLU(e.g.,EENTER)

ENCLU(e.g.,EEXIT)

Systemcall(e.g.,sys_sgxinit())

Conclusion

43

•  WedesignandimplementOpenSGX,fullyfuncTonalandinstrucTon-compaTbleSGXemulator

•  AsashowcasingapplicaTon,wedevelopSGX-enabledTortoenhancethesecurityandprivacy

•  OpenSGXoffersopportunitytoleverageallcomponentsofSGXfortheresearch–  HardwaresemanTcs(e.g.,encrypTonschemeofMEE)–  Systemsodware,enclaveloaderanduser-levelAPIs–  RedesigningunforeseensecurityapplicaTons(e.g.,Tor)

APNet2017

Trend:CommodiBzaBonofTEE

44

•  TrustedExecuTonEnvironment(TEE):HardwaretechnologyfortrustedcompuTng

OS(untrusted)

ApplicaTon(untrusted)

Securecontainer IntegritycheckingàPreventsbehaviormodificaTon

Modified Torcode

•  IntelSGX:apromisingTEEtechnologyforgenericapplicaTons–  NaTveperformanceinthesecuremode–  AvailableonIntelSkylakeandKabylakeCPU

Cannotaccessdata,flowcontrolXàProtectsthesecrecyoftheprogram

edit

Original

APNet2017

Tornetwork:Threatmodel(Cont.)

45

DirectoryauthoriBes

•  Carefuladmission•  Behaviormonitoring

Torclient DesTnaTon AnonymityBroken!

APNet2017


46


… •  Havingalargenumberofrelays

Out-of-scope:network-leveladversary(controlsalargefracTonofnetwork)

1.  Currentlyruns~10,000relays

2.  Large-scaletrafficcorrelaTonisbelievedtobeverifydifficultinpracTce

APNet2017

DirectoryauthoriBes

•  Carefuladmission•  Behaviormonitoring


47

Out-of-scope:network-leveladversarywhocancontrolsalargefracBonofTor

network

1.   Currentlyruns~10000relays

2.   Large-scaletrafficcorrelaBonarebelievedtobeverifydifficultinpracBce

However, Tor is still vulnerable to many types of attacks under its traditional threat model

APNet2017


… •  Havingalargenumberofrelays

DirectoryauthoriBes

LimitaBonsofTor

48

Problem1.Torrelaysaresemi-trusted–  AuthoriTescannotfullyverifythebehaviorsofthem

Problem2.EvenaLackerscontrolafewTorrelays,theycan–  AccessinternalinformaTon(circuitidenTfier,cellheader,…)–  Modifythebehaviorofrelays(DDoS,packettampering,…)

Modifyingthebehavior

AccessinginternalinformaBon

•  MaliciouscircuitcreaTon[Security09,CCS11]•  Snipera_ack[NDSS15]•  Badapplea_ack[LEET11]

•  HarvesTnghiddenservicedescriptors[S&P13]

•  CircuitdemulTplexing[S&P06]•  WebsitefingerprinTng

[Security15]

Both

<Low-resourceaLacks> •  tagginga_ack[ICC08,TON12,

CCS12,S&P13]•  BandwidthinflaTon[PETS07,

S&P13]•  ControllingHSDir[S&P13]

LimitaBonsofTor(Cont.)

49

ToaddresstheproblemsonTor,1)Fundamentaltrustbootstrappingmechanism2)AdvancedtrustmodeltoverifyuntrustedremoteparTesarerequired

APNet2017


DesTnaTon

Plain-text


SGX-Tor:LeveragingIntelSGXonTor

50

IntelSGX

Improvedtrustmodel

OperaBonalprivacy

PracBcalityTornetwork

Middle

Improvedtrustmodel OperaBonalprivacy PracBcality•  SpellsoutwhatuserstrustinpracTce

•  ProvidesulTmateprivacy

•  ProtectssensiTvedataandToroperaTons

•  PreventsmodificaTonsonTorrelays

•  Thechanceofhavingmorehardwareresourcesdonated

•  Incrementallydeployable

•  CompaTbility

SGX-Tor

APNet2017

àReducesthepowerofana_ackerwhocurrentlygetsthesensiTveinformaTonbyrunningTorrelays

àRaisesthebarforToradversarytoatradiTonalnetwork-leveladversary(onlypassivelyseetheTLSbytestream)

SGX-Tor:ThreatModel

51

•  OnlytruststheunderlyingSGXhardware&Torcodeitself•  Donotaddressnetwork-leveladversaries:whocanperformlarge-

scaletrafficanalysis•  Outofscope:VulnerabiliTesinTorcodes,SGXsidechannela_acksàMiTgatedbyrecentSGXresearch:Moat[CCS16],SGX-Shield[NDSS17],T-SGX[NDSS17]

OS(untrusted)

ApplicaTon(untrusted)

Enclave

CPU

Powerfulnetwork-leveladversary:out-of-scopeTCB:Enclave+CPUpackage

<SGXThreatmodel> <TorThreatmodel>

NewfuncBonality:AutomaBcadmission

52

•  IntegrityverificaBonofrelays(DirectoryauthorityàOnionRouter)–  AutomaTcallyadmits“unmodified”and“SGX-enabled”relays–  Improvedtrustmodel:currentimplicittrustmodelturnsintotheexplicittrust

model

Directoryauthority

Torrelays

Expectedhash Admit(matchsuccess)

A_estaTonfail(notSGX-enabled)

A_estaTonfail(badhash)

Enclave

EnclaveRemote

A_estaTon

Enclave

Nickname:OR1

Nickname:OR2

Nickname:OR3

Consensusdocument

(modified)

name:OR1BW:20MB/sfingerprint:….

NOTE:TorusesthesamebinaryfordirectoryauthoriTes,Torrelays,andclientproxies

APNet2017

Incrementaldeployability

53

•  SGX-Tor’sbasicassumpBon:“AllrelaysandauthoriTesareSGX-enabled”

•  SGX-Torsupportsinteroperability–  Allowsadmissionofnon-SGXrelayswithoutremotea_estaTon–  SGX-enabledclientscangetthelistofSGX-TorrelaysfromSGX-enabledauthoriTes

Entry Middle Exit Torclient DesTnaTon

Enclave Enclave Enclave

Enclave … Enclave EnclaveDirectoryauthoriTes

RemoteA_estaTon

Enclave

Enclave

APNet2017

ImplementaBondetail

54

•  Engineeringefforts–  SupportforWindows/Linux(basedonIntelSGXSDK)–  SGX-portedlibraries:OpenSSL,libevent,zlibc–  SGX-Torisanopensource:Availableath_ps://github.com/KAIST-INA/SGX-Tor

•  TrustedCompuTngBase(TCB)size–  TCBsizeofHaven:Morethan200MB(maximumenclavesize:128MBinWindows)

–  3.8xsmaller(320KLoCvs1,228KLoC)thanGraphene(opensourcelibraryOSforSGX)

APNet2017

EvaluaBon

55

1)WhatkindofsensiBvedataofTorisprotectedbySGX-Tor?2)WhatistheperformanceoverheadofrunningSGX-Tor?3)HowcompaBbleandincrementallydeployableisSGX-TorwiththecurrentTornetwork?

•  Environmentalsetup–  SGXCPUs:IntelCorei7-6700(3.4GHz)andIntelXeonCPUE3-1240(3.5GHz)–  ConfiguraTon:128MBEnclavePageCache(EPC)–  RunningTorinWindows,FirefoxasaTorbrowser(intheclientproxy)–  EstablishaprivateTornetworkusingchutney

APNet2017

WhatisprotectedbySGX-Tor?

56

CurrentTor Network-leveladversary SGX-Tor

TCP/IPheader Visible Visible Visible TLS-encryptedbytestream Visible Visible Visible

Cell Visible Notvisible Notvisible CircuitID Visible Notvisible Notvisible

VoTngresult Visible Notvisible Notvisible Consensusdocument Visible Notvisible Notvisible

Hiddenservicedescriptor Visible Notvisible Notvisible Listofrelays Visible Notvisible Notvisible Privatekeys Visible Notvisible Notvisible

APNet2017

00.20.40.60.81

0 1 2 3Cu

mmulaT

ve

Prob

. HiddenServiceThroughput

PerformanceevaluaBon(Cont.)

57

•  End-to-endclientperformanceofSGX-Tor(usingTorbrowser)–  Weblatency:VisiTngAlexaTop50websites–  Hiddenservice:HTTPfileserver(downloading10MB)

00.20.40.60.81

0 50 100 150

CummulaT

ve

Prob

.

WebpageLoadingTime(s)


3.3%degradaTon 7.4%addiTonallatency

SGX-Tor:13.2sOriginal:12.2s

SGX-Tor:1.30MbpsOriginal:1.35Mbps

APNet2017

CompaBbilitywithvanillaTor

58

•  Long-running:AdmitSGX-TorrelaysinthevanillaTor–  Collectedresultsfortwoweeks

AdverBsedbandwidth* MiddleselecBonProbability NetworkI/Obandwidthpersecond


Fast Stable

*Fromh_ps://collector.torproject.org/

ServesTortrafficwell ActuallyselectedbymulTpleTorusers

Listedintheconsensusdocument

APNet2017

Conclusion

59

•  WedesignandimplementSGX-TorbyleveragingcommodityTEEanddemonstrateitsviability–  Givesmoderateperformanceoverhead–  ShowsitscompaTbilityandpossibilityofincrementaldeployment

•  SGX-TorenhancesthesecurityandprivacyofTorby–  DefendingagainstexisTnga_acksonTor–  BringingchangestothetrustmodelofTor–  ProvidingnewproperTes:automaTcadmission

•  Availableatgithub!(h_ps://github.com/KAIST-INA/SGX-Tor)

APNet2017

On-GoingWork

•  ApplySGXtoNetworkFuncTonVirtualizaTon– RunningmiddleboxesonactualSGX-enabledCPU– WillbepresentedinAPNet2017(SGX-Box)

•  Enhancingthesecurityandprivacyofsodware-definedinter-domainrouTng

60APNet2017

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