Understanding and Improving Security of the Android Operating System

290 Pages·2017·7.88 MB·English

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Dissertations - ALL SURFACE
December 2016
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Edward Paul Ratazzi
Syracuse University
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Ratazzi, Edward Paul, "Understanding and Improving Security of the Android Operating System" (2016).
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ABSTRACT
Successfulrealizationofpracticalcomputersecurityimprovementsrequiresanunderstanding
andinsightintothesystem’ssecurityarchitecture,combinedwithaconsiderationofend-users’
needsaswellasthesystem’sdesigntenets.InthecaseofAndroid,asystemwithanopen,
modulararchitecturethatemphasizesusabilityandperformance,acquiringthisknowledgeand
insightcanbeparticularlychallengingforseveralreasons.InspiteofAndroid’sopensource
philosophy,thesystemisextremelylargeandcomplex,documentationandreferencematerials
arescarce,andthecodebaseisrapidlyevolvingwithnewfeaturesandfixes.Tomakematters
worse,thevastmajorityofAndroiddevicesinusedonotruntheopensourcecode,butrather
proprietaryversionsthathavebeenheavilycustomizedbyvendorsforproductdifferentiation.
Proposingsecurityimprovementsormakingcustomizationswithoutsufficientinsightintothe
systemtypicallyleadstoless-practical,less-efficient,orevenvulnerableresults.Pointsolutionsto
specificproblemsriskleavingothersimilarproblemsinthedistributedsecurityarchitecture
unsolved.Far-reachinggeneral-purposeapproachesmayfurthercomplicateanalreadycomplex
system,andforceend-userstoenduresignificantperformanceandusabilitydegradations
regardlessoftheirspecificsecurityandprivacyneeds.Inthecaseofvendorcustomization,
uninformedchangescanintroduceaccesscontrolinconsistenciesandnewvulnerabilities.Hence,
thelackofmethodologiesandresourcesavailableforgaininginsightaboutAndroidsecurityis
hinderingthedevelopmentofpracticalsecuritysolutions,soundvendorcustomizations,and
end-userawarenessoftheproprietarydevicestheyareusing.
Addressingthisdeficiencyisthesubjectofthisdissertation.Newapproachesforanalyzing,
evaluatingandunderstandingAndroidaccesscontrolsareintroducedandusedtocreatean
interactivedatabaseforusebysecurityresearchersaswellassystemdesignersandend-user
productevaluators.Casestudiesusingthenewtechniquesaredescribed,withresultsuncovering
problemsinAndroid’smultiuserframeworkandvendor-customizedSystemServices.Finally,the
newinsightsareusedtodevelopandimplementanovelvirtualization-basedsecurity
architecturethatprotectssensitiveresourceswhilepreservingAndroid’sopenarchitectureand
expectedlevelsofperformanceandusability.
UNDERSTANDING AND IMPROVING SECURITY
OF THE ANDROID OPERATING SYSTEM
by
Edward Paul Ratazzi
B.S.,RensselaerPolytechnicInstitute,1987
M.S.,SyracuseUniversity,1992
M.S.,RensselaerPolytechnicInstitute,2006
DISSERTATION
Submittedinpartialfulfillmentoftherequirementsforthedegreeof
DoctorofPhilosophyinElectrical&ComputerEngineering
SyracuseUniversity
December2016
ThisisaworkoftheU.S.GovernmentandisnotsubjecttocopyrightprotectionintheUnited
States.Foreigncopyrightsmayapply.
DISCLAIMER
Theviewsexpressedinthisdissertationarethoseoftheauthoranddonotreflecttheofficial
policyorpositionoftheUnitedStatesAirForce,DepartmentofDefense,ortheU.S.Government.
v
Dedicatoamiononno,EdwardRatazzi,Sr.
—
Dedicatedtomygrandpop,HenryPaul,Jr.
vi
Acknowledgments
Mydeepestgratitudegoestothosearoundmewhomadecompletingthisdissertationpossible.
First,tomyadvisor,Prof.WenliangDu.EventhoughImetyouwithacareer’sworthofexperience
alreadybehindme,yourinsightsaboutconductingresearch,distillingproblemsandcritical
thinkinghavechangedmyprofessionallife.IwillconsidermyselfagreatsuccessifIcanpassalong
toothersevenafractionofwhatIlearnedfromyou.Iamespeciallythankfulforyourpatience,
approachability,friendlystyle,andunderstandingofmyoutsidecommitmentstoworkandfamily.
Tomydefensecommittee,Prof.JoonPark,Prof.Shiu-KaiChin,Prof.JianTang,Prof.YuzheTang,
andProf.HengYin,fortakingtimeoutofyourbusyschedulestoreadthisdissertation,provide
valuablefeedbackandserveonmycommittee.
TotheInformationDirectorateoftheAirForceResearchLaboratoryforitscommitmentto
career-longlearningandprofessionaldevelopment.Tomypastandpresentcolleaguesthere,
includingDr.WarrenDebany,Jr.,Dr.KamalJabbour,Dr.DavyBelk,JoeCamera,Lt.Col.David
Bibighaus,Dr.DanPease,andDr.LokYan.Yousupportedandguidedmyreturntograduate
school,andprovidedmuch-neededencouragementalongtheway.Iamparticularlyindebtedto
mysupervisorandfriend,JimPerretta.Forthelastfouryearsyouhaveshelteredmefrommany
day-to-daydistractionssothatIcouldfocusonconductinganddocumentingmyin-house
research.NowthatIamdone,Ihopetorisetothenewchallengesandopportunitiesyour
leadershipbringstome.
TothecurrentandformerstudentsoftheComputerSecurityResearchGroupatSyracuse,
vii
especiallyAmitAhlawat,FrancisAkowuah,AshokBommisetti,NianJi,Dr.YousraAafer,Dr.Xiao
Zhang,JiamingLiu,KailiangYing,YifeiWang,HaoHao,HaichaoZhang,andLushaWang.Iamin
aweofyourtechnicalskillsandgratefulforthecountlesshoursofdiscussionswe’vehad,bothin
groupmeetingsandone-on-one.Iwishyouallthebestandhopewecancollaborateagaininthe
future.
ToeveryoneattheGriffissInstitute,especiallyBillWolf,ReganJohnson,TracyDiMeo,Dr.Josh
White,andJimHanna.Youprovidedacomfortable,quietandwell-connectedenvironmentin
whichtostudy,research,collaborate,andwrite.Withoutyoursupport,completingthis
dissertationwouldhavebeentremendouslymoredifficultandlengthy.
Tomyparents,RandaandEdRatazzi.Byexample,youtaughtmethevalueofeducation,theneed
forperseverance,andtheimportanceofoptimism,allingredientsIfoundtobeessentialfor
completingmystudies.
Finallyandmostimportantly,tomywifeShirleyandchildrenEmilyandNicholas.Youencouraged
mewhenthingsweretough,cheeredmysuccesses,andmadecountlesssacrificesalongtheway.
Yourloveandconfidencearethecornerstoneofthisandallotheraccomplishmentsofmine.
Syracuse,NewYork
December2016
viii
Contents
Abstract i
ListofFigures xiv
ListofTables xvi
1 Introduction 1
1.1 Securityenhancementsproposedbythescientificliterature . . . . . . . . . . . . . . 3
1.2 Securityenhancementsavailabletoend-users . . . . . . . . . . . . . . . . . . . . . 4
1.3 ThesisandContributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.4 Dissertationorganization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Background 10
2.1 UniquenessofMobileDevices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2 TutorialonAndroidSecurity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.1 Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2.2 Download . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.3 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.2.4 Run-time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2.5 Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 AndroidAccessControlEvaluationMethodology 20
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.1 ThreatModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
ix