DesigninganopensourceIoTHub:bridginginteroperabilityandsecuritygapswithMQTTandyourAndroiddevice

MelissaAdrianaSimoesSaialReal,HamedHaddadi

QueenMaryUniversityofLondon

AbstractWithconstantlyevolvinghardwareandincreasedcompetitivenessfrom

manufacturersintheconstructionoftheIoTenabledhome,thedifficultyinmanagingandsecuringthemultitudeofinternetenableddevicesatanyindividual’sdisposalisevergreater,withcompetingapplicationstailoredtomanageBluetoothdevices,Wi-FiDirectorNFCenabled“things”.Whilethemeansofconnectivityareeverincreasing,thelackofasinglestandardofIoTconnectivityaswellasthelackofasingleinteroperabilitysolutiondifficultconsumeradoptionofaninternetenabledhome.

Thesolutiontotheseissuesisherepresentedintheformofasingle,simple,user-friendlyinterfacethatcanbeintuitivelyusedbyanyconsumer.Pairingthisinterfacewithanoptimalcommunicationprotocolwillassistinbridgingtheinteroperabilitygapandprovidethenecessaryabstractionlayertofacilitatetheinterchangeofdataregardlessofwhichdeviceisbeingused.Thispaperproposesthatthesolutionforboththeseissueslieswithleveragingthecapabilitiesofmobiledevices,inthiscaseparticularlytargetingAndroid,pairedwithanintegrationofthelightweightcommunicationprotocolMQTT.IntroductionDesigninganIoThubisnotanewconcept:LeaandBlackstock[20]proposeditin2014aswellandAmazon’sAlexafacilitatestheconnectionstodifferentintelligentdevicesinthehome,actingasacentralhubformanagingdevicessuchasPhilipsHuelightbulbsandTP-LinkSmartPlugs.However,whatisrecentisthemotivationtoproposeanopensourcesolution.WithacademicpapersfrequentlydiscussingIoTmagementsolutionswithoutopensourcingcode,itwasnecessarytoprovideanaccessibleandtestablesolutionthatcouldbeexploredandtinkeredwithbyotherinterestedparties.Wewillshowcasethedifferentoptionsprovidedandtheonlycompetingopensourcesolutionthusfound–homeassistant.Thispaperwillthusshowcasethestepsinbuildingtheidealhubservice,andhowanyindividualcanleveragethepowerofanopen-sourceJavaAndroidapplicationaimedatfacilitatingthediscoveryofservicesprovidedbyInternetenableddeviceswithinalocalareanetwork.AfterwardswedemonstratehowsimpleitistoestablishacommunicationchannelbetweenanandroiddeviceandaMosquittobrokerusingtheMQTTProtocolandanAndroidapplicationprovidedbytheEclipseIoTproject.ThispaperwillfurtherexplorethecurrentoptionsprovidedforservicediscoveryinthecontextofIoT,themostrelevantprotocolsandarchitecturesusedinconnectingthesedevicesaswellastheattemptsthathavebeenmadeatestablishingastandardmeansofconnectivityinthescopeoftheInternetofThings.DefiningIoTThedefinitionofIoTvarieswidelyinacademia.ForthescopeofthispaperwebeginbydefininganIoTasanInternetenabledentity,followingtheconceptgivenbydeMeloetalin[1]of“allapplicationcomprisingobjectsordevicesthatcaninteractwithotherobjectsand

applicationsovertheinternet”.ThisinterpretationunderstandsIoTnottobenecessarilyphysical,sinceIoTapplicationscanbesimulatedusingservicessuchasAWSIoTorIBM’sBluemix.CoretothisdefinitionisthecapacityofIoTtoconnectwithdifferentobjects/applicationsandcarryoutfunctions,andso,anIoTdeviceishereconsideredasaphysicalentitywhileIoTreferstoamoregeneralconceptofaninterconnectedentity.AnothervalidinterpretationthathelpsusdefinethearchitectureinwhichIoTisintegratedistoproposenotjust“anIoT”buttoperceivetheInternetofThingsasthesystemofinterconnected“things”.ThismeansthatratherthanreferringtoIoTasindividualentities,thewordIoTisreferringtoawholecognitivesystem,where“things”contributedataandintelligence[2].Inthisapproach,a“thing”istheIoTentity,andthatthingcanbeadrone,anode,anintelligenttoasteroranyotherdeemed“intelligent”machine.TheIoTnetworkarchitectureinthissensedescribestheinteractionofthingswithinthissystem.Asimplifiedversionofthisarchitectureispresentedin[2]andstatesitsfourmaincomponentsasthethings(sensingdevices),acommunicationnetwork,acloudandtheback-endIoTapplications.ThedevicesusetheIoTapplicationstomakeuseoftheirservices,andthenreachthecloudviathecommunicationnetworktomakeuseofcloudservicessuchasdatastorage.Anillustrationofthisinteractionisalsoprovidedbytheauthors.

Figure1.IoTnetworkarchitecture[2]

ChallengestoIoTconnectivityWithover8billionconnecteddevicesatthetimeofwriting[3],thenumberofconnecteddevicesmayfailtomeetthecommonlyquotedpredictionofCisco’s2011report[4]of50billiondevicesfor2020,butitisundeniablethatIoTisquicklybecomingcommonplaceasthenumberofdevicesalreadysurpassestheworldpopulation.Thus,IoTbecomesarelevantsubjecttoresearch,togetherwiththetopicofhowweconnect,interactandhavedatacollectedbythesedevices.ThedialogueonthesemattershasbeenrecentlyintensifiedbythesecuritybreachesthathaveseenmillionsofIoTdeviceshijackedforthepurposeofDDoSattacks,whichhaveexposedcriticalsecurityflawsinthedesignandimplementationofIoTcommunicationprotocols.Onesuchexampleoftheseattacksisthe“Mirai”virus

whichhijackedover900thousandroutersofDeutscheTelekomcustomers[5]bytakingadvantageofatelnetvulnerability.Thesesecurityflawsareaconsequenceofboththedifficultyinimplementingencryptionondeviceswithconstrainedprocessingpower[17],aswellasaresultoftherapidexpansionofIoTtechnologywithoutestablishingastandardforasecureIoTarchitecture.Suchastandardisstillmissing[6],notduetolackofattemptstoestablishone-aswewillexploreinsectiontwo-butmainlyduetotherapidcreationofdifferentproductspriortoconsiderationforexpansion,securityandcompatibilitywithdifferenttechnologies.This,pairedwithadesireonthepartofcertainmanufacturers1tonotprovidecompatibilityacrossdifferentbrandsofdevices,hascausedahindrancetotheeffortofstandardisation.TheneedforastandardthatenablesbestsecuritypracticestoprotectIoTconsumersisthusthemotivationforthispaperandexplorationoftoolsthatallowtheconstructionofaneasy-to-useapplicationwhichaggregatesavailableIoTservicesinasingleinterface.CurrentstandardisationeffortsMultipleopenprotocolsappropriateforIoThavebeenrecognisedbystandardisationbodiesincludingtheEuropeanTelecommunicationsStandardInstitute(ETSI),TheOrganizationofStructuredInformationStandards(OASIS),theOpenMobileAlliance(OMA)andtheInternetEngineeringTaskForce(IETF).TheseincludeHTTP,CoAPandMQTT[7].Intermsofcommunicationprotocols,thesehavedifferentcomponentsthatcanbeintegratedintoapplicationstoallowfordevicediscoveryandforthedesignofanIoTsearchsystem.However,theseprotocolsdonotdefineasinglearchitecturalmodelastheycanbesimplyintegratedintodifferentIoTdesigninfrastructuresthatsupportthem.Promotingtheimplementationofprotocols,insteadofhardwaredependantcommunicationcomponents,signalsadeparturefromhowtraditionalcommunicationhasbeenestablishedbetweenIoT.Foryears,Bluetooth,ZigBeeandothershort-rangetransmissiontechnologieshavebeenusedasgatewaysforaccessingIoTdevicesandservices[16]butthetrendtowardscloudcomputingandservicevirtualisationhasrequiredadjustmentstobemadeonhowweconnecttoIoTtoallowforexpansibilityandIoTcloudaccess.FlexibleinteroperabilitycanbefacilitatedbytheuseofWirelesstechnologiesbeingintegratedintoIoTdevicestoallowdirectcommunicationbetweenthings,withouttheneedtobeconnectedviaarouter.ThisisthestandardpromotedbyWi-FiDirect,endorsedbytheWi-FiAlliance,whichallowsfordevicestotalktoeachotherdirectlyviaasoftwareaccesspoint[8].Ratherthanusingarouterorevenneedinganinternetconnection,devicescanconnecttoagroupofmultipledevicesormakeone-to-oneconnections.Onedevicedefinesthesoftwareaccesspointandbecomestheownerofagivendevicegroup.ThisenablescompatibilitywitholderWi-FidevicesthatdonothaveWi-FiDirect,withtheaddedbenefitthatWi-FiDirectalreadyintegratessecuritymechanismswithinitsspecificationandincludesWPA2protection[8].

1Apple’sproprietaryHomeKitsoftwareisanexample,asusersarerequiredtopurchaseadditionalhardwareinordertobridgethecommunicationwithdevicesfromdifferentmanufacturers.OneexampleofthisarethePhilipsHueIoTbulbs,whichhardwareisavailablefrom:https://www.apple.com/shop/product/HJE22VC/B/philips-hue-homekit-upgrade-bridge-for-current-hue-bridge-users

WhileWi-FiDirectiscertainlyanadvantageousapproachforsystemsthatareenabledtosupportthistechnology,itisnotwithoutitsfaults-authorsin[18]highlightadisadvantageofusingwirelesstechnologies,becausetheserequireanaccesspointtobesetupforWi-Ficommunicationstobeestablishedbetweendevices.Theauthorsalsoreflectonotherhardware,suchastheneedfordevicestoberunningthesameOSwhenitcomestoBluetoothcommunications.Asso,anidealsolutionwouldnotrelyonaparticulartechnologyforinterconnectivitybutinsteadwouldallowforanabstractionlayerfromtheunderliningtechnologyandpermitinteroperabilitybetweendifferenthardware.MostprotocolsintegratedintoIoTonlyrequirethecapacityofdevicestocommunicateusingHTTP/RESTmethods,whichintegrationintoIoTcommunicationlayerswillbefurtherexploredinthenextsection.Afeatureofprotocolsisrequiringtheirrespectiveimplementationstoprovideforsecurity,meaningsecurityconcernsareaddresseddifferentlywitheachimplementation.SimplyhavingaprotocoltoestablishcommunicationisnotenoughtoprogramanIoTinteroperabilitysolutionsinceanimplementationofeachprotocolisrequiredaspartofafullapplicationtobeprovidedasaservicetheconsumercanuse.Itissoimportanttounderstandhowtheseprotocolsfunctionasinteroperabilityenablersandcanbeintroducedintoapplicationdesign.CommunicationProtocolsforIoTconnectivityMachine-to-machine(M2M)communicationisenabledbythewebtechnologiesofHTTP/RESTthatexposeservicesusingHTTPtyperequestsandbyusingURIsasameanstoidentifyresources[10].WebtransferprotocolssuchasMQTTandCoAPenableapplicationtransferevenwhenresourcesarelimited[9],thusmakingtheseidealtoworkwithconstraineddevices-whicharedefinedbybeingcharacteristicallylowpoweredandhavingonlyafewkbofRAMmemory.ConstraineddevicesdonothavethecapacityforpeakoperatingsystemssuchasLinuxtoberuninthem.WheninteractingwithHTTP,CoAPprovidesalevelofabstractionthatavoidsusingspecificapplicationdatatoprovideinteraction,manytimesusinganintermediarytotranslatethedatatransmittedinbetweenbothprotocols[9].TheusageofURIstoidentifyresourcesbybothprotocolsalsofacilitatestheinterchangeabilityofcommunicationsandtrafficinterceptionsbetweenthem.AsCoAPreliesonRESTconnectivityitcanbeappliedregardlessofwhichhardwareisbeingusedtocommunicate,sinceclientscansimplyuseGETrequeststoaskforresourceupdatesfromtheservercontainingtheresource[14].Whiletherearemanydifferentoptionsforprotocolimplementations,theonechosenforthisprojectandwhichiscommonlyusedwithconstraineddevicesisthesimpledataexchangeserviceMQTT.CreatedbyIBMandArcomtofacilitateMachinetoMachinedataexchange,MQTTisalightweightpublish/subscribeprotocolthathasanacceptedstandardisedspecificationbyOASIS[15]andusesaclient/brokersystem,whichallowsfortwoormorebrokerstoconnectviaabridgingsystem.Bridgingallowsfortheconnectionofbrokersbyhavingoneofthebrokersinitiateabridgebydefiningatopicthatallinterestedbrokers/clientscansubscribeto.ThismethodalsoallowsforclientstosendmessagestoanMQTTbroker,andthoseclientscanalsosubscribetothemessagessenttothebrokerandreceiveupdatesnotifyingthemofnewmessages.AcommonbrokerimplementationusedwithMQTTisMosquitto[12],asitprovidesasolutionthatisalsoopensource,lightweightandcompatibleacrossdifferentplatforms.Itwasthebrokerimplementationofchoicebytheauthorsin[13]tocreateamessage

transmissionsystemthatreliespreciselyonthisMQTTandMosquittocombinationtoreliablyexchangemessagesinanIoTsetting.InordertouseMQTTwithaclientimplementation,awell-establishedoptionisprovidedbyEclipsePaho[38].PahohasmultipleopensourceclientlibrariessuchasJava,PythonandJavaScriptavailable,andAmazonalsoenablestheusageofthePahoMQTTwithWebSockettoconnecttoAWSIoT[11]-WebSocketisacommunicationprotocolthatopenscommunicationchannelsoverTCPconnections.WithinthenextsectionwewillexplorehowtousetheMQTTPahoJavaAndroidclienttopushnotificationsaboutdevicestoaMosquittobroker.Butfirstly,wewillexploredifferentapproachesthatintegratethedescribedprotocolsintothedifferentlayersoftheirrespectiveIoTmanagementsolutions.FormerproposedsolutionsandimplementationsThechallengeposedbyprovidingacommunicationstructurebetweenaservicelayeranddifferentIoTarchitecturescanbeaddressedbyusingacombinationofprotocolsandclientlibrariesandturningtheseintoanAPI.OneexampleisthesolutionproposeddeMeloSilvaetalin[1],intheformofanAPIbasedonUPnPstandards,usingRESTandSOAPrequeststoretrievedataandcreateobjectsoffthatdata,thenpassingthecreatedobjecttoacomponenthandlermodule.WhiletheAPIpresentsausefulsolutiontoexposeRESTservicesithasnotbeenincorporatedinacompleteapplicationnordotheauthorsmakeitavailableforuseviaanopensourcemeanssuchasGitHub,providingachallengeintermsoftestingthefunctionalityofthedescribedapplication.Outofthedifferentarchitecturedesignsdescribed,theseeminglymostconvenientfromaconsumerfacingperspectivewasthesuggestionofafullsolutionasanapplicationwithaneasytouseclientinterface,whichdescribesamodelfora“hub”managementsystem.Authorsin[19]proposethehuborgatewaymethodsasthosewithmostpromisetodeliverinteroperabilitybetweendevices,withanexampleofsuchassystemdescribedin[20].TheideapresentsanopensourcehubthatconnectsdifferentIoTbyallowingagatewayforinteroperabilityamongstthese.ThearchitectureofLeaandBlackstock’s[20]describedhubmodelcontainsadataaggregatorthatservesasanaccesspointtoservices.Intheirmodel,theauthorsimplementedaCKANdataharvestertoaggregatedatainformationaboutthingsandusetheWotKitAPI2tofindthesethings,ormorespecifically,tofindthesensorsthatdifferentIoThasforthepurposeoflocatingphysicalorvirtualIoTdevicecapabilities.TheinformationfrombothAPIsisthensentintheformofacatalogueofresources,whichisinterpretedusingtheHyperCatspecification,meaningIoTresourcesthathadbeenexposedbybothAPIsaredescribedasacatalogueofURIresources.Certaindifficultiesarepointedoutbytheauthorsregardingtheuseofthissystem:Mainly,whenqueryingtheHyperCatcatalogueofitemsitisnecessarytorequestspecificmetadatakeyvaluepairs,andsincenotallsensordataprovidedbythechosenWoTKitAPIsexposedinformationintheformofmetadatakeysandvalues,itwasnotalwayspossibletoqueryavailableIoTresourcesofftheIoTcatalogue.MovingontoworkthathasbeenrecentlypublishedontheIoTarena,apracticalexampleofamoderndevicediscoveryandmanagementimplementationishomeassistant[22].HomeassistantisapythonbasedopensourceIoTmanagementapplicationthathasasimplecommandlineinstallation.Oncealltheappdependenciesareinstalledandrunning,home2FurtherinformationabouttheWotKitAPIisavailablefromhttps://wotkit.readthedocs.io/en/latest/user/quickstart.html#quickstart

assistantprovidesastraightforwardinterfacetotheuser,displayingallthedevicesthesystemisabletofindwithinthenetworkrange.

Figure2.Home-assistantinterfacedisplayedafterthesystemlocatedoneoftheIoTdevicespresentinthenetwork,aRokuNowTVbox

Theservicediscoverymethodsimplementedbyhomeassistantuseacombinationoflibrariesthatsearchforcomponentsandadjusttotheneedofeachindividualcomponent.Consequently,thereareseparatecodelibrariesdependingonwhatresourceistobefound,withspecificcodelibraryextensionsandinstructionsforaddingdevicessuchasanAmazonFireTVStick3.Outoftheacademicsolutionsresearched,noneprovidedaccesstothecodeimplementationsoftheirrespectiveimplementations.Theonlycompletesolutionfoundduringtheresearchforthisprojectthatoffersanopensourcerepository,whichcodecouldbeinvestigatedandtested,wasthepythonbasedhome-assistant[22].ThereisthustheneedforanopensourcesolutionthatfacilitatescommunicationandtransparencybetweenIoTdevices,thusbetterbridgingboththetheorythatsupportstheapplicationdesignaswellasclearexplanationofthecomponentsthatenablethediscoveryandcommunicationofdeviceswithinagivennetwork.

DiscoveringservicesonaLAN:ThePortAuthorityApplication

ToassesstheefficiencyofthePortAuthorityapp,wecancomparethefounddevicesagainstthoseconnectedtoourhomerouter,andsotheleastwe’llexpectfromanefficientdiscoveryserviceissixconnecteddevices,thesameonesdisplayedconnectedtoourskyhomerouter:

3InstructionsonsettinguptheFireTVextensionareavailablefromhttps://home-assistant.io/components/media_player.firetv/

Figure 3. Home router listing of connected devices

PortAuthorityisanopen-sourcetoolwithanup-to-daterepositoryprovidedby[23].ThePortAuthorityAndroidapplicationrunsnetworkscansusingacombinationofanativeservicediscoveryAPIaswellasafewnativeAndroidmethods–AndroidhaslibrariesforNetworkServiceDiscoverywhichcansupportdiscoveringHTTPserviceswhenitsserviceTypeparametersaresetto“http._tcp”ordiscoveringprintertypeswithserviceTypesetto“_ipp._tcp”[24].Theapplicationusesasynchronousthreadingtechniquestomakethediscoveryprocessesrunfasteronthebackground.

TheresultsexposedallthedevicesconnectedtotheLAN,whilefurtherprovidingportsinformationoneachoftheexposedaddresses.Itdiscoverssevenhosts,sinceitlistsnotonlythedevicesconnectedonthenetworkbutalsoourskyhubrouter.Theinformationandimplementationprovidedwerethemostdetailedandquickesttorunoutofdifferentoptionstested,reasonwhythePortAuthoritynotoriouslystoodoutasanoptimaldiscoveryservicetosupportthestructureofanIoThomehub.

Figures6and7.PortAuthoritydiscoveryresults

ThenextstepsweretotrialourchosencommunicationprotocolbeforetestinghowtopushmessagesviatheMQTTbroker.

SettingupMQTTasamessagebrokerfortheIoTdiscoveryserviceTocreateanIoThubapplication,itisnecessarytointegrateamessagingprotocolthatcansearchandpushnotificationstodeviceswithinagivenLANoravirtualisedenvironment.CurrentsolutionsthatarecompatiblewithInternetofThingsdevicesneedtobelightweightduetothesimplicityofhardware,storageandmemorylimitationsofconstraineddevices.Theauthorsin[21]highlightfourmessagingprotocolsasmostsuitableforIoTcompatibility,namelyAMQP,MQTT,ZeroMQandZMPP.TheirpapercomparestheperformanceofthesemessagingprotocolsindealingwithpublishingandsubscriptionofIoTinavirtualisedenvironment.TheauthorsinthiscomparisonpaperdenotedtheabilityofMQTTtoperformaboveaveragefortransportingmultiplesensorloads,andsothechoiceMQTTapplicationderivedfromacombinationoffactors:MQTToffersawell-documented,up-to-dateandsimpletoconfigureprotocol,easilyadjustedtofittheneedsofanyIoTapplication.Further,MQTThasbeenadoptedbycompaniescurrentlyleadingtheIoTspace,namelytheonlineretailerAmazon,whichhasimplementedtheMQTTprotocolinitsIoTsolutionsalbeitwithafewmodifications[11],aswellassocialmediagiantFacebookcurrentlyusingMQTTforitsMessengerApp[25].MQTTworksonaclient/brokermodel.Consequently,thefirststeptousethiscommunicationprotocolwastosetupanonlinebrokerthatwouldallowformultiple

Figure 8. Running the Mosquitto broker and publishing/subscribing to topics

devicestocommunicateovertheinternet.Firstly,totesttheprotocolcapabilitieswesetupanopen-sourcesourcebroker,Mosquitto.Aftersettingupthebroker,aclientimplementationisnecessary,andtheoneusedwastheopensourcePahoJavaclient[38].

InstallingandlaunchingtheMosquittobrokerwasastraightforwardprocess,Figure8demonstratesitsfirstusageandactivation.

ThisusecaseexemplifiesthepropertiesoftheMosquittobroker,wherewesetMosquittotoruninoneTerminal,andsimulateaclientbycreatingatopicinanotherterminalwindowwithmosquitto_pub,andyetanotherclientonathirdterminalwindowsubscribingtothesametopicandreceivingupdatespublishedtothebroker.WecanalsoseeontherighthandsidehowMosquittoonlyopenstheconnectionforestablishingcommunicationandclosesitstraightafterthemessageispushed.ThisdemonstrateswhyMQTTwithMosquittoisusefulforconstraineddevices,astheconnectionisonlyestablishedforaslongasnecessarytotransmitthemessage,thusoccupyingminimumbandwidth.ARaspberryPiwasalsousedtokeeprunningtheMosquittobrokerforapplicationtesting,thiswayallowingfordifferentdevicesonthenetworktoconnecttoitsserverviaSSH.WealsotestedusingMosquittoonthePi3(Figure9.).

Figure 9. Pi 3 Mosquitto broker

SittingontopoftheTCP/IPstackmeansthatMQTTreliesonaclientopeningaTCPconnectiontoestablishanMQTTconnectionandsendmessagesacrosstheclientandbroker[38].RunningMQTTallowsforcommunicationtohappenbetweendevicesthatarerunningonthesameLANvianetworksockets,butcommunicationisalsopossiblefromoutsidetheLANbyusingwebsockets,whichestablishendpointsforinternetconnectionstooccurbetweenservicesanddevices.ByaddingawebsocketlistenertotheMQTTconfigurationitispossibletotransmitmessagesbeyondthelocalareaconnection[38],butforthescopeofthisprojectwewilllimitthemessagingtobetransmittedtodevicesinourLAN.

ThepurposeofthispaperwasnotonlytofacilitatethecreationofanIoThub,butalsotogatherameanstobetterexploretheservicesbeingofferedbyIoTsonagivenLAN,andsoperceivewhetherourdevicesareexposedtosecurityrisksbyhavingcertainportsopenandaccessibleviatheinternet.Thenextstepsinimprovingtheapplicationrequirecomprehendinghowbestsecuritypracticesareputinplace,andunderstandingwhichsecuritymeasuresarecurrentlypossibleinthescopeoftheIoTandMQTTinparticular.ThenextsectionintroducesthecurrentstateofsecuritythreatsforthesedevicesaswellasproposedmethodstotackleIoTmalwarethreats.

SecurityconcernshandlingIoTconnectionsThesusceptibilityofIoTdevicestohackingbecamefarmoreprominentinthelastquarterof2016,whentheMiraivirusharvestedmillionsofconnecteddevicestoformabotnetthatwouldbringdowntheDNSproviderDyn[26],thuscausingtheunavailabilityofservicesfromwebsitesincludingTwitter,NetflixandSpotify.ThisDistributedDenialofService(DDoS)attackoverwhelmedthecapacityoftheserviceprovidersthatusedDyn,whichwerefloodedwithdatasentandrequestedbythehijackedIoTdevices,sotakingadvantageofboththevulnerabilityofIoTdevicesandthevulnerabilityofDNS.

Figure 20. Configuration of the raspberry pi IP to act as a local server for the MQTT message exchange

Figure 21. Paho MQTT Client on an HTC One Android Device, sending messages to the raspberry pi mosquitto broker

MiraiprovidesaninterestingexamplewhenexposingvulnerabilitiesinthescopeofIoT.Atitscore,thevirushasasimplestructure:itscansforrandomIPaddressesofinternetconnecteddevicesthathaveweakpasswordpolicies,andusesalookuptableofcommonusername/passwordcombinationstoconnecttothesedevicesviabrute-force,thatis,byattemptingallpossiblepasswordcombinationsforthese[30][34].Themalwarestartsbyexploitingpasswordvulnerabilities,andtheninsertstheMiraibotintothevulnerabledevice.Thebotstayslatentuntilarequesttoattackagivenserverisemittedbythecommandandcontrol(C&C)server.Becauserebootingdeletesthevirusfromthedevice,Miraialsoprovidesa“keepalive”methodtopreventthis–althoughre-infection,whenavulnerabledeviceisconnectedtotheinternet,takesonlyanestimated5minutesbasedontheexperienceconductedby[31].TheMcAfeesecurityreportfromApril2017providesanillustrationoftheMiraiarchitecture[34].

AnotherMiraiparticularityisthatitalsoprovidesformeanstoexpelothervirusesfromthesamedevice.Itsearchesforcommonmalwareexecutables,deletesthemfromthesystemandclosesvulnerableportstopreventfurtherinfectionsandgaincompletecontrol:itcanterminateapplicationsboundtoSSHorTelnetports[34,p.18],andafterinfectionitclosesport22forSSH,80forHTTPand23forTelnet.

Figure24.MiraiarchitecturefromMcAfee'sthreatreport[34]

ThisparticularfeatureofMirai,closingports22,80and23,emphasiseswhyIoTdevicesareespeciallyvulnerable–IoTthatkeepsspecificportsopenforaccessibilityandremotemanagementwithoutrequiringanyformofauthenticationfacilitateshijackingofitsfunctions.Thisvulnerabilityiswhatpromptedthepreviouslymentionedattackthattookover900thousandrouters–DeutscheTelekomhadkeptTCPport7547opentoallowforremotemanagementoftherouters,withoutlimitinginternetconnectionsfromaccessingthisport.

Figure25.Miraicommandthatinitiatesmalwareattack[35]

Thefaultonport7547waspatchedbyanupdateprovidedbythecompany,whichcouldonlybedeliveredaftercustomersrebootedtheirrespectivedevicestoclearthevirusandreceivetheupdate[36].However,whileDeutscheTelekomcustomersmaynolongerneedtoworryaboutthisparticularvulnerability,combattingnewmalwarestrandssuchasMiraiderivativesremainsachallengesincemanyofthedevicesithijacks,especiallyolderIoTmodels,containoldhardwarethatcannotbeupdated,orwhichdefaultpasswordscannotbechanged[32].Websitessuchasinsecam(http://www.insecam.org/en/)exposeexamplesoftheseinsecurities,wherestreamsareprovidedfromonlineinsecurecameras,whereuserscanwatchlivecamerafeedsfromdifferentpartsoftheworld.

TacklingtheIoTsecuritythreatTheauthorin[26]highlightsthelackofastandardforIoTtohavesecurityintegratedasacompulsorypartofthesystemasoneofthereasonswhymanufacturersdonotinvestinthisfeaturewhenproducingsmartdevices.Suggestedalternativestothecurrentsystemincludetheuseofencryption,withoneexamplebeingtoreplacethewidelyusedTelnetwithSSH,which,despitealsohavingsecurityvulnerabilities4[27],providesasecurecommunicationsessionchannelthatincludessupportingRSAauthenticationandencryptionofauthentication.ProtocolssuchasTelnetandFTPontheotherhand,openlytransmitpasswordswithoutencryptingtheseoverthenetwork,insteaddisplayingthemascleartexttoanyonelisteningonthenetwork.

TotackletheMiraithreatspecifically,Caoetalin[32]describeamethodtouseMiraiasavirusexpeller,bychangingthecodestructureofthevirus,eliminatingattackfunctionsandimplementingaheart-beatmodulewhichalertsaserverastowhetherthevirusexpellerislive.Thisversionofthemalware,proposedasa“whiteMirai”,dependsonatimeframeagreedwiththedeviceusertodisconnectthedeviceandhavethevirusexpellerbeinstalledassoonasthedeviceisbackon.However,thisstilldependsontheuseractivelyassistinginremovingthethreatfromtheinfecteddevice,ratherthanhavingamore“passive”approachforusersthatareunawaretheirrespectiveIoTmayhavebeeninfected.

ThealternativetotheapproachproposedbyCaoetal.wastopushthemodifiedmalwarewithoutuserconsent,whichresultsinaviolationofuserprivacy.ThispremiseputsforwardanentirelydifferentdebateonthedifficultyofpatchingdevicesthathavebeenhijackedbyMirai-typeviruses–ifusersareunawareoftheirdevicesbeinginfectedinthefirstplace,andwilllikelyremainunawareifafixisdeployedtothedevice,theethicalconcernsofanexternalpartyaccessingaprivatedevicebecomeapointofdebate,eveniftheoutcomeofthesecuritypatchisaimedatprotectingtheusersprivacywhileinfringingonuserprivacy.Withthisconsiderationinmind,itsbesttodesignIoTsystemsthatcomplytobestsecuritypracticesandrequireauthenticationmechanismswiththeoriginalimplementation,ratherthanprioritisingeaseofconnectivitywhilesacrificingsecurity,whichisthetrademadebyUPnPdevicestodate.

Toapplybettersecuritypractices,weneedtoconsiderhowMQTTcommunicatesoverthenetwork.MQTTwasdesignedwithoutintegratedauthenticationmechanismssincetheimplementationofthesewouldnotallowfortheprotocoltobeaslightweightasintended.Authenticationmechanismsaresupportedbuttheseneedtobeimplementedontopoftheprotocol[28].Asforourbroker,inMosquittothedefaultconfigurationdoesnotuseanyformofauthentication,keepingtheport1883openandlisteningforconnections[27],buttherearemultipleoptionsavailabletoaddanextralayerofsecurity:ItispossibletoencrypttheconnectionbetweentheMQTTbroker,inthiscaseMosquitto,andtheMQTTclient.Forthis,oneoptionistosetupatrustedservercertificateontheBrokeranduseaservicesuchasCertbot(https://certbot.eff.org/about/)orOpenSSLtogeneratethenecessarysecuritycertificates.

4G.SchultzhighlightsthatparticularlyOpenSSHhasavastamountofvulnerabilities.

Aftersecuringtheconnectionwithatrustedcertificateweneedtosetupapasswordbyeditingtheconfigurationfileinside/etc/mosquitto/conf.d/default.conftodisableconnectionsthathavenotbeenauthenticated(anonymousconnections)andrequireapasswordfile:

ThefinalsteptosecuringthebrokeristoconfiguretheSSLcertificatesandchangethedefaultportthatMQTTislistening.AnexampleofaconfigurationforthisissuggestedinFigure13,retrievedfrom[37].

Figure26.Configurationofmosquittobrokertopointtocertificatesandencryptconnection

Port1883localhostisreplacedwithalisteneronport8883.Thedisplayedconfigalsodisplayswherethecertificatestoencryptconnectionswillbefound.

ItisthusstraightforwardtoencryptMQTTconnectionsandmodifythenativepasswordsusedbythebroker.AsfortheraspberrypialteringthedefaultpasswordassoonastheconnectionisestablishedforthefirsttimewasthebestapproachtosafeguardfromMiraiinfectionsonconnection.

Finally,consideringrelatedworkonthisareaandeffortstowardsamoresecureIoT,asecurityframeworkaimedspecificallyatMQTTisproposedin[29]wheretheauthorsimplementamechanismthatusesasymmetrickeyencryptionalgorithmstosignrootcertificateswithapublickeyanddecryptthesewithaprivatekey,toallowforclientstosubscribetoagiventopiconlyifthesepossessthecorrectprivatekeynecessarytodecryptthemessagessenttothattopic.TheauthorstestbothRSAandEllipticCurvealgorithmswithfeasibleresults.AmazonIoTalsocontainsimplementationsthatcommunicateoverMQTTanditprovidestheoptiontoencrypttrafficusingTransportLayerSecurity.

ConclusionThisworkwasmotivatedbytherecentpropagationofIoTdedicatedviruses,andfortheneedoffurthertransparencyinthemappingandmanagementofintelligentdevices.WehavethusdiscussedservicesthatcanactasastartingpointforafullIoThub,byallowingfortheexposureofdifferenttypesofdevices,whethertheseareconnectedviaIPorBluetooth,byallowingtheusertodiscovertheseviaasimple,user-friendlyinterface.

IdeallyfutureworkwouldinvolveadaptingtheMQTTservicetopushtopicstodevicesthatcansupportaversionoftheMQTTclient.However,thisworkalsorealisedthatduetothevariationsinthesoftwareofeachthing,itisnecessarytobuildspecificcommunicationmodulesthatcaninitiateconnectionstoeach“thing”.MQTThowever,canprovideanabstractionlayerontopofwhichfunctionalitycanbefurtherdevelopedtoindeedestablishconnectionstoeachIoTonagivenLAN.

Duringtheprojectdevelopment,wefurtherexploreddifferentapproachestointerconnectivityandsecurity,aswellastheintrinsicdifficultiesinsecuringthehardwareofconstraineddevices.ConflictsintheestablishmentofasinglestandardthatcangaintheconsensusofIoTdevicemanufacturers,alongwithdesignflawssuchasnotallowinguserstomodifydefaultpasswordsonolderdevicesordesignsthatoverlookinterconnectivitysecuritybykeepingportsopentoincomingunauthenticatedconnections,thesehaveallcontributedtowardsturninginternet-enableddevicesintomalware-enableddevices.

OnthefutureofIoTsecurity,thesubjectisevermorepertinentwiththegrowthofIoTdevicesalesandthesuccessofcommercialgiantssuchasAmazoninacceleratingthedeploymentofnewIoTsolutionstothemarket.ItispossiblethatthecommercialsuccessofAmazonwillfacilitateitsroleinadvocatingforbestsecuritypracticeswhenestablishingIoTconnections,andsoitsstandardsmayresonatemorequicklywiththeindustrythanthestandardsadvocatedbytheIEEEortheWi-FiAlliance–albeitsuchstandardmaynevertrulymaterialise.Asso,ratherthanwaitingforastandardorasingleauthoritytoleadsecurityefforts,thebestapproachtoenablesecurityiscentralisingthemanagementofourIoTdevicesthroughanIoTHuB:usinganeasyinterfaceandanapplicationthatcanprovideforanabstractionlayertoalldevicesandencryptconnectionstoIoT.Thiswouldbethesolutiontoavoidinterferenceandmalwareattacksfromtheoutsideworld,thusstrivingforabetter,moresecurefuturefortheInternetofThings.

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