1-Security-Goals-安全測試-教學課件

CHAPTER1

SecurityGoalsSlidesadaptedfrom"FoundationsofSecurity:WhatEveryProgrammerNeedsToKnow"byNeilDaswani,ChristophKern,andAnitaKesavan(ISBN1590597842;).Exceptasotherwisenoted,thecontentofthispresentationislicensedundertheCreativeCommons3.0License.

CHAPTER1

SecurityGoalsSlide1AgendaSevenKeySecurityConcepts:AuthenticationAuthorizationConfidentialityData/MessageIntegrityAccountabilityAvailabilityNon-RepudiationSystemExample:WebClient-ServerInteractionAgendaSevenKeySecurityConce21.1.SecurityIsHolisticPhysicalSecurityTechnologicalSecurityApplicationSecurityOperatingSystemSecurityNetworkSecurityPolicies&ProceduresAllThreeRequired1.1.SecurityIsHolisticPhysi31---Security-Goals-安全測試-教學課件41---Security-Goals-安全測試-教學課件51.1.2.TechnologicalSecurity(2)(OS&NetworkSecurity)Apps(e.g.servers)useOSformanyfunctionsOScodelikelycontainsvulnerabilitiesRegularlydownloadpatchestoeliminate

(e.g.WindowsUpdateforcriticalpatches)NetworkSecurity:mitigatemalicioustrafficTools:Firewalls&IntrusionDetectionSystems1.1.2.TechnologicalSecurity61.1.3.Policies&ProceduresEx:Socialengineeringattack-takingadvantageofunsuspectingemployees(e.g.attackergetsemployeetodivulgehisusername&password)GuardsensitivecorporateinformationEmployeesneedtobeaware,beeducatedtobesomewhatparanoidandvigilant1.1.3.Policies&ProceduresEx7SecurityConceptsAuthenticationAuthorizationConfidentialityData/MessageIntegrityAccountabilityAvailabilityNon-RepudiationSecurityConceptsAuthenticatio8ArchetypalCharactersAlice&Bob–“goodguys”Eve–a“passive”eavesdropperMallory–an“active”eavesdropperTrent–trustedbyAlice&BobAliceBobArchetypalCharactersAlice&B91.2.AuthenticationIdentityVerificationHowcanBobbesurethatheiscommunicatingwithAlice?ThreeGeneralWays:Somethingyouknow(i.e.,Passwords)Somethingyouhave(i.e.,Tokens)Somethingyouare(i.e.,Biometrics)1.2.AuthenticationIdentityVe101.2.1.SomethingyouKNOWExample:PasswordsPros:SimpletoimplementSimpleforuserstounderstandCons:Easytocrack(unlessuserschoosestrongones)PasswordsarereusedmanytimesOne-timePasswords(OTP):differentpasswordusedeachtime,butitisdifficultforusertorememberallofthem1.2.1.SomethingyouKNOWExamp111.2.2.SomethingyouHAVEOTPCards(e.g.SecurID):generatesnewpasswordeachtimeuserlogsinSmartCard:tamper-resistant,storessecretinformation,enteredintoacard-readerToken/Key(i.e.,iButton)ATMCardStrengthofauthenticationdependsondifficultyofforging1.2.2.SomethingyouHAVEOTPC121.2.3.SomethingyouAREBiometrics

Pros:“raisesthebar”Cons:falsenegatives/positives,socialacceptance,keymanagementfalsepositive:authenticuserrejectedfalsenegative:impostoracceptedTechniqueEffectivenessAcceptancePalmScan16IrisScan21RetinalScan37Fingerprint45VoiceId53FacialRecognition64SignatureDynamics721.2.3.SomethingyouAREBiomet131.2.4.FinalNotesTwo-factorAuthentication:Methodscanbecombined(i.e.ATMcard&PIN)Whoisauthenticatingwho?Person-to-computer?Computer-to-computer?Threetypes(e.g.SSL):ClientAuthentication:serververifiesclient’sidServerAuthentication:clientverifiesserver’sidMutualAuthentication(Client&Server)Authenticateduserisa“Principal”1.2.4.FinalNotesTwo-factorA141.3.AuthorizationCheckingwhetherauserhaspermissiontoconductsomeactionIdentityvs.AuthorityIsa“subject”(Alice)allowedtoaccessan“object”(openafile)?AccessControlList:mechanismusedbymanyoperatingsystemstodeterminewhetherusersareauthorizedtoconductdifferentactions1.3.AuthorizationCheckingwhe151.3.1.AccessControlLists(ACLs)Setofthree-tuples<User,Resource,Privilege>SpecifieswhichusersareallowedtoaccesswhichresourceswithwhichprivilegesPrivilegescanbeassignedbasedonroles(e.g.admin)UserResourcePrivilegeAlice/home/Alice/*Read,write,executeBob/home/Bob/*Read,write,executeTable1-1.ASimpleACL1.3.1.AccessControlLists(A161.3.2.AccessControlModelsACLsusedtoimplementthesemodelsMandatory:computersystemdecidesexactlywhohasaccesstowhichresourcesDiscretionary(e.g.UNIX):usersareauthorizedtodeterminewhichotheruserscanaccessfilesorotherresourcesthattheycreate,use,orownRole-Based(Non-Discretionary):user’saccess&privilegesdeterminedbyrole1.3.2.AccessControlModelsAC171.3.3.Bell-LaPadulaModelClassifications:TopSecretSecretConfidentialUnclassified3Rules/PropertiesSimpleproperty*-property(confinement)Tranquilityproperty1.3.3.Bell-LaPadulaModelClas181.4.ConfidentialityGoal:KeepthecontentsofcommunicationordataonstoragesecretExample:AliceandBobwanttheircommunicationstobesecretfromEveKey–asecretsharedbetweenAlice&BobSometimesaccomplishedwithCryptography,Steganography,AccessControls,DatabaseViews1.4.ConfidentialityGoal:Keep191.5.Message/DataIntegrityDataIntegrity=NoCorruptionManinthemiddleattack:HasMallorytamperedwiththemessagethatAlicesendstoBob?IntegrityCheck:Addredundancytodata/messagesTechniques:Hashing(MD5,SHA-1,…),Checksums(CRC…)MessageAuthenticationCodes(MACs)DifferentFromConfidentiality:A->B:“Thevalueofxis1”(notsecret)A->M->B:“Thevalueofxis10000”(BAD)A->M->B:“Thevalueofyis1”(BAD)1.5.Message/DataIntegrityDat201.6.AccountabilityAbletodeterminetheattackerorprincipalLogging&AuditTrailsRequirements:SecureTimestamping(OSvs.Network)Dataintegrityinlogs&audittrails,mustnotbeabletochangetrails,orbeabletodetectchangestologsOtherwiseattackercancovertheirtracks1.6.AccountabilityAbletodet211.7.AvailabilityUptime,FreeStorageEx.Dialtoneavailability,Systemdowntimelimit,Webserverresponsetime

Solutions:AddredundancytoremovesinglepointoffailureImpose“l(fā)imits”thatlegitimateuserscanuseGoalofDoS(DenialofService)attacksaretoreduceavailabilityMalwareusedtosendexcessivetraffictovictimsiteOverwhelmedserverscan’tprocesslegitimatetraffic1.7.AvailabilityUptime,Free221.8.Non-RepudiationUndeniabilityofatransactionAlicewantstoprovetoTrentthatshedidcommunicatewithBobGenerateevidence/receipts(digitallysignedstatements)Oftennotimplementedinpractice,credit-cardcompaniesbecomedefactothird-partyverifiers1.8.Non-RepudiationUndeniabil231.9.ConceptsatWork(1)IsDVD-FactorySecure?PCs-R-USBobDVD-FactoryorderspartsB2Bwebsite1.9.ConceptsatWork(1)IsDV241.9.ConceptsatWork(2)Availability:DVD-Factoryensuresitswebsiteisrunning24-7Authentication:Confidentiality:Bob’sbrowserandDVD-Factorywe