Windows VistaWindows VistaSystem IntegritySystem IntegrityTechnologiesTechnologies

WCI 442WCI 442

Why?

The bad guys are everywhere!The bad guys are everywhere!

They literally want to do you harmThey literally want to do you harmThreats exist in two interesting places—Threats exist in two interesting places—

Online: system started and shows a login screen or a user Online: system started and shows a login screen or a user isislogged inlogged inOffline: system is powered down or in hibernationOffline: system is powered down or in hibernation

Policies must address bothPolicies must address both

Cool stuff!Cool stuff!

Code integrity: protection against online Code integrity: protection against online attackattackBitLocker (secure startup): protection BitLocker (secure startup): protection against offline attackagainst offline attackWindows service hardeningWindows service hardeningMandatory integrity controlMandatory integrity controlInternet Explorer protected modeInternet Explorer protected mode

Protect the OSWhen Running

The threatsThe threats

Trojan that replaces a system file to install a Trojan that replaces a system file to install a rootkit and take control of the computer rootkit and take control of the computer (e.g. Fun Love or others that use root kits)(e.g. Fun Love or others that use root kits)Offline attack caused by booting an Offline attack caused by booting an alternate operating system and attempting alternate operating system and attempting to corrupt or modify Windows kernel filesto corrupt or modify Windows kernel filesThird-party kernel drivers that are not Third-party kernel drivers that are not securesecureRogue administrator who changes kernel Rogue administrator who changes kernel mode code to hide other actsmode code to hide other acts

Code integrityCode integrity

Validates the integrity of certain OS filesValidates the integrity of certain OS filesImplemented as a file system filter driverImplemented as a file system filter driverHashes stored in system catalog or in X.509 Hashes stored in system catalog or in X.509 certificate embedded in filecertificate embedded in file

Also validates the integrity of the boot Also validates the integrity of the boot processprocess

Checks the kernel, the HAL, boot-start driversChecks the kernel, the HAL, boot-start drivers

If validation fails, image won’t loadIf validation fails, image won’t load

What does it check?What does it check?

All kernel mode code (All kernel mode code (x64 onlyx64 only))All code loaded into a protected processAll code loaded into a protected processModules implementing cryptographic Modules implementing cryptographic functionsfunctionsModules loaded into the software licensing Modules loaded into the software licensing serviceservice

More on kernel mode codeMore on kernel mode code

x6x644

All kernel mode code must be signed or it won’t All kernel mode code must be signed or it won’t loadloadThird-party code must be WHQL-certified or Third-party code must be WHQL-certified or contain a certificate from a Microsoft CAcontain a certificate from a Microsoft CANo exceptions, periodNo exceptions, periodApplies to drivers, utilities, anything in the kernelApplies to drivers, utilities, anything in the kernel

x3x322

Signing applies only to drivers shipped with Signing applies only to drivers shipped with WindowsWindowsCan control by policy what to do with third-partyCan control by policy what to do with third-partyOther unsigned kernel mode code will loadOther unsigned kernel mode code will load

More on protected processesMore on protected processes

Only one right now: Media FoundationOnly one right now: Media Foundation

Loaded binaries are codecsLoaded binaries are codecsMicrosoft-supplied: signed by MicrosoftMicrosoft-supplied: signed by MicrosoftThird-party: signed by a Windows Media DRM Third-party: signed by a Windows Media DRM certificatecertificate

Affects potential playback of next-Affects potential playback of next-generation high definition protected contentgeneration high definition protected content

Content and/or playback app control what to do Content and/or playback app control what to do in presence of unsigned kernel mode driversin presence of unsigned kernel mode drivers

Code integrity non-goalsCode integrity non-goals

Protecting from attackers with physical Protecting from attackers with physical accessaccessVerifying the integrity of NTLDRVerifying the integrity of NTLDR

Requires secure startup on TPM-enabled Requires secure startup on TPM-enabled machinesmachinesRequires read-only fixed media otherwiseRequires read-only fixed media otherwise

Supporting rebinding or hotpatchingSupporting rebinding or hotpatchingThese change the on-disk imageThese change the on-disk imageCI will work if patch includes updated hashCI will work if patch includes updated hash

Online checks at boot-time for revocation Online checks at boot-time for revocation listslists

Revocation list updated after boot and stored Revocation list updated after boot and stored locallylocally

Protect the OSWhen Not Running

The threatsThe threats

Computer is lost or stolenComputer is lost or stolenTheft or compromise of dataTheft or compromise of dataAttack against corporate networkAttack against corporate network

Damage to OS if attacker installs alternate Damage to OS if attacker installs alternate OSOSDifficult and time-consuming to truly erase Difficult and time-consuming to truly erase decommissioned disksdecommissioned disksExisting ways to mitigate these threats are Existing ways to mitigate these threats are too easy for user to circumventtoo easy for user to circumvent

Secure startup (“BitLocker”)Secure startup (“BitLocker”)

Ensure Ensure boot boot

integritintegrityy

Resilient Resilient against against attackattack

Protect system from offline Protect system from offline software-based attackssoftware-based attacks

Lock Lock tampered tampered systemssystems

Prevent boot if monitored Prevent boot if monitored files have been alteredfiles have been altered

Protect Protect data data

when when offlineoffline

Encrypt Encrypt user data user data and system and system filesfiles

All data on the volume is All data on the volume is encrypted: user, system, encrypted: user, system, page, hibernation, temp, page, hibernation, temp, crash dumpcrash dump

Umbrella Umbrella protectionprotection

Third-party apps benefit Third-party apps benefit when installed on encrypted when installed on encrypted volumevolume

Ease Ease equipmequipm

ent ent recyclinrecyclin

gg

Simplify Simplify recyclingrecycling

Render data useless by Render data useless by deleting TPM key storedeleting TPM key store

Speed data Speed data deletiondeletion

Decommissioning takes Decommissioning takes seconds, not hoursseconds, not hours

Won’t EFS protect me?Won’t EFS protect me?

Yes—for those who know what they’re doingYes—for those who know what they’re doingUsers often store data on the desktop—is it Users often store data on the desktop—is it EFSed?EFSed?EFS doesn’t protect the operating systemEFS doesn’t protect the operating systemEFS is very strong against attacksEFS is very strong against attacks

Four levels of key protectionFour levels of key protectionProperly configured, EFS is computationally Properly configured, EFS is computationally infeasible to crackinfeasible to crack

Encryption scenariosEncryption scenariosBitLoBitLockercker

EEFFSS

RRMMSS

LaptopsLaptops Branch office serversBranch office servers Local single user file protection (Windows Local single user file protection (Windows partition only)partition only)

Local multi-user file protectionLocal multi-user file protection Remote file protectionRemote file protection Untrusted administratorUntrusted administrator Remote document policy enforcementRemote document policy enforcement

OS co-existenceOS co-existence

BitLocker encrypts BitLocker encrypts Windows volume onlyWindows volume onlyYou won’t be able to dual-boot another OS You won’t be able to dual-boot another OS on the same volumeon the same volumeOSes on other volumes will work fineOSes on other volumes will work fineData on protected volume is unavailable Data on protected volume is unavailable outside the OSoutside the OSAttempts to modify the protected Windows Attempts to modify the protected Windows volume will render it unbootablevolume will render it unbootable

Enabling BitLockerEnabling BitLocker

Create a 1.5GB active partitionCreate a 1.5GB active partitionThis becomes your “system” partition—where This becomes your “system” partition—where OS bootsOS bootsThe TPM boot manager uses only 50MBThe TPM boot manager uses only 50MBWindows runs from on your “boot” partition—Windows runs from on your “boot” partition—where the system liveswhere the system lives

Initialize TPM chip if you’re using itInitialize TPM chip if you’re using itIn management console or BIOSIn management console or BIOS

Enable BitLocker in Security CenterEnable BitLocker in Security CenterUpdate hard disk MBRUpdate hard disk MBREncrypt Windows “boot” partitionEncrypt Windows “boot” partition

Recovery optionsRecovery options

Useful in case of some kind of hardware Useful in case of some kind of hardware failurefailureIt’s a password; stored in different ways—It’s a password; stored in different ways—

Removable mediaRemovable mediaPrintedPrintedActive DirectoryActive Directory

Also, service packs and driver upgrades Also, service packs and driver upgrades trigger a loader that recomputes and trigger a loader that recomputes and reseals TPM secretsreseals TPM secrets

Can use TPM 1.2 chipCan use TPM 1.2 chip

Microcontroller affixed to motherboardMicrocontroller affixed to motherboardStores keys and digital certificatesStores keys and digital certificatesFor BitLocker, TPM stores storage root keyFor BitLocker, TPM stores storage root key

SRK decrypts volume encryption keySRK decrypts volume encryption key only when only when system boots normally;system boots normally; compares each boot compares each boot process against previously stored measurementsprocess against previously stored measurementsNo user interaction or visibility (unless you No user interaction or visibility (unless you require a PIN or additional start-up key)require a PIN or additional start-up key)Recovery key can be archived in Active Directory Recovery key can be archived in Active Directory for the inevitable “omg” momentfor the inevitable “omg” momentProhibits meaningful use of software debuggers Prohibits meaningful use of software debuggers during bootduring boot

TPM architectureTPM architecture

Reset all registers, transfer execution Reset all registers, transfer execution to Core Root of Trust Measurementto Core Root of Trust MeasurementMeasure next stage of firmware into Measure next stage of firmware into PCR[0] and data into PCR[1]PCR[0] and data into PCR[1]

Hardware test and configurationHardware test and configuration

Code always measured first, then Code always measured first, then executedexecutedNew PCR value is SHA-1 hashed then New PCR value is SHA-1 hashed then concatenated with previous hash; concatenated with previous hash; permanently written to PCRpermanently written to PCROption ROMs and data into PCR[2] Option ROMs and data into PCR[2] and [3]and [3]MBR into PCR[4], partition table in MBR into PCR[4], partition table in PCR[5]PCR[5]

PCR[0]PCR[0]PCR[1]PCR[1]PCR[2]PCR[2]PCR[3]PCR[3]PCR[4]PCR[4]PCR[5]PCR[5]PCR[6]PCR[6]PCR[7]PCR[7]PCR[8]PCR[8]PCR[9]PCR[9]

PCR[10]PCR[10]PCR[11]PCR[11]PCR[12]PCR[12]PCR[13]PCR[13]PCR[14]PCR[14]PCR[15]PCR[15]

Pla

tform

Configura

tion R

egis

ters

Pla

tform

Configura

tion R

egis

ters

TPM architectureTPM architecture

MBR takes over; loads first sector of MBR takes over; loads first sector of active boot partition into memory; active boot partition into memory; measures first 512 bytes into PCR[8]measures first 512 bytes into PCR[8]Boot sector loads; measures Boot sector loads; measures remainder into PCR[9] and transfers remainder into PCR[9] and transfers executionexecutionBoot code measures BOOTMGR into Boot code measures BOOTMGR into PCR[10] and transfers executionPCR[10] and transfers executionAny additional boot applications Any additional boot applications must load only from BitLocker must load only from BitLocker volumevolume

BitLocker keys are in PCR[11]BitLocker keys are in PCR[11]

Finally, BOOTMGR transfers control Finally, BOOTMGR transfers control to operating system; OS checks to operating system; OS checks integrity of all executables loadedintegrity of all executables loaded

PCR[0]PCR[0]PCR[1]PCR[1]PCR[2]PCR[2]PCR[3]PCR[3]PCR[4]PCR[4]PCR[5]PCR[5]PCR[6]PCR[6]PCR[7]PCR[7]PCR[8]PCR[8]PCR[9]PCR[9]

PCR[10]PCR[10]PCR[11]PCR[11]PCR[12]PCR[12]PCR[13]PCR[13]PCR[14]PCR[14]PCR[15]PCR[15]

Pla

tform

Configura

tion R

egis

ters

Pla

tform

Configura

tion R

egis

ters

TPM architectureTPM architecture

TPM measures all code and reports TPM measures all code and reports resultsresults

Default BitLocker consumption: Default BitLocker consumption: 4,8,9,10,114,8,9,10,11

You can add others, with caveatsYou can add others, with caveatsOption ROMs in 2,3Option ROMs in 2,3

Any change invalidates the PCRsAny change invalidates the PCRsIncludes inserting smartcard reader or Includes inserting smartcard reader or USB driveUSB drive

BIOS ROMs in 0,1BIOS ROMs in 0,1Reflashing BIOS invalidates the PCRsReflashing BIOS invalidates the PCRsPCR[0]PCR[0]

PCR[1]PCR[1]PCR[2]PCR[2]PCR[3]PCR[3]PCR[4]PCR[4]PCR[5]PCR[5]PCR[6]PCR[6]PCR[7]PCR[7]PCR[8]PCR[8]PCR[9]PCR[9]

PCR[10]PCR[10]PCR[11]PCR[11]PCR[12]PCR[12]PCR[13]PCR[13]PCR[14]PCR[14]PCR[15]PCR[15]

Pla

tform

Configura

tion R

egis

ters

Pla

tform

Configura

tion R

egis

ters

BitLocker can’t stop everythingBitLocker can’t stop everything

Hardware debuggersHardware debuggersOnline attacks—BitLocker is concerned only Online attacks—BitLocker is concerned only with the system’s startup processwith the system’s startup processPost logon attacksPost logon attacksSabotage by administratorsSabotage by administratorsPoor security maintenancePoor security maintenance

Deployment considerationsDeployment considerations

Requires hardware and software upgradesRequires hardware and software upgradesPhase in, start with high priority computersPhase in, start with high priority computers

Mostly a feature for laptopsMostly a feature for laptopsAlso consider for desktop computers in Also consider for desktop computers in insecure environments (factory floor, kiosk, insecure environments (factory floor, kiosk, …)…)Enterprise key managementEnterprise key management

Protect ServicesFrom Exploit

The threatsThe threats

Remember Blaster?Remember Blaster?Took over RPCSS—made it write msblast.exe to Took over RPCSS—made it write msblast.exe to file system and added run keys to the registryfile system and added run keys to the registry

No software is perfect; someone still might No software is perfect; someone still might find a vulnerability in a servicefind a vulnerability in a serviceMalware often looks to exploit such Malware often looks to exploit such vulnerabilitiesvulnerabilitiesServices are attractiveServices are attractive

Run without user interactionRun without user interactionMany services often have free reign over the Many services often have free reign over the system—too much accesssystem—too much accessMost services can communicate over any portMost services can communicate over any port

Service hardeningService hardening

Service Service refactorefacto

ringring

Move service from LocalSystem to Move service from LocalSystem to something less privilegedsomething less privilegedIf necessary, split service so that only the If necessary, split service so that only the part requiring LocalSystem receives that part requiring LocalSystem receives that

Service Service profilinprofilin

gg

Enables service to restrict its behaviorEnables service to restrict its behaviorResources can have ACLs that allow the Resources can have ACLs that allow the service’s ID to access only what it needsservice’s ID to access only what it needsAlso includes rules for specifying required Also includes rules for specifying required network behaviornetwork behavior

It’s about the principle of least privilege—It’s about the principle of least privilege—it’s good for people, and it’s good for servicesit’s good for people, and it’s good for services

MemoryMemory

RefactoringRefactoring

Ideally, remove the service out of Ideally, remove the service out of LocalSystemLocalSystem

If it doesn’t perform privileged operationsIf it doesn’t perform privileged operationsMake ACL changes to registry keys and driver Make ACL changes to registry keys and driver objectsobjects

Otherwise, split into two piecesOtherwise, split into two piecesThe main serviceThe main serviceThe bits that perform privileged operationsThe bits that perform privileged operationsAuthenticate the call between themAuthenticate the call between themMain serviceMain service

runs as LocalServiceruns as LocalServicePrivilegedPrivilegedLocalSystemLocalSystem

SVCHOST group refactoringSVCHOST group refactoringWindows XP Service Pack 2Windows XP Service Pack 2

LocalSystLocalSystemem

Wireless Wireless ConfigurationConfiguration

System Event System Event NotificationNotification

Network Network ConnectionsConnections

COM+ Event COM+ Event SystemSystem

NLANLA

RasautoRasauto

Shell Hardware Shell Hardware DetectionDetection

ThemesThemes

TelephonyTelephony

Windows AudioWindows Audio

Error ReportingError Reporting

WorkstationWorkstation

ICSICS

BITSBITS

RemoteAccessRemoteAccess

DHCP ClientDHCP Client

W32timeW32time

RasmanRasman

BrowserBrowser

6to46to4

Help and SupportHelp and Support

Task SchedulerTask Scheduler

TrkWksTrkWks

Cryptographic Cryptographic ServicesServices

Removable Removable StorageStorage

WMI Perf AdapterWMI Perf Adapter

Automatic Automatic updatesupdates

WMIWMI

App ManagementApp Management

Secondary LogonSecondary Logon

NetworkNetworkServiceService

DNS ClientDNS Client

Local Local ServiceService

SSDPSSDP

WebClientWebClient

TCP/IP NetBIOS helperTCP/IP NetBIOS helper

Remote RegistryRemote Registry

Windows VistaWindows Vista

LocalSystemLocalSystemNetwork Network restrictedrestricted

Removable Removable StorageStorage

WMI Perf AdapterWMI Perf Adapter

Automatic Automatic updatesupdates

TrkWksTrkWks

WMIWMI

App App ManagementManagement

Secondary Secondary LogonLogon

LocalSystemLocalSystemDemand startedDemand started

BITSBITS

Network Network ServiceService

RestrictedRestricted

DNS ClientDNS Client

ICSICS

RemoteAccessRemoteAccess

DHCP ClientDHCP Client

W32timeW32time

RasmanRasman

NLANLA

BrowserBrowser

6to46to4

Task schedulerTask scheduler

IPSEC ServicesIPSEC Services

ServerServer

Cryptographic Cryptographic ServicesServices

Local ServiceLocal Service

RestrictedRestricted No network No network accessaccess

Wireless Wireless ConfigurationConfiguration

System Event System Event NotificationNotification

Shell Hardware Shell Hardware DetectionDetection

Network Network ConnectionsConnections

RasautoRasauto

ThemesThemes

COM+ Event COM+ Event SystemSystem

Local ServiceLocal ServiceRestrictedRestricted

TelephonyTelephony

Windows AudioWindows Audio

TCP/IP NetBIOS TCP/IP NetBIOS helperhelper

WebClientWebClient

Error ReportingError Reporting

Event LogEvent Log

WorkstationWorkstation

Remote RegistryRemote Registry

SSDPSSDP

ProfilingProfiling

Every service has a unique service identifier Every service has a unique service identifier called a “service SID”called a “service SID”

S-1-80-S-1-80-<SHA-1 hash of logical service name><SHA-1 hash of logical service name>

A “service profile” is a set of ACLs that—A “service profile” is a set of ACLs that—Allow a service to use a resourceAllow a service to use a resourceConstrain the service to the resources it needsConstrain the service to the resources it needsDefine which network ports a service can useDefine which network ports a service can useBlock the service from using other portsBlock the service from using other ports

Now, service can run as LocalService or Now, service can run as LocalService or NetworkService and still receive additional NetworkService and still receive additional access when necessaryaccess when necessary

Restricting servicesRestricting servicesSCM computesSCM computes

service SIDservice SID

SCM adds theSCM adds theSID to serviceSID to service

process’s tokenprocess’s token

SCM creates write-SCM creates write-restricted tokenrestricted token

SCM removes SCM removes unneeded unneeded

privileges from privileges from process tokenprocess token

Service places ACL Service places ACL on resource—only on resource—only

service can write to service can write to itit

Example: event logExample: event log

SysEvent.SysEvent.evtevt

EventloEventlogg

serviceservice

Write-Write-restrictrestrict

ededtokentoken

ACLACLEventlog:WEventlog:W

Restricting services: know thisRestricting services: know this

A restrictable service will set two properties A restrictable service will set two properties (stored in the registry)—(stored in the registry)—

One to indicate that it can be restrictedOne to indicate that it can be restrictedOne to show which privileges it requiresOne to show which privileges it requires

Note!Note! This is a voluntary process. The service This is a voluntary process. The service is choosing to restrict itself. It’s good is choosing to restrict itself. It’s good

development practice because it reduces the development practice because it reduces the likelihood of a service being abused by likelihood of a service being abused by

malware, but it isn’t a full-on system-wide malware, but it isn’t a full-on system-wide restriction mechanism. Third-party services can restriction mechanism. Third-party services can

still run wild and free…still run wild and free…

Network enforcement scenariosNetwork enforcement scenarios

No portsNo ports Services that neither listen nor connectServices that neither listen nor connect

Fixed Fixed portsports

Services that listen or send on known fixed Services that listen or send on known fixed ports should be constrained to those ports ports should be constrained to those ports onlyonly

ConfigurConfigurable able

portsports

Administrator configures port in service’s Administrator configures port in service’s administration UI; network rules and administration UI; network rules and firewall automatically update their own firewall automatically update their own configurationsconfigurations

DynamiDynamic portsc ports

Services that listen or send on dynamically-Services that listen or send on dynamically-allocated portsallocated ports

AuditingAuditing

Management eventsManagement eventsInitial rules configurationInitial rules configurationRule changesRule changesRule deletionsRule deletions

Enforcement eventsEnforcement eventsTraffic allowedTraffic allowedTraffic deniedTraffic denied

global vulnglobal vulnmitigations andmitigations and

system lockdownssystem lockdowns

networknetworkenforcementenforcement

rulesrules

Interaction with host firewallsInteraction with host firewalls

Configuration changes Configuration changes implemented implemented immediatelyimmediatelyRules can’t be disabled Rules can’t be disabled by WF or third-partyby WF or third-partyRules can’t be stopped Rules can’t be stopped while services are while services are runningrunningFor dynamic ports, For dynamic ports, netenf pushes netenf pushes configuration to WFconfiguration to WF

hosthostfirewallfirewallrulesrules

Example rulesExample rulesBlock any network access for BFE"V2.0; Action=Block; App=%windir%\System32\svchost.exe; Svc=bfe;Name=Block any traffic to and from bfe;“

Allow outbound PolicyAgent traffic"V2.0; Action=Allow; Dir=Out; RPort=389; Protocol=tcp; Protocol=udp;App=%windir%\System32\svchost.exe; Svc=PolicyAgent;Name=Allow PolicyAgent tcp/udp LDAP traffic to AD;“

"V2.0; Action=Block; App=%windir%\System32\svchost.exe; Svc=PolicyAgent;Name=Block any other traffic to and from PolicyAgent;“

Allow inbound/outbound traffic to Rpcss"V2.0; Action=Allow; Dir=Out; RPort=135; Protocol=tcp; Protocol=udp;App=%windir%\System32\svchost.exe; Svc=rpcss;Name=Allow outbound rpcss tcp/udp traffic;“

"V2.0; Action=Allow; Dir=in; LPort=135; Protocol=tcp; Protocol=udp;App=%windir%\System32\svchost.exe; Svc=rpcss; Name=Allow inbound tcp/udp rpcss;“

"V2.0; Action=Block; App=%windir%\System32\svchost.exe; Svc=rpcss;Name=Block any other traffic to and from rpcss;"

Protect the OS and Datafrom Unknown Code

The threatsThe threats

A user unknowingly runs code from an A user unknowingly runs code from an unknown source that attempts to modify or unknown source that attempts to modify or delete filesdelete filesCode running as LUA attempts a local Code running as LUA attempts a local elevation of privilege by injecting code into elevation of privilege by injecting code into a process running as administratora process running as administratorTrojans that attempt to execute with full Trojans that attempt to execute with full administrator privilegeadministrator privilegeSystem code reads data from the Internet System code reads data from the Internet (an untrustworthy source) that contains (an untrustworthy source) that contains corrupt data designed to elevate privilege corrupt data designed to elevate privilege by exploiting a bugby exploiting a bug

Mandatory integrity controlMandatory integrity control

Method to prevent low-integrity code from Method to prevent low-integrity code from modifying high-integrity codemodifying high-integrity code

Protect TCB files and data from modification by Protect TCB files and data from modification by privileged usersprivileged usersProtect user data from modification by unknown Protect user data from modification by unknown malicious codemalicious codeProtect processes running as privileged user Protect processes running as privileged user from modification by processes running as from modification by processes running as standard user under the same user SIDstandard user under the same user SID

Classical computer security concept known Classical computer security concept known since the 1970ssince the 1970s

Lots of recent work in various operating systemsLots of recent work in various operating systems

Don’t confuse with code Don’t confuse with code integrityintegrity

CICI Verifies code during module loadingVerifies code during module loading

MIMICC

Implements a type of information flow policyImplements a type of information flow policyImplements an enforcement mechanismImplements an enforcement mechanismIntegrity level changes trigger a security Integrity level changes trigger a security audit eventaudit event

Mandatory integrity control policy is based on Mandatory integrity control policy is based on trustworthinesstrustworthiness. Subjects with . Subjects with lowlow degrees of degrees of trustworthiness can’t change data of a trustworthiness can’t change data of a higherhigher

degrees. Subjects with degrees. Subjects with highhigh degrees of degrees of trustworthiness can’t be forced to rely on data of trustworthiness can’t be forced to rely on data of

lowerlower degrees. degrees.

The limitations of DACLsThe limitations of DACLs

No protection of system stabilityNo protection of system stabilityThird-party installers redistribute system Third-party installers redistribute system binariesbinariesWant to stop this, even if run by administratorWant to stop this, even if run by administrator

No protection from tricky softwareNo protection from tricky softwareNon-savvy users can be convinced to install Non-savvy users can be convinced to install malwaremalwareRuns with full capabilities of userRuns with full capabilities of user

Weakens power of UACWeakens power of UACCan’t distinguish limited version from full Can’t distinguish limited version from full (possibly administrator) version of user(possibly administrator) version of userBoth versions have same user SIDBoth versions have same user SID

Defined integrity levelsDefined integrity levels

SysteSystemm

HighHigh MediumMedium LowLow UntrustedUntrusted

0x4000x40000

0x30000x3000 0x20000x2000 0x10000x1000 00

LocalLocalSysteSystemm

Local Local ServiceService

NetworkNetworkServiceService

ElevatedElevated(full) user (full) user tokenstokens

Standard Standard user tokensuser tokens

AuthenticateAuthenticateddUsersUsers

WorldWorld(Everyon(Everyone)e)

AnonymouAnonymouss

Shell runs hereShell runs here

MIC expressionMIC expression

Add an integrity SID to a user token at Add an integrity SID to a user token at logonlogon

S-1-16-S-1-16-<level><level>Announces the integrity level of the tokenAnnounces the integrity level of the tokenDetermines level of access the token can Determines level of access the token can achieveachievePossible second SID used by Secure Desktop to Possible second SID used by Secure Desktop to determine protection ring of an applicationdetermine protection ring of an application

Store integrity SID in the SACL of every Store integrity SID in the SACL of every object’s security descriptor (user-created object’s security descriptor (user-created and OS)and OS)

Specifies the integrity level of the objectSpecifies the integrity level of the object

Checking MIC levelChecking MIC level

During access check, verify the user passes During access check, verify the user passes integrity check against an object for write integrity check against an object for write accessaccess

However, can add ACE to DACL to deny read However, can add ACE to DACL to deny read access to low integrity users access to low integrity users (more on this later)(more on this later)

User must User must dominatedominate object to obtain write object to obtain write accessaccess

User/process level >= object levelUser/process level >= object levelAll users pass integrity check for reading and All users pass integrity check for reading and executingexecuting

MIC trumps DACLMIC trumps DACLIf the DACL lets you write, but you don’t If the DACL lets you write, but you don’t dominate the object, your write failsdominate the object, your write fails

Consider four scenariosConsider four scenariosAn attachment arrives in mail. While saving, file is An attachment arrives in mail. While saving, file is written with written with lowlow integrity. When executed, it runs at integrity. When executed, it runs at lowlow integrity and can’t write to user’s data. integrity and can’t write to user’s data. MIC MIC prevents process from performing capabilities at prevents process from performing capabilities at user’s level.user’s level.IE downloads file from site in Internet zone. IE IE downloads file from site in Internet zone. IE process that writes file to TIF runs at process that writes file to TIF runs at lowlow integrity; integrity; thus file is receives thus file is receives lowlow integrity. integrity. MIC doesn’t trust MIC doesn’t trust content or code from the Internet.content or code from the Internet.A malicious program is running at A malicious program is running at standardstandard user X user X and attempts to open process running as and attempts to open process running as privilegedprivileged user X for write, to bypass UAC and execute code will user X for write, to bypass UAC and execute code will full privileges. full privileges. MIC stops this because desired access MIC stops this because desired access is write.is write.Admin (IL=Admin (IL=highhigh) runs downloaded program. Process ) runs downloaded program. Process runs as runs as standardstandard admin (IL= admin (IL=mediummedium). ). MIC MIC prevents processes from write-accessing resources prevents processes from write-accessing resources ACLed for the administrator.ACLed for the administrator.

Processes also affectedProcesses also affected

When user launches .EXE, process receives When user launches .EXE, process receives lower of user’s or file’s integrity level (if it lower of user’s or file’s integrity level (if it has one)has one)

Process never runs higher than file, regardless of Process never runs higher than file, regardless of IL of user who started itIL of user who started itProtects even administrators from malicious Protects even administrators from malicious actions of downloaded codeactions of downloaded codeAlso protects any user data, whose level is Also protects any user data, whose level is typically that of the user—it’s higher than the typically that of the user—it’s higher than the codecode

Controlled by AIS (app installer service)Controlled by AIS (app installer service)Check ILs of user and fileCheck ILs of user and fileAdjust process IL accordinglyAdjust process IL accordinglyImpersonate user with correct IL and continue Impersonate user with correct IL and continue creationcreation

Modifying integrity levelsModifying integrity levels

Token can lower its own levelToken can lower its own levelNot reversibleNot reversibleOnly a TCB caller can raiseOnly a TCB caller can raise

Secure InputSecure InputDefault: UI ring SID = object integrity SIDDefault: UI ring SID = object integrity SIDTCB caller can elevate token UI ringTCB caller can elevate token UI ringTypically necessary for accessibility utilities—can Typically necessary for accessibility utilities—can now control UI but not bypass MIC control of now control UI but not bypass MIC control of object accessobject access

But I want to administer my But I want to administer my box!box!

Full privilege tokens, including members of Full privilege tokens, including members of the local Administrators group, are the local Administrators group, are controlled by MICcontrolled by MIC

Can’t delete files if their level is systemCan’t delete files if their level is systemCan’t lower the level of objects or filesCan’t lower the level of objects or files

Built-in “Administrator” account has an Built-in “Administrator” account has an additional privilegeadditional privilege

Grants caller access to objectGrants caller access to objectCould grant to other users, but be careful!Could grant to other users, but be careful!Granting and use of privilege is auditedGranting and use of privilege is audited

Denying read accessDenying read access

Can use deny ACE to prevent lower level Can use deny ACE to prevent lower level principals from reading or executing higher principals from reading or executing higher level objectslevel objectsGood for administrator programsGood for administrator programs

Set IL to highSet IL to highAdd deny ACE for anything with a lower ILAdd deny ACE for anything with a lower ILPrevents malware running at lower level from Prevents malware running at lower level from attempting to call admin toolsattempting to call admin tools

Unlabeled objectsUnlabeled objects

System assumes default MIC of medium System assumes default MIC of medium during access checkduring access checkPrevents untrustworthy code running at low Prevents untrustworthy code running at low from modifying unlabeled objectsfrom modifying unlabeled objects

Regardless of DACLRegardless of DACL

OS files are unlabeledOS files are unlabeledProtected from modification with an ACLProtected from modification with an ACL

Objects without a SID have no MIC Objects without a SID have no MIC considerationconsideration

Non-goalsNon-goals

Provide for confidentiality of dataProvide for confidentiality of dataThis is the Bell-LaPadula modelThis is the Bell-LaPadula modelAlthough with no-read-up ACEs, you can use MIC Although with no-read-up ACEs, you can use MIC to achieve similar behaviorto achieve similar behavior

Prevent high IL processes from reading data Prevent high IL processes from reading data at a lower IL if the policy allows thatat a lower IL if the policy allows thatImplement dynamic integrityImplement dynamic integrityPrevent offline attacks through Prevent offline attacks through modifications of ILs on filesmodifications of ILs on files

But BitLocker could help here…But BitLocker could help here…

Protect the OSfrom the Internet

The threatsThe threats

Alas, most Windows users still run as adminAlas, most Windows users still run as adminMeaning: the Internet runs as admin on your PC!Meaning: the Internet runs as admin on your PC!

““Drive-by” installs of spyware and virus Drive-by” installs of spyware and virus codecodeExploits of vulnerabilities give attackers full Exploits of vulnerabilities give attackers full remote accessremote accessEven non-admins still vulnerable to Even non-admins still vulnerable to malicious destruction of personal datamalicious destruction of personal data

Internet Explorer protected Internet Explorer protected modemode

Built on mandatory integrity controlBuilt on mandatory integrity controlInternet Explorer runs at low integrity levelInternet Explorer runs at low integrity level

Reduce the severity of threats to IE add-onsReduce the severity of threats to IE add-onsEliminate the silent install of malicious code Eliminate the silent install of malicious code through software vulnerabilitiesthrough software vulnerabilitiesPreserve compatibility whenever possiblePreserve compatibility whenever possibleProvide the capability and guidance for add-Provide the capability and guidance for add-ons to restore functionalityons to restore functionalityMinimize required user involvementMinimize required user involvementSometimes called “low-rights IE”Sometimes called “low-rights IE”

Protected mode summaryProtected mode summary

Restricts IE from writing outside of the Restricts IE from writing outside of the Temporary Internet Files (TIF) folderTemporary Internet Files (TIF) folder

IE’s process has lower write privileges than LUAIE’s process has lower write privileges than LUAIt builds on the Mandatory Integrity Control (MIC) It builds on the Mandatory Integrity Control (MIC) which restricts writes to higher integrity folderswhich restricts writes to higher integrity folders

Protected mode uses COM to call two new Protected mode uses COM to call two new broker processes which allow IE to write broker processes which allow IE to write outside of the TIFoutside of the TIFA compatibility layer allows add-ons to A compatibility layer allows add-ons to elevateelevateThis is not a “sandboxing” technology. IE is refactored This is not a “sandboxing” technology. IE is refactored

into a multi-process application, with varying ILs for into a multi-process application, with varying ILs for each process.each process.

Refactoring IERefactoring IE

LP IELP IE

IEUserIEUserIL=high if adminIL=high if adminIL=medium otherwise IL=medium otherwise

LP IELP IEInternet ZoneInternet Zone

IL=lowIL=low

Intranet/Trusted ZoneIntranet/Trusted ZoneIL=mediumIL=mediumSeparate TIFSeparate TIF

IEPolicyIEPolicy IL=highIL=high

Again: the principle of least privilegeAgain: the principle of least privilegeRefactoring at the process level—more Refactoring at the process level—more efficient and less expensive than a virtual efficient and less expensive than a virtual machinemachine

Components and zonesComponents and zones

OperationOperation RequirementsRequirements ProceProcessss

URL navigation and HTML URL navigation and HTML renderingrendering

Least privilegeLeast privilegeLow integrityLow integrity

LP IELP IE

Managing user-controlled Managing user-controlled settingssettings

Least privilegeLeast privilegeMedium Medium integrityintegrity

IEUserIEUser

Enforcing policy in downloaded Enforcing policy in downloaded codecodeInitiating executionInitiating execution

Full privilegeFull privilegeHigh integrityHigh integrity

IEPolicIEPolicyy(service)(service)OperationOperation LP IE LP IE

lowlowLP IE LP IE mediummedium

Files downloaded in zoneFiles downloaded in zone Low ILLow IL Medium Medium ILIL

Modify outside TIFModify outside TIF NoNo YesYes

Interact with other apps on Interact with other apps on desktopdesktop

NoNo YesYes

Inject DLL and create remote Inject DLL and create remote threadthread

NoNo YesYes

Renders HTML files in local Renders HTML files in local zonezone

YesYes YesYes

Installing from the WebInstalling from the Web

LP IELP IE IEPolicyIEPolicy

Run?Run?

greatstuff.comgreatstuff.com

……\TIF\greatstuff.exe\TIF\greatstuff.exe

TrustTrustGreatStuff?GreatStuff?

IL=lowIL=low

……\My Docs\greatstuff.exe\My Docs\greatstuff.exeIL=high if adminIL=high if adminIL=medium otherwise IL=medium otherwise

AISAIS

Run withRun withfull privs?full privs?

greatstuff.exegreatstuff.exe

\Progs\GS\stuff.exe\Progs\GS\stuff.exestuff.dllstuff.dll

IL=highIL=high

full privfull priv

In-proc compatibility layerIn-proc compatibility layer

Redirects file and registry key writes to new Redirects file and registry key writes to new low integrity locations—low integrity locations—

HKCU\Software\Microsoft\Internet Explorer\Low HKCU\Software\Microsoft\Internet Explorer\Low Rights\VirtualRights\VirtualDocuments and Settings\%user profile%\Local Documents and Settings\%user profile%\Local Settings\Temporary Internet Files\VirtualSettings\Temporary Internet Files\Virtual

Added to the location IE is tryingAdded to the location IE is trying

If IE tries to write If IE tries to write here…here…

……it gets redirected hereit gets redirected here

HKCU\Software\FooBarHKCU\Software\FooBar HKCUHKCU\Software\MS\IE\Low Rights\Virtual\Software\\Software\FooBarFooBar

C:\Documents and C:\Documents and Settings\%user profileSettings\%user profile%\FooBar%\FooBar

C:\Documents and Settings\C:\Documents and Settings\%user profile%%user profile%\Local Settings\Temporary Internet Files\Virtual\FooBar\FooBar

Steve RileySteve Rileysteve.riley@microsoft.comsteve.riley@microsoft.com

http://blogs.technet.com/sterileyhttp://blogs.technet.com/steriley

www.protectyourwindowsnetworwww.protectyourwindowsnetwork.comk.com

Thanks very much!Thanks very much!

© 2006 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.

The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation.

MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.