endpoint security via application sandboxing and virtualization: past, present, future

Endpoint security via Application sandboxing and virtualization:Past, present, future

Rafal Wojtczuk [email protected]

mailto:[email protected]

Bromium Confidential

• We will talk mostly about securing Windows client systems

• Application sandboxes• Sandboxie• Chrome sandbox

• Virtualization-based sandboxes• Qubes OS• Bromium vSentry

Agenda


• Environment designed to run untrusted (or exploitable) code, in a manner that prevents the encapsulated code from damaging the rest of the system

• The aim of a sandbox is to isolate threats• Protection by isolation, not detection

What is a sandbox?


• Infeasible or too expensive to write a bug-free complex code

• Many approaches (AV, HIPS, NIPS) have limited effectiveness• Particularly against 0days

• Containing a malicious code in a jail is doable• How effective?

Why we need sandboxing?


• Type A: OS enhancement based: Sandboxie, Buffer Zone Pro etc.

• Type B: Master/slave model: Adobe ReaderX, Chrome browser

Types of application sandboxes


• Example: Sandboxie (available since 2006), BufferZone Pro

• Custom kernel driver modifies Windows behavior, so that change to protected system components is prevented

• Use cases: Most of such sandboxes are used for controlled execution of applications

• Sandboxie is widely used for malware analysis

TYPE A


Application Sandbox Type A

Architectural Discussion: Type A

• There is a lot of kernel interaction that the sandbox needs to allow for applications to work as designed

• It relies on the assumption that OS kernel is not compromised

• The sandbox cannot protect against malicious kernel mode malware


• Example: Google Chrome (available since 2008), Adobe Reader

• Two processes - master and slave, talking over IPC channel

• Slave is confined using OS access control facilities • Master mediates access to resources• Use case: protect the application from exploitation• Google Chrome and Adobe Reader are popular

applications mainly for web and content rendering

TYPE B


Application Sandbox Type B

Architectural Discussion: Type B

• Master has smaller codebase, the point being – it should be tougher to exploit it

• Slave has a bigger attack surface that needs to be ‘brokered’ by the master

• Slave still directly interacts with the OS Kernel – the attack surface is limited but far from zero (win32k.sys)

App Sandboxes: Important Points

• Application sandboxes are fundamentally vulnerable to kernel mode attacks• The sandbox is entirely bypassed, not penetrated• Layering sandboxes doesn’t help

• The attack surface of commodity OS kernels is large, with no reasonable hope of securing them


• Windows kernel issues are discovered increasingly frequently

• 25 CVE items for Windows kernel in 2012• 30+ CVE items in the first 3 months of 2013• There have been targeted attacks like Duqu that

have targeted kernel vulnerabilities• Cansecwest 2013 Chrome sandbox bypass by MWR

Labs used two stage exploit• First compromise the slave• Then compromise the kernel

• Yes… it’s a big problem!

Is this a problem?

CVE-2012-1515CVE-2012-0178CVE-2012-2527CVE-2012-1890CVE-2011-2016CVE-2011-2018CVE-2011-3402CVE-2012-1864CVE-2012-1865CVE-2012-1866CVE-2012-1867CVE-2012-1868CVE-2012-0217CVE-2012-0179CVE-2012-0157CVE-2012-0148CVE-2012-0149CVE-2011-5046CVE-2012-0154CVE-2012-0001CVE-2013-1278CVE-2013-1279CVE-2013-1280CVE-2013-0008CVE-2012-2556CVE-2012-4786CVE-2012-2530CVE-2012-2553CVE-2012-2897CVE-2013-1248CVE-2013-1249CVE-2013-1250CVE-2013-1251CVE-2013-1252CVE-2013-1253CVE-2013-1254CVE-2013-1255CVE-2013-1256CVE-2013-1257CVE-2013-1258CVE-2013-1259CVE-2013-1260CVE-2013-1261CVE-2013-1262CVE-2013-1263CVE-2013-1264CVE-2013-1265CVE-2013-1266CVE-2013-1267CVE-2013-1268CVE-2013-1269CVE-2013-1270CVE-2013-1271CVE-2013-1272CVE-2013-1273CVE-2013-1274CVE-2013-1275CVE-2013-1276CVE-2013-1277

CVE-2011-3402

Exploit: MS11-087

SANDBOX BASEDDEFENSE “IN-DEPTH”#EPICFAIL

User Mode Exploitation

• Type A and Type B do not restrict network connectivity for a sandboxed process.

• The exception to this rule is Google Chrome that has been hardened to restrict TCP/IP networking in case the renderer got exploited.

• All vulns in these services are a sandbox escape vector

• Even properly functioning code can be abused


• ALPC ports [12] are a low-level mechanism used for interprocess communication on the Windows OS. Again, many Windows services listen on ALPC ports; if a sandboxed code can connect to these services, it can attempt to exploit a vulnerability in it.

• Chrome sandbox documentation correctly states that the sandboxed process cannot obtain new handles to almost all existing interesting objects, including ALPC ports. However, it is not enough – care must be taken to not leak important handles from the pre-sandbox process state into the sandbox.

ALPC Ports


• Wrap the OS in a sandbox such that OS (and other application) vulnerabilities are nonfatal – this can be achieved using a Virtual Machine based environment

What are the alternatives?


• Just do unsafe activities in a standalone VM• Manageability problems

• Ultimately, VM will get dirty• How about using many VMs?

• Managing multiple OS images is painful

First approximation – standalone VM(s)


• Manageability• Performance• Hypervisor and supporting environment is still an

attack vector, arguably small enough to be defensible• Security vs features tradeoff, e.g. GPU virtualization

Virtualization-based sandboxing challenges


Qubes OS (available since 2010)


• Based on a bare-metal hypervisor (Xen)• All user applications run in “AppVMs”, lightweight

VMs based on Linux – one VM per each “role”• Qubes GUI virtualization presents applications like if

they were running locally (aka “seamless” mode)• Networking code sand-boxed in an unprivileged VM

(using IOMMU/VT-d)• Centralized updates of all AppVMs based on the

same template• Disposable VMs

Qubes OS main features


• Requires some discipline/training from the user: • To perform each task in the proper AppVM or disposable VM• To manage files scattered across VMs

• Using off-the-shelf multipurpose large hypervisor• Vulnerable to “sysret” vulnerability, CVE-2012-0217• On the other hand, very careful to introduce as little

supporting privileged code as possible, good• Linux focused, limited support for Windows VMs• Using type 1 hypervisor means deployment issues

Qubes OS deficiencies


Bromium vSentry


• Available since 2012• For Windows, based on type 2 hypervisor (derived from

Xen)• Easily deployable – just install .msi file• Mac OSX version almost ready

• Each instance of application runs in a separate VM• No need for the human to be involved in VM management• Possible due to ultra-optimized VM creation time

• Heavily customized/stripped hypervisor• By design, NOT Vulnerable to “sysret” vulnerability, CVE-2012-0217

• Many enterprise-friendly features• E.g. transparent support for web proxies that require NTLM

authentication

Bromium vSentry main features


• No support for dedicated networking VM• … yet

• In comparison with Qubes, more supporting privileged code• Still managable from security viewpoint• Ultimately, at least partially solvable by using Intel Trusted

Execution technology and deprivileging the host

Bromium vSentry current deficiencies


• Will someday virtualization-based sandboxing become omnipresent (well, at least as Chrome sandbox currently)?

• Some features are unique• E.g. vSentry sandboxes MS Office applications

• The resilience against kernel exploits should be relevant• Any chance for secure Windows kernel soon?• Some mitigations, e.g. SMAP, are interesting, but not a silver bullet

• Functionality concerns• Intel will provide hardware-assisted GPU virtualization some day

• So yes, there is a fair chance• Assuming in real life the number of vulnerabilities will be close to 0

Future


• Most of the above material was prepared in cooperation with Rahul Kashyap ([email protected])

Acknowledgements

mailto:[email protected]

endpoint security via application sandboxing and virtualization: past, present, future

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