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  • 1. Endpoint security via Application sandboxing and virtualization: Past, present, future Rafal Wojtczuk rafal@bromium.com
  • 2. Agenda We will talk mostly about securing Windows client systems Application sandboxes Sandboxie Chrome sandbox Virtualization-based sandboxes Qubes OS Bromium vSentry Bromium Confidential
  • 3. What is a sandbox? 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 Bromium Confidential
  • 4. Why we need sandboxing? 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? Bromium Confidential
  • 5. Types of application sandboxes Type A: OS enhancement based: Sandboxie, Buffer Zone Pro etc. Type B: Master/slave model: Adobe ReaderX, Chrome browser Bromium Confidential
  • 6. TYPE A 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 Bromium Confidential
  • 7. Application Sandbox Type A Bromium Confidential
  • 8. 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
  • 9. TYPE B 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 Bromium Confidential
  • 10. Application Sandbox Type B Bromium Confidential
  • 11. 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)
  • 12. App Sandboxes: Important Points Application sandboxes are fundamentally vulnerable to kernel mode attacks The sandbox is entirely bypassed, not penetrated Layering sandboxes doesnt help The attack surface of commodity OS kernels is large, with no reasonable hope of securing them
  • 13. Is this a problem? 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 its a big problem! Bromium Confidential
  • 14. CVE-2011-3402 Exploit: MS11-087 SANDBOX BASED DEFENSE IN-DEPTH #EPICFAIL
  • 15. 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
  • 16. ALPC Ports 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. Bromium Confidential
  • 17. What are the alternatives? 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 Bromium Confidential
  • 18. First approximation standalone VM(s) 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 Bromium Confidential
  • 19. Virtualization-based sandboxing challenges 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 Bromium Confidential
  • 20. Qubes OS (available since 2010) Bromium Confidential
  • 21. Qubes OS main features 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 Bromium Confidential
  • 22. Qubes OS deficiencies 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 Bromium Confidential
  • 23. Bromium vSentry Bromium Confidential
  • 24. Bromium vSentry main features 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 Confidential
  • 25. Bromium vSentry current deficiencies 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 Confidential
  • 26. Future 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 Bromium Confidential
  • 27. Acknowledgements Most of the above material was prepared in cooperation with Rahul Kashyap (rahul@bromium.com) Bromium Confidential