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Slashdot Treat

Slashdot Treat. MICROSOFT WINDOWS VISTA HOME 4. USE WITH VIRTUALIZATION TECHNOLOGIES. You may not use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system.

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Slashdot Treat

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  1. Slashdot Treat • MICROSOFT WINDOWS VISTA HOME4. USE WITH VIRTUALIZATION TECHNOLOGIES. You may not use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system. • MICROSOFT WINDOWS VISTA BUSINESS/ULTIMATE6. USE WITH VIRTUALIZATION TECHNOLOGIES. You may use the software installed on the licensed device within a virtual (or otherwise emulated) hardware system on the licensed device. If you do so, you may not play or access content or use applications protected by any Microsoft digital, information or enterprise rights management technology or other Microsoft rights management services or use BitLocker. We advise against playing or accessing content or using applications protected by other digital, information or enterprise rights management technology or other rights management services or using full volume disk drive encryption.

  2. Terra: A Virtual Machine-Based Platform for Trusted Computing Tal Garfinkel, Ben Pfaff, Jim Chow, Mendel Rosenblum, Dan Boneh (Stanford) SOSP’03 Presented by: Michael LeMay

  3. Introduction • VM-based architecture for supporting various security models on a single physical machine • Context: Old paper, not fully implementable at the time and many of the techniques are outdated, but principles have still been very influential

  4. Outline • Background • Security Requirements • Terra Design • Limitations of Terra • Enhanced Technologies • Conclusion

  5. Standard Operating Systems • Large codebases • Difficult to verify correctness and bug-freeness • Offer poor isolation between applications • Compromise in one can affect entire system • Security reduced to level of most vulnerable application • Applications with varying security requirements are unable to share a machine • Don’t provide trusted paths

  6. Closed-Box Platforms • Advantages: • Greater security provided by custom hardware and software, perhaps including tamper-resistance • Embedded cryptographic keys can be used to authenticate platform to remote entity • Disadvantages: • Expensive • Unable to utilize standard software for commodity systems

  7. Example Closed Boxes • Automated Teller Machines • Many cellphones • Game consoles • All three of the above have been cracked! • Advanced meters • These can be easily attacked • Are there any other closed-box platforms you can think of?

  8. What is a closed-box, really? • Something that doesn’t support standard development interfaces by default • Linux: GDB, /dev/kmem, cp, etc. • Open-box • Cellphone: Windows Mobile File Explorer • PS3: ? • Closed boxes

  9. Terra Objectives • Combine best aspects of open- and closed-box platforms: • Strong support for privacy and integrity • Support for standard hardware and software • Provide semantics of dedicated, tamper-evident hardware platform to each application • Doesn’t actually use trusted hardware in implementation! Think about implications…

  10. Realization • Trusted Virtual Machine Monitor (TVMM) • Assurances: • Isolates VMs • Will not falsely attest VM state • Will not disclose or allow tampering with contents of closed-box VM • These assurances are root-secure • Limitations: • Unable to guarantee availability • Relies on Management VM to provide additional functionality

  11. Terra Architecture

  12. Trusted Platform Module

  13. TPM Interconnection

  14. TPM 1.0 Components TCG 1.0 Architecture Overview

  15. Credential Types • TPM contains 5 types of credentials: • Important: • Endorsement or EK credential: uniquely identifies TPM, privacy concern • Identity or AIK credential: Issued by privacy CA to preserve privacy of EK credential • Not-so-important: • Conformance credential: Certifies that TPM meets specifications • Platform credential: Identifies TPM manufacturer and capabilities • Validation credential: Associated with peripheral or software to guarantee integrity

  16. Threat Model • Threat model dictated by hardware capabilities: • Tamper-evident, not tamper-resistant TPM • Sets bit internally when compromised, but doesn’t zero information • Hardware-protected CPU and memory against adversaries lacking electrical analysis equipment and expertise • Joe pointed out that this assumption was violated on the Xbox • Unprotected disk • Can be removed and inserted into new machine

  17. Remote Attestation • Three phases: • Measurement: machine to be attested must measure its properties locally • Attestation: transfer measurements from machine being attested to remote machine • Verification: remote machine examines measurements transferred during attestation and decides whether they are valid and acceptable

  18. Linux Integrity Measurement

  19. Linux Attestation

  20. Linux Verification

  21. Terra Attestation Process • Lower layers certify higher layers: • TPM → Firmware → Boot Loader → TVMM → VM → Application • For each layer above TPM: • Upper layer generates public/private keypair • Upper layer requests that lower layer certify its public key and perhaps other data • Lower layer signs certificate with hash over attestable parts of requests as the common name (main identifier) and the hashed data as auxiliary information

  22. TVMM Attestation (cont.) • VM disk contents included in attestation • Simple hash tree used to optimize performance • Permits VM to run for indefinite time using false disk hash • Encrypted, integrity-protected, and non-encrypted disks all supported • Keys used to protect disks placed in sealed storage, to prevent attackers from removing disks and performing an offline compromise

  23. Attestation Verification • Verify certificate in each layer by ensuring that it is signed by lower layer • TPM certificate is signed by TPM manufacturer, which is also responsible for issuing CRLs • No TPM manufacturer currently does this • Check software hashes and attested data contained within certificates, ensure they are all trusted.

  24. Attestation Binding • Verification must be bound to attested process in some way • Exchange certificate chains during SSL handshake • If software is good, it will not persist session key • Prevents system from rebooting and continuing execution in unattested state • This problem was pointed out by John

  25. Attestation Limitations • In Terra, PCRs are not necessarily utilized, so no boot history is maintained • Verifying entity must have comprehensive and up-to-date list of trusted software configurations • A simple patch or software upgrade generates entirely new hash • Difficult to obtain meaningful security assurances from simple software hashes

  26. Policy-Reduced Integrity Measurement Architecture JaegerSS 2006

  27. Attestation Limitations (cont.) • Compromising a TPM key undermines entire process • TPM vendors do not maintain CAs or CRLs • Platform privacy compromised by attestation • Endorsement Key uniquely identifies platform • Privacy CAs issue alternative keys (AIKs), but have an unsustainable business model • Terra proposes group signatures

  28. Attestation Limitations (cont.) • Attestation can increase vendor lock-in and platform discrimination by permitting verifying entities to check the exact, complete software stack of the system. • Attestation can only guarantee past and present system properties, it can say very little about the future. • Owner can always turn machine off • Operator can often load new software that violates trust (can be prevented)

  29. Attestation Limitations (cont.) • John pointed out that TPM revocation is an issue. Fortunately, TPMs are unlikely to be compromised while the system is running. • Must decide how much state to attest. Should updating the high scores in Trusted Quake break the attestation? • Use separate images for configuration data

  30. Attestation Limitations (cont.) • Can’t directly detect MITM exploits • Attestation simply tells you what software is running on system, not the identity of the system • Could corrupt DNS or routing tables and run legitimate server, client wouldn’t be able to detect. • Is this a bad thing? • No, leads to privacy problems.

  31. Attestation Limitations (cont.) • Useful for clients attempting to verify security of servers? • No, clients couldn’t possibly be provided with source code for major websites, so attestation would be meaningless. • Is isolation important from the standpoint of attestation? • Somewhat orthogonal, but often an important property being attested.

  32. Management VM • Analogous to Xen Dom0 • Performs administrative functions: • Create virtual device (NIC, block dev, etc.) • Creates new VM • Attach/detach virtual device to/from VM • Powers VM up or down • Suspends and resumes VM • Hosts drivers

  33. Driver Security • Terra designers do not wish to include drivers in TCB, since they are often buggy • They suggest nooks, but the VM-based driver isolation technique we discussed would also be applicable • Just one of the problems with the suggested Terra architecture

  34. Security-Enhanced Xen • Would provide significant benefits to Terra • Mandatory Access Control (MAC) for VM objects and commands • Would permit controlled data sharing between Terra VMs, using shared memory buffers • Currently implemented by IBM as sHype • Xen Security Modules (XSM) provides extended hooks, backwards compatibility with sHype, and support for SELinux-style Type Enforcement policies

  35. Security-Enhanced Xen (cont.) • Better TPM support: • Trusted/secure boot • TPM virtualization • Dom0 decomposition • Break management interface into pieces, allow different domains to use various parts • Run drivers in separate domains • Secure I/O • IO-MMU support http://www.xensource.com/files/xs0106_intel_xen_security.pdf, http://www.xensource.com/files/XenSecurity_SHand.pdf

  36. TPM Virtualization http://www.xensource.com/files/XenSecurity_Intel_CRozas.pdf

  37. Intel LaGrande

  38. Intel Trusted Execution Technology (TET) http://www.intel.com/technology/security/downloads/arch-overview.pdf

  39. TET System Architecture

  40. TET System Implementation • Enter VMM mode using GETSEC[SENTER] instruction, measures VMM before transferring control • CPU provides internal RAM that can execute code after hashing code and verifying against embedded digital signature. Enter Authenticated Code (AC) mode using GETSEC[ENTERACCS] instruction. • Will only run software signed by Intel • Is this a good thing? What if Intel decides they don’t like ATI, so you have to choose between an ATI graphics card and an Intel processor? http://download.intel.com/technology/security/downloads/31516803.pdf

  41. ARM TrustZone http://www.arm.com/products/esd/trustzone_home.html

  42. Microsoft NGSCB • Microsoft, AMD, HP, IBM, Infineon, Intel, Sun, … all members of TCG • Uses TPM to partitionsystem into two parts:Nexus and L.H.S. • NCAs: Nexus Comput-ing Agents • Only two compartments

  43. NGSCB Architecture – WinHEC 2004 • Little device diversity • Only a few drivers • KLOC • Great device diversity • Thousands of drivers • MLOC • Compartments are Windows-based • Significantly reduced footprint • Strongly Isolated, hardened and armored • Secure device ownership • Nexus or service compartments • Windows • Owns most HW • Only real-time OS • Security benefits via scenarios Biddle, 2004

  44. Additional Questions • What are some closed-box platforms that could not be easily adapted to run within Terra? • What are some closed-box platforms that could benefit from Terra? • What changes to Terra or its infrastructure are necessary to shrink the first list and/or expand the second?

  45. Additional Questions (cont.) • Are Terra-provided closed-box platforms more secure than standard closed-box platforms? • Use tamper-evident hardware for key storage • Would your answer change if the TPM were integrated into the CPU so it can’t be snooped?

  46. Conclusion • Very influential general architecture • Proposed before much needed functionality was available, but could be easily updated to use new functionality • More general than NGSCB, but should benefit from NGSCB-inspired hardware

  47. Appendices

  48. Attested Meter • Distributed Energy Resource management • Demand Reducation/Load Management • Automated Meter Reading/Real Time Pricing

  49. Problem • For real-time pricing to work, power company has to know exactly how much power was used by each customer at each point in time • Could be privacy problem • User should be able to access consumer portal software on meter from local network • We’re taking a closed-box platform, a meter, and adding an isolated open-box application • Same thing suggested by Ravinder for Xbox

  50. Attested Meter Architecture

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