BATTLE OF SKM AND IUM

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IS IUM/VSM SECURE…? YES! • There do not appear to be any design flaws in the implementation of IUM/VSM • Good decisions made all around regarding separation of privileges, roles, and powers • Good analogy was made yesterday in the Microsoft presentation with government judicial, executive, and legislative branches • Extremely limited attack surface • Hypervisor is already a very thin piece of code. VTL has added complexity, but is manageable • No true hypervisor non-DoS bugs have ever been found (only virtualization component vulnerabilities) • SKM is ~350KB and provides limited system calls and accessible interfaces from VTL 0 • SKCI does do ASN.1 parsing, but code has been tested for decades and is a minimalistic implementation • However, true VSM security relies on platform features to be present, and well-implemented
SECURE KERNEL COMPLEXITY / ATTACK SURFACE • Note that outside of the Secure Mode Calls described, the Secure Kernel does not do much on its own • All scheduling, memory management (paging/etc) and other resource management is done by NTOS • No hardware drivers / devices implemented • System calls are “proxied” through Normal Mode Calls • SKM doesn’t “trust” NTOS, but it does depend on it • So Denial-of-Service attacks are possible, but information disclosure would require a pretty severe vulnerability • You also cannot “nop out” calls to SKM in order to attack the system • For example, since SKM owns the EPT mappings and secure image relocations, if you try to force the system to load an unsigned driver (bypassing Device Guard), the code will simply not execute, since the EPTs will not have the executable bit set • If you force loading an unsigned Trustlet, default settings will allow it to run (since it’s user-mode code), but it won’t actually have access to any SKM facilities (SKM will not have a secure image object associated with it)
Page 1 and 2:
BATTLE OF SKM AND IUM HOW WINDOWS 1
Page 3 and 4:
PRESENTATION OVERVIEW • Microsoft
Page 5 and 6:
VBS FEATURES IN WINDOWS 10 / SERVER
Page 7 and 8:
ENABLING VBS
Page 9 and 10: HOW DOES IT ALL WORK? • Hyperviso
Page 11 and 12: SEPARATION OF ROLES • Instead of
Page 13 and 14: PLATFORM REQUIREMENTS • The Boot
Page 15 and 16: HARD CODE GUARANTEES • When hard
Page 17 and 18: VIRTUAL SECURE MODE (VSM) BOOTSTRAP
Page 19 and 20: SKM LAUNCH • To initialize VTL 1,
Page 21 and 22: BCD VSM POLICY OPTIONS • The poli
Page 23 and 24: SKM INTERNALS
Page 25 and 26: SKM STRUCTURES • SKM has a PCR at
Page 27 and 28: SKM CAPABILITIES • The SkCapabili
Page 29 and 30: SECURE MODE CALLS • Secure Mode C
Page 31 and 32: SPECIALIZED SECURE MORE SERVICE CAL
Page 33 and 34: NORMAL MODE SERVICE CALLS • SK ne
Page 35 and 36: IUM INTERNALS
Page 37 and 38: SECURE SYSTEM CALLS • SKM exposes
Page 39 and 40: SECURE BASE API • Trustlets shoul
Page 41 and 42: NOTABLY MISSING… • Trustlets ca
Page 43 and 44: NORMAL MODE SYSTEM CALL PROXYING Th
Page 45 and 46: LAUNCHING A TRUSTLET • Process At
Page 47 and 48: EXAMPLE IUM-COMPLIANT SIGNED BINARY
Page 49 and 50: TRUSTLET INSTANCE GUID • Trustlet
Page 51 and 52: LSA TRUSTLET • One of the two inb
Page 53 and 54: LOADING A TRUSTLET • Ldr, or the
Page 55 and 56: TRUSTLET TO NORMAL WORLD COMMUNICAT
Page 57 and 58: CAN WE BUILD OUR OWN TRUSTLETS? •
Page 59: CONCLUSION RISKS AND THOUGHTS
Page 63 and 64: VSM WITHOUT SECUREBOOT • What’s
Page 65: YOU HAVE QUESTIONS? I HOPEFULLY HAV
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BATTLE OF SKM AND IUM

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