This paper proposes HyperSafe, which provides lifetime control flow integrity for the hypervisor through two techniques: 1) non-bypassable memory lockdown of hypervisor code and control data, and 2) restricted pointer indexing to allow only valid control transfers. It implements these techniques in a type-1 hypervisor using LLVM for pointer analysis and enforcement with restricted pointer indexing. This aims to prevent attacks against the hypervisor, such as VM escapes or installation of a hypervisor rootkit.

1. HyperSafe : A Light Apporoach
to Provide Lifetime Hypervisor
Control-Flow Integrity
31st IEEE Symposium on Security and Privacy (2010)
2010-06-21
id:yuzuhara
2010 6 22 1

2. Background
•
• VMM
•
• (VM escape attack)
• hypervisor rootkit(blue pill etc..)
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3. Approach a secure hypervisor
• [seL4, SOSP’09]
•
• Microkernel
•
• TPM&TXT measured launch
•
•
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4. Objective
•
• Control flow integrity
•
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5. cf).Control Flow Integrity [Abadi et.al. , CCS’05]
•
• SFI primitive
• jmp call src/dst
• programming return-oriented
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6. Goal and Assumptions
• Goal
•
•
•
• Threat model
•
• inject, modify, return-to-libc
• out-of-band attacks Malicious DMA
• TPM,TXT
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7. HyperSafe
•
• Type1-VMM
•
•2
• Non-bypassable memory lockdown
• Restricted pointer indexing
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8. lifetime hypervisor
control-flow integrity
load-time run-time
integrity control-flow integrity
e.g. tboot
1.non-bypassable memory lockdown
hypervisor hypervisor
code integrity control-data integrity
2.restricted pointer indexing (RPI)
Fig.1 A break-down of hypervisor integrity guarantees and
corresponding key techniques in HyperSage
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9. 1.Non-Bypassable Memory Lockdown
•
• code
• control data
• control data... RPI Target Table
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10. 1.Non-Bypassable Memory Lockdown (cont’d)
• read-only
• W^X HW
• WPbit OFF
• WPbit ON
Writable page tables
(Traditional)
Read-only page tables
WP WP
Benign Benign OFF ON
Malicious Malicious
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11. 2.Restricted Pointer Indexing (RPI)
• Control flow integrity
• call/ret jmp
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12. 2.Restricted Pointer Indexing (cont’d)
• control data
• call/ret, jmp src/dst
• static analysis CFG(Call Flow Graph)
• CFG Target Table
Call Site i Call Site i Target Table i
eax Callee j eax Callee j
func_j func_j: func_j func_j:
call *%eax | call *%eax |
Ri: ... ... | Ri: ... ... Target Table j |
[esp] | [esp] |
Ri Ri
ret ret
(a) Traditional indirection call (b) New indirection call
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13. 2.Restricted Pointer Indexing (cont’d)
• CFG(control flow graph) Pointer analysis
• LLVM
•
• BitVisor gs
• call/ret control flow RPI
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14. Implementation
• Non-bypassable memory lockdown : VMM
• Restrict Pointer Indexing : LLVM
• LLVM = low level virtual machine
•
• BitVisor 2
• Xen memory lockdown
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15. • WP bit OFF
• <-RPI
• subvert page table
• <-RPI
• Guest
<-memory lockdown
• Return-oriented programming
<- memory lockdown, RPI
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16. Related Work
•
• seL4[Klein et al, SOSP’09],WIT[Akritidis et al, IEEE
S&P’08],KLEE[Cadar et al, OSDI’08]
• OS or
• SIM[Sharif et al, CCS’09] SecVisor[Seshadri,et al, ’07]SBCFI
[Petroni et al,CCS’07]
• Trusted Computing
• TrustVisor[McCune et al, Oakland’10], Flicker[McCune et
al,Eurosys’08],Pioneer[Seshadri et al, SOSP’05]
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17. Summary
• HyperSafe
integrity
Type-1 Hypervisor control flow
lifetime hypervisor
control-flow integrity
load-time run-time
integrity control-flow integrity
e.g. tboot
1.non-bypassable memory lockdown
hypervisor hypervisor
code integrity control-data integrity
2.restricted pointer indexing
2010 6 22 17