lightweight virtualization framework protects critical kernel objects from rootkits
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A lightweight invariance-enforcing framework to mitigate rootkits in virtualized operating systems
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lightweight virtualization framework protects critical kernel objects from rootkits
- 1. hello rootKitty a lightweight invariance-enforcing framework Francesco Gadaleta - Nick Nikiforakis DISTRINET Research Group Katholieke Universiteit Leuven - Belgium
- 2. hello rootKitty a lightweight invariance-enforcing framework Francesco Gadaleta - Nick Nikiforakis DISTRINET Research Group Katholieke Universiteit Leuven - Belgium
- 3. OVERVIEW rootkit Operating System framework critical kernel objects malware detection code virus Analysis integrity invariance attack module virtualization malicious repairing memory corruption approach profiling hardware-based countermeasure evaluation
- 4. ๏ process hiding ๏ botnet ๏ stealing private data ROOTKIT ๏ subverting kernels ๏ spamming ๏ bank fraud
- 5. ROOTKIT User-mode ls, ps, PATH, etc... limited to user’s privileges Kernel-mode device drivers, access to kern. memory, etc... limited to kernel’s privileges (=unlimited)
- 6. FACTof rootkits will never be solved the problem
- 7. FACT
- 8. FACT “I’d rather tackle world peace than the rootkit problem, it is that hard to solve”
- 9. ATTACKER MODEL Loading rootkit as LKM Loading by overwriting memory directly (eg. /dev/mem, /dev/kmem) Executing arbitrary code via kernel vulnerability GOAL: Compromission of hardcoded, static, dynamic kernel objects
- 10. VIRTUALIZATION Events trapped by the hypervisor case EXIT_REASON_MOV_CR case EXIT_REASON_CPUID case EXIT_REASON_IO_INSTRUCTION case EXIT_REASON_RDMSR case EXIT_REASON_WRMSR Guest kernel case EXIT_REASON_EXCEPTION_OR_NMI case EXIT_REASON_EXTERNAL_INT case EXIT_REASON_INTERRUPT_WINDOW case EXIT_REASON_INVLPG case EXIT_REASON_VMCALL: /* for debugging */ case EXIT_REASON_INIT_SIGNAL case EXIT_REASON_STARTUP_IPI case EXIT_REASON_HLT VMExit VMEntry case EXIT_REASON_TASK_SWITCH case EXIT_REASON_XSETBV guest memory space hypervisor memory space Hypervisor
- 11. ASSUMPTION Rootkits modify kernel data structures Observing critical kernel objects is a good detection strategy Virtualization still not massively exploited in desktop environments (QubesOS)
- 12. APPROACH Phase 1: collecting addresses of data structures to protect phy s ad 0xC dr 1 234 0xC 567 size 3214 0xC 567 128 flag 421 s 456 128 111 0xC A 111 521 11 456 111 C 64 111 11 111 4 111 11 guest kernel 111 111 11 trusted module guest memory space hypervisor memory space hypervisor
- 13. APPROACH Phase 2: check integrity within the hypervisor mem. space guest kernel guest memory space hypervisor memory space hypervisor phys addr size hash 0xC1234567 128 abcd 0xC3214567 128 abde 0xC421456A 64 1234 0xC521456C 4 4321
- 14. APPROACH Phase 3: repair compromised objects (if original content provided) guest kernel guest memory space hypervisor memory space hypervisor phys addr size hash 0xC1234567 128 abcd 0xC3214567 128 abde 0xC421456A 64 1234 0xC521456C 4 4321
- 15. IMPLEMENTATION Exploit the MOV_CR event :-| App 1 App 2 App 3 (1) When the guest kernel changes a <mov CR3, cr3_app2> scheduler control register it is doing Guest something “interesting” such as kernel task switching :-) (2) guest memory space hypervisor memory space Room for improvement: we can hypervisor (3) map all the objects to a common host_virt_space area in the hypervisor’s space and phys addr size hash 0xC1234567 128 abcd compute the checksum once 0xC3214567 0xC421456A 128 64 abde 1234 0xC521456C 4 4321
- 16. IMPLEMENTATION Lists of objects to protect might be HUGE => let’s relax the problem phys addr size hash <mov CR3, cr3_app1> <mov CR3, cr3_app2> <mov CR3, cr3_app3> SOLUTION: <mov CR3, cr3_app4> on MOV_CR event the hypervisor checks a subset of objects $$
- 17. EVALUATION BitVisor 1.1 and Linux Kernel 2.6 Total: 15000 kernel objects 128-bit sized Rate: 100 objects/MOV_CR* Corruption of pointers in the guest system call table
- 18. PERFORMANCE LMBENCH (microbenchmarks) Processes open/close sign. handl. fork exec +0.6% +2.5% +41% +35% Local comm. TCP File reread Mmap reread Bcopy Mem.read Mem. write bandwidths +2.2% 0% -0.9% -0.32% -0.12% 0.12%
- 19. PERFORMANCE APACHEBENCH 100K requests, 50 concurrently on local lighttpd server (macrobenchmarks) Time +1.50% Req. per second +1.52% Time per request +1.54% Time per conc. req +1.4% Transfer rate +1.52% DETECTION TIME (time the hypervisor needs to check a compromised object in the worst case) Depends on the guest load, about 6 sec wall-clock time
- 20. LIMITATIONS Protects invariants Attacks to variant data structures are still possible
- 21. DISCUSSION Kernel developers support system Fine-grained protection Lightweight contermeasure Guarantees target-monitor isolation
- 22. DEMO.
- 23. CONCLUSION helloRootkitty mitigates the problem of kernel malware Negligible overhead Attack surface might be considerably reduced Easy integration with other protection mechanisms (Daikon, Gibraltar)
- 24. THANKS.