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Spectre: A Dependable Introspec3on Framework via System Management Mode Fengwei Zhang, Kevin Leach, Kun Sun, and Angelos Stavrou. In DSN'13. Presented by Fengwei Zhang Wayne State University CSC 6991 Topics in Computer Security 1 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 2 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 3 Introduc3on • Malware detec3on and analysis remain an open research problem • Tradi3onally, malware detec3on is provided by ︎ installing an3-malware tools (e.g., an3-virus) within the OS • However, these detec3on tools are vulnerable to ︎ malware running at the same level (e.g., rootkits) • ’Out-of-box’ introspec3on mechanism proposed ︎ for malware detec3on and analysis (e.g., Virtual machine introspec3on) Wayne State University CSC 6991 Topics in Computer Security 4 Introduc3on • Virtual Machine Intropsec3on (VMI) systems run malware within a VM and use analysis tool to introspect the malware from outside • VMI systems have been widely adopted for malware detec3on and ︎ analysis. They isolate the malware detec3on so]ware from a vulnerable guest [4, 5, 6] • Limitaons of VMI systems: – Large Trusted Compu3ng Base (TCB) (e.g., Xen 4.2 has 208K lines of code) – Armored malware can detect the presence of a VM and alter its own execu3on (e.g., an3-VM techniques) – High performance overhead • We present Spectre, a dependable introspec3on framework via system management mode Wayne State University CSC 6991 Topics in Computer Security 5 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 6 Background System Management Mode (SMM) • A CPU mode on the x86 Architecture. • A]er entering into SMM, it executes the System Management Interrupt (SMI) handler • SMI handler stores at a sealed storage called System Management RAM (SMRAM) • BIOS locks the SMRAM, and the SMRAM is inaccessible from any other CPU modes • SMM-based systems – Integrity checking: HyperGuard [7], HyperCheck [8], – HyperSentry [1] – SMM rootkits [3, 2] – Agacks against SMM [9] Wayne State University CSC 6991 Topics in Computer Security 7 Background Basic Input and Output System (BIOS) and Coreboot • BIOS code is stored on-volale ROM, and it is responsible for hardware ini3alizaon before OS starts. • Coreboot is an open source project aimed to replace the BIOS in current computer • Spectre uses a custom SMI handler in Coreboot Wayne State University CSC 6991 Topics in Computer Security 8 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 9 System Framework Target Machine SPECTRE system regularly introspects native memory on target machine Monitor Machine Check kernel data Rebuild Check kernel code Enter Report alerts SMM semantic data Check program data ‘heartbeat’ attack occured? optional custom module ... select module Wayne State University CSC 6991 Topics in Computer Security 10 System Framework • Step 1: Periodic triggering of SMM Target Machine SPECTRE system regularly introspects native memory on target machine Monitor Machine Enter SMM Wayne State University CSC 6991 Topics in Computer Security 11 System Framework • Step 1: Periodic triggering of SMM • Step 2: Rebuilding seman3c informaon Target Machine SPECTRE system regularly introspects native memory on target machine Monitor Machine Enter Rebuild SMM semantic data Wayne State University CSC 6991 Topics in Computer Security 12 System Framework • Step 1: Periodic triggering of SMM • Step 2: Rebuilding seman3c informaon • Step 3: Running a detec3on module Target Machine SPECTRE system regularly introspects native memory on target machine Monitor Machine Check kernel data Enter Rebuild Check kernel code SMM semantic data Check program data optional custom module ... select module Wayne State University CSC 6991 Topics in Computer Security 13 System Framework • Step 1: Periodic triggering of SMM • Step 2: Rebuilding seman3c informaon • Step 3: Running a detec3on module • Step 4: Communicaon with monitor server Target Machine SPECTRE system regularly introspects native memory on target machine Monitor Machine Check kernel data Rebuild Check kernel code Enter Report alerts SMM semantic data Check program data ‘heartbeat’ attack occured? optional custom module ... select module Wayne State University CSC 6991 Topics in Computer Security 14 Step 1: Periodic Triggering of SMM • Two ways to trigger an SMI – So]ware-based: write to an ACPI port specified by chipsets – Hardware-based: NIC card, keyboard, mouse, and hardware 3mer • Hardware-based method is more reliable than so]ware-based method, so we use a hardware 3mer at southbridge to periodically assert an SMI Wayne State University CSC 6991 Topics in Computer Security 15 Step 2: Rebuilding Seman3c Informaon • SMM only sees the raw memory, and does not know the seman3cs of the memory (e.g. OS data structures) • Similar to the seman3c gap problem in VMI systems • We manually bridge the seman3c gap in our prototype, automacally bridging (e.g., Virtuoso [6], VMST [4]) PsActiveProcessHead Executive Process Heap List Segment Static VA of KPCR Segment S0 prev Heap H0 +78h Metadata... 0xffdff000 Heap H1 KPCR KdVersionBlock FirstEntry +34h next Heap H2 LastEntry PEB Heap H3 Entry E1 Executive Process Executive Process Executive Process Heap H4 e.g., “lsass.exe” e.g., “explorer.exe” e.g., “System” ... Data... Heap Hn Other Entry E2 prev prev prev Executive next next next Data... Processes Heap H0 Metadata Entry E3 ... Segment S0 Entry ... Heap List Segment S1 Segment S Data... Other heap 2 ... ... Handle Table 3 Handle Table 2 Handle Table 1 Entry En tables Segment Sn Process Environment Block Heap Wayne State University CSC 6991 Topics in Computer Security 16 Seman3c Gap Problem in VMI • SoK: Introspec3ons on Trust and the Seman3c Gap. Bhushan Jain, Mirza Basim Baig, Dongli Zhang, Donald E. Porter, and Radu Sion. In S&P'14. • SMM-based Systems, TrustZone-based Systems, SGX, other hardware isolated execu3on environments (HIEEs) Wayne State University CSC 6991 Topics in Computer Security 17 Step 3: Running a Detec3on Module • We demonstrate the capability of our framework with three memory-based aacks: – Detec3ng heap spray aacks – Detec3ng heap overflow aacks – Detec3ng rootkits • Other checking modules can be extended into Spectre with corresponding detec3on algorithm Wayne State University CSC 6991 Topics in Computer Security 18 Step 4: Communicaon with Monitor Machine • The SMI handler alerts the monitor machine over a serial or Ethernet cable • We port the NIC driver into SMI handler because we do want to trust any code in the OS • ‘Heartbeat’ message can be used to detect denial of service aack • Exit from SMM and resume OS states Wayne State University CSC 6991 Topics in Computer Security 19 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 20 Prototype Specificaon • Hardware ︎ – Motherboard: ASUS-M2V MX SE – CPU: 2.2GHz AMD Sempron LE-1250 – RAM: 2GB Kingston DDR2 – NICs: Integrated NIC and Intel e1000 Gigabit with PCI • So]ware ︎ – BIOS: Coreboot+SeaBIOS – OSes: Linux (Cent OS 5.5) and Windows XP SP3 Wayne State University CSC 6991 Topics in Computer Security 21 Memory Agacks Detec3on • Run various memory aacks, and measure the detec3on 3me in the SMM • Detec3on 3me = Time at SMM exit - Time at SMM enter Wayne State University CSC 6991 Topics in Computer Security 22 System Overhead • Spectre is OS-agnos3c, and can detect memory aacks on both Windows and Linux plaorms. • Benchmark: PassMark on Windows and UnixBench on Linux • First, we run different detec3on modules, and record their benchmark scores – Without detec3on module – Heap spray detec3on module – Heap Overflow detec3on module – Rootkits detec3on module • Second, we change the SMI triggering rate, and it ranges from 1/16 s to 5s Wayne State University CSC 6991 Topics in Computer Security 23 System Overhead • X-coordinate: Sampling interval ︎ • Y-coordinate: Percent overhead Windows Linux Without detection module 20% Without detection module Heap spray module Heap spray detection module 20% Heap overflow module 15% Rootkit detection module Rootkit module 10% 10% Percent overhead Percent overhead 5% 0% 0% 5s 2s 1s 1 s 1 s 5s 2s 1s 1 1 2 16 2 s 16 s Sampling interval / s Sampling interval / s Wayne State University CSC 6991 Topics in Computer Security 24 Comparison with VMI Systems • Smaller code base–Spectre only trust the BIOS, but VMI systems need to trust hypervisor • More transparent–armored malware with an3-VM techniques cannot detect it • Beger Performance Wayne State University CSC 6991 Topics in Computer Security 25 Agenda • Introduc3on • Background • System Framework • Experimental Results • Conclusion Wayne State University CSC 6991 Topics in Computer Security 26 Conclusion • We introduce a hardware-assisted framework ︎ that can examine code across all layers of a running system • Spectre is OS-agnos3c and fully transparent to higher level so]ware • We have implemented a prototype of our framework in both Linux and Windows, and demonstrates that our system can detect various memory aacks including heap spray, heap overflow and rootkits. Wayne State University CSC 6991 Topics in Computer Security 27 References Wayne State University CSC 6991 Topics in Computer Security 28 .
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