Analyzing Stripped Device-Driver Executables Gogul Balakrishnan 1 Thomas Reps 2 1 NEC Laboratories...

Analyzing Stripped Device-Driver Executables

Gogul Balakrishnan1 Thomas Reps2

1NEC Laboratories America2University of Wisconsin

(Work done at University of Wisconsin)

2

Why Analyze Executables?• Source code is not available

– Windows drivers, libraries, viruses, worms, etc.

• Source code analysis may miss bugs– WYSINWYX phenomenon:

• What You See Is Not What You eXecute

• Better platform for finding security issues– Many exploits utilize particular quirks of a

compiler

3

Device Driver Analysis “. . . You must examine the object code to be sure it matches your

expectations, or at least will work correctly in the

kernel environment. . .”

(From a document on Microsoft’s WHDC website)

4

Device-Driver Analysis• Device Driver

– like a library that exports procedures– each procedure: actions for an I/O request

• e.g., AddDevice routine– invoked by OS when a new device is added

• referred to as “dispatch routines”

• Windows Kernel API is complex– 85% of crashes in Windows due to driver bugs [Swift et al. 2005]

“A driver’s dispatch routine does not return STATUS_PENDING on an I/O Request Packet (IRP) if it has called IoCompleteRequest on the IRP.”

PendedCompletedRequested Rule

(simplified version)

B: return value STATUS_PENDING

A: return value STATUS_PENDING

D: IoCompleteRequest

START COMPLETED

ERROR

*

A

DB

D

START

PENDING

COMPLETED

PENDING COMPLETED

ERROR

A: “return status STATUS_PENDING”

A

A,BA,B

BB: “return status STATUS_PENDING”

*

C

D C

D

C: IoMarkPending

D: IoCompleteRequest

D C,D

C

“A driver’s dispatch routine does not return STATUS_PENDING on an I/O Request Packet (IRP) if it has called IoCompleteRequest on the IRP, unless it has also called IoMarkIrpPending.”

PendedCompletedRequested Rule

7

DDA/x86: Device Driver Analyzer

8

SLAM Error Trace DDA/x86 Error Trace

9

SDV Error Trace DDA/x86 Error Trace

10


11


12

Analyzer

Propertyspecification

OK Errorreport

Source code

Front end

CFG + call graph+ other info

IRConstruction

IRExploratio

n

Static Program-Analysis Tools

• Malicious-code detection• Bug detection• Policy adherence

13

Analyzer


OK Errorreport

Source code

Front end

CFG + call graph+ other info

Model Constructio

n

ModelChecking

Static Program-Analysis Tools

14

Executable

Memory-accessanalyzer

CFG + call graph+ memory-access info

IRRecovery

IRExploratio

n

Static Executable-Analysis Tools

Analyzer


OK Errorreport

15

Executable



ModelExtraction

ModelChecking


Analyzer


OK Errorreport

• Value-Set Analysis [CC04] – Combined pointer and numeric

analysis– Information about memory accesses

• Variable recovery algorithm [VMCAI07]– Structure and Type recovery

• Analyzes heap-allocated data – Recency-abstraction [SAS06]

16

Executable



ModelExtraction

ModelChecking


Analyzer


OK Errorreport

Memory-safety violations!• Access outside of activation record• Access outside of malloc’ed block• Call/jump to data• Use of code as data

17

Memory-Access Analyzerint dispatch_routine(Irp) { int status; status = STATUS_PENDING; if(. . .) { Irp->Status=STATUS_SUCCESS; IoCompleteRequest(Irp); status=STATUS_SUCCESS; } return status;}

proc dispatch_routine sub esp, 4 mov [esp+0], STATUS_PENDING cmp . . . jnz L1 mov ecx, [esp+4] mov [ecx+12], STATUS_SUCCESS push ecx call IoCompleteRequest

mov [esp+0], STATUS_SUCCESS L1: mov eax, [esp+0] add esp, 4 retn

Memory-Access Analyzer (MAA)• Analyze a (possibly stripped) executable E

– Recover an Intermediate Representation (IR)

• Identify the procedures, data objects (V), types, and libraries that it uses

• For each instruction I, compute “AbsEnv”– AbsEnv: (V 2Values)– Values: memory addresses or numeric values– 2Values: use “value-set” abstract domain [VMCAI07]– Distinguish inter-procedural contexts also

18

19

PDEVICE_OBJECT

PDEVICE_OBJECT

PDEVICE_OBJECT

PI8042_QUEUE_PACKET

LONG

PVOID

PI8042_MOUSE_ISRPI8042_ISR_WRITE_POR

TPVOID

CON_DATA.A CON_DATA.B

DEVICE_POWER_STATE

BOOLEAN

BOOLEAN

BOOLEAN

Device Extension Structure for “moufiltr” driver

Declaration in C Source Structure in Executable

20

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4

BYTE_4 BYTE_4

BYTE_4

BYTE

BYTE

BYTE

PDEVICE_OBJECT

PDEVICE_OBJECT

PDEVICE_OBJECT

PI8042_QUEUE_PACKET

LONG

PVOID

PI8042_MOUSE_ISRPI8042_ISR_WRITE_POR

TPVOID

CON_DATA.A CON_DATA.B

DEVICE_POWER_STATE

BOOLEAN

BOOLEAN

BOOLEAN

Device Extension Structure for “moufiltr” driver

Declaration in C Source Structure identified by MAA

21

Memory-Access Analyzer (MAA)• Two aspects of AbsEnv

• Pointer analysis– information about

memory accesses

• Numeric analysis– Information about

numeric contents of data objects

proc dispatch_routine sub esp, 4 mov [esp+0], STATUS_PENDING cmp . . . jnz L1 mov ecx, [esp+4] mov [ecx+12], STATUS_SUCCESS push ecx call IoCompleteRequest

mov [esp+0], STATUS_SUCCESS L1: mov eax, [esp+0] add esp, 4 retn

22

• IR recovery followed by automaton state propagation

Executable



Analyzer


OK Errorreport

API Usage Checking with Recovered IR

23

API Usage Checking with Recovered IRint dispatch_routine(...) { int status; status = STATUS_PENDING; if(...) { IoCompleteRequest(); status = STATUS_SUCCESS; } return status;}

status {STATUS_PENDING, STATUS_SUCCESS}Reachable Automaton States: {START, COMPLETED}

START COMPLETED

ERROR

*

A

DB

D

PendedCompletedRequest rule violated! (False Positive)

From Memory Access Analyzer

24

• Combine IR recovery and state-space exploration– Feedback between phases can improve both

Executable



Analyzer


OK Errorreport


25

Executable

Memory-access andproperty analyzer



OK Errorreport

• Combine IR recovery and state-space exploration?– Feedback between phases can improve both

• ESP-like analysis [M. Das et. al.]• Qualify “AbsEnv” with property automaton states


26


START COMPLETED

ERROR

*

A

DB

D

PendedCompletedRequest rule NOT violated!

START: status {STATUS_PENDING}

COMPLETED: status {STATUS_SUCCESS}

AbsEnv qualified with automaton

state

27


START COMPLETED

ERROR

*

A

DB

D

Actually, above automaton does NOT provide sufficient fidelity to deal with all

cases!

28

API Usage Checking with Recovered IRint dispatch_routine(...) { int status, c; c = 0; status = STATUS_PENDING;

if(...) { status = STATUS_SUCCESS; c = 1; }

if(c == 1) { IoCompleteRequest(); } return status;}

int dispatch_routine(...) { int status; status = STATUS_PENDING; if(...) { IoCompleteRequest(); status = STATUS_SUCCESS; } return status;}

29




START:

status {STATUS_PENDING, STATUS_SUCCESS}

START:

status {STATUS_PENDING}

START COMPLETED

ERROR

*

A

DB

D

30

START COMPLETED

ERROR

*

A

DB

D




START:

status {STATUS_PENDING, STATUS_SUCCESS}COMPLETED:

status {STATUS_PENDING, STATUS_SUCCESS}

PendedCompletedRequest rule violated! (False Positive)

ST_UNKNOWN

ST_PENDING

ST_NOT_PENDING

A: “status : x, where x STATUS_PENDING”

C

B

B: “status : STATUS_PENDING”

A

C: “status : ?”B A

C

C

StatusPending FSM

Finding status-variable: “The local variable (if any) that is used to initialize the value of eax just before returning from the dispatch routine is the status-variable.”

Extracting Counter-Example Traces• Harness existing tracing facilities from

Push Down Systems (PDSs)– Build PDS on-the-fly during property

checking• Symbolic representation of state space

explored– Issue a reachability query on PDS– Report witness trace for a path to the error

configuration

32

Results For “PendedCompletedRequested” Rule

33

34

Summary• Prototype tool to check device-driver executables

– 2 bugs, 10 OK, 5 false positives– Reasonable running time

• Establishes that property checking of stripped executables is a promising direction

• What next?– Automatic abstraction refinement

• Lazy Abstraction [Henzinger et al. POPL02], Property simulation [Das et al. PLDI02], Gulavani & Rajamani [TACAS06],. . .

– Automatic counter-example validation– . . .

Analyzing Stripped Device-Driver Executables

Gogul Balakrishnan1 Thomas Reps2

1NEC Laboratories America2University of Wisconsin

(Work done at University of Wisconsin)

36

Backup Slides

37

G. Balakrishnan and T. Reps, “Analyzing memory accesses in x86 executables”, CC 2004, www.cs.wisc.edu/~reps/#cc04

T. Reps, G. Balakrishnan, J. Lim, and T. Teitelbaum, “A next- generation platform for analyzing executables”, APLAS 2005, www.cs.wisc.edu/~reps/#aplas05.invited

T. Reps, G. Balakrishnan, and J. Lim, “Intermediate-representation recovery from low-level code”, PEPM 2006, www.cs.wisc.edu/~reps/#pepm06.invited

G. Balakrishnan and T. Reps, “Recency-abstraction for heap-allocated storage”, SAS 2006, www.cs.wisc.edu/~reps/#sas06-recency

G. Balakrishnan and T. Reps, “DIVINE: DIscovering Variables IN Executables”, VMCAI 2007, www.cs.wisc.edu/~reps/#vmcai07.invited

38

Current State-of-the-Art: CodeSurfer/x86

• General platform for analyzing executables

• Tracks data movement through memory– including heap

• Does not rely on debugging information• Gives information to build further

analysis– like a compiler front-end plus some more

39

Basic Approach• Recover an Intermediate Representation (IR)

from the executable– IR similar to that built by a compiler

• control-flow graph (w/ indirect jumps resolved)• call graph (w/ indirect calls resolved)• set of variables• values of pointers• used, killed, and possibly-killed variables for CFG nodes• data dependences• types of variables: base types, pointer types, structs, and

classes

• Use the recovered IR for further analysis

Without Debugging Information!

40

Scope• Programs that conform to a “standard

compilation model”– procedures– activation records– global data region– heap, etc.

• Report violations– violations of stack protocol – return address modified within procedure

41

Binary Value-SetAnalysis

Initial estimate of• code vs. data• procedures• call sites• malloc sites

• fleshed-out CFGs• fleshed-out call graph• used, killed, may-killed variables for CFG nodes• points-to sets• reports of violations

CodeSurfer/x86 Architecture

IDAPro Disassembl

er

CodeSurfer(Builds SDG)

Security Analyzers

Decompiler

Binary Rewriter

User Scripts

Memory-Access Analyzer

42

Binary



IDAPro Disassembl

er


Security Analyzers

Decompiler

Binary Rewriter

User Scripts


VSA

ASI


43

Binary



IDAPro Disassembl

er


Security Analyzers

Decompiler

Binary Rewriter

User Scripts


VSA

ASI


44

SLAM Error Trace DDA/x86 Error Trace

45


46


47


Analyzing Stripped Device-Driver Executables Gogul Balakrishnan 1 Thomas Reps 2 1 NEC Laboratories...

Documents

Transcript of Analyzing Stripped Device-Driver Executables Gogul Balakrishnan 1 Thomas Reps 2 1 NEC Laboratories...