The DynamoRIODynamic Tool Platform

Derek Bruening

Typical Modern Application: IIS

2

Runtime Interposition Layer

3

underlying platform (stock OS,

commodity hardware)

DynamoRIO:

manipulate every instruction in

running application

running application

Outline

System Overview

Example Tools

• Security

• Debugging

Open Source Project

4

Direct Code Modification

5

Kernel32!TerminateProcess:

7d4d1028 7c 05 jl 7d4d102f

7d4d102a 33 c0 xor %eax,%eax

7d4d102c 40 inc %eax

7d4d102d eb 08 jmp 7d4d1037

7d4d102f 50 push %eax

7d4d1030 e8 ed 7c 00 00 call 7d4d8d22

e9 37 6f 48 92 jmp <callout>

Entry Point Complications

6

Kernel32!TerminateProcess:

7d4d1028 7c 05 jl 7d4d102f

7d4d102a 33 c0 xor %eax,%eax

7d4d102c 40 inc %eax

7d4d102d eb 08 jmp 7d4d1037

7d4d102f 50 push %eax

7d4d1030 e8 ed 7c 00 00 call 7d4d8d22

e9 37 6f 48 92 jmp <callout>

application code

bar()foo()

Basic Interpreter

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A

B C

D

E

F

interpreter

Slowdown: ~300x

fetch decode execute

application code

bar()foo()

Improvement #1: Basic Block Cache

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A

B C

D

E

F

DynamoRIO

software

code

cache

A

C

D

E

F

Slowdown: 300x 25x

application code

bar()foo()

Improvement # 2: Linking Direct Branches

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A

B C

D

E

F

DynamoRIO

software

code

cache

A

C

D

E

F

Slowdown: 300x 25x 3x

application code

bar()foo()

Improvement # 3: Linking Indirect Branches

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A

B C

D

E

F

DynamoRIO

software

code

cache

A

C

D

E

F

Slowdown: 300x 25x 3x 1.2x

indirect

branch

lookup

application code

bar()foo()

Improvement # 4: Building Traces

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A

B C

D

E

F

DynamoRIO

software

code

cache

A

C

D

E

F

indirect

branch

lookup

Slowdown: 300x 26x 3x 1.2x 1.1x

cmp

application code

bar()foo()

Tool Platform

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A

B C

D

E

F

DynamoRIO

software

code

cache

C

X

D

F

indirect

branch

lookup

cmp

tool codeA

E

Transparency

Do not want to interfere with the semantics of the program

Dangerous to make any assumptions about:

• Register usage

• Calling conventions

• Stack layout

• Memory/heap usage

• I/O and other system call use

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Painful, But Necessary

Difficult and costly to handle corner cases

Many applications will not notice…

…but some will!

• Microsoft Office: Visual Basic generated code, stack convention

violations

• COM, Star Office, MMC: trampolines

• Adobe Premiere: self-modifying code

• VirtualDub: UPX-packed executable

• etc.

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Avoid Resource Conflicts

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Linux Windows

DynamoRIO Demo

Inserts counters into every basic block

Counters are visible via shared memory

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Outline

System Overview

Example Tools

• Security

• Debugging

Open Source Project

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Anatomy of an Attack

system and

application memory

kernel

network

ENTER

CORRUPT DATA

HIJACK PROGRAM COUNTER

COMPROMISE

Critical Data: Control Flow Indirection

Subroutine calls

• Return address and activation records on visible stack

Dynamic library linking

• Function exports and imports

Object oriented polymorphism: dynamic dispatch

• Vtables

Callbacks – registered function pointers

• Event dispatch, atexit

Exception handling

Any problem in computer science can be solved with another layer

of indirection.

- David Wheeler

Critical Data: Control Flow Exploits

Return address overwrite

• Classic buffer overflow

GOT overwrite

Object pointer overwrite or uninitialized use

Function pointer overwrite

• Heap, stack, data, PEB

Exception handler overwrites

• SEH exploits

Any problem in computer science can be solved with another layer

of indirection. But that usually will create another problem.

- David Wheeler

Preventing Data Corruption Is Difficult

Stored program addresses legitimately manipulated by

many different entities

• Dynamic linker, language runtime

Intermingled with regular data

• Return addresses on stack

• Vtables in heap

Even if could distinguish a good write from a bad write, too

expensive to monitor all data writes

Insight: Hijack Violates Execution Model

HardwareInterface

Typical Application

Execution ModelSecurity Attack

Goal: Shrink Hardware Interface

Typical Application

Execution ModelSecurity Attack

Constrained Hardware Interface

Program Shepherding

Monitor all control-flow transfers during program execution

• DynamoRIO is in perfect position to do this

Validate that each transfer satisfies security policy based

on execution model

• Application Binary Interface (ABI): calling convention, library

invocation

The application may be damaged by data corruption, but

the system will not be compromised by hijacking control

flow

Outline

System Overview

Example Tools

• Security

• Debugging

Open Source Project

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Memory Bugs

Memory bugs are challenging to detect and fix

• Memory corruption, reading uninitialized memory, memory leaks

Observable symptoms resulting from memory bugs are

often delayed and non-deterministic

• Errors are difficult to discover during regular testing

• Testing usually relies on randomly happening to hit visible symptoms

• The sources of these bugs are painful and time-consuming to track

down from observed crashes

Memory bugs often remain in shipped products and can

show up in customer usage

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Dr. Memory

Detects unaddressable memory

accesses

• Wild access to invalid address

• Use-after-free

• Buffer and array overflow and underflow

• Read beyond top of stack

• Invalid free, double free

Detects uninitialized memory reads

Detects memory leaks

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Implementation Strategy

Track the state of application memory using shadow

memory

• Track whether allocated and whether defined

Monitor every memory-related action by the application:

• System call

• Malloc, realloc, calloc, free, mmap, mumap, mremap

• Memory read or write

• Stack adjustment

At exit or on request, scan memory to check for leaks

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Shadow each byte of memory with one of 3 states:

Shadow Metadata

definedunaddressable uninitialized

allocate:

malloc, stack

deallocate

write

deallocate

allocate: mmap, calloc

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Shadow Memory

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defined

unaddr

uninit

defined

Shadow StackStack

Shadow HeapHeap

header

malloc

header

padding

unaddr

unaddr

unaddr

defined

uninit

defined

freed

unaddr

Performance Comparison

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Valgrindfailed

Valgrindfailed

Outline

System Overview

Example Tools

• Security

• Debugging

Open Source Project

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Dynamo

@HP Labs

on x86

DynamoRIO History

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Dynamo + RIO

DynamoRIO

1999

Dynamo

@HP Labs

on PA-RISC

RIO @MIT

(Runtime Introspection

and Optimization)

2001

late 1990’s 2000

Google

sponsors

Dr. Memory

DynamoRIO History Cont’d

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2001

VMware

acquires

Determina

Determina

security startup

open-sourced

BSD licensebinary releases

DynamoRIO

@MIT

2003 2007 2010

2002 2009

Google

sponsors

Dr. Memory

DynamoRIO Team

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VMwareDetermina

security startup

DynamoRIO

@MIT

DynamoRIO Open Source Project

Google Code

• BSD license

• Subversion repository

300 KLOC

Mostly C, some assembly

• Issue tracker

Google Groups

• User discussion forum/mailing list

• Developer mailing list

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http://dynamorio.org

Dr. Memory Open Source Project

Google Code

• http://code.google.com/p/drmemory

• LGPL 2.1 license

• Subversion repository

67 KLOC

Mostly C

• Issue tracker

Google Groups

• User discussion forum/mailing list

• Developer mailing list

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Potential Projects

Build a New Tool

• Code coverage

• Fuzzer

• Profiler: basic block, edge, function, etc.

• Malware sandbox

• Reverse engineering

Contribute to an Existing Tool

• Dr. Memory or Dr. Heapstat

• Revive PiPA or UMI

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Potential Projects Cont’d

Build a Tool Library

• Control flow, call graph, data dependence analysis

• Symbol table access

Contribute to Platform

• Buffer filling API

• Probe API

• Port to MacOS

• Port to ARM

• Debugger integration

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