NTUSTxTDOH 資訊安全基礎工作坊基礎逆向教育訓練

TEEMO KNOWS BINARY
TDOH x TAIWAN TECH 2015/11/29
aaaddress1

SELF INTRODUCTION
➤ 馬聖豪 (aaaddress1)
➤ 義守大學資訊工程二年級
➤ Reverse Engineering Skills
➤ Windows / Mac OS /Android
➤ TDoHacker Core Member
➤ HITCON 2015 CMT:
➤ AIDS
➤ x86靜態手花詐欺術
➤ Wooyun WhiteHat: x86手花詐欺
➤ 逢甲2015行動計算研討會: AIDS
➤ 成功大學2015行動APP競賽

SELF INTRODUCTION
➤ Hack BOT
➤ CrackShield / MapleHack
➤ Tower Of Savior
➤ FaceBook: Adr’s FB
➤ Isu Hack
➤ 競時通防爆PING
➤ CSharp,VB,C/CPlus,
x86,Python,Smali,Swift

OUTLINE
➤ main() is not the really main
➤ OllyDBG:Baby First (Exam)
➤ Return-oriented Programming
➤ Overflow: Revo Wolf(Exam)
➤ Fuzzing
➤ Make a fuzzer in C++
➤ How to fuzzing with Z3

SWEET REMINDER
Tool
https://goo.gl/4sJRtB
Exam
https://goo.gl/xUYkoz

REALLY MAIN
➤ Label “_start” is really main.
➤ CRTStartUp is loaded in label “_start”.
(To init RTC/new/delete/arg…etc)
➤ Find programmer’s main (normal c plus compile)
➤ Find the address calling GetCommandLine
➤ Find the address calling exit() or cexit()
➤ Programmer’s main function is between them.

DEMO
Olly Debugger:Really Main

EXAM
Olly Debugger: Baby First
&
Take a break!

ROPReturn-oriented-Programming

WE NEED TO
KNOW MORE
BEFORE ROP

X86 CALLING
COVENTION
&
STACK FRAMES

ROP
[EBP+0 ] = Pointer to old EBP
[EBP+4 ] = Return Address
[EBP+8 ] = First Parameter
[EBP+C ] = Second Parameter
[EBP+10 ] = Third Parameter
…etc
[EBP+8 + 4*index] =
Parameter[index]

ROP
VOID
FUNC()
{
INT A =
0;
INT B =
1;
INT C =
2;
[EBP - 4] =0
[EBP - 8] =1
[EBP - C] =2
push EBP
mov
EBP,ESP
SUB ESP,
LEN

ROP
VOID FUNC(){
NFUNC(ARG1,ARG2,AR
G3…)
}
push ebp
mov ebp,esp
.
.
push arg3
push arg2
push arg1
call nFunc

ROP
Stack
ESP + 0
ESP + 4
ESP + 8
ESP + C
ESP + 10
ESP + 14

ROP
Stack
ESP + 0 Old EBP
ESP + 4
ESP + 8
ESP + C
ESP + 10
ESP + 14
_______EIP

ROP
Stack
EBP + 0
=ESP
Old EBP
EBP + 4
EBP + 8
EBP + C
EBP + 10
EBP + 14
_______EIP

ROP
Stack
EBP - 8
=ESP
Buffer
EBP - 4 Buffer
EBP + 0 Old EBP
EBP + 4
EBP + 8
EBP + C
_______EIP

ROP
Stack
EBP - 8
=ESP
1
EBP - 4 Buffer
EBP + 0 Buffer
EBP + 4 Old EBP
EBP + 8
EBP + C
_______EIP

ROP
Stack
EBP - 8
=ESP
return Address
EBP - 4 1
EBP + 0 Buffer
EBP + 4 Buffer
EBP + 8 Old EBP
EBP + C
_______EIP

ROP
Stack
EBP - 8
=ESP
return Address
EBP - 4 1
EBP + 0 Buffer
EBP + 4 Buffer
EBP + 8 Old EBP
EBP + C

ROP
Stack
EBP - 8
=ESP
EBP
EBP - 4 return Address
EBP + 0 1
EBP + 4 Buffer
EBP + 8 Buffer
EBP + C Old EBP
_______EIP

ROP
Stack
EBP + 0
=ESP
EBP
EBP + 4 return Address
EBP + 8 1
EBP + C Buffer
EBP + 10 Buffer
EBP + 14 Old EBP
_______EIP

ROP
_______EIP
Stack
EBP - 8
=ESP
return Address
EBP - 4 1
EBP + 0 Buffer
EBP + 4 Buffer
EBP + 8 Old EBP
EBP + C

ROP
Stack
EBP - 4
=ESP
1
EBP + 0 Buffer
EBP + 4 Buffer
EBP + 8 Old EBP
EBP + C
EBP + 10
_______EIP

ROP
Stack
EBP + 0
= ESP
Buffer
EBP + 4 Buffer
EBP + 8 Old EBP
EBP + C
EBP + 10
_______EIP

LET’S PLAY
WITH
BEEF
OVERFLOW

BUFFER OVERFLOW
➤ We just can see , cannot modify the application.
➤ For Exploit?
➤ Overflow local variables. (EBP+N are good friend to us)
➤ Do something for get control EIP/RIP.

BUFFER OVERFLOW
[EBP-8]
[EBP-10]

BUFFER OVERFLOW
How to let data ==
“admin”?

BUFFER OVERFLOW
Stack
ESP Old EBP
_______EIP

BUFFER OVERFLOW
Stack
EBP
=ESP
Old EBP
_______EIP

BUFFER OVERFLOW
Stack
EBP - 10 Buffer
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP
_______EIP

BUFFER OVERFLOW
Stack
EBP - 10 Buffer
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP
_______EIP
Variable “name”

BUFFER OVERFLOW
Stack
EBP - 10 Buffer
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP
_______EIP
Variable “data”

BUFFER OVERFLOW
Stack
EBP - 10 Buffer
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP_______EIP

BUFFER OVERFLOW
Stack
EBP - 10 Buffer
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP_______EIP
If you input “aaaa”

BUFFER OVERFLOW
Stack
EBP - 10 aaaa
EBP - C Buffer
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP_______EIP
If you input “aaaa”

BUFFER OVERFLOW
Stack
EBP - 10 aaaa
EBP - C BBBB
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP_______EIP
If you input “aaaaBBBB”

BUFFER OVERFLOW
Stack
EBP - 10 REVO
EBP - C WOLF
EBP - 8
0x6C6C6548
= lleH
EBP - 4
0x0000216F
=x00x00!o
EBP
=ESP
Old EBP_______EIP
If you input
“OVERFLOW”

IF WE INPUT MORE
WORDS…?
MAGIC!

BUFFER OVERFLOW
Stack
EBP - 10 REVO
EBP - C WOLF
EBP - 8 revo
EBP - 4 wolf
EBP
=ESP
Old EBP_______EIP
If you input
“OVERFLOWoverflow”

BUFFER OVERFLOW
Stack
EBP - 10 AAAA
EBP - C AAAA
EBP - 8 imda
EBP - 4 x00x00x00n
EBP
=ESP
Old EBP_______EIP
SO, We can input
“AAAAAAAAadmin”

DANGER FUNCTION
#include <iostream>
printf, fprintf, snprintf, vprintf, …etc

EXAM
Overflow: Revo wolf
&
Take a break!

EXAM
Overflow: 7$BUY TICKETS
&
Take a break!

EXAM
Overflow: Lee Sin can Read
&
Take a break!

FUZZING
Fuzzing the key with
Z3.py

“ Fuzz testing or fuzzing is a software testing technique,
often automated or semi-automated, that involves
providing invalid, unexpected, or random data to the
inputs of a computer program. The program is then
monitored for exceptions such as crashes, or failing
built-in code assertions or for finding potential memory
leaks. Fuzzing is commonly used to test for security
problems in software or computer systems. It is a form
of random testing which has been used for testing
hardware or software.
From Wikipedia
WHAT IS
FUZZING?

When we need to
fuzz?A. Prove that something is always true
B. Fuzzing for something unexpected
C.Fuckinnnnnnnnnnnnng Crypto
D.A lot of choice, find one is correct

Your said :
Get the key is easy?

YOU THINK
REVERSING IS:
SOLVING
PROBLEMS?
BRAIN FUCKING (O)

FUZZING
Key= adr
‘a’ = 0x61,’d’ = 0x64, r =
0x72

FUZZING
Key= adr
0x00726461
= x00x72x64x61
= x00adr

FUZZING
How to find the key
matching the factors?

MAKE A MINI
FUZZER
IN C PLUS PLUS

0x20 to 0x7E,
Visible ASCII Char Range

BUT…
IF LENGT OF THE KEY
ISN’T JUST 3 WORDS?

Z3 BEGIN
➤Get and Install Python2.7
✴ Z3.py script environment
✴ www.python.org
➤You can use python basically
➤Get Z3.py for Windows
✴ Prove tool
✴ github.com/Z3Prover/z3/wiki/Using-Z3Py-on-Windows

猜謎
➤ 無腦
➤ 很軟
➤ 手有毒

FUZZING(Z3)
Include Z3 function to your python script
like you use #include <iostream> in C++

FUZZING(Z3)
BitVec(“Name” , BitCount)
For example:
1.char a => a = BitVec(“a”, 8)
2.short b => b = BitVec(“b”, 16)
3.int c => c = BitVec(“C”, 32) => Int(“c”)
4.bool e => e = BitVec(‘e’, 8)

FUZZING(Z3)
Solve(All rules ), Z3 will auto fuzz all variables,
and find a result(JUST ONE RESULT!).
Then, print all results of variables.

FUZZING(Z3)
If you have a looooot of rules,
you can use Solver().
Solver.add() can remember
all rules you requested.

FUZZING(Z3)
If you want to check current
whether rules can come true,
you just use: Solver.check()

FUZZING(Z3)
If Z3 cannot find any result,
check() will reply you “unsat”.

FUZZING(Z3)
If Z3 can find any result,
check() will reply you “sat”.

FUZZING(Z3)
Finally, if you get “sat”,
you can use: Solver.model()
It will save a result in it.
Use model[Variable Name],
and get the answer by String

FUZZING(Z3)
So,How to fuzz the key with z3?

EXAM
Fuzzing: ShacoBuysCrusts
&
Take a Break!

EXAM
Fuzzing:
AIS3 Final Exam Binary

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