[cb22] Are Embedded Devices Ready for ROP Attacks? -ROP verification for low-spec embedded devices- by Yuuma Taki

Are Embedded Devices Ready for ROP Attacks?
-ROP verification for low-spec embedded devices. -
YUUMA TAKI
1

Self introduction
Yuuma Taki
・Hokkaido Information University
Department of Information Media A Senior
・Interested in lower layer security around OS and CPU.
Having Researched KASLR deployment
using Prekern at SecHack365.
A Japanese security Hackathon
2

Overview
・Investigate possibilities of ROP attacks against OSs and processors
for embedded systems.
→ Execute vulnerable test programs on embedded system,
launch ROP Attack(details later).
→Emulate both high spec and low spec embedded devices
using QEMU.
3

Background
・Radically Increase demand for embedded systems
by proliferation of IoT devices.
→ Due to various restrictions in some embedded devices, cannot deploy
rich security systems. ・Low Power
・Small Capacity
・Low Electricity
Consumption
・High Power
・Large Capacity
・High Electricity
Consumption
4

Background
・Evolution of Return Oriented Programming(ROP) Attacks
→ROP attack is an attack combining code execution snippets
inside a program to perform arbitrary processing.
→Derivative techniques of ROP attacks are being researched.
・ROP attacks can be utilized to various architectures.
5

Previous Research
A ROP countermeasure:
Implementing security controls such as Control-Flow Integrity
Drawback:
High cost to execute the security controls.
→Implementing security control in low-spec embedded devices is difficult.
6

This Research
・Investigate embedded devices that have no ROP countermeasures.
・Devising a new countermeasures which can be implemented to
low spec embedded devices
7

ROP Overview
・What is ROP(Return Oriented Programming) ？
→Attack method devised to circumvent Nxbit security control.
・No eXecutable bit (NX bit)
→ Security control that disables code execution of code set
in the heap or stack region.
This can hinder shell code execution
by exploiting stack overflow vulnerabilities.
8

Visualizing ROP
・ROP Attack
→Trigger code execution by chaining code fragments called gadgets
into a ROP chain.
Command fragment 1
Command fragment 2
Command fragment 3
Command fragment 4
Command fragment 5
Command fragment 6
Ordinary Execution File
Command
Fragment 1
Command
Fragment 3
Command
Fragment 5
Command
Fragment 6
ROP Chain
Collect command
fragments needed
for attack
Code Region
Data Region
Execution File
ROP Chain
Embed into
ROP Chain
9

ROP on x86_64
・Execute system(/bin/sh) to steal control
Assembly Command Used
pop xxx: Contain rsp value into xxx register
ret: Same value for pop rip
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code
buf (0x10)
rbp
rsp
saved rbp
Return Address
rbp + 8
・
・
・
Stack Region Register
rdi: Store parameter 1
rsi: Store parameter 2
rdx: Store parameter 3
rip: Store next address for
execution
rbp: Store lowest address
inside the stack frame
rsp: Store stack top
address
10

・Write ROP chain by filling up to the return address with ‘A’
ROP on x86_64
11
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code
buf (0x10)
rbp
rsp
saved rbp
Return Address
rbp + 8
・
・
・
execution
address

ROP on x86_64
AAAAAAAA
AAAAAAAA
rsp
AAAAAAAA
0x400100
“/bin/sh” Address
‘system’
actual address
・After embedding ROP Chain
12
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code Stack Region Register
execution
address

ROP on x86_64
AAAAAAAA
AAAAAAAA
rsp
AAAAAAAA
0x400100
‘system’
actual address
13
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code Stack Region Register
rip: 0x400100
rbp:0x4141414141414141
address
・Right after processing functions (pop rbp; ret;)

ROP on x86_64
Stack top
“/bin/sh” address
gets stored into
rdi at pop rdi
execution
・pop rdi execution time
14
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code Stack Region
AAAAAAAA
AAAAAAAA
rsp
AAAAAAAA
0x400100
‘system’
actual address
Register
rdi: “/bin/sh” address
rip: 0x400102
rbp:0x4141414141414141
address

ROP on x86_64
By ret command
the ‘system’ actual
address gets stored
in rip
・ret execution time
15
0x400100: pop rdi
0x400102: ret
:
0x400200: pop rsi
0x400202: ret
:
0x400300: pop rdx
0x400302: ret
:
Assembly Code Stack Region
AAAAAAAA
AAAAAAAA
rsp
AAAAAAAA
0x400100
‘system’
actual address
Register
rdi: “/bin/sh” address
rip: ‘system’ actual address
rbp:0x4141414141414141
address

Effective Security Countermeasures
against ROP①
Address Space Layer Randomization(ASLR):
ASLR is a security measurement that randomize the address space
where program code and data are stored,
which makes access to specific code and data difficult.
KASLR is ASLR deployed to the kernel
16

ASLR
Assembly Code
buf (0x10)
rbp
rsp
saved rbp
Return Address
rbp + 8
・
・
・
execution
address
17
0x400100:
0x400102:
:
0x400200:
0x400202:
:
0x400300:
0x400302:
:
pop rdi
ret
pop rsi
ret
pop rdx
ret
??????
??????
??????
??????
??????
??????
Address of the instruction has been randomized, so building ROP chains is not possible.

Effective Security Countermeasures
against ROP②
18
Control-Flow Integrity (CFI):
Security measure that creates a model of normal control flow then compares
that model to the flow at execution time to detect anomalous control flow.

CFI
normal control flow
main()
↓
function1()
↓
function2()
↓
function3()
Jumping to Instructions in Other Functions with ROP
main()
↓
function1()
↓
function3()
Record normal control flow at compile time.
ok!

ASLR Weaknesses
・In less than 32 bit address space, address leaks can be triggered
by brute force attacks.
→Not realistic to implement in low spec embedded devices
with narrow address space.
20

CFI Weakness
・Resource intensive for the processor, therefore, requires high capability CPU
→Difficult to implement into low spec embedded devices.
21

Details regarding the ROP evaluation in
this research
・Using simple ROP attacks.
→Find embedded devices that can be overtaken with simple ROP
・Use QEMU to emulate embedded devices.
→QEMU enables us to check the register and memory content
in the guest environment.
22

R0P examination using QEMU
The schematics is as following:
23

ROP Examination
・Conducted ROP Examination in the following three environments.
- CentOS6 on i686
- Raspberry Pi OS on Arm Cortex-a53
24

ROP demo on CentOS6 on i686
・Emulate CentOS6 on i686 using QEMU and launch ROP attack
against vulnerable test server.
Attack
25

Attack Target Environment
OS: CentOS6.0
Arch: x86
Server program source code: http://kozos.jp/samples/rop-sample.html
Security measures:
・NX bit: Active
・SSP: Inactive
・ASLR: Inactive
・CFI: Inactive
26

ROP Demo against CentOS6 on i686
27

Examination Results
・Because many security measures such as SSP and ASLR are active by default,
unless those are made inactive a simple
ROP attack will not result in gaining control.
28

ROP against Raspi OS on Arm Cortex-a53
・Emulate Raspi OS on Arm Cortex-a53 using QEMU and launch ROP attack
against vulnerable test server.
29

Attack Target Environment
OS: Raspberry Pi OS
Arch: Armv8-A
Server program source code: http://kozos.jp/samples/rop-sample.html
Processor execution state: AArch32
Security Measures:
・NX bit: Active
・SSP: Inactive
・ASLR: Inactive
・CFI: Inactive
30

ROP demo against Raspi OS on Arm Cortex-a53
31

Exploit code (ROP chain part)
R0 register: store parameter 1
pc register: Program counter register
r4 register: Not used here
32

Examination Results
・Raspberry Pi 3B+ is a high spec embedded device and many security
measures are available, therefore without disabling these security measures
ROP attack was unsuccessful.
33

Verification summary so far
Security※
Target NX bit ASLR SSP CFI
CentOS6 on i686 〇〇〇 ×
RaspiOS on Arm Cortex-A53 〇〇〇 ×
ZephyrOS on Arm Cortex-M0 ？？？？
※Enabled by default

ROP attack to low spec embedded device
Investigate possibilities of ROP attacks against ZephyrOS on Arm Cortex-M0.
→Survey results, ZephyrOS on Arm Cortex-M0
may not have countermeasures against ROP.

ZephyrOS
・An Embedded OS that can run on boards with strict restrictions.
・ZephyrOS can be utilized to various boards.
e.g.
Arduino-mega2560, microbit, STM32F0 series…

Memory protection in ZephyrOS
The following Memory protection are implemented.
・Stack protection
・Memory isolation
・Thread isolation
Requires MPU

Memory Protection Unit(MPU)
・In, low-spec processors that cannot implement MMU,
Critical hardware for Memory protection
・Divide the address space into several areas,
set access rights for each area.

Arm Cortex-M0
・As a low-power processor, it is used in STM32F0 series board and microbit.
・Memory Protection Unit(MPU) is not implemented,
security using MPU used in many OS cannot be applied.

ROP countermeasure in low spec
embedded devices.
・Currently the following countermeasures can be considered for implementation.
40

Conclusion
・When CFI and ASLR are not applied in the program gaining control is possible
with a simple ROP attack.
・Consider implementing ROP countermeasures in low spec embedded devices,
implement security measures if necessary.
41

Acknowledgements
・Special thanks to the National Institute of Information and Communications
Technology organized SecHack365 and its trainer Hiroaki Sakai ,
who showed the basics of program execution and debug methods,
which this research is founded upon.
Thank you Mr.Sakai and all SecHack365 staff.
42

Thank You
For Your Kind Attention.
43

[cb22] Are Embedded Devices Ready for ROP Attacks? -ROP verification for low-spec embedded devices- by Yuuma Taki

Recommended

More Related Content

Similar to [cb22] Are Embedded Devices Ready for ROP Attacks? -ROP verification for low-spec embedded devices- by Yuuma Taki (20)

More from CODE BLUE (20)

Recently uploaded (20)

[cb22] Are Embedded Devices Ready for ROP Attacks? -ROP verification for low-spec embedded devices- by Yuuma Taki