A Zigbee security research toolkit for the RaspBee, nRF52840 and CC2531 radio modules.
In order to develop and test improved network join procedures using asymmetric encryption, a custom proof of concept protocol based on the IEEE 802.15.4 standard was developed and is also included in the toolkit.
The radio modules need to be flashed with our custom firmware, prior to using it with ZigBear.
The instructions, on how to do this, vary depending on the chosen transceiver.
To remotely flash the firmware of a RaspBee module, execute
$ make remote-install-firmwareOn the host, docker is required for compilation of µracoli.
On the RaspberryPi, GCFFlasher_internal is required (included in the installation of deCONZ).
The SSH target for the RaspBee can be configure in the Makefile.
To flash a nRF52840 dongle, the nRF Connect software is required.
Detailed instructions on how to flash using nRF Connect, can be found here.
To flash a CC2531 dongle, the CC Debugger from Texas Instruments is required.
Detailed instructions on how to flash using the CC Debugger can be found here.
To launch the ZigBear Python CLI locally, simply execute
$ make runRequires python3, pipenv and optionally tkinter for the virtual lamp
To remotely execute ZigBear via SSH on a RaspberryPi + RaspBee, execute
$ make remote-runRequires python3 and pipenv on the RaspberryPi.
The ZigBear CLI can be either preconfigured using command line arguments
usage: __main__.py [-h] [-L [LOG_FILE]] [-l {DEBUG,INFO,WARN,ERROR}]
[-c {nrf,cc2531,raspbee,socket}] [-d DEVICE] [-C CHANNEL]
[-w WIRESHARK_HOST] [-r RECEIVE_PORT] [-t TARGET_PORT]
ZigBear CLI
optional arguments:
-h, --help show this help message and exit
Logging:
-L [LOG_FILE], --log-file [LOG_FILE]
Log output to LOG_FILE. If -L is specified but
LOG_FILE is omitted, "zigbear.log" will be used. If
the argument is omitted altogether, logging will not
take place at all.
-l {DEBUG,INFO,WARN,ERROR}, --log-level {DEBUG,INFO,WARN,ERROR}
Log messages of severity LOG_LEVEL or higher. Only
makes sense if -L is also specified (Default: INFO)
ZigBear:
-c {nrf,cc2531,raspbee,socket}, --connector {nrf,cc2531,raspbee,socket}
configure connector type
-d DEVICE, --device DEVICE
transceive from DEVICE (Default: /dev/ttyACM0)
-C CHANNEL, --channel CHANNEL
radio channel for listening and sending (Default: 25)
-w WIRESHARK_HOST, --wireshark-host WIRESHARK_HOST
wireshark host (Default: 127.0.0.1)
-r RECEIVE_PORT, --receive-port RECEIVE_PORT
receive port for the socket connector (Default: 8080)
-t TARGET_PORT, --target-port TARGET_PORT
target port for the socket connector (Default: 9090)
or interactively configured using the CLI commands after launching ZigBear
To select the connector for your hardware, execute
connector <connector> <connector> must be one of the following options:
- nrf
- cc2531
- raspbee
- socket
After selecting a connector you can choose a radio channel
channel <number>
<number> must be between and including 11 and 25.
With the selected channel you can now start to transmit raw data (hexadecimal string) using the send command
send <hexadecimalString>
An application communicates with our custom protocol stack, which consists of the following layers.
The MAC Layer communicates via one of the connectors with the hardware and vice versa.
The MAC layer of the IEEE 802.15.4 protocol is used. This layer sends and receives data directly using one of the radio connectors.
The Network Layer has several tasks. One is the partitioning of packages which exceed the maximum size of 80 byte. Another task is to send ACK packages. A retry mechanism is implemented to send packages again if no response was received.
The Security Layer handles encryption and decryption of packages.
For the encryption and decryption of packets, that are exchanged between devices that share a network key, the symmetric encoding AES-GCM is used. Advanced Encryption Standard (AES) is a block cipher which decodes 16 byte blocks with byte substitution, permutations and transformations. For these operations a key with a length of 128, 192 or 256 Bit is used.
As AES-GCM is an authenticated encryption algorithm, it is also capable of providing integrity via the authentication tag, that is produced as a result of it. If an encrypted message has an invalid authentication tag, it will not be decrypted or relayed to the application layer.
To exchange the network key the Elliptic Curve Diffie-Hellman (ECDH) algorithm is used. The communication partners exchange their public keys and calculate a shared key using their private keys. This shared key is passed through HKDF to turn it into a cryptographically stronger key.
The exchange of the actual network key is encrypted using the key derived from the shared key. This secure channel could also be used for negotiating different details of the connection in the future. After the network key is exchaged, any keys relating to that exchange are dropped by both communication partners. A new set of keys has to be generated for each exchange, thus providing forward secrecy for key exchanges.
The Application Layer offers a socket interface for the development of high level applications. It consists of a Session and a Listener class where Session has methods to send a network key and a initiation package and Listener has methods to register and connect to a broadcast. Both can send and receive packages.
The projects comes with a virtual lamp as an example application for our custom protocol. By sending messages between two ZigBear instances, where one acts as device and the other one as coordinator, the "lamp" (a colored GUI window) can be switched off, on or set to specific brightness values.
To test the lamp in combination with a coordinator, follow these steps:
- Launch two instances of ZigBear from the project directory with
$ make run
- Use UDP connector (
socket), for simplicity. - Enter inverse send and receive ports on the two clients.
- Launch one client into
devicemode and the other intocoordinatormode. - Enter
infoon the device client to display its random address (in the following steps named as<device_address>). - Perform the following commands on the coordinator client to pair it with the device client.
initiate <device_address> sendkey <device_address>
- Start the virtual lamp example application on the device client with the command
lamp - Control the lamp by sending on of the following commands from the coordinator client to the device client:
toggle <device_address>
brightness <device_address> <brightness>
Development of ZigBear is on-going, and there is still much to do.
Some of the things that could be interesting to work on, in no particular order, are listed below:
- ZigBee Light Link attacks
- Automated network join attacks
- Remote factory reset attacks
- Remote firmware update attacks
- Formal verification of custom protocol
- Authorization for custom protocol
- All Your Bulbs Are Belong to Us: Investigating the Current State of Security in Connected Lighting Systems
- IoT Goes Nuclear: Creating a ZigBee Chain Reaction
- Hacking Intelligent Building
- Security Analysis of Zigbee
- ZigBee Exploited - The Good, the Bad and the Ugly (Paper)
- ZigBee Exploited - The Good, The Bad and The Ugly (Video)
- Improved Secure ZigBee Light Link Touchlink Commissioning Protocol Design