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Z3sec

Z3sec is an open-source penetration testing framework comprising a set of command line tools for ZigBee security research. Primary targets of the framework are ZigBee-certified devices that implement either the ZigBee Light Link (ZLL) or the ZigBee 3.0 standard.

Introduction

ZigBee is a wireless low-power standard in the Internet of Things (IoT). While ZLL is an application profile designed for connected lighting systems, ZigBee 3.0 comprises various applications in the domain of smart home networks. In order to simplify the process of setting up and managing a ZigBee network, the ZLL standard introduced a commissioning procedure called touchlink commissioning. This commissioning procedure is an optional feature in the ZigBee 3.0 standard.

Z3sec can send arbitrary touchlink commands, and thus exploit security weaknesses in the touchlink commissioning procedure. A local attacker is able to perform denial-of-service attacks or to take control over ZigBee-certified products. For more information about the security weaknesses of touchlink commissioning and the procedures of attacks, please see [1].

A demonstration of Z3sec can be watched on Youtube.

Installation

Dependencies

• gnuradio
• gnuradio-dev
• gr-foo
• gr-ieee802.15.4
• KillerBee
• scapy-radio (https://bitbucket.org/cybertools/scapy-radio)
• Ipython
• tcpdump
• Wireshark (optional)
• python-crypto
• python-sphinx (docs)
• python-numpydoc (docs)
• setuptools
• (see install_dependencies.sh for a complete list)

Install steps (Ubuntu 16.10 x86_64)

1. git clone https://github.com/IoTsec/Z3sec.git
2. cd Z3sec
3. Install all needed dependencies with:

• bash ./install_dependencies.sh (Password for sudo is requested when needed.)

4. Install Z3sec with:

• sudo python setup.py install

5. Add the leaked ZLL master key in ~/.config/z3sec/touchlink_crypt.ini. This configuration file is created at the first run of Z3sec.

Hardware

Z3sec supports two radio platforms: Ettus USRPs and radios, which are supported by the KillerBee framework. In order to use Ettus USRPs, it is necessary to install GnuRadio.

All tools of Z3sec are tested with the Ettus USRP B200 (GnuRadio) and the MoteIV Tmote Sky (KillerBee).

Ettus USRP

1. Connect the USRP to the computer.
2. Verify the successful connection via uhd_find_devices.
3. Use the --sdr parameter in the Z3sec tools.

KillerBee Radio

1. Flash the KillerBee firmware as described on https://github.com/riverloopsec/killerbee
2. Connect the device to the computer.
3. Execute sudo zbid to get the device name.
4. Use the --kb argument together with the device name (e.g. --kb /dev/ttyUSB0) in the Z3sec tools.

Tools

Z3sec is a collection of tools to evaluate security features of ZigBee-certified products. The Z3sec tools assume basic knowledge of IEEE 802.15.4 and the ZigBee standards. For a detailed description of the parameters of each tool, please refer to the output generated by the --help argument.

Please also see our Wiki, where we provide a step-by-step tutorial on touchlink attacks.

z3sec_touchlink

This tool partially reimplements the touchlink commissioning procedure from as an initiator. It consists of several sub-tools, which can send specific touchlink commands. The received signal strength of the touchlink commands must be above a certain threshold on the targeted device, i.e., these command must be sent from a particular proximity, also denoted as touchlink range. For an evaluation of the wireless range of these tools, please see [1].

For the description of all parameters of a sub-tool, please refer to the help message, e.g., z3sec_touchlink scan --help.

• scan: Actively searches for touchlink-enabled devices in the touchlink range and displays an overview of all received scan responses. Here, and for all subsequent sub-commands, it is possible to specify the channels on which shall be searched for devices. By default, only channel 11 is scanned.

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <all|primary|secondary|11...26> scan
  

• anti-scan: Suppress scan requests of other touchlink initiators by impersonating them. This tool monitors channel 11 until a touchlink scan request of another initiator is received. This scan request is cloned and transmitted on all other channels. Touchlink-enabled devices on these channels respond immediately to the spoofed scan request, and won't reply to the scan request by the legitimate initiator.

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) anti-scan
  

• reset: Reset a touchlink-enabled device in touchlink range to factory-new. The target device leaves its current network and search for new networks. The target device has to be recommissioned before it can be controlled again. The --target option needs to be set to the extended address of a touchlink-enabled device. It can be discovered by executing a scan and copying the <src_addr_ext> of an answering device before.

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <channel> reset --target <addr_ext>
  

  Due to an implementation bug, some (old) touchlink-enabled devices can be reset, even if they are not in touchlink range. This bug can be exploited in the following way:

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <channel> reset --target <addr_ext> --no_scan
  

• identify: Trigger the identify action (e.g. blinking) of a touchlink-enabled device in touchlink range. The identify duration can be set up to a theoretical maximum duration of 0xFFFE seconds (approximately 18 hours):

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <channel> identify --target <addr_ext> --duration <duration>
  

  This command also supports the bypassing of the proximity check with --no_scan.

• update: Update the channel of a touchlink-enabled device in touchlink range. If the channel is changed, the targeted device cannot communicate with its legitimate network anymore.

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <channel> update --target <addr_ext> --channel_new <channel>
  

• join: Request a touchlink-enabled device in touchlink range to join a new network. The configuration of the new network can be explicitly set:

    z3sec_touchlink (--kb /dev/ttyUSBX | --sdr) --channels <channel> join --target <addr_ext> --channel_new <channel> --network_key <network_key_hex>
  

Note (1)

For the join command, the specification of the pre-configured touchlink link key (also known as ZLL Master Key) in "~/.config/z3sec/touchlink_crypt.ini is required. This key was leaked in March 2015 and can be found online.

Note (2)

The z3sec_touchlink tool is not able to send acknowledgements within the required time frame. However, some devices expect an acknowledgment for their scan response, otherwise they abort the touchlink transaction. In order to still send touchlink commands to those devices, one can impersonate another ZigBee device in the wireless range of the target device by setting --src_addr, --src_addr_ext, --src_pan_id, and --src_pan_id_ext according to the values obtained by a prior scan. The impersonated device then sends the acknowledgment upon the reception of the scan response.

z3sec_key_extract

With this tool, the network key transmitted during a legitimate touchlink commissioning procedure can be extracted and decrypted.

As ZigBee traffic source, a radio device can sniff actively for touchlink commissioning procedures on a specific channel '<channel>':

z3sec_key_extract (--kb /dev/ttyUSBX | --sdr) --channel <channel>

Alternatively, the ZigBee traffic can be read from a pre-captured pcap file:

z3sec_key_extract --pcap /path/to/file.pcap

Note

For this tool, the specification of the pre-configured touchlink link key (also known as ZLL Master Key) in ~/.config/z3sec/zll_master_key.txt is required. This key was leaked in March 2015 and can be found online.

z3sec_control

This tool keeps track of all ZigBee devices and networks on a specific channel.

If the network key of a ZigBee network is known, this tool can be used to interactively send command frames to devices of this network in order to change their state. The network key for the network needs to be known.

z3sec_control (--kb /dev/ttyUSBX | --sdr) --channel <channel> --pan_id <pan_id> --network_key <network_key_hex>

Please see our Wiki (Tutorial 2: Takeover Attack) for a detailed description.

Note

The command packet is automatically encrypted using the given network key and all the address fields and sequence numbers are overwritten with those of the impersonated and spoofed device.

Literature

For more information about the security of touchlink commissioning and an extensive evaluation of the presented attacks, please see:

[1] P. Morgner, S. Mattejat, Z. Benenson, C. Müller, F. Armknecht: Insecure to the Touch: Attacking ZigBee 3.0 via Touchlink Commissioning. In Proceedings of the 10th ACM Conference on Security & Privacy in Wireless and Mobile Networks (WiSec'17, Boston, MA, July 18-20, 2017)

If you refer to Z3sec in a publication, please cite [1].