knxunlocker

A C# tool that uses the official KNX SDK to bruteforce a locked KNX device, which is a device where the BCU key is set and you want to unlock it. The BCU key is only a four byte key but it needs to be either guessed or extracted from the memory or the KNX device is useless. Some devices (like some of Merten) do not validate the key and recovery is not needed.

Can I reset my device without the BCU Key

Probably not. Some vendors can reflash their devices.

How does this tool work ?

You need either a KNX GW or KNX USB Interface and the device address. The knxunlocker is basically a bruteforcer. Bruteforcing the key is tricky because the key is one of 2^32 possibilities and the KNX BUS is quite slow (~9-11 tries per seconds) The bruteforcer supports three modes

• level 1: tries well known default keys
• level 2: tries a list of keys from all kind of wordlists (keys.txt) or a custom wordlist or your choice.
• level 3: tries the whole key space (with 10 tries per seconds, can take up to 13 years because the KNX bus is really slow)

If your KNX device shows the message "system hacked bcu key xx1234xx" (1234 is just an example) you can use the options --middle to generate a wordlist and use the option --dictionaryKeys to use the wordlist.
See the following issue for an example of the message Issue.

Some other features:

• The bruteforce stores the progress in a text file with to continue where it left off.
• The tool can discover network KNX GWs and usb KNX dongles and output the needed connection string

Usage

# discover a KNX GW or USB device for bruteforce to be used
knxunlocker -N 
Discovering network devices for 10 seconds
Found 1 devices
Type=KnxIpTunneling;HostAddress=192.168.42.193;SerialNumber=0001:0052177F;ProtocolType=Tcp;UseNat=True
# you need to know the KNX device address (three digits) beforehand. This can be easily detected by clicking the program button on the device
# start the bruteforcer 
knxunlocker -c Type=KnxIpTunneling;HostAddress=192.168.42.193;SerialNumber=0001:0052177F;ProtocolType=Tcp;UseNat=True -t 1.1.62
# if the bruteforcer found the key, you can reset the key via the ETS (KNX engineering Software)

The bruteforce takes too long, what are my other options

• You can try recover the key from memory of the device by dumping the flash: This heavily depends on the device and if hardware protection is enabled (might need advanced attacks like glitching)
• If you have multiple devices with the same key (assumption) you can accelerate the cracking process by using multiple KNX buses (Multiple cracking attempts on the same bus are not going to be faster). Other tools might be more useful.
• Contact the vendor

Pre built binaries

The tool has been prebuilt and its so large because its a single executable including the matching dotnet runtime + default keys. Checkout the Releases section.

Built

The project is based on dotnet core and you should only need the dotnet SDK to build it.

# build it
dotnet build
# run the tool with --help
dotnet run -- --help
# build a standalone binary
dotnet publish -c Release -r win-x64 --self-contained
dotnet publish -c Release -r linux-x64 --self-contained

Contribution

If you found a bug, want a new feature, got a question, feel free to open a issue anytime. Pull requests are welcome :-)

Othter informations

• knxmap can bruteforce keys as well but has limited support for KNX GWs and USB Dongles

TODOs

• Write more documentation about the bruteforce idea
• Add the keys to binary
• Check for typos
• Test the tooling more