phoenix-mstu / janus-mqtt-proxy

MITM proxy which can filter and modify MQTT packets

Modifying MQTT proxy

With this service you can transform MQTT topics and their payload by specifying transformation rules.

For example you have topics /some/topic1 and /some/another/topic2 on MQTT broker, and you have a client which needs them to be /root/topic1 and /root/topic2.

All you need is to create a yaml config with this rules:

broker_to_client:

  - topic: ^/some/topic1$
    template: '/root/topic1'
    val_map: {0: OFF, 1: ON}        # you can specify map to transform values
  
  - topic: ^/some/another/([^/]*)$  # you can use regex
    template: '/root/{{.f1}}'       # and place an extracted part into template


client_to_broker:

  - topic: ^/root/topic1$
    template: '/some/topic1'
    val_map: {OFF: 1, ON: 1}        # reverse value transformation

  # if you comment it, this topic will be readonly for client
  # - topic: ^/root/topic2$
  #   template: '/some/another/topic2'

And another yaml file with basic info:

broker_host: tcp://broker.host:1883
broker_login: login
broker_password: pass

clients:

  - login: some_login
    password: some_pass
    filters_config: your_filters.yaml
  
  # another client with no password
  - filters_config: another_filters.yaml

Then you can run proxy: ./proxy basic.yaml

Usage

The service is meant to be used inside a Docker container. Though it should work as an executable as well, if you manage to build it.

To run it as a Docker container you should:

1. Clone the repository
2. Create configs directory with your main.yaml and filters.yaml configs.
3. run docker build -t janus .
4. run docker run -v $(pwd)/configs:/configs/ janus /configs/main.yaml

Testing

There are a few integration tests which check basic functionality. You can also use them as a reference.

1. Clone the repository
2. cd smoke_tests
3. /run_tests.sh

More info

• The most advanced sample config is located in sample_configs/my_wirenboard_to_homeassistant.yaml. Look there for more examples.

• Article in English: https://medium.com/@phoenix.mstu/modifying-mqtt-proxy-bf6d8931ef60

• Article in Russian: https://habr.com/ru/company/funcorp/blog/497234/