MOSQUITTO BROKER - allow support for Lua-Based Mosquitto Plugin

[puterboy]

Describe the issue you are experiencing

(Note that I initially posted this request to the "Community Forum" but the moderators helpfully suggested that I post here instead.)

I would like to be able to filter out invalid MQTT messages at the Mosquitto broker level.

For example, my temperature sensors which involve 4 entities (temperature, humidity, RSSI, batter) often get invalid data which I can detect by humidity > 100.

I would like to filter these out wholesale at the broker level by doing something like:

function acl_check(clientid, username, topic, payload, qos, retain)
    local json = require("cjson")  -- Make sure Lua JSON library is available
    local data = json.decode(payload)
    
    -- Reject if "humidity" exists and is greater than 100
    if data.humidity and tonumber(data.humidity) > 100 then
        return mosq.AUTH_DENIED
    end
    
    return mosq.AUTH_GRANTED
end

And then modifying mosquitto.conf by adding:

plugin /usr/lib/mosquitto/auth_plugin.so
auth_plugin /etc/mosquitto/auth_filter.lua

My understanding is that this is not possible currently since you can't add plugins to the add-on.

Is that correct?
If so, is there any way to add the plugin capability to the broker add-on?

What type of installation are you running?

Home Assistant OS

Which operating system are you running on?

Home Assistant Operating System

Which add-on are you reporting an issue with?

Mosquitto broker

What is the version of the add-on?

6.5.0

Steps to reproduce the issue

As above

System Health information

NA

Anything in the Supervisor logs that might be useful for us?

Anything in the add-on logs that might be useful for us?

Additional information

No response

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[puterboy]

Please keep open. Thanks.