Configure BLE only supports 4 Key Pairs

[virtualwebber]

Currently using OMG on an Atom M5 Lite and using the decoding function with 4 devices. On trying to add 5 the device on saving the 5th line will disappear.

To Reproduce

• Go to Configure BLE
• Enter 5 Key pairs and click save - 5th line will not be retained.

Expected behavior
Unless this is a limitation i would expect the 5th line to be retained.

Environment (please complete the following information):

• OpenMQTTGateway version used DEV 382fa5

[DigiH]

Just to clarify, this is about the MAC:Key entries for the newly introduced BLE decryption functionality.

A limit of four devices would be very restrictive.

@plambrechtsen any insight on this?

[plambrechtsen]

There is the config parameter

define JSON_BLE_AES_CUSTOM_KEYS 256 // 42 byte BLE Custom Key * 6 rounded up to 256.

OpenMQTTGateway/main/User_config.h

Line 695 in 382fa5e

# define JSON_BLE_AES_CUSTOM_KEYS 256 // 42 byte BLE Custom Key * 6 rounded up to 256.

My concern was allocating too much memory and storage so I opted for a smaller number.

It can easily be increased to 512/1024 as long as it doesn’t cause an issue on the particular board due to memory limitations.

I successfully added 64 on my ESP with 4mb flash when I had the setting at 2048.

[plambrechtsen]

The other important thing was to use a space and not a carriage return as a delimiter when adding the key pairs.
Perhaps I should have supported both as the interface leads itself to think you can have multiple keys on each row. I just had the logic doing a split on space.
If the client side JavaScript that is disabled here gets enabled the keys are validated before posting to OMG.

OpenMQTTGateway/main/config_WebContent.h

Line 244 in 382fa5e

//const char ble_script[] = "function bkv(){let e=document.getElementById('bk'),t=document.getElementById('bke'),l=e.value.trim();0===l.length||/^[A-Fa-f0-9]{32}$/.test(l)?(t.textContent='',e.style.color=''):(t.textContent='Invalid key',e.style.color='red')}function kpv(){let e=document.getElementById('kp'),t=document.getElementById('kpe'),l=e.value.split(/ /),n=/^[A-Fa-f0-9]{12}:[A-Fa-f0-9]{32}$/,o=l.map((e,t)=>({line:e,index:t})).filter(e=>!n.test(e.line));if(0===e.value.trim().length||0===o.length)t.textContent='',e.style.color='';else{let i=o.map(e=>e.index+1).join(', ');t.textContent=`Invalid format on line(s): ${i}`,e.style.color='red'}}";

That caused build issues on one board due to space issues. Which was also the reason why I limited the number of keys as I wasn't sure the impact would be across the supported board fleet.

[DigiH]

The other important thing was to use a space and not a carriage return as a delimiter when adding the key pairs.

@virtualwebber might this have been your issue, as currently there should be 6 pairs possible?

@1technophile what do you think the best compromise might be here, between allowed device pairs and memory concerns?

[virtualwebber]

The other important thing was to use a space and not a carriage return as a delimiter when adding the key pairs.

@virtualwebber might this have been your issue, as currently there should be 6 pairs possible?

@1technophile what do you think the best compromise might be here, between allowed device pairs and memory concerns?

Not my issue unfortunately. I have tried various combinations and the last line (5th line) disappears when you click save.

Click Save

[plambrechtsen]

Have you tried tweaking that size limit and rebuilding OMG and deploying it on your device. I did have differencing experiences on a few ESP32's I tested with.

But if you changed the line: https://github.com/1technophile/OpenMQTTGateway/blob/development/main/User_config.h#L695

#      define JSON_BLE_AES_CUSTOM_KEYS 2048

It will support a lot more devices.

[virtualwebber]

Have you tried tweaking that size limit and rebuilding OMG and deploying it on your device. I did have differencing experiences on a few ESP32's I tested with.

But if you changed the line: https://github.com/1technophile/OpenMQTTGateway/blob/development/main/User_config.h#L695

#      define JSON_BLE_AES_CUSTOM_KEYS 2048

It will support a lot more devices.

Thanks @plambrechtsen. I have only been updating the device via the web page, so would need to look at how doing it the way you have suggested. Any pointers as a start?/

[plambrechtsen]

It's all in the fantastic documentation @virtualwebber that @DigiH has written about using VSCode + PlatformIO to build it yourself.

https://docs.openmqttgateway.com/upload/builds.html

Or use Build from the web.

https://docs.openmqttgateway.com/upload/gitpod.html

[virtualwebber]

It's all in the fantastic documentation @virtualwebber that @DigiH has written about using VSCode + PlatformIO to build it yourself.

https://docs.openmqttgateway.com/upload/builds.html

Thank you @plambrechtsen @DigiH :)

[1technophile]

@1technophile what do you think the best compromise might be here, between allowed device pairs and memory concerns?

For regular usages without TLS that should be fine, when using TLS this is where the memory management is more challenging.

[DigiH]

It's all in the fantastic documentation @virtualwebber that @DigiH has written about using VSCode + PlatformIO to build it yourself.

I've only really made smaller additions to these parts of the docs, the original documentation is from @1technophile - so credit where credit is due ;)

@plambrechtsen maybe you want to add some documentation about how to extend the MAC:key pairs in custom builds in the relevant section

https://github.com/1technophile/OpenMQTTGateway/blob/development/docs/use/webui.md#bluetooth-low-energy---ble