Unable to register U2F token from the Chromebook login window

Question

We have our own SSO server which has the feature to allow U2F token registration from within the authentication process.

This feature works well on a PC using Chrome (with or without the U2F browser extension). It also works well when used from the browser on the Chromebook after the user has successfully authenticated.

However when we enable SSO on Chromebook and try to register the U2F token during the authentication process, registration does not seem to work. After some debugging we find that the onMessage event listener is not being called after sending a U2F register request to the u2f_register_request channel.

However the same is not true for sign request (when authenticating after having registered using a PC). When we send a request to u2f_sign_request we successfully receive a message on the onMessage callback.

Has anyone encountered this issue before? or know of work around that will allow us to perform registration during the authentication process?

The following shows some of the code being used to post to the channel:

// 1. connect to extension

var port = chrome.runtime.connect("kmendfapggjehodndflmmgagdbamhnfd", {'includeTlsChannelId': true});

// 2. bind callback function

port.onMessage.addEventListener(function(message) {
// this callback not been invoked if post 'u2f_register_request' message to channel in chrome OS login page
     handler({'data': message});
});

// 3. post message to extension.

port.postMessage({
     type: 'u2f_register_request',
     signRequests: signRequests,
     registerRequests: registerRequests,
     timeoutSeconds: (typeof opt_timeoutSeconds !== 'undefined' ?
     opt_timeoutSeconds : u2f.EXTENSION_TIMEOUT_SEC),
     requestId: reqId
});

The code being used can be found at (https://github.com/Yubico/java-u2flib-server/blob/master/u2flib-server-demo/src/main/resources/assets/u2f-api.js)

The Chromebook information is as follows:

Google Chrome Version (and Chromebook info)
Version: 43.0.2357.125
Framework version: 6946.58.0 (Official Build) stable-channel kip
Software version: Google_Kip.5216.227.5
Start mode: Verified
Model: HP Chromebook 11 2100-2199 / HP Chromebook 11 G3