How to listen to http requests in a Chrome extension and how to set the permissions for it in manifest.json

Question

I'm trying to realise the idea of waldalla to build a proxy server in a Google Chrome extension.

I understand how to code in a Chrome extension the server-facing side of the problem, i.e. sending HTTP requests and receiving responses, but I don't know how to do the client-facing side, i.e. listening on a defined port for HTTP requests from outside the browser.

I have read up on Chrome's Native Messaging API. However, from what I can see it is used for communication via stdin/stdout, not via HTTP.

So, how can I listen to HTTP requests in a Google Chrome extension? And how do I set the permissions for this in the extension's manifest.json file?

Answer 1

A Chrome extension has no way* to listen to network connections, at least arbitrary ones.

* Possible exception here being WebRTC, but that's not very useful for proxying standard HTTP.

Native Messaging is, indeed, a way to escape the API limitations by doing whatever you want in a native companion application that talks to the extension via STDIO.

[Extension] <-- STDIO --> [Native host] <-- anything, eg. HTTP --> [Client]

Note that it's not arbitrary STDIO, but a specific JSON-based native host protocol.

Also note that the extension will need to spawn a new copy of the native host application; it can't connect to an already running one.