How get raw response body inside a Web Extension for Firefox 55?

Question

I try to get the raw response body inside a Web Extension using Firefox 55.0.3.

Only "solutions" I have seen for now:

• Repeat the request (I absolutly don't want to repeat the request)
• Using Javascript to get innerHTML attribute of HTML tags such as head and body (tell me if I'm wrong, but with a solution like that I will not always have the whole content, for example I will get nothing in case of response without HTML. So it will never be the real raw response and in some case it will simply not work.)

Also, I saw this answer for Chrome (from 2015) using the debugger, but I wasn't able to do it with Firefox. This kind of solutions are interesting, I read Mozilla documentation about devtools but I didn't find a way of using the network tab of webtools interface with Javascript inside a Web Extension.

To give you more details, my goal is to intercept the full request and response from server (header and body). This is not a problem to do it, except for the response body.

Here an example of code to get the request body: (background script)

browser.webRequest.onBeforeRequest.addListener(
    function (e) {
        console.log(e);
    },
    {urls: ["http://*/*", "https://*/*"]},
    ["requestBody"]
)

Here some documentations that I used (there is more, but these links are all official):

• Mozilla documentation about Web Extension
  • Intercept HTTP requests
  • webRequest
  • webRequest.onHeadersReceived
  • webRequest.onBeforeRequest
  • webRequest.onBeforeSendHeaders

Here some examples of Web Extensions.

Any ideas, solutions or even explainations "why this is not possible" are welcome, thank you in advance for your time !

Cheers++

Answer 1

This is now available, as of Firefox 57: browser.webRequest.filterResponseData allows you to add a listener via browser.webRequest.onBeforeRequest which receives, and allows you to modify the response.

You can see an example in the Mozilla github webextensions-examples repo