From ca1eb8cf5abdf33321884badf1b928bcbd334183 Mon Sep 17 00:00:00 2001
From: Peter Snyder <psnyde2@uic.edu>
Date: Sat, 14 Oct 2017 17:39:27 -0500
Subject: [PATCH] add much needed documentation about whats going on in the
background script (most importantly, the cookie setting code)
---
background_scripts/background.js | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/background_scripts/background.js b/background_scripts/background.js
index 879eb5c..74533d5 100644
--- a/background_scripts/background.js
+++ b/background_scripts/background.js
@@ -65,6 +65,12 @@
}, 1000);
// Listen for updates to the domain rules from the config page.
+ // The two types of messages that are sent to the background page are
+ // "rulesUpdate", which comes from the config page, indicating the domain
+ // blocking / matching rules have changed, and the "rulesForDomains"
+ // message, which comes from the browserAction popup, and is a request
+ // for information about "here are the domains of the frames on the
+ // current page, which rules are being used to match them".
rootObject.runtime.onMessage.addListener(function (request, ignore, sendResponse) {
const [label, data] = request;
@@ -95,6 +101,18 @@
const requestOptions = ["blocking", "responseHeaders"];
// Inject the blocking settings for each visited domain / frame.
+ // This needs to be done syncronously, so that the DOM of the visited
+ // page can be instrumented at "document_start" time. This means we
+ // can't do any of the "obvious" techniques for loading the "what should"
+ // be blocked in this frame" information (ie using the storage API).
+ // So, instead, we halt at the http query point, match the domain being
+ // loaded against the current rule set, pack the set of standards
+ // that should be blocked into a base64 encoded bitfield, and then
+ // push that to the page as a cookie.
+ //
+ // The page then reads the information about what standards to block
+ // out of the cookie (by decoding and unpacking the bitfield), and then
+ // deletes the cookie, so nothing is left behind.
rootObject.webRequest.onHeadersReceived.addListener(function (details) {
const url = details.url;