Issue 6469 - Inject API wrappers only if there's a filter match

lib/scriptInjection.js

Index: lib/scriptInjection.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/scriptInjection.js
@@ -0,0 +1,72 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-present eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @module scriptInjection */
+
+"use strict";
+
+const {defaultMatcher} = require("matcher");
+const {RegExpFilter} = require("filterClasses");
+const {extractHostFromFrame, isThirdParty, stringifyURL} = require("url");
+
+let {typeMap} = RegExpFilter;
+
+function injectScript(tabId, frameId)
+{
+  try
+  {
+    browser.tabs.executeScript(tabId, {
+      file: "/inject.preload.js",
+      frameId,
+      matchAboutBlank: true,
+      runAt: "document_start"
+    });
+  }
+  catch (error)
+  {
+  }
+}
+
+browser.webNavigation.onCommitted.addListener(({tabId, frameId, url}) =>
+{
+  // There's a bug in Chrome that causes webNavigation.onCommitted to get
+  // dispatched twice if there's a URL filter present, therefore we must listen
+  // for all URLs and do an explicit check here.
+  // https://crbug.com/827855
+  if (!/^(https?:\/\/|about:blank\b|about:srcdoc\b)/.test(url))
+    return;
+
+  let urlObject = new URL(url);
+  let urlString = stringifyURL(urlObject);
+
+  let frame = ext.getFrame(tabId, frameId);
+  if (!frame)
+    return;
+
+  let hostname = extractHostFromFrame(frame);
+  let thirdParty = isThirdParty(urlObject, hostname);
+
+  let filter = defaultMatcher.matchesAny(urlString, typeMap.WEBRTC, hostname,
+                                         thirdParty, null, false);
+  if (!filter)
+    return;
+
+  // As long as there's a matching filter, inject the API wrappers. We could
+  // check if the URL is whitelisted or if the filter is a whitelisting filter,
+  // but it's not worth it (i.e. false positives are OK).
+  injectScript(tabId, frameId);
+});