Issue 6539, 6782 - Implement support for snippets

lib/scriptInjection.js

 /*
  * 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 cssInjection */
+/** @module scriptInjection */
 
 "use strict";
 
 const {RegExpFilter} = require("../adblockpluscore/lib/filterClasses");
 const {ElemHide} = require("../adblockpluscore/lib/elemHide");
 const {ElemHideEmulation} = require("../adblockpluscore/lib/elemHideEmulation");
+const {Snippets, compileScript} = require("../adblockpluscore/lib/snippets");
 const {checkWhitelisted} = require("./whitelisting");
 const {extractHostFromFrame} = require("./url");
 const {port} = require("./messaging");
 const {HitLogger} = require("./hitLogger");
 const info = require("info");
 
 // Chromium's support for tabs.removeCSS is still a work in progress and the
 // API is likely to be different from Firefox's; for now we just don't use it
 // at all, even if it's available.
 // See https://crbug.com/608854
 const styleSheetRemovalSupported = info.platform == "gecko";
 
 const selectorGroupSize = 1024;
 
 let userStyleSheetsSupported = true;
 
+let snippetsLibrarySource = "";
+let executableCode = new Map();
+
 function* splitSelectors(selectors)
 {
   // Chromium's Blink engine supports only up to 8,192 simple selectors, and
   // even fewer compound selectors, in a rule. The exact number of selectors
   // that would work depends on their sizes (e.g. "#foo .bar" has a size of 2).
   // Since we don't know the sizes of the selectors here, we simply split them
   // into groups of 1,024, based on the reasonable assumption that the average
   // selector won't have a size greater than 8. The alternative would be to
   // calculate the sizes of the selectors and divide them up accordingly, but
   // this approach is more efficient and has worked well in practice. In theory
@@ skipping 102 matching lines @@
   // Sometimes the old and new style sheets can be exactly the same. In such a
   // case, do not remove the "old" style sheet, because it is in fact the new
   // style sheet now.
   if (oldStyleSheet && oldStyleSheet != styleSheet)
     removeStyleSheet(tabId, frameId, oldStyleSheet);
 
   frame.injectedStyleSheets.set(groupName, styleSheet);
   return true;
 }
 
+function getExecutableCode(script)
+{
+  let code = executableCode.get(script);
+  if (code)
+    return code;
+
+  code = compileScript(script, [snippetsLibrarySource]);
+
+  executableCode.set(script, code);

[Manish Jethani, 2018/05/23 05:12:45]

Cache executable.

+  return code;
+}
+
+function executeScript(script, tabId, frameId)
+{
+  try
+  {
+    browser.tabs.executeScript(tabId, {
+      code: getExecutableCode(script),
+      frameId,
+      matchAboutBlank: true,
+      runAt: "document_start"
+    })
+    .catch(error =>
+    {
+      // Sometimes a frame is added and removed very quickly, in such cases we
+      // simply ignore the error.
+      if (error.message == "The frame was removed.")
+        return;
+
+      throw error;
+    });
+  }
+  catch (error)
+  {
+  }
+}
+
+port.on("snippets.executeScripts", (message, sender) =>
+{
+  if (checkWhitelisted(sender.page, sender.frame, null,
+                       RegExpFilter.typeMap.DOCUMENT))

[Manish Jethani, 2018/05/23 05:12:46]

Note: I'm not checking for ELEMHIDE here. I don't think ELEMHIDE should apply to
snippets. I'm not sure what we should do here, but applying ELEMHIDE seems
wrong.

[kzar, 2018/07/10 14:52:00]

So would a #@# exception filter be honoured?

[Manish Jethani, 2018/07/19 01:00:54]

Yes, in the initial version #@# will not work.

+  {
+    return;
+  }
+
+  let hostname = extractHostFromFrame(sender.frame);
+  for (let script of Snippets.getScriptsForDomain(hostname))
+    executeScript(script, sender.page.id, sender.frame.id);
+});

[Manish Jethani, 2018/05/23 05:12:46]

Note: No DevTools logging, I'll get it to eventually.

[kzar, 2018/07/10 14:52:00]

Please could you add this as a known limitation to the issue description?

[Manish Jethani, 2018/07/19 01:00:53]

I do intend to add DevTools logging in the initial version, but if I don't
manage to add it (in a separate patch) then I'll mention this in #6782.

[kzar, 2018/07/19 10:37:11]

Could you mention it in #6782, along with the #@# thing? You can remove them
again if you manage to work around.

Also the issue has barely any details in general, would you mind fleshing it out
so I can triage? That would help me review this code as well. For example, I
wouldn't have had to clarify about #@# if it was already mentioned in the
description.

+
 port.on("elemhide.getSelectors", (message, sender) =>
 {
   let selectors = [];
   let emulatedPatterns = [];
   let trace = HitLogger.hasListener(sender.page.id);
   let inline = !userStyleSheetsSupported;
 
   if (!checkWhitelisted(sender.page, sender.frame, null,
                         RegExpFilter.typeMap.DOCUMENT |
                         RegExpFilter.typeMap.ELEMHIDE))
@@ skipping 29 matching lines @@
     response.inlineEmulated = true;
 
   return response;
 });
 
 port.on("elemhide.injectSelectors", (message, sender) =>
 {
   updateFrameStyles(sender.page.id, sender.frame.id, message.selectors,
                     message.groupName, message.appendOnly);
 });
+
+fetch(browser.extension.getURL("/snippets.js"), {cache: "no-cache"})

[Manish Jethani, 2018/05/23 05:12:46]

Note: I deleted the part that loads a remote version of the library, checks the
signature, and so on. Let's keep it simple so we have something working.

[kzar, 2018/07/10 14:52:00]

No need to fetch this script, and to add the mapping in the metadata, we could
do something like let snippetLibraries = require("../snippets");` right?

[Manish Jethani, 2018/07/19 01:00:53]

We actually need this in text form (not as a JavaScript object), as per the
design. The idea is that any snippet library will be loaded in a "sandbox",
which is basically a Function object (not much in the way of security) for now.

[kzar, 2018/07/19 10:37:11]

Acknowledged.

+.then(response => response.ok ? response.text() : "")
+.then(text =>
+{
+  snippetsLibrarySource = text;
+});