Issue 6539, 6782 - Implement support for snippets

lib/snippets.js

Index: lib/snippets.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/snippets.js
@@ -0,0 +1,182 @@
+/*
+ * 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/>.
+ */
+
+"use strict";
+
+const {defaultMatcher} = require("matcher");
+const {RegExpFilter, WhitelistFilter} = require("filterClasses");
+const {verifySignature} = require("rsa");
+const {extractHostFromFrame, isThirdParty, stringifyURL} = require("url");
+const {checkWhitelisted} = require("whitelisting");
+const {FilterNotifier} = require("filterNotifier");
+const devtools = require("devtools");
+const info = require("info");
+
+const {typeMap} = RegExpFilter;
+
+const remoteURL = "https://easylist-downloads.adblockplus.org/snippets.js";
+
+let libraries = {local: "", remote: ""};
+let executableCode = new Map();
+
+function fetchText(url)
+{
+  return fetch(url, {cache: "no-cache"}).then(
+    response => response.ok ? response.text() : ""
+  );
+}
+
+function updateLibrary(name, text)
+{
+  libraries[name] = text;
+
+  executableCode.clear();
+}
+
+function checkLibrarySignature(url, text)
+{
+  return fetchText(`${url}.sig`).then(
+    signature => fetchText(browser.extension.getURL("/key")).then(
+      key => verifySignature(key.replace(/=/g, ""), signature, text)
+    )
+  );
+}
+
+function loadLibrary(name, url, {verify = true} = {})
+{
+  fetchText(url).then(text =>
+  {
+    if (text != libraries[name])
+    {
+      let check = verify ? checkLibrarySignature(url, text) :
+                    Promise.resolve(true);
+      check.then(ok =>
+      {
+        if (ok)
+          updateLibrary(name, text);
+      });
+    }
+  });
+}
+
+function loadLocalLibrary()
+{
+  loadLibrary("local", browser.extension.getURL("/snippets.js"),
+              {verify: false});
+}
+
+function loadRemoteLibrary()
+{
+  loadLibrary("remote", remoteURL);
+}
+
+function getExecutableCode(snippet)
+{
+  let code = executableCode.get(snippet);
+  if (code)
+    return code;
+
+  code = `
+    "use strict";
+    {
+      let localImports = Object.create(null);
+      let remoteImports = Object.create(null);
+      new Function("exports", ${JSON.stringify(libraries.local)})(
+        localImports
+      );
+      new Function("exports", ${JSON.stringify(libraries.remote)})(
+        remoteImports
+      );
+      let imports = Object.assign(Object.create(null),
+                                  localImports,
+                                  remoteImports);
+      let key = ${JSON.stringify(snippet)};
+      if (Object.prototype.hasOwnProperty.call(imports, key))
+      {
+        let value = imports[key];
+        if (typeof value == "function")
+          value();
+      }
+    }
+  `;
+
+  executableCode.set(snippet, code);
+  return code;
+}
+
+function injectCode(snippet, tabId, frameId)
+{
+  try
+  {
+    browser.tabs.executeScript(tabId, {
+      code: getExecutableCode(snippet),
+      frameId,
+      matchAboutBlank: true,
+      runAt: "document_start"
+    });
+  }
+  catch (error)
+  {
+  }
+}
+
+loadLocalLibrary();
+
+// Only Chrome supports dynamic loading of JS.
+if (info.platform == "chromium")
+{
+  loadRemoteLibrary();
+
+  // Download every 24 hours.
+  setInterval(loadRemoteLibrary, 24 * 60 * 60 * 1000);
+}
+
+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);
+  let hostname = extractHostFromFrame(frame);
+  let thirdParty = isThirdParty(urlObject, hostname);
+
+  let filter = defaultMatcher.matchesAny(urlString, typeMap.SNIPPET, hostname,
+                                         thirdParty, null, true);
+  if (!filter)
+    return;
+
+  let page = new ext.Page({id: tabId, url});
+
+  if (checkWhitelisted(page, frame))
+    return;
+
+  devtools.logRequest(page, urlString, "SNIPPET", hostname, thirdParty, null,
+                      true, filter);
+  FilterNotifier.emit("filter.hitCount", filter, 0, 0, page);
+
+  if (filter instanceof WhitelistFilter)
+    return;
+
+  for (let snippet of filter.snippets)
+    injectCode(snippet, tabId, frameId);
+});