Do not cname-uncloak same-origin network requests

Same-origin as per URL address of the main document. Currently the
fix only affect top-level pages.

Related issue:
- uBlockOrigin/uBlock-issues#1062

The previous behavior can be restored by toggling the advanced
setting `cnameIgnoreRootDocument` to `false`.

platform/firefox/vapi-background-ext.js

@@ -19,7 +19,7 @@
  Home: https://github.com/gorhill/uBlock
 */
 
-// For background page
+/* globals browser */
 
 'use strict';
 
@@ -69,7 +69,7 @@ import {
  super();
  this.pendingRequests = [];
  this.canUncloakCnames = browser.dns instanceof Object;
- this.cnames = new Map([ [ '', '' ] ]);
+ this.cnames = new Map([ [ '', null ] ]);
  this.cnameIgnoreList = null;
  this.cnameIgnore1stParty = true;
  this.cnameIgnoreExceptions = true;
@@ -110,7 +110,7 @@ import {
  if ( 'cnameReplayFullURL' in options ) {
  this.cnameReplayFullURL = options.cnameReplayFullURL === true;
  }
- this.cnames.clear(); this.cnames.set('', '');
+ this.cnames.clear(); this.cnames.set('', null);
  this.cnameFlushTime = Date.now() + this.cnameMaxTTL * 60000;
  // https://github.com/uBlockOrigin/uBlock-issues/issues/911
  // Install/remove proxy detector.
@@ -171,16 +171,18 @@ import {
  return Array.from(out);
  }
  canonicalNameFromHostname(hn) {
- const cn = this.cnames.get(hn);
- if ( cn !== undefined && cn !== '' ) {
- return cn;
+ const cnRecord = this.cnames.get(hn);
+ if ( cnRecord !== undefined && cnRecord !== null ) {
+ return cnRecord.cname;
  }
  }
- processCanonicalName(hn, cn, details) {
+ processCanonicalName(hn, cnRecord, details) {
+ if ( cnRecord === null ) { return; }
+ if ( cnRecord.isRootDocument ) { return; }
  const hnBeg = details.url.indexOf(hn);
  if ( hnBeg === -1 ) { return; }
  const oldURL = details.url;
- let newURL = oldURL.slice(0, hnBeg) + cn;
+ let newURL = oldURL.slice(0, hnBeg) + cnRecord.cname;
  const hnEnd = hnBeg + hn.length;
  if ( this.cnameReplayFullURL ) {
  newURL += oldURL.slice(hnEnd);
@@ -194,11 +196,11 @@ import {
  details.aliasURL = oldURL;
  return super.onBeforeSuspendableRequest(details);
  }
- recordCanonicalName(hn, record) {
+ recordCanonicalName(hn, record, isRootDocument) {
  if ( (this.cnames.size & 0b111111) === 0 ) {
  const now = Date.now();
  if ( now >= this.cnameFlushTime ) {
- this.cnames.clear(); this.cnames.set('', '');
+ this.cnames.clear(); this.cnames.set('', null);
  this.cnameFlushTime = now + this.cnameMaxTTL * 60000;
  }
  }
@@ -221,8 +223,9 @@ import {
  ) {
  cname = '';
  }
- this.cnames.set(hn, cname);
- return cname;
+ const cnRecord = cname !== '' ? { cname, isRootDocument } : null;
+ this.cnames.set(hn, cnRecord);
+ return cnRecord;
  }
  regexFromStrList(list) {
  if (
@@ -257,26 +260,20 @@ import {
  return r;
  }
  }
- if (
- details.type === 'main_frame' &&
- this.cnameIgnoreRootDocument
- ) {
- return;
- }
+ const isRootDocument = details.type === 'main_frame' &&
+ this.cnameIgnoreRootDocument;
  const hn = hostnameFromNetworkURL(details.url);
- const cname = this.cnames.get(hn);
- if ( cname === '' ) { return; }
- if ( cname !== undefined ) {
- return this.processCanonicalName(hn, cname, details);
+ const cnRecord = this.cnames.get(hn);
+ if ( cnRecord !== undefined ) {
+ return this.processCanonicalName(hn, cnRecord, details);
  }
  return browser.dns.resolve(hn, [ 'canonical_name' ]).then(
  rec => {
- const cname = this.recordCanonicalName(hn, rec);
- if ( cname === '' ) { return; }
- return this.processCanonicalName(hn, cname, details);
+ const cnRecord = this.recordCanonicalName(hn, rec, isRootDocument);
+ return this.processCanonicalName(hn, cnRecord, details);
  },
  ( ) => {
- this.cnames.set(hn, '');
+ this.cnames.set(hn, null);
  }
  );
  }