Issue 3956 - Convert domain whitelisting filters

lib/abp2blocklist.js

Index: lib/abp2blocklist.js
diff --git a/lib/abp2blocklist.js b/lib/abp2blocklist.js
index 1bece259e455539c7aebdbf220479425f7eab0e3..fb90da33463b453806cae4fa5497cb31cef9223c 100644
--- a/lib/abp2blocklist.js
+++ b/lib/abp2blocklist.js
@@ -25,6 +25,18 @@ let punycode = require("punycode");
 
 const selectorLimit = 5000;
 const typeMap = filterClasses.RegExpFilter.typeMap;
+const whitelistableRequestTypes = (typeMap.IMAGE
+                                   | typeMap.STYLESHEET
+                                   | typeMap.SCRIPT
+                                   | typeMap.FONT
+                                   | typeMap.MEDIA
+                                   | typeMap.POPUP
+                                   | typeMap.OBJECT
+                                   | typeMap.OBJECT_SUBREQUEST
+                                   | typeMap.XMLHTTPREQUEST
+                                   | typeMap.PING
+                                   | typeMap.SUBDOCUMENT
+                                   | typeMap.OTHER);
 
 function parseDomains(domains, included, excluded)
 {
@@ -66,28 +78,38 @@ function convertElemHideFilter(filter, elemhideSelectorExceptions)
 }
 
 /**
- * Convert the given filter "regexpSource" string into a regular expression,
- * handling the conversion of unicode inside hostnames to punycode.
- * (Also deciding if the regular expression can be safely converted to and
- *  matched as lower case or not.)
+ * Parse the given filter "regexpSource" string. Producing a regular expression,
+ * extracting the hostname (if any), deciding if the regular expression is safe
+ * to be converted + matched as lower case and noting if the source contains
+ * anything after the hostname.)
  *
  * @param   {string} text regexpSource property of a filter
- * @returns {object} An object containing a regular expression string and a bool
+ * @returns {object} An object containing a regular expression string, a bool
  *                   indicating if the filter can be safely matched as lower
- *                   case: {regexp: "...", canSafelyMatchAsLowercase: true/false}
+ *                   case, a hostname string (or undefined) and a bool
+ *                   indicating if the source only contains a hostname or not:
+ *                     {regexp: "...",
+ *                      canSafelyMatchAsLowercase: true/false,
+ *                      hostname: "...",
+ *                      justHostname: true/false}
  */
-function toRegExp(text)
+function parseFilterRegexpSource(text)
 {
-  let result = [];
+  let regexp = [];
   let lastIndex = text.length - 1;
+  let hostname;
   let hostnameStart = null;
   let hostnameFinished = false;
+  let justHostname = false;
   let canSafelyMatchAsLowercase = false;
 
   for (let i = 0; i < text.length; i++)
   {
     let c = text[i];
 
+    if (hostnameFinished)
+      justHostname = false;
+
     // If we're currently inside the hostname we have to be careful not to
     // escape any characters until after we have converted it to punycode.
     if (hostnameStart != null && !hostnameFinished)
@@ -97,9 +119,11 @@ function toRegExp(text)
       if (!endingChar && i != lastIndex)
         continue;
 
-      let hostname = text.substring(hostnameStart, endingChar ? i : i + 1);
-      hostnameFinished = true;
-      result.push(escapeRegExp(punycode.toASCII(hostname)));
+      hostname = punycode.toASCII(
+        text.substring(hostnameStart, endingChar ? i : i + 1)
+      );
+      hostnameFinished = justHostname = true;
+      regexp.push(escapeRegExp(hostname));
       if (!endingChar)
         break;
     }
@@ -107,32 +131,32 @@ function toRegExp(text)
     switch (c)
     {
       case "*":
-        if (result.length > 0 && i < lastIndex && text[i + 1] != "*")
-          result.push(".*");
+        if (regexp.length > 0 && i < lastIndex && text[i + 1] != "*")
+          regexp.push(".*");
         break;
       case "^":
         if (i < lastIndex)
-          result.push(".");
+          regexp.push(".");
         break;
       case "|":
         if (i == 0)
         {
-          result.push("^");
+          regexp.push("^");
           break;
         }
         if (i == lastIndex)
         {
-          result.push("$");
+          regexp.push("$");
           break;
         }
         if (i == 1 && text[0] == "|")
         {
           hostnameStart = i + 1;
           canSafelyMatchAsLowercase = true;
-          result.push("https?://");
+          regexp.push("https?://");
           break;
         }
-        result.push("\\|");
+        regexp.push("\\|");
         break;
       case "/":
         if (!hostnameFinished &&
@@ -141,44 +165,27 @@ function toRegExp(text)
           hostnameStart = i + 1;
           canSafelyMatchAsLowercase = true;
         }
-        result.push("/");
+        regexp.push("/");
         break;
       case ".": case "+": case "$": case "?":
       case "{": case "}": case "(": case ")":
       case "[": case "]": case "\\":
-        result.push("\\", c);
+        regexp.push("\\", c);
         break;
       default:
         if (hostnameFinished && (c >= "a" && c <= "z" ||
                                  c >= "A" && c <= "Z"))
           canSafelyMatchAsLowercase = false;
-        result.push(c);
+        regexp.push(c);
     }
   }
 
-  return {regexp: result.join(""),
-          canSafelyMatchAsLowercase: canSafelyMatchAsLowercase};
-}
-
-function getRegExpTrigger(filter)
-{
-  let result = toRegExp(filter.regexpSource);
-
-  let trigger = {"url-filter": result.regexp};
-
-  // Limit rules to to HTTP(S) URLs
-  if (!/^(\^|http)/i.test(trigger["url-filter"]))
-    trigger["url-filter"] = "^https?://.*" + trigger["url-filter"];
-
-  // For rules containing only a hostname we know that we're matching against
-  // a lowercase string unless the matchCase option was passed.
-  if (result.canSafelyMatchAsLowercase && !filter.matchCase)
-    trigger["url-filter"] = trigger["url-filter"].toLowerCase();
-
-  if (result.canSafelyMatchAsLowercase || filter.matchCase)
-    trigger["url-filter-is-case-sensitive"] = true;
-
-  return trigger;
+  return {
+    regexp: regexp.join(""),
+    canSafelyMatchAsLowercase: canSafelyMatchAsLowercase,
+    hostname: hostname,
+    justHostname: justHostname
+  };
 }
 
 function getResourceTypes(filter)
@@ -223,9 +230,43 @@ function addDomainPrefix(domains)
   return result;
 }
 
-function convertFilter(filter, action, withResourceTypes)
+function convertFilterAddRules(rules, filter, action, withResourceTypes)
 {
-  let trigger = getRegExpTrigger(filter);
+  let parsed = parseFilterRegexpSource(filter.regexpSource);
+
+  // For the special case of $document whitelisting filters with just a domain
+  // we can generate an equivalent blocking rule exception using if-domain.
+  if (filter instanceof filterClasses.WhitelistFilter &&
+      filter.contentType & typeMap.DOCUMENT &&
+      parsed.justHostname)
+  {
+    rules.push({
+      trigger: {
+        "url-filter": ".*",
+        "if-domain": addDomainPrefix([parsed.hostname])
+      },
+      action: {type: "ignore-previous-rules"}
+    });
+    // If the filter contains other supported options we'll need to generate
+    // further rules for it, but if not we can simply return now.
+    if (!(filter.contentType | whitelistableRequestTypes))
+      return;
+  }
+
+  let trigger = {"url-filter": parsed.regexp};
+
+  // Limit rules to HTTP(S) URLs
+  if (!/^(\^|http)/i.test(trigger["url-filter"]))
+    trigger["url-filter"] = "^https?://.*" + trigger["url-filter"];
+
+  // For rules containing only a hostname we know that we're matching against
+  // a lowercase string unless the matchCase option was passed.
+  if (parsed.canSafelyMatchAsLowercase && !filter.matchCase)
+    trigger["url-filter"] = trigger["url-filter"].toLowerCase();
+
+  if (parsed.canSafelyMatchAsLowercase || filter.matchCase)
+    trigger["url-filter-is-case-sensitive"] = true;
+
   let included = [];
   let excluded = [];
 
@@ -241,7 +282,7 @@ function convertFilter(filter, action, withResourceTypes)
   else if (excluded.length > 0)
     trigger["unless-domain"] = addDomainPrefix(excluded);
 
-  return {trigger: trigger, action: {type: action}};
+  rules.push({trigger: trigger, action: {type: action}});
 }
 
 function hasNonASCI(obj)
@@ -352,18 +393,7 @@ ContentBlockerList.prototype.addFilter = function(filter)
 
   if (filter instanceof filterClasses.WhitelistFilter)
   {
-    if (filter.contentType & (typeMap.IMAGE
-                              | typeMap.STYLESHEET
-                              | typeMap.SCRIPT
-                              | typeMap.FONT
-                              | typeMap.MEDIA
-                              | typeMap.POPUP
-                              | typeMap.OBJECT
-                              | typeMap.OBJECT_SUBREQUEST
-                              | typeMap.XMLHTTPREQUEST
-                              | typeMap.PING
-                              | typeMap.SUBDOCUMENT
-                              | typeMap.OTHER))
+    if (filter.contentType & (typeMap.DOCUMENT | whitelistableRequestTypes))
       this.requestExceptions.push(filter);
 
       if (filter.contentType & typeMap.ELEMHIDE)
@@ -392,12 +422,6 @@ ContentBlockerList.prototype.generateRules = function(filter)
 {
   let rules = [];
 
-  function addRule(rule)
-  {
-    if (!hasNonASCI(rule))
-      rules.push(rule);
-  }
-
   let groupedElemhideFilters = new Map();
   for (let filter of this.elemhideFilters)
   {
@@ -426,7 +450,7 @@ ContentBlockerList.prototype.generateRules = function(filter)
       // this by converting to the attribute format [id="elementID"]
       selector = convertIDSelectorsToAttributeSelectors(selector);
 
-      addRule({
+      rules.push({
         trigger: {"url-filter": matchDomain,
                   "url-filter-is-case-sensitive": true},
         action: {type: "css-display-none",
@@ -436,11 +460,11 @@ ContentBlockerList.prototype.generateRules = function(filter)
   });
 
   for (let filter of this.elemhideExceptions)
-    addRule(convertFilter(filter, "ignore-previous-rules", false));
+    convertFilterAddRules(rules, filter, "ignore-previous-rules", false);
   for (let filter of this.requestFilters)
-    addRule(convertFilter(filter, "block", true));
+    convertFilterAddRules(rules, filter, "block", true);
   for (let filter of this.requestExceptions)
-    addRule(convertFilter(filter, "ignore-previous-rules", true));
+    convertFilterAddRules(rules, filter, "ignore-previous-rules", true);
 
-  return rules;
+  return rules.filter(rule => !hasNonASCI(rule));
 };