Issue 4450 - Prevent ElemHide filters with empty domains

lib/filterClasses.js

Index: lib/filterClasses.js
diff --git a/lib/filterClasses.js b/lib/filterClasses.js
index ebfe551604cf296e582fbd6e7cdeca87bbe66237..27dff31eccaa77d4dda7ed512185f8688208873d 100644
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -22,6 +22,28 @@
 let {FilterNotifier} = require("filterNotifier");
 let {extend} = require("coreUtils");
 
+// Helper function used to determine if a filter has any empty domains or not.
+function emptyDomains(domains, separator)
+{
+  let emptySoFar = true;
+  for (let i = 0; i < domains.length; i++)
+  {
+    switch (domains[i])
+    {
+      case separator:
+        if (emptySoFar)
+          return true;
+        emptySoFar = true;
+      break;
+      case "~":
+      break;
+      default:
+        emptySoFar = false;
+    }
+  }
+  return emptySoFar;
+}
+
 /**
  * Abstract base class for filters
  *
@@ -924,6 +946,9 @@ ElemHideBase.fromText = function(text, domain, isException, tagName, attrRules,
       return new InvalidFilter(text, "filter_elemhide_nocriteria");
   }
 
+  if (domain && emptyDomains(domain, ElemHideBase.prototype.domainSeparator))

[Wladimir Palant, 2016/10/06 08:06:14]

Why have this function rather than /(^|,)~?(,|$)/.test(domain)? Yes, you would
duplicate the separator character but the result would be considerably faster.

[kzar, 2016/10/06 08:53:55]

Done.

+    return new InvalidFilter(text, "filter_empty_domain");

[Wladimir Palant, 2016/10/06 08:06:14]

filter_invalid_domain? We allow empty domains, but here the domain is invalid.

[kzar, 2016/10/06 08:53:56]

Done.

+
   if (isException)
     return new ElemHideException(text, domain, selector);