Use tiny var names by default.

lib/rex/exploitation/jsobfu.rb

@@ -74,14 +74,16 @@ class JSObfu
       @rand_gen = Rex::RandomIdentifierGenerator.new(
         :max_length => 15,
         :first_char_set => Rex::Text::Alpha+"_$",
-        :char_set => Rex::Text::AlphaNumeric+"_$"
+        :char_set => Rex::Text::AlphaNumeric+"_$",
+        :min_length => 1
       )
     end
 
     # @return [String] a unique random var name that is not a reserved keyword
     def random_var_name
+      len = 1
       loop do
-        text = random_string
+        text = @rand_gen.generate(len)
         unless has_key?(text) or
           RESERVED_KEYWORDS.include?(text) or
           BUILTIN_VARS.include?(text)
@@ -89,6 +91,7 @@ class JSObfu
           self[text] = nil
           return text
         end
+        len += 1
       end
     end
 
@@ -97,15 +100,10 @@ class JSObfu
       super or (@parent and @parent.has_key?(key))
     end
 
-    # @return [String] a random string
-    def random_string
-      @rand_gen.generate
-    end
-
   end
 
   #
-  # The maximum length of a string that will be passed through
+  # The maximum length of a string that can be passed through
   # #transform_string without being chopped up into separate
   # expressions and concatenated
   #