more error handling, deal with user error

Author: busterb

modules/exploits/linux/misc/drb_remote_codeexec.rb

@@ -43,8 +43,7 @@ def initialize(info = {})
 
       register_options(
         [
-          OptString.new('URI',
-            "The URI of the target host (druby://host:port) (overrides RHOST/RPORT)"),
+          OptString.new('URI', [false, "The URI of the target host (druby://host:port) (overrides RHOST/RPORT)", nil]),
           Opt::RHOST(nil, false),
           Opt::RPORT(8787)
         ])
@@ -110,6 +109,16 @@ def method_syscall(p)
   end
 
   def exploit
+    if !datastore['URI'].blank? && !datastore['RHOST'].blank?
+      print_error("URI and RHOST are specified, unset one")
+      return
+    end
+
+    if datastore['URI'].blank? && datastore['RHOST'].blank?
+      print_error("neither URI nor RHOST are specified, set one")
+      return
+    end
+
     unless datastore['URI'].blank?
       serveruri = datastore['URI']
     else
@@ -130,12 +139,12 @@ class << p
 
     methods.each do |method|
       begin
-        print_status("trying to exploit #{method}")
+        print_status("Trying to exploit #{method} method")
         send("method_" + method, p)
         handler(nil)
         break
       rescue SecurityError, DRb::DRbConnError, NoMethodError
-        print_warning("target is not vulnerable to #{method}")
+        print_warning("Target is not vulnerable to #{method} method")
       end
     end