Land rapid7#4148, @wchen-r7 fixed rapid7#4133

Author: jhart-r7

modules/exploits/windows/browser/msvidctl_mpeg2.rb

@@ -75,6 +75,13 @@ def initialize(info = {})
     @javascript_encode_key = rand_text_alpha(rand(10) + 10)
   end
 
+  def get_srvhost
+    # If the SRVHOST isn't the default 0.0.0.0, obviously the user wants to
+    # specify, so we will not force source_address()
+    return datastore['SRVHOST'] if datastore['SRVHOST'] != '0.0.0.0'
+    Rex::Socket.source_address(cli.peerhost)
+  end
+
   def on_request_uri(cli, request)
 
     if (request.uri.match(/\.gif$/i))
@@ -187,7 +194,7 @@ def on_request_uri(cli, request)
     j_memory     = rand_text_alpha(rand(100) + 1)
     j_counter    = rand_text_alpha(rand(30) + 2)
 
-    host = Rex::Socket.source_address(cli.peerhost) + ":" + (datastore["SRVPORT"].to_s)
+    host = get_srvhost + ":" + (datastore["SRVPORT"].to_s)
     gif_uri = "http#{(datastore['SSL'] ? 's' : '')}://#{host}"
     if ("/" == get_resource[-1,1])
       gif_uri << get_resource[0, get_resource.length - 1]