Add prints and better checking to HTTP CmdStagers

Admittedly, this code is more convoluted than it needs to be.

Author: wvu

lib/msf/core/exploit/cmdstager/http.rb

@@ -27,9 +27,25 @@ def start_service(opts = {})
   end
 
   def on_request_uri(cli, request)
-    if request['User-Agent'] =~ /^(?:Wget|curl)/
+    client = cli.peerhost
+
+    if (user_agent = request.headers['User-Agent'])
+      client << " (#{user_agent})"
+    end
+
+    print_status("Client #{client} requested #{request.raw_uri}")
+
+    if stager_instance.respond_to?(:user_agent)
+      agent_regex = stager_instance.user_agent
+    else
+      agent_regex = /.*/
+    end
+
+    if user_agent =~ agent_regex
+      print_status("Sending payload to #{client}")
       send_response(cli, exe)
     else
+      print_status("Sending 404 to #{client}")
       send_not_found(cli)
     end
   end