Add "username" and "password" script args to ftp-bounce.nse

It has scoped args in the straight form of "ftp-bounce.<arg>" which is
apparently how this works now (at least what other scripts seem to use) instead
of using actual subtables like in http://seclists.org/nmap-dev/2008/q2/567

CHANGELOG

@@ -1,5 +1,8 @@
 # Nmap Changelog ($Id$); -*-text-*-
 
+o [NSE] Added script arguments "username" and "password" to ftp-bounce
+  to override the default anonymous:IEUser@ login combination. [Kris]
+
 o [Zenmap] Made IP addresses be sorted by octet, not by their string
   representation. For example, 10.1.1.2 is now sorted before
   10.1.1.10, when it was the opposite before. This was reported by

scripts/ftp-bounce.nse

@@ -5,6 +5,9 @@ author = "Marek Majkowski"
 license="Same as Nmap--See http://nmap.org/book/man-legal.html"
 
 ---
+-- @args ftp-bounce.username Username to login with instead of "anonymous"
+-- @args ftp-bounce.password Password to login with instead of "IEUser@"
+--
 -- @output
 -- PORT   STATE SERVICE
 -- 21/tcp open  ftp
@@ -72,6 +75,27 @@ get_ftp_code = function(socket)
 	return fcode
 end
 
+local get_login = function()
+	local user, pass
+	local k
+
+	for _, k in ipairs({"ftp-bounce.username", "username"}) do
+		if nmap.registry.args[k] then
+			user = nmap.registry.args[k]
+			break
+		end
+	end
+
+	for _, k in ipairs({"ftp-bounce.password", "password"}) do
+		if nmap.registry.args[k] then
+			pass = nmap.registry.args[k]
+			break
+		end
+	end
+
+	return user or "anonymous", pass or "IEUser@"
+end
+
 action = function(host, port)
 	local socket = nmap.new_socket()
 	local result;
@@ -79,6 +103,7 @@ action = function(host, port)
 	local isAnon = false
 	local isOk   = false
 	local sendPass = true
+	local user, pass = get_login()
 	local fc
 	
 	socket:set_timeout(10000)
@@ -105,7 +130,7 @@ action = function(host, port)
 	
 	socket:set_timeout(5000)
 	-- USER
-	socket:send("USER anonymous\r\n")
+	socket:send("USER " .. user .. "\r\n")
 	fc = get_ftp_code(socket)
 	if (fc >= 400 and fc <= 499) or (fc >= 500 and fc <= 599) then
 		socket:close()
@@ -130,7 +155,7 @@ action = function(host, port)
 
 	-- PASS
 	if sendPass then
-		socket:send("PASS IEUser@\r\n")
+		socket:send("PASS " .. pass .. "\r\n")
 		fc = get_ftp_code(socket)
 		if (fc >= 500 and fc <= 599) or (fc >= 400 and fc <= 499) then
 			socket:close()