description = [[
Attempts to find the owner of an open TCP port by querying an auth
daemon which must also be open on the target system. The auth service,
also known as identd, normally runs on port 113.
]]
---
--@output
-- 21/tcp   open     ftp       ProFTPD 1.3.1
-- |_ auth-owners: nobody
-- 22/tcp   open     ssh       OpenSSH 4.3p2 Debian 9etch2 (protocol 2.0)
-- |_ auth-owners: root
-- 25/tcp   open     smtp      Postfix smtpd
-- |_ auth-owners: postfix
-- 80/tcp   open     http      Apache httpd 2.0.61 ((Unix) PHP/4.4.7 ...)
-- |_ auth-owners: dhapache
-- 113/tcp  open     auth?
-- |_ auth-owners: nobody
-- 587/tcp  open     submission Postfix smtpd
-- |_ auth-owners: postfix
-- 5666/tcp open     unknown
-- |_ auth-owners: root

-- The protocol is documented in RFC 1413.

author = "Diman Todorov"

license = "Same as Nmap--See http://nmap.org/book/man-legal.html"

categories = {"default", "safe"}

portrule = function(host, port)
	local auth_port = { number=113, protocol="tcp" }
	local identd = nmap.get_port_state(host, auth_port)

	return identd ~= nil
		and identd.state == "open"
		and port.protocol == "tcp"
		and port.state == "open"
end

action = function(host, port)
	local owner = ""

	local client_ident = nmap.new_socket()
	local client_service = nmap.new_socket()

	local catch = function()
		client_ident:close()
		client_service:close()
	end

	local try = nmap.new_try(catch)

	try(client_ident:connect(host, 113))
	try(client_service:connect(host, port))

	local localip, localport, remoteip, remoteport =
        	try(client_service:get_info())

	local request = port.number .. ", " .. localport .. "\r\n"

	try(client_ident:send(request))

	owner = try(client_ident:receive_lines(1))

	if string.match(owner, "ERROR") then 
		owner = nil
	else
		owner = string.match(owner,
                	"%d+%s*,%s*%d+%s*:%s*USERID%s*:%s*.+%s*:%s*(.+)\r?\n")
	end

	try(client_ident:close())
	try(client_service:close())

	return owner
end