local nmap = require "nmap"
local shortport = require "shortport"
local sip = require "sip"
local stdnse = require "stdnse"
local table = require "table"

description = [[
Enumerates a SIP Server's allowed methods.

The script works by sending an OPTION request to the server and checking for
the value of the Allow header in the response.
]]

---
-- @usage
-- nmap --script=sip-methods -sU -p 5060 <targets>
--
--@output
-- 5060/udp open  sip
-- | sip-methods: 
-- |_  INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY, INFO


author = "Hani Benhabiles"

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

categories = {"default", "safe", "discovery"}


portrule = shortport.port_or_service(5060, "sip", {"tcp", "udp"})

action = function(host, port)
    local status, session, response
    session = sip.Session:new(host, port)
    status = session:connect()
    if not status then
	return "ERROR: Failed to connect to the SIP server."
    end

    status, response = session:options()
    if status then
	-- If port state not set to open, set it to open.
	if nmap.get_port_state(host, port) ~= "open" then
	    nmap.set_port_state(host, port, "open")
	end

	-- Check if allow header exists in response
	local allow = response:getHeader("allow")
	if allow then
	    return stdnse.format_output(true, allow)
	end
    end
end