description = [[
Informs about cross-domain include of scripts. Websites that include
external javascript scripts are delegating part of their security to
third-party entities.
]]

---
-- @usage nmap -p80 --script http-refferer-checker.nse <host>
--
-- This script informs about cross-domain include of scripts by 
-- finding src attributes that point to a different domain. 
-- 
-- @output
-- PORT   STATE SERVICE REASON
-- 80/tcp open  http    syn-ack
-- | http-referer-checker: 
-- | Spidering limited to: maxdepth=3; maxpagecount=20;
-- |   http://css3-mediaqueries-js.googlecode.com/svn/trunk/css3-mediaqueries.js
-- |_  http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js?ver=3.4.2
-- 
---

categories = {"discovery", "safe"}
author = "George Chatzisofroniou"
license = "Same as Nmap--See http://nmap.org/book/man-legal.html"

local http = require "http"
local shortport = require "shortport"
local stdnse = require "stdnse"
local table = require "table"
local string = require "string"
local httpspider = require "httpspider"

portrule = shortport.port_or_service( {80, 443}, {"http", "https"}, "tcp", "open")

action = function(host, port)
 
    local crawler = httpspider.Crawler:new(host, port, '/', { scriptname = SCRIPT_NAME, 
                                                              maxpagecount = 30, 
                                                              maxdepth = -1, 
                                                              withinhost = 0,
                                                              withindomain = 0
                                                              })

    crawler.options.doscraping = function(url)
        if crawler:iswithinhost(url) 
        and not crawler:isresource(url, "js") 
        and not crawler:isresource(url, "css") then
            return true
        end
    end

    crawler:set_timeout(10000)

    if (not(crawler)) then
        return
    end

    local scripts = {}

    while(true) do

        local status, r = crawler:crawl()
        if (not(status)) then
            if (r.err) then
                return stdnse.format_output(true, ("ERROR: %s"):format(r.reason))
            else
                break
            end
        end

       if crawler:isresource(r.url, "js") and not crawler:iswithinhost(r.url) then
            scripts[tostring(r.url)] = true
       end

    end

    if next(scripts) == nil then
        return "Couldn't find any cross-domain scripts."
    end

    local results = {}
	for s, _ in pairs(scripts) do
		table.insert(results, s)
  	end

	results.name = crawler:getLimitations()
	
	return stdnse.format_output(true, results)

end