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

description = [[
Looks for signature of known server compromises.

Currently, the only signature it looks for is the one discussed here:
http://blog.unmaskparasites.com/2009/09/11/dynamic-dns-and-botnet-of-zombie-web-servers/.
This is done by requesting the page <code>/ts/in.cgi?open2</code> and
looking for an errant 302 (it attempts to detect servers that always
return 302). Thanks to Denis from the above link for finding this
technique! 
]]

---
--@output
-- Interesting ports on www.sopharma.bg (84.242.167.49):
-- PORT     STATE SERVICE    REASON
-- 80/tcp   open  http       syn-ack
-- |_ http-malware-host: Host appears to be clean
-- 8080/tcp open  http-proxy syn-ack
-- |  http-malware-host: 
-- |  |  Host appears to be infected (/ts/in.cgi?open2 redirects to http://last-another-life.ru:8080/index.php)
-- |_ |_ See: http://blog.unmaskparasites.com/2009/09/11/dynamic-dns-and-botnet-of-zombie-web-servers/
-- 

author = "Ron Bowes"

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

categories = {"malware", "safe"}


portrule = shortport.http

action = function(host, port)
	-- Check what response we get for a 404
	local result, result_404, known_404 = http.identify_404(host, port)
	if(result == false) then
		return stdnse.format_output(false, "Couldn't identify 404 message: " .. result_404)
	end

	-- If the 404 result is a 302, we're going to have trouble
	if(result_404 == 302) then
		return stdnse.format_output(false, "Unknown pages return a 302 response; unable to check")
	end

	-- Identify servers that answer 200 to invalid HTTP requests and exit as these would invalidate the test
	if ( result_404 == 200 ) then
		stdnse.print_debug(1, "%s: Exiting due to ambiguous response from web server on %s:%s. All URIs return status 200.", SCRIPT_NAME, host.ip, port.number)
		return false
	end
  
	-- Perform a GET request on the file
	result = http.get_url("http://" .. host.ip .. ":" .. port.number .. "/ts/in.cgi?open2")
	if(not(result)) then
		return stdnse.format_output(false, "Couldn't perform GET request")
	end

	if(result.status == 302) then
		local response = {}
		if(result.header.location) then
			table.insert(response, string.format("Host appears to be infected (/ts/in.cgi?open2 redirects to %s)", result.header.location))
		else
			table.insert(response, "Host appears to be infected (/ts/in.cgi?open2 return a redirect")
		end
		table.insert(response, "See: http://blog.unmaskparasites.com/2009/09/11/dynamic-dns-and-botnet-of-zombie-web-servers/")
		return stdnse.format_output(true, response)
	end

	-- Not infected
	if(nmap.verbosity() > 0) then
		return "Host appears to be clean"
	else
		return nil
	end
end
