local nmap = require "nmap"
local shortport = require "shortport"

description = [[
Checks if a VNC server is vulnerable to the RealVNC authentication bypass
(CVE-2006-2369).
]]
author = "Brandon Enright"
license = "Same as Nmap--See https://nmap.org/book/man-legal.html"

---
-- @output
-- PORT     STATE SERVICE VERSION
-- 5900/tcp open  vnc     VNC (protocol 3.8)
-- |_realvnc-auth-bypass: Vulnerable

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


portrule = shortport.port_or_service(5900, "vnc")

action = function(host, port)
  local socket = nmap.new_socket()
  local result
  local status = true

  socket:connect(host, port)

  status, result = socket:receive_lines(1)

  if (not status) then
    socket:close()
    return
  end

  socket:send("RFB 003.008\n")
  status, result = socket:receive_bytes(2)

  if (not status or result ~= "\001\002") then
    socket:close()
    return
  end

  socket:send("\001")
  status, result = socket:receive_bytes(4)

  if (not status or result ~= "\000\000\000\000") then
    socket:close()
    return
  end

  socket:close()

  return "Vulnerable"
end
