rsync-brute NSE Script

local brute = require "brute"
local creds = require "creds"
local shortport = require "shortport"
local stdnse = require "stdnse"

local rsync = stdnse.silent_require "rsync"

description = [[
Performs brute force password auditing against the rsync remote file syncing protocol.
]]

---
-- @usage
-- nmap -p 873 --script rsync-brute --script-args 'rsync-brute.module=www' <ip>
--
-- @output
-- PORT    STATE SERVICE REASON
-- 873/tcp open  rsync   syn-ack
-- | rsync-brute:
-- |   Accounts
-- |     user1:laptop - Valid credentials
-- |     user2:password - Valid credentials
-- |   Statistics
-- |_    Performed 1954 guesses in 20 seconds, average tps: 97
--
-- @args rsync-brute.module - the module against which brute forcing should be performed



author = "Patrik Karlsson"
license = "Same as Nmap--See https://nmap.org/book/man-legal.html"
categories = {"brute", "intrusive"}

portrule = shortport.port_or_service(873, "rsync", "tcp")

Driver = {

  new = function(self, host, port, options)
    local o = { host = host, port = port, options = options }
    setmetatable(o, self)
    self.__index = self
    return o
  end,

  connect = function(self)
    self.helper = rsync.Helper:new(self.host, self.port, self.options)
    return self.helper:connect(brute.new_socket())
  end,

  login = function(self, username, password)

    local status, data = self.helper:login(username, password)
    -- retry unless we have an authentication failed error
    if( not(status) and data ~= "Authentication failed" ) then
      local err = brute.Error:new( data )
      err:setRetry( true )
      return false, err
    elseif ( not(status) ) then
      return false, brute.Error:new( "Login failed" )
    else
      return true, creds.Account:new(username, password, creds.State.VALID)
    end
  end,

  disconnect = function( self )
    return self.helper:disconnect()
  end

}

local function isModuleValid(host, port, module)
  local helper = rsync.Helper:new(host, port, { module = module })
  if ( not(helper) ) then
    return false, "Failed to create helper"
  end
  local status, data = helper:connect()
  if ( not(status) ) then
    return false, "Failed to connect to server"
  end
  status, data = helper:login()
  if ( status and data == "No authentication was required" ) then
    return false, data
  elseif ( not(status) and data == "Authentication required" ) then
    return true
  elseif ( not(status) and data == ("Unknown module '%s'"):format(module) ) then
    return false, data
  end
  return false, ("Brute pre-check failed for unknown reason: (%s)"):format(data)
end

local function fail (err) return stdnse.format_output(false, err) end

action = function(host, port)

  local mod = stdnse.get_script_args(SCRIPT_NAME .. ".module")
  if ( not(mod) ) then
    return fail("rsync-brute.module was not supplied")
  end

  local status, err = isModuleValid(host, port, mod)
  if ( not(status) ) then
    return fail(err)
  end

  local engine = brute.Engine:new(Driver, host, port, { module = mod })
  engine.options.script_name = SCRIPT_NAME
  local result
  status, result = engine:start()
  return result
end