local bin = require "bin"
local rmi = require "rmi"
local shortport = require "shortport"
local stdnse = require "stdnse"
local string = require "string"
local vulns = require "vulns"

description = [[
Checks if rmiregistry allows class loading.

The default configuration of rmiregistry allows loading classes from remote
URLs which can lead to remote code execution. This is considered as "by
design".

Based on original Metasploit module by mihi.

References:
* http://dev.metasploit.com/redmine/projects/framework/repository/entry/modules/exploits/multi/misc/java_rmi_server.rb
]];

---
-- @usage
-- nmap nmap --script=rmi-vuln-classloader -p 1099 <target>
--
-- @output
-- PORT     STATE SERVICE
-- 1099/tcp open  rmiregistry
-- | rmi-vuln:
-- |   VULNERABLE:
-- |   RMI registry default configuration remote code execution vulnerability
-- |     State: VULNERABLE
-- |     Description:
-- |               Default configuration of RMI registry allows loading classes from remote URLs which can lead to remote code executeion.
-- |
-- |     References:
-- |_      http://dev.metasploit.com/redmine/projects/framework/repository/entry/modules/exploits/multi/misc/java_rmi_server.rb

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



portrule = shortport.port_or_service({
    1099
  }, {
    "rmiregistry"
  });

action = function (host, port)
  local registry = rmi.Registry:new(host.ip, port.number);
  registry:_handshake();
  local rmiArgs = rmi.Arguments:new();
  local argsRaw = "75" ..  --TC_ARRAY
   "72" ..  -- TC_CLASSDESC
   "0018" ..  -- string len
   "5B4C6A6176612E726D692E7365727665722E4F626A49443B" ..  -- class name "[Ljava.rmi.server.ObjID;"
   "871300B8D02C647E" ..  -- serial id
   "02" ..  -- FLAGS (serializable)
   "0000" ..  -- FIELD COUNT
   "70787000000000" ..  --TC_NULL TC_BLOCKEND TC_NULL
   "77080000000000000000" ..  -- TC_BLOCKDATA
   "73" ..  -- TC_OBJECT
   "72" ..  -- TC_CLASSDESC
   "0005" ..  -- string len
   "64756D6D79" ..  -- class name "dummy"
   "A16544BA26F9C2F4" ..  -- serial id
   "02" ..  -- FLAGS (serializable)
   "0000" ..  -- FIELD COUNT
   "74" ..  -- TC_STRING
   "0010" ..  -- string len
   "66696C653A2E2F64756D6D792E6A6172" ..  -- annotation "file:./dummy.jar"
   "78" ..  -- TC_ENDBLOCKDATA
   "70" ..  -- TC_NULL
   "7701000A"; -- TC_BLOCKDATA
  local rmi_vuln = {
    title = "RMI registry default configuration remote code execution vulnerability",

    description = [[
	Default configuration of RMI registry allows loading classes from remote URLs which can lead to remote code executeion.
		]],
    references = {
      'http://dev.metasploit.com/redmine/projects/framework/repository/entry/modules/exploits/multi/misc/java_rmi_server.rb',
    },
    exploit_results = {},
  };

  local report = vulns.Report:new(SCRIPT_NAME, host, port);
  rmi_vuln.state = vulns.STATE.NOT_VULN;

  rmiArgs:addRaw(bin.pack("H", argsRaw));

  -- reference: java/rmi/dgc/DGCImpl_Stub.java and java/rmi/dgc/DGCImpl_Skel.java
  -- we are calling DGC's (it's objectId is 2) method with opnum 0
  -- DCG's hashcode is f6b6898d8bf28643 hex or -669196253586618813 dec
  local status, j_array = registry.out:writeMethodCall(registry.out, 2, "f6b6898d8bf28643", 0, rmiArgs);
  local status, retByte = registry.out.dis:readByte();
  if not status then
    return false, "No return data received from server";
  end

  if 0x51 ~= retByte then
    -- 0x51 : Returndata
    return false, "No return data received from server";
  end
  data = registry.out.dis.bReader.readBuffer;

  if string.find(data, "RMI class loader disabled") == nil then
    rmi_vuln.state = vulns.STATE.VULN;
    return report:make_output(rmi_vuln);
  end

  return report:make_output(rmi_vuln);
end;