Redirector for localhost driven SMTP based on a simple TCP redirector in python

SMTPRedirector

#!/usr/bin/env python
# SMTP client ip tunneler
#
# ./SMTPRedirector 0.0.0.0 LISTENPORT SMTPHOST SMTPPORT
#
# Based on https://gist.githubusercontent.com/sivachandran/1969859/raw/f834e72c27488c279166a53ce1623b7f2f79e70c/SimpleTcpRedirector.py

import socket
import threading
import select
import sys
import os

terminateAll = False

class ClientThread(threading.Thread):
	def __init__(self, clientSocket, targetHost, targetPort, sourceHost):
		threading.Thread.__init__(self)
		self.__clientSocket = clientSocket
		self.__targetHost = targetHost
		self.__targetPort = targetPort
		self.__sourceHost = sourceHost

	def run(self):
		#print "ClientThread started"

		self.__clientSocket.setblocking(0)

		targetHostSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                targetHostSocket.bind((self.__sourceHost, 0))
		targetHostSocket.connect((self.__targetHost, self.__targetPort))
		targetHostSocket.setblocking(0)

		clientData = ""
		targetHostData = ""
		terminate = False
		while not terminate and not terminateAll:
			inputs = [self.__clientSocket, targetHostSocket]
			outputs = []

			if len(clientData) > 0:
				outputs.append(self.__clientSocket)

			if len(targetHostData) > 0:
				outputs.append(targetHostSocket)

			try:
				inputsReady, outputsReady, errorsReady = select.select(inputs, outputs, [], 1.0)
			except Exception, e:
				print e
				break

			for inp in inputsReady:
				if inp == self.__clientSocket:
					try:
						data = self.__clientSocket.recv(4096)
					except Exception, e:
						print e

					if data != None:
						if len(data) > 0:
							targetHostData += data
						else:
							terminate = True
				elif inp == targetHostSocket:
					try:
						data = targetHostSocket.recv(4096)
					except Exception, e:
						print e

					if data != None:
						if len(data) > 0:
							clientData += data
						else:
							terminate = True

			for out in outputsReady:
				if out == self.__clientSocket and len(clientData) > 0:
					bytesWritten = self.__clientSocket.send(clientData)
					if bytesWritten > 0:
						clientData = clientData[bytesWritten:]
				elif out == targetHostSocket and len(targetHostData) > 0:
					bytesWritten = targetHostSocket.send(targetHostData)
					if bytesWritten > 0:
						targetHostData = targetHostData[bytesWritten:]

		self.__clientSocket.close()
		targetHostSocket.close()
		#print "ClientThread terminating"
def usage(appname):
	print 'Usage:\n\t'+appname+' <host> <port> <remote host> <remote port>'
	print 'Example:\n\t'+appname+' 0.0.0.0 5025 localhost 25'
	sys.exit(0)

if __name__ == '__main__':
	appname = sys.argv[0]
	if len(sys.argv) < 5:
		usage(appname)
	if sys.argv[1] == '-p':
		pidfilename = sys.argv[2]
		sys.argv[1:] = sys.argv[3:]
		pidfile = open(pidfilename, 'w+')
		pidfile.write(str(os.getpid())+"\n")
		pidfile.close()
		pidfile = None
	if len(sys.argv) != 5:
		appname = sys.argv[0]
		print 'Usage:\n\t'+appname+' <host> <port> <remote host> <remote port>'
		print 'Example:\n\t'+appname+' 0.0.0.0 5025 localhost 25'
		sys.exit(0)

	localHost = sys.argv[1]
	localPort = int(sys.argv[2])
	targetHost = sys.argv[3]
	targetPort = int(sys.argv[4])

	serverSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	serverSocket.bind((localHost, localPort))
	serverSocket.listen(5)
	#print "Waiting for client..."
	while True:
		try:
			clientSocket, address = serverSocket.accept()
			sourceSocket = clientSocket.getsockname()
			sourceHost = sourceSocket[0]
			print sourceHost
			if sourceHost[0:4] != '127.':
				clientSocket.close()
				continue
		except KeyboardInterrupt:
			#print "\nTerminating..."
			terminateAll = True
			break
		ClientThread(clientSocket, targetHost, targetPort, sourceHost).start()

	serverSocket.close()
	try:
		os.remove(pidfilename)
	except OSError:
		pass