SOCKS4 Experiments Failed attempts at restricting a Socks 4/4a/5 proxy to only use Socks 4

socks4.py

#!/usr/bin/env python

import socket
import threading
import select
import SocketServer

class TCPServer( SocketServer.TCPServer ):
	allow_reuse_address = True

class ThreadedTCPServer( SocketServer.ThreadingMixIn, TCPServer ):
	pass

def relay( A, B ):
	AtoB = threading.Thread( target = passthru, args = ( A, B ) )
	BtoA = threading.Thread( target = passthru, args = ( B, A ) )
	AtoB.start()
	BtoA.start()
	AtoB.join()
	BtoA.join()

def passthru( A, B ):
	while True:
		r, w, x = select.select( [ A ], [ B ], [] )
		if not r or not w:
			continue

		data = A.recv( 4096 )
		hex = "PROXY:"
		for i in data:
			hex += " %02x" % ord( i )
		print hex
		print data

		if not data:
			break

		B.sendall( data )
		print str( A.getsockname() ) + ' -> ' + str( B.getsockname() ) + ( ' : %d' % len( data ) )

class Socks4Handler( SocketServer.BaseRequestHandler ):
	def handle( self ):
		data = self.request.recv(1024)
		hex = "CLIENT:"
		for i in data:
			hex += " %02x" % ord( i )
		print hex

		if "\x04" != data[0]:
			print "CLIENT NOT SOCKS4"
			self.request.sendall( "\x00\x5B\x00\x00\x00\x00\x00\x00" )
			self.request.close()
			return

		if "\x00" == data[4]:
			print "CLIENT ATTEMPTED SOCKS4A"
			self.request.sendall( "\x00\x5B\x00\x00\x00\x00\x00\x00" )
			self.request.close()
			return

		self.ssh = socket.socket( socket.AF_INET, socket.SOCK_STREAM )
		self.ssh.connect( ( '127.0.0.1', 8080 ) )

		self.ssh.sendall( data )

		recvd = self.ssh.recv( 1024 )
		hex = "SERVER:"
		for i in recvd:
			hex += " %x" % ord( i )
		print hex

		if "\x00" != recvd[0] or "\x5A" != recvd[1]:
			print "SERVER SENT ERROR"
			self.ssh.close()
			self.request.sendall( recvd )
			self.request.close()
			return

		self.request.sendall( recvd )

		relay( self.ssh, self.request )

	def finish( self ):
		return
		try:
			print "CLOSE SSH"
			self.ssh.close()
		except:
			pass
		try:
			print "CLOSE REQUEST"
			self.request.close()
		except:
			pass

if __name__ == "__main__":
	server = TCPServer( ( '127.0.0.1', 7070 ), Socks4Handler )
	server.serve_forever()

#	server = ThreadedTCPServer( ( '127.0.0.1', 7070 ), MyTCPHandler )
#	server_thread = threading.Thread(target=server.serve_forever)
#	server_thread.start()